.,







A MANUAL
OF
CH EM  IST RY,
ON THE BASIS OF
TURNER'S ELEMENTS OF CHEMISTRY;
CONTAINING, IN A CONDENSED FORM,
ALL THE MOST IMPORTANT FACTS AND PRINCIPLES
OF THE SCIENCE.
DESIGNED AS A TEXT-BOOK
FOR COLLEGES AND OTHER SEMINARIES OF LEARNING.
REWRITTEN AND RESTEREOTYPED, WITH MANY NEW ILLUSTRATIONS,
BY JOHNI J'ONSTON, LL. D.,
PROFESSOR OF NATURAL SCIENCE IN THE WESLEYAN UNIVERSITY,
PHILADELPHIA:
CI-IARLES DESILVER,
No. 714 CHESTNUT STREET,
OPPOSITE THE MIASONIC HALL.
1860.




Entered, according to Act of Congress, in the year 1856, by
CHAI-I A LES DESILVER,
in the Clerk's Office of the District Court of the United States for the Eastern District
of Pennsylvania.
STEREOTYPED BY J. FAGAN.




TO
PARKER CLEAVELAND, LL.D.,
PROFESSOR OF CHEMISTRY, MINERALOGY, AND NATURAL PHILOSOPHY3
IN BOWDOIN COLLEGE, BRUNSWICK, ME.;
DISTINGUISHED NO LESS FOR HIS PERSONAL VIRTUES
THAN
AS THE AUTHOR
OF THE FIRST AMERICAN WORK ON MINERALOGY AND GEOLOGY;
~Ehe folIoh)lfg 3ages are 3eapeuctfutllt) Knscfvbet,
II TOKEN OF THE DEEP SENSE OF OBLIGATION ENTERTAINED
BY HIS FRIEND AND FORMER PUPIL9
JOtIN JOHNSTON.
(m)








PREFACE
TO TBH  PRESENT, OR SIXTH  REVISED  EDITION.
BY the original contract between the publishers and
compiler of this work, provision was made for a periodical
revision, in order that new and important discoveries might
be introduced without delay, and the work be made to
conform as much as possible to the rapidly advancing
science.  These revisions have been carefully attended
to, and considerable alterations in the plates from time
to time have been required; the whole of the part on
Organic Chemistry, in the last preceding revision, having
been rewritten and restereotyped.
But the progress of the science is, and has been, still
onward; —new and important facts have rapidly been
made known, and new views, throwing more or less light
on points heretofore considered obscure and doubtful, have
been proposed; so that in the present revision an entire
recast of the work has been found necessary.  Encouraged
by the favor heretofore shown the work, the publisher has
cheerfully incurred the expense of stereotyping it anew,
including the preparation of many new illustrations; and
the results of our joint labors are here presented to the
public in a book substantially new, though retaining the
former title.
The changes which have been made are too great and
important to be discussed here; — for a knowledge of them
I,.s k(v)




Vi                   PREFACE.
the intelligent reader is referred to the pages of the work
itself; they are such only as the new aspects of the science
seemed imperatively to' demand.  The principles which
have been followed in its preparation are indicated in the
extracts from the advertisements to former editions, which
will be found further on.  Many of the new cuts have
been derived from the profusely illustrated work of Regnault; others are original, or have been obtained from
miscellaneous sources.
The Grouping of the Elements adopted is nearly the
same as that of Gmelin; —it is not free from objection,
but is considered the best yet proposed on this difficult
point. In preparing the remarks introductory to the part
on Organic Chemistry, important aid has been derived
from  Dr. W. Gibbs'  "Report on the Recent Progress
of Organic Chemistry," prepared for the American Association for the Advancement of Science, and printed in
the Proceedings of their ninth Meeting, at Providence,
R. I., August, 1855.
Many thanks are due to teachers and other kind friends,
for judicious suggestions and encouraging words during
the preparation of the work; and it is now offered to the
public in the confident expectation that it will be found
not less adapted for use in the school or lecture-room than
preceding editions.
MIDDLETOWN, CT., July, 1856.




EXTRACT FROM THE ADVERTISEMENT TO THE FIRST EDITION, (1840.)
TIHE preparation of the following pages was undertaken by the advice of the
late lamented President of the Wesleyan University, with the primary design
of providing a suitable Text-book on Chemistry, for the use of the annual
classes in that institution.
There are indeed already before the public many excellent works on this
branch of science, the great merits of which the subscriber is happy to acknowledge; but he long since became convinced, from his experience in teaching,
of the need of a work of a little different character, for the special use of students
in our higher seminaries of learning, as a text-book. The object of a great
majority of students, even of those who pursue a collegiate course, is, not tt
make themselves familiar with minute details of facts or processes of manipulation, but to understand the great principles of the science, and the leading
facts which serve for its foundation.  To facilitate the accomplishment of
this purpose is the object of the present work. In preparing it, the excellent " Elements of Chemistry" of the late Dr. Turner has been adopted as the
basis, and all of that work incorporated in it which was suited to our purpose.
1ils arrangement has been uniformly followed, with a few unimportant exceptions, which it is not necessary here to particularize. This arrangement, on
the whole, is considered the best that has ever been proposed.
The part of Dr. Turner's work omitted is taken up chiefly with details of facts
and discussions of opinions and theories, which indeed is important in a work
designed for the general student, but which would be out of place in a book
prepared expressly to be used as a text-book. Its place, however, has been
in part supplied by matter compiled from various other sources, so that the
work is thought to be sufficiently large for the ordinary use of students, as the
study of this science is usually pursued in this country. It has constantly been
an object, while the work should be true to the science, and present in true
proportion all its important features, to make it at the same time as practical
as possible; to lead the student to apply the principles he learns to the solution of natural phenomena, or processes he may witness in the arts.
EXTRACT FROM THE ADVERTISEMENT TO THE SECOND EDITION,
IN the present edition the work has been carefully revised, and indeed recompiled from the seventh edition of Turner's, and many additions made to
adapt it to the advancing state of the science.-'      *      * 
The extracts from other authors are always introduced in their own language, except in cases where it was necessary to make some little change to
incorporate the extract the better with the passage with which it comes in
connection. In a few instances the names of authors are introduced in the
text. To avoid the necessity of constantly introducing quotation marks and
references, a list of the authors which have been used will be given.
To facilitate the acquisition of the science, the text is divided into paragraphs,
and numbered; and references to important facts and principles introduced as
frequently as they seemed necessary. As in many institutions so much time
cannot be devoted to this science as would be requisite for a thorough study
of the whole work, the less important parts have been printed in smaller type,
which may be omitted on the first reading. The intelligent student, however,
it is hoped, will not be satisfied without a perusal, at his hours of leisure,
of the whole work.                                            (vii)




LIST OF WORKS
MADE USE OF, MORE OR LESS, IN THE PREPARATION OF THIIS WORK.
Elements of Chemistry, by the late Edward Turner, M.D., F.R.S., &c., edited L
J. Liebig, M. D., Ph. D. F. R. S., &c., and Wm. Gregory, M.D., F. R. S. E.
Elements of Chemistry, &c., by Robert Kane, M. D., M. R. I. A., &c. Dublin.
Chemistry of Organic Bodies, by Thomson.
Do.     Inorganic Bodies. Two vols.
Ure's Dictionary of Chemistry. Two vols.
Encyclopedia Metropolitana. Articles, Electro-magnetism, Electricity, Galvanism, Heat,
Light, and Chemistry.
Library of Useful Knowledge. Articles, Electricity, Galvanism, Magnetism, Electromagnetism, Chemistry, &c.
Thomson's Outlines of the Sciences of IIeat and Electricity.'rait6 de Chimie Appliqude aux Arts, par M. Dumas. Six tomes.
Trait6 de Chimie, par J. J. Berzelius; traduit par Me. Esslinger. Huit tomes.
Abr6g6 E16mentaire de Chimie, par J. L. Lassaigne. Deux tomes.
Organic Chemistry in its applications to Agriculture and Physiology, by Liebig, edited
by Webster.
Animal Chemistry, or Organic Chemistry in its applications to Physiology and Pathology,
by Liebig.
Lectures on Agricultural Chemistry and Geology, by J. F. W. Johnston.
Elements of         do.                 do.
Thomson's "First Principles."  Two vols.
Prof. Silliman's Chemistry. Two vols.
Prof. Hare's Compendium of Chemistry.
Faraday's Chemical Manipulation, edited by Dr. J. K. Mitchell.
Thomson's History of Chemistry. Two vols.
A Treatise on Chemistry by Michael Donovan, Esq.; Lardner's Cabinet Cyclopedia.
Prof. John W. Webster's Manual of Chemistry, on the basis of Prof. Brande's.
United States' Dispensatory, by Drs. Wood and Bache.
American Journal of Science and the Arts, conducted by Prof. Silliman.
Henry's Elements of Chemistry. Three vols.
Cleaveland's Mineralogy and Geology.
Dana's Mineralogy.
Shepherd's Mineralogy. Three vols.
Griffin's Chemical Recreations.
Journal of the Franklin Institute.
Parke's Chemical Catechism.
Chaptal's Chemistry applied to Agriculture.
Elements of Chemistry, by MI. Lavoisier, translated from the French by It. Kerr, F. R. S.
Watson's Chemical Essays. Five vols.
Noad's Chemical Manipulation and Analysis.
Do. Lectures on Electricity.
Knapp's Chemical Technology. Vols. I., II.
Gibbs' Report on the Recent Progress of Organic Chemistry.
Gmelin's (L.) Hand-book of Chemistry, translated by Henry Watts. Vols. I. to IX.
Trait6 de Chimle El6mentaire, Theorique et Pratique, par L. J. Thenard. Cinq tomes,
Cours de Chimie E16mentaire, par A. Bouchardat. Deux tomes.
Legons sur la Philosophie Chimie, profess6es an Coll6ge de France. par M. Dumas.
Th6orie des Proportions Chimiques, et Table Synoptique des Poids Antomiques, etc.,
par J. J. Berzelius.
Trait6 de Mineralogie, par M. L'Abb6 Haiiy. Quatre tomes.
El6ments de Physique, etc., par M. Pouillet.   do.
Lehrbuch der Chimie, von E. Mitscherlich, Berlin, 1844.
Grundriss der Chimie, von Professor Dr. F. F. Runge.
Cours de Chimie Generale, par J. Pelouze et E. Fremy. Trois tomes, accompagne d'un
Atlas de 46 Planches.
Gerhardt (Ch.), Trait6 Chimie Organique.
Rlegnault, Cours Elementaire de Chinsie.
The same, translated into English by Dr. T. F. Betton, M. D.
Besides the above, reference has often been made to various other works, as Le Diction.
naire des Sciences Naturelles, Annales de Chimie et de Physique, the various Encyclopedias,
Philosophical Transactions, &c.
(viii)




CONTENTS.
PART I
THE IMPONDERABLE AGENTS.
PAGE
INTRODUCI ION..........................................................                13
I. HEAT.
Nature and  Sources of Heat..............1..........7.........................    1
Expansion of Bodies by Heat..........................,,........   18
Thermometers.................................................................  22
Distribution  of Heat..........................................................   29
Relation of Heat to Changes in the State of Bodies.......................   36
Specific Heat.-Capacity  of Bodies for Heat..............................   58
II. LIGHT.
Nature and Sources of Light......................                                                 60
Distribution of Light..............................................................   65
Decomposition of Light..................8.........................................                 8
III. ELECTRICITY.
Nature of Electricity.-Electrical Theories.....................   74
Distribution of Electricity...........................................,....   76
Sources of Electricity..................51............................................   81
Galvanism...........................................................................          88
Effects of Galvanic Electricity................................................... 102
Electro-magnetism............................................................    111
PART II.
GENERAL CIIEMISTRY.
The Elements.-Chemical Affinity............................................. 137
Laws of Combination.-Atomic Theory..................................... 143
Nomenclature of Chemistry.-Symbols....................................... 151
Crystalography...................................................................... 158
(ix)




CONTENTS,
PART II1.
SPECIAL C IIEMISTRY- INORGANIC.
PAGX
CLASSIFICATION  OF ELEMENTS...................................................  172
METALLOIDS, OR NON-DIETALLIC ELEMENTS................................. 173
GROUP  I. -   Oxygen............................................................... 174
Hydrogen............................................................  181
Nitrogen........................................................  191
GROUP II. -   Chlorine..............................................................  206
Iodine..............................................................                                             215
Bromine..........................................................                                                 2i3
Fluorine.............................................................  220
G(ROUP         III.- Sulphur..............................................................  222
Selenium............................................................  23(9
Tellurium............................................................  240
GrROUP IV. —Phosphorus....................................................... 241
Arsenic............................................................  250
GaouP V. -    Carbon..............................................2........... 257
Silicon......................................................    278
Boron..............................................................  281
THE  METALS......................................................................... 284
GENERAL PROPERTIES......................................................    2841
GROUP  I. -Potassium.................................................. 298
Sodium........................................................  310
Lithium................................................... 318
Ammonium........................................  319
GROUP II. -Barium................................................  328
Strontium.........................................................  330
Calcium................................................       331
M agnesium................................................   337
GROUP  III.-Aluminum..................................... 339
Glucinum.....................................................                          344
Zirconium...................................................344
Thorium...........................................................    344
Yttrium...........................................  344
Erbium..............................................................  344
Terbium..............................................  344
Cerium..................................  344
Lanthanum................................... 344
Dic lymium..........................................................   344




CONTENTS.                                                           xi
PAGE
Ganoup IV. —Mianganese....................... 345
Iron 348
Iron....................................................................  348
Chromium........................................................... 357
Zinc................................................................... 859
Cadmium.........................................................3....    362
Tin..                                                          #            #   e........................................ 362
Cobalt................................................................ 364
Nickel........................................................             365
GaouP V. — Antimony............................................................  65
Bismuth.............................................................. 367
Lead.................................................................. 368
Copper......................................... I.................... 371
Vanadium................................................ 373
Molybdenum........................................................  373
Tungsten.............................................. 373
Titanium.............................................................                     373
Uranium................                                                                   374
Columbium..............................................  374
Tantalum............................................................   374
RnouP         VI.-Mercury..................,........................                  374
Silver.........8....................          381
Gold................................................................... 386
Platinum......................................................... 389
Osmium..............................................................  391
Iridium..3....................................... 392
Palladium..........................                                                      392
Rhodium.............................................................   92
Ruthenium.......................................................... 392
PART IV.
SPECIAL CHEMISTRY-ORGANIC.
GENERAL  PROPERTIES  OF  ORGANIC  BODIES...................................   93
STARCH,  SUGAR, GuMB, LIGNINE................................................. 405
Starch, or Fecula.............................................................  405
Sugars...........................................................................  408
Gums..4............................................................ 411
Woody  Fibre, Lignine, Cellulose.......................................... 412
A LCOROLS AND SUBSTANCES DERIVED FROMi THEiM......................... 418
Wine Alcohol...................................... 418
Methylic  Alcohol, or Wood  Spirit........................................ 428
Amylic  Alcohol.................................................  430
Sulphur Alcohols, or  Mercaptans......................................... 432




XiP                                  C OCONTENTS.
PAOG
ETIIERS.-COUPLED, OR VINIC  ACIDS..........................  433
Ethers of Wine Alcohol....................................  434
I. Simple Ethers........................................................   434
II. Compound Ethers....................... 438
Ethers of Methylic Alcohol..................................     440
I. Simple Ethers...................................................  440
II. Compound Ethers...........................                                     442
Ethers of Amylic Alcohol................................................... 443
VOLATILE, OR ESSENTIAL  OILS............................................    444
Carbohydrogen Volatile Oils............................................... 446
Oxygenated Volatile Oils................................................... 448
Sulphuretted Volatile Oils.................................................. 452
Camphors....................................................................... 453
Coumarine...................................................................... 454
FIXED OILS AND  FATS............................................................. 455
Glycerine....................................................................... 456
Stearine and Stearic Acid....................................... 457
Margarine and Margaric Acid............................................. 458
Oleine and Oleic Acid........................................................ 458
Other Proximate Principles of the Fats................................. 459
Soaps and Plasters............................................................ 462
RESINOUS SUBSTANCES............................................................. 46
VEGETABLE ACIDS NOT INCLUDED IN PRECEDING GROUPS................ 465
ORGANIC ALKALIES, OR  ALKALOIDS.............................. 469
ALKALOIDS OF THE ETHERS, OR CONJUGATED AMMONIAS.................. 471
ORGANIC  COLORING-MATTERS.................................................... 475
TuIE AMIDES AND NITRILES..................... 478
CYANOGEN AND ITS COMPOUNDS............................................  480
Compounds of Cyanogen and Oxygen.................................. 481
Compounds of Cyanogen and Hydrogen................................                       484
Sulphocyanates or Sulphocyanides....................................... 485
Compounds of Cyanogen and the Metals............................... 486
Double  Cyanides.-Polycyanides.........................................  487
ALBUMIINOUS, OR. PROTEINE COMPOUNDS.................................,                         490
CIIEMIICAL  PHENOMENA OF VEGETATION....................................... 494
COMPOSITION   OF THE ANIMAL  TISSUES......................................... 498
THE BLOOD. -PHENOMENA OF RESPIRATION AND DIGESTION............. 500
The Blood....................................................................... 501
Phenomena of Digestion..................................................... 503
Phenomena of Respiration...................                                              506
SEVERAL ANIMAL SECRETIONS AND EXCRETIONS NOT BEFORE NOTlCdED 510
Ar1ENDIx.-TA3LES OF WVEIGHITS AND AIEASURES........................ 515




MANUAL OF CHEM [ISTRY.
PART I.
THE IMPONDERABLE AGENTS.
INTRODUCTION.
1. WE recognize as matter or substance whatever possesses tle
four properties of extension, impenetrability, inertia, and gravity,
or weight. By the first of these properties every body occupies a
portion of space; by the second, it refuses to allow another body
to occupy this space at the same time with itself; by the third, it
is incapable, of itself, of changing its state, whether of rest or
motion; and by the fourth, if unsupported, it falls to the earth.
Whatever does not possess all these properties is not recognized as
matter.
2. Natural science embraces the whole range of material things:
their properties, the changes they are capable of undergoing, and
the laws of their changes.
3. As has been suggested by Gmelin, all the changes of which
any portion of matter is capable may be referred to the three
eauses or forces of Repulsion, Attraction, and Vitality.
4. Repulsion is manifest in the property of matter denominated
impenetrability, and in the expansion of bodies, especially by the
influence of heat, as will be shown hereafter.
QUESTIONS. -1. What is matter or substance?  Define what is meant
by the four properties mentioned. —2. What does Natural Science embrace?-8. To what three causes may all changes of matter be referre/1?
-4. In what is repulsion manifest?;2                                          (13)




14                    INTRODUCTION.
5. Attraction manifests itself in a variety of forms:  1. As
Gravitfation, or that force which acts at all distances, however
great, and between the largest masses.  2. Coh7esion, or that force
which, acting only at distances immeasurably small, unites the
parts of the same mass.  3. Electrical and MJagnetic Attracfion.
4. CUemical Attraction or Affnity, which acts only at insensible
distances, and between the ultimate particles of bodies, and produces homogeneous compounds.
6. Vitality is that peculiar force or power, possessed both by
animals and plants, by which the simple affinities of the various
substances contained in their bodies are so modified and controlled
in their action, as to produce the complex, and almost innumerable
organic compounds, such as sugar, woody-fibre, albumen, &c.
Changes produced by all the varieties of attraction above mentioned,
except the fourth, or last, pertain properly to Physics or Natural Philosophy; while those produced by Affinity, either alone, or as it is controlled
by vitality in the bodies of plants and animals, belong to Chemistry.
The changes produced by the action of affinity consist in the combination of dissimilar substances into a homogeneous mass, or, occasionally,
the separation of dissimilar substances from a homogeneous mass. We
may, therefore, define Chemistry as the science which treats of the combination of dissimilar substances into homogeneous compounds, and of
the separation of dissimilar bodies from homogeneous compounds.
7. Molecules or Atoms.-All bodies, it is believed, are male
up of infinite numbers of indefinitely small particles —too small to
be detected by the eye, even when aided by the most powerful
microscopes -which are called molecules or atoms (from a, privative, and temno, I cut), indicating their supposed indivisibility.
Our knowledge of them is obtained indirectly, as we shall see
hereafter; but it is believed that all the molecules of the same
substance are precisely alike in weight, size, and form, as well as
other properties.
8. Simple and Compound Bodies. —From  what has been said
above, the distinction between simple and compound bodies is
obvious.  Simple substances are such as are believed to be conmQurSTIONS.-5. What are the different varieties of attraction?  Defi:e
the several varieties. -6. What is vitality?  What changes pertain i,
Natural PhilosopZvy or Physics?  What to Chemistry?  The changes p''i-I
duced by the action of affinity consist in what?-7. Of what are:li
bodies composed?  Do we have any direct knowledge of thlese atoIms? —
8. What are simple bodies?




INTRODUCTION.                              15
I)poed of only one kind of particles, as carbon, sulphur, copper,
a-d gold; compound substances are composed of two or more kinds
of particles, which are held in union more or less intimate by
their affinity.  The separation of the elements of a compound is
called its decomposition.
The composition of a body may be determined in two ways, analytically or synthetically.  By analysis, tire elements of a compound are
separated from one another, as when water is resolved by the agency
of galvanism into oxygen and hydrogen; by synthesis they are made to
combine, as when oxygen and hydrogen unite by the electric spark, and
generate a portion of water.  Each of these kinds of proof is satisflactory; but when they are conjoined-when we first resolve a particle
of water into its elements, and then reproduce it by causing them to
unite-the evidence is in the highest degree conclusive.
9. Matter is Indestructible; that is, it cannot be made to
cease to exist.  This statement seems at first view contrary to fact.
Water and other volatile substances are dissipated by heat; and
coals and wood are consumed in the fire, and disappear.  But in
these and other similar phenomena, not a particle of matter is
annihilated: the apparent destruction is owing merely to a change
of form or of composition.  The power of the chemist is, therefore,
limited to the production of these changes.
10. Different Forms of Matter. —latter exists in three forms
or states: the solid, liquid, and gaseous.  Besides these, there are
the three imponderable  agents, Heat, Light, and  Electricity,
which, if they are ever proved to be material, will constitute a
fourth form of matter.
It is believed flhat the particles of a substance, even the most solid,
are never in actual contact, but are held in close proximity by the two
opposite forces of attraction and repulsion; and that the particular state,
whether solid, liquid, or gaseous, in which a body is seen, depends upon
the relative intensity, for the time, of these forces.
If the force of attraction altogether preponderates in a body, it
is solids and the particles, in general, are held firmly in their
QuEsTIONS. -What are compound bodies?  Give an illustration.  In
what two modes may the composition of a body be determined? Explain analysis and synthesis. - 9. Can matter be destroyed?  To what
is the power of the chemist limited?-10. What different forms of matter
are there?  What is said of the imponderable agents?  Are the particles of matter ever in contact?  Upon what will the state of matter in
any particular case depend?  Are not the particles of solids in contact 
What reasons are given for this opinion?




16                   IN TRODUCTI(  N.
places, and are incapable of motion among themselves.  But the
particles are not in actual contact, for, by cooling, or by great
pressure, the dimensions of any body may be contracted, and,
therefore, its particles brought nearer to each other.  This will
appear more fully hereafter.
In liquids, there is a degree of cohesion among the particles
which, however, are capable of perfectly free motion among themn
selves.  That there is a degree of cohesion existing between the
particles is shown by the drop, which is composed of particles held
together by a slight force; but this slight force does not interfere
with the freedom of their movements.
Gases are distinguished by their tendency to expand, or enlarge
their volume, when external pressure is removed.  In them cohesion is entirely wanting.   The term  fluid  is applied  to  both
liquids and gases.
Some substances are found naturally existing in one of these states,
and some in another; and many can be made to pass from one state or
form to another, simply by varying their temperature, or the pressure
to which they are exposed. Thus, water at a moderate temperature is
liquid, but in the cold weather of winter it freezes, that is, becomes
solid; and if it be heated sufficiently, it is changed into steam, or
becomes gaseous.  The metal, platinum, is found always in the solid
state, though it may be melted by very great heat; but carbon is known
only as a solid. Several substances, found naturally in the gaseous state,
may be changed to liquids by great pressure, or by extreme cold; and,
by a still greater cold, some of them may be frozen. Others, as atmospheric air, have hitherto resisted all attempts to reduce them to the
liquid or solid form.
Hleat, light, and electricity are said to be imponderable, because they
possess no appreciable weight; but they certainly exhibit some of the
ordinary properties of matter.  They may be accumulated in bodies, are
capable of being attracted and repelled, and often produce various chemical and mechanical effects. But because they possess no weight, so
far as we can determine, many choose to consider them, not as matter,
but only properties of matter.
QUESTIONS.-IS there any cohesion among the particles of liquids?
How is this shown?  How are gases distinguished?  How is the word
fluid used? What is said of the natural state of substances?  ~What are
the imponderables? Why are they so called?




I. H EAT.
NATURE AND SOURCES OF IIEAT.
11. The word Heat is used indiscriminately to indicate the sensation we experience by placing the hand in contact with a heated
body, or the cause of the sensation.  To indicate the latter, the
word caloric has sometimes been used.
The discussion of this subject properly pertains to Physics, or Natural
Philosophy, (6,) but the agency of heat is so intimately connected with
nearly all chemical changes, that a treatise upon Chemistry would be imIpeifect without a previous development of some of its more important
laws and phenomena.
12. Nature of Heat. -  Heat cannot be obtained separate from
matter; it is invisible, and, so far as we are able to determine,
entirely destitute of weight.  It is not, therefore, (10,) believed
to be material; but in describing its effects, and its relations to
matter in general, we speak of it as an exceedingly subtile fluid,
the particles of which constantly repel each other, but are attracted
by other substances -as capable of being transmitted through
space, and the interior of bodies, and of being accumulated in
quantities in them.  It is present in all bodies, and cannot be
wholly separated from  them.  For if a substance, however cold,
be transferred into an atmosphere which is still colder, a thermo.
meter placed in the body will indicate the escape of heat.
HIeat appears to be attracted by all bodies, but is self-repellent, as is
shown by the fact that two bodies easily movable, when heated in a
vacuum, repel each other.
13. Sources of Heat.-The chief sources of heat are: the Sun,
Cormbustion, and other chemical changes, Friction, Electricity, and'Vital Action.
The Sun is the great source of heat to our system.  The intensity of the solar heat appears to be directly in proportion to the
number of rays that can be collected upon a given surfac; and
at one time philosophers were able to produce a greater heat by
QusTroNs. —  11. HI-ow is the word Ileat used?  Caloric?  Is the
naemilcy of heat connected with chemical changes?-12. Can heat be
bltained separate from matter?  Do we speak of heat as being material?
Is beat present in all bodies?  Is it attracted by matter?  13. What
sau,rcrs of' heat are mentioned?  HIow may the sun's rays be concentrated
s;! as to p1roduce a great heat?
*  17)




13        N iNATURE AND  SO URCES OF ISEA'.
cllecting the sun's rays by means of the convex lens or concav
mirror, than by any other mode.
But although the sun's rays are not made use of in the arts when
great heat is required, yet their momentous importance to all the inhabitants of the earth cannot he over-estimated. Without them all the water
upon the face of the globe would soon be congealed, and animal and vege
table life cease to exist.
Comblstion is the great source of artificial heat, as the sun iL
the source of natural heat.  Besides wood, nature has provided
immense deposits of combustible material, in the form of mineral
coal, in the bosom of the earth.  These are found in almost every
country, and seem to be provided by the Creator as an unfailing
resource for man, when, from the increase of the species, or from
his own negligence or extravagance, the supply from the vegetable
world should fail or become deficient.
F'icotiont is a well-known source of heat.  By the friction of the
parts of heavy machinery, especially when not well oiled, heat has
often been evolved sufficient to ignite wood; and the same effect is
said to have been produced in ships by the rapid descent of the
cable. Some tribes of the aborigines of this country were accustomed to kindle their fires by rubbing smartly one piece of wood
against another.  In the boring of cannon, heat enough has been
evolved to raise the temperature of a considerable quantity of water
so hs to boil.
The heating effects of electricity will be considered hereafter.
The influence of vital action in developing heat is seen in all
warm-blooded animals, which are maintained at a temperature
often much above that of the air and other surrounding bodies,
though heat must constantly be escaping from  them.
EXPANSION  OF BODIES BY IIEAT. -TIERMOMIETERS.
14. All bodies, with a very few exceptions, expand when their
temperature is increased, and contract when it is reduced.  I-low
this effect is produced we really, do not know, but appearances indicate that the particles of heat entering among the particles of the
body, partially overcome their cohesion, and cause them to sepaQUETIONS. —What is the great source of artificial heat?  What is said
of friction as a source of heat? - 14. Are all bodies expanded by heat?
}How are bodies affected by a reduction of their temperature?




NATURE  AND  SOURCES OF IIEAT.                        19
rate farther from  each other.   On the other hand,  when the
particles of heat are withdrawn, the molecules of the body are
allowed to approximate each other more closely.  A substance is
therefore less dense when heated, than when cold.
15. Expansion of Solids. —The expansion of solids by heat is
not very considerable, but may easily be made
very sensible. Let a bar of brass be accurately
fitted into a gauge, when cold, and then let
it be slightly heated; it will be found to have
increased so much in length as not to fit the
gauge0. If the gauge be also made of brass,
and the experiment performed in the warm
weather of summer, the same result will be
produced by cooling the gauge in ice-water,
because of its contraction by the cold.  This  Expansion of Solids.
experiment indicates a change only in length, but a corresponding
change is at the same time produced, both in breadth and thickness, as may be demonstrated in various modes, which the ingenious
student will readily devise.
16. Different Solids, when equally heated, do not expand
equally; every substance possesses an expansibility peculiar to
itself. Blut a body expanded by heat, and again cooled to the
same temperature it had at first, suffers no change in its dimensions.
Nor does the same substance expand equally at all temperatures with
an equal increase of heat; in general, the expansibility increases with
the temperature.  Thus, a body heated ten degrees at a high temperati're, expands more than when the same amount of heat is added at a
low temperature.
The different expansibility of the two metals, copper and platinum, may be shown by soldering together a thin slip of each, and
applying a moderate heat to the
comlpound bar.  Both plates will
be equally heated, but the copper being the most expansible,
the bar will be curved, the cop-    Different Expansion of two Metals.
Qu:STIoNs.-15. How may the expansion of a solid by heat be shown
1(;. Do all bodies expand equally when equally heated?  Does the salle
sutbstance at different temperatures expand equally for equal increases
of tenmperattc?  Ilow may the different expansibilities of two metals,
as copper and platinum, be shown?




20         NATUR E  AND  SOURICES OF  H EA T.
per being  on the convex side.  See figure, in which the copper is
supposed to be on the lower, and the platinum  on the upper side.
()ther metals, used in pairs in a similar manner, would show the
stanie result, but with  many of them  the effect would be less
dlecidd.
An  instrument like the following, at the same time that it
shiows the different expansibilities of two metals, serves as an
excellent thermometer for many practical purposes.  A and B are pieces of iron wire -  Iths,s n 7"    <       of an inch in diameter, and a foot long; and
C a piece of brass wire of the same size and
i:;5;~~   ~~~x,:)} length.  At the bottom  they are all fastened
together by brazing or otherwise; at the top, a
piece of brass is fixed to the two pieces of iron,
and through it, near the centre, is a hole in
~A   x B    which the brass wire, C, plays freely.  Now,
by immersing the thin wires in boiling water,
hot oil, or melted lead, they are all expanded;
but the brass expanding more than the iron,
its upper end is pushed  upward  against the
lever, D, which in turn acts upon E, producing
considerable motion at its extremity, where may
be placed a graduated scale, as S.  Such an
Different Expansion  instrument will be sensibly effected  by even
of Metals.    moderate changes of temperat ure.
The following table shows the expansion in length of rods of
several substances, when  transferred  from  the freezing  to the
boiling point of water:
Substances.        Expansion in Frac- Substances.       Expansion in Frao.
tion of TLength.                    tionr of Length.
Flint Glass...........,.         Copper..............
rood...............            Brass.............
Wood...............                          - -93;6 -0
Platinum............        %;j-'  Zinc................-3    -
Gold..............                 Tin...............
Sil-el...............              Bismut.............    f
ITrI.............  Lead................   
Steel'        Antimony..        3
S'  eel................           Antimony.........          _
QuEsTIoxs.-Describe the instrument represented by the second figure
of this para:graph.  What is the design of the instrument?  What are
some of the most expansible of the metals, as indicated in the table?




NATURE  AND  SOURCES  OF  HEAT.                       21
17. Practical Applications. — This property of bodies, and
particularly of the metals, has been applied to various useful
purposes in the arts.  The iron band or tire of a carriage-wheel
is made a little smaller than the circumference of the wheel, but,
being expanded, is sufficiently enlarged to be slipped on; and the
immediate application of water prevents it from burning the wood,
and brings the iron to its original dimensions, causing it to grasp
the wheel with great firmness.  Other examples are of frequent
occurrence in the arts.
The expansions and contractions of bodies by change of temperature
also occasion some inconveniences.  The accurate movement of clocks
depends upon the length of their pendulums, which being sensibly affected
by changes of temperature, they are made to go faster in cold, and slower
in warm weather.
Brittle substances, when unequally heated, are often broken by the
unequal expansions and contractions to which they are liable.  The
danger is greater if the substance is a bad conductor of heat, as is the
case with glass, and particularly if it is thick.  Hence, glass vessels that
are to be used about the fire, or with hot water, should be made as thin
as is consistent with the requisite strength.
Metallic or other instruments used for measuring length or capacity
vary with change of temperature-a circumstance that sometimes occasions serious difficulty where very great accuracy of measurement is
required.
It has been found by very accurate examination, that the Bunker Hill
Monument, which is built of granite, is daily made to change its position
slightly, by the heat of the sun, which expands the sides upon which the
rays fall.
18. Expansion of Liquids.-In solids, the expansive force of
heat is opposed by the cohesion of their
particles, and is therefore less effective than
in liquids, in which there is only a very
slight cohesion of the particles.  A liquid,
therefore, will expand  on being  heated,   A                 -B
much more than a solid.
The expansion of a liquid may be shown in
the following manner. Take a glass flask (called
a mattrass or bolt-head), of the form represented
in the figure, and partly fill it with some liquid,
as water, and tie a thread around the stem, as  m
on A, to indicate the height of the water in it;
and then apply for a few minutes the heat of a
spirit-lamp.  Both the glass and the water will   Expansion of Liquids.
QUESTIONS.-17. What is said of the tire of wheels?  How are brittle
substances affected by sudden changes of temperature?  What is said
of the Bunker Hill Monument?  18. What is said of the expansion of
liquids by heat?  How may the expansion of a liquid be shown?




22                   T H E R Al T  MOMETERS.
be expanded; but the water will expand more than the glass, and will
then rise in the stem, as shown in B.
But all liquids when equally heated do not expand alike,-every one
possesses an expansibility peculiar to itself.  Thus, it has been found by
making the experiment, that 1000 parts of water, at the freezing point,
when heated so as to boil, are expanded to 1046 parts; but
1000 parts of mercury, heated in like manner, expand only
to 1008 parts. Ether is more expansible than alcohol, and
alcohol more expansible than water.
Liquids, as well as solids (16), are expanded more at high
than at low temperatures, by a given addition of heat.
19. Expansion of Gases.-All gases expand equally
when equally heated, and the expansion is proportional
to the increase of temperature.  When 1000 parts of
any gas are heated from 320 to 2120 of Fahrenheit's
thermometer (an instrument soon to be described), they
expand to 1365 parts, or 413 part of the volume at 320
for each degree.
Q~7       In the case of gases that are capable of becoming liquid by
apressure, this law does not hold strictly true when they are
about to assume the liquid form.
SExpansion   To show the expansion of air by heat, let a glass flask, filled
of Gases. with air, be placed as in the figure, with its mouth immersed
in water; then warm it slightly, by grasping the bulb in the hands, or
br)eathing upon it, when the air will escape in bubbles, in consequence
of its expansion by the heat.  On cooling, the air within contracts, and
the water rises in the stem to supply the place of the air which was
expelled.
T HE R   0 ME T ERS.
20. Thermometers are instruments for ascertaining and measuring changes of the temperature of bodies, of which there are
several kinds.  The name is derived from  the two Greek words,
thermos, heat, and metron, a measure.
The first instrument of the kind, so far as we know, was constructed but little more than two hundred and fifty years ago, by
Sanctorio, an Italian philosopher.
Sanctorio's thermometer was made in the following manner.  A
glass tube of small diameter, having a bulb blown at one end, was
QUESTIONS.-Do all liquids expand equally when equally heated?
H-low much do 1000 parts of water expand when heated from the freezing
to the boiling point? 19. Do gases expand by heat? What is the
amount of their expansion for each degree of heat?  How may the
expansion of air by heat be shown? 20. What are thernsoaeters? 




T FIR MOMIETERS.                          23
partly filled with a colored liquid, and the stem passed through a
cork, and inverted in a vessel containing the same kind
of liquid, and having a wide bottom, as in the figure,
so as to stand upright firmly.  Through the cork a
small perforation was made, so as to allow the air to pass
freely, and to the stem a graduated scale was attached,
to mark the rising and falling of the liquid in it.
Now, in an instrument of this kind, it is plain that
when the bulb-is heated, the air within will be expanded,
as before explained, and the liquid in the stem will fall; 
and a motion of the liquid in the opposite direction will
take place when the bulb is cooled.  The rise and fall 
of the liquid will also be proportional to the change of
temperature in the bulb.                                 Air ThermoThis thermometer will very well answer some specific   meter.
purposes, but as it will be affected by changes of atmospheric
pressure as well as by changes of temperature, it cannot be applied
to general use.
The differential thermometer may be considered as a modification of the preceding.        l
It consists of a glass tube, bent twice at
right angles, with a bulb at each end, and
is supported on a stand, as shown in the
figure.  In the tube is contained a portion
of colored oil of vitriol, or other liquid; but
both bulbs are left filled with'air, and to one
of the arms is attached a graduated scale.
When both bulbs are equally heated or
cooled, this instrument indicates no change: 
but if one is heated or cooled more than the  Differential Thermomtcr
other, a motion is at once occasioned in the liquid in the stem, tlhe
direction of which will be readily understood from the explanations
already given.  This thermometer therefore indicates the dicyieree
of temperature at any time existing between the bulbs, and hence
its name.  It is exceedingly delicate, and is especially adapted fur,some particular purposes.
QUESTIONS. -Describe Sanctorio's air thermometer. What objection is
there to its use? Describe the differ ential thler mOometer.




24                    T H ERMOMET E R S.
21. The Common Thermometer.-The thermometer in common use consists simply of a glass tube of an exceedingly small bore,
with a bulb blown at one extremity, and filled with mercury to about
one-third the height of the stem.  The air being expelled, the tube
is hermetically' sealed, and the fr2eezing point ascertained by holding it a short time in water containing ice, and the boiligy point by
holding it in the same manner in boiling water. Both points are
marked on the stem  by a file.  It is necessary that these two
points should be accuratelj determined, in order that the indications of different instruments may be compared with each other.
By.the term freezing point here, is meant the temperature at which
water freezes or ice melts, which, with certain exceptions, is always the
same, as will be fully explained hereafter; so, also, pure water always
boils at the same temperature, provided attention is paid to certain circumstances to be discussed further on in the work. This temperature i,:
called its boiling point.
It will be unnecessary here to give a minute description of the method
of making thermometers, as, at the present day, they can be everywhere
obtained at a very moderate price.  "Besides, the construction, though
simple in theory, is difficult in practice. It requires great tact and dexterity to produce one of very moderate goodness; and without steadily
watching the process as performed by another, or previously possessing
much practical knowledge in glass-blowing, &c., it would be a vain
attempt."-Faraday's Chemical Manipulation, p. 144.
The graduation of the scale of the thermometer is a matter of great
importance; and it would be fortunate for us if we had but one, instead
of three or more, as is the fact. We have seen that in all thermometers
there are two fixed points; and the question now before us is, into how
many parts or degrees, shall the space between them be divided?  Unfortunately, this question has been answered differently by different artists,
and in a manner entirely arbitrary.
Fahrenheit, a German artist, whose thermometer is generally used in
this country and in England, divided it into 180 parts or degrees, and
placed the zero, or the beginning of the scale, 32 degrees below the
freezing point; so that the temperature of melting ice or freezing water'
is 32 degrees, and that of boiling water (32- +180 =) 212 degrees.
Celsius of Sweden proposed to divide the space into 100 parts, and
placed the zero at the freezing point.  His thermometer is called the
centigqrade thermometer, and is used in France and Sweden, and some
other parts of Europe.
* A glass tube is sealed hermetically by rnelting the end by means of the blow-pipe, and
thus perfectly closing it. For this purpose the end is usually drawn out into a fine point.
QUESTIONS.-21. Describe the common thermometer.  What are the
freezing and boilinsg points?  How are these determined?  Describe the
scale adopted in Fahrenheit's thermometer. Where is the zero or beginninlg of this scale? Describe the scale of the centigrade thermometer.




THE R MOMETE RS.                            25
Reaumnur divided it into only 80 parts, placing the zero, or beginning
of the scale, like Celsius, at the freezing point; of course the boiling
point is at 80.
Below zero of each of the scales, and above the boiling point, degrees
are marked, of precisely equal magnitude with those of the other part of
the scale.  Temperatures below zero are usually indicated by placing a
horizontal line before the figures representing the degrees.  Thus,
— 12~ means 12 degrees below zero on the scale used.
The numbers 180, 100, and 80, which severally represent the number
of degrees on the above scales, are to each other as 9, 5, and 4. Recollecting, therefore, that the zero of Fahrenheit is 32 degrees below that of
the other scales, the expert arithmetician will find no difficulty in  educing
the degrees of one scale to those of another.
Thus, to convert the degree of temperature indicated by Faltrenheit's
scale into its centigrade equivalent, we multiply the degrees above or
below 320 by 5, and divide by 9.  Suppose the temperature by Farenheit's thermometer is 1400, what is the corresponding degreie in the
centigrade?  Ex. 140 — 32-= 108, and 108 X 5 = 540, and 540 ~- 9 = 60.
On Fahrenheit's scale, therefore, 140~ are equivalent to 600 of the centigrade thermometer.
Let us suppose again that the temperature by the centigrade thermometer is 600; it is required to find the corresponding degree by Fahrenheit's instrument.  Ex. 60X9=-540, and
540 + 5=108.  To this (108) we must now       F.       C.       R.
add 32, because the beginning of Fahrenheit's scale is 320 below that of the centi-    -212       10    - 80
grade. Thus 1080-+ 32~= 140~.
In this work, and in most works in the       -167
English language, if nothing is said to the
contrary. it is always to be understood that
temperatures are expressed in degrees of          122   -50      - 40
Fahrenheit's scale; but, to avoid confusion,
we often place F., C., or R., after the figures     77   -        _5 20
expressing the degrees, to indicate what
thermometer has been used.
The relation between the three  scales       — 32        0    --
above described is indicated in the accompanying figure.
Though mercury is chiefly used in filling
thermometers, yet other liquids are also
sometimes employed.  At very low tem-          Different Thermometers.
peratures mercury is frozen, so that it
ceases to answer the purpose designed; in such cases, therefore, alcohol
thermometers alone can be used.
22. The Register Thermometer, while it answers the same purpose as another thermometer, at the same time indicates or registers
QuESTIONS.-Describe the scale of Reaumur's thermometer.  I-Tow are
the degrees determined below the freezing point and above the boiling
joint?  How may we convert temperatures as indicated by Fahrenheit's
-ale into its centigrade equivalent?   How may we convert centigrade
ato Farenheit degrees?  Is mercury always used in constructing thermometers?
q




26                   T IIE R IM 0 AI E T E R S.
the extremnes of temperature that may occur during the absence
of the observer.  It consists of two therrnonIeters, with the stems
bent near the bulb, and placed in a horizontal position, attached
to the same frame, as shown in the following figure:
Register Thermometer.
The one usually placed-uppermost is a mercurial thermometer,
having in the tube a small piece of iron or steel wire, which is
pushed forward by the mercury as it expands, but does not recede
with it when it contracts.  The point at which the iron is left, of
course shows the maximum  temperature attained.  The other
thermometer is filled with colored alcohol, and contains in the
liquid in the stem a similar piece of iron, inclosed in glass to pre.
vent oxidation, around which the alcohol flows while that in the bulb is expanding, so as not to be moved, but
which is drawn along with it by capillary attraction, when it contracts so as
to be kept at its surface.  It is therefore left at the lowest point to which
the spirit has contracted, and of course
shows the minimum temperature. Both
pieces of iron or steel, which thus serve
as indices, may be brought to any posi-'tion in their respective tubes by means
A-= —~~ ~~~~ ~  _     of a magnet applied on the outside.
~ \FjW           ~       23. Breguet's Thermometer is made
entirely of solids.  It consists of;i very
Bremuet's Thermometer.   thin strip of platinum, soldered to a
QUESTIONs.-22. Describe the register thlerimometer.  Breguet's therciometer.




T HER  IOMETERS.                            27
similar strip of silver, and coiled in a spiral, as shown in the
figure (page 26).  The upper end of the coil is then attached to
a firm  support, and to the otlher extremity is fixed a pointer or
index, which is made to revolve by any change of temperature,
by reason of the unequal expansions and contractions of the two
metals.  Beneath the pointer is placed a circle which may be graduated to any scale desired.  It is a very delicate instrument.
A modification of this instrument is used in the United States' Coast
Survey, for determining the temperature of the water in deep soundings,
at sea.
The Pyrometer (from pur;, fire, and inetron, a measure,) is an instrument
for measuring temperatures too high to admit of the use of the thermormeter.  The only one now in use is Daniel's pyrometer, which is not
of sufficient importance to require description here. By it the melting
point of cast iron has been shown to be about 27860 F., that of gold
to be about 2016~ F., copper 1996~, silver 18600, and zinc 7130.
24. Exceptions to the general Law of Expansion. —There is
a remarkable exception to the general law (1.4) concerning the
expansion of bodies by heat, as above stated.  Water
is most dense at the temperature of about 400, and
expands, whether it is heated above this point or
cooled below it.
To show this, fill an ounce vial with water at a temperature of 65~0 or 70~, and adapt to it a cork, through which
passes a glass tube of small bore.  Then insert the cork
and tube, and fill the latter with water one or two inches
above the neck of the vial, and expose the whole to the
cold atmosphere of winter, or immerse the vial in a freezing mixture of snow and salt; the contraction of the water
in the vial will very soon be made evident by the fall of
that in the tube; but the falling will shortly cease, and
an upward motion commence, indicating an expansion of
the water in the vial, although its temperature must be      l lil
all the time falling. The volume of the water has therefore first been diminished by reduction of its heat, and Water Expansion
again expanded; and by making use of the thermometer, when Freezing.
it is found that the change takes place at about 390 or 400.
A large thermometer tube, nearly filled with water, may be used for
the same purpose.
25. The most important effects result from  this remarkable
property of water.  If the density of water continued to increase
until it arrived at the freezing point, as is the case with mercury
QUESTIONS. —What is the design of the Pyrometer? 24. What exceptions
are there to the general law of expansion of bodies by heat?  Describe
the method of showing the expansion of water by reduction of temperature,




28                    T II ER M O I ET E R S.
and other liquids, ice would be heavier than water, and as soon as
formed would subside to the bottom in successive flakes, until the
whole of the water, however deep, would become solid.   The
effects of such an arrangement can be easily conceived.  Countries
which, in the present state of things, are the delightful abodes of
innumerable animated beings, would be rendered uninhabitable,
and must inevitably become dreary and desolate wastes.   But,
since water expands previously to its freezing, as well as during
this change, ice is lighter than water, and floats upon its surface,
protecting the water, to some extent, from the further influence
of frost.
The cause of the expansion of water at the moment of freezing is attributed to a new and peculiar arrangement of its particles. Ice is in reality
crystallized water, and during its formation the particles arrange themselves in ranks and lines, which cross each other at angles of 600 and
120~, and consequently occupy more space than when liquid. This may
be seen by examining the surface of water while freezing, and still better
by receiving particles of snow as they fall upon a piece of black cloth.
They will often be found to be small but beautiful crystals or collections
of crystals, presenting a great variety of forms. Some of the more common forms are shown in the figure.
Snow Crystals.
QUESTIONS.-25. Whalt is said of the importance of this remarkableproperty of water? What is suggested as the cause of this expansion of water
in ifreezing?




DISTRIBUTION  OF H EAT.                         29
26. The view just taken of the cause of the expansion of water
when freezing is sustained by the facts observed in the formation
of anchor ice, or ground ice, as it is often called.  This ice is
found in certain circumstances at the bottom of bodies of water,
and not at the top, as with ordinary ice.  It has little tenacity,
and may be supposed to consist of the primary crystals of water.
Separately, they are believed to possess a higher specific gravity
than water, but, when aggregated according to the law stated
above, at angles of 600 and 120~ to form common ice, on account
of the insterstices necessarily left among them, the volume is so
increased as to diminish the specific gravity to the point we usually
witness.-lactnu.scr'ipt -Notes of PIrofessor Cleave(and's Lectures in,
ou;owdoib  College, 1832.
DISTRIBUTION OF HEAT.
Heat constantly tends to diffuse itself, and its distribution is
effected by Conduction, CYovection, Radiation, Reflection, and'ranrsmnission.
27. Condueftion of Heat. —I-eat is said to be conducted, when
it is transmitted fromn particle to particle through a body, as when
one end of a metallic bar is held in the fire until the whole becomes
heated.
The passage of the heat in such cases is evidently progressive,
as may be shown in the following manner.  Take a small bar of
copper, 18 or 20 inches in            ---
length, and  cement to  it
several small bullets, or inar~
bles, about two inches from
each other, by means of wax,
as shown in the figure, and
then  apply  the heat of a
lamp to one end.  As the
heat progresses  along  the              Conduction of Ieat.
bar, it will melt the wax, and the balls will drop off in succession,
QUESTIONS.-26. What is said of anchor ice in this connection?  Wbhat
are some of the modes by which heat tends to diffuse itself?  07. When
is heat said to be conducted?  IHow may the conduction of heat along a
bar of copper be shown?
3*




30              DISTR IBUTION  O' HEAT.
the one nearest the lamp falling first, and the one farthest from
it last.
Substances differ greatly in their power of conducting heat; a
rod of glass, or a piece of charcoal, an inch long, may be heated
to redness at one extremity, and yet be held in the fingers by the
other extremity; but it cannot be done with a similar piece of
nmetal, because, on account of its better conducting power, the
whole very soon becomes too much heated.
The apparent temperature of a body, is determined by the hand,
will often depend upon its conducting power. Thus, if on a cold
morning of winter, the hand is placed upon a piece of metal, and
then upon a piece of woollen cloth, the former will feel much
colder than the latter, because the metal in equal times conveys
away from the hand more heat than the cloth.
28. Substances are divided into two classes in reference to their
ability  to conduct heat, called conductors and non-conductors.
There are, however, no absolute non-conductors; heat penetrates
the substance of all bodies; the only difference in them, in this
respect, is in the rapidity with which
the process takes place. Gold is usually considered the best conducting
substance known; and very porous
solids, the interstices of which are
filled with air, as cotton, or sheep's
wool, and fur, are the poorest conductors.
A convenient method to determine
the relative conducting power of different substances, is, to have them
made into cylinders of equal diameCon~ductio of ~Heat.  ter, and set in a thin piece of wood
at sufficient distances from each other, both extremities of each
piece projecting a little from the wood.  If the board be held in
QUESTiONS.-Do substances differ from each other in their power to con(dclet heat?  Why will some substances feel colder than others, when it is
known that all must be at the same temperature? 28. Into what two
classes are substances divided in reference to their conducting powers e
What is usually considered as the best conductor known? What method
for determining the relative conducting power of several substances is
Dointed outc




DISTR IBCTION  OF  HEAT.                            31
a horizontal position, a small piece of phosphorus may be placed
upon the upper extremity of each of the substances experimented
upon, and the lower ends exposed to the same temperature by
plunging them in heated oil or sand: and the times that elapse
before the ignition of the phosphorus upon the several substances,
will indicate with some accuracy their relative conducting powers.
The following table exhibits the relative conducting power of several
metals and other substances:
Gold............................... 1000   Tin...................................  304
Silver........................  973   Lead............................  180
Copper...........................  898   Marble..............................   23
Platinum...........................  381   Porcelain....................,   12
Ir)n................................. 374   Fine Clay..........................  11
Zinc......I...........................    363
In the arts, advantage is taken of the imperfect conducting powers of
bodies, to prevent the passage of heat in any direction, particularly in
confining it.  Hence furnaces are generally lined with " fire-brick," or a
thick coating of clay and sand.  Wooden handles are fitted to metallic
vessels, or a stratum of wood or ivory is interposed between the hot
vessel and the metal handle.  Ice-houses are constructed with double
Nwalls, which have their interstices filled with fine charcoal, saw-dust, or
some other non-conducting substance, to prevent the influx of heat from
without.
The design of clothing is to retain the heat produced
by the system; and hence the warmest clothing will
be that which possesses the least conducting power. d
In winter, the poorest conductors are selected, and       I d  
in summer the best, as it is then desirable that the
superfluous heat may be permitted at once to escape.
If, in summer, the temperature of the atmosphere
should rise considerably above that of the system,
it would be found advantageous to use the same
clothing as in cold weather.
Snow, in consequence of its imperfect conducting
power, serves as clothing to the earth, and prevents
its surface from being cooled down as low as it would
otherwise be.
Li~quids of all kinds, except mercury, are poor
conductors of heat.  This may be shown by celnenting a thermometer tube in a glass funnel,
inverting it, and filling it with water, so as to   Ether brns on the
cover the bulb about a quarter of an inch, or    surfaceofWatet
eve'-"'k,  as shown in the figure.  Then pour upon the surface
Q -JTIONS. — What is the use of "1fire-brick" in coal-stoves?  How are
ice-houses constructed?  What is the design of clothing?  What is said
of the benefits of snow in winter?  How is the poor conducting power
of liquids shown by the burning of ether?




DISTRIBUTION  OF  HEAT.
of the water a little sulphuric ether, and inflamrn  it; the ether
will burn brilliantly, but without affecting the thermometer for
some time, although the flame is so very near the bulb.
In like manner, heated oil, poured
upon the surface of water in a tumrbler, can scarcely be made to affect
a small thermometer placed at the
bottom.
If a tube ten or twelve inches
long be nearly filled with water and
placed in an inclined position, so
Water boils in vessel with Ice.
that the heat of a spirit-lamp can
be applied near the centre, the water in the upper part of the tube
may be made to boil, while the lower portion will remain per.
fectly cold. If, before applying the heat, a piece of ice be confined to the bottom, it will remain unmelted while the water above
is boiling.  Mercury, though liquid, is a very good conductor
of heat.
cases are even poorer conductors than liquids; and it is for this reason
that very hot or very cold air can be endured in contaot with a person,
though exposure to a liquid of the same temperature would produce intense
pain, or perhaps even worse effects. Double windows and double doors,
with air between them, are sometimes used to insure the greater warmth
of dwellings.
29. Convection of Heat.-Though fluids are poor conductors
of heat, yet, if the heat be applied to the bottom of the vessel containing them, in consequence of the mobility of their particles, it
is rapidly diffused through the whole mass.  The heated portions
are expanded, and becoming, in consequence, specifically lighter
than the rest, they rise through the centre of the vessel, the
colder portions around the sides at the same time descending to
take their place. Thus an upward and a downward current will
be at the same time established, which will continue until the
whole is heated to the boiling point. This mode of distribution is
called the convection of heat.
QUESTIONS.-HOW is the poor conducting power of liquids shown by
the boiling of water in a vessel containing ice? 29. How is the heat distributed through a liquid when it is applied to the bottom of the vessel
containing it? What name is given to this mode of the distribution of heat?




DISTRIBUTION  OF  H}EAT. A3
These currents may readily be shown by filling a flask with water
contaiiiing some insoluble powder, as pulverized gum copal, and applying
the heat of a small lamp, as represented
ill the figure.
When large quantities of water are
slowly heated, the upper portions will
frequently be found quite warm, while
th.t  in the lower part of the vessel
will remain comparatively cold; and this
though the fire is applied beneath. Hence
it is3 not unfrequent, in bathing establishments, to draw both warm and cold water
from the same reservoir.
Similar currents are produced in gases
when heated; and it is on this account
that the heated air, with the smoke and
other lases from a fire, ascend in a chimney, or the pipe from a stove.
30. Radiation of Heat.-A  hot
body suspended in the air emits heat
in all directions in right lines, like Currents formed in vessel of Water
radii drawn from  the centre to the              when heated.
surface of a sphere.   This mode of distribution is termed the
radiation of heat.
The radiation of heat from hot bodies is singularly influenced by the
nature and condition of their surfaces, which is perhaps the most important
circumstance connected with the subject. It is probable that every sub.
stance in nature has a radiating power peculiar to itself, but, in any case,
very much will depend upon the nature of the surface of the body.  By
many experiments, it has been proved that bodies with bright polished
surfaces retain their heat much longer than when their surfaces are
rough and unpolished. Adding even a thin coat of whiting or lampblack
to a bright tin vessel greatly increases the radiating power of its surface,
so that boiling water or other hot liquid contained in it will be cooled
more rapidly in consequence.  The same effect will be produced by
scratching its surface with coarse sand-paper.
Some important practical considerations will naturally suggest themselves
in connection with this subject.  Whenever it is desired that the heat of a
fluid or other substance should be retained, vessels with bright and polished
metallic surfaces should be used, but the reverse if the heat is to be distributed.  Thus tea and coffee pots are usually made of some bright metal,
while stoves and stove-pipes, for the diffusion of heat, are made with dark
and rough surfaces. Pipes to convey steam from the boilers in steamengines to the cylinders, and pipes to convey heated air from furnaces to
the different apartments of a building, should be bright, or else they
should be protected by some non-conducting covering.
QUESTIONS.-30. When is heat said to be radiated?  How is the radiation of heat affected by the nature of the surface of the heated body?
What surfaces radiate best?  What practical considerations suggest
themselves in view of these principles?




3 4             DISTRIBUTION OF HEAT.
31. Reflection of Heat.-That heat may be reflected, may be
shown by standing at the side of a fire in such a position that the
heat cannot reach the face directly, and then placing a plate of
tinned iron opposite the grate, and at such an inclination as permits the observer to see in it the reflection of the fire; as soon as
it is brought to this inclination, a distinct impression of heat will
be produced upon the face.
If a line be drawn from a radiating substance to the point of a plane
surface by which its rays are reflected, and a second line from that point
to the spot where its heating power is exerted,
]R IP  the angles which these lines form with a line
perpendicular to the reflecting plane are
xx,    /   called the angles of incidence and reflection,,              and are invariably equal to each other.
Thus, let AB (see figure) be the reflecting.........,,.  surface, and R a ray of heat, which strikes
A D       _B   this surface at D, in the direction RD; it
Reflection of 1Heat.  will be thrown off or reflected in the direction
DI. If a perpendicular PD be erected at the
point D, the angle RDP will be the angle of incidence, and IDP the angle
of reflection.
These principles, which have just been developed concerning heat,
apply as well to the invisible rays emitted from a moderately heated
substance, as to those accompanied by light from an incandescent body,
or the rays of the sun.
32. The Absorption of ]Heat by bodies sustains an intimate
relation both to its radiation and reflection.  Bright and polished
surfaces, it is well known, are the best reflectors; and these are
just the ones, we have seen (30), which radiate least. And
rough, unpolished surfaces, which radiate heat best, are found to
be the best absorbers.
Surfaces may therefore be divided into two classes, those which
afford an easy passage to heat, and those which do not.  The
former will be good radiators and absorbers, and the latter good
reaectors and retainers.
The color of a body influences considerably its absorbing, but not its
radiating power; surfaces that are black, other things being equal, absoi b.
ing heat more readily than those of a lighter color.
QUESTrioNS.-31. How may the rejfection of heat be shown? Define the
angles of incidence and reflection. Do these principles apply to rays of
heat unaccompanied by light? 32. What surfaces are the best absorbers
of heat?  Into what two classes may surfaces be divided in reference
to their power to transmit heat?




DISTRIBUTION  OF  HEAT.                             35
Both the radiation and the reflection of heat are well shown by placing
a heated cannon-ball in the focus of a concave reflector, having another
similar reflector facing it at a distance, in the focus of which is placed one
A                                       B
Parabolic Reflectors.
of the bulbs of a differential thermometer. The rays from the ball C are
reflected in parallel lines from the reflector A (see figure), and are again
concentrated on the thermometer D, by reflection from the second concave
mirror B.
If a piece of phosphorus be substituted for the thermometer at D, it
may often be inflamed, even when the reflectors are ten or twenty feet
distant from each other.
If a lump of ice is made use of, instead of the heated ball, the thermometer in the focus of the other reflector will fall; in which case the bulb
of the thermometer is the radiating body, and its heat is received by
the ice.
33. Transmission of Eeat.-When a ray
of heat is thrown upon a body, it must either
be reflected, absorbed, or transmitted by the
body.  We have already seen the conditions
upon which reflection and absorption depend,  11l          ii
and it remains only to consider the circum-   J   Itill   i  I tt 7/
stances of transmission.  
In general, transparent substances afford the          1,   11 
most ready transmission of heat, but there is a  ll                 i
great difference among them  in this respect. I       l     u{    I 
Even atmospheric air transmits heat but imper-'lij           J iI tllll  ii Y    i
fectly.  This is shown conclusively by an experiment of Davy.  He contrived to heat a platinum'"'ill     I.
wire by means of galvanism, within a receiver con-      i'    l 
taining two concave reflectors, with a thermometer  Transmision of Heat in a
in the focus of one of them, the heated wire being       Yacuum.
in the focus of the other.  Now, when the air was
exhausted to I~,th part of its ordinary density, the thermometer, it  as
QUESTIONS.-Explain the effect of parabolic reflectors in reflecting
heat. How is a lump of ice to be used instead of a heated ball? 33. When
a ray of heat falls upon a body, in what three ways may it be disposed
of? How does the presence of the air affect the transmission of heat?




36                  RELATION OF HEAT
found, would be raised, by means of the ignited wire, three times as
high as when the air in the receiver was at its natural p reasurA.
Bodies that transmit heat freely are said to be diatherAialnous (fronm
the two Greek words, dia, through, and thermos, heat), as those which
sfford a free passage to light are said to be transparent.
By experiments made with a very delicate piece of apparatus, called
the thermo-multiplier, it has been shown that the most diathermanous substance known is rock-salt, in pure transparent crystals.  Of different
specimens of glass, some are much more diathermanous than others.
though all are equally transparent; and some colored glasses, and other
bodies only partially transparent, afford a ready passage to heat, or are
highly diathermanous.
It appears, also, that the ray of heat, like a ray of light, is really compound, or composed of rays of heat of different kinds, some of which have
a greater penetrating power as regards most diathermanous media, than
others.  In this respect heat from an oil-lamp will differ from that of a
spirit-lamp, though both are equally intense; and the heat of both will
differ from that of heated metal.
The rays of heat from the sun possess this penetrating power, as I
have called it, in a greater degree than any kind of artificial heat.  Thus,
p, pane of window-glass, held between the face and a coal-fire, is found at
once to intercept most of the heat; but no such effect is produced by
holding it before the face when exposed to the direct solar ray.
The rays of heat, like those of light, may be refracted; and some of
them being more refrangible than others, like the different colors of light,
they may be separated from each other by means of the prism.
The ray of heat, like a ray of light, may also be polarized, and in a
similar manner.  See Decomposition and Polarization of Light.
RELATION   OF  HEAT  TO  CHANG ES IN  THE
STATE OF BODIES.
34. Relation of the Three Forms of Matter to each other.We have seen above (10), that, omitting the imponderable agents,
which are not known to be material, every substance must be in
one of the three forms, or states, solid, liquid, or gaseous; and
that the particular form a body assumes will depend upon the
relative intensity of the cohesive and repulsive forces existing
among its particles.
If the repulsive force be comparatively feeble, the particles will adhere
so firmly together, that they cannot move freely upon one another, thus
QUESTIONs.-What are diathermanous bodies?   Will heat from  all
sources be transmitted alike? What is said of the rays of the sun is:
this connection?  May the rays of heat be refracted?  Polarized 
34. Upon what will the particular form or state of a body depend?




TO CHANGES IN BODIES.                          37
constituting a solid. If cohesion is so far counteracted by repulsion that
the particles move on each other freely, a liquid is formed; and, should
the cohesive attraction be entirely overcome, so that the particles not only
move frieely on each other, but would, unless restrained by external pressure, separate or expand to an indefinite extent, an aeriform substance
will be produced.
Now, the property of repulsion is manifestly owing to heat; and as it
is easy, within certain limits, to increase or diminish the quantity of this
principle in any substance, it follows that the forms of bodies may be
made to vary at pleasure: that is, by heat sufficiently intense, we have
reason to believe, every solid, provided decomposition does not take
place, may be converted into a liquid, and every liquid into vapor. The
converse ought also to be true; and, accordingly, several of the gases
have been condensed into liquids by means of cold, or cold and pressure
combined, and the liquids have been solidified. The temperature at
which liquefaction takes place is called the melting point, or point of
fusion; and that at which liquids solidify, their freezing point, or point of
congelation.  Both these points are different for different substances,
but usually the same, under similar circumstances, in the same body.
35. Liquefaction. —By the liquefaction of a substance, we mean
its reduction from either the solid -or gaseous to the liquid state; but
generally it is the former change which is intended.
If, when the temperature of the air is at zero, as is often the
case in some parts of our country, a quantity of ice be brought
into a room, and placed near a fire, it will be gradually heated, like
any other solid, as a thermometer placed in it will indicate, until
the temperature reaches 320; but it will stand at this point until
the whole is melted. The thermometer will then begin again to
rise, as it did before. Now, it is plain that it must have been
receiving heat as rapidly while the thermometer was stationary,
as before and afterwards; but the heat thus communicated did
not affect the thermometer, because it was all absorbed by the ice,
and was expended in changing the ice into water. It has therefore become insensible to the thermometer, and is properly called
latent heat; and if it was known to be material, we might perhaps, with some propriety, consider water as a compound of ice
and heat.
The quantity of heat which is thus lost or becomes insensible,
during the melting of a mass of ice, is sufficient to raise the tenmQUESTIONS.-To what is the property of repulsion owing?  What is
the melting point of a body?  The freezing point?  35. What is meant by
the liquefaction of a body?  Is heat always required to produce liquefaction?  Why cannot ice be heated above 320?
4




38                 RELATION OF HEAT
perature of an equal weight of water about 1400, as may be shown
in the following manner:  Let a pound of water at 32~ be mixed
with a pound of water at 1 72~, and the temperature of the mixture
will be intermediate between them, or 1020. But if a pound of
water at 172~ be added to a pound of ice at 320, the ice will quickly
dissolve, and on placing a thermometer in the mixture, it will be
found to stand, not at 1020, but at 320.  In this experiment, the
pound of hot water which was originally at 1720, actually loses
140~ of heat, all of which enters into the ice, and causes its liquefaction, without affecting its temperature.
36. Heat of Fluidity.-The heat thus required for the liquefaction of solids is often called their heat of fluidity; and the
quantity necessary for the purpose is not the same in any two
substances.  While the heat of fluidity of water is, as we have
just seen, 1400, that of spermaceti is 1450, that of lead 162~, that
of tin 5000, and that of bismuth 5500.  That is, to melt any given
weight of one of these substances, an amount of heat is required that
would heat the same weight of the substance the number of degrees
indicated, provided no change of state should take place during
the process.
The melting point of nearly all substances is the same as their freezing
point; but this point varies greatly in different substances. Thus, solid
mercury melts (and liquid mercury freezes) at — 390~; ice at 320; spermrnceti at 1320; sulphur at 2260; tin at 4420; lead at 6120; zinc at 7780;
silver at 18730, and gold at 20160.
37. Freezing  llfixtures are made of various salts and liquids,
which have such an affinity for each other, that rapid liquefaction
is produced, without the direct application of heat.  But as this
agent is always required when this change takes place, it must be
absorbed from surrounding objects, which therefore lose their heat,
or become cold. A good mixture of this kind is made of snow, or
finely broken ice, and common salt, both of which, when mixed
together, become rapidly liquid; and the process is attended with
great cold, so that a thermometer immersed in it will fall to zero,
QuEsTIONS.-WVhat is the quantity of heat absorbed by ice when it is
melted?  How is this shown?  36. What is the heat oq fluidity of a substance? Will it be the same in all substances? What are the meltiig
points of the several substances mentioned?   37. What are freezing
mnixtlures?




TO  CIIAN GES IN  BODIES.                      39
or below. Of course, if a vessel of water be immersed in it, the
water will in a short time be frozen.
Saltpetre, dissolved in cold spring water, will often reduce the temperature to 32~, or lower, so that water may be frozen by it; but the
greatest cold is produced in this mode by mixtures of certain of the salts
and acids. Thus, powdered sulphate of soda three parts, and diluted
nitric acid two parts, mixed at 500, will sink the temperature to -3~;
arnd phosphate of soda nine parts, and the same diluted acid four parts,
will produce a cold of -12~.  The greatest cold that can be produced in
this way is found to be about — 100~, but by other means still lower temperatures have been obtained. But it is not possible, in the present state
of our knowledge, entirely to deprive a body of heat.
Since solids, on becoming liquid, absorb heat, as we have seen,
it necessarily follows, that when liquids become solid, heat must
be given out. The freezing point of water is usually said to be
320; but if it be contained in a close vessel, and cooled very slowly
without agitation, its temperature may be reduced, without freezing,
to 200, or lower.  Slight agitation will now cause it to freeze suddenly, and the temperature will rise at once to 320, the ordinary
freezing point.  The portion that has frozen, therefore, has given
out sufficient heat to raise the temperature of the whole mass
some 120.  Saturated solutions of several of the salts, made at
elevated temperatures) upon being slowly cooled, exhibit the same
phenomenon.
A beautiful experiment may be performed by making a saturated solution of Glauber's salt in warm water, and setting it aside
in a closely corked vial till it cools.  If now the cork be removed,
or the vessel violently agitated, the salt will immediately crystallize,
and a thermometer placed in it will rise several degrees.
38. Provision of Nature. — We cannot but notice here the
beautiful and unexpected manner by which nature, to some
extent at least, checks the cold of winter, which might otherwise
be destructive.  The cold atmosphere causes large quantities of
water to congeal, but at the same time heat is given out, which
prevents so great a reduction of temperature as might, but for
this circumstance, be experienced.
QUESTIONS.-What is the greatest cold that can be produced by freezing
mixtures? Is heat given out when liquids become solid? May water
have its temperature reduced below the ordinary freezing point?  What
is the effect on the thermometer when freezing at length is prodused?
Describe the experiment with Glauber's salt..3'8. How is the excessive
cold of winter to some extent checked?




40                 RELATION OF HEAT
The peculiar mode provided by the Creator to check the heat
of summer, which might otherwise become excessive, will be
noticed hereafter.
39. Vaporization. —By the term  vaporization is meant the
conversion of solids or liquids into gases.
Aeriform bodies are often divided into vapors and gases, according to the relative force with which they resist condensation; but
the distinction is of little consequence.
Heat is always required to convert a solid or liquid into a gas;
usually, it is communicated directly, as when water is made to
boil over a fire, but if not applied directly, it will always be
absorbed from surrounding bodies.
In most cases, when heat is applied to solids, they first melt, or
become liquid, and afterwards, by a continuance of the heat, are
converted into vapor; but some, as metallic arsenic, and certain
salts, pass at once, when heated, from the solid to the gaseous
state.
Gases occupy considerably more space than the liquids from
which they are formed.   Water, when converted into steam,
expands about 1700 times, so that a cubic inch of water forms
nearly a cubic foot of steam; but most liquids expand much less
than this.  Alcohol, for instance, is expanded, when converted
into vapor, only 659 times its original volume, and sulphuric
ether 443 times.
Volatile substances are such as are readily converted into vapor
by heat or at ordinary temperatures, while those that are incapable
of this change are often called fixed substances.
Two or more gases, whatever may be their density, when brought
in contact, readily intermix with each other, and become equally
diffused through the vessel that may contain them.  This is seen
in the atmosphere, which is composed of gases differing in density,
but they remain uniformly diffused.
If we fill two bottles with gases of different densities, as hydrogen and
carbonic acid, and connect them by a narrow tube, as shown in the figure
on p. 41, the lower containing the most dense gas, in a short time the two
QUEsTIONS.-What is meant by vaporization.2 Is heat.always required
when a vapor is formed? Do gases occupy more space than the solids or
liquids from which they are formed?  I-low many times does water expalnd
when it takes the form of steam? Alcohol? Ether?




TO  C:HANG}ES  IN  BODIES.                       41
gases will diffuse themselves equally through the whole space.
The mixture of the gases will even take place through thin
membranes, whether animal or vegetable; the least dense of
the gases passing the most rapidly.
A good method to show this is to fill an ox bladder with
carbonic acid, or even atmospheric air, and suspend it with
the neck tied firmly in a large vessel filled with hydrogen.
A transfer of the gases through the substance of the bladder
will take place, but the hydrogen entering more rapidly
than the denser gas escapes, the bladder will after a time
be burst.
40. Ebullition-Boiling Point.-When a liquid in
an open vessel is exposed to any source of heat, the
temperature gradually rises, like that of any other substance in similar circumstances, until a certain point Diffusion of
is attained, when a violent motion commences in it,    Gases
called ebzullition or boiling; and  no heat can then cause any
further increase of temperature.  If the heat be continued, the
quantity of liquid gradually diminishes, or, as we familiarly say,
is boiled away, until the whole is gone. The commotion in the
liquid is occasioned by portions of it at the bottom, where the heat
is applied, being converted into vapor, and rising in bubbles to
the surface.
Ordinarily it will be found that water boils at 2120, which is
therefore called its boiling point; but the temperature at which
other liquids boil is not necessarily the same, every liquid having
a boiling point peculiar to itself.  Thus, the boiling point of alcohol is only 1730, and that of sulphuric ether 960, while that of
sulphuric acid is 6200, and that of mercury 662~.
41. Boiling Point dependent upon Circumstances.-But the
boiling point of a liquid is not to be considered as perfectly constant; it depends upon several circumstances, the most important
of which is the pressure of the atmosphere upon the surface of the
liquid. By heating a small vessel of water to about 2000, and placing
it under the receiver of an air-pump, it begins to boil when the air
is very moderately exhausted.  So, on ascending a mountain, by
QuESTIONs.-What is said of the diffusion of gases of different densities?  Describe the experiment with the ox bladder.  40. What is ebullilion or boiling?  What is the effect of continuing the heat?  What is the
boilinyg point of water? Is this point in other liquids the same? 41. What,oxre the circumstances which affect the boiling point of a liquid? Describe
the experiment with the air-pump.
4*




42                RELATION  OF HEAT
which a part of the atmospheric pressure is avoided, the boiling
point falls in proportion to the ascent.  At the hospital of St.
Bernard, situated upon a point on the Alps, about 8400 feet above
the sea, water boils at 196~; and on the top of Mount Blanc it
was observed by Sausure to boil at 184~.
This is just as we should expect, for the expansion of the vapor
has to take place directly against the pressure of the atmosphere
on the surface of the liquid; and the degree of heat necessary tL
produce the expansion will be to some extent proportional to th
expansive force required.
The pressure of the atmosphlere at the surface of the sea is
usually about 15 pounds to each square inch, but it is subject to
some variation; and the boiling point of any liquid will of course
vary at the same time with the atmospheric pressure.
In a perfect vacuum, water boils at 720, and
sulphuric ether at — 46, or about 140~ lower
than in the open air.
As might be expected, sulphuric ether may
easily be made to boil under an exhausted receiver, without heat, even in the coldest weather.
For this purpose let a little good ether, in a wineglass, be placed under an air-pump receiver, as
represented  in the figure; upon working  the
Boiling of Ether.  pump, it will boil violently.  The experiment
will usually succeed best if some small pieces of
metal are dropped into the ether, before placing it under the
receiver.
While the boiling is in progress considerable reduction of temperature takes place, and water contained in a small vial placed
in the ether will be frozen.
42. Other circumzstances affecting the boiling point are, the
nature of the containing vessel, and the presence of soluble substances in the liquid.  Thus water boils in metallic vessels at
2120, but in a clear glass vessel one or two degrees more are
QUESTIONS.-What is said of the boiJing point upon high mountains?
What is the boiling point of water in a vacuum?  Describe the experiment with ether under the exhausted receiver of the air-pump? While
the ether boils how is the thermometer in it affected? 42. 1WYhat other
circumstances are mentioned as affecting the boiling point?




TO  CHANGES IN  BODIES.                        43
required; so any substance, as a salt, held in solution in the
water, causes a rise of the boiling point.  Water saturated with
common salt bo'ls at 224~; saturated with saltpetre at 238~, and
with chloride of calcium at 264~.
43. Effect of increased Pressure.-If water or other liquids
boil at a lower temperature by diminishing the pressure upon the
surface, so a higher temperature is required for this purpose when the pressure is ir1nreased, as in a steam boiler.
W~ater cannot be heated above 212~ in
the open air, because any additional heat
is expended in converting a portion of it
into steam, which at once makes its escape
into the air; but if it be confined in a
strong vessel, it may be heated to any                 /.
temperature even to redness.
The rise of the boiling point under
increasing pressure is well illustrated and          c
proved  by  Iarcet's steam  aplparatus,                /2
which is represented in the accompanying figure.  A  is a hollow  brass globe,
supported on a stand, and in it is contained a little mercury, and a small quan- 
tity of water. Through an air-tight collar,           T    /
a graduated glass tube, C, is inserted, so
as to reach very nearly to the bottom,        A
both ends of it being open.  B is a thermometer, having its bulb in the water or
mercury.  Now, by applying a lamp the 
water is heated, and when the temperature has risen to 212~, the steam  will 
begin to issue freely through the faucet,
F; but, by closing the faucet, the escape      Maucet's Apparatus.
of the steam will be prevented, and the
temperature will rise; the mercury at the same time by the pressure of the steam within, being forced up the tube C.  And the
QUESTIONS. —43. Why cannot water be heated above 012~ in the open
air? What, if the steam be confined? Describe Marcet's steam apparatus.




44                RELATION  OF' HEAT
height to which it may rise will always show the exact amount of
the pressure.
By this means it has been determined that, at a heat of 250~,
the tension of steam, thus confined in a boiler, is equal to two
atmospheres, or 30 pounds to the square inch; at 275~ its tension
is equal to three atmospheres; and four atmospheres, or 60 pounds
to the square inch, at 294~.
The expansive force of steam confined in this manner is the
propelling power in the steam engine.  (See author's Nat. PhfilosoeAy, p. 173.)
44. Evaporation.-But it is not only when a liquid is heated,
and made to boil, that it is changed into vapor; this change, in
most, and probably in all liquids, and many solids, is ever taking
place, whatever may be their temperature, when they are contained in open vessels.  This slow formation of vapor is termed
evacporation.  It is seen in the drying of clothes, when wet with
water or alcohol, and in the gradual diminution of a quantity of
either of these liquids, when left in an open vessel.  Even in the
formLs of ice and snow water gradually evaporates.
Evaporation is much more rapid in some liquids than in others;
and it is always found that those which have the lowest boiling
point evaporate with the greatest rapidity.  Thus, alcohol, which
boils at a lower temperature than water, evaporates also more
freely; and ether, whose point of ebullition is yet lower than that
of alcohol, evaporates with still greater rapidity.
The chief circumstances that influence the process of evaporation, are extent of surface, and the state of the air as to temperature,
dryness, stillnzess, and density.
The same quantity of liquid, exposed in a shallow vessel, wil
evaporate more rapidly than in one of a different form, because
of the large amount of surface in contact with the air; so, also
currents in the air increase evaporation by removing the vapo,
as fast as it is formed.  Increased pressure of the atmosphere
diminishes evaporation.
QUESTIONs.-What is tle tension of steam at 2500? 44. Do water and
other liquids take the form of vapor without ebullition? Do all liquids
evaporate with the same facility?  What are the chief circumstances
which influence evaporation?




TO  CHIA NGES IN  BODIES.                       45
45. Eeat is absorbed by the Formation of Vapor.-During
the slow evaporation of water, or other liquids, as well as when
they are evaporated by boiling, a large amount of heat is absorbed,
and becomes latent in the vapor produced.  It is. on this account
that ether, alcohol, or even water, though at the same temperature
as the air, always feels cold when a little is dropped upon the hand.
The natural heat of the hand is absorbed and carried off in the
vapor that is formed.
The evaporation of good sulphuric ether may easily be made to
freeze water, even in the warmest weather. For this purpose let a
very small glass vial, covered with muslin,
be filled with water, and suspended by the
neck from  some convenient support; then
drop slowly upon the muslin good sulphuric
ether, from  the mouth of a vial, or by
means of a dropping  tube.   In  a few w/
iminutes, ice will begin to form; and if the
operation be continued, the whole of the
water will be frozen, perhaps breaking the
vial containing it.
Porous earthen vessels are often used in hotels
and other places, in warm weather, to contain
water for drinking.  A portion of the water
gradually exudes through the vessels, and evaporates from the surface, by which that within
is kept several degrees colder than the temperature of the atmosphere. Such vessels are
said to be much used in Spain, where they are
called alcarrazas.  People crossing the deserts
of Arabia in caravans, are said sometimes to load
camels with earthenware bottles filled with water, Freezing of Water by EYapowhich is kept cool by wrapping the jars with     ration of Ether.
linen cloths, and keeping them moist with water.
46. The freezing of water by its own evaporation under the
receiver of an air-pump, is a common experiment.  A  shallow
dish containing strong oil of vitriol is first placed upon the plate
of the machine, and over it, supported by a tripod of wire, is
placed a small capsule filled with water.  The receiver being now
put in its place, covering the whole, by working the pump the
QUEISTONS. —45. Is heat absorbed during the slow evaporation of as
liquid?  Describe the mode of freezing of water by the evaporation of
ether. 46. Describe the experiment with water and sulphuric acid under
the receiver of the air-pump.




46                 RELATION OF HEAT
air is exhausted, rapid evaporation from
the surface of the water commences, which
is continued because of the absorption of
~     15          the vapor by the acid beneath, until the
water is frozen.   Without the acid, or
other substance to produce the same effect,
the receiver would soon  be filled with
vapor, and no further evaporation take
place; the vapor of water, at ordinary
temperatures, not having sufficient tension
-____   to lift the valves of the pump, as it is
worked.  Indeed, a small drop of water
Freezing Water under Exhausted Receiver with   may be frozen under the receiver of an
Oil of Vitriol.      air-pump by its own evaporation, without
the use of any substance to absorb the vapor. Let a single drop
of water, on a piece of charred cork, hollowed a little on its upper surface, be
placed under the air-pump receiver, and
I      by working the pump a few seconds, it
will be frozen by the rapid evaporation
which takes place from  its surface.  The
burnt cork capsule is preferable to one
of glass or metal, since, as the water does
not adhere to its surface, not so much heat
is received from it.
________       4.7. Latent Heat of Vapors. —It is not
easy  to  determine  with  precision  the
Freezing Water by its own   amount of latent heat in vapors, or the
Elvaporatiotn.    relative quantity of heat absorbed as they
are formed.   The results obtained by different experimenters,
therefore, are not uniform.  It is believed that water, in taking
the form of vapor, absorbs nearly 1000~ of heat, or heat enough
to raise the temperature of an equal weight of water 10000, if it
could be confined.  The amount of heat in different vapors vaiies
QUESTIONs — What purpose does the acid serve?  Explain the method
of freezing a drop of water upon a piece of burnt cork under an,aihausted receiver. 47. What is the amount of latent heat in steam?




TO  CHANGEiS IN  BODIES.                        407
with their nature; in no two vapors is it the same.  Thus, while
the latent heat of watery vapor is, as we have seen, about 1000~,
that of vapor of alcohol is only 3730~, that of vapor of ether 1630~
vapor of oil of turpentine 138~, and of sulphide of carbon 144~.
The heat which is absorbed when water or other liquid is converted into vapor, will, as a matter of course, be given out again
when this vapor is condensed into the liquid form. On this prin.
ciple, steam is often used for warming buildings, being conveyed
in pipes through the different apartments.  As it passes along the
pipes, it is condensed, giving out its heat; and the water that is
formed runs back again into the boiler.
48. Distillation.-The process of distillation consists simply in
evaporating a substance, and again condensing the vapor, by
causing it to come in contact with a cold surface.  This is usually
accomplished by having a tube of considerable length, leading
from the top of a close boiler, and passing in the form of a spiral
through a vessel which is kept filled with cold water.
In the laboratory, the apparatus figured below answers well for
distilling small quantities of
any liquid.  A retort, R, contains the liquid to be distilled,
and the vapor is received into
a flask, F, the mouth of which
is slipped on the neck of the   RR 
retort, but the joint not made 
perfectly air-tight.  The flask 
should be kept cold by being
immersed in cold water, or by                                   I
having  a small stream   of                                r'lil    j /
water constantly falling upon _-I.... _:
it from a vessel above.            /,'1
For larger operations, a, Lei-     "               -e"'...
big's condenser is indispensable.           Distillation.
It consists of a glass flask, for a
boiler, which may be heated in a small furnace, as represented in the
figure on page 48, or by means of a spirit-lamp, and a metallic case, (1,
in which is inserted, through perforated corks, a glass tube, dd, designled
QuEsTINs. —Describe the mode of warming buildings by the use of
Bteam. 48. In what does the process of distillltion consist?




48                  RELATION  OF  HEAT
to be kept constantly surrounded with cold water.  From the vessel, i, o
stream of cold water enters the funnel, c, and, as it is heated, escapes at
the highest part by the tube, h, and is collected in a basin, b.  The gl'ass
tube, dd, is connected at one end, by means of a smaller tube, with the
boiler, and at the other end, with the receiving-vessel, e, in which is col
Il
Distillation.
lected the distilled liquid condensed in passing through the tube, dd. The
crooked funnel in the boiler serves to introduce the liquid to be distilled.
By the process of distillation volatile substances, whether liquid or
solid, may be separated from those that are fixed, or even from such as
are less volatile than themselves  Water is distilled to purify it from
salts or other substances it may contain in solution or suspension; and
alcohol, by distillation, is separated from water, which is less volatile
than itself, as well as from fixed substances.
The application of this process to solids is usually termed their sub.
limation.
49. Boiling produced by Cold. —WTe have seen above (41) the
effects of diminishing or removing the atmospheric pressure in
promoting ebullition, and we are now prepared to understand
another ingenious method of accomplishing this object.   Let a
flasl, with a cork well fitted to its mouth, be partly filled with
water, and made to boil briskly by means of a spirit-lamp; then
suddenly insert the cork  and remove the lanlp: the water will
QUESTIONS.-Describe Leibig,'s condenser. iTow is it that substances
may be separated from  one another by distillation?  49. Describe the
experiment of boiling water by the application of cold.




TO  CHANGE-S IN  BODIES.                        49
continue to boil, and by immersing it in comd 
water, as shown in the figure, the boiling will              T
become violent.  The same effect will be pro-    l{f!;!jTl4
duced by inverting the flask and  applying   1
snow or even cold water to the bottom.  But
if the flask be held again a moment over the 
lamp, the boiling will instantly cease.  The
reason of this is, because the upper part of
the flask, when the cork is inserted, is filled  
with steam, which is condensed by the appli-           Ii
cation of cold to the outside, and a vacuum 
produced,  The warm water within then boils,        Boii by old
as in a vacuum produced by any other means;
but if heat be applied, steam will be again formed, and fill the
upper part of the flask, and, by its pressure upon the surface of
the water, prevent further boiling.
If the flask is firmly corked, so as to exclude the air perfectly, when
it has become cold the water within, as the flask is handled, will fall from
side to side, almost like masses of ice, and producing a similar sound to
the ear. This is because there being no air within to break up the water
as it is thrown in any direction, it falls in a mass and strikes against the
sides of the glass with much the same effect as a solid. A small toy of
this kind, made of glass tube, and hermetically sealed, is called a waterhammer.
50. The Cryophorus. -  The cryophorus, or
frost-bearer (firom the two Greek words, crmos,
frost, and phero, I bear), is an instrument for
freezing water by its own evaporation, which
beautifully  illustrates some  of the foregoing
principles.  It consists of a tube, half an inch
or more in diameter, with a bulb blown at
each end, one of them  having a small aperture, A, by which a small quantity of water
is introduced, sufficient only partly to fill one
of the bulbs.  This water is first all collected
in  the lower bulb, and  the heat of a lamp    _..
applied, so as to cause it to boil briskly; and       Cryophorus.
while the interior is filled with steam, the aperture at A is quickly
QuESTIONS.-What will be the effect of holding the flask over a lamp?
What is the effect if, when cold, the flask is shaken?  50. Describe the
cryorphorus.
6




~50                  E LA RELATION  OF HEAT
scaled hermetically, and the lamp removed.  When it has become
cold, the water is passed to the upper bulb, as represented in the
figure (p. 49), and the instrument supported on a stand, with the
lower bulb in a beaker glass.  All the interior is now filled with
vapor of water, except a part of the upper bulb, but no evaporation of the water can take place, because of the presence of this
vapor.  But by removing the vapor, which is accomplished by surrounding the lower bulb with a freezing mixture of salt and snow,
to condense it rapidly, evaporation of the water is produced, attended
with cold sufficient to freeze the most of it, even in the warmest
weather.
The pulse-glass, as it is called, is a very similar instrument, and
is made in the same manner, except
that ether is used in it, instead of
water.  By grasping one of the bulbs
firmly in the hand, the vapor, by its
expansion, will immediately force all
the liquid into the other; and the
moment it has all passed through the stem, an appearance of violent ebullition is produced, attended by a distinct sensation of
cold in the hand which grasps the bulb.  This is occasioned by
the rapid evaporation of the film  of liquid lining the inside of
the bulb.
51. Effect of Perspiration upon the Animal System.-The
effect of evaporation in withdrawing heat is admirably illustrated by
the process of perspiration.  The natural temperature of the human
body is about 980, but when we take active exercise, or are exposed
to a great degree of heat, there is a tendency to a rise of temperature above that which is conducive to health; and the most
injurious effects would ensue, if they were not prevented by the
rapid evaportation which takes place from all parts of the surface
of the system.
Examples of the power of the human body to sustain great and
apparently even dangerous elevations of temperature, are on record,
It is well known that individuals have voluntarily exposed thcemQUEsT IONs.-Desciribe the pulse-glass. 51. What is the effect of pe7spirei
tion upon the animal system?  Will the human body sustain high tem.
peratures for a time without injury?




To CH ANGES IN  BODIES.                         51
selves for several minutes, in ovens, to temperatures even a huncdred degrees above that of boiling water, without suffering any
injury.  The very rapid perspiration that takes place in such circumstances, prevents the destructive elevation of temperature in
the system which would otherwise take place.
52, Temperature of the Seasons Xodified —The heat of suminer is always greatly modified by the evaporation which take
place from the surface of the earth, and the stalks and leaves of
plants and trees.  When a stalk of Indian corn (zea maize), or
other plant, is cut down in midsummer, or a branch removed
from a tree, the leaves soon begin to wither, because of the evaporation of the moisture in them.   But the evaporation is no
more rapid from  them  after being cut than before, but now the
supply of water from the earth, received by the roots, ceases, and
the withering we notice is a necessary consequence.   We see
therefore that vegetation in warm weather is sending forth into
the atmosphere immense quantities of water by evaporation, besides
that which rises from the surface of the earth itself; and as a result,
the temperature of the atmosphere is more or less cooled.  In other
words, the heat is thus prevented from becoming as excessive as it
would be but for this arrangement.
We have seen above (38) that heat given out by the freezing
of water in winter, prevents the low reduction of temperature that
would otherwise be experienced; and we cannot here less admire
the wonderful provision of Providence, by which, on the other
hand, the excessive heat of summer is, to some extent, limited.
53. Liquids upon very Hot Surfaces.-Liquids, as water, thrown upon
metallic surfaces, heated nearly to redness, instead of adhering to the
surface and rapidly evaporating, will sometimes be seen to roll around in
globules, apparently without touching, until at length they gradually
disappear. This is occasioned by an atmosphere of vapor that is formed
around the globules of liquid, by its rapid formation preventing the temperature from rising as high as the boiling point, and also. by its elasticity preventing the liquid from coming in contact with the metallic plate.
Alcohol dropped upon the surface of heated oil of vitriol, exhibits a like
phenomenon.  This has been called the spheroidal state of liquids.
QUESTIONS.-52. How is the heat of summer modified?  Why does a
plant-stalk, separated from its root, so rapidly wilt in warm weather?
Is water constantly evaporating from the leaves and stalks of plants?
53. Describe the action of a drop of water upon a very hot surface.




52                RELATION  OF HEAT
54. Dew. —Dew is a deposit of moisture from  the atmosphere
upon a cold surface in contact with it.  If, in the summer, a vessel is left but a few minutes filled with ice-water, or even cold
spring-water, dew soon collects upon it, and after a time, the water
thus condensed trickles down the surface in drops. A surface
upon which dew is seen to form will always be found colder than
the surrounding air; and the particular temperature at which it
begins to form is called the dew-point.  When the air is very dry,
this point will always be considerably below the temperature of the
air; but when there is much moisture present this will not be
the case.
In fair weather, during the summer season, there is usually
seen, in the morning, a copious deposit of dew upon the leaves
of plants, and upon other substances exposed to the open air.
This is occasioned by the radiation of heat from bodies at the
surface of the earth,. which takes place rapidly during the night,
cooling them down considerably below the temperature of the air.
Substances, therefore, which radiate slowly (30), as polished
metallic surfaces, seldom have any dew upon them, while good
radiating surfaces near them will be abundantly covered with it.
In cloudy weather (without rain), there is generally little dew,
because the heat radiated from the earth is reflected back by the
clouds; and by suspending even a small handkerchief by the four
corners, a few inches from the earth, the deposition of dew on
substances under it is, for the same reason, prevented.
In some warm countries, water is said to be frozen during the
night by the rapid radiation which takes place from its surface.
The water for this purpose is poured into shallow pans, so situated
as to receive as little heat as possible from the earth.
55. Hygrometers.-Hygrometers are instruments for determinit', the relative quantity of watery vapor present at any time in
the atmosphere.  Daniel's hygrometer (represented in the figure
on p. 53) is much in use. It consists of a tube, A, with a bulb
at each end, and is formed in the same manner as the cryophorus
QUESTIONS.-54. What is dew? Under what circumstances is it deposited?  -lHow do the leaves of plants and other bodies at the earth's
surface become colder than the air?  Why is there usually little dew in:loudy weather? 55. What are hygrometers?




TO  CHANGES IN  BODIES.                      5$
(50), except that it contains ether instead
of water.  The tube is supported by a stand;  
and the lower bulb, which is usually made I
of colored glass, is about half filled with the,"
ether, having in it the bulb of a very deli-  A      K 
cate thermometer, with its stem extending
upward in the tube.  The other bulb is         l      i
empty, or contains only the vapor of ether,           1
and is covered with muslin.  To the stand
1B is attached a small thermometer, to indi- 
cate the temperature of the air.  By pour.
intg a little ether upon the muslin, the bulb
is cooled, and the vapor of ether within
condensed, and a rapid evaporation of the
ether in the bulb produced, as in the cryo-      Hygrometer
phorus,  This occasions a cooling of the colored bulb, and a
deposition of dew upon its surface, the small thermometer within
showing the exact temperature at which the process commences,
which is taken as the dew-point.  Properly, however, it is the
difference between the temperature thus obtained, and the temperature of the air, which shows the real state of the air as to
moisture.
A decided objection to the use of this instrument is found in
the fact, that it is extremely difficult to determine accurately
the moment when the formation of dew upon the bulb actually
commences.  Its indications, therefore, cannot always be fully
relied on.
The wet-bulb thermometer is now mostly used to determine the
hygrometrie state of the atmosphere.  Two thermometers are
attached to the same support, as shown in the figure on p. 54,
one of them having a piece of muslin wrapped around its bulb,
which is kept wet by a string leading to it from a small fountain
of water, attached also to the support between the thermometers.
Now, as the evaporation from the muslin necessarily reduces the
temperature, this thermometer will always stand a little lower
than the other, the bulb of which is dry; and, moreover, as the
QUESTIONS. -Describe Daniel's hygrometer.  Describe the wet-batlb
the rmometer.
5*




54                  RELATION  OF  HEAT
rapidity of the evaporation from  the muslin will
depend upon the dryness of the air, the difference
between  the readings of the  thermometers will
indicate its true hygrometric condition.
56. Watery vapor exists in three different states:
1. As transparent, invisible steam, as it rises from
boiling water, and before it comes in contact with
the air; 2. As it appears partially condensed, after
escaping into the air; and 3. As it exists in the
1   atmosphere at all temperatures, but invisible to
the eye.   That steam, before coming in contact
with the atmosphere, is perfectly transparent and
invisible, is shown by partly filling a glass vessel
with water and causing it to boil rapidly.  The
Wet-bulb Thermometer.    steam  within, above the water, cannot be seen
until it escapes into the air, and becomes partially
condensed, as stated above.
Clouds are collections of watery vapor, in this partially condensed state, in the upper regions of the atmosphere, and differ
from fog only in their more elevated position.
The moisture that constitutes clouds, when fully condensed,
falls in rain upon the earth, or is solidified and falls in beautiful
crystals (25), as snow.  If the drops of rain are frozen after they
are formed, hail is produced.
If in warm weather a quantity of air be forced into a large glass
receiver, so as to produce a pressure of at least two atmospheres, a
slight mistiness will usually be seen within, occasioned by a partial condensation of the watery vapor forced in with the air.  If the process is
several times repeated, drops of water may be obtained, forming a kind
of artificial rain.
In the manner stated above, all the water upon the surface of the
earth is subjected to a constant natural distillation; pure water, in the
form of vapor, rises in the air from the leaves of plants, from the earth,
and from the surface of the ocean, rivers, and lakes, to be agfin diffused,
in rain and snow, over the earth, producing everywhere vigor and life,
both in the vegetable and animal world.
57. Liquefaction and Congelation of Gases.-By great pressure, or by pressure and a low reduction of temperature, many of
QUE STIONs.-56. In what three states does watery vapor exist?  What
are clouds?  What is rain?  57. How may many of the gases be reduced
to the liquid state?




TO  CHANGES IN  BODIrES.                      55
the gases may be reduced to the liquid state, and the liquids thus
formed solidified or frozen.  Indeed, all gases may be considered
as the vapors of extremely volatile liquids.  Some of them, however, have never yet been reduced to the liquid state.
The usual method to liquefy a gas, is to put the materials from
which it is to be formed into
a strong glass tube, bent in
the middle, as represented in
the figure, and hermetically
sealing it.  As the gas is
evolved the pressure of course increases, but at length a point is
attained, depending upon the temperature and the nature of the gas,
when it begins to condense as a liquid, the quantity of which is increased by the further evolution of gas from the materials, without
any increase of pressure, if the temperature is kept uniform.  The
bent tube is particularly adapted for the liquefaction of cyanogen
gas.  To form this gas, dry cyanide of mercury is used, a portion
of it being placed in the closed end of the tube, and the other end
hermetically sealed.  Moderate heat is then applied to the end
containing the cyanide, the other end being cooled by a freezing
mixture of snow and salt.  As the cyanide is decomposed by the
heat, the cyanogen first takes the gaseous form, but is subsequently condensed by the pressure and cold, and collects in the
empty end of the tube.
Of the different gases, some require a much greater pressure
than others to condense them to the liquid state. At 0~ sulphurous
acid gas becomes liquid under the ordinary atmospheric pressure,
but at 320 it requires a pressure of 2 atmospheres to produce the
effect.  Carbonic acid gas at 0~ has a tension of 23 atmospheres,
and at 32~ a tension of 36 atmospheres; at higher temperatures
the tension is still more increased.
The liquids formed from  the gases, in the manner described,
may be frozen by the great cold produced by their own evaporation, or by exposing them in tubes to intense cold.  In the former
Case, the solids formed will appear like snow, and in the latter, like
tlear, transparent ice.
QU3ESTIONS.-What is the usual method to liquefy a gas 9 Do all gases
require a like pressure to reduce them to the liquid state?




56                 RELATION  OF HEAT
58. For preparing small quantities of solid carbonic acid, the
fiolowing apparatus answers well, and is much less expensive than
such as are usually purchased of the manufacturers of philosoplhical instruments.
The generator, A, is made of a common mercury flask, having the aper.
ture at the neck a little enlarged, so
as to be about an inch and a quarter
in diameter.  A plug of cast-steel, B,
LE                   is then made of a bar two inches at
1,    L      dM  least in diameter, and turned with a.i..,,,i~               wide and smooth shoulder so as to fit
accurately upon a collar of block-tin,
when screwed into its place, as represented in the figure.  The valves,
which are the most difficult part to
construct, on account of the great
pressure that is to be overcome, are
inserted in the plugs, a second one
l  A  ~lii~   C          of which, precisely like the preceding,
is made to screw into the receiver, C.
Into the upper end of each plug, a hole
"ll'l~ 1,. |  lllm1||  N   an inch in diameter is bored about one
lh+  1     011 AL!inch deep, and terminates in a conical
S""' ~         ij,=l<Ad....   point; from which an aperture, a tenth;j..ill. of an inch in diameter, is bored quite
Solidifying Carbonic Acid.  through the plug. E H is composed
of two parts, so constructed that when
screwed firmly into the cast-steel plug, and the part H which terminates
in a conical point screwed down, all escape of the gas from the generator
is effectually prevented. When the part H is screwed upward, the escape
of the gas around E is prevented by the firm pressure of the shoulder
of E upon the washer I, and a shoulder upon the lower part I-H, which
presses against the bottom of E, and produces the same effect with regard
to the escape of the gas around the thread of the screw H.
Instead of the valve described above, the following answers better for
the generator, as the passage at the bottom of the plug is
not liable, as in the other construction, to be closed by the
sulphate of soda which is formed. The part H extends
IH t       quite through the plug, having at the lower extremity a nut,
P, attached firmly by a screw and soldered. Now when the
i1i|!     screw tH is turned upward, the thread on which extends
from I downward about an inch, the nut P perfectly closes
the passage below, but by turning the screw down, the
passage through the plug is opened at P, and closed at
I, allowing the gas to escape laterally, as in the other
construction,
The receiver, C, is made of common boiler iron, and
should be about two inches internal diameter, and of the
same height as the generator, which will make it of the capacity of
QUESTIONS.-58. Describe the apparatus for preparing solid carbonic
acid.




TO CHANGES IN BODIES.                            57
about a pint.  The tube L should screw into the plug connected with the
receiver, having its other extremity terminate in a conical point to fit
into a cavity prepared for it in the other plug.  By means of the stirrup.
screws NI and N, and the block of wood 0, the receiver may then be
firmly screwed in its place; and when both the valves are open, there
will be a free passage.between it and the generator, but no communica.
tion of either with the open air.
To make use of this apparatus, the generator and receiver are separated,
and the plug B being removed, 2- pounds of bicarbonate of soda, made
into a paste with the same weight of water, are introduced into A, and
21~ ounces of strong sulphuric acid are poured into several copper vessels, made a little shorter than the length internally of the generator, and
of such a diameter that they will just pass the aperture.  These being
nearly filled with acid are dropped into the generator, which, after the
plug B is inserted, is allowed to lie on one side for fifteen or twenty
ninutes, and several times rolled over, to mix the acid with the soda.
The receiver is then attached to it as seen in the figure, by means of the
stirrup-screws MI and N; and, if kept sufficiently cool by means of ice,
the liquid carbonic acid formed in A will shortly be distilled over into C,
the passage between them being of course previously opened.
The valves are now to be closed, and the receiver, which contains the
liquid carbonic acid, separated from the generator. A small tin cup (not
represented in the figure) is then to be attached to the tube L, to receive
the jet of acid from the receiver. It is essential that the liquid acid should
escape into this cup, which is effected by having a small tube pass from
the steel plug nearly to the bottom of the receiver, or by inverting the
receiver before opening the valve.
The apparatus should be well tested, at least three times, before running any risk by venturing to handle it while charged. This is best done
by means of a hydraulic press; but the same object may be accomplished
very effectually by standing the apparatus when charged in a tub of water
heated to about 160~, so that when the apparatus and water have attained
the same temperature, it shall not be lower than 1300. If a more severe
test is desired, the water may be made still warmer.
In constructing an apparatus, care should always be taken to make
the receiver of not more than one-fifth the capacity of the generator.
The quantity of materials used should also be just sufficient very nearly
to fill the generator.
In using this apparatus, when the liquid is received in the cup, it
hisses and boils with the greatest violence; and the cold produced by
the evaporation of a part of it is so great as to freeze the rest, which is
retained in the cup as a fine white snow. By rolling this in balls, and
wrapping it in cotton, it may be kept some time; but in the open air it
evaporates rapidly, and intense cold is produced, equal, it is said, to
-1480. By moistening the solid with ether, and placing it in an exhausted
receiver, it is claimed that a temperature as low as 1750 or 1800 below
sero has been produced.
The solid does not mix with water when immersed in it; a ball
of it thrown upon the surface of water floats about lightly, and at
QUEsTIoss.-How is the freezing of the liquid accomplished?  At
what temperature is the solid formed?




58                   SPECIFIC  HEAT.
le6ngth a portion of water in contact with it is frozen by the intense
cold.  With sqlphuric ether or chloroform  it mixes readily, and
the pasty mass rapidly evaporates, producing intense cold.
Mercury which congeals at about -40~ is readily frozen by
being kept a short time in contact with the solid, surrounded by
some cotton, or by immersing it in a mixture of the solid and
ether or chloroform.
SPECIFIC  HEAT.- CAPACITY  OF  BODIES  FOR
HEAT.
59. When a body is exposed to any source of heat, its temperature rises, and the substance of heat is supposed to accumulate in it; but the same quantity'of heat, imparted to different
bodies, will not raise their temperature alike.  Thus, if a pound
of water and a pound of mercury, in similar vessels, and at the
same temperature, be exposed to the same source of heat, the
temperature of the mercury will rise about 300, while that of the
water rises only 1~.  It appears, therefore, that it requires 30
times as much heat to raise the temperature of water any given
amount, as it does to produce the same effect upon mercury.
This idea is expressed by saying that the specific heats of these
substances are as 30 to 1; or we say (as some prefer) that the
eapacity for heat of water is to that of mercury as 30 to 1.
If, instead of comparing equal weights of the two substances,
we take equal volumes-as a pint of each-and expose them  to
the same uniform  source of heat, we shall find that while the
water gains 10 of heat, the mercury will gain 2~, or a little more.
To express this relation we use the term  relative heat; and we
say therefore that water has more than twice the relative heat of
mercury.
Other methods of determining the specific heat of bodies have
been devised, one or two examples of which will be given. If a
QUESTIONs.-What is said of the solution of the solid in ch!loroform and
ether? How may mercury be frozen by use of the solid acid? 59. Will
the same quantity of heat imparted to different bodies heat them alike?
If like quantities of water and mercury are exposed to the same source
of heat will they in the same time be heated alike?




SPECIFIC   HEAT.                            59
pound of olive-oil and a pound of water be heated to some given
temperature, say 800, and then placed in a cold room, and the
number of minutes noted which is required for each to cool an
equal number of degrees, say to 50~, it will be found that the oil
will cool in less than half the time required by the water; but as
both substances must be supposed to lose equal quantities of heat
in equal times, it follows that the water must have contained more
than twice as much as the oil; or the capacity of water for heat
is more than twice that of this oil.
If a piece of copper, of a pound weight, be heated to 3000, by
holding it a few minutes in mercury at this temperature, and then
immersed in a pound of water at 500, the copper will give out
heat to the water until the temperature of both will be at 72~.
Now, the copper has lost 228~ of heat, and the water has acquired
22~.  The specific heat of water, therefore, is to that of copper as
228 to 22.
It is usual to make water the standard in comparing the specific
heats of bodies, considering its specific heat as 1'000; we shall
then have the specific heat of mercury 1'o000 —033, and that of
copper 22 —'096.
No two substances have the same specific heat, but every substance has a specific heat peculiar to itself, and which is to be
considered as one of its own peculiar properties.
The following table exhibits the specific heats of several wellknown substances:Water....................... 1.000  Gold......................... 0'032
Iron.......................... 0.114   Silver.................  0'057
Copper.....................  0'096  Alcohol...................  0'645
Lead..................... 0.031   Tin.............0.............. 0'056
Sulphur...................... 0-203   Platinum................   0032
Phosphorus.................  0188   Zinc.......................... 0'095
Diamond.................... 0-119  Mercury..................... 0033
Graphite.................... 0.202   Oil of Turpentine......... 0'467
Charcoal.................... 0'201  Ether....................... 0 503
The specific heat of a body depends to some extent upon its temnperature, being greater as the temperature is higher.
Change of density in a body is usually attended by a corresponding change in its specific heat, which is increased as the density is
QUESTIroNs.-What is the ratio of their capacitiesfor heat, or their specific
hleats?  What is taken as the standard for the specific heat of bodies?




60       NATURE  AND  SOURCES  OF LIG I-HT.
diminished, and diminished as the density is increased. This is
seen in solids, as when a piece of iron is heated by hammering,
which increases its density and causes a portion of its latent heat
to be given out, thus raising its temperature; but is best illustrated by the gases, the densities of which are more easily made
to vary at pleasure. Thus, if we suddenly compress a portion
of a gas, its temperature is sensibly raised; but, on the other
hand, if we diminish its density, it becomes colder by the absorption of heat occasioned by its increased capacity for heat.  A
delicate thermometer placed under the receiver of an air-pump
falls as the air is exhausted.
60. The Fire Syjr'inge is an instrument by which
dry tinder or spunk may be ignited by the heat produced by the sudden compression of a portion of atmospheric air.  It consists of a hollow  cylinder,
closed at one end, and a solid piston fitting it
accurately, and having in its under side a cavity to
receive the substance to be ignited.  To use it, the
tinder or spunk is put in the place fitted for it, and
the piston is then plunged forcibly into the cylinder;
on removing it, the combustible substance will generally be found ignited.  If the cylinder is of glass,
a flash of light will often be seen when the air is
Fire Syringe. compressed.
II. LIGHT.
NATURE  AND SOURCES OF LIGHT.
61, Nature of Light. -Although innumerable observations
and experiments have been made upon light, yet it must be
admitted that some doubt and obscurity still remain concerning
its real nature.  But, in the absence of positive knowledge, two
theories of light have been proposed, by each of which nearly all
QUESTIONS.-How does change of density in a body affect its specific
heat?  60. Describe the fire syrinye. 61. Do we understand fully the
real nature of light?




NATURE AND SOURCES OF LIGHT.    61
the phenomena attending it may be satisfactorily explained; and
it is admitted that each is also attended with its peculiar difficulties.
These are called the Newtonian, or corpuscular, and the undulatcyry
theories.
62. The Newtonian theory supposes light to be material, and
to consist of inconceivably minute particles, which, however, are
too subtile to exhibit the common properties of matter.  These
particles, emanating from luminous bodies, such as the sun, the
fixed stars, and incandescent substances, and traveling with irnmense velocity, excite the sensation of light, it is supposed, by
passing bodily through the substance of the eye, and striking
against the expanded nerve of vision, the retina. The whole
language of optics is founded on this theory.
63. The undulatory theory, or theory of.Huygens, which is
now generally adopted, denies to light a separate material existence, and ascribes its effects to the vibrations or undulations of a
subtile ethereal medium, supposed to be universally present in
nature, the pulses of which, in some way excited by luminous
objects, pass through space and transparent bodies, and give rise
to vision by impressing the retina, in the same way as pulsations
of air impress the nerve of hearing, to produce the sensation of
sound.-(See Natural Philosophy, p. 188.)
64. Light is not a homogeneous substance, as might be supposed, but the white light of the sun is made up of rays of several
different colors, as will be shown when we come to speak of its
decomposition, or analysis.  So, also, it is capable of producing
several distinct classes of effects, which have been attributed to the
action of distinct agents; as the colorific rays, or the rays which
produce the phenomena of color, the heating rays, and the chemical rays, or those which are capable of producing chemical changes.
Thus it is possible, by causing the solar ray to pass through certain
substances, to separate the heat entirely from it; or its illuminating
power may be destroyed, and a distinct, invisible ray of heat be
obtained. So, also, chemical effects may be produced by rays which
seem to be destitute of any heating or illuminating power.
QuEsToNs.-62. Describe the Newtonian, or copuscular theory of light.
63. Describe the undulatory theory. 64. What colored rays are contained
in the white light of the sun? What other rays?
6




62    NATURE AND SOURCES OF LIGHT.
65. Sources of Light.-The sun is the great source of light to
the earth, and all things upon its surface.  As rays of heat always
accompany the light of the sun, it is natural to suppose that the
sun is an intensely heated mass, which is constantly throwing off
both light and heat in every direction, like a red-hot cannon-ball
suspended in the air; but this cannot be proved.  At the present
day, it is generally believed that the body of the sun is a dark,
opaque substance, surrounded by luminous clouds, unlike anything, perhaps, with which we are acquainted upon the earth, but
which are the real source of the sun's rays. These clouds are
supposed to be of great thickness; but occasionally they break
away in places, showing the body of the sun beneath them, which
constitute the spots often seen upon his surface.
The great distance of the sun from the earth-95,000,000 of
miles-very probably will ever prevent us fiom  knowing more
with certainty of his real nature.
Artificial light is produced by various modes, but chiefly by
combustion, by the burning of a lamp or candle, or a mass of
charcoal; but it may also be produced by galvanism,-in a manner to be hereafter explained,-by decaying animal and vegetable
substances, called phosphori, and by every means which produce
great heat.
All bodies begin to emit light when heat is accumulated within
them in great quantity; and the appearance of glowing or shining,
which they then assume, is called incandescence.  The temperature at which solids in general begin to shine in the dark, is
between 6000 and 700~; but they do not appear luminous in
broad daylight till they are heated to about 10000.  The color
ofincandescent bodies varies with the intensity of the heat.  The
first degree of luminousness is an obscure red.  As the heat augments, the redness becomes more and more vivid, till at last it
acquires a full red glow.  If the temperature still increase, the
character of the glow changes, and by degrees it becomes white,
shining with increasing brilliancy as the heat augments.  Liquids
and gases become incandescent when strongly heated; but a very
QUaESTIONS.-65. What is the great source of light to the earth? How
is artificial light produced?  At what temperature do bodies begin to
emit light?




NATURE AND SO URCES OF LIGHT.    63
high temperature is required to render a gas luminous, more than
is sufficient for heating a solid body even to whiteness.  The dif.
ferent kinds of flame, as that of a wood-fire, candles, and gas-lights,
are instances of incandescent gaseous matter.
Artificial lights differ greatly in color, some being of a brilliant
white, and others being red, blue, yellow, or green.  The chemical
agency of artificial light is in general analogous to that from the
sun; but in most cases it is too feeble to produce very decided
effects.
66. Many substances have the power of emitting a feeble light, unattended by sensible heat, and are called phosphori (from two Greek words,
lhos, light, and phero, I bear). Certain living animals also possess the
same property, as the glow-worm, and the common fire-fly.  This property of bodies is termed theirphosphorescence.
Some phosphori, as that prepared by mixing sulphur and oyster-shells,
and exposing the mixture for a time to a strong heat, the diamond, fluorspar, &c., shine only after having been heated, or exposed for a few
moments to a strong light; while others, as moist, decaying wood, and
decaying fish, shine without such preparation, even at ordinary temperatures.
Light sometimes appears during the process of crystallization. This
is exemplified by a tepid solution of sulphate of potassa in the act of
crystallizing; and it has been likewise witnessed under similar circumstances in a solution of fluoride of sodium and nitrate of strontia. Another instance of the kind is afforded by the sublimation of benzoic acid.
Allied to this phenomenon is the phosphorescence which attends the sudden contraction of porous substances. Thus, on decomposing by heat
the hydrates of zirconia, peroxide of iron, and green oxide of chromium,
the dissipation of the water is followed by a sudden increase of density
suited to the changed state of the oxide, and a vivid glow appears at the
same instant. The essential conditions are that a substance should be
naturally denser after decomposition than it was previously, and that the
transition from one mechanical state to the other should be abrupt.
67. Photometers are instruments for measuring the comparative
intensities of different lights, of which several kinds have been
proposed; but it does not enter into our present purpose to
describe or discuss their comparative merits.
To determine the comparative intensities of two lights, as that
from different candles or lamps, the following method, originally
proposed by Count Rumford, is perhaps as reliable as any; and
has the advantage of requiring little and very cheap apparatus.
Let L be a lamp, and C a candle, the lights of which we desire to
QuESTIONS.-Do artificial lights differ in their colors?  66. What are
phosphori P  67. What are photometers 2




64      NATURE  AND  SOURCES  OF LIGIIT.
compare. Provide a screen, S, of white paper, which is to be put
in a frame and properly supported by a stand, as shown in the
figure, and also a small cylinder, C, of wood or some opaque substance.  Then place this cylinder in an upright position in front
of the screen, in such a position that its shadow from both of the
lights shall be thrown side by side upon the screen, but not overlapping each other, and removing the lights to different distances,
until the shadows appear of perfectly equal intensities.  The comparative intensities of the two lights will then be as the squares
of the distances of the lights from  the screen.  In the present
case, L' will be the shadow from the light of the lamp, and C'
that from the light of the candle; and the intensity of the lamp
light will be to that of the candle light as LL'2is to CC'2. If LL'
Photometer.
is 50 inches and CC' 45 inches, then will the light of the lamp be
to that of the candle as 2500 is to 2025, or as 1'234 is to 1.
This method is founded upon the fact to be illustrated in the
next paragraph, that the intensity of the light from any luminous
body, at different distances, will be inversely as the squares of
those distances.
The experiment must, of course, be conducted in a dark room.
QuESTIONS.-Describe the method of determining the comparative
intensities of two lights by a comparison of the shadows they produce




DISTRIBUTION  OF LIGHT.                        65
DISTRIBUTION OF LIGHT.
68. Light is distributed,, or diffused abroad, by several modes;
as by radiation, reflection, 9refraction, &c.
Light emanates from every point in the surface of a luminous
body, and is equally distributed on all sides, if not intercepted,
diverging like radii drawn from  the centre to the surface of a
sphere.  Thus, if a single luminous point were placed in the
centre of a hollow sphere, every point of its concavity would be
illuminated, and equal areas would receive equal quantities of
light. Each ray, when not interrupted in its course, and while
it remains in the same medium, moves in a straight line, as is
obvious by the appearance of shadows cast by the side of a house,
or of a sun-beam admitted through a small aperture into a dark
room.  Owing to these modes of distribution, it follows that the
quantity of light which falls upon a given surface decreases as the
square of its distance from the luminous object increases-the same
law which regulates the heating power of a hot body.
69. The passage of light is progressive, time being required for
its motion from one place to another.  It comes to the earth from
the sun in about 8~ minutes,-a distance of 95,000,000 miles,which shows its rate of progress to be about 195,000 miles a
second. Owing to this prodigious velocity, the light caused by
the firing of a cannon or a sky-roclket is seen by different spectators at the same instant, whatever may be their respective distances from the rocket, the time required for light to travel 100
or 1000 miles being inappreciable to our senses.
70. Reflection of Light. —Light is reflected in the same manner as heat (31), obeying precisely the same laws. This always
takes place when it passes from one medium into another of different nature or density, whether the media be solid, liquid, or
gaseous. Different media, however, differ much in their power
of reflection.
Bright metallic surfaces, as polished silver or clean mercury,
QUESTIONs.-68. How is light distributed?  Does light emanate from
every point of an object? What is said of the course of a ray when not
interrupted? 69. Is the passage of light from point to point instantaneous? What is its velocity? 70. When is light said to be reflected?.
(6*




66            DISTRIBUTION OF LIGHT.
reflect nearly all the rays which fall upon them; while those
which are dull and rough reflect but a few. The reflection of
light, like that of heat, takes place at the surface of bodies, and
appears to be influenced rather by the condition of the surface
than by the internal nature or structure of the reflecting body.
Let A B be the reflecting surface,
-D:E,   E C the ray incident at C, and C D the
reflected ray, and let PC be perpen
dicular to AB.  EC P will then be
___-.....:.    _.       the angle of incidence, and P C D the
angle of reflection, both of which will
&,           TB'     be equal.  It is not necessary that the
Reflection of Light.  reflecting surface should be a plane, as
might be supposed;-it may be either concave, as a b, or convex,
as A' B', and the same results would follow.
Light has precisely the same characters after being reflected as
before, but is less intense, because of the absorption of a part of
the rays.
71. Refraction of Light.-When a ray of light passes through
the same medium, as glass or water, or when it passes perpendicularly from one transparent medium to another, it moves in
perfectly straight lines; but when it passes ob'i;quely from one
medium to another of different density, it is thrown more or less
out of its first direction, and is said to be refracted.
Thus, a ray of light, R, passing through
the air, when it comes in contact with a
_________  piece of polished glass at A, does not move
on in a straight line to R', but is bent
downward or refracted, and emerges from
Refraction of Light.    the glass at B, where it is again refracted
Refraction of Light.    in the opposite direction, and takes the
same course, though not precisely the same path, as it had
at first.
Refraction always takes place when a ray of light passes obliquely
from one medium to another of different density, but not always to
the same amount; this will depend upon the refracting flower of
QUESTIONS.-Describe the angles of incidence and reflection. 71. When
is light said to be refracted?




DISTRIBUTION  OF LIGHT.                        67
the two media, and also upon the obliquity of the ray to the surfaces of the media in contact.
When the ray passes from a rare to a dense medium, it is always
refracted or bent towards a line perpendicular to the surface at the
point of contact, and from this line when it passes in the opposite
direction, from a dense to a rare medium.
To understand the relative positions of the incident and th
refracted ray, in the case of any two media, the following law
needs to be well studied.  Let A B in the figure be the surface
of some transparent medium  more                P
dense than air, as water, and let
I C be a ray of light incident upon    i
it at C; it will not pass on in a
straight line, but on entering the   1           C
water will be bent downward, to
E; I C is then called the incident
ray, and C E  the refracted ray.
Let P P' be a line perpendicular                    i
to the surface at C, then angle           Index of Refraction.
I C P will be the angle of hicidence, and E C P' the angle of
e'efraction.
If now from. C as a centre we draw  the circle A P B P', and
also the lines I a and E c both at right angles to P P', then will
I a be the sine of the angle of incidence and E c the sine of the
angle of refraction.  And for the same two media these lines will
always have the same ratio to each other, whatever may be the
angle of incidence.  Thus, if a second ray, iC  be incident at C,
it will emerge at e; and the sines of the angles of incidence and
refraction, that is, the lines i b and e d will have to each other
the same ratio as the lines Ia and Ec; and the same will be
true for the same media, whatever may be the angle of the incident ray.
The quotient obtained by dividing the sine of the angle of incidence by that of the angle of refraction is called the index of
ret.fraction for the media used; for the same media it is always
QUESTIONs. —What is the course of the ray in passing from a rare to a
dense medium?  When from a dense to a rare medium? Describe the
angles of incidence and of refraction. Describe the index of refraction.




DECOMPOSITION  OF LIGHT.
the same, but varies with different media.  Usually the air is
taken as one of the media, so that the index of refraction for any
substance is the quotient thus obtained in the case of a ray of
light in passing from  air into that substance.  The index of
refraction for water is thus found to be 1'33, for common flint
glass 1'56, for oil of cassia 1'64, for phosphorus 2'22, and for the
diamond 2 43.
(For the Polarization of Light; see the author's "Natural
Ptilosophy.")
DECOMPOSITION  OF  LI GHT.
72. The Solar Spectrum.-The white light of the sun is not a
homogeneous substance, but is capable of being separated into
several rays of entirely different colors.  This was first effected
by Newton, by passing it through a triangular piece of clear, solid
glass, called a prism.
In the figure following, let S be a ray of light from the sun,
admitted into a darkened
VIOLET                       X      room  through  the windowINDIO                               shutter, D E;  it will pass
IBLUE: ~ -— ~~'~~.A ~13~,//~ $downward to the floor, at a
cREE N   =!                         little distance from  the wall,
YELLOW                    C          p
ORANGE / -—,B  producing a circular spot of
ORE,         /                     clear white light, W.  Then
",,'RED'~'~~ _/'22~'/let the prism A B C be held
/~/'-'                         in the ray, and at once the
iDecompostion of Light.      spot at W  will disappear, and,
Decomposition of Light.
in its stead, an elongated and
beautifully colored image of the sun will be seen upou a screen
hung up in front of the window, or on the wall at the opposite
side of the room, if no screen be used.  The several colors will
appear in the order indicated, the violet being uppermost and the
red lowest.
QUESTIONS.-What is the index of refraction for water?  Flint-glass 
Diamond? 72. Hlow may light be decomposed?  Describe the exueri.
nent with the prism.




DECOMPOSITION  OF LIGHT.                        69
It will be seen that the light, in passing the prism, has been
twice refracted, or bent upward, first as it entered the glass, and
again as it issued from it; and that the separation of the several
colors has been in consequence of their different refrangibilities.
The violet being most refrangible, is found uppermost in the
picture, and the red is lowest, because least refrangible.  The
other colors occupy intermediate positions, depending upon their
respective refrangibilities.
The colored image thus produced is called the solar spectrum;
and, according to Newton, it is composed of the seven colors
named in the figure, which are therefore called pribmary colors.
73. More recent investigations by Brewster render it probable
that there are in the spectrum really only three colors, r'ed, yellow,
and blue, and that the other shades are produced by mixtures of
these in different proportions; a mixture of the blue and the yellow, for instance, producing the green, and a like mixture of the
red and yellow producing the orange.  Indeed, it is believed that
each of these three colors extends over the whole spectrum, but
each is much more intense at one part of the spectrum than elsewhere, the blue being most intense near the top, and the red near
the bottom, with the most intense portion of the yellow between
them.  The solar spectrum, therefore, as produced by the prism,
may be considered as composed of three simple spectra superimposed upon each other.
The distribution of the rays in each of   3        Y       x
these simple spectra is represented by the
shading of the annexed figures, in which B
represents the blue, Y  the yellow, and R 
the red, each color being supposed to be
separated from  the others.  If the three         -
spectra be thrown one upon another on the
same screen, the ordinary solar spectrum
will be produced.                              Colors of Spectrum.
74, Heating and Chemical Rays.-It has been stated above
that light is capable of producing several distinct classes of
QUESTIoNs.-What are Newton's primary colors?  Why are these separated by the prism? 73. What colors only are contained in the spectrum,
according to Brewster? How are the other colors produced? 74. In what
part of the spectrum are the greatest heating effects produced?




70            DECOMPOSITION. OF LIGHT.
effects, as those of color, those of heat, and besides these, others
which may strictly be called chemical effects.  Now, these several
effects are not produced in every part of the spectrum with equal
facility; the greatest illuminating power is found to be in the yel.
low, while the greatest heat is in the red, or a little below it, and
the greatest. chemical effects are produced in the extreme violet.
The chemical effects of light are various and important; a mixture of chlorine and hydrogen gases may be kept together in the
dark for any length of time, without combining, but unite with
an explosion when placed in the direct sunlight.  On the other
hand, many compound substances are decomposed by light, as
certain preparations of gold and silver.  If a piece of white paper
be coated over with a thin film of white chloride of silver, carefully prepared in the dark, and then placed in the solar spectrum,
the part in the violet ray will soon become black, while that in the
red will:scarcely be affected.  Between these extremes there will
be produced various shades of gray and purple.
It appears, therefore, that the sun's light is made up of three
kinds of rays, viz., the colorific rays, or rays of light proper, the
heating rays, and the chemical rays, the last of which are most,
and the heating rays least, refrangible.
The light of the sun produces most important effects in the vegetable
world; many plants will not grow in the dark, and others growing in the
shade have their nature entirely changed. But a discussion of these
topics does not belong to our present subject.
75. Photography. —By this name we designate the various
modes of producing pictures by the action of light..  If a piece
of white paper is moistened with a dilute solution of common salt,
and then one side of it washed with a solution of nitrate of silver,
the surface becomes coated with chloride of silver, which readily
turns black or dark chestnut by exposure to the direct rays of the
sun.  If, now, before exposing paper thus prepared to the light,
any small flat object, as a flower, or piece of lace, be placed upon it,
an image of the object will remain upon the paper, and may be
QUESTIONS.-In what part of the spectrum are the greatest chemical
effects produced?  Does the light of the sun produce any important
effects upon vegetable bodies? 75. What is photographty?  What method
is mentioned for preparing a photographic paper?




DECOMPOSITION OF LIGHT.                         71
rendered permanent by soaking it imzniedicatey in a saturated
solution of common salt, or of iodide of potassium.
The unaltered chloride of silver in the paper is by this soaking
dissolved out, while the part that has become colored resists the
action of the solvent and therefore remains in the paper.
Talbot's Calotype Process, invented by a gentleman of this
name, is conducted as follows:  A  sheet of writing paper of a
firm texture is brushed over on one side with a solution of 50
grains of nitrate of silver in an ounce of water, and then dried
in a dark room, and subsequently soaked two or three minutes
in a solution of iodide of potassium, containing about an ounce
of the iodide to a pint of distilled water.  It is then to be again
soaked for some minutes in water, and thoroughly dried, and
preserved for use.
When required for use, the paper is to be washed on the side
previously iodized by gallo-nitrate of silver, prepared for the
occasion in the following manner: Dissolve 100 grains of nitrate
of silver in 2 ounces of distilled water, and add to it an equal
volume of strong acetic acid, and then mix with it several volumes
of saturated solution of gallic acid in cold distilled water.  This
last preparation should be made only in small quantity for the
particular occasion, as it spoils by keeping. The last washing
should be made in the dark, or with only a feeble candle light;
and the paper dried carefully, excluding the light of day, to the
action of which it is exceedingly sensitive.
Paper prepared in this way may be used in the manner first
described, or in the camera obscura, for the taking of portraits.
If the picture at first is not sufficiently distinct, it may be improved
by washing it again in the gallo-nitrate of silver.  Finally, it is
to be rendered permanent by washing it with solution of bromide
of potassiumn, or of common salt.
The picture thus formed is what is called a negative picturethat is, the light and shade are reversed, as compared with an
ordinary engraving; but a positive one may be formed from the
first by using it as an object for forming a second picture upon
another sheet of the same prepared paper.  For this purpose it is
QUESTIONs.-Describe Talbot's Calotype process.  What are neyative
and what positive pictures?




72           DECOMPOSITION  OF LIGHT.
placed with its face downward upon the prepared paper, and then
exposed to the direct rays of the sun, as directed above (75). The
new picture is to be rendered permanent in the same manner as
before.
Numerous other preparations are in use for producing pictures upon
paper, but none of them equal in sensitiveness the one just described.
Though the materials to be used are different, as well as the processes,
yet the essential principles are the same in all. The light produces a
chemical change in the parts of the picture exposed to its influence, and
the picture is fixed by soaking the paper in a solution capable of dissolving out the sensitive substance contained in the parts which have not
undergone this change, in consequence of being in the shade.
Paper prepared for the taking of pictures is called photogenic pa~per,
and generally cannot be long kept, even in the dark.
76. The Daguerreotype process, so called from the name of the
inventor, is applied only to plates of silver, which are usually
spread upon plates of copper.  The silver surface is first very
thoroughly cleaned by washing with dilute nitric acid, and rub.
bing with leather or cotton and some polishing substance, as very
fine colcothar.  It is then to be subjected for a few minutes to the
action of vapor of iodine, by placing it in a box which has some
crystals of iodine spread upon the bottom; by this means, an
exceedingly thin coating of iodide of silver is formed upon the
surface of a straw-yellow  color, which is very sensitive to the
action of light.  It is then placed in a camera obscura, and the
image of any object in front is made to fall upon it for a few
moments, by which such a chemical change is produced in the
thin coating of iodide of silver, that subsequent exposure to the
vapor of mercury, at about 1650  F., brings out a beautiful picture
of the object.  By close inspection, it will be found that in the
parts of the picture where the most light has fallen such a change
has been produced that the mercury is capable of acting upon it,
but in other parts the bright surface of the silver remains unaffected; and further, the action of the mercury upon the silver
plate will be in proportion to the intensity of the light upon the
different parts.
Instead of pure iodine, the bromide or chloride of iodine may
be used for preparing the plates; but the last compound is said to
be, on the whole, much the best.
QUESTIONs.-How are pictures prepared in this way fixed or rendered
permanent?  76. Describe the Daguerreotype process.




DECOMPOSITION  OF LTIGHT.                         73
The picture, when taken from the mercurial process, is rendlered
permanent by removing the coating of iodide of silver, which is
readily done by merely pouring over it a warm solution of hyposulphite of soda or of common salt.
It is further improved, and the shades rendered deeper, by
heating upon it a solution of chloride of gold and hyposulphite
of soda.
The Daguerreotype process is very simple, but to insure success, close attention must be paid to various minute particulars,
which cannot here be discussed.
77. Thermography is a name which has been given to certain modes,
dependent, it is believed, upon heat, by which one body is made to depict
itself more or less minutely upon another, either in contact with it or in
its vicinity. Thus, if we write with some soft substance upon glass, and
then breathe upon it, the writing becomes visible. So if we allow a piece
of coin to lie for a time on a plate of metal or glass, and then breathe
upon it, an image of the coin will be produced. If while the piece of coin
lies upon the metallic plate it is gently heated by a spirit-lamp, and when
cold exposed to the vapor of mercury, a very distinct image of the coin
will be formed. In some cases, we are told, this effect will be produced
when the coin has not touched the plate, but only remained for a time
near it.
78. Double PRefraction of light takes place when a ray is passed
through certain transparent crystals, and some organized substances, so that objects seen through them  in particular directions
appear double; and the rays emerging from  them  are found to
have undergone a further change, by which they have acquired
peculiar properties on different sides, and are said to be polcriized.
Light is also polarized by other means, as by reflection at particular
angles from most non-metallic substances, and by refraction.  For'
a very full discussion of the subject, see Natural Philosophly,
page 259.
Rays of heat may be polarized in the same manner and by the
same means as those of light.
QvuESTIONs.-77. What is thliermography?  78. When is light said to be
doubly refracted.
7




74            NATURE  OF ELECTRIOITYo
III. ELECTRICITY.
NATURE  OF  ELECTRICITY.-ELECTRICAL
THE O R I ES.
79. Nature of Electricity.-As in the cases of heat and light,
we know nothing of the real nature of electricity, all our knowledge on the subject being limited to its effects.
Like heat and light, it is imponderable; no accumulation of it
in any substance adds to the weight of that substance, even when
tried by the most delicate balances; but many of its effects are so
like those of a mechanical agent, that it is usually considered a
separate material substance.
When certain substances, such as amber, glass, sealing-wax,
and sulphur, are rubbed with dry silk or cloth, they are found to
have acquired a property, not observable in their ordinary state,
of causing contiguous light bodies to move towards them; or, if
the substances so rubbed be light and freely suspended, they will
move towards contiguous bodies.  After a while this curious phbnomenon ceases; but it may be renewed an indefinite number of
times by friction.  This property was first noticed in amber; and
therefore the principle thus developed was called electricity (fromn
the Greek, electron, amber).
When a substance, by friction or other means, has acquired the
property just stated, it is said to be electrified, or to be electrica7ly
excited; and its motion towards other bodies, or of other bodies
towards it, is ascribed to a force called electric attraction.  But its
influence, on examination, will be found to be not merely attractive;
on the contrary, light substances, after touching the electrified body,
will be disposed to recede from it just as actively as they approached
it before contact.  This is termed electric repulsion.
80, Theories of Electricity. —In the absence of positive knowIdge in regard to the nature of this agent, two theories have been,jsecld, to account for and connect together the established facts..,...lu~s. —79. Do we understand the real nature of electricity?  Is
it Imiponderable?  What is the derivation of the term electricity.?   Whlen
is a substance said to be excited or electrified?




ELECTRICAL  THIEORIES.                         75
D tufly's th/.eory (from the name of its proposer) supposes that
every substance, in its natural state, contains in itself two highly
subtile and elastic fluids, in such a state of combination that their
presence is entirely disguised; but that the various phenomena
of electrical excitement are produced by one or the other of them,
accumulated in a body in excess.  The particles of each fluid are
supposed to have a strong attraction for those of the opposite kinld,
and for other matter, but are highly repulsive of each other.
These fluids are supposed to be separated by the various modes
of producing electrical excitement, to be hereafter described; and
one of them  being collected in excess in a body, as just stated,
produces the phenomena witnessed.
In most cases, when glass or any other vitreous substance is
rubbed, the electricity which is collected is the reverse of that
obtained when sealing-wax is subjected to friction; and hence the
former is called vitreous, and the latter resinous electricity.
Franklin,'s theory of electricity supposes that all bodies, in their
natural state, contain in their substance a certain quantity, called
their natural shcare, of a single, subtile, elastic fluid, which produces no sensible effects; but that the phenomena of electrical
excitement are produced when the body is made to contain either
less or more than its natural share.  It supposes that the particles
of this fluid repel each other strongly, but are attracted by all
other matter.  When a body contains more than its natural share,
it is said to be positively electrified; and negatively electrified,
when it contains less.
Glass and other vitreous substances, when rubbed, are supposed
to talke more than their natural share of the fluid, or become
positive; while resinous  substances, in the same circumstances,
lose a r ortion of their natural electricity, or become tegative.
These states are often indicated by the algebraic signs ~- and -,
The terms vitreous and positive, of the two theories, are theresynonymous, as are also the terms resinous and negative.
Either of these theories is found to answer well in explaining
most of the phenomena of electricity, but that of Dufay is geneQUESTIONS. - 800.Describe D)ufay's theory of electricity.  Descrtibe
F'.nklin's theory. What termuswere proposed by himl?  What terms of
tO  two theories are synonymous?




76        DISTRIBU% TION  OF ELECTRICITY.
rally preferred; though the terms positive and negative, of Franklin's theory, are almost universally used.
1From the above it will readily be seen, that when two bodies
are either positively or negatively electrified, they repel each
other, but attract each other when one is positive and the other
negative.
81. Electrometers.-Electrometers are instruments for indicating the presence of electricity, or its intensity. A pith-ball, suspended by a dry silk thread from any convenient support, answers
the purpose quite well; but the following, called the
gold-leaf electrometer, is a more sensitive instrument.
It consists of two slips of gold-leaf, suspended in a
cylindrical glass vessel, from  a metallic plate at the
top.  If the bottom is also made of metal, its sensitiveness will be increased.  When an excited body is
brought near the metallic plate, the leaves at once
diverge, in consequence of their being brought;nto
the same state, whether positive or negative, by the
inductive influence of the excited body, in a manner
to be hereafter explained.
DISTRIBUTION  OF ELECTRICITY.
82. Conduction of Electricity. — Some substances allow the
electric fluids to pass over them freely, and are therefore called
conductors; while others, that do not possess this property, or
only imperfectly, are called nonl-conductors.  If electricity be imparted to one end of a conductor, such as a copper wire, the other
extremity of which touches the ground, or is held by a person
standing on the ground, the electricity will pass along its whole
length and escape in an instant, though the wire were several
miles long; whereas excited glass and resin, which are non-conductors, may be freely handled without losing any electricity
except at the parts actually touched.
QUESTIONS. - Which of these theories is now generally preferred?
When do bodies attract and when repel each other?  81. What are
"lectromelers? Describe the gold-leaf electrometer. 82. What is said of
the conduction of electricity? What are conductors and non-condulctors?




D ISTR IBUTION  OF ELECTRICITY.                       77
To the class of conductors belong the metals, charcoal, plum]tago, water, and aqueous solutions, and substances generally
which are moist, or contain water in its liquid state, such  as
animals and plants, and the surface of the earth.  These, however, differ in their conducting power.  Of the metals, silver and
copper are found to be the best conductors; and after these follow
gold, zinc, platinum, iron, tin, lead, antimony, and  bismuth
Aqueous solutions of acids and salts conduct much better than
pure water.
To the list of non-conductors belong glass, resins, sulphur,
diamond, dried wood, precious stones, earth, and most rocks when
quite dry, silk, hair, and wool.  Air and gases in general are
lnon-conductors if dry, but act as conductors when saturated with
moisture.
It is not, however, to be understood that any very definite line can be
drawn between the two classes of conductors and non-conductors; but
there seems to be a very regular gradation from the most perfect conductor to the most imperfect, or most perfect non-conductor.  This
division of substances is, however, found very convenient, though in some
instances individuals might differ with regard to the class to which a
particular substance should be assigned.
83. Insulation.-When a conductor is supported upon a nonconducting substance, it is said to be ilsulated, and electricity
may be retained upon it for a time; but even then it wvill be
gradually diffused and disappear.  This is occasioned in part by
the conducting power of the air, which is considerable, except
when it is very dry.  In damp weather, many electrical experinients cannot well be performed, because of the rapid diffusion of
the fluid through the air, and the deposition of moisture upon the
surfaces of insulators.
When two substances are rubbed together, both electricities are
always developed, one of them going to one of the substances, and
the other to the other substance; and both electricities may be
retained, if the two substances rubbed together are insulated.
QUESTIONS.-What substances are classed with conductors, and what
with non-conductors? Can any definite line be drawn between the conductors and non-conductors?  83. When is a body said to be insulated?
Why do electrical experiments often fail in damp weather?  Are both
electricities always developed by friction?
7*




78        DISTRIBUTION  OF E LECTRICI  Y.
84. Induction of Electricity. - An electrified  body always
exerts a peculiar influence on the natural electricity of other
bodies in its vicinity, called induction, the nature of which will
be seen from the following explanation:  Let A be a positively
excited glass tube, held near one end
-H-   nB            /    of an insulated conductor, B, supposed
________ __  to be in its natural state; the natural
electricity in B will instantly be dis
turbed, and, on examination, it will be
found that the end next the excited
glass is negatively electrified, and the
other end positively, as shown by the
algebraic signs. If, instead of the glass
tube, some other substance, negatively
electrified, had been used, the electricities of the two ends of the conductor B would have been
reversed.  In every case, the part of the conductor next to the
excited body will be in the opposite state of excitement, while the
other end will be in the same state as the excited body.
In the experiment nothing but air is supposed to be between the
excited body A, and the conductor B, but the inductive influence
is exerted through all non-conductors. Thus, if a clean and dry
pane of glass be held between A and B, the result will be the salme.
Let A and B, in the next figure, be two
metallic discs, supported upon pillars of
glass, their edges being towards the eye,
Al          -- and let a spark of positive electricity be
communicated to one of them, as A; —it
will immediately act by induction upon
the natural electricity of B, causing the
side next to A to be negative and the
other to be positive.  The effect is precisely the same as in the preceding
experiment, but the form  of the conInduction of Electricity.  ductors different.  If now we touch the
QuEsTrioNs. 84. What is meant by induction?  Explain the experiment dcleseibed in this paragraph. Explain the experiment described in
connection with the next figure.




)DISTRIBUTION  OF ELECTRICITY.                       79
back of B with the finger, the positive fluid escapes, and the whole
disc becomes negative.  The action of the positive body, A, has
taken place through the stratum of intervening air; and any other
non-conductor may be substituted for it.  If, for instance, a plate
of glass be interposed, the two plates may then be brought much
nearer together, and the same results will follow.  Instead of
the metallic discs, we may simply apply a metallic coating to
the two sides of a pane of glass; which, if the coating do not
reach within one or two inches of the edge, serves as a sufficient
insulator.
85. The Leyden Jar —The Leyden jar receives its name from
the city of Leyden, in Holland, where it was invented.   It is
essentially the same thing as just described, except that a glass
jar is substituted in the place of the pane.  It consists of a glass
jar, coated both inside and outside with tin-foil,
except a part around the top, as shown in the
figure.  Through a varnished wooden cover, A,
a wire, having a knob at top, is passed, and a
chain, B, extends to the inside coating.  Now,           B
when either positive or negative electricity is
coammunicated to the knob at the top, it is im-  I   l
mediately diffused over the whole inside coating; 
and by its inductive influence, the outside coat-        I
ing takes on the opposite kind.  When in this
Leyden Jar.
state,-the two coatings being oppositely electrified,-the jar is said to be charged; and a discharge takes
place when a communication is established between the knob and
the outside coating, the equilibrium being restored with a bright
flash of light and a sharp report.  As the human system is a good
conductor, this discharge may take place through it, by grasping
the outside coating with one hand, and touching the knob at the
top with the other; or several persons may form a line by grasping hands, the one at one extreme touching the outside coating,
while the one at the other extreme touches the knob.  All will feel
the shock, as it is called, at the same instant.
While the jar is receiving the charge, it must not be insulated,
that is, the outside must communicate with the earth.  As the
QUESTIONS.-85. Why is the Leyden jar so called?  Describe its con.
struction and use. How is the shock produced in the system?




80        DISTRIBUTION  OF ELECTRICITY.
positive fluid collects on the inside, the outside becomes negative
by the expulsion of the positive fluid naturally in it, and the
accumulation of the negative fluid in its stead, drawn from  the
earth.  But if the outside is insulated these transfers to and from
it cannot take place, and therefore the jar cannot become charged.
86. Free Electricity resides in the Surface of Bodies. —It has
been demonstrated that the electricity of an excited body resides
entirely upon its surface.  Let A be a sphere of metal, suspended
by a silk thread, and excited by receiving a spark of electricity;
and let BB be two covers of paper, gilt outside and inside, and
held by glass handles.  Let them  now be applied to the excited
globe, and then instantly removed; it will be found that the
electricity has been entirely removed firom the ball to the covers.
Resides upon the Surface.
The fiee electricity therefore was entirely accumulated upon the
surface of the ball.
87. Distribution over Surface.-The fluid will be distributed
over the surface of an excited conductor, in
a mode dependent upon  its form; —if  it
be a perfect sphere, the fluid will be distributed equally over every part, but if it
be more or less elongated, as in the prolate
spheroid, the fluid accumulates in the ends,
where the intensity is greatly increased if the
spheroid  happens  to be very considerably
Distributioenon Ellipsoid. elongated.
QUESTIONS.-While receiving the charge must the jar be insulated?
Why?  86. In what part of an excited conductor does the electricity
reside?  87. In what manner is electricity diffused over the surface of a
sphere?  How is it dciffused over the prolate spheroid?




SOURCES  OF ELECTRICITY.                         81
If the extremity of the conductor is carried out to a point, the
fluid at once escapes from it, and all excitement disappears, even
though it remains insulated.  In the same manner, a sharp point
projecting from a conductor receives the fluid silently upon it, and
the body becomes excited.  The effect of points in discharging or
receiving either of the fluids is therefore apparent; and the circum.
stance must always be particularly regarded in the construction of
electrical apparatus.
The escape of positive electricity from a point in a
dark room is always attended by the appearance of a
faint blue light in the form of a brush, as represented
in A, but the escape of the negative fluid, in the same
circumstances, presents the appearance of a star, as
shown in B.
It is to be noticed, that in such experiments the
escape of either fluid is to be considered as precisely   Electricity
equivalent to the entrance of the other.
SOURCES OF ELECTRICITY.
88. As we have seen above, electricity is believed to be contained in all bodies, which are therefore properly its sources; but
the earth, as being by far the largest mass to which we have
access, is its chief source.  WVe propose, however, under this
head, to speak of the different modes of exciting or collecting it,
which are frict'ion, change of temperature, and chemical action.
89. Friction. —It is believed that electricity is always developed
when one substance is rubbed against another, one of the fluids
passing to one of the substances, and the other to the other substance, as before stated; but, in most cases, neither of the fluids
is retained, because the rubbing substances are not insulated.  If
QUESTIONS.-What is the effect if one part of an insulated conductor
is extended out to a point?  What is said of the influence of points in
receiving the fluid?  88. What is the great source of electricity?  What
are the different modes of exciting electricity? 89. Is electricity always
developed when one substance is rubbed against another?  How may
both be collected and retained?




82            SOURCES OF ELE(CTRICITY.
both be insulated, both the positive and negative fluids may be
retained (83).
90. The eiectrical qnachine is an instrument for developing
electricity by friction more abundantly than it can be done by
the simple means heretofore pointed out,
though most of the great principles of the
science, as we have seen, may be demonstrated without it.  The figure in the margin
R~ " "f7/.    /  c  represents the cylinder machine in its usual
form.  A is a cylinder of glass, firmly sup- __  ported, and capable of being turned on its
axis by a handle; and R  is a conductor,
-   supported on a pillar, having the  rubber
attached to it, with a flap of silk, S, extending nearly over the cylinder.  C  is made
of sheet-brass, and is called the prime conElectrical Iachine.    ductor, because it receives the electricity
from the cylinder as it is turned, by means
of several pointed wires (87), extending inwards towards the
cylinder.  It is supported upon a pillar of glass.
Now, when the cylinder is turned, electricity is abundantly
developed by the friction of the rubber against its surface, and is
received by the prime conductor, in which it accumulates. The
use of the flap of silk, 8, is to prevent the fluid from escaping in
the air) as the cylinder is turned.
From  the principles heretofore discussed, the learner will readily
perceive that it is the positive electricity that will be accumulated
in the prime conductor; but the negative (83) will also at the
same time accumulate in the rubber, if it be insulated.  But no
considerable quantity of electricity can usually be collected, unless
the rubber communicates with the earth, or, which is the same
thing, with the floor of the room.
An elegant plate electrical machine is represented in the next figure
(p. 83). AB is a firm base of wood, mounted on castors, so as to allow
the machine to be moved around easily upon the floor; C C C the prime
conduct.r, supported upon pillars of glass; P P two circular plates of
QUESTIONS.-90. Describe the electrical machine.  Describe the large
plate machine.




SOURCES  OF ELECTRICITY.                          83
glass upon the same axis, and turned by the handle H; R IRt  R  the
rubbers, of which there are eight, and F F flaps of silk to prevent the
MUMF.ORD So.
Electrical Machine.
escape f the fluid before reaching the point from the prime conductor.
This m i-hine, when put in proper order, developes electricity rapidly, and
is decide dly preferable to the cylinder machine.
When used, the machine should be dry and warm, and perfectly clean and free from dust.  Its action is also greatly increased
by spreading the surface of the rubber, where it presses against
the cylinder, with a soft amalgam of zinc, tin, and mercury, or
with the yellow sulphide of tin, called aurztm musivumn, the latter,
on the whole, being preferable.
QUESTION.-What is the substance spread over the rubber?




84             SOURCES  OF ELECTRICITY.
To prepare the amalgam, melt in a crucible three parts of zinc and
one of tin, and, after removing it from the fire, add four or five plrts of,ercury. Stir the mass with a stick a few seconds, and pour it out
upon a clear marble slab, or plate of metal, and allow it to remain
several hours before breaking it up. When wanted for use, grind it as
fine as possible in a mortar, and mix it with sufficient tallow to cause it
to adhere well to the rubber.  If the aurum musivumn is used, it is to be
mixed with tallow and spread upon the rubber in the same manner.
When the machine operates properly, if the knuckle be presented near the prime conductor, a vivid spark passes between
them, and a slight stinging sensation is felt; the same thing also
takes place on presenting the knuckle to the rubber, provided it
be insulated.  In the first case the effect is produced by accumulated positive electricity; in the second, by the negative.
91. Thle Eiectrophorus (from  electron and pherlo, I bear) is an
instrument for readily obtaining small quantities of electricity.
It consists of a plate of resin, A, about
12 inches in diameter, contained in a
shallow  dish of metal, and a metallic
disc, D, a little smaller than the plate
of resin, provided with a glass handle,
A     D         ~ q n F=   91 for removing it from  the resin at pleasure.  To operate well, the surface of
the resin should be perfectly smooth.
To charge the electrephorus, the disc
is removed, and the surface of the resin rubbed briskly with a
piece of warm, dry flannel, or struck several times with a dry silk
handkerchief, folded up for the purpose, by which a negative
electricity is excited.  If, now, the disc of metal be restored by
means of its insulating handle, its lower surface will become positive by induction (84), and its upper surface negative.   By
touching the upper surface of the disc, when in this position, with
the finger, the negative electricity will be discharged; and if it be
then removed carefully by its handle, it will be found highly
charged with positive electricity, so that a considerable spark may
be obtained from it.  As the cake of resin has lost nothing of its
electricity by the operation, the process may be repeated any
number of times, with the same result.
QUESTIONS.-lHow  may a spark be obtained from  the macthie' 
91. Describe the electrophorus.




SOURCES  OF ELECTRICITY.                       85
The Ilfyrdo-Electric Machine is an instrument for exciting electricity by means of high-pressure steam.  The excitement is attributed to the friction of the steam, carrying with it drops of water,
against the pipes from which it issues.
92. Atmospheric Electricity.-The  general phenomena of
thunder and lightning are well known. They are occasioned, as
Franklin first demonstrated, about a century ago, by immense
accumulations of electricity in the clouds, between which and
objects upon the earth violent discharges are frequently taking
place.  The discharge is believed to differ in nothing from  the
discharge of a,spark from the conductor of an electrical machine,
except what necessarily results from the'quantity and intensity of
the fluid accumulated.
L-ghtning-roods, which are so common at the present day, are
rods of metal erected upon buildings, extending a distance above
them at the top, and at the bottom connecting with the moist
earth. Being made of metal, which is a good conducting material,
any discharge that may happen upon the building will be conveyed by them without danger to the ground.
Often several of them are attached to the same building, at different points, but they should always be connected together, and
also make two connections, at least, with the moist earth.  Any
attempts to insulate the rod from the building are, to say the
least, useless.  Buildings with tin or copper roofs, and metallic
water-conductors extending downward, require special electrical
oonductors only for the chimneys or other projecting parts, and
also from the water-conductors to the moist earth below.
Electricity excited by friction is frequently called statical electricity, to distinguish it from  (dynamic electricity, which will be
hereafter described, under the head of Galvanism.
93. Thermo -Electricity.-  If a crystal of tourmaline, the
extremities of which are dissimilar, is slightly heated in the
flame of a spirit-lamp, one end will be found, on examination by
a delicate electrometer, to be positive, and the other negative;
QUESTIoNs.-What is the hydro-electric machine?  92. What is said
of lightning and thunder?  Who first explained their cause?  What are
lightning-rods?. What is said of buildings with metallic roofs? 93. How
may crystals sometimes be electrically excited?
8




86            SOUIRCES OF E  ECTRICITY.
but the excitement is very feeble.  Crystals of some other substances may be excited in the same manner.
But the more common method of exciting electricity by change
of temperature, is to heat slightly the ends of two or more small
rods of different metals at their junction, as represented in the figure.  Let A  be a small rod of
antimony, and B  another of bismuth, soldered
together at one end; and then let the heat of a
spirit-lamp be applied, for a moment, at the point
where they are soldered; while the bars are warmi'~   ing, the bismuth will be negative, and the antimony
positive.  The bismuth is called the positive, and
Thermo-Electricity.
the antimony the negative metal, because, while
heating, the positive fluid appears to originate in the former, and
flow to the latter; but an electrometer will show the different
states of the metals, as above indicated.
Other metals-and even non-metallic substances —-may be used,
with similar results.  German silver and brass answer very well,
the former corresponding in its action with the antimony, and the
latter with the bismuth.
The effect will be considerably increased, if several pairs of thle
metals, arranged as above, are associated together, as shown in
the accompanying figure, the alternate
rods, A, being of German silver, and
the intermediate ones, B, of brass,
When the metals are gently heated
__ _ -c   /        at the points of junction at one extremity of the bars, and kept cool at
the other, the terminal bars become
excited, and a constant current flows over any conducting substance, as a copper wire, connecting the extremities of the series.
If the upper ends of the rods be heated, the direction of the current over the wire will be as shown by the arrow. If the lower
ends be heated, or the upper ends cooled, its direction will be
reversed.
QUEssTIoNs.-Describe the mode with two metals. How may the effect
be increased?




SOURCES  OF:ELECTRICITY.                       87
To render the instrument more compact, the metallic bars may
be placed side by side, i'ith only a slip of silk  
between them, the ends being bent a little, so
as to admit of being soldered as before.  Such
an instrument constitutes the thermo-eiectric           li
pi/e, which is figured in the margin, P and N:!I
being the positive and negative poles.                    --
The existence and direction of these cur-   Thermo-Electric Pile.
rents are best shown by a delicate galvanomreter; an instrument to
be hereafter described.
By reversing the experiment, and passing a current of electricity
through the series of bars, they will be heated or cooled, according
to the direction in which the current is made to pass.
94. Chemical Action.-Chemical action, as the solution of a
metal in an acid, and the combustion of charcoal in an ordinary
fire, it is believed, is always attended by the development of electricity. In the combustion of charcoal, the gas arising from the
coal is positive, while the coal itself, if insulated, is negative; and
when a metal is dissolved in an acid, a current of positive electricity
always passes from the metal to the liquid, and any conducting
substance, as a plate of copper, contained in it.
Let Z be a zinc plate immersed in water,
acidulated with a little sulphuric acid, contained in a,ass vessel, and C a plate of
copper, also i;imersed in the same liquid;
the zinc will be gradually corroded, and a
current of positive electricity pass from  it      Simple Circuit.
through the liquid to the copper; and if
the plates are connected by a wire, the current will pass over it in
the direction indicated by the arrows.
But, although we have, in these and other cases of chemical
action, such decided and even powerful developments of electricity,
it is admitted, that in very many cases where chemical action really
takes place, no indications of electricity have as yet been observed.
The action of one salt upon another, of one metal upon another, or
QUEsTIONS.-Describe the thermo-electric pile.  94. Is chemical action
always attended by the development of electricity?  Describe the simple
gatlvanic circle. Are indications of electrical excitement always observed
during chemical action?




88                      GALVANISM.
of' a simple element, as oxygen or sulphur, upon a metal, may be
mentioned, as instances in which no electrical excitement is actually
known to take place.
The electricity of chemical action, sometimes called c7ynamicai
electricity (92), properly constitutes the subdivision of the general
subject of electricity called GALVANISMI; and under this title it
will be discussed more at length, as it is this branch of the general
subject which more especially concerns the student of chemistry.
GALVANISM.
95. The science of Galvanism owes its name and origin to the
experiments on animal irritability made by Galvani, professor of
anatomy at Bologna, Italy, in the year 1790.  In the course of
some of his investigations, he discovered the fact that muscular
contractions are excited in the leg of a frog recently killed, when
two metals, such as zinc and silver, one of which touches the
crural nerve, and the other the muscles to which it is distributed,
are brought into contact with one another.
The experiment with the legs of a recently killed
frog is easily repeated, in the following manner:After killing the frog, immediately separate the
hind-legs, with a small portion of Dte spine, and
S  remove the skin; then bind around the part of the
spine removed with the legs a piece of tin.foil, F,
and, holding it up with the left hand, apply a piece
of silver coin, or a rod of silver, S, bent, if necessary, so that it shall touch the tin-foil and the flesh
of one of the legs at the same time.  At each contact of the metals, the muscles of the leg will be
K   ) /  1    violently contracted, and jerking of the legs pro-'x n withduced.  The experiment succeeds best when the
Experiment with
Frog.     whole is kept wet with clean water.  The irritaQUESTIONS.-By what name is the electricity of chemical action generally known?  95. What was the discovery of Galvani?  Describe the
experiment with the legs of the frog.




G A L V A N I S                         89
pility of the muscles will gradually subside, but sometimes it will
continue more than an hour after the death of the animal.
The large legs of some insects, especially those of the grasshopper,
may be used for the same purpose.  It
is necessary only to remove with a sharp              A
penknife a portion of the skin from each                         B
side of the thick part of one of the leaping legs, so as to expose the flesh; then
by laying the under side of the leg upon     c
a small piece of moistened zinc, Z, and    Z
bringing a piece of copper, C, in contact    Experiment with Grasshopper.
with the flesh exposed on the upper side,
no motions will be observed until the copper also touches the zinc, when
quick movements or jerks of the lower part of the leg, A B, will be seen,
each time the contact is made.
96. Simple Galvanic Circles.-A  simple galvanic circle is
formed of three substances, two of which are usually metals,
and the third a liquid, as a dilute acid.  The arrangement described in paragraph 94 constitutes such a circle.  The zinc is
acted upon by the acid, and the electrical disturbance takes place
over all that part of its surface covered with the liquid; and a
current of positive electricity flows to the liquid.  If, now, a plate
of copper, or other metal not capable of being acted upon by the
liquid, be introduced, it will become positive by receiving electricity from  the liquid; and, by connecting the two plates by
wires, a constant current is established over these wires, as shown
by the arrows.  It matters not, so far as galvanic action is concerned, at what part the plates touch each other.  A current is
formed, whether contact between the plates is made below, where
covered with liquid, above, where uncovered, or along the whole
length of the plates, provided both plates are immersed in the
same vessel or diluted acid. But in every case a circuit must be
formed, around which the electricity may traverse, either in a
single current, or in many partial currents, into which it ma
divide itself, as will be the case when the metals are in contact
along their whole surfaces.  This last result it is desirable to
avoid; and therefore the metals are always to be kept separate
below the liquid, and above it also, except at the part where the
QuEsTIoNs.-Describe the experiment with the leg of a grasshopper.
96. What constitutes a simple galvanic circle?  When is the electricity
excited?  What is the use of the plate of copper?  In what direction
does the positive current flow? Must the circuit always be complete?
8*




030                     GALVANISM.
current is desired to pass.  Usually, a wire is connected with each
plate, which may be brought in contact or separated at pleasure.
WX/hen they are in contact, the circuit is said to be closed; when
they are separated, it is said to be broketn, or opena.
97. As the electricity is developed entirely by the chemical
action between the zinc plate and the acid, it is only upon the
surface of the zinc covered by the acid that the electric disturbanct
takes place; and, other things being equal, the quantity of elec.
tricity set in motion will be proportional to the extent of zinc surface
thus exposed to the acid.  And in
every case, in order to establish the
current, the circuit must be made
A?:,],~                 complete.  Thus, if we take two
m:.  /    cups of dilute acid, immersing in one
a copper, C, and in the other a zinc,
Z, plate, and connect the two by a
Circuit not Formed.
wire, as shown in the figure, though
some chemical action will take place, no current will be established,
for the reason that no circuit has been formed.  Chemical action
does indeed take place in the cup,A         -            containing the zinc plate, and its
electricity no doubt is disturbed;
but, still no current can be estam/ I'i   blished.  For this it is necessary,
further, to add the conducting wire
UK,     ~'~ ~ii'l  AB, as shown in the next figure;:_!.the direction of the current will
=_8_ t~          then be as shown by the arrows.
It is to be understood that here,
Circuit Complete.
as elsewhere, in using this ]anguage, we have reference to the positive fluid; but in reality there
is just as much reason to believe there is also at the same time a
QUESTIONs.-When is the circuit said to be closed?  When open?
97. To what will the quantity of fluid put in motion be proportional?
Explain the necessity of completing the circuit, as illustrated by the
figures in this paragraph.




GALVANISM.                             91
negative current established in the opposite direction.  In every
case, the direction of the positive current will be fromv the metal
acted upon to the liquid, and that of the negative, of course, the
reverse.  The direction of the positive current, therefore, in the
apparatus last figured, is from the zinc cell to the copper cell, over
the wire connecting the cells, and from the copper to the zinc over
the wire connecting the plates, as shown in both cases by the arrows.
To break the circuit it matters not which of these wires is inter
rupted; both are equally necessary to complete the circuit.
08, A simple galvanic circle may be formed of one metal and two liquids,
provided the liquids are such that a stronger chemical action is induced on
oue side than on the other. Nay, even a plate of metal, with two portions
of the same liquid, may be made to constitute the simple circuit, provided
only the conditions are such that one side of the metal shall be acted upon
by the liquid more readily than the other. This will be effected, if one
portion of the liquid is warmer or stronger than the other, or if one surfa.ce of the metal is rough and the other polished.
Ae have above represented the positive current as passing from the
zinc, through the liquid, to the copper, and in the opposite direction over
the wires connecting the plates above the liquid; this will always take
place when a diluted acid is used, which attacks the zinc more violently
tlhan it does the copper; but if a solution of ammonia be substituted for
the acid, the copper will be most acted upon, and the current will move
in the opposite direction.
It is not necessary that copper and zinc alone should always be
used in these experimendt; other metals may be adopted, with
equal, and, in some cases, with even more decisive resul'ts.  Nor
is it required that the liquid should always contain an acid; other
substances, as solutions of the salts, are often very efficacious in
exciting this subtile fluid.  The conditions required are, that the
metals and liquid used should be such that chemical action will
take place more readily between one of them and the liquid than
between the other and the liquid; and that metal is always found
pnsitive (below the surface of the liquid) which is most acted upon
by it.  Other things being equal, the galvanic action will be more
intense, the greater the difference between the the two metals
QUESTIONS.-IS there a current of the negative fluid?  What is its
direction as compared with that of the positive?  98. How may a simple
circle be formed of a single metal and two liquids? Will the positive current
tlways pass from the zinc to the copper? Why is the direction reversed
when aqua ammonia is used?  lMay other metals besides copper and
zinc be used? What are the conditions required?




-0 2                    GAGALVANISM.
used, as regards their tendency to be acted on by the particular
mnenstruuln in which they are immersed.
Besides the above arrangement, there are several modifications
of the simple galvanic circle, each possessing its own peculiar
advantages, which will be described hereafter.
99. Compound Galvanic Circles.-Galvanic Batteries.-The
compound galvanic circle, or galvanic battery, consists of a number of simple circles, so arranged in a series, that the copper of
each simple circle is connected with the zinc of the one adjacent.
One extreme of the series, it will be evident, will be copper, and
the other zinc; they are often called the poles of the battery, the
former being positive and the latter negative.
The voltaic pile (from the name of its inventor) deserves here
to be noticed, as the earliest and simplest instruz    ment of this kind, though by no means the most
efficient.  It is formed of pieces of copper, c, zinc,
z, and cloth, the latter being moistened with a solution of salt or acidulated water.  Commencing with
either of the metals, upon this is placed a piece
of cloth, and then a piece of the other metal; the
1 ~   tthree, of course, constituting a simple galvanic
circle.  Upon this circle other simple circles are
Z   then formed in the same manner, care being taken
to place the metals throughout the series in the
Voltaic Pile.   same order.
same order.
The series may be extended indefinitely; but, usually, from
fifty to one hundred pairs of metallic plates will be found as many
as can be employed advantageously.  When in action, the extreme
zinc plate, which is represented as uppermost in the figure, will
be negative, and the extreme copper plate positive; and if they
be -onnected by wires, the current will flow in the direction of
the arrows, both through the series, and over the wires.  The
extremes of the series are called its poles, or electrodes (from
electron, and odos, a way).
QUESTIONS.-99. Whait constitutes the galvanic battery, or comnpotnd
circle?  What constitutes the poles of the arrangement?  Describe the
voltaic pile:  HIow many pairs of plates are needed? What are the poles,
or electrodes?




GALVA NISM.                         93
The voltaic pile is now rarely employed, because we possess
other modes of forming galvanic combinations which are far more
powerful and convenient. Cruickshank's battery, one of the earliest
invented, consists of a trough
of baked  wood, about thirty.            /.          )
inches long~ in which are placed,   ~      "~'  /,.
at equal distances, fifty pairs of
zinc and  copper plates, previously soldered together, and
so arranged that the same metal
shall always be on the same side.  Each pair is fixed in a groove
cut in the sides and bottom of the box, the points of junction
being made water-tight by cement.  The apparatus thus constructed is always ready for use, and is brought into action by
filling the cells left between the pairs of plates with some convenient solution, which serves the same purpose as the moistened
cloth in the pile of Volta.
An excellent compound circle, or battery, is formed by combining a number of cups like that
represented in paragraph 94.  Each
cup contains a zinc, Z, and copper         M    X    X
plate, C, the zinc of one cup being connected with the copper of the next,
through the whole series, leaving the
Compound Circuit.
two extreme plates free; and the cups
are filled with diluted acid, or a solution of salt.  The two free
plates, constituting the extremities of the series, will be the poles,
or electrodes; and when they are connected by wires, the current
will be established in the direction of the arrows.
By studying closely this arrangement, it will be seen that the
actual quantity of electricity flowing over the wires connecting the
electrodes, is no more than when a single cup only, with a single
pair of plates, is used.  The same electrical disturbance takes
place in each cup, over the whole surface of the zinc plate which
i.i covered with the liquid, the part of this plate aboeve the liquid
QUESTIoNs.-Describe the trough battery. What is said of the quantity
of electricity flowing in the compound circle, or battery? IHow does this
appear?




94                     GALVANIS M.
becoming negative, and the liquid becoming equally positive; the
copper plate then serves as a conductor to take up this positive
electricity, and convey it to the negative zinc of the next cup, by
which it will be exactly neutralized.  However extensive the
series may be, this will take place with every alternate zinc and
copper plate except the extreme ones; so that the quantity pass
ing over the wires connecting the electrodes, will be only that of
the single pair of plates constituting the extremes of the series.
100. But although the quantity of electricity developed at the
electrodes of the compound circle is no more than we should
obtain by using a single pair of plates, yet it will be found to
have acquired a very important property, called intensity.  By
this term is meant its power to overcome resistances which may
impede the passage of the current.  The current from a single
pair of plates, however large they may be, will always be exceedingly feeble, and will not flow unless the wires connected with
them are in actual contact; but, if the polar wires of the compound circle are once brought in contact, they may be separated
at a little distance, and the current will continue to pass between
them, with a brilliant flame.  The reason is, because the current
fr'om the compound circle possesses sufficient intensity to overcome
the resistance of the thin stratum of air between the wires, which
is not the case with the current of the simple circle.
So, if the polar wires of the simple circle are grasped, one in
each hand, by the operator, not the least sensation is felt, because
there is not sufficient intensity to impel the current through the
system, which is comparatively a poor conductor; but if the same
is done with the polar wires of the compound circle, especially if
the series be extensive, the moment the circuit is formed, a powerful shock is experienced, similar to that received from the Leyden jar.  This is owing to the increased intensity of the current
from the compound circle, enabling it to overcome the resistance
which is interposed.
QUESTIONS.-100. What benefit then is derived from increasing the
series?  What is meant by intensity?  Why will not any sensation be
produced in the system by a single cell?




GALVANISM.                            95
101. From the above facts we deduce this important practical
principle: that, to produce a current of quantity, a single pair
only of large plates is wanted; but to give inztensity, a number
of simple circles must be combined, in the manner described.
Compared with frictional or statical electricity, that of the most
powerful galvanic battery has always only a feeble intensity, but
the quantity is often immense.
The energy of any battery, whether composed of one or many simple
circles, will depend very much upon the nature of the liquid used. A
solution of common salt, sulphate of soda, nitrate of potassa, alum, or
other salt, will answer the purpose, but acids are better. Generally, one
of the stronger acids is used, diluted with 15 or 20 times its weight of
water. For ordinary purposes, a mixture of equal parts of nitric and
sulphuric acids, diluted with 20 times their weight of water, will be
found to answer well.
102. Nature of the Chemical Action in the Battery.-The
development'of electricity by the usual galvanic arrangements is
attributed chiefly, if not entirely, to the decomposition of water
in contact with the zinc plates.  Water is a compound of oxygen
and hydrogen, and is incapable of acting upon zinc, unless some
acid be also present.  But when a piece of this metal, in its usual
impure state, is immersed in diluted acid, the water is decomlposed, its oxygen combining with the zinc, forming oxide of zinc,
while the hydrogen rises in bubbles and escapes in the air, and at
the same time the oxide of zinc is taken up by the acid.  If, now,
a plate of copper is placed in the diluted acid at a little distance
from the zinc, and the two connected by a wire, constituting a
simple galvanic circle (97), the bubbles of hydrogen will not rise
around the zinc as before, but around the copper; showing that
the gas has in some way been transmitted through the liquid
between the plates, though not the least appearance of any motion
can be observed by the eye.  If the connecting wire is removed,
the evolution of hydrogen at the copper plate at once ceases with
the cessation of the electrical current, but continues to rise slowly
QUESTIONS.-101. What is said of the intensity of the excitement produced by the galvanic battery, as compared with that of statical electricity?
XWhat acids are recommended for use in the battery?  102. What is said
of the chemical action that takes place when a piece of zinc is imnmersecid
in a dilute acid?  What is the occasion of the bubbles upon the zinc?
When a copper plate is connected with the zinc where do the bubbles of
hydrogen make their appearance?




9G                      G ALV A NIS M.
around the zinc.  This latter effect, however, is occasioned by the
impurity of the zinc.  Thus it would seem that the development
of the current is occasioned entirely by the decomposition of the
water, and the formation of oxide of zinc.
When the battery is in active operation, though the hydrogen
is rapidly evolved at the copper plates, yet the whole surfaces of
these plates will be all the time covered with a film of this gas,
which interferes with its conducting power, and prevents the frec
passage of the current; at the same time, as a matter of course,
diminishing very considerably the energy of the battery.  T,
remedy this difficulty, several new forms of the battery have
recently been invented, which act with great energy, and will
here be briefly described.
103. Daniel's Constant Battery. —This excellent instrument
consists of a cylindrical vessel of copper, C, in
-  which is placed another smaller one, L, made of
~,,:;    unoiled leather, or unglazed  porcelain, through
Which water will gradually percolate; and in the
latter is contained a rod of zinc, Z, about an inch
in diameter.  To charge it, the inner porous vessel, which contains the rod of zinc, is filled with
H i I lldiluted sulphuric acid (acid 1 part, and water 8
parts), and the space around the inner vessel with
a saturated solution of blue vitriol, acidulated with
Daniel's. l   sulphuric acid.  To the side of the copper vessel,
and also to the zinc rod, wires are soldered, with
binding screws for holding the polar wires; the one connected
with the copper being positive, and the other negative, as shown
by the algebraic signs.
Usually, the zinc rod is amalgamated with mercury, which is
done by rubbing the surface with mercury, while covered with
some weak acid.  This renders the chemical action over the whole
surface more uniform, and the action of the battery more constant;
but thb same thing may be accomplished with less trouble, by
using the zinc in its ordinary state, and substituting, in the porous
QUmsTroNs.-103. Describe Daniel's b6altery. IIow is the zinc amral.
gamated?




GALVANISM.                              97
cell, a saturated solution of sulphate of soda (Glauber's salt), instead
of the diluted acid.
The above arrangement, it is plain, constitutes a simple galvanic
circle; and its action is particularly energetic and constant, in
consequence of the accumulation of hydrogen gas upon the copper
plate (102) being completely avoided.  This will appear from thJ
following explanation.
In this instrument, as in the more common one first described,
the electricity is developed at the surface of the zinc, by the decomposition of the water; the oxygen combining with the zinc, and
the hydrogen passing through the porous vessel into the vitriol
solution, and thence to the sides of the copper vessel, which constitutes the copper plate of the series (98).  Here the hydrogen
does not make its appearance in bubbles upon the surface of the
copper, as in the common arrangement, but enters into a new
combination with the oxygen of the oaide of copper deposited
from the vitriol solution.  Blue vitriol is a compound of sulphuric
acid and oxide of copper; and while the battery is in operation,
it is all the time decomposing, its acid passing into the porous
cup, to act upon the zinc, while the oxide of copper is itself also
decomposed, its oxygen combining with the hydrogen at the surface of the outer vessel, which receives a new coating of metallic
copper.
Any number of these arrangements may be united, by connecting the
zinc of one with the copper of the next, as heretofore described (99);
and a battery so constructed has this
great advantage, that no action takes
place when the circuit is not closed.    +       0
It is also very constant in its action,
affording a uniform current for seve-     i
ral hours in succession.
sents a battery of this hind, of six
series.                                        11
When a battery of this kind is to
be used some time, a quantity of undissolved blue vitriol should be kept       
in the upper part of the copper cell,        Daniel's Battery.
either upon a shelf provided for the
purpose, or in a muslin bag, to keep the solution constantly saturated
QUESTrION. —How is the hydrogen disposed of in this arrangement?
Why is it called a constant battery? How are the separate cells to be
united to form the compound arrangement?
(1




9Q                       C-'G A L V A N I S IS.
104. Grove's Cell,-This battery, invented by Professor Grove,
of London, is roemarkable, not only for the constancy of its action,
but also for its great intensity.
The constrllction of this battery is shown in the accompanying
figure.  A  glass or porcelain cup, of a proper
+  size, is used, and in it is placed a hollow cylinder,   l i.~t  llLof zinc Z, (usually having a slit in one side, to
il'~}q~,,~..allow a free passage to the liquid), and inside
of this, a small cylindrical cup, C, of porous or
i!,llI  unglazed porcelain.  The glass cup is then filled
1 I  i'!  with diluted sulphuric acid (of the same strength
as is used in Daniel's battery), and the porous
cup with strong aquafortis (nitric acid).  Lastly,
a thin slip of platinum, P, is suspended in the
aquafortis, and supported by a piece of wood
Grove's Cell.
attached to the side of the glass cup, through
which a wire passes, and is bent in the form represented in the
figure.  A  projection upward from  the zinc supports a binding
screw, shown on the right, and another is soldered to the wire to
which the platinum  is attached, shown at the left.  These, of
course, serve as the positive and negative poles of the circle; and
to them the polar wires may be attached, when required.
The zinc should be well amalgamated, as heretofore described.
The action of this battery is essentially the same as that of
Daniel's, except that the hydrogen fiom  the decomposition of the
water, passing into the porous cell, is expended in decomposing
the nitric acid, which, when the instrument is in action, gives
off copious nitrous fumes.  To understand this, it is necessary to
recollect that nitric acid is a compound of nitrogen and oxygen;
and the hydrogen entering the porous cell takes away a part of its
oxygen, forming water; and the binoxide of nitrogen which is
liberated rises, and uniting with more oxygen from the air, forms
i-he nitrous fumnes.',battery of' twelve series of Grove's arrangement is represented in
wie following igoire. The cups are contained in a box of wood, for the
sake of convenience in handling, and between the cups are partitions to
QuESTIro NS. —104. Describe Grove's cell. What in this case becomes of
the hydrogen?




G AL  AN IS I.                            99,olcld them more stleadily.  The hollow cylinders of zinc, when made for
this IpurIpose, are caIst with arms rising fiom one side, and then projeCti
+       -OI
L 11tT  211jig   lt4 2it{tj~511   a u  n t!;     |, 7
Grove's Battery.
ing a distance horizontally; and to the end the platinum  plate is firmly
soldered, so as to hang directly in the nitric acid cup of the next adjacent
series.  The whole, it will be observed, forms a connected series; and
the terminal zinc at one extremity, and the platinum at the other, with
each of which a binding screw is connected, constitute the negative and
positive poles.  The terminal platinum plate is supported in its place by
a wire passing through a piece of wood attached to the side of the box
or the cup, as represented in the figure.  When a greater power is
required than is afforded by a battery of this size, it is found more convenient to connect two or more batteries together than to have a larger
number united in one series.  The batteries are connected by extending
a wire from the positive pole of one to the negative of the next; they
then in reality become a single series.
This is the kind of battery generally used in working the magnetic
telegraph, as it excels all others in the constancy and intensity of its
action.
105. Smee's Cell.-This very efficient arrange- 
inent is represented in the figure in  the  margin.   Two plates of zinc, well  amalgamated,   c  V
are firmly held together against a piece of wood,             i.. 
W, by means of a brass clamrp and screw; and
between theui is a plate of silver S  the surfaceii i iii
of which  has been  coated  over with  metallic
platinum, in a state of fine powder, called platinum  black.  The zinc and silver plates are then          i
suspended in a glass vessel, the piece of wood              I
resting upon the top.   A  binding  screw, con-             T' mL II  K
stituting the +  pole, is connected  by a wire             Smee's Cell.
QUESTIONS.-What is said of the character of batteries of this kind''
05. Describe Soiee's arra,? einent.




100                      GALVANI S M.
(which is insulated from the brass clamp through which it passes)
with the silver plate, and another, constituting  the -  pole, is
soldered to the clamp which holds the zinc plates in their places.
The liquid used in the glass cup is sulphuric acid, diluted with
10 or 15 times its weight of water.
The peculiar advantage possessed by this form of the batter)
depends upon the rapid evolution of hydrogen from the platinized
silver plate.  We have seen above (102) that the accumulation of
this gas upon the smooth surface of the copper plate, in the old
arrangement, considerably retards the passage of the electric current, by preventing the liquid in a measure from coming in contact
with the plate; but this is avoided, in Smee's arrangement, by
the roughened surface  of the silver plate, produced by the platinum
deposit.
Compound circles or batteries are readily formed by combining the
simple series of Daniel with each other, or those of Smee with each other;
but the proper mode of doing it will be easily understood without further
illustrations. For many purposes, they answer well; but neither of them
possesses the energy of that of Grove above described.
As batteries are sometimes constructed, and as they are usually represented in books, the direction of the current appears to be the reverse
of that in the simple circuit, but this is in consequence of there being a
superfluous plate at each extremity which serves only as a conductor.
In the figures in this book, however, these superfluous plates are not
represented, and the remarks in the text are made with reference to
instruments of this construction.
106. Buansen's arrangement is constructed on the same principle as
Grove's, except that hollow cylinders of carbon surrounding the zinc,
are substituted instead of the platinum  plates.  The carbon cylinders
are made of carbon from gas-retorts, by grinding it to a powder, and
then kneading it with flour dough, and afterwards baking it in a strong
heat.
107. Ohm's.Formna. —The effective force of a battery of
any construction will depend upon a number of conditions, or
circumstances, which are well expressed in a formula devised by
Prof. Ohm, and therefore generally known by his name.
To estimate the effective force of any galvanic arrangement, two
things are to be considered, viz: 1. The electromotive force, or
absolute tension of the electric fluid, and 2. The resistance to be
overcome. As there must always be some resistance to the passage
QUESTION.-What is the peculiar advantage of Smee's arrangement?
1G06. Describe Bunsen's arrangement.  107. What is the design of OhnIl's
folrmla?  To estimate the effective force of a battery what two things
must be considered?




GALVANISM.                            101
of the fluid, the effective force must always be less than the full
electromotive power, if such resistance did not exist.  The resistance will be occasioned chiefly by the wires connecting the poles,
but something is due also to the liquid between the plates.
In the case of a single cell, let the absolute tension be represented by t, and let r be the resistance of the wire, and'" the
resistance of the liquid between the plates, and A the effective
force; then will A = -t".  That is, the effective power of the
cell will be directly proportional to the absolute tension of the
electric fluid, which will in general depend upon the activity of
the chemical action taking place, and inversely as the sum of the
resistances of the liquid between the plates, and that of the conducting wire.
To apply the same law in the case of a compound series or
battery, we have the following formula: A  -- ri t,  in which n is
used to represent the whole number of cells.  We see, therefore,
that the effective power will be directly proportional to the electromotive'force of each cell, multiplied by the number of cells,
tand inversely as the resistance, which is made up of the resistance
of the wire connecting the poles, and the resistance of the fluid
of the cells.
The resistance r will be proportional to the length of the wire
and inversely as the area of its section.  The resistance hr' will be
proportional to the thickness of the stratum of liquid, and inversely
as its conducting rower.
108. Animal:lectricity.-Several animals, as the g$yyznotus
electricus, which is found in the fresh waters of some parts of
South America, the siltrus electricus, found in some Aftrican
rivers, and the torpedo, a species of which has been taken, though
rarely, upon the sea-coast of IMassachusetts, possess the power of
giving strong shocks of electricity, by means of peculiar galvanic
arrangements with which nature has provided them.
The electrical apparatus of these animals is plainly connected
with the nervous system, and is perfectly under the animal's conQUESTIONS. —What resistance will there always be to the passage of
the current,?  ro what is the effective force of a battery proportional?
108. What anliuals are mentioned as possessing the power of giving shoclis
of electricity' Is their electrical apparatus under control of the will?
9*




102   EFFECTS  OF GALVANIC  ELECTRICITY.
trol.  It is made use of as a defence against enemies, and in
paralyzing other small fishes, which are immediately seized for
food.  The'shock given by some of these animals is very powerful.
EFFECTS OF GAL'VANIC ELECTRICITY.
109. Galvanic electricity, as we have seen, differs essentially
front ordinary, or statical electricity, in several important particulars, as its feeble intensity, its immense quantity, and its flowing
in a continuous current; and, as we should expect, there is a corresponding difference in the effects which these two kinds of
electricity are capable of producing.
In consequence of the feeble intensity of the most powerful
galvanic battery, it is quite incapable of producing many of the
more brilliant effects of the common electrical machine, but others
are produced not less important.  In fact, in the galvanic battery
the ordinary signs of electrical excitement are almost wholly wanting, plainly for the reason that these indications depend chiefly
upon intensity.  Thus, when the circuit of a powerful battery is
broken, that is, when the poles or electrodes are disconnected,
both of them give signs of electrical excitement, if examined by
the ordinary tests; one of them being positive, and the other
negative, as be-fore explained; but the indications are exceedingly
feeble.
A Leyden vial may also be charged by establishing a communication between one of its surfaces and one of the electrodes, while
the other surface is connected with the other electrode; but the
charge will always be slight.
Either of the electrodes will give a spark to a conductor presented to it, but it is shown best by bringing the two polar wires
in close proximity; and on establishing the communication between the electrodes by the hands, previously moistened, a
powerful shock is felt, precisely like that produced by  the
QuESTIONS.-109. In what respect does galvanic differ from statical
electricity?  In the charged galvanic battery, are the ordinary signs of
electrical excitement apparent?  May the Leyden vial be charged by an
active battery?  How may a spark be obtained from one of the electrotles?  How is the shock produced?




EFFECTS  OF GALVANIC  ELECTRICITY.  103
discharge of the Leyden jar.  But the shock is felt only at the
moment the current is established; if afterwards the hands be held
firmly in their places a peculiar feeling of numbness in the muscles
in the line of the current succeeds, and continues until the current
is again broken.
110. Heating Effects-Deflagration. —Wh en the communication between the electrodes of an active battery is established by
various substances capable of conducting the current, they often
become intensely heated, and sometimes even consumed or dissipated in vapor by the heat.  Thus a small wire interposed in the
circuit will become red-hot in an instant, and gold and silver leaf,
in the same circumstances, will take fire and burn with brilliant
scintillations.
This heating effect of the galvanic current may be produced at
a distance from the battery, and gun-powder or gun-cotton and
other combustibles ignited.  Let W  be two
copper wires, coated with tarred twine, so as
to insulate them  perfectly, having their ex- 
tremities connected by a very small platinum
wire soldered to theni, as shown through the
glass cup C.  Let the cup                         c
be now filled with gunpowder or gun-cotton, and the
other ends of the  wires
brought in contact with the         Gunpowder Exploded.
poles of the battery; immediately on the passage of the current,
the platinum wire will be heated, and the powder exploded.  The
wires, if well coated, may be extended under water, and. a submarine magazine exploded.  This method has been used for
exploding the powder in the blasting of rocks.
A mixture of oxygen and hydrogen may be inflamed in the
same manner; for this purpose the mixed gases are contained in
a pistol, into which the wires are inserted, as shown in the figure
on p. 104.
QUEsTIONs. -- Does the shock continue while the current flows?
110. How may the heating effects of the current be shown? How
m.ay gunpowder be inflamed?  Describe the method of exploding a
mixture of oxygen and hydrogen.




104   EFFECTS OF GALVANIC  ELECTRICITY.
Pistol,
When pieces of well-burnt charcoal are attached to the polar
wires, on bringing them near each other, a most brilliant arc of
flame appears between them, and the
points appear to be vividly ignited, as
Charcoal Points.     if heated by any other means.  But
the heating effect does not depend upon the combustion of the
coal, since it is equally as great when the charcoal points are
excluded from  the air.  To produce the effect, the
points must first be brought into contact, but they
may afterwards be separated some distance, and the
arc of flame will continue.  At the same time a portion of the carbon point in connection with the positive
pole disappears, and the other point is elongated as if
by matter transferred from the other side.  If the charcoal connected with the positive pole be hollowed out so
Metal ola- as to receive pieces of metal, as silver, gold, or platinum,
talizecl.   when the current passes the metals will not only be
fused, but appear to be even volatilized, and pass off in fumes.
111. Chemical Effects, Decomposition,-The chemical effects
of the galvanic current are seen chiefly in the decomposition of
compound substances, and in the operations of electro-imetallurgy,
soon to be explained. Thus, when two gold or platinum wires
QUESTIONS.-Describe the experiment with the charcoal points. I-low
nnay the metals, as gold and platinum, be even volatilized?  111. In
what are the chemical effects of galvanism chiefly seen?




EFFECTS OF GALVANIC ELECTRICITY.  105
arc connected with the opposite ends
of a battery, and their free extremities
are plunged into  the same cup of
water, but  without  touching  each
other, hydrogen gas is disengaged at            iv 
the negative, and oxygen at the positive
wire, these being, as we have seen
(102), the elements of water.  If the,
wires are brought into actual contact                    I
in the water the current is conducted
directly through without acting upon
the water, and if any other metal except
gold or platinum  is used for the positive pole, it will be rapidly attacked by
the liberated oxygen.                        1I            _  +
By using one or the other of the _              /   _,
two pieces of apparatus figured in the.....
margin, the oxygen and hydrogen may -           I
1_21  5.                    y 1Decomposition of Water.
be collected separately or together, as
may be desired.  The first -piece consists of an open vessel, with
a shelf and  support for two tubes,
N and P, which are closed at the top,
and binding screws marked + and- 
whibh connect with wires passing underneath  the edge of the glass, and
terminating in the mouths of the tubes.
After fillingt the tubes and inserting
them in their places,-the vessel being           _;_
previ4ously nearly filled with water, the
current from the battery is made to pass
through in the ordinary way.  Very
soon the gases will be seen to collect in                 -
the tubes; and as water contains by         Decomposition of Water.
volume twice as much hydrogen as oxygen, the tube N conQUESTIONS. —How may water be decomposed by the current? Describe
the apparatus for decomposing water and collecting the gases formed in
separate tubes. Describe that for collecting the gases together.




1003  EFFECTS OF GALVANIC ELECTRI CITY.
taininig it will be found to fill proportionably faster than the
other.
\Wbhen the two wires terminate in the same tube, the two gases
will be collected together; and by passing afterwards a spark of
common electricity through the mixture they will be again united,
with an explosion.
In decomposing water, it is well always to add a few drops of
oil of vitriol, to increase its conducting power.
If other compound bodies, such as some acids and solutions of
salts, are exposed to the action of galvanism, they are also decomposed, one of their elements appearing at one electrode, and the
other at the other.  An exact uniformity in the circumstances
attending the decomposition is also remarked.  Thus, in decoimposing water or other compounds, the same kind of body is always
disengaged at the same side of the battery. The metals, inflammable substances in general, the alkalies, earths, and the oxides
of the common metals, are found at the negative electrode; while
oxygen, chlorine, and the acids, go over to the positive electrode.
112. Those substances which appear at the positive side have
been called elctro-negative bodies, while those that are separated
at the negative wire are called electro-positive bodies.
The decomposition of a salt, which must be in solution, may be
shown in the following manner:-Let two wine-glasses be filled
with a solution of sulphate of soda, (which
v:;!  is a compound of sulphuric acid and soda,)
and let some fibres of moistened cotton be
extended between them, as shown in the
figure.  If the current is then transmitted
Decomposition of Salt. through the cups, the salt will soon, be
decomposed, and the cup in connection with the positive electrode
will be found to contain weak sulphuric acid, and that in connection with the negative electrode a solution of soda.  If, now,
a little red cabbage-water be poured into each, the acid liquid will
become red, and the soda solution green.
QUESTIONS.-May other compounds also be decomposed?  In decomposing a compound, will the same element always appear at the
same electrode?  112. What are electro-negative and electro-positive
substances?




EFFECTS OF GALVANIC ELECTRICITY.  107
A compound to be decomposed by the current must be in the
liquid state, and must of course be a conductor; but all compounds answering these conditions are not by this means capable
of direct decomposition.  Yet compounds, not directly decomposable by the current, are often decomposed indirectly by the
hydrogen derived from the decomposition of water that is present.
Thus, sulphuric acid is not directly decomposed by the current,
but hydrogen separated from the water present, making its appearance at the negative pole, unites with the oxygen of the acid, and
causes the evolution of fumes of sulphuric acid.
Following the suggestions of Faraday, the term  electrolysis
(from  electron, and luo, I unloose) is now very generally used
to express this electro-chemical decomposition; and the term
electrolyte to indicate a compound capable of being thus decom.
posed.  The positive pole or electrode is also called the anode,
and the negative pole the cathode (froin ana, upward, icata,
downward, and odos, a way).
But instead of the terms anode and cathode, most writers prefer
to say positive or negative electrode, as the case may be.
The elements of a compound capable of separation by this
mode, are termed ions (from  the Greek participle ion, going);
the anion being the element which appears at the anode, and the
cation the element which goes to the cathode.  It will at once be
seen that the anions are electro-negatives, and the cations electropositives.
It is not to be inferred from the above remarks. that every substance will always make its appearance at the same electrode,
whatever may be the other substance from which it is separated
by the electrolytic action.  Oxygen does indeed always appear at
the positive electrode, and potassium at the negative; but in the
electrolyses of the compounds of other substances, that element
will appear at the positive electrode which is most electro-negative,
and that at the negative which is most positive.
113. The following table exhibits the electrical relations of several of
the more important elements. It is to be understood that each subQuF.sTsoNs.-Are all compounds directly decomposable by the current?
Define the terms, electrolyte, anode and cathode.  What are ions — what
anions and cations? Will every substance always make its appearance
at the same electrode, whatever may be the other from which it is separatedC? What is the law in this respect?




108   EFFrE CTS OF GALVANIC  ELECTRICITY.
stance in the first column is electro-negative as compared with each ono
below it, but in the second column each substance is negative as corn.
pared with all above it:
Oxygen.                          Potassium.
Fluorine.                        Sodium.
Chlorine.                        Calcium.
Iodine.                          Carbon.
Sulphur.                         Hydrogen.
Nitrogen.                        Zinc.
Phosphorus.                      Iron.
Arsenic.                         Bismuth.
Antimony.                        Tin.
Gold.                            Lead.
Mercury.                         Copper.
Silver.                          Silver.
114. We have seen that the decomposition of a compound takes
place only when the current is made to pass through it-then one
of the ingredients is collected at one electrode, and the other at
the other electrode; thus in the electrolysis of water, the oxygen
is collected at the positive and the hydrogen at the negative electrode.  But how is it that these effects are produced? and at what
precise point or points?  Are both gases liberated at each electrode, but one only, hydrogen (the electro-positive element), collecting at the negative electrode, and the other, oxygen (the
electro-negative element), collecting at the positive pole?  This
would require that opposite currents of oxygen and hydrogen
should be passing by each other in the liquid between the poles
while the battery is in operation, of which we have no evidence.
Or, does the decomposition take place along the whole line between the poles traversed by the current?  Other similar inquiries
may be made, which cannot be answered positively, but the following is believed to be a correct representation of the phenomena
witnessed, so far as we are able to determine.  Wrater is a compound of hydrogen, which we will represent by H, and oxygen,
which we will indicate by O;-and the compound by }.  A tier
or row of particles between the poles we may then represent thusd
H,1 H, H. H, H   -
+0 0 0 0 0 0
QUESTIONS.-114. When only does the decomposition of a compound
take place?  Describe the manner in which the decomposition of water
is supposed to be effected by the passage of the electric current.




EFFECTS OF GALVANIC ELECTR'ICITY.  109
the sign + indicating the position of the positive pole, and -  that
of the negative.
Instantly as the current begins to pass, oxygen from the decom.
position of the water appears on the positive side, and hydrogen
from the same decomposition at the negative side, a state of things
which may be represented as follows:, H, H, H, H, H,I   --
+00 O 000
We have now one less particle of water than before, and one of
the elements of the decomposed particle is found at one electrode,
and the other at the other electrode.  To produce this effect, it is
only necessary that, by the action of the current, all the particles
of hydrogen should be removed one place to the right, or all the
particles of oxygen one place to the left.  That is, the electrolysis
of every particle of water in the track of the current has taken
place, but the immediate reunion of all the particles has followed,
except the extreme particle of oxygen, on the one hand, and the
extreme hydrogen on the other.
The oxygen and hydrogen thus liberated, at once make their
escape; and the continued action of the current produces a like
effect on other particles of water until the action ceases, or all the
water is decomposed.
115. The quantity of electricity required to effect the decomposition
of any compound is probably always the same, as would be shown if we
had means to measure it accurately; and the relative quantities of
several electrolites decomposed by a given quantity of electricity will be
represented by the combining numbers of these compounds. We shall
hereafter have occasion to allude to this point again, in connection with
the subject of combining proportions or equivalents.
116. Electro-Metallurgy is the name applied to the deposition
of the metals from their compounds by the chemical agency of
the galvanic current.  We have seen above (103), in describing
Daniel's battery, that during its action there is a constant deposition of metallic copper upon the negative plate.  Now, if, for
the copper plate in this arrangement, a medal, or coin, or other
conducting body be substituted, the deposition of the copper upon
it will take place in the same manner, and all its minute pecuQUESTIONS.-115. Is the quantity of electricity required to effect the
same decomposition always the same? 116. What is electro-metallurgy?
10




110   EFF ECTS  OF  GALVANIC  ELECTRICITY.
liarities will be copied. An apparatus of this kind, called the
electrotype, is figured below.
A glass vessel is partly filled with a saturated
solution of blue vitriol, and in this is placed a
porous vessel, containing dilute sulphuric acid,
and a rod of zinc, Z, having a binding screw at
top.   The medal or coin to be copied is then
suspended in the vitriol solution by means of a
wire inserted in the binding screw.  The surface
of the medal on which the copper is to be deposited should be perfectly clean, and the other
1il il  1 lIsurface should be protected by a coating of wax'It~:[    l         or varnish.  In the figure, two medals, MI, M, are
Electotype.    supposed to be connected at the same time with
the zinc.
A  better method than the above is to use a regular Smee's
battery, and to have the blue vitriol solution in a separate vessel, as in the annexed figure.
Then  let the  article  to  be
copied, A, be connected with
the zinc of the battery, and a
plate  of copper, C, with  the
silver, both  being  suspended,
at a little distance from  each
I'ii   ~  other, in the vitriol solution.
Eectrotype       By the action of the battery,
the piece of copper will be gradually dissolved, and a corresponding deposit of metallic copper
made upon the medal.
In the battery here used, one of the zinc plates is supposed to be
removed, presenting clearly to view the plate of silver.
117. Other metals besides copper may be deposited in this manner,
but a battery of several cells is in most cases required.  The most important application that has been made of this discovery is in depositilg
silver and gold in thin laminve upon other metals, called plating or gilling.  For this purpose a Daniel's or Smee's battery of about four cells
answers well, and a fifth, which is called the depositing cell. This is
QuarSTroN.-Describe the apparatus called the electrotypLe.




E LECTR O-M AGNETIS M.                      ill
filled with a solution of cyanide of potassium, and used in the same
manner as just described for obtaining a deposit of copper, except that
silver or gold must be used instead of the copper, C, according as one
or the other of these metals is to be precipitated.
E L E C T R 0-M A G N E T I S M.
118. Natural Magnet, or Loadstone. —Among the ores of iron,
pieces are often found which possess the property of attracting and
retaining pieces of iron or steel with more or less force, and are
called nmaCnets or loadctone.  Each magnet always has two points
iu which the attractive force appears to be concentrated, which
are called the poles. They are always readily found by rolling
the magnet in iron filings, which will be collected more at these
points than in other places.  Gene-.
rally they are nearly opposite to each
other.  (See figure.)  If a magnet    =         _     
is broken into several pieces, each
always retains the same magnetic                Loadstoe.
properties as the whole mass, but in less degree.  Sometimes a
magnet has more than two poles.
119. If a magnet be suspended horizontally by a thread, or
placed upon a piece of cork floating in a vessel of water, one of
the poles will turn towards the north, and is hence called the
vorth pole, and the other towards the south, and is called the
south pole.
If two magnets thus suspended are brought near each other, it
will be found that like poles repel each other, but unlike poles
attract.  These attractions and repulsions extend to some distance, and are not affected by the interposition of other bodies,
not capable of becoming magnetic. This may easily be shown
by interposing a pane of glass, or plate of copper, or a thin piece
QUESTIONS.-118. What is the natural magnet, or loadstone.?  What
are the poles?  What is the effect if the magnet be broken in several
pieces?  119. What is the north pole?  What the south pole? When
two magnets freely suspended are brought near each other, what is
observed of like, and what of unlike poles?




112           EE LECTRO-MAG NETISi.
of wood between the two magnets, when it will be seen that the
action of the magnets upon each other is the same as before, and
does not even suffer diminution by the interposed substance, except
as the distance between them is increased.
120. lMagnets and Diamagnets.-It has of late been very
satisfactorily determined that all substances may be divided into
two classes,-the magnetic and the diamagnetic.  To the first
class belong all substances which, like iron, nickel and cobalt,
are attracted by either pole of a magnet when presented near
them; and when shaped into bars and free to move (as when
suspended by a thread in the centre) in the vicinity of a magnet,
they arrange themselves in the direction-of a line uniting its
_sN-      -       XL,  poles.  Two bar magnets best illus.
~-~ 7-.......... trate this property; when in the
Maglnets.         vicinity of each other, and free to
move, they take the position indicated in the figure.
The substances already named are the only ones that possess
this property in any considerable degree; but others have recently
been added to the list, as manganese, chromium, titanium, palladium, platinum, oxygen gas, &c., in which the magnetic property
is manifested only when a powerful magnet is used.
Diamagnetic substances are such as are repelled by either pole
_-  ~       of a magnet, and when made into
the form of bars and free to move,
in the vicinity of the poles of a
S_=Aj MAC V NET       N   magnet, arrange themselves at right
i it           angles to a line uniting its poles.
This relative position of the magnet
and diamagnetic bar is shown in the
accompanying figure.
This diamagnetic property is manifested more powerfully by
bismuth than by any other substance, but phosphorus, antimony,
zinc, tin, sodium, mercury, copper, gold, glass, ether, alcohol, and
many other bodies, are similarly affected.  The experiment can
only be shown by using very powerful magnets.
QUESTION.-] 20. Into what two classes may all substances he divided?
IIow do magnetic substances arrange themselves when brought into the
vicinity of a magnet? How'do diamagnetic substances?




ELECTRO-M AGN ETIS M.                      113
121. Magnetic Induction. —When either pole of a magnet is
brought in contact with a piece of soft iron, or only very near it,
the iron itself becomes magnetic, and remains so until the magnet
is removed.  The figure following represents several pieces of
iron, placed in different positions near the poles of a magnet; on
examination, they will all be found to have the magnetic property,
their poles being developed as indicated by the letters N and S.
Magnetic Induction.
This influence of a magnet upon pieces of iron, which extends to
a distance around its poles, is called its inlductive influence.
This influence is exerted by a powerful magnet to a    II[f
considerable distance from  either pole, or even through
other bodies (119) which are not themselves capable of
becoming magnetic.
A piece of iron or other substance which is attracted
by either pole of a magnet, is evidently first rendered
magnetic by induction, and then the attraction follows as
a, necessary consequence.  But the first piece, as a nail,
being rendered magnetic by induction, will act in like
manner upon a second, and this upon a third, and so on;
so that several pieces may be lifted one after another, as
represented in the figure.  But it will be found, when
the connection with the first magnet is broken, the pieces
of iron instantly lose their magnetism, and fall asunder.
122. Pieces of hardened steel will also be affected in
Margnetic
a similar manner, but much less readily, and, unlike Induction.
QUElTSTIONS. -121. What is the effect when either pole of a magnet is
brought near a piece of soft iron?  What is meant by magnetic induction? Why is a piece of soft iron attracted by a magnet?
10*




114              ELECTR O -  AGNETISM.
iron, they retain the magnetism  that has been induced.  They
therefore become permanently magnetic, and for nearly every
purpose are superior to the natural magnet, and may be denominated artificial magnets.  The same magnet may be used suc.
cessively to magnetize any number of steel bars, without losing
any of its virtue; from which it follows that the magnet communicates nothing to them, but only by its influence developes some
hidden principle already there. Artificial magnets are frequently
made in the form of the horse-shoe, and are called horse-shoe
magnets.  To the poles a short piece of soft iron is usually
accurately fitted, called the armature or keeper.
123. The Magnetic Needle-Dipping Needle.-A  slender bar
of magnetized steel, suspended upon a pivot, so as to revolve
freely, constitutes the magnetic needle.  Sometimes it is attached
to a circular card, and suspended upon a pivot, as in the mariner's
conmpass.
124. If a steel bar be suspended by its centre of gravity, and
afterwards carefully magnetized, it will be found not only to place
itself in the magnetic meridian, but to assume a position inclined
to the horizon.  In northern latitudes, the north pole will be
depressed and the south pole elevated, while in southern latitudes
the south pole will be depressed.  The angle of inclination is
generally nearly the same in the same place, and is called the
dip of the 9needle; and a needle nicely balanced and adjusted for
showing the dip is called a dipping needle.
The dip of the needle is subject to considerable variation, but at the
present time it is, at Baltimore, about 710 30'; at Philadelphia, 72~ 15';
at New York, 7803~; at Middletown, Conn., 730 30'; and at Boston, 740 24.
The magnetic needle does not always point to the true north and south,
but deviates more or less from this position at different times and places.
This is called its variation. At Philadelphia, in 1840, the variation was
30 52! W., and at Middletown, Conn., about 60 40'.
125. Terrestrial Magnetism.-The earth may be considered
as a great natural magnet, which, by its action on the needle, in
the same manner as any other magnet, causes it to place itself in
QUESTioNs.-122. May magnetism be induced in pieces of tempered
steel?  What are artificial magnets?  123. What constitutes the magnetic
needle?  124. What is a dipping needle?  125. What may the earth be
considered?




ELEOCTRO-MAGNETISM.                        115
th3 position of north and south.  Indeed, it is by the inductive
influence of the earth that magnetism is developed in bodies upon
its surface. This is shown in bars of iron or steel that have stood
long in a vertical position, which are always found to be magnetic.
Tongs and pokers, fiom their being usually kept in an upright
position, are almost always found to be magnetic.
As it has been agreed to call that pole of the needle which
points northward, the north pole, it is evident that the pole of
the earth situated iiorth must be a south pole; that is, it must
possess southern. polarity.  So, also, the south pole of the earth
must possess northern polarity.
126. Relation between the Electric Current and Magnetism.
-It has been long known that a discharge of lightning will often
affect seriously the magnetic needle, sometimes reversing its poles;
but it was not until 1819 that (Ersted made his famous discovery,
which has served as the basis of the beautiful science of Electro3Iagnetism.
He first observed that when the wire, connecting the electrodes
of an active galvanic battery, is brought near a magnetic needle,
it is made to deviate from its ordinary position, and assume a new
one, depending upon the direction of the current and the position
of the wire in regard to the needle. Thus, the needle being in
its natural position, —lst, if the connecting wire be above the
needle and parallel to it, the pole next the negative electrode will
move westward; 2d, if the wire be.::~
beneath the needle, it will move east-                     k
ward; 3d, if the wire is on the west
side, this pole will be depressed; and,
4th, if it be on the east side, it will
be elevated.  The figure in the margin
indicates the motion that will be produced in the first of the above cases.     Current a.Ld Needle.
If the wire be placed under the needle, and the current made
QUESTIONS.-Why do tongs and pokers become magnetic by standing
in a vertical position? What is said of the north and south poles of the
earth?  126. What was the fact first observed by (Ersted as regards the
wire conducting a galvanic current and a magnet?




1 6              EL EC TRO - MA GNET ISM.
to pass from north to south, the motion of the needle will be the
same as indicated in the figure.
It follows, therefore, if the wire be bent around the needle, in
-~ Hi??the form  of a rectangle, so as to
convey the current in one direction
above the needle, and back again, in
f-     ~ |-?.....the opposite direction  beneath  it,
both parts will conspire to produce
the same effect, and the motion of
the needle will be much increased.
Such an arrangement is represented
Currn  n.  in the annexed figure.
In  all these cases, the tendency of the needle is to settle
directly across the wire, or at right angles to the direction of
the current, while the influence of the earth is exerted to bring
it in its first position, parallel with the wire, supposing the experinent to be commenced with the needle in its natural position.
The position it will ultimately take will therefore be intermediate
between these two.
127. To avoid the directive influence of the earth upon the
needle, the astalic (from the Greek astatos, unstable) needle has
been contrived.  It consists of two needles, of nearly equal
strength, fixed to the same axis, with their
poles reversed in reference to each other, and
suspended by a thread, as shown in the
figure.  One of the needles being a little
more highly magnetized than the other, or
_N               a little larger, they will have a slight ten- static Nedl.   dency to settle in the meridian.  If, now, a
wire is bent several times around the lower
needle, each turn or coil being coated with some insulating substance, when the current is passed around it, its influence on
both needles will be to turn them in the same direction; and the
QUESTIONs. —What is the effect if the wire is bent around so as to
pass several times around the needle?  What is the real tendency
of the needle?  127. What is the astatic needle2  Describe its construction.




ELECTRO-MAGNETISM.                         117
arrangement becomes a most delicateinstrument for indicating the passage of
the feeblest currents.  Such an instrument is called a galvanzometer, or galvanoscope.  To protect it from  currents
of air, the whole is usually enclosed in
a glass case; and beneath the upper
needle, and above the coil of wire, a
graduated circle is placed, to indicate
exactly the comparative deflections of the
needle.
Such  an  instrument, in  connection
with a thermo-electric pile (93), becomes
a most delicate thermometer, which is
capable of indicating a change of temn- l1L
perature of only a very small fraction of
Astatic Needle.
a degree.
128. Tangential Force. —By a careful inspection of the motions
produced in the needle by the current in the several positions of
the wire, as described in paragraph 126, it will be evident that
the real tendency of each pole is to revolve around the connecting
wire in a circle, the plane of which is perpendicular to the wire;around the north pole in one direction and around the south pole
in the other.  The force which causes this motion is exerted in
lines which are tangents to the circumference of these circles, and
is therefore called a tangentiaalforce.
The motion of the needle actually procluced will of course
depend upon the mode in which it is supported, as well as the
position of the wire in reference to it.  It is to be remarked, too,
that the pole is a mere point situated near the extremity of the
needle; —between this point and the wire the force is exerted.
This point,-the magnetic pole,-cannot exist independent of
the needle itself, which must ther, fore always move with it; and
therefore in order to determine the real motion in any particular
QuJESTIONS.-Descibe the galvanometer, or galvanoscope.  128. What
is the real tendency of each pole of a magnet when brought near the
wire?  What is the force called which produces this motion?  Upon
what will the motion actually produced depend?




118             E L E C T R O - MA G N E T IS M.
case we are to consider the two circumstances,-First, the motion
the pole tends to make, and Secondly, the motion of which the
needle is susceptible.  Upon these two conditions plainly will
depend the actual motion that will result.
129. In order easily to remember the particular motion a pole
will tend to make in any given case, take the following example.
Let us suppose the conducting wire to be placed in a vertical
$P 0position, and the current of positive electricity to be dlescending
/'~.PI7             through it, the tendency of a north
pole in the vicinity of the wire
will be to move around it in a horizontal circle, in the direction indicated by the arrows in the figure,
[///~ -—'"~.~~  or in the direction of the hands
of a watch with the dial upward.
Pole Revolves.       The tendency of the south pole
would be to revolve in the opposite direction.  If the direction
of the electrical current is reversed, and it is made to pass upward, both poles would tend to revolve in the opposite direction
from that described above. Whatever may be the position of
the conducting wire with reference to the needle, the motions
produced will always be in accordance with these statements; and
reference being had to this particular position of the conducting
wire and the needle, we can always determine by inspection in
what direction the needle will move, whatever may be the position
of the wire in regard to it.
We have here been speaking only of motions produced in the
needle by the conducting wire; but it is plain that if the pole of
a magnetic needle tends to revolve around a fixed conducting
wire, a free wire will have a tendency to revolve around the pole
of a fixed needle.  The fact is, the influence is mutual, and both
the wire and the pole tend to revolve, as we will proceed to show.
QUESTIONs.-To determine the real motion that will be produced in a
given case, what two things are to be considered? 129.1 When the current is descending perpendicularly, what will be the tendency of the
north pole of a needle in the vicinity of the wire?




EL EC TRO-M A GN ET IS AM.                 119
130. Both the revolution of a pole around a fixed wire, and the
revolution of a wire around a fixed pole, may be shown by the
apparatus, a section of
which is seen in the cut
in the margin.  A and
1B are two glass vessels,
filled nearly to the top
with mercury.  A wire,
supported by a pillar between the vessels, has       7 
one end bent down so
as to dip into the mercury in A; and the other,_                   l
end is bent into a hookl,
on which a short piece       Both Pole and Connecting Wire revolve.
of wire is suspended, so that its lower end shall also dip into the
mercury in the vessel B.  Conducting wires pass through the
bottoms of both vessels, with binding screws, C and D, to connect
them with the poles of the battery; and to that in A, a small
magnet is attached by a thread, so that one of its poles may be a
little above the surface of the mercury; and in the vessel B
another small magnet is firmly fixed, with one pole a little above
the mercury. When the current is passed through this apparatus,
as indicated by the arrows, the upper pole of the magnet in A
will revolve slowly around the conducting wire, and the free conducting wire suspended in B will revolve around the fixed pole
near it.
131. Further Experiments illustrating the Relation of the
Magnet and a Galvanic Current.-Experiments to illustrate the
relation of a current and the magnet may be multiplied almost
indefinitely.
De la Rive's Ring is a very beautiful contrivance to show the
influence of a magnetic pole upon a conducting wire capable of
motion.  A  copper wire is bent into a circle about an inch in
QUESTIONS. —130. Describe the apparatus figured in paragraph 180.
What is the point illustrated?




120              ELEC T RO-M A GNET I S M.
diameter, and the two ends passed through a piece of wood or
cork, and soldered, one to a slip of
zinc, Z, and the other to a slip of
copper, C.  If, now, it be placed in
a bowl of water containing a little
acid, a current of electricity will cir____         culate along the wire, in the direction
of the arrows; and if a bar magnet
TDe la Rive's Rinig.  be brought near it, it will be attracted
or repelled, according as one pole or the other of the magnet is
presented to it.  As represented in the figure, if the north pole
of the magnet is presented to it, it will be attracted; the south
pole will first repel it, but in a little time it will turn around, and
will then be attracted.  We may, therefore, properly regard it as
a fiat magnet, having its two poles in the centre of the circle, the
one on one side, and the other on the other; the south pole being
in that surface on which, when held before you, the positive current flows in the direction of the hands of a watch.  The apparatus
will be more powerful if the conducting wire, covered with silk,
to prevent lateral communication, be formed into several circles
of the same diameter, on the principle of the multiplier.
132. But whb/t are the forces that have produced these special
movements?  Giving our attention for the present only to the
part of the current upward on one side of the ring and downward
on the other, we have seen (129) that the downward current tends
to revolve around the north pole of a needle in the direction of
the hands of a watch, and the upward current in the opposite
direction; let these facts be kept in mind while the eye rests upon
the figure, and it is plain that the effect must be to cause the ring
to approach the pole, or apparent attraction ensues.  If, now, the
magnet be suddenly removed, and the south pole presented, in
accordance with the same laws, the ring recedes, turns around,
and again approaches the pole i
QurSTrONS.-131. Describe De la Rive's Ring, and the mode of
using it. What may we regard it? 132. Give the reasons for these
movements.




EL E cT RO - 1 A GNET I SM.                  121
133. The g#lvanoscope is represented  by  the  next figure
N  and S are the north and south poles of a
permanent horse shoe magnet, supported upon
a stand; and between them, in a small glass.            I.
tube, is a strip of gold leaf, connected at top   F:Ti',,/
and bottom with binding screws, as shown in
the figure.  Now  when the current is passed              11i'iis
through the gold leaf, it is made to curve to one         i 
side or the other, according as the motion of the
current is upward or downward.  As the poles            flj
are situated in the figure, if thb direction of the     i 1.   1 l
current is downward, the curving or convexity          i"ll 
of the gold leaf will be upward from the plane         iiill ji
of the paper; but if the current is upward the
strip of gold leaf will be convex in the opposite
direction, or backward from  the plane of the    __
paper.
~~~~~~~~~~~~paper.                      Un~Galvanoscope.
134. The Revolvi.g    Spur W/heel, figured in the margin, is
made to revolve by the
action of a magnet upon                    R
the galvanic current. A
wheel W  made of sheet
brass, is supported in
such a manner that its
rays touch in a globule
of mercury in the base                  W                   B
beneath, from  which  a,ad         
concealed  wire extends             A.d 
to the binding screw A,
the other binding screw                _     __
B    being   connected,    in            I'X~iJ! ll! llll 11 iill illlll!  IIi l! I i  IIIIfl iII  i I!IIII,, I "I i  Il-q~~'i Si
like manner, with  the                 Revolving Wheel.
wire R  which supports the wheel.  N S is a magnet placed so
QUESTIONs.-133. Describe the gaivanosccpe.  134. Describe the re.
volving spur wheel, and give the reasons for the movement produced.
11




122              E         O I E C T R O - MA A   N Ei' T IS.
that its poles shall be as nearly as possible one on each  hicde of
the ray of the wheel which  for the time is in contact with the
mercury.'"hen the poles of the galvanic battery are connected
with the binding screws, a ray of the wheel being in contact with
the globule of mercury, the current passes through it, and the
wheel is made to revolve on its axis. A permanent magnet may
be used, or an electro-magnet, as represented in the figure (p. 121).
135. Relation of Current to the Eartli's Magnetism.-The
ring described in paragraph 131 is acted upon by the earth's
magnetism precisely in the. same manner as by the magnet, only
that the influence is less in degree: In order that it may be made
to move by the magnetism of the earth, it is only necessary that
it should be enlarged sufficiently, and a powerful current passed
through it.   The following modification of it answers a good
purpose.
___ LBB                Let A  and B  be  two
A iI —'   metallic  pillars, insulated
Yit    i ll from  each other, provided
each with a horizontal arm
terminating in a small cup
filled  with  mercury, and
n  -I  connected  at the bottom
with binding screws.  Let
-=___  =___  ______  a ring R  of copper wire,
8 or 10 inches in diameter,
_    be suspended by the ends
of the wire fiom  the cups
Influence of Earth        of mercury, and the poles
of the battery connected
with the binding screws; — the current will pass around the circle
of wire, whichb by the influence of the earth's magnetism, will be
made to move until at length it will take a position with its plane
at right magles to the meridian.  Supposing the direction of the
current to be as indicated by the arrows, and recollecting that tlle
QuISTIToNS.-135. Does the earth's magnetism act upon a current in
the same manner as a magnet?  Describe the movements produced in
the ring here figured when conveying the current by virtue of the
earth's ma-nvetism.




ELECTR O- AAGNETIS M.                       123
north pole of the earth really possesses southern (125) polarity,
let the intelligent student determine which side of the circle of
wire will settle to the east and which to the west!
It may afford some aid to reflect that the action on the circle
of wire will be the same as if it were square,
ias shown in the margin, in which it appears 
there are four parts conveying the current,
two on which its motion is horizontal in opposite directions and on the same side of the
point of support.  The influence of these is  i
lost and may not therefore be further con- 9: i
sidered.  On the other two parts the motion   I
of the current is in opposite directions,-?-:
being on one upward and on the other down- Upwvard and Downward
ward-and on opposite sides of the point of          current.
support.  Now the tendency of the part conveying the upward
current will be to revolve round the north pole of the earth in
one direction, and of the part conveying the downward current to
revolve around this pole in the opposite direction; considering
then the mode in which the wire is suspended, it is plain that the
tendency of the circle of wire will be to settle with its plane due
east and west, or at right angles to the meridian.  If, then, before
passing the current, the plane of the circle of wire is placed in the
meridian when the current is made to pass it will turn on its
points of support until it takes a position at right angles to the
meridian.  In every case, the side of the circle conveying the
downward current will move towards the east, and the other side
of course towards the west.
The same movement will be produced if the wire conveying the
current is bent several times around, as represented in the first figure
on the next page, and supported by its two ends resting in cups
of mercury, with which the two poles of the battery are to be
connected by binding screws not represented in the figure.  The
influence of each coil conspires to produce the same effect, and
therefore the motions described will be more readily produced.
QUESTIONs.-Explain the reasons for the motions which are produced
by the earth's magnetism, as illustrated by the preceding figure, and alsa
the two figures on the next page.




124              E L E  a ECT 1RO-' MAGN E T I S M.
But it is not necessary that the diffferent coils of the wire should lie in the
same plane, the result being the sa-me
if it is wound in the form of a helix,
I I
Influence of Earth's Magnetism.
as represented in the next figure; the helix then truly representing a bar magnet, as will be found by holding either pole of a
magnet near either end.
By examining the direction of the current in this helix, considerinrg it as a bar magnet, it will be found that is the south pole
in which (when it is held up before the eye) the current is moving
in the direction of the hands of a watch.  It is scarcely necessary
to remark that, in the other pole, the direction of the current is
the reverse of this.
-3S. induction of MIag'netism  by a Current. —Magnetism  is
w N        induced in a bar of soft iron by the simple
passage of a current near it, in a direction at
______ right angles to the bar.  Thus, if WI be the
conducting wire, and N S a small piece of iron
lying under the wire, while the current is passing, magnetic polarity will be induced in the
Induction of iMagnetism iron, N  being a north pole, and S a south
by a Current.    pole, when the current passes from     W  to I;
but if the current pass from I to W, the poles will be reversed.
But, if the wire is made to pass around the iron many times,
the effect will be greatly increased.   This is accomplished by
QUESTIO.Ns.-When the south pole of the helix is held up before the
face, in what direction is the current found to be moving?  136. How
is magnetism induced in a piece of iron by the galvanic current?




EL ECTRO-M A GN ET I SM.                     1 25
placing the iron in a helix of wire, as shown in t;he figure.  The
current being then made to  v                                  x
pass in the direction of the
arrows,  the  iron  becomes
strongly magnetic, with  its -..    
poles as shown by the letters      tl  7- -'   ~      I
N and S.  The cups P and
N  ser ve  to  connect  it with   Induction of 3Iatgnetism by a Current.
N  serve to connect it with
the battery.  When the current is broken, the iron ceases at onee
to be magnetic; but if a piece of hardened steel be substituted
for the iron, it retains its magnetisnm permanently.
A magnet formed in this manner, by the passage of a current
of electricity around it, is very properly termed an
eectro-maygnet.  Magnets of this kind have some- 
times been made of sufficient strength to sustain a
weight of 2000 or even 3000 pounds.  For this pur-       m
pose, a bar of iron of considerable size is bent in the  
form of a horse-shoe, and the conducting wire made?:
to pass many times around it, as represented in the    c J
figure.  An armature of soft iron (122) is attached
to the poles, as with the common magnet, from which  Electro-magnet
the weights are suspended.  As stated above, when the current of
electricity i is interrupted, the magnetism will be immediately destroyed, and the weights drop off.
137, The _J1gic Circle, as it has been termed,
possesses too much interest to be here omitted,
though no new principle is developed by its action.,
Two semi-circles, A and B3, are made of a stout bar 
of soft irone and well fitted together, so as to form.
a circle, C, and include a small helix of wire,   B,
the two ends of which are to be connected with the      >
electrodes of a small but active battery.  While the        )
current is passing, the semi-circles are made powerfully magnetic, and will adhere with a force which   11.X
is capable of sustaining a weight of many pounds.      ic
QuESTIONS. —What is the effect when the current is made to pass many
times around the piece of iron? What constitutes the dlectro-nagonet?
137. Describe the nagic circle.
11. *




126             E1x:E C L TRt O-M AGNET I S M.
The wire uced in all these arrangements is supposed to be wound
with some insulating substance, as silk or cotton, to prevent the
contact of the separate coils, which would permit a lateral discharge
of the current, so that it would not pass around the whole length
of the wire.
183. To form  an effective electro-magnet, the total length of
copper vwire intended to be used is cut into several portions, each
of which, covered with thread, is coiled separately on the iron.
The ends of all the wires are then collected into separate parcels,
and are made to communicate with the same battery, taking care
that the positive current shall pass along each wire in the same
direction.  The current is thus divided into a number of branches,
and has only a short passage from  one end of the battery to the
other, though it gives energy to a multitude of coils.  This was
first made known by Prof. -lenry, now Secretary of the Smithsonian Institution.
189. I.agnetism  of the Earth. — We have seen above (125)
that the earth may be considered as a great magnet, having its
south pole somewhere near its north geographical pole, and its
north pole near its south geographical pole; and it has been suggested that this may be occasioned by currents of electricity flowing around it, beneath its surface, from east to west, or in the
direction opposite to that of its motion on its axis.  Indeed, it has
even been suggested that these currents may have their origin in
the heating influence of the sun's rays, as successive portions of
the earth's surface come under their influence by its daily motion;
but this is to be regarded as only plausible
e-.=-                        Ticonjecture.  That the needle would be in/  /,<:~"?:y,-?~,  fluenced by s utch a current, precisely as it
really is, at difierent points of the earth's
surface, may  be shown  by winding a
1 7-, /Ii       covered wire several times around the
>X,,.t,/,/~ /.   equator of a common globe, and placing
"M3,,?>! ~ --- a small magnetic needle upon it while
A:l.th's ianlelim.  the current is pnssing, as shown in the
QuEsToINs. s -Why  must the wire used for this purpose be wound with
some non-conlucting substance?  1388. What is said of the total length
of wire used for this purpose? 189. What is said of the earth in referelce to this silh;iect?  Io1wv may the magnetism of the earth be occasioned? Dcscribe the Luice in this paragraph.




T E C v R - - -M A G N E T I S M.             127
figure (p. 126).  The small needle will uniformly settle in the
meridian.
140. Electro-magnetic Engines,-All the above motions, it
will be observed, whether of the magnetic needle or of the conducting, wire, have been produced by the tangential force; but
various machines have been devised, called electro-mag~netic engines,
for producing motion by direct influence upon each other of th,
unlike and like poles of two or more magnets; one of which al
least must be an electro-magnet.
The next figure represents a very simple electro-magnetic machine,
which by its motion rings a bell with considerable force. N and S are the
north and south poles of a common horseshoe magnet, which stands in a vertical
position, with its poles downward. A is
a piece of soft iron wound with copper
wire and fixed upon a vertical axis, so as
to revolve very accurately between the
poles of a magnet; and CC are binding
screws for connecting the wires from  the
galvanic battery.  The extremities of the
wire around the magnet A connect with
C C, by means of parts not represented in
the figure, in such a manner that the
current flows in the proper direction to
develope north polarity in the further extremity A as it approaches the south pole
of the magnet S, and south polarity in the
other extremity as it approaches the north
pole N: but the moment the revolving
mlignet has arrived at a position between
N and S, the two poles of the stationary
magnet, where it would be held if the                   A
s-ame polarity remained, the direction of
the current is reversed, and, as a necessary consequence, the polarity of the re-.
voiving magnet.  If its momentum  has
now carried it a little beyond the point
of greatest attraction, it will be urged
on by repulsion  until it has made  a
quarter of a revolution, when it will be
attracted as before.  At S on the vertical    Electro-magnetic Engine.
axis is a perpetual screw which acts upon
the teeth of a ratchet wheel, and causes the hammer to strike the bell B.
The machine may be constructed with more than two magnets, and in
a variety of forms, but whether it will ever be made practically useful
remains to be determined:
QUESTIONS. - 140. What are electro-n'gynelic  ngines?  Describe thf
engine represented in the figure.




E L E C T R O- 5M A G N E T I S M.
141. lnutual Influence of Two Currents, —Two currents moving
in the same direction in the vicinity of each other are mutually
attracted, but if moving in opposite directions they repel each
other.
Let a helix of slender wire be sus.
pended by the top so that the bottom  may just touch in a cup of
mercury; and let a current from  a
battery  be passed through it.  In
tween the coils, the spiral will be
l_ __   -    shortened, and the lower end raised,
from the mercury, thus breaking the
____-___ —— __________     icircuit. But when the current ceases
===,_________       the end of the wire again falls so as
i'!7l    to touch the mercury, and the curAttraction.        rent is renewed with the same effects
as before.  Every time the wire touches the mercury a brilliant
spark is produced.  Two currents therefore in the same direction
attract each other.
142. Electro-Dynamic Induction.-A  current of electricity
passing through a conductor in a given direction, induces a current in the opposite direction in a second conductor situated
parallel to the first. Thus, let A B be a portion of a wire conA  B  necting the poles of a galvanic battery, and M N  a
+  portion  of a second wire
M                              N    parallel, and near to  the
Secondary current.        first;-at the moment the
circuit is formed and the current passes through the first wire in
the direction from  ~+ to -  a secondary current is induced in the
second wire in the opposite direction.  This current is but for an
instant, but is renewed in the opposite direction when the battery
current is again broken.
QuESTIONS.-141. How do two currents moving in the same direction
affect each other? Describe the experiment illustrated in the annexed
figure.  142. How may a current be made to induce another current
called a secondary current?




ELLECTRO-MAGNETISM.                       129
A. better method to demonstrate the existence of this secondary
current is as follows: Let A be a coil of large copper wire, or,
better, of copper ribbon, covered with
some non-conducting substance, and
having binding screws attached to
each end, to receive the polar wires
of the battery.  Above this is placed
a coil, NV, of fine covered wire, with
a metallic handle at each end; and
when the battery current is made to          A
pass through the lower coil, the
secondary current will be induced           Secondary Current.
in the upper coil, as will be plainly
indicated by grasping the handles with the moist hands.  In this
case, as before, the secondary current is induced at the moment
the battery current is established, in the direction opposite that
of the battery current, and again when the battery current ceases
in the same direction as this latter current.
The former is termed the initial and the latter the terminal
secondary current.
The effect of the shocks will be increased by rapidly breaking
and closing the battery circuit, the feeble intensity of the shocks
being compensated by their frequency.
Of the two coils above used, it is to be observed, that the one
connecting the poles of the battery is made of large wire, or
ribbon of metal, and is of moderate length, while the other, in
which the secondary current is to be induced, is made of smaller
wire, and is of much greater length.  The secondary current in
this case is one of considerable intensity (100), as is shown by the
fact that it can be made to pass through the system; but if the
coil had been made of a large wire, and much shorter than it is,
the current induced would have had only a feeble intensity, but
would have been much greater in quantity. And, in general, it
is found that long coils of small wire give secondary currents of
QuEsTIoNs S.-Describe the mode of obtaining a secondary current, as
illustrated in the next figure. When only is this secondary current
induced?  What are the terms used to indicate these currents?  What
is their direction as compared with the primary current?  What is slid
of the two coils used in this experiment?




1.30             ELECTtO-M AG N E           S M.
great intensity, while, on the other hand, to obtain a current of
quantity short coils of large wire or ribbon are required.
By arrangements altogether similar to the above, with addi.
tional coils. tertiary currents have been produced, and others of
still higher orders, even up to the seventh or ninth.
The following mode of developing the tertiary current will show
the method to be pursued to obtain others of still higher orders.
A is a ribbon coil through which the battery current revolves as
before, and B another ribbon coil in which a secondary current is
induced, as already explained.  A third ribbon coil, C, is placed
at a little distance, but has its two ends connected by means of
wires with the two ends of the ribbon of the coil B, so that the
same current which is induced in B flows also in C.  Above C is
placed an intensity coil of small wire, W, with metallic handles
connected with its extremities.  Now when the battery current is
established in the coil, A, a secondary current is induced in B and
revolves in the coil, C, by which a tertiary current is induced in
the coil WA.  As the secondary current flows in the opposite
Tertiary Current.
direction from  that of the battery current, so the tertiary takes
the opposite direction from  that of the secondary; and the same
law holds good through all the series of currents.  As the distance fromn the battery increases, the strength of the current
gradually diminishes
QUESTION. —Describe the mode of obtaining a tertiary current. What
is said of the direction of the tertiary current as compared with that of
the secondary current?




EL  C T RO-  A GN E T ISM.                   131
143. Induction of Electricity by Magnetism — agnetoElectricity.-Magneto-electricity, as the  term  implies, is the
reverse of electro-magnetism.  The current of galvanic electricity
circulating around a bar of soft iron, converts it, as we have seen,
into a temporary magnet, and renders a bar of steel permanently
magnetic.  Now, d priori, it would seem  very probable that a
magnet placed in the centre of a helix or spiral of metallic wire,
would develope in it a current of electricity.  This is found to
be actually the case; but the current can be observed only at the
moment of inserting the magnet or removing it.
The development of electricity by magnetism is shown in a
very simple manner, by winding the middle of
the keeper or armature AB of a powerful horse-  
shoe magnet, with copper wire, properly bound,
and bringing the two extremities of the wire into
contact, one of which should be flattened a little,
and amalgamated by dipping it into a solution of
nitrate of mercury, and the other filed to a point.
If, now, the armature be suddenly placed upon
the magnet or removed from  it, a spark of electricity will manifest itself every time, at the point  
of contact, C, of the two extremities of the wire. Magneto-Electricity.
The electric current flows in one direction at the moment
magnetism is induced in the soft iron enclosed in the coil
of wire, and in the other direction, when its magnetism is
destroyed.
The same thing is accomplished, but in a manner a little different, by
the apparatus figured on the next page. Externally a large coil of fine
copper wire is seen, terminating in binding screws, to which wires with
handles, II, are attached, to be grasped by the hands. Within this is a
smaller coil of larger wire, the top of which is seen at B; the extremities
of this wire are soldered to the binding screws A and D, the latter also
connecting with the horizontal bar E C, which has an irregular surface,
resembling that of a coarse file. Inside of the last coil is a bundle of
small iron wires, W. Now when the wires from the battery are connected with the binding screws A and D, the current circulating in the
QUESTIONS.-143. What is the term magneto-electricity used to signify?
TDescribe the method of developing electricity by means of a peirnanent
magnet and armature.  Describe the apparatus represented by the next
figure, and the mode of using it.




132                 L E.     TR O-M A  N ET IS M.
1-1                   helix B induces magnetism in the wires W, arnd
this in turn at the moment when the magnetism is induced, or when
it is destroyed, induces
a current of electricity
in the outer helix, which
will  be  felt in  the
hands  when  grasping
the handles.
To produce the grent.est effect, the current
Dn                             from  tihe battery should
E (    be formned and broken
rapidly, which is accomc,        plished  by  connecting
one wire with the binding screw A, and drawing the end of the other
Magneto-Electricity.            over  the  rough  surface E C.
144. Magneto-electric machines are now made, which act witl
great energy, producing  all the effects both  of quantity  and
intensity.
Magneto-Electric Machine.
The above figure* represents a machine of this kind.  Several
steel magnets, NS, are firmly fixed together upon pillars on a
base board; and in front of the poles, an armature, A, in thle
* From Davis's Manual of Magnetism.
QUEsTION.-144. Describe the magnreto-electric machinle.




E L ECTRO- MAGNETI S M.                   133
form of the letter U, having its two arms wound with 2000 or
3000 feet of fine insulated wire, is made to revolve on an axis by
means of the multiplying wheel W. As the armature is made
to revolve in front of the strong poles of the fixed magnets, magnetism is induced in it (121), currents of electricity being at the
same time made to flow through the coils of wire wound upon its
arms, in accordance with the principles just explained, which are
communicated by wires, concealed under the base board, to the metallic handles, H, by the wires C and D. These currents being in one
direction while the magnetism of the armature is increasing-that
is, during one quarter of each revolution-and in the other direction
while the magnetism is diminishing, would be scarcely appreciable
but for a contrivance by which it is constantly interrupted and
renewed. This is accomplished by a toothed wheel placed upon
the axis at O, against which the wire C constantly presses, slipping from tooth to tooth as the wheel is turned.  At every interruption of the current a powerful shock is felt by any one grasping
the handles.
145. The Electro-magnetic Telegraph. —This is an instrument for conveying intelligence instantaneously, by means of the
galvanic current, to any distance, where metallic wires can be
extended and properly insulated.
We have seen above (136), that the current, when made to
pass around pieces of soft iron, renders them magnetic while the
current is passing, but that they lose their magnetism instantly
when the current is interrupted. Usually, the experiment is performed with the battery and the piece of iron in the same room,
and even upon the same table, but this is not necessary.  If the
battery be in one room, and the piece of iron in another room, or
in another building at a distance, the result will be the same,
only a little increase in the power of the battery will be necessary. All that is required is, that good conducting wires, well
insulated, should extend from the battery and form a helix around
the iron, and on closing the circuit, whatever may be the distance
QUESTIONS.-What is the length of the wire upon the revolving arms
ture? What is the use of the toothed wheel? 145. What is the electromagnetic telegraph? May the current from a battery be made to magnetize
a piece of iron at a distance? What is required for this purpose?
12




EL EC TRO-M A G N ETIS M.
of the iron from the battery, it instantly becomes magnetic, and
loses its magnetism again when the circuit is broken.  The closing
and breaking of the circuit can be performed at any point in the
line, but we suppose it to be done at the battery.
[~tIMorse Telegraph.Ii iillilllllll
Morse Telegraph.
The above figure, which represents the recording part of
Morse's telegraph, will perhaps serve better to illustrate the
operation of the instrument than a full figure of it.  A  piece
of soft iron, 3M, in the form of the letter U, with each arm surrounded with a helix of covered wire, is firmly fixed upon a baseboard, with the ends upward, and the extremities of the wires
of the helix connected with the binding screws, (seen at the right,)
with which the wires from the battery are connected. A is an
armature of soft iron, fixed to the short arm of a lever, which at
the other end carries a blunt point of steel, capable of indenting
characters upon paper when pressed against it.  Above the point
is a metallic roller, with a groove cut around it, into which the
point plays, and a narrow slip of paper is supposed to be drawn
along between them by the hand.
Now let us suppose this instrument, which we will call the
register, to be in New  York, and the battery in Washington,
with metallic wires, well insulated, extended between them;
when the operator in Washington closes the circuit, the iron Mi
instantly becomes magnetic, drawing down the armature A, and
pressing the point at the other extremity of the lever against the
paper, producing a dot if the paper is at rest, but a straight line
if it is in motion.  When the operator in Washington breaks the
QuEsTIoNs.-Describe the figure given to illustrate the recording part
of Morse's telegraph.'How is a mark made upon the paper?  Describe
the mode in which an operator in Washington may write in New York.
What are the only marks the instrument is capable of making?




ELECTRO-M AGNET ISM.                     135
circuit, the iron M loses its magnetism, and the lever drops by its
own weight, leaving the paper to move along unmarked.  When
the circuit is again closed, the point is raised again in like manner against the paper, and immediately drops when the circuit is
broken; so that the steel point in New York is perfectly under
the control of the operator in Washington, for making dots and
straight lines, with which an alphabet is easily constructed.  Thus
a dot and line (. -) is A, a line and three dots (-...) B, a single
dot (.) E, and so on through the alphabet.
In the next figure the full instrument of Morse is represented.
The paper, P, is carried along by machinery, between two rollers,
in the direction indicated by the arrows, the machinery being
propelled by a weight.   A  spiral spring, S, attached to a piece
projecting downward fromn the pen-lever, removes the steel point
from  the paper when the circuit is broken.  WT W, the wires of
Morse's Telegraph.
the magnet. The motion of the machinery is regulated by a fan,
which is partly seen in the figure.
146. In order to send communications at the same tirme from
New York to Washington, another arrangement similar to the
above is needed, with the register in Washington; but the same
wires and the same battery may be used to return an answer, after
QUESTIONS.-IOW is the alphabet used in this telegraph constructed?
146. May the same battery and the same wires be made use of to send
communications between two places in both directions?




136               ELECTRO-MAGNETISM.
the Washington operator has finished, merely by having a second
register in the same circuit in Washington, and the operator in
New York breaking and closing the circuit in that place, as before
explained.  Nor is it necessary, if the register is in New York,
the battery should be in Washington; it may be at any point in
the circuit.
In the above explanation, two wires are supposed to be extended
the whole distance between the places connected by the telegraph;
but experiment has shown that only one is really needed, as the
earth may be made to form a part of the circuit.
Besides the above, two other electric telegraphs are in use in this
country, and one or two of still different construction in Europe.
House's telegraph (from the name of the inventor) is a most ingenious
instrument, which performs the wonderful operation of printing in distinct capitals the messages transmitted.  It is too complex to be understood without a close examination of the instrument itself.
Bain's telegraph is worked precisely like Morse's, but the marks are
made on chemically prepared paper, by transmitting the current of electricity through it.  Like Morse's, also, it marks only dots or straight
lines.
QUESTINs.S.-Are more than one wire needed to send communications
between two places in both directions?  Are other telegraphs besides
Morse's in use?




PART II.
GENERAL CHEMISTRY.
147. THERE are two very distinct sub-divisions of the general
science of Chemistry, usually denominated Inorganic Chemistry,
and Organic Chemistry; the former of which treats only of the
chemical history of the elements and their inorganic compounds,
while the latter treats of the chemistry of animal and vegetable
bodies. There are, however, certain principles equally applicable
to both branches of the science, which we propose first to consider,
under the above head.
THE  ELEMENTS.- CIHEIICAL AFFINITY,
148. The Elements.-We consider all substances as simple, or
elementary, that have not been decomposed.  Of the exact number of these we cannot speak with certainty, as the existence of
two or three, the discovery of which has been announced, has not
yet been sufficiently verified. On a following page will be found
a list of sixty-two, the existence of which, it is believed, has been
established.  Some of these, as we shall see hereafter, are found
only in very small quantities, while others are abundant, the
great mass of the globe we inhabit being made up of the various
compounds of some fourteen or sixteen.
The elementary substances are usually divided into the two
classes of non-metallic and metallic, fifteen  being included in
the former, and the remainder in the latter class; but several of
each class possess characters so peculiar, that it is difficult to
assign them their proper place.
QUESTIONS.-147. What two sub-divisions of the general science of
Chemistry are there? What is the distinction between them? Of what
is it proposed to treat under the head of General Chemistry? 148. What
ase simple substances?  How many elements are there?  What is said
of the quantities of these afforded by nature?  What two divisions of
them do we recognize?
12*                                          (137)




138                      AFFINITY.
149. Affinity. —Affinity, or chemical attraction, has already
been mentioned as one of the forces with which the particles of
every kind of matter seem to be naturally endowed.  It is to the
action of this force that all chemical changes, and the accompanying phenomena, are to be attributed.  If two elements unite to
form a compound, it is this force which occasions it; and if a corn
pound of two or more substances, already formed, is destroyed by
the action of another element, it is to this force we are to look for
the cause of the change.
Affinity is exerted only between the minutest particles of different kinds of matter, causing them to combine so as to form new
bodies, endowed with new properties.  It acts only at insensible
distances; in other words, apparent contact, or the closest proximity, is necessary to its action.   Every thing which prevents
such contiguity is an obstacle to combination; and any force
which increases the distance between particles already combined,
tends to separate them permanently from  each other.  It follows,
therefore, that, though affinity is regarded as a specific power, distinct from the other forces which act on matter, its action may be
promoted, modified, or counteracted by them; and, consequently,
in studying the phenomena produced by affinity, it is necessary to
inquire into the conditions that influence its operation.
150. The most simple instance of the exercise of chemical
attraction is afforded by the admixture of two substances.  Water
and sulphuric acid, or water and alcohol, combine readily. On
the contrary, water shows little disposition to unite with sulphuric
ether, and still less with oil; for, however intimately their particles
may be mixed together, they are no sooner left at rest than the
ether separates almost entirely from the water, and a total separation takes place between that fluid and the oil.  Sugar dissolves
very sparingly in alcohol, but to any extent in water; while
camphor is dissolved in a very small degree by water, and abundantly by alcohol.  It appears, from these examples, that chemical
attraction is exerted between different bodies with different degrees
QUESTIONS.-149. What is affinity? Are all chemical changes to be referred to this force? Between what only is it exerted? Is it influenced in
its action by other forces of nature? 150. Where do we observe the most
simple instance of the exertion of this force? Is it exerted with equal
intensity between all bodies?




AF FIN'IT Y,                       139
of force. There is sometimes no proof of its existence; between
some substances it acts very feebly, and between others with great
energy.
Ajfinity is therefore said to be elective, as, when several substances, capable of combining, are mixed together, a particular
compound is always formed, in preference to others.  Thus, if
sulphuric acid, soda, and lime are at any time mixed together, the
acid will always combine with the lime, in preference to the soda.
151. Decomposition of a compound is often effected by presenting to it a third substance, having a stronger affinity for one of
the ingredients of the compound than those ingredients have for
each other.  Thus, oil has an affinity for the volatile alkali, am.
monia, and will unite with it, forming a soapy substance called
liniment.  But the ammonia has a still greater attraction for sulphuric acid; and hence, if this acid be added to the liniment, the
alkali will quit the oil, and unite by preference with the acid.
If water be poured into a solution of camphor in alcohol, the
camphor will be set free, because the alcohol combines with the
water.  Sulphuric acid, in like manner, separates baryta from
nitric acid.  Combination and decomposition occur in each of
these cases; —combination of sulphuric acid with ammonia, of
water with alcohol, and of baryta with sulphuric acid;-decomposition of the compounds formed of oil and ammonia, of alcohol
and camphor, and of nitric acid and baryta.
The action becomes more complex when two compounds are
presented to each other, of such a nature that a transfer of
elements takes place between them.  Thus, in mixing a solution of carbonate of ammonia with another of hydrochlorate
of lime, the carbonic acid of the first compound unites with the
lime of the second, while the hydrochloric acid of the second comnbines with the ammonia of the first.
152. Action of Affinity lfodified by Circumstances.-The
action of affinity is influenced greatly by various circumstances,
ondly a few of which can be here noticed.
QUESTIONS.-Why is affinity said to be elective?  151. How is decom.
position effected by the exertion of this force?  Give an illustration.
152. Is the action of affinity modified by the circumstances in which it is
exerted?




140                      A F FINITY.
Th]e particular state of a substance, whether solid, liquid, or
gaseous, is a very important circumstance, intimately affecting all
its chemical relations.  It is very rarely the case that two solids
are capable of combining;-one of them at least must first be made
liquid, either by solution in some solvent, or by melting.  Thus,
tartaric acid and carbonate of soda, in a dry state, are kept togegether for any length of time, without any action taking place
between them; but if a little water be added to dissolve them,
chemical action at once ensues, attended with violent effervescence.
Phosphorus and iodine, though both are solids, and phosphorus
and sulphur, will indeed combine when brought together in their
ordinary state; but even in these cases, one or both of the substances are made liquid during the action.
153. Cohesion (for it is this force which unites the particles of
a solid) is therefore always opposed to the action of affinity; and
whatever tends to diminish it in bodies capable of acting upon each
other, facilitates their union.  Heated water is therefore usually
a more powerful solvent than when cold; and salt in fine powder
will be dissolved more rapidly in water, than when in large
lumps.
154. The gaseous state is also unfavorable to the action of
afifnity.  Gases do indeed, in some cases, combine spontaneously,
but, usually, the introduction of an ignited body, the electric
spark, or, in some cases, the influence of the sun's rays, is needed
to cause the action to commence.  Thus, a mixture of oxygen and
hydrogen may be kept for any length of time; but the introduction of flame, or the passage of the smallest spark of electricity,
will cause them to combine instantly, with a powerful explosion.
155. Contact with a third body sometimes will cause a union
of two elements, that would otherwise remain together without
cumnbining.  Thus, the introduction of a piece of spongy platinum
into a mixture of oxygen and hydrogen, produces an explosion in
a few seconds, without-any change being produced in the metal,
QUESTIONS. —What is said, in this connection, of the peculiar state of
a substance, whether it be solid, liquid, or gaseous? Give an example.
153. Is cohesion always opposed to affinity?  154. What is said of the
gaseous state?  HIow may gases that remain in mixture without uniting
afterwards be made to combine? 155. What is catalysis?




AFFINITY.                           141
except that it becomes intensely heated.   This power of some
bodies to produce chemical changes, merely by their presence, is
termed catalysis (fiom the Greek, kata, by, and luo, to unloose).
156. Mechanical action  also  favors the action  of affinity.
Thus, if a piece of phosphorus be wrapped, with a few crystals
of chlorate of potash, in a piece of tin foil or strong paper, a
smart blow  will cause a violent explosion.   Common friction
matches are ignited by friction against sand-paper, or other hard
substance.
157. Relative quantity of matter is the last circumstance we
mention, as affecting the action of this force.  What is meant by
this may be illustrated by the solution of common salt in water.
If equal quantities of the salt are added in succession to the water,
the first portion will disappear in less time than the second, the
second in less time than the third, and so on.  As the relative
quantity of salt contained in solution increases, the action of the
water becomes enfeebled, until full saturation takes place.  If a
large quantity of salt had been added at first, the full saturation
of the water would have taken place much more speedily.
158. Action of Affinity always accompanied by a Change
of Properties. —A  change of properties, to a greater or less
extent, always attends chemical action; but no means are yet
known by which we can predict what any of these changes will be
in any case, previous to making the trial.
Often, when two.bodies unite, the characteristic properties of
both will disappear, and the bodies are said to neutralize each
other.  Thus, the acids are usually sour to the taste, and possess
the power of changing the blue color of some vegetables to red;
while the alkalies are exceedingly caustic to the taste, and change
vegetable blues to green.   Now, when an acid and an alkali
unite, a new substance is formed, called a salt, which is mild to
the taste, and produces no effect whatever upon vegetable colors;
QUESTIONS.-156. What is said of mechanical action?  Give an illustration. 157. What is said of the relative quantities of matter that are
brought to act upon each other?   Give an illustration.  158. Does a
change of properties usually accomlpany chemical action? Can we from
a knowledge of the substances used, predict before trial what the changes
will be?  When are substances said to neutlralize each other? Give an
illustration.




142                      A F FI NITY.
and, indeed, while it possesses many new properties of its own,
it exhibits none of those of either of its ingredients.
159. This change may extend to any or all of the properties
of bodies.  (1.) Bodies, after combining, do not usually occupy
the same space as they did before combination.  Generally, a contraction of volume takes place, but this is not universal.  A pint
of water, added to a pint of sulphuric acid, will not produce a
quart of the mixture; and the same will be found true of water
and alcohol.  When two gases combine, a very great contraction
often takes place; but the result with different gases is very different.  (2.) The changes of form that attend chemical action are
exceedingly various.  The combination of gases may give rise to
a liquid, as in the union of oxygen and hydrogen to form water;
or to asolid, as in the union of carbonic acid gas and ammonia to
form solid carbonate of ammonia; or hydrochloric acid and ammonia, to form  hydrpchlorate of ammonia.  Two solids may, in
combining, form a liquid, as is the case when crystals of sulphate
of soda and nitrate of ammonia are rubbed together in a mortar,
or acetate of lead and alum.  Solids may also, in combining, form
gases, as is the case when gunpowder detonates. Two liquids, by
uniting, may form a solid, as may be shown by pouring sulphuric
acid into a solution of hydrochlorate of lime.  (3..) Chemical
action is frequently attended by change of color.  No uniform
relation has been traced between the color of a compound and that
of its elements.  Iodine, whose vapor is of a violet hue, forms a
beautiful red compound with mercury, and a yellow one with
lead.  The black oxide of copper generally gives rise to green
and blue-colored salts; while the salts of the oxide of lead, which
is itself yellow, are for the most part colorless.
A beautiful instance of the change of color produced by chemical action
is seen in mixing solutions of chloride of mercury and iodide of potassium. The solutions may be made as perfectly limpid as water, but,
upon being mixed, a beautiful vermilion red is produced, by the formation of iodide of mercury.  The color shortly disappears, if either
solution was in excess, by the redissolving of the pr.ecipitate.  About
27 parts of the chloride should be used with 33 parts of the iodide.
QUESTIONS.-159. May the change extend to all the properties of bodies!
Give some illustrations.




C O1 MB I N A T I O N,                  14
ILA W S OF  COMBINATION.-ATO M  C TI  E ORY.
160. Laws of Conmbination.-The relative proportions in,which
substances unite to form the different compounds, is governed by
fixed laws.  There are, however, some apparent exceptions to this
rule, in which bodies seem  to unite in all proportions, without
reference to any law.  Thus, water and alcohol seem  to unite in
all proportions; and the same may be said of water and the liquid
acids.  There are still other substances which seem to combine in
any proportion within certain limits. Thus, water dissolves conmmon salt very readily, but the quantity it is capable of holding in
solution cannot exceed about four-tenths of its own weight.  Below
this limit, the water and salt appear to unite in every proportion.
161. The following are the laws which regulate the composition
of such compounds:I.  Thle com2positio   and  propereties of  compound  bodies are
unchangeable.
By this it is meant (1.) that any compound, while it retains its
characteristic properties, must contain the same elements, united
in the same proportions; and (2.) that while a compound contains
the same elements, united in the same proportion, it must also
possess the same characteristic properties.  Thus, water, a compound of 1 part* of hydrogen and 8 parts of oxygen, possesses
certain well-known properties; now, whenever and wherever a
substance is found, possessing the various properties of water, we
know, from this law that it must be a compound of these two substances, united in the above proportion; and whenever a compound
of these substances, in this proportion, is formed, it must possess
the peculiar properties of water.
A change of properties always necessarily implies a change of
composition; and, conversely, a change of composition necessarily
implies a change of properties.  This law is of universal applicas
tion, except in the case of isomeric compounds, which wnill be
hereafter noticed.
" Parts by weight are always intended, unless it is otherwise exproessed.
QUEGSTIONS. —160. Are the relative proporltiotis in whichi bodbies  coalbine governed by any law?  What example' is nentioned?  -161. Stbito
the first law of combination.  What is water composed of'? Does a
change of properties always imply a clhange of composition?




144                   CO MB IN A T I ON.
II. Whllen any sTlhstancees (as B, C, D, &c.) combbne with a given
quatC'tity of another substance (A), then the numbers which
represent the proportions.in w,hich BC, C, &c., combine with
A, will also represent the proportiolns in which they will combinZe with each other, if such combination be possible.
This law is also of universal application, and examples to illustrate it are abundant. Thus,
8.0 parts of oxygen ]
35 4   "    chlorine
16.0   "    sulphur I combine with 1 part of hydrogen.
127.0   "    iodine
80'0   "    bromine J
It follows, therefore, that if oxygen and chlorine combine, it will
be in the ratio of 8 parts of the former to 35'4 parts of the latter;
and if chlorine and iodine combine, the compound will contain
35'4 parts of the former, and 127 parts of the latter; and so
of the other substances mentioned.
But it is more common, as oxygen unites with nearly all other
substances, to determine the quantities severally of these which
combine with 8 parts of this element.  Thus,
16-0 parts of sulphur   ]
85'4   "    chlorine
1'0  "'  hydrogen
6'0   "    carbon      combine with 8 parts of oxygen.
14'0'   nitrogen
39"1   "    potassium
31'0   "    phosphorus J
Any other substance, having an extensive range of affinity,
might also be selected as the basis of our table, and the results
would be the same. The numbers thus obtained for the various
substances are called their combining numbers, equivalents, or
atomic wei(hts.  It will be noticed that the numbers used merely
express the relative quantities of the substances they represent,
that combine together; it is therefore in itself immaterial what
figures are employed to express them.  The only essential point
is, that the relation should be strictly observed.  Thus, the equivalent of hydrogen may be assumed as 10; but then the number
for oxygen will be 80; that for chlorine 354, &c.  Hydrogen
QUESTIONs. —State the second law of combination. Give an example
in illustration. What are the combining numbers, equivalents, or atomic
weights of substances?




CO IB IN ATIOO N                               14:5
combines with other bodies in a lower proportion than any other
known substance, and is therefore, with propriety, made the unit
by most writers in the English language; but on the continent
of Europe, oxygen is usually considered as 100, and the tables
constructed accordingly.
162. We give below a table of all the known elementary substances, with their combining numbers, or equivalents, the combining weight of hydrogen being considered as the unit.  To find
the corresponding numbers in a table in which the combining
weight of oxygen is made 100, it is only necessary to multiply
the numbers in this table by 12'5.  VWe insert also, in the table,
the symbols by which the elements are represented in chemical
formula, a subject to which the attention of the student will be
called in a future paragraph.
TABLE OF ELEMIENTS, WITH TH1EIR EQUI'VALENTS AND SYMIBOIS.
_,is....uts.
Son-    Equira-                                     Oe Elements.  Sv-  qivaElements.       Iolos.   letis.               Ee nt.ol..    len.ts.
Aluminum..........n.l......... A      13-7.oybdenum.........          46 0
Antimony (Stibium)........   Sb        129'0      Nickel...........................    Ni  29 5
Arsenic.........................  As    750       Nitroen........................  N       140
Barium......................... IM  S'     5     Norium........................  No?
Bismuth......................,  i  208' 0     Osmiu- S.........................   is  995
Boron...........                0      Oxygen................... 109 y..  O      8'0
Bromine.......................  r     80    O  Palladium....................   Pd       53 2
Cadmium......................  Cd      56 0      Peiopium.......................?
Calcium........................    a    20 0      Phosphorus...................            310
Carbon......................... C         6      I Platinum........0..........             99'0
Cerium........................    C     470        otassium  (Kalium) 9........              1
Chlorine........................    1          I5  Rhodiumn..5.................    R       52'2
Chromium....................  Cr         26 7   11uthcui um....................   Lu       52'2
Cobalt...................                2           l......ium.......................  5
Columbium....................    b?       Silicon...........................  Si   213
Copper (Cuprum)............    u             17   Silvc (Argentn)..........  Ag          1080
idyium..................  Di               Sodium  (Ntr.......iu).......... i  N     2 0
E. rbiu.........................   E            Srotium....................             440
Fluorine.....................    F       1  0     Sulphur........................    S    16'0
Glucinum.                                                  um....................   Gt-  7  Taitalum.......1.40..........      1840
Gold (Aurum)................  Asi    198 0        Tellurium........;.4.1........    o      6-11
Hydrog en......................            0      Terbium........................  Tb?
Iodine............           120       Thoiu....................       T        594
Iridium....................I.....  r     99 0     Tin (Stannum)...............             58' 
Iron (Plorrulm)................  Fe      28 0     Titsmum....................    Ti       2510
Lanthanum...................                    I T    a ni (        rm).................... W  9  0
Lanthanl~um.....,.~... ~~~~~    TLa       47'0     Tungsten   (Wolfram).......    02'(
Lead (Plumbum)............  Pb          105       Unium....................       U        0
Lithium..............'..V.nd I                             um....................  V      6S5
R0l an esium.................  A10.~~1C~  1210  U ttrium........................  Y       322
langanese.....................  Xn       280       Zinc.............................. inc  Zn  325
Mercury (5iTydraro'yrln).m   MtI    100'            Zirconsium.....................  Zr     31(0
QUESTIONS.-162.  Alh(lt  are  contained   in   the  table  on  this  pagoe?
Whnat is taken as thle unit?   Ilow  may the numbers given in the table be
converted into  others, in'which the combining  weight of oxygen  is  100?.




I t413C 0 At B I N A M:l)TIO N.
Besides the preeding sixty-two elements, the existence of which
seems to be well established. the discovery of four others has been
announced, which are to be considered as doubtful.  The namres Ari,
diunm, Donarium, ilmeniumn, and Thalium have been given to them.
The equivalents given in the table have been taken chiefly fronm
Dana's table, found in the last edition of his Miineralogy, but are reduced
to the hydrogen standard. In some few instances preference has been
given to Regnault's numbers.
III. I7hen two substcances cornbine in mor'e pro portions tiatn ore,
then, these di',Nrent propor'tions'will always sustain solute simple,
r'atio to each oth&Le-.
To illustrate this law, let A and B be two substances capable
of combining with each other in several proportions;the lowest
proportion in which they coambine will be in the ratio of one
equivalent of each, or I A + I B.  The other compounds they
form will be of the character, I A + 2 B, 1 A - 3 B, I A -+ 4 B, &c.;
that is, 1 equivalent of one substance will be united with 2 or 3,
or some exact number of equivalents of the other substance.
The compounds of nitrogen and oxygen afford an excellent
illustration of the above law.  Thus, the
I st compound contains-Nitrogen, 14, and Oxygen, 8.
2d    "         C         Do.  14, "    Do. 16.
3d    "         "         Do.  14, "    Do.  24.
4tll   "                  D" lo.  14, 6    Do. 32.
5th           "           Do.  14, "    Do. 40.
The law, however, admits of a more general application than these
examples alone would authorize us to expect.  Substances may coinbine-and instances of the kind are not unfrequent-in the ratio of 2
equivalents of the first to 3 or 5, &c., equivalents of the second; and
even more complex ratios than these are known, as 3 equivalents of one
substance to 4, 5 or 7 of the other, but they are not common.  They
may be expressed thus, 2 A + 3 B, 2 A -A   5 B, &c., and 3 A + 4 3,
3 A -- 5 B, -ec.
M15anga'nese and oxygen combine in five different proportions, as shown
below.  The second compound, it will be observed, contains 2 equivalents
of the metal to 3 equivalents of oxygen, while the fifth contains 2 equivalents of the metal to 7 equivalents of oxygen.  Thus, the
1st compound contains-Maanganese, 28, and Oxygen, 8.
21    "  Do.    56, "    Do. 24.
3d    "         "         Do.    28, "    Do. 16,
4th   "       "          Do.    28, "    Do.  24.
5th   "         "        Do.    56, "    Do. 56.
QUESTIsoNs.-State the third law  of combination.  Give an ill,.e
tration.




C       O MBIN AT 1 IO  N  147
These complex ratios may be expressed fractionally; thus, the
expressions 2 A +  3 B, 2 A + 7 B, aund 3 A -+ 4 B, are equal
respectively to 1 A + 11 B, 1 A -- 38  B,   1A + 4B.
in the lmanganese series above given one place, it will be seen,
is wanting, between the fourth and fifth, which may hereafter be
filled by further research.
IV.  Y/V'e equfvctclet of a comgpoun,,d substance e:ill always b
eqeual to the suna (f the ezqu'ivalett's of! the stbsltaaces whlicl
comlpose it.
Thus, water is composed of 1 equivalent of ovygen 6, and 1
equivalent of hydrogen 1; its comlbining number, or equivalent, will therefore be (8 + I =)9.  So, also, sulphuric acid,
which contains 1 equivalent of sulphur (16) and 8 equivalents
of oxygen (8 x 3 -94), has for its equivalent 40.
The same is true of all cormpound bodies, as hydrochloric acid,
which contains 1 equivalent of chlorine, 354-, and I equivalent
of hydrogen, 1, giving for its equivalent 36'4.  The equivalent
of potassium  is 8391, and as this combines with 8 of oxygen to
form  potassa, the equivalent of the latter is 47'1 =   9'1 -+ 8.
Now, when any comupound substances unite with each other, one
equivalent of one substance combines with one, two, or three
equivalents of the other substance, precisely as in the case of the
elements.   Thus, the hydrate of potassa, composed of potassa
and water, contains exactly I equivalent, 47'1 parts of potassa
and 1 equivalent, or 9 parts of water; and its equivalent is
56 1-  47-1 + 9.  So the sulphate of potassa is composed of 40
parts of sulphuric acid and 47'1 parts of potassa, having for its
equivalent 87l; and the nitrate of potassa, composed of nitric
acid and potassa, contains 54 parts of the acid and 47 1 parts of
potassa, its equivalent being 101.1.
V. The quanltities of gaseoeus substances, esti.>ated by mieasure,
u-hich en/er into combinatiol, bear sceme simple reatio to eacl7
other, andc also the quantities of the resulting comnpounds, con,
sid(ered e  as: g(aseous, bear sonme simZle rctio to the sunz of the
volumze of the ingredients.
Water, we have seen, is composed of I equivalent (estimated
Dy weighlt) of' each of its elements, hydrogen and oxygen, which
QuEsTrioNs. —S tate the fourth law.  What illustration is given?




148                   Co  B I NATIONo
are gases; but if we measure them  before causing them to combine, we shall find that 1 pint of oxygen will unite with exactly
2 pints of hydrogen.  If we use more oxygen than this in proportion, a part of it will remain after combination; and if we use
less, a part of the hydrogen will be left.
So, a pint of chlorine will combine with exactly a pint of
hydrogen, and a pint of nitrogen with exactly 3 pints of hydrogen form  ammonia; and so of other gaseous substances, or any
capable of taking this form, as sulphur or mercury.
If we represent the combining volume of oxygen by 1, as is
usual, then the combining volume of each of the following sub'
stances, viz., hydrogen, mercury, nitrogen, chlorine, iodine, and
brominc, will be 2.  Phosphorus and arsenic have the same
combining volume as oxygen, 1; -while that of sulphur is i.
These numbers are determined by experiment precisely as the
numbers representing the proportion in which substances combine
by weight.
It follows from  the above that there must be a close relation
between the atomic weights, the combining volumes, and the
densities of gaseous substances.  The atomic weights of oxygen
and hydrogen, we have seen, are as 8 to 1, while their combining
volumes are 1 to 2; it follows, therefore, that the density of
oxygen must be to that of hydrogen as 16 to 1.  So the atomic
weights of chlorine and hydrogen are as 35-4 to 1, but they conmbine in equal volumes; their comparative densities must therefore be as their atomic weights, that is, as 35'4 to 1.  In fact, in
all cases in which the gases combine in equal volumes, their
densities respectively must be as their atomic weights..And in
the cases of those which do not combine in equal volume, the
simple ratio of the combining volume being observed, it is easy to
calculate their relative densities from their atomic weights. Thus
the combining volumes of hydrogen  and sulphur vapor are,
respectively, 2 and -, and their atomic weights 1 and 16; the
Q sJErSTONS. —State the fifth law of combination. What illustration is
given? Is there any relation between the atomic weights, combining
volumes, and densities of gaseous bodies?  How is this illustrated by
reference to oxygen and hydrogen?  When the combining volumes and
atomic weights of gases are given, may their relative densities be calcu
lated? How is this illustrated by reference to sulphur and hydrogen?




C 0 G r3 I     N   T I.                     149
density of sulphur vapor, compared with that of hydrogen, vmust
therefore be 96, which is very nearly the saume as it is fbund to be
by direet experiment:t
It is customary to refer the densities of gaseous bodies to that of atmospheric air (at a given temperature and pressure) tiaken as unity; and
we have then, as the result of very many experiments, the numbers in
the table below.   These numbers will be of use hereafter.
One volume of Air weighs.......... 1'000   One vol. of Iodine vapor weighs........ 87 16
"         liydroogen weighs *069        "  Bromiinue   "           5'400
"     "    Oxygen'   1'106'    "    ercury "    "           6'976
Niltroge    "'971    "   "  Sulphur   "           6'654
"   Chlorine'   2'440    "   "  Phosphorus vapor weighs 4'326
_ _"   "  Arsenic    4"  "6  10'370
By the second part of the fifth law, as enunciated above, the combining
volumes of compound gases will bear a simple ratio to the sums of the
volumes of their respective ingredients.  In some cases, no change of
volume takes place when gases combine, as in the case of chlorine and
hydrogen, -where equal volumes combine and produce two volumes of
hydrochloric acid; but more frequently a change of volume is observed,
us in the case of vaipor of water, which is composed of 1 vol. of oxygen and
2 vols. of hydrogen condensed to 2 vols. of steam.  So amimlonia is a
compound of 1 vol. of nitrogen and 8 vols. of hydrogen condensed into 2
vols. oL' amlmoniea.
The density of a compound gas may therefore often be calculated from
the density of its ingredients and the change of volume known to take
place in combination.  Thus, in the case of water, which we have seen
is composed of I vol. of oxygen and 2 vols. of hydrogen condensed into 2
vols. of stestz,
l vol. of Oxygen                    1 1'i06
2        H dHydrogen =_' X 069 =3 0'188'2  Steam G=                        1'24'4
One-half of this sum, 1'244, or 06'22, is therefore the weight of 1 vol.,
or, in other words, the density of steam.  This is the same as found by
dliect experiment.  So in the case of a:mmonia, mentioned above,
3 vols. of Hydrogen _ 3 X  069 =  0.207
1   "    Nitrogen  -                0'971
Ammonia =                 1178
As this forms 2 vols. of ammonia, one-half of the sum, 1.178, or,'589
is the weight of 1 vol., or the density of this compound gas.
We add one more instance, by way of illustration.  HTydrosulphuria
QuESTIONs.-Does a change of volume sometimes take place when
ga}ses combine?  How is this illustrated in the case of water?  May the
density of a comlpound gas be calculated from the densities of its ingredients and the change of volume that takes place when they combine.3:




150                  ATOMIC THEORY.
acid is a compound of a single equivalent of hydrogen and sulphur, the
combining volume of the former being 1, and that of sulphur 1. Now,
1 vol. of Sulphur vapor 6- 654
6       H" hydrogen =  6 X 0.069-   -414
6   "   Hydrosulphuric acid  =-  7068
As the 7 vols. in combining form but 6 vols. of the gas, the sum 7 060
is to be divided by 6, giving us for the density of hydrosulphuri
acid, 1'178.
Some substances, as carbon, cannot by any means yet known be
obtained in a state of vapor; still we may with some certainty calculate
what the density of their vapor would be if vaporization were possible.
Thus, in the case of carbon, assuming that carbonic acid is composed of
1 volume of carbon vapor and 2 volumes of oxygen, the whole condensed
in 2 volumes, we have2 vols. of Carbonic Acid      2 x 1.524  3.04-8
2        Oxygen (subtract) - 2 X 1.106 = 2.212
1        Carbon vapor      =                 836
One volume of carbonic acid we know contains 1 volume of oxygen,
but whether the carbon vapor should be taken as 1 volume or only - of a
volume, we have no means of determining, except the analogy of other
compound gases, and therefore our assumption above may not be correct.
It is possible that carbonic acid may have a more complex organization
and carbon a very different combining volume.
The combining volume of oxygen being taken as 1, those of all the
elementary bodies capable of assuming the gaseous form are 1, 2, or 4,
except that of sulphur, which is 3. Of the very many compound gases
whose combining volumes have been determined, that of nearly every
one is either 2 or 4.
163. Ato lic Theory.-It will be observed that nothing theoretical pertains to the above laws, which are simply the enunciation of well-determined facts; but such striking results, obtained
by experiment, naturally incline us to inquire for their cause;
and, in the absence of positive proof, the atomic thoeory has been
proposed for this purpose.
This theory assumes that every simple substance is an aggregation of atoms (9), by which is meant the particles in their
smallest state of division; and that the atoms of the same substance are all precisely of thle same weight.  It assumes, also,
that when simple substances combine to form  compounds, they
unite by atoms; that is, one atom of one substance combines with
one, two, three, &c., atoms of the second; or two atoms of the
QUESTr0N.-168.  Explain the atomic theory.




N O M EN C LA T U R E.                  151
first combine with three, five, or seven, &c., atoms of the second,
&c. As these atoms are supposed to be absolutely indivisible,
there can, of course, be no such thing as half an atom; and all
compounds must be of the form 1 A + 1 B, 1 A + 2 B, 2 A + 3 B,
&C.  The absolute weight of an atom of any substance has never
been determined, but it is assumed that the equivalents of the
various bodies do actually express their relative weights; the term
atonzmic weight is therefore often used as synonymous with equiva
lent. Thus, the atomic weight of oxygen is said to be 8, and
that of hydrogen, 1, &c.; and water is said to be a compound of
one atom of oxygen and one atom of hydrogen; while sulphuric
acid is a compound of one atom of sulphur and three atoms of
oxygen-and so of other compounds.
Whether the assumptions of this theory are strictly true, we
may never be able to determine experimentally, but, it is readily
seen, that if they are a correct expression of what really takes
place in nature, they afford an elegant explanation of the reason
of the above demonstrated laws.
164, Specific Heat of Atoms.-The quantities of heat required to raise
the temperature of equal weights of different bodies by a given number
of degrees (59), varies greatly, according to their nature; and the numbers expressing these quantities, having reference usually to vwater as
tihe standard, express also the capacities for heat or the specific heats of
these bodies.  Between these numbers no special relation can be traced;
but if we make the calculation in reference, not to equal weights, but to
al/onic weights, then in some nine or ten of the elementary bodies the
specific heats are found to be the same, while several others have a specific
heat twice or four times as great.
It has been supposed that-the specific heat of the atoms of all bodies
may be the same-a view which is favored by the facts above mentioned-but most bodies, both elementary and compound, depart so
widely from this supposed law that its existende is altogether improbable.
NOMENCLATUR E  OF CHE M IS T RY-S Y M B OLS.
165. iomenclature.-Chemistry possesses a more systematic
nomenclature than any other branch of natural science; and a
thorough knowledge of it, at the very beginning of his studies, is
QUESTIoNs.-Does this theory account satisfactorily for the preceding
laws of combination?  164. Is the specific heat of the atoms of all
bodies the same? 165. What is said of the nomenclature of chemistry T




1.52                NOMENCLATUR E.
very important'to the student.  This nomenclature is framed in
reference to the composition of compounds, and is so contrived
that the names of all compounds shall indicate the substances
of which they are composed.
166. Elementacry slbstances being composed of only one kind
of particles, of course the above remark does not apply to them:
their names are mere names; that is, mere sounds connected by
usage with the things signified.  Yet, in the case of newly discovered elements, names have in some instances been given that
indicate some important property of the substance.  Thus, oxygen
(from  the Greek oxus, acid, and gennao, to produce) was so
named, because it was supposed to form  a necessary part of all
acids; and hydrogen (from  hudor, water, and gelnao), because
it was known to enter into the composition of water.  So chlorine,
being of a greenish color, received its name, in consequence, from
the Greek chloros, green; and bromine was so called from its
offensive odor, from bronmos, fetid.  Potassium and sodium are so
named, because they form the basis, respectively, of potassa and
soda; and glucinum (from glukus, sweet), because of the sweet
taste of some of its compounds.  Other elementary substances
of recent discovery have been named in like manner; but all
simple substances which have been long known retain their
ancient names.  Thus, gold, silver, lead, copper, sulphur, carbon, are names of well-known substances, and they are retained
in chemistry; but they contain, it is evident, no descriptive
meaning.
167. But it is to compound bodies that the nomenclature
especially applies; and, as above intimated, its design is to
indicate their composition by their names.  For this purpose,
when two substances only are combined in a compound, a part
of the name of one, with the termination ide, is made use of;
while the other is expressed in full. Thus, oxygen forms oxides;
chlorine, chlorides; bromine, bromides; sulphur, sulphurides, or
sulphides; carbon, carbonides, or carbides, &c., of the other substance, the name of which is fully expressed; as oxide of iron, oxide
QuESTION.-In   reference to what is this nomenclature framed?
16B. What is said of elementary substances?  167. I-ow is the ternination ide used? Give an example.




N OMENCLATURE.                         153
of sulphur, chloride of hydrogen, &c. Formerly, usage required us
to employ the termination idte for the compounds of all the elementary substances except those of carbon, sulphur and phosphorus,
with which, without any apparent reason, another termination, qret,
was used.  Thus, we have been accustomed to say sulphuret of
carbon, and not sulphide; phosphuret of calcium, and not phosplhide; but a change in this respect has taken place, and the
termination ide is alone made use of, as sulphide of carbon, &c.
When two elements unite in more than one proportion, numeral
prefixes from the Greek or Latin are used to designate them; as
protoxide of copper (from protos, first), and deutoxide (dczeteros,
second) or binoxide (bis, twice) of copper.  The first of these
compounds contains one equivalent of oxygen, united with one
eq. of copper, while the second contains two eq. of oxygen, combined with one of copper.  So the teroxide (tertio, third) or
tritoxide (tRitos, third) of nitrogen, is a compound of three eq.
of oxygen and one eq. of nitrogen.  The same rule is observed
wvith regard to the compounds of other substances as protosulphide
and bisulphide of mercury, bicarbonide -of sulphur, terchloride
of gold, &c.  The prefixper is often used to indicate the highest
compound known, as peroxide of lead; and the prefix scsqui
implies that two eq. of one of the substances is combined with
three eq. of the other substance; as sesquioxide of iron, which
contains two eq. of iron and three eq. of oxygen.  Generally, the
electro-negative element is expressed first, as chloride of sulphur,
and not sulphide of chlorine; but this rule is not universally
followed.
163. Most of the compounds above described, which may properly be called binary, or bielementary, as being composed of two
elements, are also capable of combining together, and forming
other more complex compounds, usually called salts.  In considering the relations they sustain to each other, they are usually
divided into the two classes of acids and bases.  The acids are
QUESTroNs.-How was the termination uret formerly. used?  When
two elements combine in more'than one proportion, how are tile different
compounds indicated? For what is the prefix per used? Which element
is usually expressed first?  168. May compounds combine to form other
more complex compounds?




154                 N O  E N CL AT U RE.
generally more or less sour to the taste, change vegetable blueg
to red, and are electro-negative in relation to the other class;
while the bases are electro-positive, and restore the blue colors
which have been changed to red by acids.  Some of the bases
are soluble in water, and are exceedingly acrid and caustic.
A  large proportion of all the acids are oxides, and are therefore called oxygen acids, or oxyacids; but many contain hydrogen,
and are called hydracids.  So, when a sulphide possesses acid properties, it is called a sulphur acid.
As most of the acids belong to the first class, or are oxyacids,
special reference is had to them in the nomenclature; and they
are named by using the termination ic or ous in connection with
the name of the substance with which the oxygen is combined to
foirm the acid, the termination ic being used for the acid containing most oxygen, when there are more than one formed from the
same substance, and the termination ous for the one containing
least. Thus we have sulphuric and sulphurous acids, the former
of which contains more oxygen, and is a more powerful acid than
the latter.  When there are more than two acids formed fiom the
same substance, the prefix hypo (hupo, sub, or under) is used iu
connection with the name of one or the other of the two already
described, as the case may require.  Thus, we have hlyposulphuric
acid, which contains less oxygen than the sulphuric, and the
/iyposulpkurous, which contains less oxygen than the sulphurous.
When a compound, not containing oxygen, possesses acid properties, a part of the name of one of the substances is used as a
prefix to the name of the other substance, to form a name for the
acid. Thus, hydrochloric and hydrosulphuric acids are compounds
of hydrogen with chlorine and sulphur respectively.  So ch!oriodic
acid is a compound of chloride and iodine.  Some writers are
particular to take the prefix from  the name of the negative element, and say chlorohydric, sulphydric, &c.; but there is no good
reason for such a distinction   If no prefix is used, the acid is
understood to be an oxyacid, as nitric acid, which is composed
of nitrogen and oxygen.
QUESTIONs.-How are acids generally characterized?  Ilow are bases?
1What are oxyacids? What hydracids? HIow are the oxyacids named? 
Tlow is the prefix hiypo used? Give examples. When an acid compound
does not contain oxygen how is it named?  Give examples.




SY I BO LS.                         155
169. The  salts are compounds of the acids with bases, as
Glauber's salt (sulphate of soda), which is composed of sulphuric
acid and soda.  Names of the salts are formed by changing the
termination of the name of the acid from'Ic into ate, and from ous
into ite, and expressing in full the name of the base.  Thus, suiphuric acid, combined with bases, forms sulphates; carbonic acid,
carbonates, &c., of the bases with which they may be severally
united; as sulphate of lime, phosphate of alumina, hyposulphate
of soda, &e.  So sulphurous acid forms sulphites; nitrous acid,
nitrites; hyposulphurous acid, hyposulphites, &c., of the various
bases.
Many of the metallic oxides serve as bases of salts, but in
expressing them  (the salts), the word oxide is often omitted;
thus, sulphate of iron is the same as sulphate of the oxide
of iron.  If a higher oxide than the protoxide forms the base
of a salt, it is usually expressed in full; thus, we have the
sulphate of the sesqui-oxide of iron.
170. Acidc or super salts are such as contain an excess of acid,
while basic or sub salts contain an excess of base; salts that contain no excess of either acid or base being called neutral salts.
A bisulphate contains twice, and a tersu7phate three times as much
acid as a sulphate.  Prefixes derived from  the Greek numerals
are often used to express the excess of base in the subsalts; as
cinitrate of lead, a salt which contains 1 equivalent of nitric acid
and 2 equivalents of oxide of lead.  The same thing would be
expressed by calling it bibasic nitrate of lead.
The above explanations will serve to illustrate the fundamental principles of the present nomenclature; but it is admitted that it applies
but partially to the more complex chemical compounds, which, however,
are not of frequent occurrence.
171. Chemical $ymbols.-Instead of writing the full name of
substances, it is often  convenient to substitute  abbreviations,
which are called the symbols of these substances.  For a simnle
substance, the first letter of the Latin name is generally used;
but when there are two or more having the same initials, some
QIUESTIONS.- 169. What are salts?  How are the salts named? What
is said of the names of salts which have metallic oxides for their bases?
1 70. What are acid or super salts?  What basic or subsalts?  171. YWhat
are chemical symbols?  How are they formed?




156                      SYMBOLS.
other letter of the name is connected with the initial, in the symbols of all except one. Thus, 0 stands for oxygen, and Os for
osmium; B for boron, Ba for barium, and Bi for bismuth; P for
phosphorus, Pd for palladium, and Pt for platinum, &c.  In the
table on page 145, the symbols in general use for all the simple
substances are given.
These symbols indicate single equivalents of the substances
they respectively represent; and to indicate two, three, or more
equivalents, a figure is placed before the symbol, as the coefficient in
Algebra or a little below it at the right.  For instance, S signifies
a single equivalent of sulphur, 2 S, 3 S, or S2, S,, &c., two, three, &c.,
eq.; and 4 0, 5 C, or 04, C,, four eq. of oxygen, five eq. of carbon, &ce
To indicate that several substances are combined, their symbols
are simply written side by side, as HO, or with a comma between
them, as H, 0, or with the plus sign (+), as H + O; all of which
expressions represent a single equivalent of protoxide of hydrogen,
or water.  The comma and the plus sign are generally made use
of only when the expression is somewhat complex; thus, NOI, is
the symbol for nitric acid, KO that for potassa, and KO, NO5, or
KO + NO5 that of nitrate of potassa.  Sometimes the plus sign
is used when the substances between which it is placed are not
combined, but only mixed.  Generally, in writing the symbols
df compounds, we express the electro-positive element first, as
HO, KO, and not OH1, OK, hydrogen and potassium  being the
positive elements of these compounds. So also we write KO, S03
for sulphate of potash, and not SO,, KO.
It is to be particularly observed that small figures, placed at
the right of letters, apply only to the ones to which they are
attached; but large figures, placed at the left, like algebraic
coefficients, affect all that follow them to the next comma or
plus sign.  Thus, PO, represents phosphoric acid; NaO, soda;
NaO,PO,, phosphate of soda; 2(NaO,PO0), two equivalents of
the same phosphate of soda; but 2NaO,PO, indicates a single
eq. of bibasic phosphate of soda, which contains two eq. of soda,
united to one of acid.
In consequence of the frequent occurrence of the double equivalent, it is often expressed by. drawing a line under the symbol
QUESTIONS.-HOW are compounds expressed by the use of these sya!bols? How is a double atom often expressed?




SYMBOLS.                              157
of the single equivalent, or by a black letter.  Thus, Al signifies
an eq. of aluminum, and Al or Al, two equivalents. A1O, or
A103 is the symbol for the sesquioxide of aluminum or alumina,
and means the same as A12,,.  As oxygen forms an extensive
list of compounds, simple dots are often used to indicate its presence in them; the above symbol for alumina would then become
L:.=A1203.  Other examples follow the same rule.
Combinations of these symbols, according to the principles
above explained, are called  Chemical Formnzula; and the great
advantages of their use, in expressing forciblycomplicated chemical changes, will be fully seen as we proceed.
172. Isomerism-Polymerism.-Isomeric compounds (161) are such as
have the same ultimate composition, but differ from each other in some'
or all of their sensible properties.  The term is derived from  the Greek
isos, equal, and meoros, part.
Thus phosphoric acid, PO,, is known in three different conditions, as
ordinary, pyro, and metaphosphoric acids, the first of which is capable of
saturating 3 eq. of a base, as soda; the second, 2 eq. of base, and the
third only 1 eq.  In other properties, also, this acid in its different
states exhibits a diversity, but its composition in the different states is
the same.  There are other examples of the same kind
Polylneric compounds have the same ultimate composition, but differ
in their properties; and their equivalents are multiples or sub-multiples of each other.  Olefiant gas, C4H4, oil gas, Cells, and cetine,
C32H3,,, form a series of this kind, having the same elements in the same
atomic proportion, but the equivalent of the second being twice that
of the first, and one-fourth of that of the third.  So, oil of turpentine,
CoH, and oil of lemons, C,2oHT6, sustain to each other a similar relation.
Many other examples are known.
173. Allotropism. —This term  is used to designate the different conditions in which a substance is sometimes found, as it regards the
chemical action of other bodies. Thus, iron, in its ordinary state, is
readily dissolved by nitric acid; but if, before immersing a piece of iron
wire in this acid, one end of it be heated to redness, or if it is connected
with the positive electrode of a galvanic battery, or if it be immersed in
the acid in contact with a piece of platinum,-in either of these cases,
the acid fails to act upon it.  So, if an aqueous solution of chlorine be
prepared in the dark, it may be kept in a dark place without change for
a long time; but if the sun is permitted to shine upon it a few seconds,
decomposition will commence, hydrochloric acid will be formed in the
water, and bubbles of oxygen rise to the surface.
Many other substances exhibit similar peculiarities, and are said to
exist in different allotropic states.
QUESTION.S.-172. What are isomeric compounds?  What examples are
given?  What are polymeric compounds?  Give an example.  173. What
does the term allotropism designate?
14




158                 C R Y ST A L O G R AP H Y.
CRYSTALO GRAP IIY.
174. The particles of liquid and gaseous bodies, as they unite
to form  solids, sometimes cohere together in an indiscriminate
manner, and give rise to irregular, shapeless masses; but more
frequently they attach themselves to each other in a certain
order, so as to constitute solids possessed of a regularly limited
form. The process by which such a body is produced is called
cr,/stalization; the solid itself is termed a crystal; and the
science, the object of which is to determine and classify the
forms of crystals, is crystalogeraphy.
175. Mode of producing Crystals.-Nature presents us with
an abundance of crystals in the mineral kingdom, but they may
also be produced artificially by several processes.  The essential
condition is, that the particles of the substance to be crystalized
should be free to move among each other, which is accomplished
by bringing it into the liquid state by solution, or by melting it.
Alum forms beautiful octahedral crystals, by making a saturated
solution in warm  water, and allowing it to cool
slowly.  If a small tree be made of copper wire,
and its branches immersed in such a solution while
cooling, on removing it, the part immersed will be
covered with a multitude of small shining octabeOctahedron.   drons, like fruit.  If the solution be allowed to
stand after it has become cold, the crystals will gradually increase in size as the water evaporates.  Common salt, blue and
green vitriol, and many other substances may be crystalized in a
similar manner.
Crystalization by fusion is also very common.  If a quantity
of sulphur be melted and allowed to cool slowly, upon breaking
QUESTIONS.-174. Do the particles of bodies sometimes unite so as to
form solids of a regular form?  What are such solids called? 175. lWhal
is the essential condition for the formation of crystals? What is tLo
form of the crystals of alum?




CRYST ALOGRA PHY.                         159
the crust and pouring out all that remains
liquid, a  mass of crystals will be  found'within, shooting in every direction, as represented in the figure.
The crystalization of many substances, as
sulphur, corrosive sublimate, iodine, &c., may
also be produced by sublimation.              Crystalization of Sulphur.
176. Crystalization in Solids. —Even in solids, crystalization
sometimes takes place.  Copper wire which has been long kept is
said often to lose its tenacity, in consequence of cubic crystals of
the metal gradually forming in it.  When sugar is melted and
allowed to cool, it forms a hard, transparent mass; but by keeping some time, it gradually becomes opaque, and exhibits the
ordinary white color and crystaline structure of refined sugar.
Common "lemon candy," which is usually sold in small flat
pieces, an inch wide and four inches long, is beautifully transparent when first formed; but after a f6w hours, crystalization
commences in numerous points, and gradually extends through
the mass, which now becomes opaque; and at the same time its
flavor is improved.
177. Water of Crystalization. -  Many substances, in  crystalizing, absorb a large quantity of water, called their water
of crystalizafton, which  is essential to the existence of the
crystals.  It sometimes amounts to half their weight.  When
exposed to the air, the water often evaporates, and the crystals
fdll to powder.  They are then said to efgforesce.  Glauber's salt
affords a noted instance of this.
All substances are limited in the number of their crystaline
forms. Thus, calcareous spar crystalizes in rhombohedrons, fluor
spar in cubes, and quartz in six-sided pyramids; and these forms
are so far peculiar to those substances, that fluor spar never crystalizes in rhombohedrons or six-sided pyramids, nor calcareous
spar or quartz in cubes.  Crystaline form  may, therefore, serve
as a ground of distinction between different substances.  But the
composition of substances having the same form is not necessarily
QuESTIoNs. —How may sulphur be crystalized?   176. May crystali
zation take place in solids?   Give an example.  177. What is water
of crystalization? When does a substance effloresce? Are substances
limited in the number of their crystaline forms?




160                 CRYSTALOGRAPIIHY
the same, nor are the crystaline forms of the same substances
always identical.
178. Primary Forms. —The total number of cryst.aline forms
is unlimited; but it is found that all the more complex may be
derived from thirteen of the more simple forms, which are therefore called primnary or findamentalforms. These readily arrange
themselves (see.Dana's excellent work on lfitneqralog3y) in six
classes or systems, which are characterized by the comparative
length and position of certain imaginary lines, supposed to be
drawn through them, called axes.
i. Mlonometric,ys-tem. —This system  includes the cuze, A,
the regular octahedron, B, and the rhombic dcodecalcedron, C; all
of which have three equal axes at right angles with each other.
HIence the name, from monos, one, and mzetqron, measure.
The cube, A, is a solid with six equal square faces; its axes, a, b, c,
A9                 LA
-__ —---— _ —---— _ —— _ —--
Cube.
are three lines, supposed to connect the centres of opposite faces. All
its solid angles are similar, as also its edges.
The regular octahedron, B, is contained under eight equilateral triangles,
Octahedron.
QUESTIOrS. —178. What are primary forms?  How many of these are
there?  In how many classes do they arrange themselves?  What are
the forms of the monometric system? What is said of the axes of the
~,s.s of tli s system?




CR Y ST ALOGR AP HY.                        161
and its axes, a, b, c, connect opposite solid angles.  All its angles and
edges are similar.
The rhombic dodecahfedron, C, is bounded by twelve equal rhombs; At
has two kinds of solid angles, one kind, as m, n,, which is composed of
four acute plain angles, and another kind, as ni, n, which is composed of
Dodehecadron.
three obtuse plain angles.  The axes, a, b, c, connect the opposite acute
solid angles.
Comparing these three forms with each other, it will be seen that the
axes are the same in all, being equal in length, and making right angles
with each other. If any one of them is supposed to be placed within
another, the axes of the two will entirely correspond throughout.
2. Dbinetric Systen.- This system  includes only two forms,
the square prisz, and the sguare octahedron.  These solids have
three axes, at right angles to each other, but they are of two
kinds, as indicated by the name, from  dis, twice, and mnetron,
measure.
The square prism, D, is bounded by six faces, two of which, O, 0,
D'0 0
Square Prism.
called the bases, are squares, but the four other faces are rectangles,
the height of which may be either greater or less than the base. The
QuEsTioNs.-What are the forms of the dimetric system?  How are
the axes of the forms of this system characterized?
14*




162                   CRY S TALO GRAP HY.
axes, a, b, c, connect the centres of opposite faces, as in the cube;-the
two last named, b and c, are always equal, but the other, a, sometimes
galled the prismatic axis, is variable, and may be either longer or shorter
than the others.  Its solid angles are similar to
each other, but the edges are of two kinds, the
basal and the lateral.
The square octahedron, E, has for its faces eight
equal isosceles triangles.  The axes connect oppo
site solid angles, and correspond in every respec
with the axes of the square prism.  The twi
therefore properly constitute one system.  In describing this solid the variable axis, a, is always
supposed to be vertical, the other two being horizontal.  It has two kinds of edges, and two kinds
Square Octahedron.   of solid angles.
3. Tierlmetric Systemn.-The  three solids of this system  are
the rectacsgular _prism, F, the right'rhombic prism, G, and the
rhobonzc octahedron, H.    The name is from  tris, trice, and
metron, measure.  These forms have three axes intersecting at
right angles, but all are variable, no two being equal.
The rectangular _prism, F, has six faces, all of which are rectangles:its three axes, a, b and c, connect the centres of opposite faces, and
intersect each other at right angles, and are variable, as to their length.
Its solid angles are all similar; but its edges are of three kinds.
F
*     -b ----- ---
Rectangular Prism.      Right Rhombic Prism.    Rhombic Octahedron.
The right rhonibic prism, G, has six faces, two of which are equal
rhombs, and constitute the bases, while the four lateral faces are rectangular. Its three axes, a, b and c, intersect at right angles, and are
variable; the first, a, connecting the centres of the bases, but the other
two, b and c, being drawn between the centres of opposite lateral edges.
Its solid angles are of two kinds and its edges of three.
The rhombic octalzedron, H, has eight faces, which are scalene triangles; its axes, three in number, a, b and c, unite the apices of oppoQuESTIONS.-What are the forms of the trimetric system?  What, is
said of their axes?




CRY s T AL 0 GR AP II Y.                    163
site solid angles, and in every respect correspond to the axes of the two
solids last described.  This solid may be considered as composed of two
pyramids with rhombic bases, united base to base.
Comparing the three forms of this system, we see that their axes are
identical; comparing the systems now described with each other, we
find that they each have three axes intersecting at right angles in the
centre of the solids; but in the first, or submonometric system, all are
equal; in the second, or dimetric, two are equal, and the third variable;
while in the third, or trimetric, all are variable.
4. Monloclnic S'ystcm.-This system  includes two forms, the
ri?,]ht 1hoamboimal prismn, I, and the obliq~ue rholon&b/c prism, J,
which have three axes, a, b and c, two of them  making  their
intersections at right angles, but the third  is inclined.   The
name is from  mzossos, one, and clino, to incline.
The right rhonmboidal prism, I, has two rhomboidal bases, upon one
of which in this figure it is supposed to stand, the other four being
rectangles.  The axes connect the centres of opposite faces, of which
a and b, a and c, intersect at right angles, but b and c are inclined to each
other.
7T
I J_ 1
Right Rhomboidal Prism.   Oblique Rhombic Prism.   Right Rlhomboidal Prism.
The obligue rhlonbic prism, J, has its faces rhombs, and its four lateral
faces parallelograms.  Its vertical axis, a, connects the centres of the
bases, but the two lateral axes, b and c, are drawn between the centres
of the lateral edges.  The last two intersect at right angles, and the
vertical axis, a, makes a right angle with b, but is inclined to c.
To compare these two forms, the right rhomboidal prism, I, must be
placed upon one of its rectangular faces, as in K, making the axis, a,
vertical; the faces m mu and n n, in I, will become respectively m m and
n iz in K, and all the axes of the two will correspond.  If now, when in
QUESTION.i-Compalring now the axes of the forms belonging to the
three preceding systems, in what do they differ?  What forms are
included in the monoclinic system? What is said of their axes?




164:                C R Y S T A LOG (R AP H Y.
this positiou, all the lateral edges are removed, as in K/, we shall have
the oblique rhombic prism, represented within the rhomboidal, as in
K'                             L
Right Rhomboidal Prism.   Oblique Rhomb'l and Right Rhomb'l Prisms
figures K/ and L; the crystal in the last figure being supposed in the
same position as in I.
5. Triclinic System.-A  single form  only, the oblique 7honmboidal prism, 3M, belongs to this system.  It
is bounded by six faces, but only those
directly opposite each other are equal.  Its
basal faces are rhomboids, and  its lateral...             edges are inclined to the plane of its base.
Its three axes are unequal, and no two of
them  intersect at right angles.  The name
Oblique Rlhomboidal Prism. iS from tris, thrice, and crino, to incline.
6. ]texa1gonal System. —This system  includes the r'hombolhed.ron; N and 0, and the hexagonal prism, T.  These solids have
Rhombohedron.               Rhombohedron.
four axes, one of which, called the vertical axis, is perpendicular
QuEsrIoNs. — What solid only belongs to the triclinic system?  What
is said of the axes of this form?  What are the forms of the hexagonal
system? How many axes have they, and how are they drawn?




CRYSTALOGRAPIHIY.                             165
to the other three, called the lateral axes.  These latter intersect
each other at angles of 60~, and are equal.
The rho~mbohedronz is of two kinds, the obtuse, N, and the acute, 0;
in each all the six faces are equal rhomebs, and in each there are two
Ecilid angles, diagonally opposite, which are formed by three equal plain
anugles.  Between these, one axis, a, is drawn, called the vertical axis;
nrid in describing the solid this is always supposed to be in a vertical'7    0              0
Rthombohecdron.
position.  The other three axes, b, c and d, unite the centres of opposite
lateral edges.
Of the twelve edges, six (three above and three below) are connected
with the extremities of the vertical axis around which they are symmetrically placed.  The other six, called the lateral edges, are also
situated around this axis symmetrically, and at equal distances from it.
This is readily seen by looking downward upon a crystal of this form
when in position, a section through the centre perpendicular to the
vertical axis being plainly a regular hexagon, as in the figure P.
Section Rhombohedron                Secondaries.
By replacing the six lateral edges by planes parallel to the vertical
axis, a, a hexagonal prism, terminated by three-sided pyramids, is pro(laced, represented in R.  Removing  in a similar manner the lateral
solid angles, we have the form, S, which is essentially the same as the
QUIcSTIONS.-oIIw is the hexagonal prism  terminated with three-sided
pyramids produced from the rhombohedron?




1l66                CRY ST ALOG RAPII Y.
last except the terminal pyramids; and by a removal of the terminal
pyramids a regular hexagonal prism, T,
2'                U        will be found.
In a similar manner, the rhombohedron may be derived from the hexagonal prism, by a replacement of the
-  /I I   1        11|,Ialternate basal edges of the prism;
first in the form represented in U:
and the replacement being continued'4t. i           until the faces of the original prism
are obliterated, the resulting solid will
Hexagonal Prism.        be the rhombohedron.
179. Secondary Forms.-Secondary forms are derived from
the  primary, by regular, systematic changes or modifications
upon the angles or edges.  Their number is unlimited.
A general discussion of the laws of these modifications cannot be here
introduced, and only a few further illustrations.  The connection between
the different forms of each of the six systems, it is believed, has been
made plain; and also the modifications by which one form is evolved
from another, as the oblique rhombic prism, J, from the right rhom.
boidal, I, in the monoclinic system.
By the same process the secondary forms are obtained from the pri.
maries; indeed, in each system  containing more than one form, any one
in that system may be taken as the primary, of which the others are then to
be considered as secondaries.  Thus, in the dimetric system, either the
square prism, or the square octahedron may be taken as the primary form,
from which the other may be derived in the manner pointed out.  Therefore, although it is customary to consider as primary all the thirteen forms
mentioned above as belonging to the several systems, yet the whole number necessary for the derivation of all known forms is only six, one for
each of the six systems.
180. Laws of MIodification of Forms.-The modification of
the forms of crystals always takes place in accordance with certain laws, which may be stated as follows, viz:  All the similar
pl7arts of the crystal will be simzilarly and simultcaneously modifed, or half of the similar parts will be sinzilarly nzo(d~iedl
iXdependewtly of the other half.
In the forms of the monometric system all the parts are similar, and
all will therefore be modified in the same manner; but this is not the
QUESTIoNs. —How  may the rhombohedron be produced from the hexagonal prism? 179. What are secondary forms? In each of the above
systems may all the forms be derived from one?   How many fundamental forms only are then necessary?  180. Do the modifications in
the forms of crystals always take place according to fixed laws?  What
is the general law stated? Are all the parts similar in the forms of the
monometric system?




C t Y S T     A  O GR  p Y.                 167
case with the forms of the other systems.  In the dimetric system, for
instance, the square prism, D, (page 161,) has two kinds of faces, tle
basal and the lateral, and also two kinds of- edges, but only one kind
of solid angles.
The lateral edges, being formed by the meeting of similar faces, m"ay
be truncated, that is, replaced by a plane equally inclined to the two
faces; but the basal edges, being formed by the meeting of dissimilar1
faces, do not admit of truncation.  The new plane replacing one of these
edges will always be more inclined to one of the old faces than to the
other.
The solid angles are all alike, but each being formed by two plane
angles that are similar to each other, but unlike the third, they cannot
be truncated.  The figure V represents a square prism with its lateral
V OW X
19
Replacements.
edges truncated, and in W, we see one of the same with its basal edges
replaced, but each of the new planes is unequally inclined to the adjacent basal faces 0, and lateral faces I.  In the figure X, the square
prism has its angles replaced, the new plane, p, making equal angles
with the faces I, but not with 0.
By continuing the replacements seen in W, or in X, until the old faces
are entirely obliterated, it is evident that we shall have the square octaSquare Octahedron.
hedron, Y, which sustains the same relation to the square prism as the
regular octahedron does to the cube.
QEsTIONS. —What is said of the faces of the square prism?  YWhat is
said of the faces forming the basal edges?  Can these edges then )be
truncated?   May the lateral edges be truncated?   If we replace tile
basal edges on the angles of the square prism, continuing the replacement until the original faces are all obliterated, what form will result?




168                  C R Y S T  ALOG It AP I Y.
By examining the forms belonging' to other systems, and applying the
same general law, it becomes appalrent that the variety of forms capable
of being produced is really unlimited, but the subject cannot be pursued
further in this place.
181. Formnation of Crystals. —When a substance crystalizes in circum
stances to admit of observation, a very small crystal is first seen, which
gradually increases in size by the deposition of particles on the different
faces.  If this addition of matter be equal on all the faces the form is
continued the same, but if there is more added on some of the faces than
on others the crystal becomes more or less irregular.  Changes of form,
in accordance with the laws above mentioned, we may suppose to be produced in the following manner.  Let us suppose a substance crystalizing
in the monometric system, as galena, or common salt.  A cube is formed
and is gradually increasing in size by equal additions upon every face,
but at length, from some cause not understood, a change takes place, and
regular spaces are left at the angles or edges of the cube.  We will suppose that at each edge of the cube there is left a deficiency, or decremenot,
of one row of particles for every addition upon the surface; this will
occasion the formation of planes upon the edges, and. if continued, will
result in the production of a rhombic dodecahlledron.
Or let us suppose, as the additions are made, a decrement occurs at
the angles only:-this will result in the replacement of the angles.  Let
A be a snmall cube on which deposits are taking place, as suggested
above, leaving decrements at the angiles.  After a time it will have the
form B, and by a continuation of the process will become of the form C,
and then of D: but unlike the forms represented in the figures, it will
be constantly increasing in size.  But the form, D, is evidently that of a
MIonometric Forms.
regular octahedron with all its solid angles replaced by planes; and we
suppose the process continued until the perfect octahederon would be
formed.  By reversing this process, commencing with the regular octahedron, anid supposing additions to be made on the faces, with decrements at the angles, and continuing the process sufficiently, the cube
will eventually be produced.
Whether this is the real mode by which the variously modified secondary forms are produced, we may never be able to determine fully; but,
in the absence of positive proof, this has been presented as theoretically
possible.
QUESTIONS.-181. How do crystals increase in size? Illustrate the mode
in which a secondary form may be produced in the crystalization of commuon salt by a supposed decrement upon the edges?




R Y-T AL O GRAP H Y.                     169
182. Cleavage.-Crystals are generally capable of separation
in certain directions ky  natural joints;-a property which is
denominated cleavage.  In the primary forms this usually takes
place in planes parallel to the faces, but may also occur in planes
paralhel to any of the faces of secondary forms belonging to the
species.  It will usually be found in crystals that cleavage is much
more easy in some directions than in others; and the general rule
is that it will take place with equal facility parallel to similar
faces, and only in this direction.
183. Isormorphismn.-Isomorphous substances (from isas, equal,
and noo7lphe, form), strictly are substances which crystalize in the
same form; but the term  is generally used to indicate those
bodies which, in the comnpounds they form, are capable of
replacing each other, without changing the forms of the crystals
of these compounds.  Thus magnesia and lime, and the protoxides
of iron and manganese, form a group, any one of which may replace
another in whole or in part in the compounds they form.  So also
alumina (sesquioxide of aluminum), and sesquioxide of iron, fbrm
another group, and phosphoric and arsenic acids another.
In general, isomorphous substances will be found to possess
other analogous properties; and the compounds they form will
often closely resemble each other in all their leading properties.
We have an excellent illustration of this in the alucms, of which
there are several, but all possessing the same crystaline form.
and the same astringent, sweetish taste, the same solubility in
water, &c.  Below are the formula representing their composition
Common alum........ KO,SO, + A 1,203, 3  0S, + 24 H0.
Iron alum............. KOS, S0      F e,O,, 3 S0, + 24 110.
Chromium alum,.......   10, 20  + Cr03, 3 203 + 24 -1 0.
Soda alum......... NaO,S0,3 + A203,, 3 SO, -p 24 10.
Ammonia alum....... NI,40,SO03+ A120, 3 SO,3 + 24 110.
QUESTION.- 182. Whiat is meant by cleavage? How does this usually
take place in primary forms? Is cleavage made with equal facility in
all directions?  183. What are isomorphous substances? Will isomor-.
phous substances usually be found to possess other analogous properties
besides those of form? What is said of the alums in this connection?
15




170                CRY ST A LO GR AP   Y.
Comparing these formula, one after another, -itfb  the first,
that of common alum, we perceive that *n iron and chroniumn
alums the sesquioxide of aluminum is replaced by the sesquioxides
of iron and chromium respectively; and in the soda and ammonia
alums, the potash is replaced in one by soda and in the other by
ammonia (oxide of ammonium). These several sesquioxides are
therefore isomorphous, as are also the potash, soda, and oxide of
ammonium which replace each other in the other formula. This
list of alums might be still further extended; and all constitute a
single family of compounds formed on the same type and possessing very similar properties.
Many other similar groups of compounds rmight be given in
which isomorphous substances replace each other, but the above
will suffice.
The following group of simple substances that are isomorphous, is from
Gmelin.
1. Carbon, phosphorus, potassium, titanium, bismuth, cadmium, lead,
iron, copper, silver, and gold.
2. Potassium, sodium, lithium, calcium, zinc, lead, and silver.
3. Oxygen, sulphur, and chlorine.
4. Arsenic, antimony, and tellurium,
5. Platinum, iridium, and osmium.
184. Dimorphisrm.-Dimorphous substances (d'is, double, and
morphle, form,) are such as are capable of crystalizing in two
forms belonging to different systems of crystalization.   A  few
substances are known which, under different circumstances, crystalize in three forms, and are therefore called triimogyhous.
Among the simple substances, carbon, sulphur, and perhaps
copper, are dimorphous.   Carbon, as cliamlzod, takes a form
belonging to the monometric system, but, as graphite, it is found
in the hexagonal system.  It is scarcely necessary to remark that
in these different forms many of its properties are essentially different.  As diamond, it is the hardest substance known, and is
transparent, but, as graphite, it is comparatively soft, perfectly
black, and opake.
Sulphur when crystalized by melting and slow cooling (175)
QuESTrONs.-I-How  do the formula for the different alums compLare
with each other?   184. What are dimorphous substances?  What
simple substances are mentioned as being dimorphons?




CRYSTALOGRAPHY.                             171
the crystals take forms belonging to the monoclinic system, but
the native crystals, and those obtained by dissolving sulphur in
the bisulphide of carbon, belong to the trimetric system.
Many compound bodies are found to crystalize in two or more forms;
and sometimes it has been ascertained that the particulaIr form produced
will depend in some degree upon the temperature of the crystalizing solution.  Carbonate of lime usually crystalizes in forms of the hexagonal
system, but occasionally it forms crystals of the trimetric system, and is
then called arragonite.  Such researches as have been made on the subject indicate that it takes the form last mentioned when crystalizing at
about 2120, but forms crystals of the hexagonal system only at very low
or very high temperatures.
In some cases a change of the crystaline arrangement of the particles
of a body, attended by a change of color, is produced by a mere variation of temperature.  Thus protiodide of mercury sublimed at a very
gentle heat forms small dimetric crystals of a scarlet color, but if sublimed at high temperatures the crystals are luonoclinic and of a sulphur
yellow color.  The scarlet crystals become yellow by being heated, but
tur'n red again when cooled.
The yellow crystals obtained by sublimation retain this color when
cooled, but if scratched or disturbed by some pointed instrument, they
aLt once turn red at the point touched, and the change of color soon
extends to the whole mass of crystals in contact.
QUESTIONS.Tspo pon what has the form of dimorphous substances sometimes been found to depend?l'




PART IIIo
SPECI AL CHEM  ISTRY-INOR GAN IC
185. Classification of Elements.-Having discussed under the
head of GENERAL CHEMIiSTRY the important principles pertaining
to chemical changes generally, we are now prepared for the examnination of the various simple substances, or elements, found in nature,
and their inorganic compounds so far as may come within the objects
of the present work. And, in accordance with general usages we
shall divide them  into the two great classes of non-metallic and
metallic elements, called also nmetatlodcs and metals.
Though this division is universally recognized by writers upon
this science, yet it is founded upon properties which are not absolute, and are much more distinctly seen in some of the elements
than in others; a degree of vagueness therefore attaches to it,
and several of the simple substances are not readily determined,
being referred to either of the divisions with nearly equal propriety.  It is however retained because of its convenience; and,
following the example of iRegnault, we shall consider as non-metallic the following fifteen elements, which are further arranged
in natural groups.  Of these, silicon, tellurium, and arsenic have
not unfiequently been classed with the metals which they-and
especially the last two-strikingly resemble in some of their properties.  Iodine and bromine also, though with less reason, have
been sometimes regarded as metals.
All the elements may enter into the composition of inorganic
compoLmnds, which are produced in the mineral world, and may
be formed artificially; but only a few of them-more especially
carbon, hydrogen, oxygen, and nitrogen-form organic compounds,
which originate almost exclusively in plants and animals,
QUESTIONS.-185. Into what two classes are the elementary substances
divided?  How many non-metallic elements are there?  Allay all the
elements enter into the composition of inorganic or mineral compounds?
What four are mentioned as forminrg most organic compounds?
(1'72)




ON  METALLI E      C ELEMEN T S.                173
A further discussion of the relations of organic and inorganic
bodies will be introduced hereafter.
186. For the sake of convenience we shall arrange the nonmetallic elements in the five following groups, and introduce them
for description in the order in which their names appear.  Among
the individuals of some of the groups a striking resemblance is
manifest, but in other groups this is less apparent.
Each element will first be described, and afterwards will be
introduced the more important compounds it forms with  the
other elements previously described.
METALLOIDS, OR NON-METALLIC ELEMENTS.
GROUP. I.  OXYGEN.  IIYDROGEN.  NITROGEN.
These substances are brought together in the same group merely for
the salke of convenience; each one properly constitutes a class by itself.
The first, oxygen, is more abundant than any other element, constituting from 30 to 50 per cent. of the whole globe, or at least that part of it
accessible to man.  It forms compounds with nearly all other elements.
Hydrogen is a highly electro-positive substance, and in some of its
properties resembles the metals.
Nitrogen is noted for its very feeble afinity for the other elements,
Avhether electro-positive or electro-negaltive.  It has sometimes been
classed with phosphorus and arsenlic, to which it has some resemblance.
Guour II.  CHLORINE. IODINE. BroBIINE.  FLUORINE.
These electro-negative elements constitute a very distinct natural
family; each forms a single acid compound with hydrogen, and all
except the last form analogous acid compounds with oxygen.
GRouP III.  SULPHUR. SELENIUM.  TELLURIUM.
These elements, especially the first two, closely resemble each other;
they also form acid compounds both with oxygen and hydrogen, which
are analogous in their constitution.
QUESTIONS.-186. In how many groups are the metalloids arranged?
Name the elements of the first group. Why are these arranged together?
Nalme those of the second group.  Name the elements of the third group
164,




174                        o X y GE:  N.
GRouP IV. PHiOSPIIiORTs, ARSENIc.
Two elements very similar in many of their properties, and forming
similar compounds with oxygen and hydrogen.  Many of their compounds are isomorphous.  Antimony also properly belongs to the group.
GROUP V., CA~RBON. SILICON. BoitoN.
Combustible bodies incapable of being volatilized even at the highest
temperatures known, and forming feeble acids with oxygen.
GROUP I.
OXYGEN        Gaseous at all temperatures; but having few other points
HYDROGEN  of resemblance.  A compound of the first two constitutes
NITIOGEN j wcter,-a mixture of the first and last, atlmosilieric air.
OX Y GE N.
Sy mzol, 0; Egquivce'nt,, 8; lDensityZl, 1 106.
187. 1History-.Oxygen (from  oxus, acid, and gez2nao, to produce) was discovered by Priestly and Scheele, independently of
each other, in 1774.  It has been called esn7yrecal aneh, because
it  supports- combustion, and  vital air', because  necessary  to
respiration.   It is the most abundant of the elementary substances, and constitutes from 30 to 50 per cent of the mass of the
globe, or at least that part of it accessible to man; it forms also
an ingredient of nearly all animal and vegetable compounds.
188. Prepaxra tion.-Oxygen is a gaseous substance, and may
be obtained from  several sources; but the best method to procure
it, when only a small quantity is required, is to heat an ounce or
less of chlorate of potash in a green glass flask or retort.  This
salt is comrnposed of chloric acid, C105, and potash, KIO; and,
when heated nearly to redness, gives up the whole of its oxygen,
as shown by the following formula.  Thus,
KO,C105 =KC1 + 60;
each atom of the salt yielding one atom of chloride of potassium,
and six. atoms of oxygen.  The process succeeds better if, before
QuEsTIONs.-Name the elements of the fourth  and fifths groups.
187. Whnat impoortant facts are mentioned in the history of oxygen?
188. Describe the mrode of preparing oxygen from chlorate of potash?
How is it to be collected?




X Y GE N.                        175
heating, the salt is intimately mixed with an equal weight of powdered peroxide of muanganese, or oxide of copper.
The  accompanying  figure
will serve  to  illustrate  the
arrangement of the apparatus
required for the experiment.
The salt, contained in a retort,
is heated  by a  spirit-lamp,
which produces no smoke, and           Prepaaton of Oxygen
the gas, as it forms, passes
under a receiver filled with water, and placed on a shelf in a
pneumatic cistern, a section of which is shown in the figure.
The receiver is open at the bottom, and it is first filled with
water by plunging it in the cistern, and then bringing it to its
upright position, and raising it carefully to its place upon the
shelf, which is just beneath the surface of the water.  The water
rises in the receiver, in consequence of the atmospheric pressure
(see the author's NVatural Pthilosopf7y, p. 135); and when the
gas is forced underneath it, it rises in bubbles, displacing the
water, and occupying the highest part of the receiver,-the shelf
being supposed to have an aperture in it, to allow the gas to pass
upward, and the water also to escape.
189. WVe have in the above equation the first instance that
occurs in this work of the use made of symbols to illustrate
chemical changes.  The expression constitutes a proper equation,
but it has peculiar properties, in which it differs from algebraic
equations.  The separate symbols in the equation, of course,
indicate equivalents or atoms of the elements symbolized, and the
manner in which they are combined in the first member is also
designed to indicate the mode of combination of the several substances expressed, before any change is produced; while the
second member of the equation shows the state or mode of combination of the same elements after the change has been produced.
There must therefore be found represented in each member
of the equation the same elements (and no others), and the same
QUESTIONS. —189. What is the design of the equation in the preceding
palragraph?  What is expressed in the first member of the equation?
Wh'at in the second? What is required in the two members in equations
of this kind?




1 71 6                    OXYGEN.
member of atonis of each element.  Thus, in the above equation
we have represented in each number 1 eq. of potassiumn,   eq. of
chllorine, and 6 eq. of oxygen.  Of course, if the sum  of these
were represented in numbers, it would be the same for eachmember.  These remarks apply in all similar cases.
When a large quantity of oxygen is to be obtained, it is more
economical to make use of saltpetre (nitrate of potash); but a
much greater heat is required to decompose it, and an iron retort
mIust therefore be substituted, instead of glass.  The iron retort
containing the saltpetre is placed in a furnace, the heat of which
can be easily regulated, and a lead tube is connected with it,
leading to the pneumatic cistern.  As soon as the bottle has
attained a full red-heat, the gas begins to come over; and if care
is taken to prevent the heat becoming too great, very pure
oxygen will be obtained.  The changes that take place are illustrated by the following formula:
KO,NO)   - -KO,N03 + 2 0.
Thus, each atom of nitrate of potash yields one atom of hyponitrite of potash, and two atoms of oxygen.
This gas may also be procured from  the peroxides of manganese, lead, and mercury, and from  other substances.  A ready
method to procure it from  the peroxide of manganese is as follows:  Let a flask of green glass be partly filled with the peroxide, and then enough strong oil of vitriol poured upon it to
moisten it thoroughly, and then apply the heat of an alcohol
lamp.  By this process sulphate of protoxide of manganese is
formed, and oxygen gas, as shown by the following equation:
MIn O2 -- SO, = MnO, SO  + O
It is thus seen that every atom of the oxide of maniganese will
yield one atom of oxygen.  To insure purity it is well to pass the
gas as it is formed through a weak solution of potassa by means
of a three-necked bottle, as shown in the figure on next page.
QUESTIONs. —May oxygen be prepared from nitrate of potash? De.
scribe the mode of preparing it by the use of peroxide of manganese  and
sulphuric acid.




OXYGEN.                             177
Preparation of Oxygen.
Whatever mode of preparing it may be adopted, the first por)ns of gas that come over should always be allowed to escape,
it will be mixed with atmospheric air, contained in the appatus at the beginning of the operation.
190. It is always easy to calculate the quantity of oxygen
rich any given quantity of materials we may desire to use will
brd.
We will suppose that 1 oz. of chlorate of potash is to be employed,w many cubic inches of oxygen will it afford?
There are in each equivalent of the chlorate of potash 1 eq. oof potash
d 1 eq. of chloric acid, composed as follows, viz:
KO  — 47'1    122. 5
C105   754  t1225
which 48 parts, or 6 eq., are oxygen. We have then the following
3portion:
122-5: 48:  480: x,
Lence x = 188 grs. for the weight of the oxygen in 1 oz. of the chlorate.,w 100 cubic inches of oxygen (192) weigh 34-28 grains; and we have,refore this proportion:
34-28: 100:: 188: x,
x = 548 cubic inches, or about 2A gallons.
QUESTION.-190. Supposing the chlorate of potash used to prepare the
3, how may we calculate the quantity that may be produced from an
ace of the salt?




178                       OXYGEN.
191. Oxygen gas is also given off by plants
under the influence of light.  Let a sprig of
mint be placed in a white glass globe, which is
then to be filled quite full of spring-water, and
~~-~ -- __  the mouth inverted  in a tumbler of water, as
shown in the figure.  It is then to be placed in
7llllz F~h the direct rays of the sun; and in a short time,
l,}ttil}lhI j bubbles of gas will be seen collecting in the upper
Oxygen from Plants. part of the glass, which is nearly pure oxygen.
192. Properties.-Pure oxygen is a colorless gas, without odor
or taste, and has never yet been reduced to the liquid state by
any degree of cold or pressure.  It is very slightly absorbed by
water, 100 cubic inches of that liquid taking up 3 or 4 of the gas.
It is heavier than air, 100 cubic inches weighing 34'28 grains, while
the same volume of air weighs only 31 grains, the temperature being at 60~ F., and the barometric pressure at 30 inches. Its density
is therefore 1-106. It has a very extensive range of affinity, entering into combination with all the other elements except fluorine.
Oxygen is a powerful supporter of combustion; and all substances that are capable of burning in the open air, burn in it
with far greater brilliancy. A piece of wood, on which the least
spark of light is visible, bursts into flame the moment it is put
into a jar of oxygen; a recently extinguished
candle, with the least spark of fire upon the
wick, is relighted; lighted  charcoal emits
beautiful scintillations; and phosphorus burns
with so powerful and dazzling a light that
the eye cannot bear its impression,  Even
iron and steel, which are not commonly ranked
\ \.     /    - among the inflammables, undergo rapid combustion in oxygen gas.
_. —  A The combustion of iron and steel is effected
/0 qH\Ss A    by introducing it in the form of wire or thin
slips,-as pieces of watch-spring, —into a
Combustion of Iron.   vessel of the gas, as shown in the figure. The
QuasTIoNs.-191. IIow may it be shown that plants evolve oxygen
under the influence of light?  192. What are some of the properties
of oxygen?  Why is it called a supporter of combustion?  Why is a
candle recently extinguished relighted when plunged in the gas?




OXYGEN.                         179
combustion is commenced by attaching to the lower extremity a
piece of spank or other combustible, which is ignited the moment
it is to be introduced into the gas. As the combustion progresses,
if the cork is tight, the water contained around the bottom of the
receiver in the shallow dish is seen to rise, and more naust be
poured in, to prevent the entrance of air from without.  This is
occasioned by the absorption of the oxygen by the iron, to form
oxide of iron, which falls in melted globules into the dish.  When
a lighted candle is let down by a wire into a
jar of this gas, as in the figure, the case is
different; the candle burns for a time with increased splendor, but soon the flame begins to
diminish, and at length  entirely disappears,
without any diminution of the volume of gas
contained within.  If the candle be relighted
and returned to the receiver, it is now instantly
extinguished, the gas having lost entirely its
power of supporting combustion.  The reason
is, that the oxygen has disappeared, and a new
gas, carbonic acid, CO2, taken its place, which  Taperin Oxygen.
has exactly the sanle volume as the oxygen from which it was
formed. If a piece of burning charcoal had been used, the result
would have been the same.
193. Ordincrty  comlwbustion consists in the union of combustible
matter with oxygen, and is usually attended by the evolution of
heat and light.  A new substance is also formed, which may be
solid, liquid, or gaseous.  When iron is burned, a solid product
(oxide of iron) results, which just equals the weight of the iron
and oxygen together, that have disappeared during the operation. It is evident that in every case the product of the combustion must be equal in weight to that of the oxygen and other
substance which have combined.
Combustion may, however, be produced without oxygen; a
QUESTIONS. —How may iron and steel be made to burn in the gas?
What is produced when iron is burned in this way?  Why does the
water rise in the receiver as the combustion progresses?  Why is not
the same effect produced when a candle is made to burn in the gass
193. What is ordinary combustion?  AMay combustion be producec
without oxygen?




180                       OXYGEN.
piece of phosphorus or powdered antimony, let down  into a
receiver filled with chlorine, will take fire spontaneously, and
burn with the evolution of light and heat; so that ordinary conmbustion can only be considered as a particular case of chemical
action.
Combustion is the great source of artificial heat and light
(13, 65). To produce an intense heat means are contrived te
force large quantities of air (one-fifth of which is oxygen) in
contact with a mass of ignited coal, the carbonic acid formed
being allowed to escape freely. To produce light, we burn oil,
tallow, or other substances which contain a large proportion of
the same material as coal, as we shall see hereafter. By supplying the burning body with pure oxygen, the intensity of both
the heat and light is greatly increased.  A  very considerable
heat is also produced, simply
by blowing with  a proper
Blowpipe,             blowpipe through the flame
Blowpipe.
of a lamp or candle, which
is sufficient for numerous small operations.
A better form of the blowpipe is represented in the next figure,
Mouth Blowpipe.
The enlargement at the angle is designed to retain auy moisture
9-:__-  _ that may enter the tube from the
mouth.
In using the blowpipe the flame
is driven violently to one side, as
shown  in  the figure; and the
greatest heat is found just be- i ~iQk       yond the point of the inner flame.
Blowpipe Flame.        If pure oxygen is used with the
QUESTIONS.-What is the great source of artificial light and heat?
What substances do we use for fuel when light is to be produced? Whlat
is the use of the blowpipe? At what point in the flame is the heat
greatest?




HYDROGcEN.                          ]81
blowpipe, instead of atmospheric air, as may easily be done, the
heat produced becomes much more intense.
194. Respirationl is also supported by oxygen gas, which is
absolutely essential to the process; no animal can live in an
atmosphere that does not contain it.  A small animal, as a bird,
confined in a close box, feels no inconvenience for a time; but
the oxygen gradually is absorbed, carbonic acid gas taking its
place, and respiration becomes laborious, until at length the aninal dies for the want of oxygen. Pure oxygen, however, does
not answer the purposes of respiration, as it excites the vital
action too much, producing various inflammatory symptoms, and
at length death, as the result of the over-action.
195. Manipulation of Gases.-The general method of collecting oxygen,
described above, answers for all the gases that are not absorbed by
water. In the same mode, also, a gas may be transferred from one
receiver to another. When a gas is to be collected that is largely absorbed by water, some other liquid must be used, as mercury, or a
saturated solution of salt; or the air may be removed by the air-pump,
and then the gas admitted.
Y YDR O GEN.
Symbol, H; Equivalent, 1; Density, 0 069.
196. History.-This gas was first described by Cavendish in
1766, and received from him the name of infnammable air, because of its combustibility.  It has received its present name
because it forms a part of water (from hudor, water, and yennao,
to produce).  It is not found free in nature, but constitutes oneninth part of water, and enters into nearly all animal and vegetable substances.
197. Preparation.-Hydrogen gas is always procured by the
decomposition of water, either directly or indirectly.  The direct
QUESTIONS. —194. Is oxygen necessary for the support of respiration?
Will pure oxygen answer the purpose?  195. What is meant by the
manipulation of the gases? When a gas is to be collected that is largely
absorbed by water what is the course to be pursued? 196. What faicts
are mentioned in the history of hydrogen?  Why has it been called
inflammable air?  Why is it now called hydrogen.  197. From what is
this gas always prepared?
16




182                     HlYDROGEN.
method consists in passing the vapor of water over metallic iron,
heated to redness.  This is done by putting iron wire or turnings
into a gun-barrel open at both ends, to one of which is attached
a retort containing pure water, and to the other a bent tube. The
gun-barrel is placed in a furnace, and when it has acquired a full
red-heat, the water in the retort is made to boil briskly.  The
gas, which is copiously disengaged as soon as the steam comes in
contact with the glowing iron, passes along the bent tube, and
may be collected in convenient vessels, by dipping the free
extremity of the tube into the water of a pneumatic trough.
The arrangement
of the apparatus will
be seen by the ac= 17~  ~      A  retort, a, conPreparation of Hydrogen.        the gun-barrel, c c,
in which are the iron turnings to be heated, and at the left is the
receiver to collect the gas as it is formed.
The second, or indirect method, which is the one usually
adopted-in practice, consists simply in dropping pieces of zinc
(or iron) into sulphuric acid, diluted
with five or six times its weight of
water, and contained in a convenient retort.  Action immediately commences,
without the aid of heat, and the gas
may be collected over water.  A jar
prepered as in the figure is very con.
venient for the purpose.  The water
and zinc are first introduced, and after
Preparation of Hydrogen.   the cork with the tubes is carefully
inserted in its place, the acid is poured in through the longnecked funnel.  The gas is collected by means of a tube leading
from the cover to a receiver, as before.
QuESTIONS. — Describe the mode first mentioned of preparing hydrogen
gas. Describe the mode by the use of dilute sulphuric acid and zinc.




HYDROG EN..183
IIydrogcn gas is also very readily procured by
the action of metallic potassium  or sodium  upon
water.  A small receiver is first filled with water,
and then a piece of the metal, wrapped in bibulous
paper, is quickly placed under it; as soon as the
paper becomes moistened, violent action  takes
place, and the hydrogen that is liberated rises to
the upper part of the receiver.  This method, on
account of the high price of potassium and sodiumrn,  Deompositionby
is very expensive.                                     Potassium.
198. Properties.-Pure hydrogen gas is without color, odor, or
taste, and refracts light powerfully. It has never yet been reduced
to the liquid state.  It does not support respiration, but may be
breathed, when mixed with air, without injury.
It is the lightest substance known, being sixteen times lighter
than oxygen, and more than fourteen times
lighter than  atmospheric air, 100 cubic
inches weighing only 2'14 grains.  Soap-         4ikl!t.
bubbles filled with it rise readily through
the air.  They may be formed very easily
by attaching a common tobacco-pipe by its
stem to a gas-bottle filled with the gas, and
forcing out the gas slowly, immediately soap Bubbles with Hydrogen.
after dipping the mouth of the pipe in a strong solution of soap
in warma water.
Hydrogen -gas is eminently combustible, and
burns with  a feeble yellowish flame.   This may
be shown  by pouring some dilute sulphuric acid
upon some pieces of zinc in a vial, and inserting a
cork with a small glass tube or pipe-stem, as shown
in the accompanying figure.  In a short time a jet
of hydrogen will issue from  the tube, and may be
inflamed.   This is often described as the philosophical candle.                                         Hybusdble.
QuEsrTIONs.-Describe the mode of preparing hydrogen by the uso
of metallic potassium.  198. Mention some of the properties of hydrogen.
What is the weight of 100 cubic inches of the gas? What is said of soap.
bubbles formed with it?  How may it be shown that the gas is comr
bustible?




184 Hf                     Y DHYDROGEN.
If, now, as the jet continues to burn, a glass tube,
half an inch  or more in diameter, and one or two
feet long, be held  over it, and properly managed,
a clear musical note will be produced, its pitch depending upon the length and diameter of the tube.
It is occasioned by successive explosions within the
tube, which follow  each other so rapidly as to cause
the air in the tube to vibrate, as in a musical instrument.
so          The following is an interesting and instructive experiment with this gas.  Let a bell-glass receiver be, nisiefilled with it in the pneumatic cistern, and then, careSunds.  fully lifting it with the left hand, with the right hand
pass up into the interior a lighted candle, as represented in the
annexed figure. As the flame enters the
hydrogen, it will take fire with  a slight
explosion, and continue to burn where it is
in  contact with  the air; but the candle
being carried farther upward into the pure
hydrogen, will be extinguished. The hydrogen, being combustible, is inflamed by
the burning candle, but not being a sup-,g GAd    4    porter of combustion, the candle is extin-:, 4,\    guished as soon as it is surrounded by it.
The gas is retained in the receiver when
lifted from its place, because of its being so
Hydrogen not a Supporter. much lighter than air.
199, Hydrogen, being the lightest substance known, is made use of by
meronauts for filling their balloons. The buoyancy of a balloon filled
with it is easily calculated.  Thus, 100 cubic inches of air weighing
31 grains, the weight of a cubic foot will be 535.68 grains, while
the weight of an equal volume of hydrogen will be but 36.98 grains.
Now 535'68 — 36'98=  498'70 grains.  This number multiplied by the
number of cubic feet in a balloon, will give in Troy grains the weighi
required to be added to make it of equal weight with the air displaced;
QueSTIONS. —Describe the mode of producing musical sounds.  How
may it be shown that the gas does not support combustion? Will the
hydrogen itself be inflamed in the experiment?  199. Why is bydrogen
selected for filling balloons?  Describe the method of calculating the
weight a balloon will sustain in the air.




COMPOUNDS OF HYDROGEN AND OXYGEN.                185
nnd if it is loaded with anything less than this it will ascend. The weight
of the balloon itself is of course always to be taken into the account.
Coal gas being always on hand where there are gas-works, though much
heavier than hydrogen, is now much used in balloons in consequence
of its being cheaper, the balloon being of course made proportionally
larger.
Compounds of Hydrogen and Oxygen.
There are only two compounds of these substances known, the
protoxide, or water, and the peroxide; and the latter is altogether an artificial product, of difficult formation.
200. Protoxide of Hydrogen, or Water. —IO, or Aq.; eq.,
(1 + 8 =) 9,-This compound, considered in all its important
relations, and absolutely universal diffusion, is probably the most
important substance known to man.  It is the sole product of the
combustion of hydrogen, whether in the open air or mixed with
oxygen gas.  In the experiment for producing musical sounds,
Lhe water that is formed will be seen to condense in considerable
quantity on the inside of the glass tube, at the beginning of the
"'O~eeS  but it will be evaporated when the tube becomes hot.
The affinity of hydrogen for ox)gen is very great, but the two
tases do not coibine spontaneously, even if kept together for any
length of titne;.  We have seen above (162) that two measures
of hydrogen combine with exactly one measure of oxygen; and
the mixture may be exploded by the approach of flame, by the
electric spark, by intensely heated metal, or by the mere presence
of spongy platinum, a substance that will be described hereafter.
To explode the mixed gases by the electric spark, the spark must'-e made to pass through them.  This is accomplished in the
following manner.  A  small metallic        w
vessel, as a miniature cannon, has a
mLetallic wire, W, inserted in one side
Hydrogen Pistol.
through a piece of wood or ivory, so
as to extend nearly through to the other side, as shown in the figure.
QUEsTINS. — Why is coal gas now often used as a substitute foi
hydrogen in filling balloons?  How many compounds of hydrogen and
oxygen are known?  200. What is protoxide of hydrogen?  What is,;lid of the affinity of hydrogen for oxygen? In what proportion do they
combine by measure? By weight? How may the mixed gases be exploded?
16*




186       CO.MPOUNDS OF IHYDROGEN AND OXYGEN.
The piece is then to be filled with the proper mixture of the gases,
and a cork, C, inserted in the muzzle.  If, now, a spark of electricity be communicated to the ball of the wire WT, in escaping
fromn the other end it ignites the gases, and the cork is forced out
with a loud report. If a mixture of equal parts of hydrogen and
atmospheric air is used, the effect will be nearly the same.
The explosion which accompanies the union of these gases is
occasioned by the great expansion of the gases at the momen
of combination, in consequence of the heat developed. This is
the only rational explanation that can be given, and yet it is a
fact that this combination is attended by a contraction of onethird of the volume of the mixed gases in forming the vapor of
water, (162) to say nothing of the still greater contraction which
takes place by the condensation of the steam that is found.
This expansion takes place apparently with great violence; but
by using a strong receiver for the mixed gases it may be restrained,
and then the combination takes place
without any report.  The figure in the
margin represents a piece of apparatus
_______ / /   for this purpose.  A strong glass globe
three or four inches in diameter has a
metallic cap upon the neck, upon which
No Explosion,     a cover is firmly screwed after the mixed
gases are introduced.  From each side
of the globe is a projection or neck, with a metallic cap, through
which wires are inserted so as nearly to meet in the centre. When
the globe is charged with the mixed gases the electric spark is
passed between these wires, and the gases at once combine, but
without explosion, a slight flame only being seen at the instant.
The inside of the glass becomes covered with dew from  the
moisture produced, and when the cover is unscrewed the rushing
in of the air attests the vacuum that has been formed.
The ignition of hydrogen by spongy platinum is well shown by
holding a small piece of this substance in a jet of the gas, by
imeans of a small wire twisted round it.  The platinum must be
QuEsTIONs.-Describe the pistol for exploding the gases by the electric,park. What occasions the great expansion that takes place? May the
gases be made to unite without an explosion?




COMPOUNDS OF HYDROGEN AND OXYGEN.                  187
perfectly dry.  It gradually becomes heated to redness, and soon
the jet is inflamed.  The common ]hy(drogen~ fire-Cq)ap'aratus acts
upon this principle. Its construction is shown -in
the figure in the margin.  A cylindrical glass ves- fi41sel, A,  is partly filled with dilute sulphuric acid, i
and in it is a small glass receiver, 3, firmly ce- A
mented at the top into a cap connected with the    - Fi
brass cover.   By the action of the acid upon a -,i
piece of zinc, Z, suspended inside of this receiver   1lii iiilII
near the bottom, it is soon filled with hydrogen (
gas, which, on turning the faucet F, is forced out
by the rise of the liquid upon a piece of platinum
sponge, contained in the cup C.  Soon the platinum  is heated so
as to inflame the jet of hydrogen, from which a candle can be
at once lighted. The platinum sponge often
loses its property of inflaming hydrogen,
but recovers it again by being heated.
A  metallic cup of half a pint capacity
filled with the mixed gases and inver!ted
over a small piece of platinum sponge, supported a little above the table by a wire,
will be thrown upward to the ceiling by the
explosion produced.                            _
201. The conlpoqtnd Z1owpipe, which is   _:an invention of Dr. Hare of Philadelphia,
is a contrivance by which two jets, one of
hydrogen and another of oxygen, are made
tc issue together, and are inflamed as they escape. The gases are
brhought by tubes fiom separate
gas-holders, so as to discharge, as
near as may be, two measures of
hydrogen to one of oxygen.  The
heat produced by this instrument
is very great, probably exceeding
that produced by any other means.          Compound Blowpipo.
QUESTIroNs.-Describe the hydrogen fi~re apparatus.  Describe the ex.!p)eiment with the spongy platinum and the metallic cup.  201. Describi
the coiounzozd bloz2pipe. What is said of the heat which is produced?




188       COMPOUNDS OF -IYDROGEN AND OXYGEN.
Platinum and other substances incapable of fusion in the hottest
furnaces, are melted, and often even volatilized by it.  A small
piece of lime, held in the flame, becomes intensely heated, and
glows with a brilliant light, exceeding any other that can be produced artificially.  It is known under the name of the Drum2onocd fight, and is much used for practical purposes.
202. Water, at ordinary temperatures, is a transparent, colorless liquid, without taste or smell. In the open air, it boils at a
temperature of 2120, and freezes at 320. The vapor produced by
boiling, familiarly called steam, is perfectly colorless and transparent, and has a density of 0'622, air being 1;' 100 cubic inches
weighing 19'28 grs.  In the form  of ice, its density is 0'92.  A
cubic inch of pure water weighs 252.458 grs., being 814 times
as much as an equal volume of air would weigh. A cubic foot
weighs 1000 oz., or 62~  lbs. avoirdupois.  Water is probably
the  most powerful solvent known.   It is capable of combining, in definite proportions, with many substances, forming
compounds which yet remain perfectly dry.  They are usually
called?hycdrates.   Substances from  which all water has been
separated are said to be anhycrzcous.
Water is never found naturally perfectly pure; that of wells,
springs, and rivers always contains carbonic acid and saline matter
in solution, obtained while percolating through the soil; and that
from rain or snow is impregnated with air and oxygen, and sometinmes with other gases.  It is obtained pure only by distillation;
and even then, by standing for a time, it takes up more or less
atmospheric air, which, however, does not unfit it for the ordinary operations of the laboratory in which it is required.
203. AWater when it solidifies often forms beautiful crystals
(25) which are best seen in snow and frost;-in ordinary ice
they cannot usually be seen, though it is believed there is always
QUESTIONS.-What is said of the light produced when a piece of lime
is held in the flame?  By what name is this light known? 202. Whbat
is said of water at ordinary temperatures? What are its freezing and
boiling points?  What is steam?  What is its density?  What is the
density of ice? What is the weight of a cubic inch of water?  How
many times is it heavier than air?  What are the chemical compounds
of water called? Is water ever found perfectly pure in nature  How
only is pure water obtained?  203. When water solidifies does it take
the form of crystals?




COMPOUNDS OF HYDROGEN AND OXYGEN.                 189
a proper crystaline arrangement.  The primary crystals belong to
the hexagonal system (178-6), but they are often grouped to-,ether in various modes, as shown in the figures. Nos. 3, 4, 5, 6, 7,
Crystals of Ice.
and v aire more common than the simple forms Nos. 1 and 2.
These tuttcr are of more frequent occurrence in hoar-frost than
in snow,
204.'The different processes for procuring hydrogen, given
above, rcijuire some further explanation, before we dismiss this
subject.  The first method is founded on the fact that iron, at high
temperatures, decomposes water when presented to it in the form
of steam, the oxygen combining with the iron to form protoxide
of iron, and the hydrogen being set free. The changes are thus
represented 
HO + Fe - Fe + H.
The changes ~which take place in the second and more common
process for p-ocuring this gas, are more complicated.  They are
represented in the following formula. Thus,
HOSO03 + Zn = ZnO,SO, + II.
In this case it vill still be seen that it is the water which supplies
the hydrogen.  The oxygen of the water is transferred to the
zinc, forming protoxide of zinc, with which the sulphuric acid
immediately cumbines.  When a piece of clean zinc is immersed
QUESTIONs.-W1 hat is said of frost and snow?  204. Expllain the
several modes of procuring hydrogen, and write the equatious illustratlng
the reactiontll thllt take place.




190        COMPOUNDS OF HYDROGEN AND OXYGEN.
in water, little action takes place, because the outside becomes
coated with a thin film of oxide of zinc, which is insoluble in
water; but if sulphuric acid is present, this oxide is instantly
dissolved, and thus a clean surface constantly exposed to the
water.
In the third process, the metal itself at once decomposes a portion of the water, forming a soluble oxide of the metal, and liberating the hydrogen. Thus,
HO + K=KO + H.
Here the affinity of metallic potassium for oxygen is sufficient
to separate this element from  its union with hydrogen in the
water, forming oxide of potassium or potassa.
Great heat is produced  by the action, and the
hydrogen liberated is inflamed if the experiment
is made in the open air.  To show this all that is
necessary is to throw a small piece of potassium
Potassium inflamed upon the surface of some water, as shown in the
by water.   figure.
The mode of decomposing water by the galvanic current has already
(111) been explained.
205, Knowing that water is formed by the union of 2 volumes of hydrogen and 1 volume of oxygen condensed into 2 volumes of steam,
it is easy to calculate the density of steam, and also the quantity of each
of these elements in a given quantity of water.  Thus,
One volume of oxygen weighs          1.106
Two    "    hydrogen "  2X 069 = 0.138
Two    "    steam      "             1' 244
One-half of this sum, or -622, is then the density of the vapor of water
which is formed.
To calculate the quantity of each of the elements in 100 parts of water
we have
1.244: 1.106:: 100: x,
whence x = 88.9 = quantity of oxygen.
And 100 - 89 9 - 11-1 = quantity of hydrogen.
QVIUESTIoNs.-Is heat produced when water is decomposed by potassiun?  205. What is the density of steam?  Describe the mode of calculating it.




N IT R O GE N.                       1 91
206. Peroxide of Hydrogen —HO2; eq., (1 + 16   ) 17.-This subtance has been obtained only in the liquid form, and when most concentrated possesses a specific gravity of 1-452. It is colorless, trans.
parent, and without odor.  It is sometimes called oxygenized water.
Though it differs from water only in containing an additional equivalent of oxygen, it acts powerfully upon the skin, producing a prickling
sensation, whitening the surface, and destroying the texture, if the application is long continued.
If the temperature is raised as high as 590, it is decomposed and converted into water and oxygen gas; a sudden elevation of temperature
even causes an explosion. It is also decomposed by the action of nearly
all the metals, and many of the metallic oxides.  Diluted with water or
mixed with some acid, it is less liable to decomposition than when pure.
NITROGEN.
Symbol, N; Equivalent, 14; Density, 0'972.
207. History.-The existence of this element has been knowni
since 1772; and it was recognized as a constituent of the atmosphere in 1775.  It was first called azote (from  a, privitive, and
zoe, life), because it does not support respiration; it receives its present name from the circumstance that it forms an ingredient of nitre.
208. Preparation.-Nitrogen gas is readily prepared, nearly
pure, by burning a piece of phosphorus in a receiver over water.
A  small cup, C, containing  a piece of
phosphorus, is placed upon the surface of
the water in the pneumatic  cistern, the
phosphorus ignited, and the receiver then
placed over it.  The phosphorus continues              v
to burn, absorbing all the oxygen, and the           _g!=
water rises to supply its place, as shown in
the figure.  The glass will at first be filled   --   I
with phosphoric acid fumes, which how-   -
ever will soon be absorbed by the water.
Preparation of Nitro —on,
Some vapor of phosphorus, carbonic acid,
and perhaps a trace of other gases, may be contained in the
QuESTIONs. —206. What is peroxide of hydrogen? What aire sonic
of its properties?  207. How long has nitrogen been known? Wlhat was
it first called?  Why has it received its present name? 208. Describe
the mode of preparing nitrogen.




192                ATMOS PERIC AIR.
nitrogen thus prepared, but it will be found sufficiently pure for
nearly all purposes.  Other processes might be described for procuring it, as by passing a current of chlorine gas through strong
aqua ammonia, but the above.is the most speedy and convenient.
209. Properties.-Pure nitrogen is a colorless gas, wholly
devoid of smell and taste, and is distinguished from  other gases
more by negative characters than by any striking quality.  It is
not a supporter of combustion, but, on the contrary, extinguishes
all burning bodies that are immersed in it.  A
taper immersed in it is extinguished at once.  No
animal can live in it; but yet it exerts no injurious
action either on the lungs or on the system at large,
the privation of oxygen gas being the sole cause
/ 1:l      of death.  It is not inflammable,  like hydrogen;
li   I;1lthough, under favorable circumstances, it may be
made to unite with oxygen.  It is slightly dissolved by water, and is sometimes found in the
i'I'      LE'~    t   water of mineral springs, as at Lebanon, in the
State of New York. 100 cubic inches of the gas
Dombes not support weigh 30'16 grs., giving a specific gravity of 0' 97.
Atmosph7er'ic Air.
210. The earth is everywhere surrounded by a mass of gaseous
matter, called the atmosphere, which is preserved at its surface
by the force of gravity, and revolves with it around the sun.  It
is colorless and invisible, excites neither taste nor smell when
pure, and is not sensible to the touch, unless when it is in motion.
It possesses the physical properties of elastic fluids in a high
degree.  Its specific gravity is unity (1), being the standard with
which the density of all gaseous substances is compared.  It is
814 times lighter than water, and nearly 11,065 times lighter
than mercury, 100 cubic inches weighing 31 grs.
QuESTIONs.-Is the nitrogen thus obtained pure? 209. What are
some of the properties of nitrogen?  210. What is the atnzoshiere?
WVlat are some of the properties of atmospheric air?  What is the
weight of 100 cubic inches?




ATM OSPHERIC  AIR~.                       193
Atmospheric air is composed of nitrogen and oxygen, with a
variable proportion of carbonic acidcl and watery vapor, l usually
a trace of ammonia.  Besides these, there may occasionally be
other substances present, depending upon local causes, as the
odoriferous principle of plants, and the miasmata of marshes,
which is supposed to be the chief cause of disease in many unhealthy situations; but they cannot be detected by chemical tests.
Instruments for determining the relative pro-          /oq
portion of the gases composing the atmosphere             lo
are called  eudiometers.   The following con-             1o
trivance answers the purpose very well.  Let a
glass tube, closed at one end, and graduated to
100 parts, with a small piece of phosphorus sup-         1i 
ported in it on a wire near the top, be placed as;I
in the figure, with the open end immersed in a             4o
vessel of water.  The phosphorus gradually absorbs the oxygen of the air in the tube, and the
water rises to supply its place.  In one or two            I
days, depending upon the temperature, the ab-           _i
sorption will be complete; and  the number
of the division  of the tube now  filled wmith
water will indicate the proportion of oxygen.         Laudiometer.
By the above and other similar modes of analysis, it is found
that the atmosphere in 100 parts is composed ofBy Teigqht.     By 2Measure.
Nitrogen............. 76.9............... 79'3
Oxygen................. 23.1...............  20-7
1.00            100
The proportion of carbonic acid varies from 2 to 6 parts in 10,000
of air.  A trace of ammonia is not unfrequently found, and also
of carburetted hydrogen.
The atmosphere is believed to extend to the height of about
forty-five miles, becoming continually less and less dense from the
QUESTIONs. — What is atmospheric air composed of? What other gases
are also found in it?  What is the design of eudionezters?  Describe the
mode of determining the proportion of oxygen by means of phosphorus.
What is thus found to be the quantity of oxygen in 100 parts of air?
What is the usual quantity of carbonic acid in 10,000 parts of air?
What is the height of the atmosphere?
17




194                ATMOSPH I{ERIC AIR.
surface uprward; and presses by its gravity upon the surface witih
a force equal, ordinarily, to about 15 lbs. to the square inch.  It
is capable of supporting a column of water about 34 feet, and a
column of mercury about 30 inches in perpendicular height.
211. Atmospheric air is highly compressible and elastic, so that
its particles admit of being approximated to a great extent by
compression, and expand to an extreme degree of rarity when the
tendency of its particles to separate is not restrained by external
force.  The volume of air and all other gaseous fluids, so long as
they retain the elastic state, is inversely as the pressure to which
they are exposed.   Thus a portion of air which occupies 100
measures when compressed by the ordinary atmospheric pressure,
will be diminished to 50 measures when the pressure is doubled,
and will expand to 200 measures when the compression is reduced
to one-half.  But those gases which are susceptible of condensation by pressure into the liquid form, as the pressure approaches
this point, vary from the law, the volume diminishing more rapidly
than this would indicate.
The chief chemical properties of the atmosphere are owing to
the presence of oxygen gas. Air from which this principle has
been withdrawn, is nearly inert.  It can no longer support respiration and combustion, and metals are not oxydized by being
heated in it.  The uses of the nitrogen are in a great measure
unknown.  It has been supposed to act as a mere diluent to the
oxygen; but it most probably serves some useful purpose in the
economy of animals and plants, the exact nature of which has not
been discovered.
212. The question has often been discussed, whether the oxygen
and nitrogen of the atmosphere are to be considered as chemically
combined, or only in a state of mixture; but the latter opinion
now generally prevails.  It has been supposed that if they are
merely in a state of mixture, oxygen, being the most dense, ought,
QUFSTIoN's. —To what height will the atmosphere support a column
of water?  Of mercury?  211. Is atmospheric air compressible an(1
elastic?  NW"hat is said of the volume of air and other elastic fluids in
relatioh to the pressure to which they may be -subjected? To whLat,11ra
the chief chenical properties of atmospheric air owing?  212. Are the
oxygen and nitrogen of the air to he considered chemically combined, or
only in mixture?




COMPOUNDS OF NITROG-EN AND OXYGEN.                 195
to settle towards the surface  of the earth; but it is found by
experiment that gases, whatever may be their relative density,
swhen brought in contact, mix (39) uniformly with each other.
T'he mixture of the gases will even take place through thin membranes, (see author's lNrt. Phil., p. 22,) whether animal or vegetable; the least dense of the gases passing the most rapidly.
213. There is still one circumstance for consideration respecting
the atmosphere.  Since oxygen is necessary to combustion, to
the respiration of animals, and. to various other natural operations,
t)y all of which that gas is withdrawn from  the air, it is obvious
that its quantity would gradually diminish, unless the tendency
of these causes were counteracted by some compensating process.
This, to some considerable extent, is accomplished by vegetation,
as it is found that healthy plants, under the influence of the sun's
light, are constantly absorbing carbonic acid from  the air, the
carbon of which is retained, while the oxygen is returned to the
air, as we have before seen (191).  Still, it has been calculated
that the loss of oxygen employed in respiration, over the whole
surface of the globe, in 100 years, would not exceed 7-1   part
of the whole quantity contained in the atmosphere.
Comvpuounds of Nitrogen and Oxygen.
214. Oxygen combines with nitrogen in five different proportions, forming the compounds NO, NO,, NO3, NO4, and NO5; the
last three of which are acids.
215. Protoxide of Nitrog en, or Nitrous  Oxide —
NO; eq., (14 + 8 -) 22.
-This is a permanent, colorless gas, of a sweetish taste    L1_i
and smell. 100 cubic inches
of it weigh 47'22 grs., and          Preparation of Nitrous Oxide.
QUSSTIONS.-213. Is oxygen constantly absorbed from the atmosphere
by coaLbustion and by the respiration of animals? By what reverse process is carbonic acid absorbed and oxygen restored to the atmosphere?
214. How many compounds of nitrogen and oxygen are there? 215. Describe the protoxide of nitrogen.




196        X)MPOUNDS OF NITROGEN AND OXYGEN.
its density therefore is 1'527.  It is best prepared as shown in
the figure on the preceding page, by heating nitrate of ammonia,
by means of a spirit-lamp, in a glass retort to a temperature
of 450~ or 430~.  The sole products of the operation, when
carefully conducted, so as not to raise the temperature too high,
are water and the gas in question.  The composition of nitrate
of ammonia is NI3,,lHO,N05-which by heat is converted into
2 atoms of the nitrous oxide in question and 4 atoms of water.
Thus,
NH,,  10O, NO5 = 4 I-TO + 2 NO.
The water of course is condensed and remains with that in the
cistern, while the gas is collected as in other cases.  It is slightly
absorbed by water and should not therefore be allowed to remain
in contact with it.
Some substances burn in this gas with great brilliancy, as a
lighted candle and phosphorus; and sometimes the combustion
of iron wire in it may be effected, but not
without difficulty.  ]By a pressure of about
30 atmospheres, at a temperature of 32~, it
is compressed into a liquid, which freezes or
becomes solid at about 150~ below zero; and
by the evaporation of this solid, a temperature considerably lower than this has been
attained.
Its action on the system, when breathed,
is very remarkable, producing a species of
intoxication, which has acquired for it the
NitrolisOn.Odxiesupports  name of laughfing gas.  In a few cases, when
it has been inspired, injurious effects have resulted; and it should
never be breathed but with caution.
216. The analysis of nitrous oxide is made as follows; in a given
quantity of the gas accurately measured introduce a piece of potassium,
the gas being contained in a glass tube closed at one end and a little bent,
QUESTIONS.-How is the protoxide of nitrogen prepared?  Describe
the chemical changes that take place, and write the equation illustrating
them.  Is this gas absorbed by water?  Will it support combustion?
What is said of its effects upon the system when breathed?  216. Describe the mode of analyzing this gas.




COMIPOUNDS OF NITROGEN AND OXYGWEN.                197
(263) so as to retain the potassium while the open end is inmmcersed in mercury.  Now apply the heat of a lamp and the potassium takes fire immediately, absorbing all the oxygen and leaving the nitrogen.  This being
returned to the graduated tube in which the gns was first measured, will
be found to have the same volume as at first.  We learn therefore that the
protoxide of nitrogen occupies precisely the same volume as the nitrogen. contained in it would alone occupy. Now,
One volume of the protoxide weighs 1'527
One    "    "   nitrogen (subtract)'972
Half   "    "   oxygen, very nearly,'555
Nitrous oxide is therefore a compound of 1 volume of nitrogen and -
volume of oxygen, the whole condensed into 1 volume.
The same result is obtained by passing a quantity of the gas through
a heated porcelain tube by which it is decomposed, and I volume of
nitrogen and - volume of oxygen obtained.
217. 3Binoxide of Nitrogen, or Nitric  Oxidel-  NO2; eq.,
(14 + 16  ) 30.-This is also a gaseous substance, and is
easily obtained by pouring nitric acid upon pieces of copper
contained in  a glass  retort.
The arrangement shown in the   3
figure is very convenient for
the purpose.  Into the glass
vessel a put some clean pieces
of metallic copper, and then       a
introduce the cover, through                             ___ =
which passes the glass tube b, A        -        =
with a funnel at top, and ex-          Preparation of Nitric Acid
tending nearly to the bottom
of the vessel, and a lead tube, c, bent at right angles, to convey
away the gas as it is formed.  The cover must fit very accurately,
in order to prevent the escape of the gas, which is rapidly formed
as soon as a little nitric acid is introduced by the funnel and
tube b.  It may be collected over water, but a small proportion
is absorbed.
The changes which take place between the copper and the acid
are indicated as follows:4 NO0  + 3 Cu = 3 (CuO,NO5) + N0Q.
QUESTIONS.-217. How is the binoxide of nitrogen prepared?  What
are the chemical changes that take place?
17'




(198       COMPOUNDS O.F NITROGEN AND OXYGEN.
Thus, from 4 atoms of nitric acid and 3 of copper, there are
formed 3 atoms of nitrate of protoxide of copper, and one of the
binoxide of nitrogen.
218. Binoxide of nitrogen is a colorless gas, of a density of
1'039, 100 cubic inches weighing a little more than 32 grs.  Its
most striking property is its strong affinity
for oxygen, although most substances introduced into it in a state of comribustion are
-t:'~~)J       extinguished.  Charcoal and phosphorus,
however, if well ignited, burn in it with
great splendor, though the latter by careful
heating may be melted in it without ignition.  When allowed to escape into the.::.i    air, it forms, with the oxygen of the air,
>1 i~:,z   dense orange fumes of nitrous acid. Thus,
if a bell-glass receiver, filled with it over
water, be suddenly inverted in the air, the.Experiment -with Nitric   dense orange fumes of nitrous acid formed
Oxide.c
by its union with the oxygen of the atmosphere will rise for a few moments from  its interior, like smoke
fiom a chimney.
Let a receiver filled with this gas be placed in a basin of pure
water, as shown in the figure; and then
let a few bubbles of oxygen gas be forced.~,/    in by a pipe leading from  a gasometer, or
/  by imeans of a gas-bag.   As the oxygen
mixes with the gas within, nitrous acid
fumes are produced, which are immediately
ii Ziii;   absorbed by the water, giving it a slight
acidity, as may be determined by the usual
Nitric Oxide and Oxygen.
tests.   By continuing  to  force  in  the
oxygen gradually, and supplying the basin with water, all the
gas will at length disappear, being entirely absorbed by the
water as nitrous acid.
QUESTIONS. — 218 Describe binoxide of nitrogen.  What is produced
when it comes in contact with atmospheric air or oxygen? Describe the
experiment with a receiver filled with the gas over water and oxygen gas.




COMPOUNDS OF NITROGEN AND OXYGEN.                  199
Binoxide of nitrogen may be analyzed in the same manner as the
protoxide (216), by heating in a small quantity of it, accurately measured, a small piece of potassium or sodium, which absorbs the oxygen,
leaving the nitrogen free, the volume of which will be found just onehalf of that of the compound gas. The binoxide therefore is composed of
1 vol. of nitrogen, which weighs 0.972
1   "'  oxygen,       "       1.106
2   "6  binoxide,     "       2-078
The weight of 1 vol. or the density is therefore, as above stated,
2.078 -2 - 1.039.
219. Hyponitrous Acid -  NO,; eq., (14 + 24  -) 38.-This
acid is formed by mixing 4 measures of binoxide of nitrogen with
1 of oxygen, both perfectly dry, and subjecting the mixture to a
cold at least as low as zero.  It is a colorless liquid, which is at
once decomposed by water into nitric acid and the binoxide.  This
acid does not combine directly with bases, but its salts may be
formed by heating carefully the corresponding nitrates.  Thus by
heating nitrate of potassa, a part of the oxygen of the nitric acid
is expelled, and the nitrate is converted chiefly into hyponitrite
of potassa, as indicated in the following formula:
KONO5 = KO;,NO3 + 2 0.
The heat should be carefully applied, and the process arrested,
as soon as the oxygen which comes over begins to be mixed with
nitrogen   By treating the mass after cooling with strong alcohol
the hyponitrite is dissolved out, and may be obtained very pure.
220. Nitrous Acid —NO4; eq., (14 + 32 -) 46. —This substance is formed, as we have seen, whenever binoxide of nitrogen
comes in contact with oxygen.   It may also be prepared by
heating dry nitrate of lead in a retort, and passing the vapor
formed through a tube surrounded with a freezing mixture to
condense it.  A  piece of apparatus like that represented in the
QUESTroNs. —What is the effect when a piece of potassium is heated
in a tube containing nitric oxide? What is the volume of nitrogen that is
left?  219. What is hyponitrous acid?  Does it combine directly with
bases?  How may the hyponitrites be formed?  220. HIow may nitrous
acid be formed?




200        COMPOUNDS OF NITROGEN AND OXYGEN.
figure answers the purpose well.  It is to be placed in a proper
vessel, containing the freezing mixture, and
connected with the mouth of the retort.
As thus obtained, this acid has a density
of 1'42, and at 60~ F. is of an orange
color, but becomes, yellow when cooled to
320 and is nearly colorless at zero. Though
it requires a temperature nearly as low as zero to condense it to
the liquid form, the liquid boils at 820.  It does not combine
with bases, but forms compounds with some of the stronger acids.
It is decomposed by contact with water.
221. Nitric Acid —NO5; eq., (14 + 40 =) 54.-Nitric acid,
or bfquafortls, is usually seen as a liquid, and is best obtained by
decomposing nitrate
of potash -or nitrate
of soda  by strong
I~7   Am~" —-,sulphuric  acid, by
Z _IA__ —~ —2'~                             the aid of heat. The
salt, previously well
~ dried, is placed in a
~1-~I ~    retort of bard glass,
A, with  an  equal
~,~,I5.?'.. ~.~'~                   weight of strong sulPreparation of Nitric Acid.       plluric acid, in a furnace, and surrounded
at the bottom with sand.  A moderate heat is applied, and the
nitric acid, as it is separated, distils over into the receiver, 1B,
where it is condensed.  To render the condensation more complete, the receiver may be surrounded with a net-work, and cold
water from a pipe, i, made to fall constantly upon it.  The water
escapes by the troughs C C and ed. A furnace is not absolutely
necessary; the heat of a lamp is sufficient in all laboratory
operations.
Nitric acid, as thus formed, is a dense liquid, of a yellow or
orange color, and always contains more or less nitrous acid mixed
QUESTIONs.-May nitrous acid be obtained in the liquid forlm? Does
it combine with bases?  221. Hfow is nitric acid obtained?  WhaVt is the
0ommon or commercial name of this acid? Describe nitric acid.




COMPOUNDS OF NITROGEN AND OXYGEN.                201
with it.  In its most condensed state it has a density of 1'52, and
boils at 1880; its composition being then NO5,HO.  There is
another definite compound of the acid and water, N0,,4HO,
which has a specific gravity of 1'42, and boils at 253~. The first
contains 14 per cent. of water, and the latter 40 per cent.
By decomposing dry nitrate of silver by dry chlorine, nitric
acid may be obtained as a white crystaline solid, which is readily
soluble in water, forming the common aquafortis.
Strong nitric acid, when exposed to the atmosphere, emits dense,
white fumes, which are exceedingly suffocating.  Mixed suddenly
with water, it occasions a considerable rise of temperature; but
mixed with snow, it produces cold by the rapid liquefaction which.
is occasioned.
Nitric acid may be frozen by cold.  The temperature at which
congelation takes place varies with the strength of the acid.  The
strongest acid freezes at about 580 below zero. When diluted
with half its weight of water, it becomes solid at — 1.  By the
addition of a little more water, its freezing point is lowered
to  45~.
It is one of the most energetic acids known, and oxydizes many
substances powerfully. Powdered charcoal and oil of turpentine
are ignited by it, and most animal and vegetable bodies disorganized.  Phosphorus is oxydized so rapidly as to produce an
explosion. A small drop on the skin will, in a few seconds,
destroy its vitality, and produce a permanent yellow spot.  There
are two varieties of it in commerce, called single and double
itquafortis, the latter of which is much the strongest, and usually
is of a deep orange color.
222. This acid is sometimes produced by the union of the oxygen and
nitrogen of the atmosphere, as the effect of lightnings, and is found as
nitrate of ammonia in rain-water after a shower in summer. The same
effect may be produced by the electric spark, but the presence of water
and some base to combine immediately with the acid is necessary. Let
a tube be bent, as in the figure on next page, and the two ends covered
with metallic cups, one of them opening by a screw, so that the tube
may be half filled with a weak solution of potash. Now insert the screw
QUESTIONS.-Does nitric acid always contain water when in the liquid
form?  How may it be obtained in the solid form?  Maly aquafortis be
frozen?  What is said of its oxydizing power?  222. How may nitric
acid be formed by the direct union of its elements?




202       COMPOUNDS OF NITROGEN AND IHYDROGEN.
and divide the solution into two equal parts,
as nearly as may be, and connect it with the
prime conductor of an electrical machine,
and cause a succession of sparks to pass
through the portion of air contained in the
central part of the tube.  Upon examinaNitric Acid Produced.  tion, the solution will now be found to contain nitrate of potassa; the nitric acid of
which has been formed by the union of the constituent gases of the
atmosphere, as above explained.
223. Gold-leaf answers well, in most cases, as a test for nitric
acid.  The substance supposed to contain it is mixed with a
little hydrochloric acid, and the mixture, if nitric acid is really
present, should then be capable of dissolving the leaf.  If' it is
a salt that is to be tested, it should first be dissolved in water,
and the solution treated in the same manner with hydrochloric
acid and gold-leaf.
Nitric acid is much used in the arts for etching on copper, as a
solvent for the metals, &c., and as a tonic in medicine.  In the
laboratory of the chemist, it is in constant and most important
use in a great variety of operations.
Compounds of Nitrogen and fI]idrogcn.
224. Ammonia —NH3; eq., (14 + 3 -) 17.-  This gaseous
substance is the only compound of nitrogen and hydrogen that
is known.  It has been
called by a variety of
names,  as  hartshorn,
sp irits  of  hartshorn,
volatile aIlcali, &c.  It.........I'       has sometimes been de__i       t either alone or in combination with nitric acid
- - Collection of Ammonia.     (222); but it is readily
QUESTIONS.-223. What test of free nitric acid is mentioned? 224. What
is the composition of ammonia?  By what names is it known?




COMPOUNDS OF NITROGEN AND HYDROGEN.             203
obtained by heating the common solution of ammonia, called
aqua antmnoniw, or a mixture of sal ammonia and recently slaked
lime.  When the latter substances are mixed the odor of ammonia
is at once perceived, but it is evolved freely when the mixture is
moderately heated. It is rapidly absorbed by water, and should
therefore be collected over mercury. The reaction is as follows:
NH,,HC1 + CaO = Ca, C1 + H0 + NH3.
The two gases do not combine directly, but their union often
takes place when they are presented to each other in their nascent
state (226), in various chemical operations. Thus, during the
rusting of iron, when moisture is present a portion of ammonia is
frequently produced, and when zinc is dissolved in dilute nitric
acid the solution will usually be found to contain a little nitrate
of ammonia.
Ammonia is also produced during the destructive distillation
of animal substances; and the name hartshorn came into use
from the circumstance that deer's horns were made use of for
the purpose.
225. Ammonia is a colorless gas, and possesses a very pungent
odor, by which it may always be distinguished.  By a pressure
of six or seven atmospheres it is compressed into a liquid; it also
takes the liquid form by the application of intense cold, under the
ordinary atmospheric pressure.  A lighted candle plunged into it
is extinguished, but a small jet of it burns in oxygen gas. Its
density is about 0'59, 100 cubic inches weighing 18'29 grs.
Ammonia is composed of one volume of nitrogen and three
volumes of hydrogen, condensed into two volumes.
1 vol. of nitrogen weighs 0-972
3   "  hydrogen  4"  0.207
2   "  ammonia  "   1'179
One-half of this, or 0-589, is the weight of one volume, or the
theoretical density of the gas.
QUESTIONS. —How may ammonia be obtained fromn aqua ammonia?
What is said of its absorption by water? What is said of the formation
of ammonia during the rusting of iron?  225. What are some of the
properties of ammonia?




204      COMPOUNDS OF NITROGEN AND HYDROGEN.
This gas is largely absorbed by water, which at 32~ is capable
of dissolving 500 or 600 times its own volume of it, and then
forms the liquid ammronia, or aqua animoniw  of commerce.
As the gas is absorbed, the water increases considerably in
volume, so that, when saturated, its density is only 0-87, and it
contains 32 per cent. of the gas.
Liquid ammonia is best prepared by the use of a Woulf's
apparatus, which is constructed as follows.  First a vessel of
D                                            i
Preparation of Aqua Ammonia.
glass or metal, A, containing the substances from which the gas
is to be evolved, is placed upon a furnace or other source of heat,
and connected by a tube with a series of three-necked bottles,
B, C, D, &c., each partly filled with water.  The first tube from
the vessel containing the materials, it will be observed, terminates
below the surface of the water, in the bottle B, so that the gas
coming through it is made to rise through the water; but the tube
connecting this with the next bottle C terminates in B near the
top, but extends downward beneath the surface of the water in C.
The same thing will also be observed of the tubes connecting
together the other bottles.  Now when the gaseous ammonia is
evolved it passes over, and rising through the water in C, is
absorbed, but any other gas passes on in like manner to the next
bottle, and so on until it escapes in the air.  If any of the ammonia escapes from the first bottle, as will be the case after the
water has become in part saturated. it will be likely to be conQuESTIONS.-What is said of the absorption of ammonia by water?
Describe the mode of preparing the liquid ammonia.




COMPOUNDS OF NITROGEN AND HYDROGEN.               205
densed in the next, or farther on in the series.  In the centre
of each bottle is a tube, open at both ends, but extending downward so as to terminate below the surface of the liquid.  It is
designed merely as a safety tube; it is plain that if, in using the
apparatus, any obstruction occurs in one of the tubes, the effect
will be to force out the liquid through these central tubes without
danger to the apparatus; so also any external pressure will at once
be equalized by the entrance of the air through these tubes. This
apparatus is used for many similar purposes.
In order to ensure the full saturation of the water in the bottles
they must be kept cold by means of ice.
Ammonia has all the properties of an alkali in a very marked
manner. Thus it has an acrid taste, and gives a brown stain to
turmeric paper; though the yellow color soon reappears on exposure to the air, owing to the volatility of the alkali.  It combines also with acids, and neutralizes their properties completely.
This substance is used extensively in the laboratory of the
chemist, and in medicine. Solution of ammonia, taken internally in considerable quantity, has been known to produce death;
and the gas, if inspired too long, is apt to occasion inflammation
in the throat and lungs.
226. Nascent State.-This phrase, which occurs above, is used to indicate the state of a body as it is evolved from a compound containing it.
In the case alluded to, the rusting of iron in the presence of moisture,
the oxygen which unites with the iron is mostly supplied by the water;
and the hydrogen, as it is thus set free, is said to be in its nascent stale,
and just at the moment is capable of combining with the nitrogen of the
air to form ammonia, which it will not do under other circumstances.
Many other substances, when thus separated from compounds of which
they form a part, manifest a disposition to form compounds with bodies
with which they will not combine directly.
QuEsTIoNs.-What is the design of the central tube in each bottle?
What is said of the alkaline properties of ammonia?  226. What is
meant by the nascent state of a body?  What is saia of the properties
possessed by substances in this state?
18




206                      C:H1LORINT.
GnouP II.
CHLOrINE    Electro-negative elements, which constitute a very distinc4
IODINE     natural family. Each forms a single acid compound with
BROMINE  hydrogen; and all combine with the metals, forming comFLUORImE J pounds that are similar.
CHLORINE.
Symbol, Cl; Equivalent, 35'4; Density, 2.44.
227. History.-Chlorine was discovered by Scheele, in 1774,
and for many years was regarded as a compound, but its true
character, as a simple element, is now universally admitted.  It
is not found uncombined in nature, but is abundant in its compounds, especially common salt, which is so generally distributed
over the surface of the earth.  It receives its name from  the
Greek chloros, green, because of its yellowish-green color.
228. Preparation.-Chlorine gas is easily prepared by pouring
strong hydrochloric acid upon half its weight of peroxide of nmanganese, in a glass retort, and applying a gentle heat.  It may be
collected over hot water, but not without some being absorbed by
it.  It should always be collected in bottles with good stoppers,
in which it may be kept for some time. The following formula
indicates the changes that take place:Mn02 + 21ICl = MnC1 + 2I-10 + Cl.
A cheaper process, and nearly as convenient, is to mix, intimately, three parts of common salt with one of the peroxide, and
pour over it two parts of sulphuric acid, previously diluted with
an equal weight of water. In this case,
Mu02, + NaC1 + 2SO3 = MnO,SO3 + NaO,SO3,    Cl.
QuEsTIoNS.-What are the substances of the second group? What is
said of them as a group? 227. What facts are mentioned in the histomy
of chlorine?  From what is the name derived?  228. Describe tle
method first mentioned for preparing chlorine. Why should hot water
be used in collecting it? Describe the mode of preparing it by the use
of common salt. What are the chemical changes that take place?




CHLORINE.                           207
The chlorine  by  this
process is evidently supplied by the salt (chloride  of  sodium)  and
there are formed  sulphate of the protoxide
of manganese and sulphate of soda.
It is afforded also by
various  other preparations.                              Preparation of Chlorine
229. Properties.-Chlorine  is a dense gas, of a yellowish
green color, as above stated, and has an astringent taste, and
rather disagreeable odor.  The weight of 100 cubic inches is
76 grains, which gives a density of 2 44. By moderate pressure
it is converted into a liquid, which has a density of about 1 33.
As cold water absorbs the gas readily it cannot be collected over
it without great loss;
but, in consequence of
its great specific gravity,
it may be collected in
an open vessel, by direct displacement of the         a
air.  Let a be the flask      -         a:
containing  the  materials, and c a receiver
in which the gas is to
be collected, the tube   __ _
firom  the flask extending nearly to the bot-  Collection of Chlorine by Displacement of the Air.
tom. The chlorine gas
being so much heavier than air, fills up the receiver just as
water would if conveyed into it in the same manner; and if the
process is expeditiously conducted, the chlorine may be collected
nearly pure.
QuEmSTIONs.-229. Describe the properties of chlorine  How may it
be collected by displacement of the air?




208                          LO R IN E.
Prepared by either of the modes described above the gas is
always mixed with watery vapor, from which it is readily separated
by passing it through a tube containing lumps of dry chloride
of calcium.  After being evolved from  the materials used it
should be made to pass through a bottle containing a small
quantity of water, to separate any hydrochloric acid that mar
Preparation of Dry Chlorine.
have come over, and then through the chloride of calcium tube,
which will absorb all the watery vapor; it may then be collected
in a bottle by displacement of the air, as just
described.  The bottle should be provided with
a well-ground glass stopper.
Chlorine is allied to oxygen in many of its
properties; a lighted candle continues to burn!I~?j  A in it for a time with a dull red flame, giving off
1;l~8\l  a dense black smoke of uncombined carbon;
l!i;jIti    land phosphorus takes fire in it spontaneously,
burning with great brilliancy.   Some of the
metals also, if in thin leaf or fine powder, take
Supports Combustion. fire in it spontaneously. For this purpose, a
QUESTIONS.-How may the gas be obtained free from moisture? Will
zh'orine support combustion?  How is phosphorus affected by it?




C HLO RI N E.                       209
-.[ ——.;/  tall jar should be used, as represented in.....i.   the figure on the left; and the bottom
should be covered with sand, to prevent   AR
the breaking of the glass by the heated
chloride falling upon it.  It has a strong
affinity for hydrogen, and a mixture of
the gases explodes by the approach of
flame, and by the electric spark, precisely
as a mixture of oxygen and hydrogen.......    If a piece of paper, moistened with oil of v i
turpentine, be suspended in a bottle of
Comusio /chlorine, it takes fire spontaneously, by X         I
of Metal in the chlorine combining with the hydrogen amrpentined In
Chlorine.  of the turpentine; at the same time the
carbon of the turpentine is liberated, in a state of minute division,
as a dense black smoke.   The bottle containing the chlorine
should have a large mouth.
One of the most important properties of chlorine is its bleaching
power, all vegetable and animal coloring matters being speedily
destroyed by it.  Powdered indigo, slightly moistened and dropped
into a bottle containing it, even if it is considerably diluted with
air, soon loses its color entirely; and pieces of calico, of different
colors, suspended in it, are affected in the same manner, without,
in the least, injuring the texture of the cloth.  It is therefore
much used in preparing rags for the manufacture of writingpaper, and also in bleaching cotton and linen goods. Writing
done with common ink is easily removed by it; but printers' ink,
being an oily preparation, is not attacked by it.
Chlorine is also a powerful disinfecting agent, removing at once
all offensive effluvia from sewers, vaults, and other places where
they may have collected.  For this purpose, bleaching-powder (to
be described hereafter) is moistened with water, and placed in
shallow dishes in the apartments to be fumigated.
The aqueous solution of chlorine is best prepared by the use
QUEjsTIoNs.-What is said of the affinity of chlorine for hydrogen?
\t;at is ~is effect upon oil of turpentine?  What occasions the dense,!:l:k s;noke? What is said of the bleaching properties of chlorine?
\l hat is said of it as a disinfecting agent?
18*




210        COMPOUNDS OF CHLORINE AND OXYGEN.
of a Woulfe's apparatus (225).  The solution readily dissolves gold.
leaf, forming trichbloride of gold.
If one of the bottles is kept cold by means of ice, a crystaline
solid will be deposited, which is a compound of one atom of chlorine and ten atoms of water.
230. By dexterously putting some of these crystals in a glass tul
and sealing it hermetically, liquid chlorine may be obtained. By
slight elevation of temperature the solid melts
and the water and chlorine separate, the latter
of which, in consequence of the pressure,
takes the liquid form.  While sealing the
tube the end containing the crystals must be
Preparation of Liquid Chlorine. kept cold by means of ice.
The aqueous solution, if prepared in the dark and kept constantly
from the action of light, undergoes no change (173), but if once exposed
for a few moments only to the sun's rays, decomposition of the water
commences, hydrochloric acid is formed, and oxygen set free.
The proper test of chlorine, either free or in combination, is solution
of nitrate of silver; silver and chlorine always forming a dense white preci pitate, quite insoluble in water, but readily soluble in aqua ammonise.
Compounds of Chlorine and Oxygen
231. The compounds of chlorine and oxygen are five in number,
as follows, viz.:-CO,ClO,,l0,04,C105, and C107, all of which are
acids; but as the affinities of these substances for each other are
very feeble, their compounds are all decomposed by slight causes.
232. Hypochlorous Acid — ClO; eq., (35 4 + 8 =) 43 4.-This is a
gaseous substance, of.a yellowish-green color, like that of chlorine, but
a shade deeper. It exists in combination with lime in the common
bleaching-powder.
233. Chlorous Acid-ClO,; eq., (35.4 + 24 =) 59-4-Is prepared by
the action of oil of vitriol upon chlorate of potash.
234. Iypochloric Acid-C104; eq., (35.4 + 32 =) 67.4.-This compound is also gaseous, and of a deep yellowish color. It is formed by
the action of sulphuric acid upon chlorate of potash. If a few grains
QUESTIONS.-HOW is the aqueous solution of chlorine prepared? May
the compound of chlorine and water be crystalized?  230. How may
these crystals be used to form liquid chlorine? Can the aqueous solution be long preserved without decomposition? What test for chlorine
is mentioned? 231. What compounds of chlorine and oxygen are there.?
What is the number of eqluivalents of oxygen in each of these?




COMPOUNDS OF CIILORINE AND HYDROGEN.              211
of chlorate of potash are placed in a wine-glass, and a little sulphuric
acid poured in, the glass will be soon filled with the gas, which will be
recognised by its color. If now a rag, wet with oil of turpentine, be presented to it, on the end of a wire or a stick, it will be inflamed, and the
gas at the same time exploded.
235. Chloric Acid-C105; eq., (35.4 + 40 --— ) 75'4.-Chloric
acid is obtained by passing a current of chlorine through a strong
solution of potash, with which it combines as it is formed, producing chlorate of potash.  At the same time with the chlorate
of potash there is also produced much chloride of potassium; the
reaction takes place between 6 equivalents of chlorine and 6 equivalents of potash, according to the following equation:6K0 + 6C1 — 5KC1 + KO,C105.
The chlorate being only slightly soluble in water, some separates
in crystals by a little evaporation of the water, while the chloride
remains in solution.
To obtain the acid in a separate state, chlorate of baryta is first
produced and then decomposed carefully by sulphuric acid.  The
BaO,SO which forms is separated by filtration, and the chloric
acid obtained as a syrupy liquid.   It is decomposed at a temperature of 104~.
Perchloric Acid possesses no characters that render it of any special
interest.
Compoznds of Chlorine and Ilydrogen..
236. Hydrochloric Acid —ICI; eq., (8354 + 1 -) 36.4. —
This is the only known compound of chlorine and hydrogen;
and, in solution in water, has long been used in the arts, under
the names of m~uriatic acidc, and sp)irit of salt.  It is formed by
the action of diluted sulphuric acid upon common salt.  The
sulphuric acid should be diluted with about an equal weight of
QuESTIONs. —235. Iow is chlorate of potassa formed? How is celhoric
acid procured from this salt? 236. What is the only compound of
chlorine and hydrogen that is known?  How is hydrochl aric acid
prepared?




212       COMPOUNDS OF CHLORINE AND HYDROGEN.
water, and be allowed to cool before being used.  The changes
which take place are as follows:NaC1 + S0,I-0 = NaO,S03 + IIC1.
From this it appears that the water of the oil of vitriol is
essential to the process; it is decomposed, yielding its oxygen to
the sodium to form soda, which combines with the acid, and its
hydrogen to the chlorine to form the hydrochloric acid.
Abundant fumes of the gaseous acid will be given off, which
should in no case be allowed to diffuse themselves in a room
where there are articles of delicate apparatus made of metal,
as they will be sure to be corroded after a little time, if not
immediately.
It is also formed by the direct union of its elements.  When
equal measures of chlorine and hydrogen are mixed together, and
an electric spark is passed through the mixture, instantaneous
combination takes place, heat and light are emitted, and hydrochloric acid is generated.  A similar effect is produced by flame,
by a red-hot body, and by spongy platinum.  Light also causes
them  to unite.  A mixture of the two gases may be preserved,
without change, in a dark place; but if exposed to the diffused
light of day, gradual combination ensues, which is completed in
the course of twenty-four hours.  The direct solar ray, like flame
and the electric spark, produces an explosion by a sudden inflam.
mation of the whole mixture; but to insure the success of the
experiment, the gases should be very pure, and the chlorine
recently prepared over warm water.  The glass vial containing
the mixed gases, after being filled, should be instantly covered
with a black cloth, which can be suddenly removed by a stick, or
wire, after it is placed in the sun's rays.
Hydrochloric acid is, of course, a chloride of hydrogen.  When
pure it is a colorless gas, of which 100 cubic inches weigh 39'38
grains, giving it a density of 1'25. By strong pressure it may
QUEsTIONS.-Explain the equation. Is the presence of water essential
to the formation of hydrochloric acid? May it be formed by the direct
union of its elements? What several means are mentioned by which the
gases may be made to combine?  What are some of the properties of
hydrochloric acid?




COMPOUNDS OF CHLORINE AND HYDROGEN.               213
be compressed into a liquid.  It is quite irrespirable, and in.
capable of supporting combustion.  Water absorbs it with avidity,
taking up, under favorable circumstances, no less than 480 times
its own volume. During the absorption it increases considerably
in volume, and the saturated solution has a density of 1'21, and
contains about forty-two per cent. of the acid.  In preparing the
liquid hydrochloric acid, a Woulfe's apparatus (225) is used, only
a very little water being contained in the first bottle, in which
most of the impurities mixed with  the gaseous acid will be
deposited.  In the open air, copious fumes of the
gas constantly arise from the liquid, which produce
a cloud of smoke if any ammonia be present in
the air.  Thus, let a little aqua ammonite be    l,
poured into a glass vessel, A, with a large mouth,
and then invert over it a tumbler, the inside of?
which has been thoroughly moistened with common    d-:l
hydrochloric acid.  The two gases, coming in contact, unite, and fill both glasses with a dense, white Hydrochloric Acid
smoke, which is solid hydrochlorate of ammonia
(159), in a finely divided state.  The same thing is shown when
a glass rod moistened with hydrochloric acid is brought near an
open vessel containing aqua ammonie.
Gaseous hydrochloric acid is composed of equal volumes of chlorine
and hydrogen united without condensation.
One volume of chlorine weighs    2'440
One    "    hydrogen'           069
Forming two vols. hydroc-h ric acid 2.509
The weight of 1 vol., or the theoretical density of the gas, is therefore
2 509 _1_264.
2s5 o 9-_ 1.254.
2
237. Aqua regia, so called because of its ability to dissolve
gold and platinum, is a mixture of two parts of hydrochloric to
one of nitric acid.  Let a single leaf of gold be placed in a wine.
QUESTIONS. —'V1hat is said of the absorption of hydrochloric acid by
wa.ter?  What is said of the fumes produced by the gas with ammonia 
NWhat is said of the volumes of chlorine and hydrogen which unite to form
this acid? 237. What is aqua regia? Why is it so called?




214       COMPOUNDS OF CHLORINE AND NITROGEN.
glass containing a little hydrochloric acid, and another leaf in a
separate glass with some nitric acid; the gold will remain undissolved in both glasses for any length of time; but, on mixing the
contents of the glasses, the whole of the gold will be speedily dissolved. The real solvent in this case is the chlorine, which is
liberated by the action of the acids'upon each other.  The reaction
is shown by the following equation. Thus,
NO5 + 21C11 = N03 + 2HO + Cl.
This decomposition, however, proceeds only so far as to saturate
the liquid with chlorine, but if heat is applied to expel the chlorine,
or a metal placed in the liquid with which it will unite, new quan.
tities of the acid are decomposed.  Nitrohydrochloric acid, therefore, is a source of chlorine in a very concentrated state, and is
capable of dissolving several substances which are not attached
by any single acid.
Hydrochloric acid may readily be distinguished by its odor and
volatility, and by its giving, with a solution of nitrate of silver
(230), a precipitate of the white chloride of silver, which is
blackened by exposure to the light.
Liquid hydrochloric acid is extensively used for various purposes in the arts, and is one of the most important chemical
agents of the laboratory.
Covpounzc7s of Clorine and Nitrogen.
238. Terchloride of Nitrogen. —NC3,; eq., (14 + 106'2 =)
120'2.-There is known only a single compound of these elemlents, the terchloride of nitrogen.  It is prepared by passing a current of chlorine through a solution of the hydrochlorate,
or other salt of ammonia, and takes the form of a dense yellow
liquid, which is seen in small globules at the bottom of the solu
tion.  The reaction is expressed in the following equation:NIH3,,HC1 + 6C01- 4HC1  + NC13.
QuEsTIoNs. —What compound of gold is formed?  How may hydro.
cliloric acid be known?  238. What comlpound of chlorine and nitrogen
is there? What is said of it?  Explain the equation.




IODINE.                           215
The liquid has a density of 1.65, and may be distilled under a
pressure less than one atmosphere, but at 2120 it explodes with
the utmost violence.  So also it detonates violently by the mere
contact with phosphorus, many of the oils, &c., and never should
be handled but with the greatest care.
IODINE.;Symbol, I; Egquivalent, 127; Density, 4'95
239. history.-Iodine from (iodes, violet color) was discovered
in the ashes of sea-plants, from which it is still prepared, by Mi.
Courtois of Paris, in the year 1812. It is found also in certain
ores of silver and zinc, in sea-water, and in the water of certain
mineral springs.
240. Preparation,-As stated above, the iodine of commerce
is obtained from  the ashes of sea-plants, especially the fulcus
i         r         i     from          1t
Preparation of Iodine.
ypalmatus.   The ley obtained by lixiviating the ashes is first.
evaporated, to separate a portion of the carbonate of soda awll
QUESTIONs.-239. When was iodine discovered? In wh'l1t is it fountl?
240. What is the mode of preparing iodine from the ashes ot sea-plants 




216                        IODINE.
other saline compounds it contains, which are less soluble than
the iodine compounds —chiefly the iodides of sodium and magnesium-and are therefore first to crystalize out fiom the solution;
the residue is then mixed with peroxide of manganese and sulphuric acid, and a gentle heat applied, when the iodine distils
over, as a beautiful violet-colored vapor, into a receiver prepared
for the purpose, where it is condensed.  A simple apparatus like
that represented in the figure on the preceding page answers well
for the distillation.
A good method to show the evolution of iodine, is to heat in a
glass globe, over a lamp or ignited charcoal, a small quantity of
sulphuric acid, and throw suddenly into it 25 or 30 grains of iodide
of potassium.  A  large quantity of iodine will instantly be set
free, and its vapor fill the globe.
241. Properties.-Iodine, at ordinary temperatures, is a soft,
friable, nearly black solid.  Usually it is in small shining crystals, which have a metallic lustre, and a density of 4'95.  Heated
a little above 2120, it melts, and is then converted into a beautiful violet-colored vapor, which has a density of 8'70 (air being
1), and 100 cubic inches weigh 270'1 grains. Iodine is a nonconductor of electricity and heat, and is allied to oxygen and
chlorine in many of its properties.  Its odor resembles that of
chlorine, but is less offensive.  It is sparingly soluble in water,
requiring about 7000 times its own weight of this liquid for complete solution; but alcohol and ether dissolve it fieely, forming a
deep brown solution. A few of the crystals pressed upon the
skin produce a deep stain, which however soon disappears.
Starch affords a delicate test of iodine, forming with it a beautiful blue. The starch should be prepared by dissolving it in hot
water, and allowing it to cool before using.  Let a little hot water
be poured upon ashes obtained by burning a piece of sponge, and,
after filtering, add a drop or two of solution of starch; then pour
in a few drops of siulphuric or nitric acid, and stir it gently,
and almost always the blue color will be observed, indicating the
presence of iodine.
QuESTIONxs.-241. Describe the properties of iodine.  What is daio
of its solubility in water?  In alcohol and ether?  What test of i diin
is mentioned?  I-low may iodine be detected in sponge?




COMPOUNDS OF IODINE AND OXYGEN, HYDROGEN, ETC. 217
Iodine has not been much used in the arts, but is largely employed in medicine. In the Daguerreotype process (76), it is
essential; and recently it is said to have been employed in dyeing.
Cornpounds of iodine and Oxygen, H.ydrogen, &c.
242. Iodine and oxygen combine in three proportions, producing iodous IO,,04 iodic IO5, and periodic IO,, acids; neither of'
which however possesses any special interest.
243. Hydriodic Acid, HI, (iodide of hydrogen,) is a gaseous
substance, of a specific gravity 4'39, and in many of its properties
strongly resembles the corresponding chloride of hydrogen (hydrochloric acid).  It is absorbed by water, and then forms the liquid
hydriodic acid.
It is best prepared by placing in
a glass tube alternate layers of iodine,
powdered glass (to prevent too rapid
action) and posphorus, slightly moistened with water.  Iodide of phosphorus  is first formed, which  is
decomposed by the water, producing       Preparation of Iydriodic Acid
phosphorous acid and hydriodic acid,
the last of which being gaseous makes its escape, and may be
collected in a dry bottle by displacement of the air, or it may be
condensed in water.
244. Teriodide of Nitrogen-NI3.-From  the weak affinity that exists
between iodine and nitrogen, these substances cannot be made to unito
directly.  But when iodine is put into a solution of ammonia, the alkali
is decomposed; its elements unite with different portions of iodine, and
thus cause the formation of hydriodic acid and teriodide of nitrogen.
The latter subsides in the form of a dark powder, which is characterized,
like chloride of nitrogen, by its explosive property.  It often detonates
spontaneously as soon as it is dry, and even when moist, by the slightest
causes. Heat and light are emitted during the explosion, and iodine and
nitrogen are set free, the former of which may be seen at the instant in
the form of vapor.
QuErsTIoNs.-Whfat use is made of iodine?  242. What compounds
of iodine and oxygen are mentioned?  243. Describe hydriodic acid
How is it formed? 244. Describe teriodide of nitrogen.
19




2X8                       BR rOM   N rE
Chlorine combines with iodine when made to pass over it in a dry
glass tube, or when passed through water in which crystals of iodine are
diffused.  The two substances form several different compounds, but they
are not at present well understood.  One of these, probably the protochloride, IC1, has been used in the Daguerreotype process.
BRO MINE.
Symbol Br; Equivalent, 80; Density, 2'97.
245. History,-Bromine was discovered in 1826, in sea-water;
and received its name, bromine (from  bromnos, offensive odor), in
consequence of its exceedingly disagreeable smell.  Recently it
has been obtained in large quantities from the waters of some
of the salt-springs in Pennsylvania and Virginia.
246. Preparation.-The usual mode of preparing bromine is a
little complex.  First, the brine from  the spring is evaporated,
and the common salt removed by crystalization, then the motherliquor, or bittern, as the uncrystalizable residue is called, is treated
with a current of chlorine to decompose the bromides of magnesium, sodium, &c., and sulphuric ether afterwards added, by which
the bromine that has been separated from  its compounds by the
chlorine is taken up, and rises to the surface as a solution of
bromine in ether.
Another method is to mix with the solution sulphuric acid and
peroxide of manganese, as in the preparation of iodine; and then
distilling with a gentle heat. The same apparatus (240) may be
used as in the preparation of iodine, but the receiver must be
kept cool by a current of cold water.
247. Properties. —Bromine is a liquid of a blackish-red color,
and specific gravity 2'97.  At a temperature a little below zero
it is frozen, and boils at about 1170, forming a vapor of a beautiful blood-red color, and specific gravity 5'39, air being 1.  It
QUsESTIONS.-What is said of the compounds of chloride and nitrogen?
245. When was bromine discovered?  From what is the name derived?
246. From what is it obtained?  What is the mode of preparing it?
247. Describe its properties.




COMPOUNDS OF BROMINE, WITH OXYGEN, ETC.    219
stains the skin yellow, like iodine, but less intensely.  Vapor
of bromine ignites phosphorus spontaneously, and a lighted
candle burns in it a short time.
Bromine, in many of its properties is closely allied to chlorine
and iodine. Taken into the system it is highly poisonous, and its
vapor possesses considerable bleaching power.  With starch it
forms a yellow color.
Like chlorine, it forms a compound with water, which crystalizes when exposed to the cold of a freezing mixture of salt and
snow. The compound is Br,10H0O.
Bromine is sometimes used in medicine, and much more
extensively in photography, especially in the Daguerreotype
process.
Compouncls of Bronmine, with Oxgeln,  Ijdrzogcn;, &c.
248. Bromic Acid, BrO5, is the only well determined compound of bromine and oxygen. It is a liquid, and may be procured of the consistency of syrup. It is very corrosive, and sour
to the taste, and by a temperature of 2120 is decomposed.
249 Hydrobromic Acid, HBr, is a colorless gas of a density
2-73.  To prepare it, a tube of the form of the letter W  is provided, and the part at the left
filled with pieces of phosphorus
mixed with pounded glass,.and
the whole moistened with water.
Into the end at the right some
bromine is then poured, and a
cork firmly inserted; and into    Preparation of iydrobromic Acid.
the other end a smaller tube is
fixed, by means of a perforated cork, to convey away the hydro.
bromic acid as it is formed. The whole being ready, a gentle
heat is applied to the part containing the bromine; and the vapor
as it is formed, attacking the phosphorus, first produces bromide
QUESTIONS.-What other elements does bromine resemble?  Does it
combine with water? What use is made of it? 248. Describe bromic
acid. 249. Describe hydrobromic acid, and the mode of preparing it




220                      FrL UORINE.
Of phosphorus, which is at once decomposed by the water, forming
phosphorous and hydrobromic acids, the latter of which, being
g;aseous, passes off, and may be collected over mercury.
The gas is rapidly absorbed by water, like hydrochloric acid,
and the concentrated solution gives off fumes in the air.  In
most of its properties it closely resembles hydrochloric acid.
By intense cold and pressure the gas may be condensed to the
liquid form.
250. Hydrobromic acid is composed of equal volumes of vapor of bromine and hydrogen combined without condensation. Thus,
1 vol. vapor of bromine weighs 5.390
1 "     "    hydrogen  "      069
2 vols. hydrobromic acid,    5'459
One volume of the acid therefore weighs 2.729.
FLUORIN E.
Slymbol, F; Equ'vallent, 19; Density, 1 29.
251. History and rroperties.-Fluorine has long been known
to exist, but it has not, until recently, been obtained in a separate
state.  It is found in nature in considerable abundance in the
mineral called fiuor spar, which is a compound of this substance
with calcium, the metallic base of lime.  It is a brownish-colored
gas, of specific gravity about 1'29 (probably), and bleaches like
chlorine.
Such is its affinity for other substances that it attacks them
with violence, even gold and platinum; and can be prepared and
kept only in vessels made of fluor spar, which, being already
saturated with the substance, is not acted on by it.
QUESTIOnS.-What is said of the absorption of hydrobromic acid by
water?  250. Considered as gaseous, what is its composition? 251. Give
the history and properties of fluorine. What is said of its affinity for
other substances?  Of what only can vessels be made to contain it?
Why is not this substance acted on by it?




COTMPOUNDS  OF FLUORINE.                      221
Comlpounds of Fluorine.
Fluorine seems to be incapable of uniting with oxygen, but
combines with hydrogen, forming the acid compound HF.
252. Hydrofluoric Acid —iHF; eq., (19 + 1 _ ) 20. —This acid
is formed by subjecting powdered fluor spar, moistened with strong
sulphuric acid, to a very gentle heat in a leaden vessel.  The acid
distils over as a pungent, corrosive, vapor, but may be condensed
in a leaden receiver, that is kept surrounded with ice.  The
reactions are as follows:CaF + SO,,11HO = CaOSO 3 + IHF.
As thus formed, the acid has a density of 1'07, and manifests
ai strong affinity for water, with which it combines with great
energy. It attacks glass powerfully, combining with its silica,
and may therefore be used to etch it.  This is done by spreading a
thin coat of bees'-wax or varnish upon the glass, and tracing the
design upon it, taking care to cut quite through the wax.  The
liquid acid is now poured over the coated surface, or it is exposed
a few minutes to the acid vapor, and the wax afterwards removed;
the design will then be found beautifully traced upon the glass.
This acid attacks animal substances powerfully, and, therefore,
should always be handled with great care.
Fluorine unites also with chlorine, iodine, bromine, and some others
of the elements, but the compounds are not important.
QUEsrIoNs.-Does fluorine combine with oxygen? 252. Describe the
mode of preparing hydrofluoric acid. Describe its properties.  How may
it be used for etching upon glass? What is said of its action upon ani.
rmal substances? Does fluorine combine with chlorine, iodine, &c.?
19*




222                      SU L PI I U JI.
GnouP III.
SUIPIIUR  )  Elements in many of their properties closely resembling
SELEiNIUM   each other, and forming similar acid compounds with
TELLURIUM J oxygen and hydrogen.
S U L P HII U R.
Symbol, S; Etquivalent, 16; Density, 1.99.
253. history and Preparation.-Sulphur, called also braimstone, has been known from the remotest antiquity.  It occurs, as
a mineral production, in many parts of the world, particularly in
volcanic regicns, as in the neighborhood of Naples, in some of the
Sandwich Islands, and in the island of Sicily. In combination
with several of the metals, as iron, lead, copper, &c., it is still
more abundant, and is found in almost every place. From one
of its compounds with iron, called iron p9yrites, it is procured in
large quantities, for the purposes of commerce.  It is found, also,
in many organic bodies, as in eggs, in the hair, horns, and hoofs
of animals, and in the seeds of black mustard.
The island of Sicily furnishes a large part of all sulphur of
commerce; the native sulphur here occurs in immense beds mixed
more or less with gypsum, lime, and other earthy matter. This
sulphurous earth is first heated in pots so as to melt the sulphur,
which is dipped out with ladles, the earthy matter settling to the
bottom.  The sulphurous earth remaining as sediment is then
heated in earthen pots, which are arranged in double rows, and
entirely inclosed in mason-work, except at the top, where is an
opening by which they are charged and emptied. At the sides,
in the open air, pots are arranged to receive the sublimed sulphur,
which, taking the liquid form, passes finally into buckets situated
as shown in the figure on next page.
QUESTIrNS.-What elements constitute group 3d of the metalloids?
258. Give the history of sulphur. With what is it found combined?  in
what Organic bodies is it contained? Describe the mode of separating it
from the earthy mlatter with which it is mixed.




SUL  P   U R.                      223
Separation of Sulphur.
The figure represents a section of the mason-work with two of
the included pots, and also the external receivers with which they
are connected, and the buckets.
254. Properties.-Sulphur is a brittle solid, of a greenishyellow color, emits a peculiar odor when rubbed, and has little
taste. It is a non-conductor of electricity, and is excited negatively by friction. It fuses at 2260, and becomes nearly as liquid
as water; but if the heat be raised as high as 430~, it becomes
so tenacious that the vessel containing it may be inverted without
spilling it, and is then of a dark molasses color.  When heated
to at least 4280, and then poured into water, it becomes a ductile
mnass, which may be used for taking the impressions of seals.
After some time, it changes into its ordinary state.
Fused sulphur has a tendency to crystalize in cooling. A crystaline arrangement is perceptible in the centre of common -roll
sulphur; and, by good management, regular
crystals may be obtained.  For this purpose,
several pounds of sulphur should be melted in
an earthen crucible; and, when partially cooled,
the outer solid crust should be pierced, and the
crucible quickly inverted, so that the inner and
as yet fluid parts may gradually flow out.  On Sulphur Crystalized.
breaking the solid mass, when quite cold, a confused arrangement
of prismatic crystals will be found in the interior.
Sulphur is dimorphous (184); that is, it is capable of. crys.
talizing in two distinct primary forms, the oblique rhombic
QUESTIONS.-254. Describe the properties of sulphur. IHow may it be
crystalized? Why is it said to be dimorphous?




2'2 4                    SU LP H UR.
prism, and the rhombic octahedroni the first belonging to the
inonoclinic, and the second to the trimetric system.
Sulphur is very volatile, and begins to rise in vapor even before
it is completely fused. At about 750~, it boils, and the vapor,
if in a close vessel, will be condensed on any cold surface, forming
the flowers of sulphur.  The density of its vapor is about 6'65.
When vapor of sulphur is brought in contact with vapor of alcohol, they unite; but solid sulphur is quite insoluble in alcohol, or
water, but dissolves in boiling oil of turpentine, and in sulphide
of carbon.
By melting the flowers of sulphur and pouring it into moulds,
the roll-sulphur of commerce is formed.  In this form it is very
brittle, and will sometimes break by the heat of the hand.  It is
the only substance known that always becomes negatively excited
by friction, whatever may be the nature of the substance used as
the rubber.
The vapor of sulphur combines readily with iron and other
metals, attended with all the phenomena of combustion.  Let the
breech of a gun-barrel be heated to
redness, and a lump of sulphur
dropped into it, and then let the
muzzle be instantly closed by a
cork; a jet of vapor of sulphur will
issue violently from the touch-hole,
which will be inflamed as it enters
Iron Wire and Vapor of Sulphur.   the air; and a bunch of small iron
wire, held in:it, will burn freely, forming sulphide of iron, which
will fall indi;drops.
The sulphur of commerce generally has an acid reaction, probably in consequence of a slight oxidation that is gradually
taking place.  Organic substances,'n contact with sulphur are
always more or less acted upon by the acid or acids thus produced.
QUEsTIoNs.-What is the boiling point of sulphur?  What are the
flowers of sulphur?  Is it soluble in water or alcohol?  I-low is rollsulphur formed? What is said of its electrical state when rubbed? How
may iron wire be made to burn in vapor of sulphur'?  Why does the sulphur of commerce usually have an acid reaction?




COMPOUNDS OF SULPrUR AND OXYGEN.                225
Uses of Sulphur.-Sulphur is used extensively in the arts, and
in medicine.  It is employed in the manufacture of gunpowder,
sulphuric acid, the different kinds of matches, vermillion, &c., and
for taking impressions of seals. In medicine, it is used in cuta,
neous diseases, and as a cathartic and alterative
Compounds of Sulphur and Ox:ygen.
255. Sulphur and oxygen form as many as seven different compounds, viz.:1. Hyposulphurous acid............................ 8202.
2. Trisulpho-hyposulphuric acid................ S505.
3. Bisulpho-hyposulphuric aci   d..          S405.
4. Monosulpho-hyposulphuric acid............... S30O.
5. Sulphurous acid.................................. SO2.
6. Hyposulphuric'acid................................. S205.
7. Sulphuric acid...................................... SO3.
Of these, the fifth and last are by far the most important; and
only these will be here described.
256. Sulphurous Acid — S02; eq., (16 + 16 =) 32. -This
substance is gaseous at ordinary temperatures, and is the sole
product of the combustion of sulphur in the open air, or in dry
oxygen gas. It is more conveniently prepared, however, by heating strong sulphuric acid in contact with mercury or pieces of
copper.   One equivalent of the sulphuric acid gives up one
equivalent of its oxygen to unite with the metal, and the oxide
thus formed is immediately dissolved by a second atom  of the
sulphuric acid, while the sulphurous acid passes off as a gas. Thus,
tHg + 2S03 = ItgO,803 + SO2.
Another very easy method is to heat in a retort a mixture of 6
prts of powdered peroxide of manganese and 1 part of sulphur.
QurESTIONS.-iWhat use is made of sulphur in the arts?  255. How
many compounds of sulphur and oxygen are mentioned 9 256. Describe
sulphurous acid, and the mode of preparing it.




202 6      COMPOUNDS OFI SULPHIUR AND OXYGEN.
]By this mode, the peroxide gives up one-half of its oxygen, which
unites with sulphur to form the sulphurous acid, and protoxide
of manganese remains in
the retort.
An arrangement like
that figured in the margin, answers well for its
preparation, by  either
mode. As the gas forms
it is made to pass through,/ /it. 1 a little water, to condense
r —-f —                    any vapor of sulphuric' ==.....acid that may have come
over and it may then be
Preparation of Sulphurous Acid.,    it may then be
collected over mercury.
Sulphurous acid is a dense, colorless gas, 100 cubic inches of
which weigh 68 55 grains, giving it a specific gravity of 2'24.  It
is distinguished from all other gases by its suffocating odor, which
every one has recognized in burning sulphur.  It is absorbed
largely by water, and may be condensed into the liquid form by
moderate pressure, or by a cold of zero. A little of the liquid
may be obtained very easily,
a4 a  ~ a by putting a small quantity of
mercury and sulphuric acid in
Preparation of Sulphurous Acid in Liquid a bent tube, as represented in
the figure, sealing it hermetically, and supplying heat to the extremity, a, which contains the
materials, while the other, b, is kept cool by means of ice, or the
evaporation of ether.  The liquid will be soon found to collect in
the cool part of the tube.  Care should be taken not to heat the
tube too much, lest it should burst.
A better method to procure the liquid is to prepare a tube, (as
in the figure on next page,) by closing one end, and drawing out
a part in the middle to a capillary bore, and then inserting it in a
freezing mixture of snow and salt.  If, now, a current of the gas,
first dried by passing through a chloride of calcium tube, be made
QUESTIONS.-What is said of the odor of sulphurous acid? Itow may
it be. obtained in the liquid form?




COMPOUNDS OF SULPIIHUR AND OXYGEN.                227
to enter the open end of the tube, it will be condensed and collectet  in the lower part.  When this
part is nearly filled, still keeping in the freezing mixture, the upper part may be separated and the lower
part hermetically sealed, and the liquid preserved for
any length of time.  Or a tube like that represented
in  the  figure  on  the  right
margin may be used.  The bulb
at the centre part is to be surrounded with a freezing mixture
fPr eparation in a suitable vessel, as a glass Preparation of Liquid Sulphurous Acid. tumbler; and when a sufficient      phurous Acid.
quantity of the fluid has accumulated, the two ends of the tube
may be hermetically sealed before it is removed from its place in
the freezing mixture.  Under the ordinary atmospheric pressure
it becomes liquid at about 14~, but at a temperature of 590 it
requires a pressure of about 2 atmospheres. The liquid has a
density of 1'42.  When allowed to escape in the open air it evaporates rapidly, producing a cold of — 60  to — 76, according
to the temperature of the air and other circumstances.  By severe?
cold it may be frozen, and with water it forms a compound
(S029HO) which may be solidified.
257. Sulphurous acid is composed of 1 volume of oxygen and' of a
volume of vapor of sulphur, condensed into 1 volume. If we burn a
small quantity of sulphur in a glass globe over mercury, the sulphur is
converted into sulphurous acid, but after cooling the volume of gases is
found to be unchanged. The acid therefore occupies the same space as
the oxygen entering into its composition  Therefore if we subtract the
weight of the volume of oxygen from that of a volume of sulphurous
acid, there should remain r of a volume of vapor of sulphur.  This we
find to be the case very nearly. Thus,
1 vol. sulphurous acid weighs 2.247
1 " oxygen (subtract) "   1.106
v " vapor of sulphur,      1141
QUESTIONS.-Describe the two'modes mentioned for collecting sul.
phurous acid in glass tubes.  At what temperature does it become
liquid? What is the density of liquid sulphurous acid? What is said
of the cold produced by its evaporation?  257. What is the composition
of one volume of sulphurous acid?




228        COMPOUNDS OF SULPHUR AND OXYGEN.
We have heretofore (254) taken the volume of sulphur vapor to be
6.654, one-sixth of which is 1 109. The discrepancy in the results is
occasioned by the great difficulty in obtaining accurately the real weight
of the volume of sulphur vapor.
208. Sulphurous acid is much used for bleaching, especially
articles of straw; which, in a moist state, are suspended in an
atmosphere charged with the gas. For this purpose, the gas is
formed by burning sulphur in the air, in some enclosure, as a box
or empty cask, in which the articles to be bleached are suspended.
259. Sulphuric Acid —SO3; eq., (16 + 24 =) 40.-This acid
is always seen as a dense liquid, not unlike oil in appearance;
and, having been formerly obtained altogether by the distillation
of green vitriol (sulphate of iron), it received the name, oil of
vitriol, by which it is now often known. It is prepared at the
present time, at Nordhausen, Germany, by the same mode. Green
vitriol is thoroughly dried by heat, and then distilled, at a high
temperature, by which it is decomposed, and the acid passes over
and condenses as a brown oil-like liquid, which still contains one
eq. of water for every two eq. of the acid. Its composition, therefore is 2SO,,HO.  Its density is 1'9, or nearly twice that of
water. When this liquid is again distilled, at a moderate heat, a
dry, silky solid is obtained, which is the pure compound, S03;
but it possesses no acid properties until water is added, which
changes it to common sulphuric acid. This solid has a strong
affinity for water, and hisses like a hot iron when thrown into it.
260. The common method of preparing the oil of vitriol of commerce is, to burn a mixture of sulphur and nitrate of potash,
or soda, in a furnace so contrived that the current of air which
supports the combustion conducts the gaseous products into a
large leaden chamber, the bottom of which is covered to the
depth of several inches with  water.  Numerous complicated
changes take place in the leaden chamber, during the combustion
of the sulphur, by which the oxygen from the air is transferred
QUESTIONS.-258. What use is made of sulphurous acid? 259. Describe
sulphuric acid. How is the Nordhausen acid prepared? How may the
solid acid be obtained from it?  What is the composition and density
of the Nordhausen acid? 260. What is the mode of preparing the corn.
mon oil of vitriol of commerce?




COMPOUNDS OF SULPHUR AND OXYGEN.               229
to the sulphurous acid formed by the combustion of the sulphur,
converting it into sulphuric acid.
In the first place, as the mixture burns, sulphurous acid is
formed (256), and binoxide of nitrogen; -the latter by the
decomposition of the nitric acid of the salt; —and the two gases
witha current of air are carried together into the leaden chamber, the binoxide of nitrogen, NO2, at the same time absorbing
oxygen, and being thus converted (218) into nitrous acid (NO4).
Secondly, these two gases, in the absence of water, are capable
of combining to form a crystaline solid, the composition of which
is NO4,2SO2, and which, on coming in contact with water, is at
once decomposed into binoxide of nitrogen and sulphuric acid.
Thus,
NO4,2SO2  2SO3 + NO2.
Or, more properly,
NO4,2SO2, 210= 2(SO3,HO) + NO,.
Thirdly, if at the same time as the mixed gases from the coinbustion of the sulphur enter the chamber, steam be also forced
in, the crystals just alluded to are not formed, but all the reactions described take place in the order mentioned, the hydrated
sulphuric acid, as it forms, falling like rain to the bottom of the
chamber.
The binoxide of nitrogen, being set free, combines again with
atmospheric oxygen present, forming nitrous acid, NO4, as before,
and this, with the sulphurous acid, by the reaction of water, again
producing sulphuric acid, and so on indefinitely.
These are the essential reactions that take place in the process,
but they are often, perhaps always, accompanied by others, which
however tend to the same result, viz., the conversion of the sulphurous acid, formed from the burning sulphur, into sulphuric
acid.
QUESTIONs. -Describe the reactions which take place. Firstly?
Secondly? Thirdly? Do other reactions tending to the same result
usually accompany the above?
20




230        COMPOUNDS OF SULPHUR AND OXYGEN.
Firstly, a portion of the nitrous acid, NO4, in the leaden cham.
her, when but little moisture is present, is converted into mono.
hydrated nitric acid, and hyponitrous acid, NO,. Thus,
2NO4 + HO = NO,HO + NO,.
If a large quantity of moisture is present, the nitrous acid is converted into hydrated nitric acid and binoxide of nitrogen.  Thus,
6N04 + nHO = 4N05,nHO + 2NO,.
Any hyponitrous acid, NO,, that may have been formed, as
indicated in the second equation above, when the supply of
moisture is increased, undergoes a similar change, producing
nitric acid and binoxide of nitrogen.
Secondly, sulphurous acid, SO,, by the reaction of hydrated
nitric acid, is converted into hydrated sulphuric acid, while the
nitric acid, N,0, by the loss of oxygen is changed to nitrous acid,
NO4. Thus,
SO2 + NO5 + nHO = S03,nHO + N04.
We have, then, as the result, sulphuric and nitrous acids, the
former of which mixes with the water at the bottom of the chamber, while the latter, remaining in the gaseous state, is ready
again to go through the same reaction as before, being thus made
a vehicle for conveying oxygen from the atmosphere to the sulphurous acid.
In some manufactories, no nitrate of potash is used, but the
sulphur is burned alone, and nitric acid, in proper vessels, is
placed in the leaden chambers in such a situation that it shall be
evaporated by the heated sulphurous acid and other gases entering from the furnace; reactions similar to those above take place
with the same results.
The figure following will serve to illustrate the process. C C is
a section of the chamber lined inside with sheet lead, and supported at the ends by mason-work.  At A is the furnace for
QUESTIONS.-Describe the other reactions tending to the same result
which accompany those already mentioned.




COMPOUNDS OF SULPHUR AND OXYGEN                   231
C gpr-'-9    C'
-A
Manufacture of Sulphuric Acid.
burning the mixture of sulphur and nitric salt, the fumes of which
are carried directly into the chamber, now filled only with air,
and at B a steam boiler from which steam  in one or more jets is
constantly entering the chamber, for the purposes described above.
A valve at the the top allows the escape of the spent gases.
261. For a class experiment, the apparatus figured below answers
well to illustrate the mode of manufacturing this acid.  A large
Illustrates the Preparation of Oil of Vitriol.
balloon glass, A, is provided, containing a small quantity of
water, a two-necked flask, B, partly filled with small pieces of
QUESTIONS.-Describe the first figure on this page. 261. Describe the
apparatus figured in connection with this paragraph.  What is illustrated
by it?



232        COMPOUNDS OF SULPHUR AND OXYGEN.
copper, and a second flask, C, containing mercury and strong oil
of vitriol. These two flasks, B and C, are connected with the
balloon, A, by means of tubes inserted in perforated corks, as
shown in the figure; and a lamp then applied to C, from which
sulphurous acid fumes will soon be made to pass over to the balloon, A. Into the flask, B, some nitric acid, a little diluted with
water is now poured by the long-necked funnel, which, acting
upon the copper (217), will soon supply binoxide of nitrogen to
mix with the other gases contained in A.  The red fumes of
nitrous acid will at once appear in A, and all the changes take
place described above, resulting in the production of a small
quantity of oil of vitriol.  Through the cork in the mouth of th,,
balloon glass, A, two glass tubes bent at right angles are inserted,
by which the air within may be changed, by blowing into one
of them by the mouth.
In the manufacture of this acid on a large scale, the acid, as it
comes from the leaden chambers, always has an excess of water,
its density varying from  1'35 to 1-50.  It is then heated in
leaden pans until its density becomes about 1'75, and, finally, in
platinum retorts, by which all excess of water is expelled, and its
density is brought to 1'84. Its boiling point is then 617~, and
its freezing point — 30~.
Oil of vitriol, we thus see, always contains water; the most concentrated, that of Nordhausen, as stated above, containing one
atom to every two atoms of the acid; or, expressed by symbols,
its composition is 2S0,,HO. As prepared by the ordinary mode,
it contains one atom of acid to one of water, or its composition is
S0,,HO. If to about 49 parts of common oil of vitriol we add
9 parts of water, we have an acid the specific gravity of which
will be about 1'78, and its composition SO,,2HO. It will then
freeze at about the same temperature as water, but on the application of heat the solid does not melt until the temperature rises
to 450.
A fourth compound of water and sulphuric acid is SO,,3HO,
which has a specific gravity of 1'63.  It boils at about 338~.
QUESTIONS.-What is the density of the acid as it is drawn from the
leaden chambers?  How is a portion of the water expelled?  What is
the proportion of water in the Nordhausen acid?  In common oil of
vitriol? Are there other definite compounds of this acid and water?




COMPOUNDS OF SULPHUR AND OXYGEN.                  233
Common oil of vitriol is the monohydrated acid, SO,,HO.
Exposed to the open air it rapidly absorbs moisture, and increases
in volume, so that a small vessel partly filled with it, if left open,
is often found running over after a few days.
Place a few drops of it in a watch glass in the pan of a small
balance, and exactly counterpoise it by weights placed in the
other pan; in a very few moments the effect of the absorption
of moisture will be seen.  It may therefore be used to separate
moisture from gases which are not acted on by it, by passing the
gas through tubes containing pieces of pumice stone moistened
with the acid.
Sulphuric acid is, perhaps, the most important of all the acids,
as by its aid nearly all the others are produced.  Its acid properties are very decided; aided by heat, it decomposes animal and vegetable substances, causing a
deposition of charcoal, and formation  of water,
which it absorbs.  Its affinity for water is very    Jll
great, and the combination of the two substances          1
is attended with the production of considerable
heat.  If a mixture of four parts of the acid and Mixture of S03oio
and 1HO produces
one of water is stirred with a test-tube containing Heat.
sulphuric ether, the heat generated will be sufficient to cause the
ether to boil.
Free sulphuric acid is occasionally found in the water of
springs, as at Byron, Genesee County, New York; but such
cases are rare.
Uses.-Sulphuric acid is applied in the arts, and in the laboratory, to very many important uses; as, in the preparation of the
other acids, the extraction of soda from common salt, the manufacture of alum, sulphate of iron, chlorine, &c. It is also used
as a solvent for indigo, and in the various manufactures of the
metals.
Test. —Chemists possess an unerring test of the presence of
sulphuric acid. If a solution of chloride of barium is added to a
QUESTIoNs. — How may the absorption of water from the atmosphere
by oil of vitriol be shown? What is said of the affinity of this acid for
w;vter? What is the effect when it is mixed with water? What use is
made of it? What test of its soluble salts is mentioned?
20*




234      COMPOUNDS OF SULPHUR AND HYDROGEN.
liquid containing free sulphuric acid, or any sulphate in solution,
it causes a white precipitate, sulphate of baryta, which is characterized by its insolubility in acids and alkalies.
Compounds of Suupnhur and 14Hydrogen.
262. There is only one well-determined compound of sulphur
and hydrogen, the protosulphide, or hydrosulphuric acid, HS;
though by a particular process a second compound is obtained, as
a heavy, yellowish liquid, which is supposed to be a bisulphide,
IIHS. The former only will be here described.
263. Hydrosulphuric Acid —HS; eq., (16 +1 =) 17.-This
substance, often called sulphuretted hydroyen, is gaseous, and may
easily be prepared by the action of diluted sulphuric acid upon
powdered protosulphide of iron, formed by intensely heating a
bar of iron, and then rubbing it with a roll of sulphur, or by
heating intensely common iron pyrites (native bisulphide of iron)
for some time in a covered crucible.
One mode of preparing hydrogen, it will be recollected (197,
204), is by the action of dilute oil of vitriol upon metallic iron;
but if instead of iron we use sulphide of iron, a particle of sulphur
being liberated at the same time as the particle of hydrogen, the
two combine, and gaseous sulphide of hydrogen is evolved. The
reactions are as follows: —
FeS + SO3,,H-O    FeO,SO, + HS.
An apparatus like that represented in the figure on the next
page is convenient for the purpose.  The sulphide of iron is first
introduced, and after the cork with the tubes is inserted, the acid
is added by means of the long-necked funnel.
The gas may also be prepared by the action of hydrochloric
acid upon native sulphide of antimony finely pulverized, aided
QUESTIONS.-262. What only well-determined compound of sulphur
and hydrogen is mentioned?  263. How is it prepared? How is sulphide of iron prepared for the purpose?  Describe the reactions that
take place.




COMPOUNDS OF SULPHUR AND IHYDROGEN.               235
by a gentle heat.  The reactions then are as expressed in the
following equation:SbS + HC1 = SbC1 + HS.
iydrosulphuric acid is a colorless
gas, of a most offensive odor, similar
to that of putrefying eggs; 100 cubic
inches of it weigh 36'93 grains, giving
it a density of 1'191.  At the ordinary
summer temperature, it takes the liquid
form under a pressure of about 15 atmo-    E
spheres, and by a cold of — 122~ is
frozen.  A jet of it burns readily in the
open air, forming water and sulphuroushu id.
acid.                                       Hydrosulphuric Acid.
acid.
Cold water absorbs 2 or 3 times its own volume of the gas, and
acquires its peculiar odor and taste; but the gas is all given off
again when the water is boiled.  Water impregnated with the
gas, if kept for a time, becomes milky from  the decomposition
of the gas, and the separation of the sulphur contained in it.
Sulphur-s2l)rings, which occur in many places in New York,
Virginia, and other States, are springs, the waters of which are
naturally impregnated with  hydrosulphuric acid.  They may
always be recognised by the offensive odor, which extends to a
distance around them, and by their
blackening pieces of silver coin, by
the formation of sulphide of silver.
WVater, possessing all the properties
of that of the most noted sulphursprings, may be prepared artificially,
by passing a current of this gas, for a    u
few minutes, through cold water.  Let
a little diluted sulphuric acid be poured Preparation of Sulphur Water.
upon some powdered sulphide of iron, in a small bottle, and then
insert a cork with a beait tube, as shown in the figure, the other
Q;ESTrONs. — What are some of the properties of hydrosulphuric acid?
What is said of its absorption by water?  What are sulophur 2y)rinzgsr
Hlow may sulphur water be prepared artificially?




(236        COMPOUNDS OF SULPHIUR AND HIYDROGEN.
end of which shall dip in a vial of cold water.  After the gas
has bubbled through  it a few  minutes, it will be found  fully
inompregnated~
This gas blackens many colorless metallic salts, by the formnation of metallic sulphides.   An  amusing  experiment may  be
~ - -... —. _   - performed in the following manner:
Let a picture  be  traced  on  white'  paper with a solution of sugar of lead,
which is perfectly colorless, and the
picture, at a little distance, will be
". d |  invisible.  Let the back of the paper
be now moistened by means of a wet
sponge; and, after tacking it to the
wMll, let a  current of this gas be
directed against it, and all the parts
traced by the lead  solution will inI;cturie.          stantly become dark brown, or black,
by the fornation of sulphide of lead onl the paper.
2MA, The composition of this gas is easily determined by heating some
tin-foil in a measured quantity of the gas.  Let the tube
be of the form represented in
~?}~'c'"'~:~X..             the figure, and let the tin-foil
be placed in the upper part by
*_  <1'~i?,~l]]i    ~',                 means of a. wire after the gas,'~.~,~~,      carefully mleasu re d, has been
introduced; and then having
the open eld of the tube immersed in mercury, heat the
-----— " —--  tin-foil by means of a spilit-- lamp.  All the sulphur   will
Analysis of IIS.            be immediately absorbed by
the mletal, and there will remain only the hydrogen, which will however
occupy the same space as before.  Now,
One volume of hydrosulphurie acid gas weighs 1.191
One    6"    hydrogen (subtract)'       069
There remains for the sulphur, 1' 1122
This is very nearly (162) the weight of one-sixth of a volume of vapor of,u:tsa'IroNs-..What is said of the action of sulphur water upon miany'ol'orless metcallic sallts?  264. 1iow may the composilion of hlydcrosulj
phurie acid be determined?




COMPOUNDS OF SULPHUR AND CHLORINE.              237
sulphur; so the composition of hydrosulphuric acid must be one volume
of hydrogen and one-sixth of a volume of sulphur vapor, condensed to
one volume.
Covmpouncds of Sufvphur and Cld7orine.
265. There are, it is believed, several compounds of these two
elements, but two only (or perhaps, three) have been obtained in
a separate state, the dichloride, S201, and the chloride, SCL.
266. Dichloride of Sulphur-S2C1; eq., (2 x 16 + 354 =-)
67'4.-The formation of this compound requires an apparatus
which is somewhat complex.  To prepare the chlorine, a flask, A,
containing some peroxide of manganese, is provided, a tubulated
retort, D, containing a quantity of sulphur, and a three-necked
bottle, B, for the purpose of washing the chlorine.  These are
connected together by tubes, as shown in the figure, and some
hydrochloric acid poured into A by means of the crooked tube,
B3         flilll~pi
Dichloride of Sulphur.
the design of which is to prevent any escape of the gas, as would
bhe the case if the liquid was poured directly in.  Everything
QUESTIONS.-265. What is said of the compounds of sulphur and
lchlorine? 266. How is dichloride of sulphur formed?




238        COMPOUNDS OF SULPHUR AND CHLORINE.
being ready, heat is applied to the sulphur in D, so as to melt it,
and also a gentle heat to A, to cause a slow evolution of chlorine.
This gas, after being washed in B, is dried by passing through a
chloride of calcium tube T, and finally comes in contact with the
vapor of sulphur in D, where the compound in question (S2C1)
is formed, and passes as a vapor into the receiver, E. This being
kept cool by a stream of cold water from the vessel F, the dichloride
is condensed, and any atmospheric air or other gaseous matter passes
off by the waste-tube inserted in E. The liquid thus obtained must
be separated from a little sulphur it contains by a second distillation.
Dichloride of sulphur is a reddish-yellow liquid, having a disagreeable, and very peculiar odor, which boils at about 280~.  Its
specific gravity is 1'69, and that of its vapor 4'668, It is immediately decomposed by contact with water.
Dichloride of sulphur, considered in the gaseous state, is composed
of one volume of chlorine, and one-third of a volume of sulphur vapor,
condensed into one volume.  Thus,
One volume of chlorine weighs         2.440
One-third vol. sulphur vapor weighs;''i.5 42 2.218
One vol. dichloride (or its density),  4.658
The density thus obtained, called the theoretical density, it will be
seen, differs but slightly from  that given above, obtained by direct
experiment.
267. Chloride of Sulphur-SC1; eq., (16 + 354 =) 51.4.This compound  is prepared by passing a current of chlorine
through a quantity of the preceding, until it is entirely saturated,
and then distilling at a temperature of 1470.  It is a deep red
fluid, having a density of 1'62.
The density of its vapor is 83549. Considered in the gaseous state, it
is composed of one volume of chlorine and one-sixth of a volume of sulphur vapor, condensed to one volume.
One volume of chlorine weighs         2.440
One-sixth of a vol. sulphur vapor weighs 1.109
One volume of chloride,               3-549
The compounds of sulphur with nitrogen, iodine and bromine, being
of little interest, are not here described.
QUESTrION.-Describe the properties of dichloride of sulphur. 267.1 How
is chloride of sulphur formed? Describe its properties.




SELENIUM.                          239
S E L E N I U BII.
ymnzbol, Se; Equivalent, 39'5; Density, 4'32.
268. History, etc.-Selenium  was discovered, in  1817, by
Berzelius, and received its name from  serene, the moon.  It is
usually found associated with sulphur, in some of its compounds
with other substances, especially sulphide of iron (iron pyrites).
It is found also in combination with copper, lead, mercury, silver,
and other metals.  From  any of these it is prepared by several
different processes.
Selenium, at ordinary temperatures, is a solid of a deep brown
color, the shade varying a little, according as it is seen in a
powder or in a solid mass.  When melted and suddenly cooled,
it has a vitreous conchoidal fracture, and becomes negatively
electrical by friction in very dry air.  When heated to 2120, it
becomes partially fluid, and perfectly soft a temperature a little
higher than this. Heated to 7000, it sublimes like, sulphur, which
it closely resembles in many of its properties.  At a temperature
of 2120, or a little higher, especially if it has been heated considerably above this and again cooled down, it is viscid, and may
be worked like softened sealing-wax, and drawn out into small
threads.
When heated in the open air, it readily takes fire and burns,
exhaling a strong odor not unlike that of decaying horse-radish,-  a
character by which it may always be distinguished.
Compouncls of Selenium, and Oxygen.
269. Selenium forms with oxygen three compounds, SeO, SeO2, and
SeO,. The latter two are acids, and in many of their properties quite
similar to sulphurous and sulphuric acids, to which they correspond in
composition.
QUFsSTIONS.-268. In what is selenium  found?  Describe its pro.
perties. 269. What compounds does it form with oxygen?




240  COMPOUNDS OF SELENIUTM AND OXYGEN.-TELLURIUMo
270. Selenous Acid-SeO2; eq., (39'5 + 2 X 8=) 555. —To prepare
this acid, a retort contain
ing a mixture of chlorate
of potash and peroxide of
manganese is connected, as
represented in the figure,
with a tube bent downxward
Be   \24k/ _1  so as to receive a quantity
of selenium  at the lowest
]     I; 9   part.  Heat is then applied
to the chlorate by which
oxygen gas is evolved, and
also to the selenium in the
tube.   As  the  selenium
- rip artin- of- Se~ibecomes heated, it burns
slowly, with a blue flame,
and the selenous acid is collected in the upper part of the tube in
the form of white acicular crystals, which are very soluble in water.
271. Selenic Acid —SeO3; eq., (39 5 + 3 X 8 -) 63.5.-Selenic acid
is prepared by burning selenium with nitrate of potash, when seleniate
of potash is formed, from which the acid may be obtained in the liquid
form. Its chief interest is found in its close resemblance to the corresponding sulphur acid, SOs, and in the fact that it is capable of dissolving
gold.
With hydrogen selenium forms a compound, hydroselenic acid, HSe,
which is gaseous, ant  irritating to the eyes, nose and lungs.  It is absorbed by water, lieA hydrosulphuric acid, and the solution, like that
of hydrosulphuric acid, is decomposed by contact with the air.
The compounds of selenium with sulphur, chlorine and bromine are
not of sufficient interest to require attention in this work.
TELLURIU M..Syrlbol, Te; EtivCLa7ec t, 64'5; Density, 6 2.
272. History, etc. —Tellurium  is a rare substance, which has
sometimes been found native, but is usually combined with the
metals, as gold, silver, bismuth and lead.  It is generally prepared from the telluride of bismuth, which is found in Schemintz
in Hungary.
QUESTIONS.-270. Describe the mode of preparing selenous acid.
271. Describe selenic acid.  What compound does selenium form with
hydrogen?  272. Describe tellurium.




COMPOUNDS OF TELLURIUM WITH OXYGEN, ETC,   241
Tellurium, in some of its physical properties, closely resembles
the metals with which it is often associated; but in its chemical
properties it is more nearly allied to the non-metallic elements,
especially sulphur and selenium.
When pure, it has a clear white color, and bright metallic
lustre; and in its general appearance is not unlike antimony.  It
melts at a dull red heat, and, by slow and careful cooling, may
be obtained in crystals, the primary form of which is the rhombohedron. At a very high temperature it becomes gaseous.
Comnpounds of Tellufriumn with Oxygen, Etc.
273. Tellurium forms with oxygen two acid compounds, viz., tellurous
acid, TeO2, and telluric acid, TeO3, which, as will at once be seen, are
similar in composition to the corresponding compounds of sulphur and
selenium.
With hydrogen, also, like the two elements just named, it forms a
single gaseous compound, hydrotelluric acid, HTe, the smell of which is
even more offensive than that of bydrosulphuric acid.
Tellurium combines with chlorine, iodine, bromine, sulphur, selenium, etc.
GRouP IV.
P1uoSPHO:Rus    Two elements which are solid at ordinary temperaIsENIOa      tures, and similar in many other properties.  Many of.  their compounds are isomorphous.
PHOSPHORUS.
Symbol, P; Equivalent, 32; Density,  P8 to 2.
274. Iistory.-Phosphorus was discovered by an alchemist
of Hamburg, in 1669; and received its present name (from
1plos, light, and pherein, to carry) from  the circumstance that,
at ordinary temperatures, it always appears luminous in the dark.
QUESTIONS.-273. What is said otfthe compounds of tellurium with
oxygen? 274. Give the history of plosphorus.
21




242                     Pio SP  Ho RUcS.
It is not found in nature in a separate state; but in combination
with oxygen and lime, it is very generally diffused, being contained in all fertile soils, without exception, and in many vegetable
and animal substances.
275. Preparation.-Phosphorus, at the present time, is propared entirely from bones, which are first heated in the open air
until they become white, so as to destroy all the animal matter
they contain.  Miore than half their weight remains, which is
chiefly phosphate of lime.  This is then ground to a fine powder,
and digested, for one or two days, with dilute sulphuric acid, in
the ratio of 3 parts of the bone ashes to 2 parts of acid and 15 or
20 parts of water.
The action of the sulphuric acid upon the phosphate of lime, is
to take away a part of its lime, forming with it sulphate of lime;
and as the whole of the phosphoric acid of the original phosphate is then in combination with only a part of its lime, it is
plain that this must now be a super-phosphate of lime.  Th is
latter is soluble in water, while the sulphate of lime which has
been formed is insoluble; more
water is therefore added, and a
clear liquid obtained, which is evidently solution of super-phosphbate
__________        ~of lime.  This liclquicd is now evaprated until it begins to be quite
l_ l-    thick, when it is mixed intimately
with charcoal, in fine powder, and
bt~egi    thoroughly dried.  It is next introduced into an eartheln retort,;~b'~qi;,~,~  I!;             a, which  is placed in a proper
mi~**{ tl~iia';~-!,m~, ffurnace, as  represented  in  the
Prearaionof....      figure; and to the neck of the
retort, a wide copper tube, b, is,
attached, which connects with a vessel of water. The heat is
then gradually raised, when the phosphorus distils over, and is
condensed in the waiter.  Much combustible gaseous matter, also,,
QOTESTION. 2 75. Describe the mode of preparing phosphorus.




PHOSPHORUS.                            243
comes over and escapes by the second tube, inserted in the
water-vessel.
The affinity of charcoal for oxygen at low temperatures is
not very considerable, but when highly heated it is intense, and
sufficient to abstract the oxygen from the phosphoric acid of the
acid phosphate of lime, causing the liberation of the phosphorus.
This, taking the gaseous state, distils over and is condensed to
the liquid form, and finally solidified.
The phosphorus thus procured is still impure, and is to be
melted in hot water, and pressed through porous leather.
276. Properties.-Pure phosphorus is of a light flesh-color,
and nearly transparent.  At common temperatures, it is a soft
solid, of specific gravity about 2, and may easily be cut with a
knife.  At 1080 it fuses, and at 5540 is converted into vapor,
which has a density of 4'326.  It is soluble, by the aid of heat,
in naphtha, in fixed and volatile oils, and in some other liquids.
By the fusion and slow cooling of a considerable quantity, it may
be crystalized, and also from its solution in bisulphide of carbon.
The crystals belong to the monometric system.
It is usually seen in long, slender sticks, of a waxy lustre,
which are made by melting the phosphorus under water and
pouring it into glass tubes.
Phosphorus may be distilled without difficulty.  For a small
operation, fit a green glass retort to a tube bent, as represented
in the figure, and having its
extremity drawn out to a fine 
point, but not closed.  Sepa-          i
rate the retort and tube, and          "!i
put in the first a small quantity
of phosphorus, and in the latter
a little water; and again connect them firmly together.  If         Distillation of Phosphorus.
now the retort is carefully
heated, the phosphorus will gradually distil over and collect in
the water in the lowest part of the tube.
QuSTIsroNs.-What is the effect produced by the charcoal? 276. Describe phosphorus.  In what is it soluble? In what form is it usually
seen!




2414                    P E O SP HO Ra US.
Phosphorus is exceedingly inflammable. Exposed to the air,
at common temperatures, it undergoes slow  combustion, emits
a white vapor of a peculiar alliaceous odor, appears distinctly
luminous in  the dark, and  is gradually consumed.  On this
account, phosphorus should always be kept under water.  In
the open air, even the heat of the hand, aided by the slightest
friction, is sufficient to inflame it; and it should therefore always
be handled with the greatest caution. It burns in the air with a
brilliant, yellowish-white light and intense;iiiiilill  heat; but in oxygen gas, its combustion is
I ~, |ii ~ll, ")j  particularly splendid.  A  good method for
performing  the experiment is to place a
piece of phosphorus in a small cup on a
stand, a few  inches high, in a basin of
-  i1h _    water, and, having ignited the phosphorus...... H!it?,, —  by touching it with a piece of heated wire,
________ — ________  dexterously to place over it a large bell-glass,
Combustion of Phos-  previously filled with oxygen.  By careful
phorus in Air or Oxygen. management, but little of the oxygen will
be lost. It may also be made to burn under warm water, by
forcing  a current of oxygen  upon it by
means of a gas-bottle, or a flexible tube,
leading from a gasometer.  A red suboxide
is formed which readily takes fire in the
open air.
The red crust which forms upon the surface
of pieces of phosphorus exposed to the action
of light, is believed to be a peculiar isomeric, or
Combustion of Phos- allotropic (173) condition of this substance.  It
Water.               may be obtained by keeping a quantity of phosphorus for several hours, at a temperature of
4500 to 4800~, in a gas which does not act upon it, as nitrogen or
hydrogen.
This red or amorphous phosphorus differs essentially from ordinary
phosphorus. Its melting point is about 4820, and it is non-luminous in the
air at ordinary temperatures.  Heated to 5000, it changes to ordinary
phosphorus.
QUESTIONS. —-Io     is phosphorus affected in the open air?  How is it
usually preserved?  May it be distilled?  What is said of its combustion in oxygen gas? How may it be made to burn under water?




COMPOUNDS OF PHOSPHORUS AND OXYGEN.                 245
277. Uses.-Phosphorus is now used in large quantities in the
manufacture of friction-matches, which ignite by slight friction.
For this purpose it is made into a paste, with gum or glue, by
which it is made to adhere to small pieces of wood or paper previously dipped in melted sulphur, and is also protected from the
action of the air.
The paste is sometimes mixed with nitrate or chlorate of lpotash,
or oxide or nitrate of lead, but this is not necessary.  Occasionally,
fine emory or powdered glass is mixed in the paste, to increase the
firiction.
Phosphorus is of great service in the laboratory, and has been
sometimes used in medicine.
Compouncds of Phosphorus and O~xygen.
278. There are four compounds of phosphorus and oxygen, the
atomic constitution of which appears to be P2,,PO,PO, and PO,.
The last three are acids; but only one of these, the last, will be
specially described.
279. Dinoxide of Phosphorus-P,. —This compound is prepared by the
combustion of phosphorus under hot water, as in paragraph 276. Atmosipheric air may be substituted for the oxygen.  The oxide appears as
flocculi of a brick-red color.  It absorbs oxygen friom the air, and mixed
with phosphorus it renders it more combustible.
280. Hypophosphorous Acid-o P0.-May be obtained as a syrupy
liquic, but cannot be crystalized. It cannot be obtained separate from
water.
281. Phosphorous Acid —PO. - Phosphorous acid may be prepared by the action
of the air upon sticks of phosphorus, at
ordinary temperatures.  For this purpose,       I11
place a few sticks of phosphorus in a funnel
under a bell-glass, as represented in the
figure, The glass is supported a little above          i     _, c
the table, to allow the air to enter. Regnault advises to put the sticks of phosphorus   a;=in small glass tubes, having capillary aper~  -  -
tures for the acid to pass through as it is    Preparation of P0s.
QUESTIONS.-277. What use is made of phosphorus? How are frictionmatches made?  278. What compounds of phosphorus and oxygen are
there?  279. How may dinoxide of phosphorus be prepared? 281. How
may phosphorous acid be prepared?
2 1




24-6     COMPOUNDS OF PHOSPHORUS AND OXYGEN.
formed, but they are not essential. Too large quantities of phosphorus
should not be used at once.
282. Phosphoric Acid —PO5; eq., (32 + 40 -) 72. — This
acid is formed by burning phosphorus in air or in oxygen gas, as
in the experiment given above (276).  To prepare it perfectly
anhydrous, the receiver should be placed over mercury, and the
oxygen or air supplied should be perfectly dry.  The acid appears
as a dense white vapor, which is gradually precipitated, and may
be collected.  In the open air it at once absorbs moisture.  If the
white flakes are collected and ignited, the mass, after cooling, is
semi-transparent, and is called glacial ph/osphoric acid.  This
acid may also be formed from calcined bones.
To prepare the common acid, a very good mode is to digest
phosphorus in nitric acid, with the aid of heat.  One part of
phosphorus, with  13
parts of the acid, of
specific gravity 1'20, is
placed in a glass retort
which connects with a
receiver that is kept
cold by a stream of cold
~j~l ~water, as shown in the
~_2<  ~ ~~        figure, and heat applied.
Red fumes of nitrous
Preparation of P05.
acid are given off, and
the phosphorus rapidly consumed. The liquid collected in the
receiver is now to be poured back into the retort, and heated
until the water and any remaining nitric acid are expelled.  On
cooling it will become solid, and present the same appearance as
glacial phosphoric acid just described. The acid thus obtained
contains 1 eq. of water for each eq. of the acid, and is called monohydrated acid.
The anhydrous phosphoric acid has a very strong affinity for
water, and when thrown into-it, unites with it with great energy,
often producing slight explosions, in consequence of the heat proQuEsTIOims.-282. What is the composition of phosphoric acid? How
is it prepared? How by the use of nitric acid? What is said of its
compounds with water?




COMPOUNDS OF PHOSPHORUS AND HYDROGEN.    247
duced.  With water it forms three different compounds, as follows, the first two of which have been called, respectively, meta.
phosphoric, and pyrophosphoric acids.
Monohydrated, or metaphosphoric acid, PO5,HO.
Bihydrated, or pyrophosphoric acid,    P052,21HO
Trihydrated, or common phosphoric acid, P05,3110.
These three acids, or rather compounds of acid and water, cannot be distinguished from each other by external appearance, but
dissolved in water they manifest chemical characteristics which
render them  quite distinct; they also form  salts, which, though
much alike in their general properties, are nevertheless easily dis
tinguished from each other by the proper tests.
Comlpounzds of Phlosphorus and ILdi'rogen.
There are several compounds of phosphorus and hydrogen, but
one only will claim attention from us, the common phosphuretted
hydrogen, PH,.  The others are P,H, and PHI2.
283. Phosphide of Hydrogen —PH,; eq., (32 + 3 =) 35.This gaseous substance, called also pho.sphurcttet 7edcdroyen, is
best prepared by heating some sticks of phosphorus in a strong
solution of caustic potash, in a small glass            --
retort, which, at the
beginning of the operation, should  be quite
filled with  the  materials.   If, then, the
mouth of the retort is                    _
made to dip slightly in       I 
*a bas dinpo waigter, ea  PiHs spontaneously combustible.
a basin of water, each
bubble -of the gas, as it breaks into the air, will burst into a flame,
QUESTIONS.-283. What phosphide of hydrogen is mentioned? HIow
is it prepared?




248     COMPOUNDS OF PHOSPHORUS AND HIYDROGEN.
with the formation of beautiful wreaths of smoke of phosphoric
acid, as shown in the figure.
In the presence of potash phosphorus has the property of
decomposing water, especially if the temperature be raised; the
oxygen and the hydrogen both combining with separate portions
of the phosphorus, producing the teroxide of phosphorus (phosphorous acid) and the terphosphide of hydrogen. Thus,
2P + 3HE0+ KO = KOPO, + PH3.
Instead of potash, milk of lime may be used with the same
result.
Still another method of procuring it is to decompose phosphide
of calcium  by water, or dilute hydrochloric acid; but when this
acid is used, the gas which is given off is not spontaneously inflammable.  It seems to be very well
determined that the spontaneous combustion of
this gas, in certain cases, is owing to the presence
of the vapor of another phosphide of hydrogen containing proportionably  more phosphorus, which
may be separated by passing the gas through a
PH13 spoutane- tube surrounded by a freezing mixture.
ously combusti-    Other combustible gases, as hydrogen, are made
ble.
to inflame spontaneously by receiving a portion of
the vapor of this inflammable phosphide.
To prepare phosphide of calcium, select a tube of green glass, half an
inch in diameter and a foot long; seal one end hermetically, and bend
it a little, as represented in the figure.
D —L-~-  ~.... In the sealed end put some  pieces
of phosphorus, and then, holding the
straight part in a horizontal position,
introduce some lumps of well burned
Preparation of Phosphide of Calcium. lime. The part containing the lime is
next to be heated to redness by means of burning charcoal, when heat is
also to be applied to the phosphorus sufficient to volatilize it; and the
vapor coming in contact with the heated lime, at once unites with it to
form the phosphide of calcium.  This should be preserved in bottles
with close stoppers; but even then it gradually undergoes decomposition.
Terphosphide of hydrogen is a colorless gas, with a very disagreeable
QuESTIONS.-Describe some of the properties of phosphide of hydrogen,
To what is its spontaneous combustion owing?




OTHER COMPOUNDS OF PHOSPHORUS.                          249
odor,* and is irrespirable; 100 cubic inches of it weigh 36.75 grains,
giving it a specific gravity of 1-18.
1 vol. of phosphorus vapor weighs  4-326
6 vols. of hydrogen weigh (.069 X 6).414
Forming 4 vols. of the terphosphide, 4.740
One volume therefore weighs. or the density of the gas is, 1.185
Other Compounds of Phzosphorus.
Phosphide of Nitrogen, N2P, is a white solid, which is infusible even
at a red heat.
284. Chlorides of Phosphorus.-There are two chlorides of phosphorus,
PC13, and PCI5, corresponding in composition to phosphorous and phosphoric acids.
The Terchloride of Phosphorus is formed in the same manner, and by
using the same apparatus, as chloride of sulphur (266). The chlorine
Preparation of PC13.
is formed in the flask A, and after being washed in water and dried in
the chlorine of calcium tube, is brought in contact with the vapor of phos* Those who have observed the odor of this gas, and that of the liquid emitted by the
American skunk (Mlephitis Americana) when disturbed, cannot but have noticed the
resemblance between them; which seems to render it probable that the fluid emitted by
the skunk contains, in solution, a portion of the gas, or some other nearly-related. compounds of the same substances. This is rendered still more probable from the fact, that
the fluid, when emitted by the animal in the dark, is distinctly phosphorescent.-See
Godman's _Natzural History, vol. 1. 289: Philadelhia eEdition, 1829.
QUESTION.-284. What chlorides of phosphorus are mentioned?




250                        ARSENIC.
phorus in the retort, D, where the chloride is formed, and afterwards con,
densed in the receiver E, which is kept cool by a stream of cold water
It is a colorless liquid, of a density of 1-45, which boils at about 1720.
285. Perchloride of Phosphorus is formed by saturating the preceding
with chlorine.  It is a solid, having its point of fusion, and also its boiling point, at about 2980.
Bromine and sulphur combine readily with phosphorus,
but the compounds are not important.
Iodide of Phosphorus is formed by bringing the two substances together in a vessel where as little air may have
admission as possible.  It forms a dark-colored mass.
(, e     These two substances afford one of the few instances in
which reaction takes place between two solids.  Let a
few crystals of iodine be dropped into a wine-glass, upon
a small piece of phosphorus, and immediately place over
it a bell-glass.  By the he.t produced, the phosphorus
will be inflamed and a portion of the iodine sublimed;
Prep. of Iodide and the white cloud of phosphoric acid (152), mingling
of Phosphorus,  with the dense iodine vapor, presents to the eye a very
pleasing appearance.
ARSENIC.
Synmbol, As; Equitvalent, 75; Densify, 5'88.
286. History and Preparation.-Arsenic has very generally
been classed with the metals, chiefly on account of its metallic
lustre, and  comparatively  high  specific gravity;  but, in  its
chemical properties, it is much more closely allied to the metalloids, with which it is here classed.
Arsenic sometimes occurs native, but usually it is found in corn.
bination with the metals, and especially with iron and cobalt.
The substance itself, or some of its compounds, seems to have
been known from the earliest times.
It may readily be prepared by heating the mineral called mispickel, which is a natural compound of arsenic, sulphur and iron,
in close vessels, by which the arsenic is expelled and the sulphide
QUESTIONS.-285. How is iodide of phosphorus prepared? Wbhat is
said of the action of iodine and phosphorus upon each other? 286. Why
bas arsenic often been classed with the metals?  Why is it here classed
-with the metalloids?  With what is it usually found combined?




COMPOUNDS OF ARSENIC  AND OXYGEN.                251.
of iron remains.  By again heating it with black-flux, the arsenic
is obtained nearly pure.  If the pulverized mineral is well mixed
with black-flux at the beginning, and no air admitted into the
apparatus, a single operation will afford it in great purity.
Let a common Hessian crucible be half filled with
the mixture, and then place another crucible, a size /
smaller, in an inverted position above it, as shown in
the figure, carefully luting them at their junction. A. ~;
moderate heat should then be applied to the lower "
crucible and very gradually raised.  The arsenic will
be sublimed from the mixture and condensed in small
crystals in the inverted crucible, which should have a 
very small aperture in the bottom, to allow the air to  of Arsenio.
escape as the heat is raised.
287. Properties.-Arsenic is a brittle substance, of a dark
color, and feeble metallic lustre.  Heated to about 3560, it is
sublimed, without first melting, as is the case with most solids.
Its vapor has a strong garlic odor, by which its presence may be
recognised, and a density of 10'37.  Heated in the open air, it
readily takes fire and burns with a livid flame.
Arsenic is often sold under the very improper names of cobalt
and fily-powder.
Compounds of Arsenic and Oxygen.
288. Two compounds only of arsenic and oxygen are known,
both of which are acids, and in composition correspond to phosphorous and phosphoric acids.
289. Arsenious Acid —AsO,; eq., (75 + 3 x 8 -) 99. —This
compound is the arsenic, or rats' bane, of commerce, well known
as a destructive poison. It is always produced when arsenic or
its ores are heated in the open air.  It is usually sold in a state
QUESTIONS.-How may arsenic be separated from  its compounds?
287. Describe arsenic.  What is said of its odor?  288. What compounds of arsenic and oxygen are known?  289. By what names is
arsenious acid often known.




252        COMPOUNDS OF ARSENIC AND HYDROGEN.
of fine white powder; but when first sublimed, it is in the form
of brittle masses, more or less transparent, colorless, of a vitreous
lustre, and conchoidal fracture. This glass, which may also be
obtained by fusion, gradually becomes opaque without undergoing
any apparent change of constitution, but becomes more soluble in
water than before.  Its specific gravity is 3'7.  At 3800 it is
volatilized, yielding vapors which do not possess the odor of
garlic, and which condense unchanged on cold surfaces. If thrown
on burning charcoal, the garlic odor is perceived, because of
the reduction of the oxide by the carbon.
Destructive as this substance is to the animal system, in minute doses
it is sometimes used in medical practice; and in some countries, as in
parts of Austria and Hungary, it is habitually used much in the same
manner as narcotics, and even administered to horses. The effect is
said to be to give a roundness and fulness of form, and clearness and
freshness to the complexion. Horses accustomed to receive it in their
food, have a fat and plump appearance, and bright and glossy skins. It
also improves their breathing.
This substance is so frequently used to destroy life, that its detection.n suspicious cases becomes an important object; but we reserve our
remarks on this point until some others of the many compounds of arsenic
have been described
290. Arsenic Acid-As05; eq., (75 + 8 X 5 =) 115. —This acid may
be formed by dissolving arsenious acid, just described, in nitric acid
mixed with a little of the hydrochloric, and evaporating to dryness. It
is a powerful acid, much resembling phosphoric acid (247); with
which it is isomorphous. Its salts are also isomorphous with the salts
of phosphoric acid.
Compounds of Arsenic and IIy/drogen.
291. Two compounds of these elements are known, one of which is
solid, and the other gaseous. Of the former, little is known, with certainty, and we therefore do not further allude to it.
292. Arsenido of Hydrogen, Arseniuretted Hydrogen —AsHs; eq.,
(75 + 3 =) 78.-This gas is evolved when arsenide of tin or zinc is
treated with strong hydrochloric acid, or when sulphuric or hydrochloric
acid is made to act upon zinc or iron in the presence of any soluble compound of arsenic.
To prepaire it, pour upon some pieces of zinc diluted sulphuric acid
with a few drops of solution of arsenious acid; the gas, which burns with
a feeble blue flame, will be at once'rapidly evolved.
QUESTIONS.-Describe arsenious -acid.  For what purpose is it often
used?  290. To what other acid ii arsenic acid analogous?  292. How
is arsenide of hydrogen prepared. ~::




COMPOUNDS OF ARSENIC WITH SULPHUR, ETC.    253
When thus prepared, the reactions are as indicated in the following
formula, the zinc being oxydized at the expense of the oxygen both of the
water and the arsenious acid. Thus,
6Zn + 3O -+ -AsO3 + 6SO3 = 6 (ZnO,S03) + AsIt3.
The gas has a peculiar nauseating odor, and is exceedingly poisonous
Its density is 2-69, and by a cold of -220 it is converted into a liquid
under the ordinary atmospheric pressure.  By chlorine it is instantly
decomposed, chloride of arsenic and hydrochloric acid being formed.
By solution of blue vitriol it is rapidly absorbed, and arsenide of copper
precipitated.
The equivalent of this gas, AsH3, answers to 4 vols., which is thus
constituted:
1 vol. of arsenic vapor weighs 10.370
6   "   hydrogen        "     414
4 vols. arsenide of hydrogen, 10'784
Weight of one vol., or the calculated density of the gas, 2'696.
We shall have occasion to speak of this compound again in connection
with the detection of arsenic.
Compounds of Arsenic with Sdp1huZ r and Other Elements.
293. Sulphides of Arsenic.-The bisulphide of arsenic, AS2, is found
native, and called realgar by mineralogists. It may also be formed by
art. It is of a dull red color.  The tersulphide, AsS,, is the opimnent,
or king's yellow of commerce. It is formed artificially by passing a current of hydrosulphuric acid through an arsenic solution containing a
little free acid. It is also found as a natural production, and is of a
bright yellow color, and is sometimes called sulpharsenious acid. A third
compound of these elements, the pentasulphide of arsenic, AsS,, called
also sulpharsenic acid, is formed by mixing solutions of hydrosulphuric
and arsenic acids. It forms slowly, and some days are often required
before the whole is precipitated.
The compounds of arsenic with chlorine, iodine, phosphorus, &c., will
be found described in larger works.
QuESTIONs.-Describe the reactions which take place in the preparation of arsenide of hydrogen. What are some of the properties of this
gas?  293. What is realgar.   What is orpiment 
22




254             DETECTION  OF ARSENIC.
Detection of Arsenic.
294. Poisoning by arsenious acid is at the present day, unfortunately, very common; and it therefore becomes a matter of
special importance to be able with certainty to detect the instrument of death.
295. There are as many as ten or twelve different tesbs for
arsenic, but we shall confine our remarks to some of the
most important. A single test should never be relied on, but
several different ones should always be applied to separate portions of the suspected substance.
I. Marsh's Test.-Put into a two or four ounce vial some pieces of
clean zinc, and pour on them a small quantity of dilute oil of vitriol
(oil of vitriol 1 part, and water 8 parts), and insert a cork
with a small tube, as shown in the figure.  Very soon
hydrogen gas will begin to be evolved, as in the preparation of hydrogen. After a little time the jet of hydrogen
_cgI\)    may be inflamed; and if all the materials used were pule,
a piece of glass or porcelain held in the flame will receive
no stain, but only a deposition of moisture from the comi   - 1ll   bustion of the hydrogen.
The cork and tube being now removed, introduce soime
of the suspected substance, or water in which the suspected
substance has been digested, with the aid of heat if necesMarsh's Test. sary, and immediately replace the cork and tube.  In a
little time the jet of gas may be relighted; and if any appreciable quantity of arsenious acid is present, a piece of clean glass or
porcelain held in the flame will at once receive a black stain upon its
surface, caused by a deposition of arsenic.
If the quantity of arsenious acid present is large, the flame will be
of a pale color, and the blackening of the glass held in the flame will be
instantaneous; but if the quantity be small, the blackening effect will be
produced only after a little time.
The deposition of arsenic here is from  the arsenide of hydrogen,
which is formed in the manner heretofore (292) explained.'i'he cold
substance held in the flame causes the deposition of the arsenic while
the hydrogen is consumed.
This is perhaps the most delicate test of arsenic known, but in using it
some precautions must always be observed to avoid mistake.  In sole
cases, where organic substances are present, spots similar to those produced by arsenic may be formed, that may be mistaken for arsenic by
QUESTIONS. —295. What is said of the number of tests for arsenic?
Describe Micarsh's test. From what is the arsenic deposited?  What is
said of the delicacy of this test?




DETECTION OF ARSENIC.                           255
the inexperienced; and antimony will form spots very much like those
of arsenic. Means must therefore be adopted to test the material forming the dark spot upon the porcelain.  For this purpose, it will generally
be sufficient to hold the spot a few minutes in the flame of a spirit-lamp;
if the deposite be arsenic it will be volatilized, and disappear, but if produced by antimony or other substances, it will remain. So also arsenic
spots, exposed a few minutes, at a moderately elevated temperature, to
vapor of iodine, become yellow, and then subsequently disappear by
exposure to the air.
II. Reinch's Test.-In a portion of the suspected liquid, made acid by
hydrochloric acid, place a piece of metallic copper, previously filed perfectly bright, and heat the whole nearly to the boiling point. If any
appreciable quantity of arsenious acid be present, the arsenic will be
deposited upon it as a gray crust of a metallic lustre.
III. Test by Hydrosulphuric Acid.-Through a portion of the suspected substance, supposed to be in the liquid form, acidulated with
muriatic acid, pass a current of hydrosulphluric acid gas for half an hour, and then
boil it a few moments; if arsenic be present, a yellow  precipitate-orpiment (293)
-will be formed.  The mode of passing the
current of gas through the liquid will be
seen  by the accompanying  figure.  The
materials for producing the gas are put into            
a flask, and a tube, bent twice at right
angles, is inserted through a cork, so as to
be air-tight; the other end is then immersed
in the liquid, contained in a glass vessel, so   Test by Ilydrosulphuric Acid.
as to reach near the bottom, and the gas, as
it escapes, bubbles through the liquid.  The mode is the same as before
described (263).  The precipitate (orpiment) thus formed, is entirely
soluble in aqua ammonise, and in solutions of the alkalies.
IV. Test by Ammonia-Nitrate of Silver.-Nitrate of silver forms with
arsenious acid solutions a precipitate of arsenide of silver, which is
of a peculiar canary yellow color, and is soluble in nitric acid. To
ensure the formation of this precipitate, the arsenious solution should
be slightly alkaline, and therefore the ammonia-nitrate of silver is used
in preference to the simple nitrate. This is prepared by pouring into
the nitrate of silver solution aqua ammonia, until the precipitate at first
thrown down is nearly all dissolved.
A precipitate very similar in its appearance to the above would be
produced by phosphoric acid in the suspected liquid; so that the precipitate formed by use of this test should always be further examined,
before any reliance is placed upon it.
V. Test by Ammonia-Sulphate of Copper.-Solution of sulphate of copper produces in neutral or alkaline solutions of arsenious compounds a
beautiful green precipitate, sometimes called Scheele's green. In making
QuEsTIoNs.-Describe Reinch's test.  Describe the test with hydrosulphuric acid. Describe the test with ammonia-nitrate of silver. Describe
the mode of testing with ammoniae-sulphate of copper.  What will be the
color of the precipitate?




256             DETECTION OF ARSENIC.
the experiment, it is best to use the ammonia-sulphate of copper, which
is prepared by pouring into a solution of blue vitriol, aqua ammonim,
until the precipitate at first formed is nearly all redissolved, as in the
corresponding preparation of ammonia-hitrate of silver.
But this test also may form with other substances a precipitate similar
in appearance to the above, so that further examination should always
be made.
VI. Flandin and Danger's Test.-Dry the suspected substance (supposed to be organic, as sugar or starch,) and treat it with one-fourth of
its weight of the strongest oil of vitriol, and apply heat until it is quite
dry;-the whole will now be reduced to a black, friable mass, which can
easily be pulverized, and is then to be boiled with strong nitric mixed
with a little hydrochloric acid. By this process the arsenic, in whatever
form it may be, is converted into arsenic acid, which after the whole has
been again'evaporated to dryness, to expel any remaining nitric acid,
and redissolved in pure water, may be examined by the appropriate tests,
not for arsenious but for arsenic acid.
For this latter purpose, the ammonia-nitrate of silver may be used,
which gives with arsenic acid a brick-red precipitate.
Or, the arsenic acid being obtained in solution, may be precipitated as
arseniate of lime by lime-water, and from this precipitate pure arsenic
with its metallic lustre may be obtained by the process next to be
described.
VII. Reduction of the Arsenic. —When arsenic is present in any appreciable quantity, it may always be obtained in a separate state, so as to
be recognised by its peculiar metallic lustre and garlic odor; and no
chemist in any particular case will positively swear to its presence unless
he is able thus to procure it!
For this purpose, provide a tube of hard glass, a quarter of an inch in
diameter and three or four inches long, with one end hermetically
sealed; and fill it to the depth of half an inch with a mixture of the
suspected substance, charcoal, and carbonate of soda, the whole being
previously well dried at a moderate heat, and ground together to a fine
powder. After wiping the inside of the tube with a little cotton attached
to a wire,' to remove any dust or remaining
moisture, a strong heat is applied to the end
of the tube containing the mixture, by which the
arsenic will be separated, to be again condensed
upon the sides of the tube a little above the
heated part.  The bright metallic lustre will at
once be recognised, and by breaking the tube
and heating the part coated, as in the figure, the
_____~i~-~   peculiar garlic odor will be perceived.  Other
Test of Arsenic.  tests may also be applied to it if desired.
This last test may be applied to any of the precipitates obtained by
the previous tests.
QuESTINs. —Describe Flandinz and Danger's test. Describe the mode
of testing by reduction of the arsenic. Hfow does the arsenic show
itself?  May the last mode be applied to the precipitates obtained by
the other modes?




CARBON.                            257
296. In these directions we are supposed, as a general thing, to be
operating with pure arsenical solutions, but in cases of actual poisoning
it will usually be otherwise; and it often becomes an important object to
be able to separate the organic matter cofitained in the suspected sub —
stance. Sometimes the substance will be soluble, as sugar, which will
not interfere badly with the operation; and at others it will be of such a
character that it can be removed by passing through it a current of
chlorine, or it may be that it can be removed only by heating it with
strong oil of vitriol, as heretofore (VI.) described. In any particular
ease, the mode of proceeding to be pursued must be adapted to its
peculiar circumstances.
GROUP V.
CARBON ~  Combustible bodies, and incapable of being volatilized even
SBIcoN (at the highest temperatures.
BORON
CARBON.
Symnbol, C; Eqivalent, 6; Deotsity (crystalized), 3 52.
297. History.-Carbon, though rarely met with in nature perfectly pure and uncombined, is one of the most important of the
elements, forming, as it does, an essential ingredient of nearly all
vegetable and animal bodies.  It is found in a variety of forms;
and when uncry-talized and  uncombined, its color is always
black.
298. Preparation and Properties.-Carbon presents itself to
us in a variety of forms, as the diamondc  graphite or pltnmbago,
mnineral coal, charcoal, gas coal, and perhaps we may add lampblack, though the latter very probably differs from charcoal only
in being in a state of fine division.
QUESTIONS.-296. In these directions what are we supposed to operate
with? Will this usually be the case in practice? Will it often be necessary to separate organic matters from the suspected substance? What
elements constitute the fifth group?  HIow are they characterized?
297. Give the history of carbon. 298. What are some of the varieties
of carbon?
22*




258                       c  It A B O N.
The diamond is pure crystalized carbon, and is the hardest
substance known in nature.  The crystals are of the form of the
regular octahedron, but the faces are frequently a
little convex, as shown in the figure.  Such crys(- - -.-  tals, properly set, are used for cutting glass, a purpose for which they are admirably adapted.  Heated
intensely in the flame of the compound blowpipe,
Diamond.   the diamond is entirely consumed, forming carbonic
acid, just as if the same weight of pure charcoal had been consumed.   Diamonds are generally very small, the largest ever
found weighing less than six ounces.   A single diamond has
been sold for more than half a million of dollars. It is generally
found in the same situations as gold and platinum.  A few crystals of little value have been discovered in the vicinity of the
gold mines in some of the Southern States. It is a powerful
refractor of light, and seems to have the faculty of absorbing light,
and giving it out again after a time. A diamond held in the
sun's rays a few seconds, and then removed at once to a dark
room, phosphoresces very distinctly for a few seconds.
Graphite, or plumbago, called also, very improperly, black
lead, is a variety of carbon, containing usually a little iron.  It
is often found crystalized in thin scales, of a hexagonal form.  It
is not unfrequently formed as an artificial production in iron furnaces, and is sometimes quite free from iron.
It is used for the manufacture of pencils, and in the construction of crucibles that are to be exposed to a very intense
heat. For this purpose, it is ground to a fine powder, and mixed
thoroughly with fire-clay.  These crucibles are used chiefly for
melting metals.
Mineral coal is of two kinds; the bituminous, and the nonbituminous, or anlthracite,
Bituminous coal is distinguished by its softening like wax,
when heated, and giving off much gas, which burns with flame.
QUESTIONS.-What is the diamond?  What is said of its hardness?
What use is made of it? What is the effect of the intense heat of the
compound blowpipe upon it? What is said of the size of diamonds?
What is said of the absorption of light by the diamond? What is
graphite or plumbcgo? What use is made of it?  What two kinds of
mineral coal are there?  How is bituminous coal distinguished?




CARBON.                           259
It is also much lighter than anthracite, and more easily ignited.
Some of the different varieties of bituminous coal are caking,
sp2lint, cherry, and cannel coal.  Jet, also, which is used in
jewelry, is a bituminous coal; and in the same family may be
included wood or Bovey coal, sometimes called lignite.
Anthracite, or stone-coal, differs from  the above varieties, in
containing no bituminous matter; and, therefore, it yields no
inflammable gas by heat.  Its sole combustible ingredient is
carbon; and, consequently, it burns without flame.  It is found
in different countries, but nowhere in such profuse abundance as
in the eastern part of the State of Pennsylvania, which supplies
most of the northern and eastern parts of the United States
with fuel.
All the varieties of mineral coal are believed to have been
formed from vegetable substances, which, in the changes the
earth's surface has undergone, have become buried beneath it.
When bituminous coal is subjected to a high temperature in
close vessels, or with only a limited supply of atmospheric air,
the volatile or bituminous manner is expelled, and the remaining
porous carbon is called coke.  It is used for many important
purposes in the arts.
Charcoal is prepared by exposing vegetable matter, and especially wood, to a high temperature in close vessels, or in such
circumstances as to avoid the presence of atmospheric air.  By
the heat a large quantity of water, acetic acid, tar, and other
matters, is expelled, and the carbon, with any mineral matter
which has been absorbed from the soil, remains.  The latter constitutes the ashes which remain after the combustion of the coal
in the open air.
The usual method of preparing charcoal for ordinary purposes,
is to ignite large heaps of wood, which are covered with earth so
as to admit only a limited supply of atmospheric air; and the
result is to char or convert into coal a large part of the wood, by
the heat occasioned by the combustion of the other part.
QuESTIoNs.-What is said of anthracite or stone-coal? -Where is it
found in this country?  What is coce?  HIow is charcoal prepared?
What constitutes the ashes?




260                        CARBON.
The figure, diminished from Knapp's Technology, represents a
section of a coal-pit ready to be ignited. The stake at the centre
Preparation of Charcoal.
serves as a support for beginning the heap; and by one side of
which space is left to kindle the fire, by dropping in pieces of very
dry wood and burning coals.
Charcoal is a black, hard, brittle substance, perfectly insoluble
in every liquid, but attacked and oxidized by strong nitric acid.
It is a good conductor of electricity, but a non-conductor of heat;
is little acted upon by air and moisture, and is perfectly infusible
in the most intense heat that can be applied to it.  Heated in
the open air, it takes fire and burns freely, especially if in large
masses, leaving only a small residue of ashes.
299. Charcoal possesses the property of absorbing a large
quantity of air, or other gases, at common temperatures, and
of yielding the greater part of them again when it is heated.
Recently-burned charcoal absorbs air and moisture so rapidly, for
a few days, as materially to increase its weight. Both are absorbed
and retained with such force, that a red heat is required to expel
them. This absorption of air may be readily shown in the following manner:-Let a piece of charcoal, of moderate size, be
heated to redness for a few minutes, and then quenched under
QUzESTIONS.-Describe charcoal. 299. What is said of the absorption
of gases by charcoal? How may the absorption of air be shown?




CARBON.                          261
mercury, and placed under a receiver, over the
mercurial cistern.  The mercury will shortly begin
to rise, in consequence of the absorption of the air
within; and the process will continue for several
hours.
Charcoal, likewise, absorbs the odoriferous and _-i
coloring particles of most animal and vegetable --
substances.  When colored infulsions of this kind  Charcoal absorbs
Gases.
are digested with a proper quantity of charcoal, a
solution is obtained which is nearly, if not quite, colorless.
Tainted flesh may be deprived of its odor by this means, and
foul water be purified by filtration through charcoal.  The substance commonly employed to decolorize fluids is animal charcoal
reduced to a fine powder.  It loses the property of absorbing
coloring matters by use, but partially recovers it by being heated
to redness.
At very high temperatures charcoal has a higher affinity for
oxygen than any other substance, and is therefore often heated
with oxides of the metals to deoxidize them, or deprive them of
their oxygen.
Lampblack is minutely divided carbon, prepared by burning
rosin or tar in a confined portion of air, so that the hydrogen
only of the material is consumed, and the carbon remains as an
exceedingly fine powder. It is used as a pigment, and for other
purposes.
Gas coal is a deposite of nearly pure carbon upon the inside
of the large retorts used in the manufacture of illuminating gas.
It is very hard and black, and a good conductor of electricity.
Uses. —Carbon is used as fuel; in forming gunpowder; as a
pigment; in the formation of steel; as a polishing-powder; and
in medicine as an antiseptic, &c., &c.
QUEsTIoNs. —What is said of the affinity of charcoal for oxygen at high
temperatures? What is lampblack? What use is made of it? What is
gas coal?




262         COMPOUNDS OF CARBON AND OXYGEN.
Compounds of Carbon and Oxyygen.
300. Carbon combines with oxygen in two proportions, forming carbonic oxide, CO, and carbonic acid, CO2.
301. Carbonic Oxide, Protoxide of Carbon-CO; eq., (6 + 8 =) 14.This is a. gaseous substance, and is best prepared by heating a mixture
of equal parts of dry powdered chalk and iron-filings in a gun-barrel.
The chalk, which is carbonate of lime, when heated, gives off its carbonic
acid (the compound next to be described) in contact with the heated iron,
by which one-half of its oxygen is instantly absorbed, and the carbonic
oxide thus produced passes on, and may be collected over water. Thus,
CaO,CO2 + Fe = CaO + FeO + CO.
Another method of preparing it, is to heat gently a mixture of oxalic
acid and five or six times its weight of oil of vitriol, by which both carbonic oxide and carbonic acid are produced in equal volumes; but the
_ rearaio ofill,
Preparation of CO.
latter may readily be separated by passing it through a solution of caustic
potash or milk of lime, in the three-necked bottle, and collected over
water. The changes which take place are as follows, viz:C203,3HO + SO3,IIO    S03,4HO + CO2 + CO.
The density of the gas is about 0.97; 100 cubic inches weighing 80-20
grains. It is highly combustible, and burns with a beautiful blue flame.
QuESTIONS.-300.-What compounds of carbon and oxygen are there?
301. Describe the mode first mentioned for preparing carbonic oxide.
The second mode. Is carbonic oxide combustible?  What is the color
of the flame?




COMIOUNDS OF CARBON AND OXYGEN.                 263
it will not support respiration or combustion; and
a lighted candle being inmmersecl in it, as heretofore
described in connection with hydrogen (198), is instntly extinguished.
It is this gas which gives the blue flame seen
about the fire of the blacksmith, and in anthracite
stoves, when the door is suddenly opened soon after
the fire has been kindled, and in furnaces for the
reduction of the metals from their ores.
Carbonic oxide is believed to be composed of 1 vol.
of carbon vapor and 1 vol. of oxygen combined with- 
out condensation. Thus,             a
1 vol. of carbon vapor weighs.836 
1 vol. of oxygen       "   14106;
2 vols. of carbonic oxide  "   1-942
1 vol. of the oxide therefore"' 971       CO is Combustible.
302. Carbonic Acid-CO,; eq., (6 + 16 =) 22.-  Carbonic
acid is remarkable as being the first gaseous substance recognised,
after atmospheric air, which must always have been known. It
was first described by Dr. Black, in 1757, and called, by him,
fixed air, because he found it fixet in
common limestone and magnesia; from
which it may be expelled by heat, or 
by the action of any strong acid.  It
may be collected over water, but a portion will be absorbed.  A  gas-bottle,
of the form shown in the figure, is con-   llll
venient for preparing it.  Some  fragments of marble, and water, are placed
in the bottle, and the cover put on,         PreparationofCO0
and then strong hydrochloric acid is poured into the long-necked
funnel.
As thus prepared, carbonic acid is a colorless, inodorous gas,
of specific gravity 1.52; 100 cubic inches weighing 47'14 grains.
It is considered a compound of I vol. of carbon vapor and 2 vols. of
oxygen condensed to 2 vols. Thus,
QUESTIONS. —302. When was carbonic acid discovered? What was it
first called?  How may it be prepared?  What is its specific gravity?
What is it composed of?




264          COMPOUNDS OF CARBON AND OXYGEN.
I vol. of carbon vapor weighs.      836
2 vols. of oxygen     "   (1.106 X 2) 2-212
2 vols. of carbonic acid "           3-048
The weight of 1 vol. therefore is     1-524
Or we may consider it a compound of 2 vols. of carbonic oxide and 1
vol. of oxygen, condensed to 2 vols., as follows:
2 vols. of carbonic oxide weigh (.971 X 2) 1-942
1 vol. of oxygen         "              1-106
Giving for the weight of 2 vols. of C02,   83048
And for the weight of 1 vol., as before,  1-524
Carbonic acid is so much heavier than atmospheric air, that
it may be poured from one vessel to another without difficulty.
Let a bottle, with a wide mouth, be
/-        /   filled with the gas, and then plunge
__________ _______3       into it a piece of lighted paper, or
_______________-7   =other substance, so that some smoke
l  L-    may be mixed with it and render its
C02i~    pouedfrm   Val  motions visible. Then hold the bottle
in the hand, as if pouring a liquid from
it (as represented in the figure), and the motion of the gas, as it
is emptied from it, will be made apparent to the eye.
Another instructive experiment of the same character may be
performed as follows:  Provide
a glass jar with. a large mouth,
and place at the bottom a lighted
taper, as shown in the figure.'I'~                   Then having filled another jar
of about equal capacity  with
carbonic acid gas, carefully remove the cover and gradually
X ~   g......... pour the contents into the firstCandle Extinguished.      mentioned jar; —the  flame of
the taper will first be considerably disturbed by the motion occasioned by the descending gas, and will finally be extinguished.
QuEsTIoNs. —How may the high specific gravity of carbonic acid be
shown by pouring it from a vessel?  I-low may the flame of a candle be
extinguished by it?




COMPOUNDS OF CARBON AND 0OXYGEN                   26
By a pressure of 36 atmospheres, at 32~, it is converted into a
beautiful transparent liquid, which may be frozen by intense cold,
in the manner already explained.
303. It is capable of supporting neither combustion nor respiration;-a burning candle plunged into it is instantly extinguished;
and a living animal, thrown into a vessel containing it, even
though considerably diluted with air, soon dies, Carbonic acid
is always produced by ordinary combustion; and lives have often
leen lost by persons placing an open dish of burning charcoal in
their bed-rooms before retiring to rest.  The oxygen of the air in
the room is taken up by the carbon, and the gas in question takes
its place, producing the effects described.  It is produced, also,
by the decay of animal and vegetable
substances, and sometimes is found
collected in caves and wells, and is
called choke-danmp.                       E.i
Though this gas does not support combustion, as the experiment is ordinarily
made, yet potassium, sodium, and some
other of the metals may be macde to burn           j 
in it.  For this purpose, fill a flask with        x<,
dry carbonic acid gas, and drop into it a
small piece of potassium, and apply the
heat of a lamp at the point where the
metal lies, by means of a blowpipe. When
it has become very hot the metal takes fire   _____
and burns brilliantly, the carbon of the
carbonic acid decomposed being deposited
upon it as a black powder.               combustion of Potassium in C02.
304. Soclct-fountai is are formed by compressing a large quantity
of this gas in water, contained in a strong vessel adapted to the
purpose.  When the tube leading from  the fountain is opened,
the water is forced out by the pressure, and effervesces violently
by the escape of the gas.  Soda-powders, &ec., often used to produce an agreeable drink, in the absence of a soda-fountain, consist
of bicarbonate of soda and tartaric acid, which, when mingled
QUESTIONs.-May carbonic acid be compressed to the liquid form?
303. Is it always produced in ordinary combustion?  How may potassium be made to burn in it? What becomes of the carbon of the carbonic
acid? 304. How are soda-fountains formed?
23




266        COMPOUNDS OF CARBON AND HYDROGEN.
together in solution, produce, by chemical action, tartrate of soda,
the carbonic acid passing off into the air with effervescence.  So,
also, the effervescence which takes place on opening a bottle of
Wbeer, cidoer or champagne wine, is owing to the escape of this
gas, which has been produced by the fermentation of the liquidO
All kinds of spring and well-water contain it in small quantity,
and become ins'ipid to the taste by boiling, in consequence of the
gas having been expelled.  It is also always present in the atmosphere, and in some cases accumulates in considerable quantities,
as at the Grotto del Cane, in Italy, through which a man may
pass without danger, but a dog on entering it is instantly suffocated.  The carbonic acid here constantly issues from the earth,
and accumulates at the bottom, while the air above remains comparatively pure.
305. Lime-water is an excellent test for
carbonic acid; and a vessel of it being allowed to stand a few  hours, becomes coated
with a pellicle of carbonate of lime, by absorbing this gas from  the air.  So lime-water
becomes milky by blowing into it with a tube
from  the lungs, for the same reason.  A portion of the lime is changed into carbonate of
lime, which is insoluble and gives the water its
Lime-water.   milkiness.
Comnpounds of Carbon and Hy1drogen.
306. Carbon and hydrogen combine in a number of different
proportions, producing compounds, several of which are of special
interest, because of their isomeric character; but we shall here
describe only two, both of which are gaseous, viz., light carbutretted h]ydrogen, C2H4, and olefiant gas, C4H,.
QuEsTions.-What is said of the Grotto del Cane in Italy?  305. }T!ov
is lime-water affected by blowing through it with the mouth?  CGive
the reason for the milkiness producedl?  306. What is said of the con-alpounds of carbon and hydrogen?




COMPOUNDS OF CARBON AND HYDROGEN.                267
307. Light Carburetted Hydrogen —C2H4; eq., (12 -- 4 ==)
16.-This gas, called alsofire-damp, marsh gas, hydrocarburet, and
dicarburet of hydrogen, is formed
by the slow decomposition of wood,
and woody substances, under water,   I..
especially in warm weather; and - -
may be obtained  by stirring  the -
mud and other matters at the bot- 
tom  of stagnant pools (see figure),
and collecting the bubbles of gas in      Collecting Marsh Gas.
a receiver, as they rise.  It sometimes accumulates in large quantities in coal mines, where it is
formed by the action of water upon the coal.
It is best prepared by heating in a flask, made of hard glass, a
mixture of 2 parts of acetate of soda, 3 parts of caustic potash,
and 3 of quick-lime.  The composition of the acetic acid is
CH404, which, it will be perceived, is precisely equal to 2 eq.
of carbonic acid, and 1 of the hydrocarburet in question.  Thus,
{C4H404 - 2CO2 + C21H4.
The use of the lime is to protect the gas from the action of the
potash.
Light carburetted hydrogen is a colorless, transparent gas, 100
cubic inches of which weigh 17'37 grains, giving it a specific
gravity of 0'56.
One volume contains 2 vols. of hydrogen, x of a vol. of carbon vapor.
Thus,
2 vols. of hydrogen weigh (.069 X 2).138
4 vol. vapor of carbon (.836)   *418
1 vol. of the hydrocarburet,     *556
A burning candle is extinguished by it, but it is, itself, highly
combustible, and burns with a feeble, yellow flame.  Mixed with
twice its own volume of oxygen, or seven or eight times its volume
QUESToNS.-8307. In what situations is light carburetted hydrogen
naturally formed? How may it be collected? IHow may it be pi epared
L.,frificiaylly?




268        COMPOUNDS OF CARBON AND HYDROGEN.
of air, it explodes violently by the electric spark, or on the approach of flame.
808. Olefiant Gas, or heavy Carburetted Hydrogen-(J4H,;
eq., (24 + 4 -) 28. —This gas was first described in 1796, by
some Dutch chemists, who gave it the name, olefiant gas, because
of its forming with chlorine a peculiar oil-like liquid.  It is colorless and tasteless, and but slightly absorbed by water; 100 cubic
inches weigh 30'41 grains, so that its density is 0'98.
Its volume contains 2 vols. of hydrogen, and 1 vol. of vapor of carbon,
as follows:
2 vols. of hydrogen weigh (-069 X 2) -138
1 vol. of vapor of carbon,'      836
Giving for 1 vol. of olefiant gas,    *974
Olefiant gas is prepared by mixing, in a capacious retort, one
part of alcohol with four of concentrated sulphuric acid, and
heating the mixture, as soon as it is made, by means of a lamp
or ignited charcoal.  The acid soon acts upon the alcohol, effervescence ensues, and defiant gas passes over, mixed with other
substances, chiefly sulphurous acid, from which it may be purified
Preparation of Olefiant Gas.
by washing it with solution of lime or caustic potassa in several
of Woulf's bottles, as shown in the figure.
As might be expected, olefiant gas does not support combustion; but a jet of it burns in the air, or in oxygen gas, with a
QUESTroNS. —Does light carburetted hydrogen form explosive mixtures
with oxygen or atmospheric air?  308. By whom was olefiant gas discovered?  Why was it so called?  Describe it.  How is it prepared?
What is said of the light produced by its combustion?




COMPOUNDS OF CARBON AND HYDROGEN.                  269
brilliant white light.  Mixed with oxygen, or air, in proper proportions, it explodes violently, like the preceding compound.
309. Illuminating Gas is usually a mixture of olefiant and
light carburetted hydrogen gases, and is formed by distilling, in
large cast-iron retorts, rosin, tar, or other resinous or oily substances, or bituminous coal.  Besides the gases mentioned, there
are also formed other hydro-carbons, but in less quantity.  Illuminating gas is used in immense quantities in large cities, for lighting
the streets, and for fixed lights in stores and other buildings.
Illuminating gas is now chiefly prepared from bituminous coal,
and as it passes from the retorts is mixed with tar, carbonic acid,
eulphuretted hydrogen, salts of ammonia, and other matters, from
which it must be freed before being admitted to the burners.  For
this purpose, it is washed by passing it through water, and then
further purified by passing through, vats containing recentlyslaked lime.
If this gas is made to pass through a heated tube it is decomposed, and a part of its carbon is deposited as a coating upon the
inside of the tube.   In this way large deposits of pure carbon
are often formed in the retorts of gas-works.  It has been described above (299) as gas carbon.
310. The History of gas manufacture, for illuminating purposes, possesses much interest, as showing the great benefit conferred by science on
the arts, and domestic and public economy. In 1680, Mr. Clayton, of
Yorkshire, England, observed that a brilliant light was produced by
igniting the gas which issued from a close vessel containing bituminous
coal when heated, but it was a century after this before any direct
experiments were made with it, with reference to its use in the arts. In
1785, the preparation of gas for illumination, from the destructive distillation of wood, was suggested; but, in 1792, some buildings were actually
illuminated with gas, in Cornwall, England; and the same thing was
repeated in 1798, at a foundry in Birmingham.  In 1805, some of the
cotton-mills in MIanchester were first lighted with gas, by means of
permanent fixtures, prepared for the purpose; and this date may be
assumed as the beginning of the use of gas-lights for practical purposes.
In a half century, therefore, has this manufacture attained its present
importance; and the time is not distant when the quantity annually consumed in every civilized country will be greatly increased.
QUESTIONS.-309. What is illuminating gas?  How is it usually prepared?  What is the substance now generally used for producing its
310. What is said of the history of the use of illuminating gas for practical purposes?
23*




270       NATURE OF FLAME.-THE SAFETY LAMP.
Nrature of Fllaame.-T/e Safety Lamp.
311. What we term the combustion of a substance is occasioned
by its entering into combination with some other substance, usually
the oxygen of the atmosphere, and then taking another form as a
compound (193).  Of the two substances thus required to produce
combustion, one is called the combustible substance, and the othet
the sui2pporter of the combustion; but the action is really mutual
between them, and neither can burn without the other.  The
supporter of ordinary combustion, oxygen, is always gaseous, but
the combustible may be either solid, liquid, or gaseous.
Flame is gaseous matter in a state of combustion, and is made
incandescent by the intense heat of the combustion. Two gases
are needed to produce it, one of which must be combustible, and
the other, of course, a supporter of combustion.  The action is
mutual between them;-neither will burn alone;-and a jet of
either will burn in the other.
In the common lamp or candle, the combustible gases are supplied from the oil, or tallow, which is gradually raised, by the
capillary action of the wick, into the flame, where it is decomposed by the heat. As these gases, thus produced, escape from
the wick, and come in contact with the oxygen of the atmosphere,
the two combine, producing the phenomena of light and heat, with
which all are familiar.  A careful inspection of the flame of a
is composed of three parts, viz: —lst, a central part, a,
surrounding the wick, and extending a little above it,
c       of gaseous matter that has emerged from the wick, and
is making its way outward to the atmosphere, which it
rI/j1q Ohas not yet reached, and therefore has not yet become
j   8EIignited; 2d, the bright part of the flame, b b, which,
in the form of a conical shell, incloses the part a, and
1 ][I |consists of gaseous matter in a state of rapid combustion,
Caude,.  the combustible particles, as they reach the air, uniting
QUEsTIoNs.-311. What is ordinarily termed combustion? Must thelr
be two substances to produce combustion? What are they called? What
is flame? In the common lamp or candle, how are the combustible gases
supplied? Of what several parts is the flame of a cancUle composed? What
is the dark interior part?




NATURE OF FLAME.-THE SAFETY LAMP.               271
with its oxygen, with the evolution of much light and heat; and,
3d, the part, cc, outside of the part last mentioned, composed
chiefly of heated air, and mixed with a small portion of com.
bustible matter in a state of ignition.
That the dark, interior portion, a, is composed of combustible
gas, may be shown by inserting, in the
centre of the flame, one end of a small  /      /
glass. tube, as shown in the figure, and
conveying away a portion, and igniting it
as it escapes at the other end.  So, when  (
the flame of a candle is suddenly extinguished, the heat in the wick continues, 
for a short time, sufficient to decompose
the tallow, and the combustible gases Gas from centre of Flame.
continue to rise in the form of smoke;
and may often be again relighted by applying the flame of another
candle to the ascending smoke, several inches above the wick.
In the flame of a jet of gas, precisely the same phenomena, in,every particular, will be observed; —the dark central cone of
unconsumed gas, surrounded by the brilliant
hollow  cone of flame, and this enveloped in
still another less brilliant cone.  In the latter
case, the gas is previously formed and consumed
as it issues into the air, but in the case of the
candle or lamp, it is formed in the wick, and
instantly consumed as it escapes.
312. That there is really no combustion in
the dark central part of the flame, appears from
the fact that the wick remains there uncon-    _
sumed, and is even protected by the gas existing
there from  being attacked by the oxygen of   Effect of Braided
Wick.
the air.  In burning ordinary tallow candles,
the wick occasionally becomes too long, and requires to be snuffed;
but the wicks of the best spermaceti and wax candles, being plaited,
QUESTIONS. —Iow may the real character of this gas be shown? Will
the same phenomena be shown in the flame of a jet of gas? 312. Why
does not the wick of a candle burn off quite down to the tallow?




272       NATURE OF FLAME.-THE SAFETY LAMP.
the end curls outward when heated by the flame, and coming in
contact with the oxygen of the air, is gradually consumed as the
candle burns away.  The necessity of snuffing is therefore
avoided.
The plaited or braided wick, while the candle is burning,
the direction of the separate strands is upward
and inward, and of course from  the other side'
g    in which the direction is upward and outward,
Generally the simple braiding of the wick is
sufficient, but sometimes a cord or bobbin is
I    braided in with one of the strands, as represented in one of the figures in the margin; and
sometimes, also, a cord is bound to the braided
Braided Wicks.
wick, by a thread wound spirally around it.
The intensity of the light from any flame, other things being
equal, will depend upon the intensity of the combustion, and this,Ill depend in turn upon the regular and abundant supply of the
on hustible and the supporter.  When the wick of a candle:.ecomes too long, or that of a lamp is too high, only the hydrogen
of the gases formed from the decomposed oil is consumed, the
carbon escapes in a finely divided state, as a dense, black smoke.
This is because of the too rapid supply of the combustible, and
the usual remedy is to diminish the length of the wick by snuffing or otherwise, but the same thing would be accomplished by
increasing the supply of the supporter, oxygen. This last purpose is effected by the use of a glass chimney, by which a current
of air is supplied more rapidly to the flame.
By the Argand burner (so named from the inventor), a current of air is also supplied to the centre of the flame, the wick
being in the form of a hollow cylinder, as shown in the figure on
next page. Both through the centre of the flame and around
QUESTIONS. —How are the wicks sometimes made to bend outward in
the air, so that the end is consumed? Upon what will the intensity of the
light from a flame depend?  What occasions the disagreeable smoke
sometimes produced by a lamp?  How is the defect usually remedied?
What is the benefit of a chimney to a lamp? Why are hollow wicks
often used?




NATURE OF FLAME. —- THE SAFETY LAMP.             273
the outside strong currents of air are established, as shown by the arrows.   The
effect is to produce a perfect combustion
of all the oil or other combustible material               I
supplied to the flame.
It is found that the intensity of light
produced by a flame depends very much            I 
upon the amount of carbon  consumed.
The flame of pure hydrogen is very feeble, 
as is also that of the vapor of alcohol and  
ether;-and these latter contain comparatively little carbon.  But add to alcohol
one-fourth  of its volume of camphene,  il.,;i:ll!,
which is rich in carbon, and a brilliant!:
flame is produced.   This mixture con- Lamp with ollow Wick and
stitutes the common burning fluid.              Glass Chimney.
313. The blowpipe (193) is, as we have seen, simply a contrivance to supply air to the flame
firom the lungs.  The instrument is
usually applied to one side of the
flame, and as the current of air is
forced through it, it is bent towards
the opposite side.  By means of this
instrument a very intense heat may
be produced, sufficient for many important purposes. Much will depend           Use of Blowpipe.
in any particular case upon the mode of using the flame; and the
inexperienced student, before commencing, will consult works
that treat at length of this subject.
314. Safety-Lamp. —The safety-lamp is the invention of Sir
H. Davy, to avoid the danger of explosions from mixtures of the
above gases'with air, which often occur in coal mines, when
unprotected lamps are made use of.  It consists simply of a comQUESTIoNs.-What is the composition of burning fluid?  313. Describe.
the mouth blowpipe.  May a very intense heat be produced by it?
814. For what special purpose was the safety-lacrn invented?




274        NATURE OF FLAME.-THE  SAFETY LAMP.
mon lamp, the flame of which is surrounded by
wire gauze, through which, it is found, flame will
not ordinarily pass.  This lamp, as it is usually
constructed, is represented  in the figure on the:-Rl i I! left.  Its action in arresting flame is easily understood when the nature of flame is considered.  We
l,~ll  have seen that this is simply gaseous matter in a
state of combustion, and therefore is intensely
l,,l..I   heated; —now if by any means we can diminish
the heat of this gaseous matter, so that it shall fall
below the point of ignition, the combustion, and
5 Itiiiiie~l~lill    consequently the flame, must cease.   And this
effect is produced by the wire gauze.
To show the effect,
let a piece of such                             t
gauze, b, be held in
Safety-Lamp.  the flame of a candle,
a; the flame appears
to be cut off by the gauze, and the
gases pass through unconsumed, as
shown  at d, and, by  dexterous              Effect of Wire Gauze.
management, may be relighted.
The occurrence of combustible gases in coal mines is occasioned
by the action of water upon the coal; and they often collect in
large quantities in places not properly ventilated, forming mixtures with the air, ready to explode with excessive violence on the
first approach of the unprotected candle of the miner.  Before the
invention of the safety-lamp, such accidents were of frequent
occurrence; and coal miners lived and worked in perpetual fear!
All this is avoided by the use of the safety-lamp; —and, in view
of what has been said above, the mode in which it operates to
afford the desired protection is easily understood.  When this
QEsTIONS. —Describe the safety-lamp. What is flame? Will ordinary flame pass through wire gauze? What is the reason given for this
fact? How may this be shown by a lighted candle and a piece of wire
ga.uze? How are inflammable gases formed in coal mines? What is the
effect when these gases, mixed with atmospheric air, come in contact
with the flame of a lamp? What is the effect when the safety-lamp is
used?




COMPOUNDS OF CARBON AND NITROGEN.                275
lamp is carried into an atmosphere containing a considerable proportion of fire-damp, this latter immediately takes fire, and burns
freely within the gauze, but the flame is not communicated to that,
without. At first, the flame of the lamp seems to be simply cnlarged, but soon it leaves the wick entirely, and the whole space
immediately inside the gauze seems filled with flame.  When
this takes place, the miner is obliged to retire, lest, by the intense
heat, the wire of the gauze should be melted or oxydized, and
the flame communicated to the mixed gases, without. The same
effect might also be produced by strong currents of air, which
sometimes occur, forcing the concentrated flame against a particular
part of the gauze, and causing it to break, or heating it so as to
allow the passage of flame through it.
The mode in which the safety-lamp operates may be shown quite well,
by pouring a little sulphuric ether into a common glass receiver, which
should be inverted and agitated a little, so that it may be filled with a
mixture of air and vapor of ether, and then letting the lighted. lamp
dlown into it. The mixture of air and vapor of ether entering thlrough
the gauze, burns brilliantly within the gauze, but the flame is not commnunicated to that without.
It should be remarked, that wire gauze serves as a protection against
explosive mixtures of atmospheric air and the carburetted hydrogen only;
a mixture of atmospheric air or oxygen with pure hydrogen may be esplodled through a very narrow tube of great length.
Compounds of Carbon and NVitrogen.
315. There are several compounds of these two substances, but
we shall notice only one, the bicarbonide of nitrogen, C2N, or
cyanogen (from  cuatnos, blue, and gennao, to produce, because it
is an ingredient of Prussian blue).
316. ]Bicarbonide of Nitrogen, or Cyanogen —C2N, or Cy; eq., (12 +
14 =) 26.-This is a gaseous substance, and is readily formed by heating
bicyanide of mercury (to be hereafter described) in a glass retort by a
*QuESTIONS.-Will it answer for the miner to remain with his lamp in
the explosive mixture? Describe the experiment for showing the operation of the safety-lamp.  Will wire gauze in this manner prevent the
explosion of mixtures of hydrogen and oxygen? 315. What is said of
the compounds of carbon and nitrogen?  From what does cyanogen
derive its name?  316. How is bicarbonide of nitrogen, or cyanogen
prepared?




276        COMPOUND OF CARBON AND SULPHUR.
spirit-lamp. It is colorless, has a very pungent odor, and is easily campressed into a liquid; and by the cold produced by a mixture of solid
carbonic acid and sulphuric ether, this liquid may be frozen. Of the
pure gas, 100 cubic inches weigh 56'47 grains, giving it a density
of 1.82.
Cyanogen is composed of 1 vol. of vapor of carbon and 1 vol. of
nitrogen, as follows, viz.:
1 vol. vapor of carbon weighs 0-836
1 "  nitrogen          "   0'972
Weight of 1 vol. of cyanogen, 1-808
Cyanogen, though a compound, is remarkable for combining with the
elementary bodies in the same manner as an element, forming a class
of compounds which are called cyanides. Further remarks concerning it
will be deferred to Organic Chemistry.
Compound of Carbon and Su7phur.
317. These elements combine in only one proportion, forming
the following compound:
318. ]Bisulphide of Carbon-CS,; eq., (6 + 32 =) 38.-This
compound, called also sulpho-carbonic acid. is formed by heating
to redness pieces of charcoal in a porcelain tube or retort, and
then causing vapor of sulphur to come in contact with it.  The
figure on next page represents a good arrangement for the purpose, even when a considerable quantity is to be prepared.  The
retort, R, of stone ware, is first filled with pieces of well-burned
charcoal, and the tube T inserted nearly to,'the bottom, and
luted well around the neck, to prevent any escape of gaseous
matter.  It is then to be placed in a suitable furnace, and connected with a Liebig's condenser, C, and this with a receiving
vial, V, partly filled with water. A small tube of glass inserted
into the cork allows the air to escape as the vial is filled.
QUESTIONS.-Describe bicarbonide of nitrogen or cyanogen. For what
is it remarkable?  317. How many compounds of carbon and sulphur
xre known?  318. Describe the mode of preparing bisulphide of carbon,
or sulpho-carbonic acid.




COMPOUND Ol CARBON AND SULPHUR.             277
Preparation of CS2.
When everything is ready, a fire is kindled in the furnace, and
when the retort becomes well heated, pieces of sulphur are occasionally dropped into the tube T, and a cork immediately inserted.
The sulphur being sublimed by the heat comes in contact with
the heated charcoal, with which it combines, producing the compound in question. This now passing into the condenser, takes
the liquid form, and is collected in the receiver, V.
It will be observed that this process is a case of combustion
(193), the carbon being the combustible, and the vapor of sulphur the supporter; and the compound formed, CS2, is analogous
to carbonic acid, C02, which is formed when carbon is burned in
oxygen. And as carbonic acid combines with oxybases, to form
salts, the composition of which is RO,CO,, so sulphide of carbon
combines with sulphur bases, to form compounds of the analogous
form, IRS,CS2. The letter R is here used indefinitely, for any
element whatever.
Bisulphide of carbon is a colorless liquid, which boils at about
1120, and has a density of 1'27. It does not mix with water,
but dissolves readily in alcohol or ether.  Its odor is excessively
fetid and nauseous.  Both sulphur and phosphorus are dissolved in it, and may be obtained in crystals by the gradual
QUEsTIoNS.-What is said of the relation of bisulphide of carbon to
carbonic acid? May this be considered as a case of combustion? Which
of the substances is to be considered as the combustible body, and which
the supporter? What are some of the properties of bisulphide of carbon?
24




278                      SILICON.
evaporation of the solution. By its evaporation in the open air a
very considerable cold is produced, but under the receiver of the
air-pump its evaporation is so rapid as to occasion a cold of — 76~.
It burns freely in the open air, producing carbonic and sulphurous
acids, and with oxygen its vapor forms an explosive mixture.
SILICON.
Symbol, Si; Equivalent, 213; Density,?.
319. History. —Silicon was first obtained by Berzelius, in 1824.
It was then considered a metal, and named silicium, but is now
generally ranked with the non-metallic elements.  It is never
found in its separate state in nature, although it is really very
abundant in every place in silicic acid (silica), and the various
siliceous compounds which constitute the rocks and soils.  Next
to oxygen it is the most abundant element found upon the earth.
320. Preparation.-To prepare silicon a somewhat complex
substance is selected, the double fluoride
of silicon and potassium, which is a white
powder like starch.
When this compound is heated in a
glass tube with nearly its own weight
of potassium, by means of a spirit-lamp,
the fluorine combines with the potassium,
Preparatiol of Silicon.    and the silicon is separated from the mass
by washing with water, which dissolves
the fluoride of potassium and leaves the silicon very pure.
The reactions which take place are represented by the following
equation:
3KF,2SiF3 + 6K    9KF + 2Si.
QUESTIONS.-319. Has silicon sometimes been ranked with the metals?
Is it abundant in nature? 320. How may it be prepared?




COMPOUND OF SILICON AND OXYGEN.                279
321., rroperties.-Silicon, as thus obtained, is a powder of a
dark, nut-brown color, without metallic lustre, and is a non-conductor of heat and electricity.  It stains the fingers, and adhere
to everything that comes in contact with it; and when heated in
the atmosphere or oxygen gas, it takes fire and burns, with the
formation of silicic acid.
In close vessels, silicon, like charcoal and boron, is capable
of enduring a very high temperature without fusion, but is rendered harder and more compact.  It is now incombustible, even
when highly heated in the air or in oxygen gas, and is unaffected
by the blowpipe, even in contact with chlorate of potassa.
Compound of Silicon and Oxygen.
322. There is known only a single compound of these elements,
the teroxide, SiO,.
323. Silicic Acid, or Silica —SiO; eq., (21.3 + 24-) 45.3.
-This is one of the most abundant compounds in nature, and is
found quite pure in quartz, flint, calcedony, agate, &c.; and, in
combination with other substances, in the material of all soils, and
nearly all rocks.
Alone, silica is nearly infusible, but may be melted in the
intense heat of a compound blow-pipe.  It is not acted upon by
any acid except the hydrofluoric (252), but, at high temperatures,
enters into combination with the alkalies and earths.  It is very
hard, and has a harsh feeling to the fingers, even in fine powder.
In quartz crystals, which are usually six-sided prisms, terminated
by six-sided pyramids, it is familiar to.every one.
By heating silica in fine powder, with four times its weight
of carbonate of potash, in a platinum crucible, the carbonic acid
is displaced, and silicate of potash formed; which, being treated
QUESTIONS.-321. Describe the properties of silicon. 322. What compound only of silicon and oxygen is there?  323. What is said of the
abundance of silicic acid, or silica? What is said of its fusibility? Is it
acted upon by any of the acids? What is the usual form of its crystals'
What is the eLfect when silica in fine powder is heated with carbonate
of potash?




23 0            OTHER COMPOUNDS OF SILICON.
with diluted hydrochloric acid, yields a gelatinous precipitate of
hydrated silica.  This is soluble in water, and constitutes soluvble
glass, or liquor of flints,-terms sometimes used.  It is sometimes found in the waters of hot springs, as the Geysers of Iceland; and, in fact, in very  small quantities, in most natural
waters.  In this state it is taken up by the rootlets of plants, and
is found in their ashes after incineration.  It is especially abundant in the grasses and the straw of the cereal grains, and in the
stalks of rushes and reeds.
In the gelatinous state, silica has occasionally been found in
the cavities of minerals, when they have been broken.  Exposed
to the air, and especially if heated, the water evaporates, and dry,
harsh, insoluble'silica only remains.
All the different varieties of glass are silicates of different
bases, or mixtures of these silicates.  This subject will be treated
of more at length hereafter.
It is in its power thus to combine with the bases, so as perfectly to
neutralise them, that this compound, oxide of silicon, or silica, evinces
its claims to be considered as an acid.
Other Compounds of Siicon.
3624. Terchloride of Silicon-SiC13; eq., (21.3 + 106.2   ) 127.5.-This
compound is formed by heating silicon in dry chlorine, or by passing a
current of the latter over a mixture of silica and carbon when heated in
a porcelain tube.  It is a colorless, volatile liquid, which boils at about
1380, and has a density of about 1 52. By contact with water it is decomposed, producing silica and hydrochloric acid.
325. Terfluoride of Silicon-SiF3; eq., (21-3 + 57 -) 783. — This
fluoride, called also, fluo-silicic acid, is obtained by gently heating a mixture of equal parts of dry and finely-powdered glass and fluor-spar, made
into a paste with strong oil of vitriol.  The oxygen of the silica and the
fluorine of the finuor-spar here exchange places, while the sulphuric acid
combines with the lime that is formed, thus, neglecting the water of
the sulphuric acid,
3CaF + SiO3 + 3SO3 = 3(CaO,SO3) + SiF3.
QU iSTIONS.-Is silica found in nature?  Is it taken up by the roots
of plants?  Of what are all the different kinds of glass composed?
324. How is the terchloride of silicon formed?  Describe its properties.
325. Describe the terfluoride of silicon.




BORON.                           281
Terfluoride of silicon is a colorless gas, with a pungent, acid odor, and
in the open air forms dense white fumes by combining with the moisture
it contains. Its density is 3'57.
By contact with water it is at once decomposed, gelatinous silica iz
deposited, and the water is found to contain a peculiar compound, Galled
hydrofluosilicic acid, the composition of which is 3HF, 2SiF,.
The experiment is best performed by putting the materials in f dry
retort, A, connected with a receiver, R, partly filled with wate. and
R4k
Preparation of Gelatinous SiOs.
placed so that it can be gently shaken occasionally, in order that the
film of silica forming upon the surface may be broken up, and a fresh
surface of water exposed.
When hydrofluosilicic acid is saturated with a base, as potassa, the
hydrogen is replaced by an equivalent quantity of the metal of the base.
Thus,
3IF, 2SiF3 + 3KO = 3KF,2SiF3 + 31HO.
The compound 3KF,2SiF3 is the double fluoride of silicon and potassium (320) used in the preparation of silicon.
Silicon is capable also of forming compounds with sulphur and bromine.
BORON.
S.nmbol, B; Equivalent, 109; Density, 2.
326. History.-Boron, in a separate state, was first obtained
by Davy, in 1807. It is found in nature only in combination,
and in comparatively small quantities.   Though it occurs in
QuEsTIONS. —How  is terfluoride of silicon affected by contact with
water?  What is the composition of hydrofluosilic acid?  326. When
and by whom was boron discovered?  Is it found naturally in a separate
state?
24*




282                         BORON.
several minerals, as datholite and boracite, it is obtained chiefly
from the waters of certain hot springs, especially in Tuscany and
the Lipari Islands, where it occurs in solution, as boracic acid.
327. Preparation.-To prepare boron, first make a saturated
solution of borax in boiling water, and, while hot, pour in sulphuric or hydrochloric acid until the solution tastes distinctly
sour.  As it cools the boracic acid will separate in white, shinink
scales, which are to be thoroughly washed
and dried by fusion in a platinum  crucible.  We thus obtain boracic acid, which
is then to be mixed with potassium (or
sodium), and heated in a glass tube, as
in the preparation of silicon.  A part of
the boracic acid yields its oxygen to the
Preparation of Boron.  potassium, and the potassa so formed enters
into  combination with  the rest of the
boracic acid to form  borate of potassa.  By treating the mass
with cold water the latter compound is dissolved, and the boron
is seen floating in the liquid as a fine powder of a brownish color,
and may be collected on a filter.  Before filtering, some sal ammonia should be dissolved in the mixture, which has the effect
to prevent the escape of the finely-powdered boron through
the filter.
The mode in which the sal ammonia operates to produce this
effect is not understood.
328. Properties.-Boron is a dark olive-green powder, without
taste or smell, and incapable of fusion in the strongest heat.  It
is insoluble in water or alcohol.  Heated in the open air to about
600~, it takes fire and burns brilliantly, forming boracic acid.  It
is a non-conductor of electricity and heat.
QUESTIONS.-327. How is boron prepared? Describe the reactions
which occur. 3828. Describe boron. How is it affected when heated?




OTHER COMPOUNDS OF BORON.                    283
Compound of Boron and Oxygen.
329. Boracic Acid-BO,; eq., (10 9 + 24 =) 34'9.-  This
acid may be obtained from the common borax of commerce,
as just described in the preparation of boron; it is also produced
by the combustion of boron in the air.
Boracic acid is slightly soluble in water and in alcohol; and
when the latter solution is inflamed it communicates to the flame
a beautiful green tinge,      A
which  is characteristic
of this substance.  To
make the  experiment,
fill a common dropping
tube, of the form  A B
in the figure, with the
in the figure, with the         Green Flame produced by B03.
solution; and, inserting
a cork firmly in A, apply the heat of a lamp to the bulb, and
inflame the jet of liquid as it issues from the capillary orifice, B.
The flame will be of a beautiful green.
The color of the flame may also be shown very well simply
by moistening one end of a pine stick in the solution, and inflaming it.
Other Compounds of Boron.
330. Terchloride of Boron-BC1,; eq., (10.9 + 106.2-) 117l. —This
compound is formed by preparing an intimate mixture of boracic acid
and carbon, and causing a current of dry chlorine to pass over it in a
porcelain tube, kept at a red heat. It is a colorless gas, of a density of
4.03;-in the open air it forms dense white fumes with the moisture contained therein, and in contact with liquid water it is instantly decomposed, forming hydrochloric and boracic acids.
331. Terfluoride of Boron —BF3; eq., (10.9 + 57 =) 67-9.-Terfiuorido
of boron, or fluoboracic acid, is a colorless gas, of specific gravity 2 37.
It is prepared by heating in a gun-barrel a mixture of 2 parts of pulQuaESTIONS.-329. How is boracic acid procured from borax? Describe
this acid. What color does it give to the flame of alcohol when dissolved
in it? How may it be shown? 330. How is the terchloride of boron
formed?  331. How is the terfluoride of boron formed?




284          TIlE METALS.- GENERAL PROPERTIES.
verized fluor spar (fluoride of calcium), and 1 part of fused boracic acid.
It has a strong affinity for water, which dissolves 700 or 800 times its
own volume of the gas, and acquires a sour taste and a strong acid
reaction, and chars wood like oil of vitriol when brought in contact with it.
Boron combines also with sulphur, forming a tersulphide, BS3.
THE METALS.
General Properties.
332. Characteristic Properties. - The metals are generally
good conductors of electricity and heat, and possess a peculiar
lustre called the metallic lustre, which can scarcely be imitated by
other substances.   When their compounds are decomposed by
the galvanic battery, they always make their appearance at the
negative electrode (112), and are therefore, without exception, to
be considered as electro-positive.  But these properties are much
more distinct in some metals than in others.  Most of the metals
are also characterized by their great density, as gold and platinum;
but two at least, potassium and sodium, are lighter than water.
All of them except mercury are solid at ordinary temperatures.
The ancients were acquainted with only seven metals, viz.:
gold, silver, iron, copper, mercury, lead, and tin; but there are
now known, with certainty, forty-seven; and the discovery of
several others has been announced, though perhaps not fully
proved.
333. Sources of the Mletals.-Though several of the metals
are found in animal and vegetable substances, they seem to forim
no necessary part of any. organic compounds. Most of them, as
iron, lead, and zinc, are found in the earth in combination with
other non-metallic elements, as oxygen, sulphur, or arsenic, and
are said to be m'neralized, and the compound is called an ore;
but a few, as platinum, gold, and sometimes copper, silver, bisQUESTIONS. — 32. What are some of the characteristic properties of the
metals? I-low many metals were known to the ancients? Are all the
metals solid at ordinary temperatures?  333. Do any of the metals form
any part of organic compounds? What constitutes a metallic ore?




THE METALS.  GENERAL PROPERTIES.                 285
muth, &c., occur in the metallic state, and are said to be found
native.  Some are found in the form of salts, especially as silicates, cairbonates, and sulphates.
The metals occur sometimes in beds, which are more or less
parallel with the earthy strata containing them, but more frequently in veins or lodes, which traverse the strata in every
direction.  The veins are more abundant in the older than in the
newer rocks; and their appearance indicates that they are fissures
which have been produced in the strata subsequent to their
deposition, and then filled by filtration of the metallic matter
from  above, or by injections from  below.  Besides the metallic
compounds, or ores, these veins always contain other minerals, as
quartz, carbonate of lime, heavy spar, and fluor spar, which constitute the gangue, or vein-stone.
334. Relations to Light. —The relations of the metals to light
are in some respects peculiar and interesting.   Their peculiar
lustre, called the metallic lustre, has already been alluded to;
this lustre entirely disappears when they are reduced to a fine
powder, but reappears when the substance is rubbed with a
burnisher.
All the metals except gold are perfectly opake, even when reduced to
the thinnest lamine possible. Gold in the form of leaf transmits a feeble
green light. The best method to observe this light is to place an unbroken leaf upon a piece of white plate glass, and press it gently with a
bunch of cotton to make it adhere. It may then be preserved for any
length of time.
The color of most of the metals, seen in mass, is grayish-white,
as platinum, iron, lead, and potassium, but seen in powder the
color is a deep gray. By burnishing the particles, the original
grayish-white is restored. Gold in mass has a beautiful yellow
color, and in powder a deep purple, almost black.  Copper and
titanium are red.
335. Malleability and Ductility. —Some metals possess the
property of malleability, that is, admit of being beaten into thin
QUESTIONs.-When is a metal said to be found native?  334. What is
said of the lustre of the metals? Is this lustre seen in a metal when it is
reduced to powder?  Are most of the metals opake even when reduced
to thin laminae?  What is the color of most of the metals?  What is
said of their color when in fine powder?  What metal is yellow?  What
metals are red? 335. What malleable metals are mentioned?




286          THE METALS. —OENERAL PROPERTIES.
plates or leaves by hammering. The malleable metals are gold,
silver, copper, tin, platinum, palladium, cadmium, lead, zinc, iron,
nickel, potassium, sodium, aluminum, and frozen mercuryr.  The
other metals are either malleable in a very small degree only, or,
like antimony and bismuth, are actually brittle.  Gold surpasses
all the other metals in malleability; one grain of it may be
extended so as to cover about 52 square inches of surface, and
the film will have a thickness of only a 1ooth of an inch.
Nearly all malleable metals may be drawn out into wires, a
property which is expressed by the term ductility. The only
metals which are remarkasble in this respect are gold, silver,
platinum, iron and copper.
The process of wire-drawing consists in drawing the metal
through round holes made in plates of steel for the purpose. The
steel plate is made with a number of holes, of different diameters,
through which the rod of metal is made to pass successively, its
diameter at each operation being a little reduced antdits length
increased.
A machine for this purpose is represented by the accompanying figure.
A B is the plate of steel through which the wire is drawn,-it is held,_    _     _' _ _  _   _
Wire Drawing.
firmly in its place by a support, D. A rod from the rolling mill, in the
form of a coil, or a coil of wire, is placed upon the reel, F G, which turns
QuEnsTIoNs. S-What metals are mentioned as being brittle?  What is
said of the malleability of gold? Are the malleable metals also ductile?
Describe the process of wire-drawing?




THE METALS.- GENERAL PROPERTIES.                287
easily upon its axis; and the end of the wire, drawn out a little with the
hammer, is passed through the plate and attached to the drum, C, which
is turned by machinery, and by its motion winds the wire around itself,
at the same time, of course, withdrawing it from the reel.  To form
small wire it is in this way passed many times through the plate; and,
to prevent its becoming hard and brittle, it is several times annealed
during the process. The passage of the wire through the plate is facilitated by dipping the coils occasionally in a moderately strong solution
of sulphate of copper, by which it receives a thin coating of metallic
copper.
336. The malleability and ductility of any substance would
seem to depend very nearly upon the same properties, but it is
found in the case of metals that they are not precisely the same.
In the following table, in the first column, several of the metals
are arranged in the order of their malleability, beginning with
the most malleable; in the second column, the same metals arc
arranged in the order of their ductility.  The table is from
IRegnault.
MaZleability.               Ducti7ity.
1. Gold.                     1. Gold.
2. Silver.                   2. Silver.
3. Copper.                   3. Platinum.
4. Tin.                      4. Iron.
5. Platinum.                 5. Nickel.
6. Lead.                     6. Copper.
7. Zinc.                     7. Zinc.
8. Iron.                     8. Tin.
9. Nickel.                   9. Lead.
Both the malleability and ductility of several of the metals
vary with the temperature. Thus iron, though partially malleable and ductile at the ordinary temperature of the atmosphere,
is much more so at a red heat; and zinc is very malleable from
2120 to 3500, but loses this property if cooled down to 32~, or
heated to 600~.  At the latter temperature it is decidedly brittle.
When a metal has been hammered or rolled, or drawn out into
wire, its hardness as well as density is increased; and it becomes
less malleable.  This property, however, is restored by an-nealig
it, which consists in heating it to redness and then cooling it
QUESTIONS.-336. Do the malleability and ductility of a substance
depend upon the same properties? Are the malleability and ductility
of some of the metals affected by their temperature?  What is sa.id
of iron and zinc in this connection?  What is meant by the annealing
of a metal? Why is this often necessary in working maany of the metals?




THE METALS.-GENERAL PROPERTIES,
slowly. But the tenacity is often very much diminished by the
process, sometimes even more than one-half.
337. The tenacity of a metal is determined by ascertaining the
greatest weight a wire made of it, of a given diameter, will sustain. The determination is made by attaching one end of the
wire to a firm support, and to the other end fixing a pan to
receive the weights.  Wires 0'787 of a line in diameter (=  to
about t    th of an inch), made of the  several metals mentioned
below, were loaded  gradually until they broke with  the weights
placed  opposite to  their names in  the following  table.   These
numbers therefore indicate their relative tenacities.
Pounds.                                Pounds.
Iron wire.......................... 549  Gold................................. 151
Copper.....................     302  Zinc......................       109
Platinum............................. 274  Tin...........................  34~
Silver......................... 187  Lead.................................  27-i
When a metallic wire is tested in  this manner its length  is
increased with the weight, but if the load has not been too great
it contracts again to the same length as at first, on the removal
of the load.   If the load be increased beyond a certain point, a
permanent elongation is produced; and usually no great further
increase is needed to break the wire.
338. The specific gravity of the metals, like many of their
other properties, are very dissimilar.   The  specific gravities of
some of the more important of them are contained in the following
Table of thle Specific Gravity of Metals at 600, compared with Water as Unity.
Platinum......................... 20 98  Cobalt............................  8.53
Gold................................ 19.02  Nickel..................... 8'27
Tungsten....................... 17'65  Manganese......................... 8.01
Mercury........................... 13-56  Iron.................................. 7'78
Palladium......................... 1105  Tin..................................  7'29
Lead................................ 11-35  Zinc................................. 6'86
Silver.............................. 10'47  Antimony........................... 6'70
Bismuth...........................   9'82  Chromium.......................... 5 09
Uryanium...........................  9'00  Titanium............................ 503
Copper.............................  8-09   Aluminum............3.....  307
Cadmium..........................  8'60  Sodium..................... 0'97
Molybdenum...................  8.06  Potassiun......................... 0'86
QUESTIONS. — 337. How is the tenacity of a metal determined?  What
metal of those mentioned has the greatest tenacity? What is the second?
338. What is said of the specific gravity of the metals?  What metal is
mentioned  s having the greatest specific gravity?  What is the second?




THE METALS.- GENERAL PROPERTIES.                 289
339. Crystaline Characters. -Many of the metals have a distinctly crystaline texture.  Iron, for example, is fibrous; and
ziec, bismuth, and antimony are lamellated.  Metals are sometimes obtained also in crystals-and most of them, in crystalizing,
assume the figure of the cube, the regular octahedron, or some
form  allied to it.  Gold, silver, and copper occur naturally in
crystals, while others crystalize when they pass gradually from
the liquid to the solid condition.  Crystals are most readily procured from those metals which fuse at a low temperature; and
bismuth, from  conducting heat less perfectly than other metals,
and, therefore, cooling more slowly, is best fitted for the purpose.
Several of the metals form small but very beautiful crystals, as
they are slowly separated from their solutions by the galvanic
current.  If in a solution of sulphate of copper we place two
plates of copper, and connect them with the two electrodes of a
galvanic battery in feeble action, after some time the plate on the
negative side will become covered with small crystals of metallic
copper, while the other plate will be gradually dissolved.
It is believed that some of the metals, in certain peculiar circuinstances, may assume a crystalline structure, even when in the solid
state.
340. Alloys. —Many of the metals are capable of combining
with each other, forming compounds called alloys, which will be
described in their proper places.  They possess all the characteristic physical properties of the pure metals, and many of them
are of great service in the arts.   Generally, alloys are more
fusible and more oxidable than their constituents separately.
Their malleability and ductility usually are much less, and their
hardness greater, than those of the metals of which they are
composed.
Compounds of mercury with other metals are called ama/7yaqvs.
341.   etallurgy.-Thle reduction of the metals from  their
ores, and the methods adopted in working them in the arts, conQUESTIONS.-88339. Do any of the metals possess a crystaline texture?
What metals are mentioned as being sometimes found ill crystals? Doescribe the mode of obtaining crystals of copper by the galvanic process?
840. What are alloys?  Do alloys possess the usual physical properties
of the metals?  What is said of their filsibility?  What of their malleability and ductility?  What are namalgams?  341. What is metallurgy?
25




?2903       THE METALS.-O- NE'RAL PROPERTIES.
stitutes a distinct branch of chemical science, called by this
name.  AMost of the metals have an extensive range of affinity;
many of them form  compounds with nearly all the non-metallic
elements, and all without exception combine with oxygen.
As many of the metallic ores are oxides, the reduction of this
class of compounds becomes particularly important.  It is effected
in several different modes, as,
1. By mere heat. By this method the oxides of gold, silver,
mercury, and platinum may be decomposed.
2. By the united agency of heat and combustible matter.
Thus, by transmitting a current of hydrogen gas over the oxides
of copper or iron heated to redness in a tube of porcelain, water
is generated, and the metals are obtained in a pure form.  Carbonaceous matters are likewise used for the purpose with great
success.  Potassa and soda, for example, may be decomposed by
exposing them to a white heat, after being intimately mixed with
charcoal in fine powder.  A  similar process is employed in
metallurgy for extracting metals from their ores, the inflammable
materials being wood, charcoal, coke, or coal.  In the more delicate operations of the laboratory, charcoal and blactc flux* are
employed.
3. By the galvanic battery.  This is a still more powerful
agent than the preceding; since some oxides, such as baryta
and strontia, which resist the united influences of heat and charcoal, are reduced by the agency of galvanism.
4. By the action of deoxdizing agents on metallic solutions.
Phosphorous acid, for example, when added to a liquid containing
oxide of mercury, deprives the oxide of its oxygen, metallic lmercury subsides, and phosphoric acid is generated.  In like manner
one metal may be precipitated by another, provided the affinity
of the latter for oxygen exceeds that of the former.  Thus, when
mercury is added to a solution of nitrate of oxide of silver,
metallic silver is thrown down, and oxide of mercury is dissolved: Blatckcflux is prepared by deflagrating nitre with twice its weight of cream of tartar
When equal weights are used, it constitutes white flux.
QurSTr Ns.-Whlat is said of the affinity of the metals?  What aire
most of the metallic ores?  What are some of the different mneans by
wsich these ores inay be reduced?




SALINE COMIPOUNDS,  OR SALTS.                  291
by the nitric acid.  On placing metallic copper in the liquid, pure
mercury subsides, and a nitrate of the oxide of copper is formed;.and from  this solution metallic copper may be precipitated by
mneans of iron.
To reduce the other compounds of the metals, other modes are adopted,
which cannot here be particularly described.
The relations of the various metalloids to the metals will be described
as each of these latter elements shall come in review before us, so fal as
demanded by the special object of the work.
342. Classification of the Ifetals. -  The metals have been
variously classified by different writers; but the following arrangeament into six groups will probably answer our purpose as well as
any we can adopt.
1. Metals, the protoxides of which are alkalies.
2. Metals, the protoxides of which are alkaline earths.
3. MIetals, the protoxides or sesquioxides of which are earths.
4. MIetals which, at a red heat, decompose the vapor of water,
but are not acted upon by liquid water.
5. Metals which are incapable of decomposing water, and whose
oxides are not reduced by the mere action of heat.
6. Metals whose oxides are reduced by a red heat.
Saline Compouncs, or Salts.
343. A  salt is a compound of two other binary compounds,
which sustain to each other the relation of acid and base; the
former being electro-negative in reference to the latter, which
is electro-positive. Thus, sulphate of s6da, NaO,SO3, is a compound of sulphurie acid (teroxide of sulphur) and soda, which is
the protoxide of sodium; the former being electro-negative in
reference to the latter, which is electro-positive.
The acids take their name from  the fact that when soluble
their taste is very generally sour,-but this may not always be
QUESTIONS.-342. What are the metals included in the first group?
In the second group?  In the third? In the fourth?  In the fifth?  In
the sixth?  343. What is a salt?  Illustrate by an example. HIow are
the acids generally characterized?




292              SALINE COMPOUNDS, 01t SALTS.
thle case; they are mostly combinations of two metalloids, as the
sulphuric, nitric, and hydrochloric acids, but sometimes they are
formed of a metal and metalloid, as the manganic and chromic
acids, and the sulphides of tin and antimony, which are capable
of acting as acids.  Most of them  have the property of changing
the blue solution of litmus to red.
The bases, or electro-positive  binary compounds, are always
formed by the combination of a metal with a metalloid, as the
protoxide of potassium (potassa), the protosulphide of potassium,
and the protoxides of iron, copper, and silver.
344. Oxysalts. -A  large majority of all known acids and
bnses are oxides, called oxacids  and otxybases; and the salts
formed by their union are therefore called oxysalts.  They are
therefo-re double oxides.
The metallic oxides, in regard to their disposition to combine
with each other as acids and bases, and with the oxides of the
inetalloids, to form  salts (as suggested by Regnault), may be
divided into several very distinct classes, as,
1. Basic oxides, which combine readily with acids and form  definite,
crystalizable salts.  Most of them are protoxides, as potassa, KO, soda,
NaO, protoxide of silver, AgO, and the protoxide of iron, FeO. A few
are sesquioxides or suboxides.
2. A cid oxides, which, as the name implies, possess acid properties;thlley combine with bases to form salts, and very generally change the
blue solution of litmus to red. Most of them  are bi- or teroxides, as
plumbic acid, PB02 (binoxide of lead), chromic acid, Cr03, and manganic acid, Man0,.  Occasionally they are still higher oxides, as permanganic acid, Mn207.
3. Nreutral oxides, which may combine with either acids or bases, as
alumina, A120a, and the sesquioxide of antimony, Sb203,; or with neither,
as the binoxides of silver, potassium, b.arium, and strontiumu.  Some
of these, by the action of acids, especially if heated, are decomposed.
4. Saline oxides, which result from the combination of a basic metallic
oxide with a higher oxide of the same metal, as the magnetic oxide
of iron, FeO04, which is really a compound of the protoxide, acting as a
base, with the sesquioxide, acting as an acid; and its proper formula is
therefore FeO,FeO03. The oxides of manganese, Mn0,O, and of chromium,
Cr]304, fiurnish other examples.
QUESTION. —Are most of the acids formed by combinations of the
metalloids? Do some of the metals form1 acid compoounds?  I-Tow do the
acids generally affect the blue solution of litmus? Of what are the oases
mostly composedl?  344. What is said of a majority of all the known
acids and bases? What four classes of metallic oxides are mentioned 9




SALINE COMPOUNDS, OR SALTS.                   293
345. Salphur Salts.-Two sulphides often combine, forming
double sulphides, analogous to the double oxides.  They possess,
in many respects, similar characters to the double oxides or oxysalts, and are called sulVphiur salts.
Some of the principal sulphur bases are the protosulphides of
potassium, sodium, lithium, barium, strontium, calcium, and ruagnesium; and some of the more important sulphulr acids are the
sulphides of arsenic, antimony, carbon, tin, gold, and hydrogen.
T'he sulphur salts generally are so constituted that if the sul[
phur they contain were replaced by an equivalent quantity of
oxygen, oxysalts would be produced. Thus, the carbosulphide
of potassium, KS,CS,, when  the sulphur is replaced by oxygen,
becomes carbonate of potassa, KO,C02; and, in like manner, the
double sulphide of potassium  and arsenic, KS,AsS,, by a similar
substitution, becomes arseniate of potash, KO,AsO5.
346. Chlorosalts.-The chlorosalts are double chlorides, one
of the simple chlorides acting as a chlorobase, and the other
as a cbhloroacid, as the double chloride of gold and potassium,
KCl,AuC13, called also  atrochlorate of chloride of potassium,
and platinochlorate of chloride of sodium, NaCI,PtCI2.
In the same manner two iodides (an iodobase and an iodoacid) bromides, or fluorides, may unite to form in each case a series of salts
analogous to the preceding, but not much is known of them.
It is to be observed that these combinations take place olly between
members of the same series, as oxides with oxides, snilphides with sulphides, &c.; it is evidently possible that members of different series may
unlite, as an oxide with a chloride, a chloride with a sulphide, &c.; but
it is a question not fully settled whether such compounds are ever really
formed.
347. Haloid Salts.-Besides the compounds recognised by the
above remarks as salts, the binary compounds of chlorine, iodine,
oromine,  and fluorine with many of the metals, have been classed
with the salts by Berzelius and other eminent chemists, because
of their resemblance, in many of their properties, to the salts,
QUETIONs. —345. What are st7.hzr salts?  Whallt is said of the constitution of the sulphur salts?  Give an example. 246. What are chloresalts?   May the iodides, bromides, &c., form  similar series of salts 
Are these combinations always between members of the same series?
347. What are haloid salts, so called? Are these compounds salts, according to the definition of a salt adopted above?
25 




294              SALINE COIMPOUNDS, OR SALTS.
properly so called.  To distinguish them  frnom  the salts proper;
they have been called haloid  salts.  But we prefer to limit the
definition of a salt, as given above, although in so doing we of
course exclude common salt, chloride of sodium, from  the class.
The elements, chlorine, iodine, &c., which, by coambining with metals,
form the so catlled haloid salts, combine also with hydrogen, forlini
acid compounds called hydracids (168), as the hydrochloric, hydriodic
&c. Now when powerful hydrous acids are brought in contact with tlhe
haloid salts, important reactions take place, dependent upon the water
of the acid.  Thus, by the action of oil of vitriol upon chloride of potassium, we obtain sulphate of potassa and hydrochloric acid, as shown in
the following ecuation:
KC1 -+- SO3,IO = KO,Ss + HC1.
H-Ire the water of the acid is decomposed, yielding its oxygen to the
potassium to fori potassa, and its hydrogen to the chlorine to form hydrochloric acid.
So, on the other hand, the action of a hydracid on an oxybase results
in the production of a haloid salt and water.  Thus,
KO + HCl = IC1 + HIO.'ig. NIeutriai za tioon of Acid and Base.-When an acid and
base combine to form a salt, the pecaliar and characteristic properties of each, in a great measure, disappear, the new compound
formed not being characterized by the properties of either of its
ingredients, but possessing others entireiy distinct.   Thus, an
acid is generally sour to the taste, and changes vegetable blues
to red, but the salts it may form with bases possess neither of
these properties; so, also, the alkalies are caustic to the flesh and
taste, and combine with oils to form  soaps, but the salts which
they form with the acids are entirely destitute of these properties.
nMost of the other peculiar properties of both acids and bases,
when the two combine, are affected in the same manner, and
they are therefore said to be neutralized.
349. Salts are often spoken of as divided into the three classes of
neutral salts, super or acid salts, aend sub or basic salts; but the distinction
QUrESTIONS. —Wfhat is said of the elements chlorine, iodine, &c., which
form the so-called haloid salts by combining with the metals?  What
reactions take place when poweriful hydrous acids act upon these salts?
Give an illustration.  3848. When an acid and base combine do the pecun
liar prope-ties of each disappear?  Give some further illustration
349. What three classes of salts are mentioned?




SALINE COMPOUNDS, OR SALTS.                       295
cannot always be made with accuracy.  In general, a neztlral salt is
formed by the union of a single equivalent of the acid and base, while
an acid salt contains two or more equivalents of acid to one of base; and
a sub or basic salt contains two or more equivalents of base to one of acid.
But this is to be understood as liable to many exceptions.  Frequently
salts denominated neutral contain as many equivalents of acid as there
are equivalents of oxygen in the base.  Thus, the neutral sulphate of
soda, is NaO,S03, and sulphate of the protoxide of iron FeO,SO, but the
sulphate of the peroxide of iron is Fe203,3SOs.
Some few acids have the property of combining with bases in such ~
manner that one equivalent of acid will hold in union with it one, two,
three (or even more) equivalents of base, and yet these several salts are
considered as neutral; such acids are called polybasic acids.  Phosphoric
acid (282) furnishes an instance of the kind.
350. Solubility and Crystalization of the Salts.-Nearly all
the salts are solid at ordinary temperatures, and very many of them
are susceptible of crystalization.  Very generally they are more
soluble in warm  than in cold water, and often their solubility'increases in proportion as the temperature of the water is elevated.   The following  table shows the  quantity of nitrate of
potash soluble in 100 parts of water at several different temperatures:
Temperatures.                   Parts soluble in 100 parts water.
320......................................  13.3
640.............................................  29.0
113~0...........................................  74.6
2070............................................  2360
In some cases, the solubility rapidly increases as the temperature is raised, up to a certain point, and then diminishes.  Sulphate of soda (Glauber's salt) furnishes an instance of this kind.
Of this salt 100 parts of water, at 320, take up 12 parts; at 770,
99 parts; at 91~, 322 parts;-but above this temperature the
solubility diminishes, so that at the boiling point only about 212
parts will be held in solution.
Q-ESTIoNs. — What in general is a neutral salt?  What is a super or
acid salt?  What is a sub or basic salt?  Do salts denominated neutral
often contain as many equivalents of acid as there a-re equivalents of
uxygen in the base?   Give an example.  What are polybasic acids?
350. Are the salts usually solid at ordinary temperatures?   Are they
nlore soluble in warm  or cold water?  What is said of the solubility
of nitrate of potash in water at different temperatures?  How is the
solllubility of sulphate of soda in water affected, as the temperature of the
water is raised?




296             SALINE COMPOUNDS, OR SALTS.
Crystals of soluble salts may generally be obtained by making
a saturated solution at an elevated temperature and allowing it, to
cool slowly.  Thus, a saturated solution of alum at 100~ or 1500,
on cooling deposits beautiful octahedral crystals; and if a tree
or basket made of copper wire is placed in the solution when
warmn, the crystals will attach themselves to it in various positions, presenting a very beautiful appearance.
351. Salts soluble in water,-and even some that are insoluble
— often retain in their crystals a portion of water, which is called,water of criystalization.  Thus sulphate of soda in crystals contains 10 equivalents of water, and its proper formula is NaO,SO3
+ 10IO.  This is the case however only when the crystalization
takes place at a temperature below  920 or 930; when it crystalizes at a higher temperature the crystals are anhydrous.
The same salt will often combine with very different quantities
of water when deposited from its solution at different temperatures.
Sulphate of protoxide of manganese, crystalized from an aqueous
solution, at 43~0 has the formula, MnO,803 + 7H0; when crystalized between 43~ and 68~ its formula is MnO,SO,3 + 6HO;
and again when crystalized between 68~ and 86~, its formula is
MnO,S0, + 4H0.
When a salt of the kind last mentioned is heated in the open
air, it gives up its water in successive portions, as the temperature is raised. Sometimes the last equivalent of water is held by
a much stronger force than the rest, and can be driven off only
by a red heat, and then an entire change in the nature of the
salt takes place.  The water in such a case is called constsitutional
water.
352. Sometimes a salt in a dry atmosphere loses a part or all
of its water of crystalization, and falls to powder; it is then said
to effloresce. Again, some salts absorb moisture from the air, and
are then said to deliiquesce.  Common pearlash (carbonate of potQUESTIONS.-Iow may crystals of salts soluble in water often be obtained?  351. What is water of crystalization?  Give an illustration.
Will the quantity of water of crystalization often depend upon the temperature of the solutions from which the crystals are deposited?  WBat
will be the effect when a salt of this kind is heated? 352. When is a
salt said to effloresce? When to deliquesce?




SALINE COMPOUNDS, OR SALTS.                   297
ash) is an instance of a deliquescent salt.  Left in the open air
for a timne, it will absorb sufficient water to effect its solution.
353. Water holding a salt in solution invariably has a higher
boiling point than pule water.  The following table shows the
boiling points of saturated solutions of several of the salts.
Salts.            Parts of Salt in 10          Boiling Point.
parts of water.
Chlorate of potash............  615.............................. 2200
Common Salt.............. 41.0..................... 227~
Nitrate of potash..............  3350.............................. 241
Nitrate of Lime................. 362.0............... 8....... 3040
But the steam from such boiling solutions, as it escapes into the
open air (omitting any regard to variations of atmospheric pressure), will always be of the same temperature of 2120~.
When a hydracid, as the hydrochloric, HCI, acts upon a metal,
as zinc, the acid is decomposed, and a chloride of the metal formed,
the hydrogen being set free; thus,
Zn + HCl    ZnC1 + H.
So when liquid hydrochloric acid is poured upon potash, the
reactions are
KO + HCl,HO = KC1 + HO + H.
In both these cases, therefore, as will be seen by an examination
of the formulra, the particle of hydrogen of the hydracid has
simply been displaced, and a particle of metal substituted.  Now
all the oxyacids, or nearly all,-at least in their active state,contain water, as the sulphuric acid, SO,,HO, and nitric acid,
NOs5HO. They may indeed be obtained free from water, as
SO,, and NO,, but they are then solid and quite inert, possessing
none of the active properties of the liquid acids, which, however,
they immediately assume on the addition of water.
The reaction between zinc and oil of vitriol is
Zn +- S03,I-O = ZnO,SO, + H1.
QUEsTIONs.-353. What is said of the boiling point of water holdina a
salt in solution?  What is said of the temperature of the steam formed?
When a hydracid acts upon a metal what are the reactions that take
place?  What when hydrochloric acid acts upon potash?  In these cases
is the hydrogen, simply replaced by the metal?  Is the result the same
when the hydrated oxyacids act upon the metals?  Explain by reference
to the action of sulphuric acid upon zinc.




298   SPECIAL DESCRIPTION  OF THE METALS. —POTASSIUIM.
Now as hydrated sulphuric acid only, SOHIO, is capable of acting
upon this metal, and not the dry acid SO,, may we not in this
case also, in like manner, consider the metal as simply replacing
the hydrogen?
If this view be adopted, as it has been by some eminent
chemists, then it is required that the formulae of the hydrated
acids, the sulphuric, nitric, &c., should be changed accordingly,
-sulphuric acid being not SO,,HO, but S04,,H, or, as generally
written, H,SO4.  So also nitric acid is to be considered, not
NO5,HO, but I,NO6, and so of other acids. —
We shall not discuss the subject further, but simply give the
formiulae for several well known salts, according to the old and
generally received view, and also according to the new view.
Salts.           Common Theory.                   New Theory.
Sulphate of Soda............ NaO,S03........................,S04.
Sulphate of Zinc............. ZnO, SO03.......................   Zn, S04.
Nitrate of potash............ KO,NO5............K......... K,NO0.
Chlorate of potash........... KO,ClO1.......................... K, Cl0o.
Separate Description of the letals.
354. The classification of the metals adopted in ithis work has
already been indicated (342).
GROUP I.
POTASIUiM    o nMetals, the protozides of which are alkalies.-The pro.toxides
PoTAS S,   tof these metallic elements are very. soluble in water, and
LI~THXIIUMri   Ppossess in an emincnt degree the peculiar properties denomi
nated alkaline properties.
POTASSIUM.
Symnbol, K  (KICaTiz )J Equivalent, 392; Density, 0 865.
355. History..-Potassium  was first obtained by Sir 1H. Davy
in 1807, from  potash, which is the protoxide of the metal.  He
QuESTIONS.-If this view be adopted, how should the formula for cominon sulphuric acid, or oil of vitriol, be written?  How that for nit.ric,cid?  354. What metals are included in the first group?  How are
they characterized?  355. By whom was potassium discovered?




POTASSIUM.                          299
procured it by subjecting a piece of caustic potash, slightly
moistened, to the action of a powerful galvanic current, when
oxygen made its appearance at the positive, and the metal potassium at the negative, electrode.  Previous to this time, potash
and the other alkalies and earths had been considered as simple
substances. Potassium, in combination with oxygen and other
bodies, is very generally diffused in the rocks and soils of every
place, but is never found in nature in a separate state. It is
contained in most vegetable and many animal substances.
356. Preparation.-This metal is best prepared by heating
intensely dry carbonate of potash mixed intimately with half its
weight of fine charcoal-powder and iron filings. The potash,
being an oxide of potassium, at a high temperature yields its
oxygen to the charcoal and iron, and itself distils over into a
receiver prepared for the purpose.
The following apparatus answers well for the operation. A com-.
mon mercury bottle,
A, covered with an
infusible  lute, and
well dried, is threefourths  filled  with
cream  of tartar that'. 
has been previously
charred and  mixed
with  one-fourth  or
one-fifth of its weight
of pulverized  char-  E
coal, and placed in a
proper furnace, with
a piece of gun-barrel,    K     h
B, about a foot in
leng t h,  extending
outward and connect-                            ENRON" 
ing with a receiver, C.          Preparation of Potassium.
QuEsrIoNs. —How did Sir H. Davy procure potassium?  How were
potash and the other alkalies considered previous to this time? Is potash very generally diffused in nature?  356. How is potassium now
usually prepared? What is the effect produced by the charcoal?  De.
scribe the apparatus figured in the margin, and the mode of using it.




300                     POTASSIU M.
A fire of hard coal is then kindled in the furnace (represented
in section in figure), which should have a good draft, by connecting with a chimney, G0F, of sufficient height, in order to
produce the greatest heat possible; and the metallic potassium,
as it is liberated in the gaseous state, escapes through the iron
tube, B, and is condensed and collected in the bottom of the
receiver, C.  In this receiver some naphtha is placed, to protect
it from the atmosphere.
Charred cream  of tartar is used because it furnishes an intimate mixture of carbon and carbonate of potassa, but instead
of it dry carbonate of potash (pearlash) may be mixed intimately
with half its weight of pulverized charcoal.
The receiver, C (seen in section), is best made
of sheet copper, in two parts, M and N, the upper
part, N, being without a bottom, and fitting accurately into the lower part, M.  The upper part, N,
C is also divided into two parts by a vertical partition,
as shown in figure; it is also provided with two
tubulures, o and p, directly opposite each other, the
one, o, to receive the end of the gun-barrel, B (in
Prep. of Potassium. the first of the accompanying figures), and the
other, p (corresponding to E in the first figure), to allow the
insertion of an iron wire to remove the obstructions that will
occasionally collect in the gun-barrel leading from the iron bottle.
A small opening is also made for this purpose in the partition
of the receiver, N.
During the operation much incondensible gaseous matter passes
over and escapes by a tube of glass (shown in the first figure)
provided for the purpose; and as it is necessary that the receiver
should be kept cold, a small stream of cold water is made to fall
upon it constantly, which is prevented from entering the lower
part, M, by a rim of metal passing round it, as shown in the
figures. The tubulure, p, is to be kept closed by a cork, except as
it is necessary to remove it for a moment to insert the iron wire,
when obstructions occur in the gun-barrel.
The potassium, after the action has ceased, will be found in
irregular masses in the naphtha at the bottom of the receiver;
QUEsTIoN.-Where will the potassium be found?




BINA.RY COMPOUNDS OF POTASSIUM.                301
but it will not be pure. It is now collected in a bag of cloth,
through which it is squeezed by compressing the bag with pincers
while held in a cup of warm naphtha.  If necessary, it may be
further distilled in a small iron retort.
357. Properties.-Potassium is a solid, in color and lustre
much resembling lead. At 1500 it melts, and at a dull red heat
may be distilled in vessels void of gases capable of combining with
it. It is the lightest metal known, having a density of only
0'865, and floats upon the surface of water.  At ordinary temperatures it is soft like wax, but at 320 it becomes quite hard.
But its most characteristic property is its affinity for oxygen;
when thrown upon the surface of water it absorbs
the oxygen so rapidly as to be inflamed, and burns
with a beautiful rose-colored flame.  In the open
air, the freshly-cut surface  absorbs oxygen so           li
rapidly as to be tarnished instantly; and heated  
even in carbonic acid (303), it takes fire and burns    Combustion of
by absorbing the oxygen.  In consequence of its  Potassium upon
affinity for oxygen it can be preserved only in
tubes hermetically sealed, or under some liquid that does not
contain oxygen, as naphtha, which is found to answer the purpose well.
Binar-y Compounds of Potassium.
358. Protoxide of Potassium-KO; eq., (39.2 + 8 -) 47 2.
-This is potash, or pptassa, and is always formed when the
metal is exposed in the open air, or oxygen gas, or acted on by
water.  In the latter case, the potash formed is immediately dissolved by the water, as will be found by applying the usual tests.
Pure potash is a white, inodorous substance, with a pungent,
caustic taste, and very soluble in water.  It absorbs carbonic acid
QuvETIONS.-357. Describe some of the properties of potassium. Wlhat
is said of its affinity for oxygen? What is the effect when a small piece
of it is thrown upon water?  How is it preserved?  Why is naphtba
selected for this purpose? 358. What is the common name for protoxido
of potassium? Describe potassa? Does it usually contain water?
26




302          BINARY COMPOUNDS OF POTASSIUM.
and water rapidly from  the air, and should therefore be kept in
close bottles.
When prepared by the slow oxydation of potassium in dry air
or oxygen gas it is anhydrous, but when formed by the oxydation
of the metal in water, or from any of its salts, it is always in the
state of a hydrate.
Potash forms with water two compounds, the monohydrate,
KO,HO, and the pentahydrate, KO,5HO; the former of which
is the caustic potash of commerce.  To prepare it, pearlash (carbonate of potash) is dissolved in ten times its own weight of
water, and half its weight of recently-slaked lime mingled with
it, in successive portions, and the whole boiled briskly for half an
hour.  It is then allowed to settle, and the clear liquid is drawn
off. The lime, in this process, decomposes the carbonate of
potassa, and forms. insoluble carbonate of lime, which settles to
the bottom; and the clear liquid contains
nearly pure potassa.  This may be preserved for use in well-closed bottles, or it
b~ieCI~    II   may be evaporated to dryness in a vessel
L    of such a form  as not to allow any colnsiderable accession of air.  To insure per- -  C  feet purity, it must be again dissolved in
absolute alcohol, and the solution filtered al d
evaporated as before. The hydrate is soluble
in alcohol, which is not the case with sulphate of potash, usually present in pearlash,
or carbonate, portions of which may have
escaped decomposition by the lime..
359. To prevent the absorption of carbonic acid from the air while filtering, an
)]}- - v-      apparatus like that figured in the margin is
used.  It consists of two vessels, A and D,
of equal capacity, and connected with each
Filtering Apparatus.    other.  The throat of the upper vessel or
QUEsTIoNs. -What hydrates of potash are mentioned?  How  is
pure caustic potash prepared from the carbonate?  Why should it be
dissolved in alcohol and filtered?  359. Describe the mode of filtering
the alcoholic solution.




BINARY COMPOUNDS OF POTASSIUM.               303
funnel, A, is obstructed by a piece of coarse linen loosely rolled up,
and not pressed down into the pipe through which the solution is
filtered.  The pipe, c, extending from e to b, serves for the air to
pass from the lower vessel to the upper; and the operation goes
quietly on, free from contact with the atmosphere, except the little
contained within the apparatus at the beginning of the process.
Solution of potassa is highly caustic, and its taste intensely
acrid.  It possesses alkaline properties in an eminent degree,
converting the vegetable blue colors to green, and neutralizing
the strongest acids.  It absorbs carbonic acid gas rapidly, and is
consequently employed for withdrawing that substance from gaseous mixtures.
Potassa is employed as a reagent in detecting the presence of
bodies, and in separating them from each other. The solid hydrate,
owing to its strong affinity for water, is used for depriving gases of
hygrometric moisture.
Caustic potash attacks all animal substances with avidity, and
neutralizes all acids.  With the fats and oils it combines readily,
forming the well-known compound called soap, of which we shall
have occasion to speak again hereafter.  This property is characteristic of all the alkalies.
The pentahydrate possesses no special interest.
360. Peroxide of Potassium, K0,, as is shown by the formula,
is a teroxide. It is of a dull yellow color, and is formed by burning potassium  in an excess of dry oxygen gas.  Thrown into
walter, it gives up two-thirds of its oxygen, and solution of caustic
potash is formed.
361. Chloride of Potassium, KC1, is readily obtained by neutralizing carbonate of potash, KO, C02, by hydrochloric acid.
The reactions which take place have already (347) been explained.
Like common salt (chloride of sodium), it crystalizes in cubes,
which are anhydrous.
Iodide of Potassium, KI, is formed by heating potassium  in
contact with iodine; or, by digesting iodine in a hot soluQUESTIONS. —What is said of the action of potash upon animal substances?  What does it form with the fats and oils?  360. What is
peroxide of potassium?  361. What is chloride of potassium?  How is
iodide- of potassium formed?




304                 SALTS OF POTASH.
tion of caustic potash, and exposing the mass, when dry, to a red
heat, and subsequently crystalizing from  solution in water or
alcohol. It is a white solid, very soluble in water, usually seen
crystalized in cubes, and is often sold under the name of qhydrio(ca te of potash.
Solution of iodide of potassium has the property of dissolving
iodine, and becomes of a brown color; it also dissolves other
iodides, as the iodides of mercury.
Iodide of potassium is much used in medicine, and in certain
photographic processes.
Bromide, KBr, and floride, KF, of potassium, like the chloride and
iodide, crystalize in cubes.
362. Sulphides of Potassium.-There are at least five sulphides of potassium, KS, KS2, KS3, KS4, and KS5, which, as shown by their formulse,
contain, respectively, 1, 2, 3, 4, and 5 equivalents of sulphur in combination with 1 equivalent of the metal.
The most important of these is the pentasidlplhide, KS5, which is easily
prepared by heating gently a mixture of carbonate of potash and sulphur, or by boiling a solution of caustic potash with an excess of sulphur.
It is a yellowish-brown solid, very soluble in water, and is used in
medicine, especially in cutaneous diseases, under the name of hepoar
szlllhuris, or liver of szulphur. The tersulphide is also used in the same
inanner.
Salts of Potash.
363. Carbonate of Potash,. KO,CO,.-Carbonate of potash, or
pearlash, is prepared for the purposes of commerce by leaching
the ashes of forest trees, and evaporating the lye thus obtained to
dryness, and then heating the dry mass to redness for a time in
open vessels, to burn out the combustible matter which is contained in it.  As thus procured, it is a white spongy mass, very
caustic to the taste, and absorbs moisture rapidly from the air, so
that it must be kept in close vessels.  It is very soluble in water,
but insoluble in alcohol, and is easily fused at a red heat.  That
found in commerce is very impure, being mixed with silica and
other substances.  It is manufactured in large quantities in the
United States, in the Canadas, and in Russia.
QuEsTIoNs.-What use is made of iodide of potassium?  362. What is
said of the sulphides of potassium?  363. What is pearlushl    How is it
prepared? Describe it. What countries furnish it in large quantities?




SALTS OF POTAsII.                        305
If pure carbonate of potash is required, as is often the case in
the laboratory, the tartrate (cream of tartar) or oxylate is heated
to redness in the open air, treating the charred mass thus formed
with warm water, and filtering. The solution may then be evaporated to dryness, if the dry salt is desired.
By slowly evaporating a solution of carbonate of potash the
salt may be crystalized, though not without difficulty.
The article sold as potash is the same as pearlash, except that
it is not subjected to the last process of calcination.  It is a darkcolored mass, and contains much caustic potash, as well as carbonate, and is used extensively for the manufacture of soap.
Pearlash is employed in the manufacture of glass and paints, and
for various other purposes.
364. Bicarbonate of Potash, KO,2C0,. -This salt is prepared by subjecting pearlash in solution, for some time, to an
atmosphere of carbonic acid, which is absorbed in large quantity.
Though less caustic to the taste than pearlash, it is still highly alkaline. It is less soluble also than pearlash, and less deliquescent.
It may be obtained in crystals with less difficulty than the carbonate, and the crystals contain a single equivalent of water.
Their formula may therefore be written KO,CO, + 11HO,CO2,
that is, the salt may be considered as a double carbonate of potash
and water.
This salt is extensively used under the name of salwtratus.
365. Nitrate of Potash, KO,NO,. —This salt, the saltpetre,
or nitre, of commerce, is formed, in this country, by decomposing
the nitrate of lime% which abounds in the caverns of some of the
Western States, by carbonate of potash, and filtering and evaporating the solution thus obtained.. In some parts of Europe it
is prepared in nitre-beds, which are made by heaping together
old mortar, refuse animal matter, wood-ashes, &c., in which it
gradually forms by the action of the atmosphere.  The mass is
QUEsrTIONS.-How may pure carbonate of potash be prepared?  What
is, the article known in commerce as potash? 364. How is bicarbonate
of potash prepared? May it be obtained in crystals? By what name is
it familiarly known?  365. By what names is nitrate of potash known in
cnmmerce? IHow is it prepared in this country?  How in some parts
of Europe?
26*




306                SAL TS OF POTASH.
lixiviated with hot water; and the solution by evaporation yields
crude nitre.
Nitrate of potash is usually seen in long six-sided prisms. It
is a colorless salt, of a cooling saline taste, and is very soluble in
water.  Its density is about 1'93.  Heated to redness, it first
melts and is then decomposed, giving off, at first, pure oxygen,
and afterwards, if the heat is increased, nitrogen and nitric oxide.
Thrown on burning charcoal it is decomposed, producing violent
deflagration, by which it may always be distinguished from sulphate of soda, for which it has sometimes been mistaken.  It is a
powerful antiseptic, and is used with common salt in the preservation of meat and other substances.
But the chief use of nitre in the arts is in the manufacture
of gunpow(der, which is composed of nitre six parts, and charcoal
and sulphur each one part, the whole being moistened and
thoroughly ground together, and subsequently pressed and granulated. When fired, the nitre, by its decomposition, furnishes
oxygen, which combines the carbon, forming carbonic acid, the
sulphur at the same time uniting with the potassa.  The action
of gunpowder depends upon its generating, when decomposed, a
large quantity of gaseous matter at a high temperature.  The
gases are chiefly nitrogen and carbonic acid, which, at the moment
of explosion, occupy more than 1000 times the volume of the
powder from which they are formed.  The formation of the gases
is not instantaneous, but occupies a certain time, and the ball is
forced from  the gun with a velocity due to the ultimate effect
of the whole.
When made for particular purposes, the proportion of the ingredients is sometimes considerably varied.  We may, in fact, consider gunpowder as of three kinds, which may be called sporting
powder, war powder, and blasting powder; the foi'mer of which
is required to detonate more rapidly and violently than either
of the others. The composition of the three kinds is usually
about as follows:QUESTIONS.-Describe nitrate of potash? How does heat affect it?
What is the effect when it is thrown upon burning charcoal?  What
uses are made of it?  What is the composition of gunpowder.   What are
the chemical reactions that take place when it is fired? Upon what does
the action of gunpowder depend.? What different kinds are mentioned?




SALTS  OF  POTASH.                            307
For sporting powder......... Nitre.........769 parts.
Sulphur...... 9-6  "
Carbon.......135   "
1000   "
For war powder...............Nitre........ 70 parts,
Sulphur......12'5   "
Carbon.......12-5 
100'0 "
For blasting powder......... Nitre.........620 parts.
Sulphur......20'0   "
Carbon.......180   "
1000   "
Theoretically, it would seem  that the best proportion would be 1
equivalent of nitre, 1 equivalent of sulphur, and 3 equivalents of carbon.
T hus,
iO,NO5 + S + 3C = KS + N + 3CO2.
The proportion by weight of the several ingredients would then be as
follows:In 100 parts.
Nitre, 1 equivalent......... 101.2..... 74.85
Sulphur, I 1........ 16.0......11.84
Carbon, 3  "......... 18'0........ 13'31
100.00
This is very nearly the same proportion as that given for war powder
above; but the reactions which take place in the conmbustion of the
powder not being necessarily the same precisely as indicated in the above
iformula, nor, indeed, in any two cases with the same powder, considerable variation in the proportion of the ingredients may be allowed.  For
the best powder, the materials should be freed from all impurities before
using them.
366. The comparative force of different specimens of gunpowder, or
the initial velocity a given quantity of it will communicate to a ball of a
given weight, is determined by several modes, only one of which, called
the ballistic pendulum (see figure on next page), will be described, and
that very briefly.  It is composed of two parts, the ballistic pendulnzm, P,
and the penzdzulum-3yzn, G, the former of which, P, consists of a conical box,
containing a mass of lead, suspended by an iron rod, in the manner of a
QUESTIONS.-'lTWhat is the difference in the composition of the three
kinds of gunpowder?  Is the composition of gunpowder exactly the same
as would seem to be required by the chemical formula?  366. How is
the comparative force exerted by different kinds of gunpowder, when
fi'ed, determined?  Describe the ballistic pendulum.




3O8                 SSALTS  OF POTASH.
pendulum, from some
very firm support. G
is a common gun-barrel supported in an
frame, which is also
suspended in the manner of a pendulum,
the gun-barrel, when
hanging freely, being
made to point to the
mass of lead. At m n
and op are graduated
p     arcs, each having at1,?/ I J.     o1   tached to it a slider,
which is carried along
with the movement of
P,t$ __  a f         the rod to the furthest
--- _____- 3point to which it oscillates, but does not reBallistic Pendulum.               t
turn with it.
The gun-barrel is now charged with the proper quantity of the powder
to be tested, and the ball placed in it, and fired; and the ball being
projected into the mass of lead causes it to move to the left (as the apparatus is represented in the figure) to a certain distance, which will be
exactly shown by the slide upon the graduated arc, m n. At the same
time the gun-barrel will recoil to the right, as will be shown by the slide
upon op. The initial velocity of the ball may now be calculated from
the distance either slide has traversed, by means of the proper mathemnatical formulae.
To insure accuracy, attention must be paid to several particulars in
the adjustment of the apparatus, which are not here alluded to.
367. Sulphate of Potash, KO,S03.-This salt is easily prepared artificially by neutralizing carbonate of potassa with sulphuric acid; and it is procured abundantly by neutralizing with
carbonate of potassa the residue of the operation for preparing
nitric acid (221).  Its taste is saline and bitter.  It generally
crystalizes in six-sided prisms, bounded by pyramids with six
sides, but its primary form is the right rhoumbic prism. The
crystals contain no water of crystalization, and suffer no change
by exposure to the air.  They decrepitate when heated; and enter
into fusion at a red heat.  They require 16 times their weight
of water at 60~, and 5 of boiling water for solution.
QuESTIONS.-367. How may sulphate of potash be prepared artificially? What are some of its properties?




SALTS  OF POTASIH.                       309
368. Bisulphate of Potassa, KO,2SO,, is easily formed by exposing the neutral sulphate with half its weight of strong sulphuric
acid to a heat just below redness, in a platinum crucible, until acid
fumes cease to escape.  It has a strong sour taste, and reddens
litmus paper, and in crystals -may be considered a double sulphate
of potassa and water, KO,SO3+ HO,SO,. It is much more soluble
than the neutral sulphate, requiring for solution only twice its
weight of water at 600, and less than an equal weight at 212~.
It is resolved by heat into sulphuric acid and the neutral sulphate.
369. Chlorate of Potash, KO,C105.-This salt is formed, together with chloride of potassium, by passing a current of chlorine
through a strong solution of pearlash.   The reactions are as
follows:6KO,C02 + 6C1 = 5KCl + KO,C105 + 6CO,.
The carbonic acid escapes during the process, and the chloride
of potassium being very soluble remains in solution, while the
chlorate crystalizes in shining white scales.
The chlorine, before entering the potash solution, should be
made to pass through a three-necked bottle containing a little
Preparation of KO,C10.
water, to separate any sulphuric acid which may pass over with
it. The proper arrangement is represented in the figure.
QUESTroNs. — 368. How is bisulphate of potash formed?  369. How
is chlorate of potash formed?  Describe the reactions that take place.




310                        SODIUM.
Its taste is not unlike that of nitre, but it is much less soluble
than that salt.  Heated moderately, it melts, and at a red heat is
decomposed, giving up the whole of its oxygen.  Thrown on
burning charcoal, it deflagrates like nitre, but more energetically.
A few of the crystals, wrapped in tin-foil, with a piece of phosphorus, or a little sulphur, explode violently by a blow from the
hammer. It was formerly used in the manufacture of Lucifer
matches, and has been substituted for nitre in gunpowder; which,
however, when thus prepared, is liable to explode from causes so
slight that its manufacture is dangerous.
The silicates of potash will be described hereafter.
370. Sulphur-Salts of Potassiumn.-Protosulphide of potassium, as the
electro-positive element, combines with many other electro-negative sulphicles, forming true salts (345), but we shall here describe only the
following two:Hydrosulphate of Potassium, or, more properly, the hydrosulphato of
sulphide of potassium, KS,HS, is prepared by passing a current of hydrosulphuric acid (263) through a solution of potash.  When the solution is
concentrated the salt may be obtained in crystals.
Carbosulphate of potassium, KS,CS2, may also be crystalized.  It is
prepared by pouring bisulphide of carbon into an alcoholic solution of
protosulphide of potassium.
SODI U M.
Symbot  Na (Natron); Elquivalent, 23; Density, 0'972.
371. History and Preparation.-Sodium  was discovered in
1807, by Davy, a few days after the discovery of potassium.
The first portions of it were obtained by means of galvanism;
but it may be procured in much larger quantity by chemical processes, precisely similar to those just described for obtaining
potassium. Its preparation is less difficult than that of potassium.
QUESTIONS.-Describe the properties of chlorate of potash. What is
the effect when it is thrown on burning charcoal? What use has been
made of it? Why may it not be used in the formation of gunpowder?
370. How is hydrosulphate of potassium  formed?  What is its composition?  What is the composition of carbosulphate of potassium?
371. tHow is sodium prepared'?




BINARY  COMPOUNDS OF SODIUIAM.                     311
372. Properties.-Sodium  has a strong metallic lustre and in
color is very analogous to silver.  It is so soft at common ternperatures,. that it may be formed into leaves by the pressure
of the fingers.
Sodium soon tarnishes on exposure to the air, though less
rapidly than potassium.  Like that metal it is instantly oxydized
by water, hydrogen gas in temporary union with a little sodium
being disengaged. When thrown on cold water, it swims on its
surface and is rapidly oxydized, though in general without inflaming; but with hot water it scintillates, or even takes fire, and
burns with a beautiful yellow flame, which readily distinguishes it
from potassium.
By throwing two pieces, one of sodium and another of potassium, at the same time, into a vessel of water, both will usually be
inflamed; and the characteristic colors of their flames will be
seen together.
Sodium  is preserved under naphtha in the same manner as
potassium.
Binary Compounds of Sodium.
373. Protoxide of Sodium-NaO; eq., (23 + 8 =) 31.-This
compound, usually called soda, is formed by the oxydation of sodium,
as potassa is from potassium. With water it forms a solid hydrate,
which is easily fusible, and very soluble both in water and alcohol.
It is a powerful alkali, and very similar in all its properties to
potassa.  Hydrate of soda is prepared from the carbonate in the
same manner as the hydrate of potash.  The hydrate is known as
caustic soda;-it contains a single equivalent of water, and its
formula is therefore NaO,HO.
Peroxide of Sodium, NaO,, is formed by burning sodium in dry air or
oxygen gas.
QursTroNs.-372. Describe the properties of sodium.  Whjat is the
effect when it is thrown upon water? How is it preserved? 373. What
is soda? Describe its properties. By what name is the hydralte of solda
known? What is peroxide of sodium?




312      BINARY  COMPOUNDS OF SODIUM.
374. Chloride of Sodium-NaCl; eq., (23 + 35'4 -) 584.This is the common salt of commerce.  It may be formed by
burning sodium in chlorine, but is obtained in great abundance
as a solid deposit, called rock salt, in various parts of the world,
as in England, Poland, and at Abingdon in Virginia; anrd in
solution in the waters of brine springs, which abound in New
York, Pennsylvania, Virginia, Kentucky, Ohio, and other States,
as well as in other countries.  Sea-water contains about 2'7 per
cent. of this substance, while the water of the great salt lake in
Utah Territory contains about 20 per cent. Around this latter
body of water are plains, many miles in extent, which, in the dry
season, are covered with incrustations of very pure salt to the
depth of more than half an inch.  In the rainy season it is more
or less dissolved.
Rock salt is sometimes mined of sufficient purity for use, and
requires only to be pulverized; but more frequently it is mixed
with clay and oxide of iron, and must then be dissolved, and the
pure liquid drawn off and evaporated.
In warm countries, as on the coast of Portugal, in the south
of France, and the West India Islands, this substance is obtained
by the spontaneous evaporation of sea-water, which is allowed, on
the rise of the tide, to flow into shallow basins, being passed
from one to another, as it becomes more concentrated; and
finally, the evaporation is finished by means of artificial heat.
In cold countries, as on the borders of the White Sea, the process is commenced in a very different manner:-the sea-water is
exposed to the cold atmosphere, by which a large part of the
water is separated in the form of ice, and the remaining liquid
portion is drawn off and evaporated.
Pure chloride of sodium has an agreeably saline taste.  It fuses
at a red heat, and becomes a transparent brittle mass on cooling.
It deliquesces slightly in a moist atmosphere, but undergoes no
change when the air is dry.  In pure alcohol it is insoluble.  It
QUESTIONS.-374. What is the common name for chloride of sodium?
Where is it found in the solid state? What are brine springs? What is
the proportion of it contained in sea-water?  In the water of the great
salt lake in Utah Territory?  How is this substance procured in celrtain
warm countries?  I-ow in certain cold countries? Describe some of the
properties of common salt?




BINARY COMPOUNDS OF SODIUM.    318
requires twice and a half its weight of water at 600 for solution,
and its solubility is not increased by heat. It crystallizes in
cubes, which are anhydrous, and have a density of about 2'13
when its solution is slowly evaporated in the
open air hopper-shacpecd crystals, as figured
in the margin, are of common occurrence. 
Their formation may be explained as follows:-first a small cubical crystal forms at  Hoppe       Cysta
the surface of the solution, which tends to
sink and depress the surface, as shown in the figure A.  Soon
AI B
Cryst. Common Salt.
other small crystals form and attach themselves to the first one
at its four upper horizontal edges, by which it is a little more depressed, as represented in the figure B;       a
a further addition in the same manner
causes a further depression, as seen in C,:
and so on.                                   Cryst. Common Salt.
A saturated solution of common salt does not freeze even at 0~
but hydrated crystals are formed which have the formula, NaCl +
4HO.  It fuses at a red heat, and may even be sublimed without
change.
The uses of this substance are well known.  Besides the ordinary purposes to which it is applied, in preserving meat from
putrefaction, and in seasoning food, it is used extensively in the
arts, in glazing pottery-ware, in the manufacture of bleachingsalt, carbonate of soda, hydrochloric acid, &c.
The name, salt (Lat., sal), was originally given to this sttih
stance alone, but was subsequently extended to an immense class
of compounds which have been known as salts.  By our present
QuESTIONs.-Describe the mode in which hopper-formed crystals are
sometimes produced. What are the uses of this substance?  Does it
belong to the family of salts, according to the definition of the word
which we have adopted?
27




314                   SAL TS OF  SODA.
technical arrangement (347), it is entirely excluded from  the
class.
Sodium forms definite compounds with iodine, bronmine,fiuor ine,
su7phur, &c., but they are not described in this work.
Salts of Soda.
375. Sulphate of Soda, NaO,SO. —Sulphate of soda, or Glauw
ber's salt, is sometimes found native in dry situations, but more
frequently in solution in the waters of mineral springs.  It is also
obtained in the manufacture of hydrochloric acid (236).  It was
first made known by Glauber, from whom it received its name,
although he himself called it sal-mirabile.   It has a cooling,
saline, and somewhat bitter taste; and is very soluble in water at
a temperature 910 or 92~, but less so in water that is very cold
or very hot (350).  The crystals of this salt usually contain more
than half their weight of water of crystalization, which escapes
when they are exposed to the open air, and they crumble into a
white powder. Their proper formula is NaO,SO,+1011HO. The
water therefore constitutes nearly 56 per cent., as will be found
by making the calculation.
Sulphate of soda is used in medicine as a cathartic, and for
the preparation of the carbonates of soda.
Biszllphate of Soda may be obtained in crystals which have the formula,
NaO,2S03 + 3HO. Deprived of its water of crystalization, it may be
used in preparing anhydrous S03 (259).
376. Hyposulphite of Soda, NaO,S202.-This salt, which is much used
in the daguerreotype process, for removing the sensitive coating from the
silver plate, after being tnaken from the mercurial vapor bath, is prepared
by first passing a current of sulphurous acid gas through a solution of carIbonate of soda, to form sulphite of soda, and then dissolving sulphur in a
concentrated hot solution of the sulphite.
It mally be obtained in crystals, which, according to some, contain 5,
and according to others, 10 equivalents of water.  It is also called
dilhionale of soda.
QUESTIONs.-375. What is Glauber's salt?  What are some of its proper ties?  What is said of its water of crystalization?  What use is
made of it? 376. What use is made of hyposulphite of soda?




SALTS  OF SODA.                        315
377. Carbonate of Soda, NaO,CO2.-The carbonate of soda
of commerce was formerly obtained by lixiviating the ashes of
sea-weeds, in the same manner as the carbonate of potassa is
obtained from the ashes of land-plants. But it is now manufactured altogether from  common salt, which is first converted
into sulphate of soda by sulphuric acid, and then the sulphate,
mixed with charcoal and carbonate of lime, is heated intensely in
a wind-furnace.
The materials, which consist of about 2 parts of the anhydrous
sulphate, 2 parts of chalk (carbonate of limle), and 1 of charcoal,
are well ground together, and introduced upon the hearth, H IIH
of a reverbatory furnace, similar    /
to that represented in section in  
the figure; and by continued action
of the heat, carbonate of soda,
NaO,CO2, oxysulphide of calcium,
CaS,CaO, and carbonic oxide, CO,
are formed: —the latter compound                     "      2
being gaseous, of course passes off.
The oxysulphide of calcium being
o    Preparation of Carbonate of Soda.
insoluble in water, it is now only
necessary to digest the black mass which comes from the furnace
in warm water, and filter, and a solution of carbonate of soda is
obtained. This is now evaporated to dryness. It may be obtained
in crystals, which always contain much water of crystalization,
and effloresce in dry air.  It is the sal soda of commerce.
The mixture as taken from  the furnace is the soda ash, or
British barilla of commerce, and has been sometimes used as a
manure.
Carbonate of soda is extensively.used in the manufacture of
glass and hard soap, and for other purposes.
Sesquicarbonats of Soda, 2NaO,8CO2, called trona, is found in the
waters of certain lakes in Egypt, in Hungary, and in this country in
springs among the Rocky Mountains.
QuEsTIoNs. —877. From what was carbonate of soda formerly obtainedcl 
low is it now manufactured?  Describe the process.




316                  SALTS  OF  SODA.
378. Bicarbonuate of Soda, NaO,2CO,.-This salt is formed by
exposing the carbonate in solution to an atmosphere of carbonic acid,
in the same manner as the bicarbonate of potash.  Like the corresponding salt of potash, it always contains one atom of water,
and may be considered a double carbonate of soda and water,
according to the formula, NaOCO02+IHO,CO2.  It is often used
by bakers as a substitute for sal-meratus.
379. Biborate of Soda, NaO,2BO3.-This salt occurs in solution in the waters of certain lakes in Thibet and the East Indies,
from  which it is obtained by evaporation, and was formerly imported into this country and England under the name of tincal.
When refined, by solution and recrystalization, it is sold as borax.,
a substance well known for its extensive use in the arts in various
metallurgic operations.  At present, most of the borax of commerce is obtained from Tuscany, where it is prepared by adding
carbonate of soda to the native boracic acid (326) of the hot
springs which abound in an extensive volcanic district of that
country.  To obtain it pure, several recrystalizations are required.
Ordinary borax crystalizes in right rhombic prisms, which contain 10 equivalents of water; but when crystalized from  a hot
solution the crystals are octahedrons, and contain only 5 atoms
of water.
When borax is heated, it first loses its water of crystalization,
which causes it to froth up very much; and at a red heat fuses
into a clear transparent liquid, which on cooling has the appearance of glass.  At high temperatures, it dissolves most of the
metallic oxides, and becomes colored.
Borax is used as a flux in metallurgic operations, in the pree
paration of certain kinds of glass, and in medicine.
380. Nitrate of Soda, NaO,NO,, resembles nitrate of potassa
in many of its properties, but cannot be substituted for it in the
manufacture of gunpowder, because of its tendency to absorb
QUEsTIONs.-378. What is bicarbonate of soda?  What use is made
of it?  379. Where is biborate of soda obtained?  What is it often
called?  Where is most of the borax of commerce obtained at the present time? What use is made of it?  380. For what is nitrate of soda
used?




SALTS OF SODA.                         317
moisture from  the atmosphere.  It is used instead of nitrate of
potash in the preparation of nitric acid, and sometimes as a
manure.
381. Phosphates of Soda. —Phosphoric acid forms with soda
(and the bases) three series of salts, viz., tribasic or ordlinary
phosphates, bibasic or 2pyropthosphates, and monobas-ic or metna>phosp2hates, corresponding to the three states (282) of the acid.
I. Tribasic Phosphate of Socta.-Of this there are three varieties, viz.:  1. The salt, 3NaO,PO,.  2. The salt, (2NaO +110) PO.  3. The salt, (NaO  -2HO) PO5.  The three varieties
are tribasic, but the base of the first consists of 3 eq. of soda; the
base of the second of 2 eq. of soda and 1 eq. of water; the base
of the third of 1 eq. of soda and 2 eq. of water. The water serving
as base in such salts is called basic water.
The first two varieties usually crystalize with 24 eq. of water,
and the third with 2 eq. of water.. If heated, they readily give
up their water of crystalization, but a red heat is required to
expel the basic water. All of them in solution give a yellow
precipitate, 3AgO,PO,, with solution of nitrate of silver.
II. Bibasic Phosphate of Soda-PJyrop2hos2phate of Socla.This compound furnishes two varieties, viz., 1. The salt, 2NaO,PO5;
2. The salt, (NaO + HO) PO,.  Both varieties are bibasic, but; the
base of the first consists of 2 eq. of soda, and that of the second of
I eq. of soda and 1 eq. of water.  Bibasic phosphate of soda
crystalizes with 10 eq. of water; — the solution of both varieties
gives, with nitrate of silver, a white precipitate, 2AgO,PO,.
III. lllonobasic Phosphate of Sodla-JMetaphosphate of Socda
-NNaO,PO5.-This phosphate in solution gives a white precipitate
with solution of nitrate of silver, AgO,PO,; but its composition,
it will be observed, differs from that procured from the bibasic
phosphate.  Solution of this phosphate also has the property of
QUEsTIONS.-381. What is said of the salts formed with soda by phosphoric acid?  What varieties of tribasic phosphate of soda are there?
How may they be tested when in solution? What varieties of bibasic
phosphate of soda are there? What is said of the precipitate they give
with nitrate of silver? What is metaphosphate of soda?
27*




318                         LIT   I U M.
coagulating the whites of eggs, an effect not produced by the
other phosphates.
For the methods of preparing these varieties and sub-varieties
of phosphate of soda, the inquiring student will consult larger
works on this science, especially the excellent one of legnault;
the object of the present work not permitting so much minute
detail.
With other bases phosphoric acid probably forms similar series
of salts, but the subject has not been fully investigaged.
382. Characteristics of Potash and Soda Salts. —All the salts of potash
and soda that are soluble are distinguished from  other metallic salts,
except the salts of lithia, which are very rare, by giving no precipitate
with solutions of the alkaline carbonates.  It is therefore sufficient,
practically, to be able to distinguish between these two classes of salts;
for which the following tests will suffice.
With tartaric acid potassa forms a sparingly soluble salt, which, if the
solution is moderately concentrated, appears as a white precipitate; but
with soda no precipitate is formed, as the corresponding salt of soda is
very sol-uble.
With potash a strong solution of chloride of platinum  forms a yellow
precipitate, the double chloride of potassium and platinum, which becomes more copious by the addition of alcohol; but in the same circumstances no precipitate is formed by the salts of soda, because of the
solubility of the double chloride of platinum and sodium.
LIT HI U M..yqnbol, L; Equivalent,   6 4; Density, -?
383. History, Etc. -Lithium  is a very rare substance, and is found
only in a few minerals, as spod2imenze, and the variety of mica called
lepidolite.  It is obtained from these in combination with oxygen as the
protoxide, lithic.  From this the metal may be procured with some difficulty by means of galvanism.  It is a white metal, like sodium.  The
protoxide, lithia, is a powerful alkali, like potash or soda, but is less
soluble   The name is from the Greek, lithos, a stone, in allusion to the
source from which it is obtained.
The salts of lithia, heated before the blowpipe, give a red tinge to the
flame.
QusETIoNs. —382. How are the soluble salts of potash and soda distinguished froml other salts?   Describe the mode of distinguishing a
soluble salt of potash from one of soda by means of tartaric acid.  By
means of solution of chloride of platinum.  383. What is said of lithium? 
From what is the name derived?




AMIMONIUM.                         319
Ammonium.  (Aot Isolable.)
384. History, Etc. —This name is given to a supposed com-.
pound of nitrogen and hydrogen, NH4, which has never yet been
obtained in a separate. state, but is believed by many to enter
into the composition of most of the ammoniacal compounds, and
to possess in some respects the characters of a metal.  Its symbol
is written NH4, or Am.
When strong aqua ammonise (225), in contact with a little
mercury, which is connected with the negative electrode of the
galvanic battery, is subjected to-the action of a strong electrical
current, oxygen is liberated at the positive electrode and the mercury increases very much in volume, and becomes less fluid,
having the consistency of butter or soft lard, but still retains
perfectly its metallic lustre.  This has very much the character
of an amalgam; and we may suppose that under the influence
of the current, ammonium, NH4 (equal to NH, + H) has been
formed from the ammonia and the hydrogen of the water, and at
once united with the mercury, the oxygen escaping at the other
electrode.
The same compound may also be obtained simply by combining a little potassium or sodium with 50 or 100 times its
weight of mercury, and pouring on it a strong solution of sal
ummoniac,  NH,,HC1.  In this case the reaction seems to be
KHg + NH3,C1 -- KCl + NH4,Hg.
This compound, called ammoniacal anal7yabn, when removed
from the solution in which it was formed, rapidly undergoes
spontaneous decomposition, yielding ammonia and hydrogen in the
proportion of 2 volumes of the former and 1 volume of the latter.
After a little time the mercury alone is found entirely unchanged.
QUESTIONS. —384. What is the compound to which the name ammonium is given? Has it been obtained in a separate state? What is the
mode of preparing ammoniacal amalgam by the use of the galvanic battery? Explain the reactions by which we may suppose the new substance to be produced. Describe the mode of producing it by the use
of sal ammoniac in solution. What are the reactions that appear to take
place? What is the effect when the amalgam is removeld from the solution? What are obtained when it dcoomposes?




320         BINARY COMPOUNDS OF AMMONIUM.
If this amalgam is subjected to a temperature of 320, it crystalizes in cubes, and its decomposition is retarded.
Although this compound, NH,4, which has received the name
of ammonium, has not been obtained in a separate state, its
existence in combination with other bodies would seem to be
established; and also its peculiar metallic character.  It is capable
of replacing potassium and sodium in combination, and is therefore isomorphous with them.
Ammonia, NH,3, has heretofore (224) been described.  It has
been called volatile alkali, because of its reactions with other
substances, and especially with the acids, being the same as those
of the other alkalies, the protoxides of potassium, sodium, and
lithium. We introduce the subject again for the purpose of
describing some of its more important compounds, which we
shall do according to this ammonium  theory, as it is called;
because it affords us, in the present state of our knowledge, the
most simple and lucid view of this important class of bodies that
can be presented. But, at the same time, it should always be
kept in mind that the existence of ammonium, NH,, even in combination with other substances, is not to be considered as fully
determined.
Binary Compounds of Ammonium.
385. Protoxide of Ammonium, NH40, or AmO.-A.s is the
case with ammonium, the existence of this compound is hypothetical. But all the ammonia salts of oxygen acids, contain an
atom of water in their composition, which appears to be essential
to their existence. This atom of water, combined with the ammonia, NH3, forms the compound in question, protoxide of ammonium, NH40, which unites with the acid to form the salt. Thus,
the composition of nitrate of ammonia, as formerly supposed, is
NH3,NO5,HO, which evidently is the same as NH40,NO,, except
as to the mode of the arrangement of the particles.
QvUETIoNs. —Iow is this amalgam affected by a cold of 320~? What is
said of the relation of ammonium to potassium and sodium? Why has
ammonia been called volatile alkali?  385. What is said of protoxido
ot' ammonium?




SALTS OF AMMONIA.                        321
As ammonium  is isomorphous with potassium and sodium, so
this compound is isomorphous with potash and soda, which it is
capable of replacing in many of their compounds.
386. Chloride of Ammonium, NH4C1.-This is the compound
often called sal-ammonitac, and hydrochlorate of ammonia.  If it
be considered as a proper hydrochlorate of ammonia, its formula
of course will be NHI,,C1.
It may be obtained by neutralizing carbonate of ammonia by
hydrochloric acid; but for use in the arts it is procured from the
liquor obtained in the distillation of bones, in preparing animal
chardlf  and also from that which condenses in the manufacture
of coa -gas.  The latter affords it in large quantities.
Sal-acmmoniac is a white solid, very tough, and difficult to
pulverize, and has a density of about 1'45.  It has a pungent,
saline taste, and is very soluble in water; and sublimes without
fusion at a temperature below redness.  Triturated with recentlyslaked lime, it yields ammonia, which is easily recognised by its
pungent odor. It is used for various purposes in the arts and in
medicine.
Salts of Anmonia.
387. Carbonates of Ammonia.-There are several carbonates
of ammonia.  The one best known is the sal-volatile of the shops,
which is a sesquicarbonate.  It is a semi-transparent solid, which
is very soluble in water, and has the pungent odor of ammonia.
Its composition, on the "ammonium  theory," is 2NH40,3C0,;
but considered without reference to this theory, its formula is
usually written 2NH3,,3CO2+ 2HO. By long exposure to the air
it is converted into a bicarbonate, N1H40,2C02 + H1O.
Besides these, there is also a neutral carbonate of ammonia.
Sulphate of Ammonia, NH40,S0,.-Sulphate of ammonia is
a soluble salt, isomorphous with sulphate of potassa.  It is someQUESTIONS. —Is ammonium isomorphous with potassium and sodium?
386. What is sal-ammoniacc?  How is it obtained?  Describe its properties. 387. What carbonates of ammonia are mentioned?  Describe
sulphate of ammonia.




322        SILICATES OF POTASH AND SODA-GLASS.
times found in the lava of volcanos, and may be formed artificially
by saturating aqua ammonia or solution of carbonate of ammonia
with sulphuric acid. It is sometimes used as a manure.
Nitrate of Ammoniay NH3,N05 + IIO, or, as it is now considered, nitrate of oxide of ammoniulm, NH40,N05, is prepared
by neutralizing nitric acid with ammonia, or its carbonate.  It is
a white salt, very soluble in water, and destitute of any ammoniacal odor. It is used in preparing nitrous oxide (215).
388. Phosphate of Soda and Ammonia, (NaO,N1H40,HO)P(5.-Tlhis is
the compound called microcosmic salt, and much used as a flux in blowpipe operations. Its crystals contain 8 eq. of water of cryst  ion,
vwhich is given up at a very moderate heat; and, at a high tern   ure,
both the basic water and ammonia are expelled, and the very fusible
mnetaphosphate of soda only remains.
It is prepared by dissolving in 2 parts of hot water 6 or 7 parts of phosphlate of soda, and then adding 1 part of sal-ammoniac. On cooling, the
salt in question crystalizes, while chloride of sodium remains in solution.
389. Hydrosullphate of Sulphide of Ammonium, NH4S,HS.-This compound, it will be
observed, is a sulphur salt (345), being composed of two sulphides, sulphides of ammonium and hydrogen. It is prepared by passJ: —-  ing a current of hydrosulphuric acid through
aqua ammoni, which is to be kept cool
during the operation. The apparatus represented in the figure will answer for the
purpose.
I     It is much used in the laboratory as a test
Preparation of NllHS,IIS.   for several of the metals.
Silicates of Potash and Soda- Glass.
390. Silica, or, more properly, silicic acid, combines at high
temperatures with the alkalies and earths apparently in indefinite
proportion, producing compounds which at very high temperatures
are more or less liquid, but at a lower heat have a pasty consistency, and when cold are hard, uncrystaline, and more or less
QuxEsTIONS.-388. What use is made of phosphate of soea and ammonia?  How is it prepared?  389. How is hydrosulphate of sulphide
of aimmonium  prepared? To what class of salts does it belong? 390. Howv
is silica made to combine with the alkalies and earths?  What is said of
the compoun Is produced?




SILICATES OF POTASH AND SODA —  GLASS.             323
transparent. All these compounds are known under the name
of glass.
There are several kinds of glass, all of which are double sili-.
cates of potassa and soda, or one of these with silicate of lime,
lead, magnesia, baryta, alumina or iron, but the proportions are
variable.
Silicic acid has no action upon the bases at ordinary temperatures, but it readily combines with them in a state of fusion, or
with their carbonates; in the latter case of course expelling the
carbonic acid.
391. When silica is fused with 2 or 3 times its own weight
of carbonated potash or soda, a compound is formed which is
soluble in hot water, and has been called soluble glass, or liquor
silicum.  The solution, when applied to wood and other combustible substances, soon dries and forms a transparent coating
which protects them from the air and renders them less combustible
when exposed to great heat.
If the proportions are reversed, and 2 parts of silica and 1 part
of carbonate of potash or soda are used, a proper glass is formed,
which is quite insoluble in water, and nearly all acids.
The proportions of the ingredients in the different varieties
of glass are exceedingly variable, but common window, or crlown
glass, is always a mixture of silicate of potash or soda and lime.
Crystal, or fiint glass, is a silicate of potash or soda and oxide
of lead; it is softer than other kinds, and more fusible and
dense, and therefore better adapted for optical purposes.  When
a thread of it is heated in the flame of a lamp, it is blackened by
the reduction of the oxide of lead.
392. Bohemian glass, which is very infusible, contains only
silicate of potash and lime. It is much used in the manufacture
of chemical apparatus.
The finest kinds of glass are made only of the purest materials;
but impure materials, containing alumina and the oxides of ir(on
and manganese, answer for such glass as that of which green bottles
are made.
QUESTIONS.-What is glass?  391. I-low is soluble glass forlmed?  ()f
what is crystal glass composed? 392. What is said of Bohemian glass?




324       SILICATES OF POTASH AND SODA — GLASS.
Though, as above stated, glass is considered insoluble in water and the
acids, except such as contain fluorine (252), yet certain varieties of it are
sometimes attacked by acids, solutions of the alkalies, or of their car-bonates, and even by pure water, especially at a boiling temperature.
Glass that has been a long time buried in the earth, is sometimes found
with a pearly incrustation upon its surface, in consequence of the separation of its alkalies; and is sometimes quite soft, so as to be cut with a
knife.
All these different varieties of glass have a density varying from 2'4 to
3'7, but glass may be made of a density as high as 5.4.
Enamel, used for various purposes, and especially for watch
and clock faces, is made of silica and potash, or soda. and oxide
of lead, and rendered opake by oxide of tin.
CYolored glass is made by adding to any of the varieties.metallic
oxides, as those of cobalt, copper, manganese, antimony, gold, &c.
A white opake glass, in imitation of porcelain, is made by adding
to the glass when in fusion arsenious acid.
393. Mlanufacture of Glass. -  The  materials for glass are
first to be fused together, at a high temperature,
~ ~          and in such a manner that no impurities from the
smoke of the fire or other source shall be mixed:  with it.  This is done by using pots made of fireclay, and entirely enclosed within the walls or the
furnace, except the projecting mouth.  The figure
Melting Glass. in the margin represents the section of one, with its
opening or mouth towards the left hand. Usually
several are placed in a circle in the same furnace, and heated by
the same fire.
The principal instrument used is an iron tube or pipe, four or
five feet in length;-one end of this
being dipped into the melted glass,
which has now  the consistency of
soft wax, a portion adheres to it, and
Glass Operations av is removed from  the pot.   As its
shape is irregular, it is first rolled
on an iron plate, called a marver (see figure), to give it a cylinQuESTIONS.-Is glass entirely insoluble in water and the acids?  Of
what is enamel made?  How is colored glass formed?  393. Describe
briefly the mode of manufacturing window glass.




SILICATES OF POTASH AND SODA- GLASS.            325
drical form, and is then blown into a pear-shape (as seen in figure
A), by forcing air through the pipe from the lungs. As the,glass
is still soft, to prevent it from inclining
in one direction or another, as it would
inevitably if held still for a moment, it
is kept constantly whirling, by rolling   A
the pipe in the hands.  If held in the
position A, the hollow  mass will gradually become elongated, and if inverted
and held in the position B, the upper         Glass Blowing.
part sinks, and it takes the form  here
seen;-of course, in any particular case, the workman will be
guided in the mode of handling by a regard to the form which he
wishes to give it. As rapid cooling is constantly taking place,
the glass has to be re-heated frequently, which is done by holding
it in a heated furnace provided for the purpose.
For common window glass, the mass in the form of B, being
re-heated to soften it, is held by the rod with the glass downward, and swung backward and forward in the manner of a pendulum, until it is sufficiently elongated, and has the form C;C  /           D
Preparation of Window Glass.
by this time it has partially cooled, and by holding the extreme
point a little time in the furnace it is softened so that a blast of
air from the lungs is forced through it, and an assistant with
shears accurately removes the lower part, giving it the form D.
The cylindrical part is now to be separated from the rod by a
section around the upper part, as shown in E, and subsequently a
longitudinal fracture is made in the hollow cylinder thus obtained
28




326       SIiICATES OF POTASH AND -SODA —- GLASS.
through its whole length; and it now only remains to open the
cylinder thus prepared in order to reduce it to a perfect plane.
This"is done by softening it in a proper furnace and pressing the
part gently with an iron rod, as represented in the figure.
Preparation of Window Glass.
394. The variety of window glass called crown glass is prepared in a different mode.  The melted mass taken from  the
melting-pot is first blown into the form of a globe, and then an
iron rod attached to it on the side opposite that to which the tube
adheres, and the tube separated by applying a little cold water.
This, of course, leaves an opening, which becomes enlarged by
softening in the heating furnace, and giving it a rapid rotary
motion by means of the iron rod held in the hand.  By heatizng
it several times in this way, the rapid rotary motion being con
tinued, the globe is at length opened out, and becomes a circular
disc, which, after the proper annealing, is cut into panes by a
diamond.
395. Many articles now made of glass, are blown in metallic
moulds prepared for the purpose, or are pressed between two
moulds, one of which shuts into the other, so as to give the
proper shape.  This is called pressed glass.
Plate glass, used for mirrors and for large windows, is poured,
when in a state of fusion, upon a plane surface, and a roller
passed rapidly over it, to reduce it to the proper thickness.  The
surfaces are then ground down to a perfect plane by means of
QUESTroNS.-394. How is crown glass manufactured?  395. Describo
the mode of forming articles of pressed glass. Describe the mode of
forming plates for mirrors.




SILICATES OF POTASH AND SODA —GLASS.                 327
friction with sand and fine emery, and then finely polished by
friction with colcothar, or red oxide of iron.
Small articles of glass may readily be made of glass tube before
a blowpipe, which is blown by a bellows worked by the foot. The
best fuel to be used is burning fluid, consisting of four parts of
strong alcohol and one part of camphene; but oil or tallow will
answer. A very little experience will enable one to bend even
quite large glass tubes, and to perform many other operations
of great importance in the laboratory.
All articles made of glass, if suddenly cooled, are exceedingly
brittle, and liable to fracture from the slightest causes, even
trifling changes of temperature.  They are therefore annetled by
placing them in a furnace prepared for the purpose, and, after
becoming quite hot, are allowed to cool very slowly.  By this
means such a change is produced in the molecular arrangement
of the particles, that this tendency to fracture is much diminished.
Articles of glass that have not been annealed, sometimes break in a
singular manner;-a tumbler half filled with liquid, and grasped by the
hand, will break quite around at the surface of the water by the slight
heat of the hand; or a thick glass tube several inches in length will split
through its whole length simply by being wet, especially if merely touched
by a hard substance, as a piece of wire. Occasionally, after being handled
and laid aside, they break spontaneously.
396. The Bologna, or philosopher's vial, is made in the form
of an ordinary vial, but with thicker sides and a very thick
bottom, and is not annealed. A smart blow may be given to
it by a piece of lead or of wood, or a leaden shot dropped 
into it, without producing any effect; but by dropping into   l
it a small angular piece of flint, it almost invariably falls to
pieces. Sometimes even coarse sand will produce this effect.
In this, and in the following case, the result is due to the
want of annealing.
Prince Rcp~ert's drops are simply drops or tears of glass,
which are made by allowing the glass when melted to drop
from the end of a rod into water, by which they are suddenly cooled. They are perfectly solid, but when the small
end is broken off, the whole mass falls to powder, with a        na
slight explosion.                                             Vial.
QUrESTIoNs.-Why are all articles made of glass annealed before using?
What is likely to be the effect if the process is omitted?  396. Describe
the Bologna vial. What are Prince Rupert's drops?




328   BINARY COMPOUNDS OF BARIUM.
GROUP II.
BARIUM       iMetals, the- protoxides of which are alkaline earths.-These
STRONTIUM  I latter are called baryta, strontia, lime, and magnesia. They
CALcrIUM  possess the same properties which characterize the alkaMAGNESIUM   lies, but in less degree.
BARIUM.
Symbol, Ba; Equivalent, 68'5; Density, -?
397. History, Etc.-This metal is procured by passing vapor
of potassium  over baryta (oxide of barium) at a red heat, or by
passing the galvanic current through hydrate of baryta in contact
with mercury, the latter forming the negative electrode of the
battery. The amalgam thus obtained is carefully heated in a
glass tube through which a current of dry hydrogen is constantly
passing, and the mercury expelled. The barium will be left in
small globules. It has the color and lustre of silver, and melts
at a red heat, but is not easily volatilized.  In the air it is rapidly
oxydized, and when heated burns with, a red flame.  It is also
rapidly oxydized when thrown into water.  Its name is from  the
Greek barlus  heavy; its compounds generally possessing this
characteristic property.
Binary Compounds of Barium.
398. Protoxtde of Barium, BaO; eq., (685 + 8 -) 74'5.This compound has been known many years as barytes or baryta.
It may be obtained by decomposing nitrate of baryta by heat,
which is best done by using an earthern retort in a furnace (as
represented in the figure on next page), and applying the heat as
long as gaseous matter is evolved.
QuEsTINs.- -What metals are included in the second group?  What
do their protoxides form? Do these earths possess alkaline properties?
397. How is barium procured?  How is the metal affected in the air?
From what circumstance or property is the name derived? 398. How
may the alkaline earth, baryta, be obtained?




SALTS  OF BARYTA.                       329
Baryta is a gray powder, which
slakes like lime when water is poured
upon it, and becomes very hot.  It
dissolves readily in water, but is less
soluble than potash or soda-a property by which the alkaline earths
are distinguished from  the alkalies.
It is very caustic to the taste, and
affects vegetable colors in the same
manner as the alkalies.
Peroxide of Barium, BaO. —This
oxide may be formed by passing a current of dry oxygen gas over baryta, at    Preparation of Baryta.
a low red heat; or by simply heating
baryta in an atmosphere of oxygen.  It is used only for the purpose of preparing peroxide of hydrogen (206).
Chloride of Barium, BaCI; eq., (68'5 + 35'4 =) 103.9.This compound is formed by dissolving the native carbonate of
baryta in diluted hydrochloric acid, and by other modes. It
crystalizes in white scales, which contain two atoms of water.
It is very soluble in water, and is much used as a test for sulphmric acid, with which baryta forms an insoluble sulphate
Salts of Baryta.
399. Carbonate of Baryta, BaO,CO,, is found native, and
salled witherite by mineralogists. From it all the other salts
of baryta may be prepared.
Sulphate of Baryta, BaO,SO,.-Sulphate of baryta is found
abundantly in various places, often in beautiful crystals.  It has
a density of about 4'4, and is insoluble in water.  When powQTJESTIONS.-Describe the properties of baryta. Describe the mode
of preparing peroxide of barium. How is chloride of barium formed?
For what.purpose is it used? 399. Is carbonate of baryta found native?
Whllat is said of the occurrence of native sulphate of baryta?
28*




330  BINARY COMPOUNDS OF STRONTIUM.
dered and mixed with charcoal, and heated intensely, it is converted into sulphide of barium, from which the other salts of
baryta may be prepared, as from  the native carbonate.  By
mineralogists, it is called heavy spar, because of its great weight.
Ground to a fine powder, it is used as a substitute for white lead,
either alone or mixed with white lead. All the soluble com
pounds of baryta are poisonous.
Nitrate of Baryta, BaO,NO5.  This salt of baryta is prepared by
digesting the native carbonate, or the sulphide, obtained as just described, in nitric acid. Its only use is in certain chemical analyses, and
in procuring the earth baryta.
STRONTIUM.
Symbol, Sr; Equilvalent, 44; -Density, -?
400. History, Etc. — Strontium  is obtained from  its oxide,
strontia, in the same manner as barium; and in its appearance
it is said very much to resemble that metal. Like barium, also,
it decomposes water with the evolution of hydrogen, and oxydizes
rapidly in the open air.  It receives its name from Strontian, a
village in Scotland, near which it was first obtained.
Binary Compounds of Strontium.
401. Protoxide of Strontium, SrO; eq., (44 + 8 -) 52.This compound, which is the earth strontia, is formed by the
oxydation of strontium.   It is prepared also by heating the
nitrate of strontia to redness, by which the acid is expelled.  It
much resembles baryta, seeming to sustain much the same relation to it that soda sustains to potash.
QUESTIONS. —How  is sulphate of baryta affected when heated with
charcoal? What is it called by mineralogists? For what purpose is it
used? How is nitrate of baryta formed? 400. Give the history, &c.,
of strontium?  From what is the name derived?  401. How is the alkaline earth, strontia, procured? What is said of its relation to baryta?




BINARY COMPOUNDS OF CALCIUM.   331
Salts of Strontia.
402. Carbonate of Strontia, SrO,CO2, is found native;-it is the strontianite of mineralogists.
Sulphate of Strontia, SrO, S03, is also found native, and is called
celestine.  Treated in the same manner as described for sulphate of
baryta (309), the other salts of strontia may be prepared from it.
Nitrate of Strontia, SrO,NO5, is prepared by dissolving the native carbonate in diluted nitric acid, or from the sulphide, as described under
sulphate of baryta. It is much employed in fire-works, to give a beautiful red color to the flame. To show this red fire, mix intimately 40
parts of this salt, 13 of sulphur, 5 of chlorate of potash, and 4 of sulphide of antimony, and burn the mixture upon a dry brick, or marble
slab, in a dark room. The nitrate contains water, and should be well
dried before mixing with the other ingredients.  All the compounds of
strontia communicate a red tint to flame in which they are heated.
CALCIUM.
Symbol, Ca; Equivalent, 20; Dezsity,-?
403. History, Etc. —Calcium is the metallic base of lime, from
which it has been obtained, but only in very small quantity. The
process is precisely the same as that given above for obtaining
barium  from  baryta.  It is said to be of a brilliant white color,
and rapidly oxydizes in the air.  Little is known of its other
properties.
Binary Compounds of Calcium.
404. Protoxide of Calcium-Lime, CaO; eq., (20 + 8 =) 28.
-This compound, commonly known by the name of lime and
quicklimqe, is obtained by exposing carbonate of lime to a strong
QUESTIONS.-402. What is the mineralogical name for carbonate of
strontia?  Sulphate of strontia?  How is nitrate. of strontia prepared?
What use is made of it? 403. Give the history, &c.,of calcium. 404. What
is the common name for protoxide of calcium?  How is it prepared from
the native carbonate?




33.2    BINARY  COMIPOUNDS OF CALCIUM.
red heat, so as to expel its carbonic acid.  If lime of great purity
is required, it should be prepared from  pure carbonate of lime,
such as Iceland spar, or Carrara marble; but to obtain lime for
ordinary purposes, common limestone is used.
The calcination of the carbonate,
Q   tr(               to procure lime for common purposes,
7~(: Ac:e      is effected in kilns, or pits, which are
usually constructed of stone, upon a
hill-side, so that the limestone may be
conveniently introduced at the top,
and the  lime, after calcination, removed from  the opening at the bot>e~~:tom.  Wood is very generally used
for the fuel, but bituminous coal may
MN 0  be substituted  for it, the pieces of
limestone being placed  so that the
flames pass through it.  When the
Lime Kiln.       calcination is finished, of which the
experienced eye can easily judge, the fire is extinguished, and
the lime, when cold, removed.  The calcination of a large kiln
usually require five or six days.
Sometimes the calcination is carried on in perpetual kilns, as
they are called.  The limestone is then introduced in successive
layers, with layers of coal between them; and the fire, once kindled, is continned for an indefinite time, layer after layer of the
coal being consumed, and the lime, after calcination, being
removed from  below.  As the mass settles down in the kiln,
new layers of limestone and coal are introduced at the top.
Lime is a brittle, white, earthy solid, the specific gravity of
which is about 2'3. It phosphoresces powerfully when heated to
fhll redness, and hence its use in the Drummond light (201).  It
is one of the most infusible bodies known; fusing with difficulty
even by the heat of the oxyhydrogen blowpipe.
Exposed to the air, it gradually absorbs carbonic acid, and
crumbles to powder.  It has also a powerful affinity for water,
QussrToIos.-lI-ow is the calcinaation usually effected? D]scribe the
mnocle of calclining lime by the use of coal for fuel. Describe the properties of lime,




SALTS  OF  LIME.                        333
which is absorbed instantly on being poured upon it; and the
combination is attended with great increase of temperature, and
formation of a white bulky hydrate.  The process of slaking lime
consists in forming this hydrate, and the hydrate itself is called
slaked lime.  It differs from the hydrates of strontia and baryta,
in parting with its water at a red heat.  Recently-slaked lime
dissolves sparingly in water, and has this singular property, that
it is more soluble in cold than in hot water.  The- solution has a
caustic, acrid taste, and acts upon vegetable colors like the alkalies.  Exposed to the air, it absorbs carbonic acid; and if agitated, becomes milky, from  the formation of insoluble carbonate
of lime.
Mortar, for building, is prepared by mixing sand with recentlyslaked lime.  It becomes very hard by exposure to the air, in
consequence of the absorption of carbonic acid by the lime.
Combination seems also to take place, to some extent, between
the silica of the sand and the lime.  When the limestone fromr
which the lime is made contains a considerable portion of silica,
alumina, &c., it constitutes hydraulic cemenet, or water-lime.
Mortar prepared from  this, has the property of becoming hard
under water, which is not the case with that prepared from.pure lime.
405. Chloride of Calcium, CaCl.-This compound is formed by dissolving carbonate of lime in hydrochloric acid. It is much used in the
operations of the laboratory, especially for removing moisture from
gases, which it effects readily in consequence of its great affinity for
water. It is often called muriate of lime.
Fluoride of Calcium, CaF, is the fluor spar, or Derbyshire spar of mineralogists. It is of great use to the chemist as affording the chief source
of the element fluorine.
Salts of Lime.
406. Carbonate of Lime, CaO,CO2.-This is one of the most
abundant mineral productions known; it is found in every country
QUESTIONS.-In what consists the slaking of lime? Is lime soluble in
water? ilow is mortar prepared? What is hydraulic cement, or waterlinme?  405. How is chloride of calcium prepared?  What use is made
of it? 406. What varieties of carbonate of lime are mentioned?




334                  SALTS  OF LIME.
as linestone, chalk, iceland spar, marble, &c.  It is decomposed
by heat, and furnishes the quicklime used in preparing mortar.
The beautiful stalactites, frequently seen suspended from  the
roofs of caverns, are formed of this compound. Though insoluble
in pure water, it is slightly soluble in water containing an excess
of carbonic acid.  Water permeating the soil above the caverns,
first becomes charged with carbonic acid, and afterwards takes up
a little carbonate of lime, which is again deposited as the water,
drop after drop, hangs suspended for a time from the roof.  This
is occasioned partly from the evaporation of the water, and partly
by the escape of the carbonic acid, when the water becomes
exposed to the free air of the cavern. As a portion cq the water
falls to the bottom of the cavern, corresponding deposits of carbonate of lime, called stalagmites, are formed upon the floor, and
gradually build themselves upward.  Sometimes a stalactite from
the roof is formed downward until it reaches the corresponding
stalagmite from below, when the two, becoming connected, form
Stalactites.
a column or pillar, as shown at the left in the figure, which is
from' Knapp's Chemical Technology.
407. Sulphate of Lime, CaO,SO, + 2HO. —This compound is
well known as gypsum, and plaster of Paris.  Pure, crystalized
QuEnsToNs. —How are stalactites in caverns formed?  What are the
corresponding deposits on the floor of the cavern called? 407. What
varieties of sulphate of lime are mentioned?




SALTS  OF  LITM                         335
specimens are sometimes called selezite, and compact varieties,
alabaster.  Common gypsum  contains considerable water, which
may be expelled by heat; but there is a variety destitute of water,
called anhlydrite by mineralogists.  When powdered gypsum, the
water of which has been expelled by a moderate heat, is again
made into a paste with water, it soon becomes hard, or "sets,"
as the workmen say;-a property which adapts it admirably for
many purposes in the arts.  In stereotyping, a coat of this paste is
spread carefully over a page of type, set in the ordinary manner,
which, soon becoming hard, is removed, and a cast in common typemetal taken from  it.   This, after certain preparations, and the
emendation of any broken letters that may be found, constitutes
a stereotype p2ate, used in printing.
In a very similar manner it is used for preparing busts of living persons. The process is conducted as follows: The individual is prepare(l
by removing the clothing from his
neck  and shoulders, coating the   ___hair with paste, and applying a                        _
little oil or soap to the part which
is to be covered by the plaster. He  -_    __
then places himself on his back on 
a table, his head being supported     -       -  - -
about an inch above the table by a
small block of wood, and surrounded    =    --
on three sides by a box prepared for.        n               F
the purpose, as represented in the
figure.  The operator, having his
calcined plaster properly mixed with
water, pours a portion of it into the
box, so that it may fill up the space       _under the head; and continues to
mix small portions at a time, and          Formation of Busts
add it to the mass, until the whole
head and face are inclosed, except a small opening at the nostrils. Tile
whole soon becomes hard, attended by a considerable elevation of temperature, but not so much as to be uncomfortable to the subject of the
operation.
In order to remove this plaster inclosure, the operator has taken the
precaution, before applying the plaster, to draw around the head two
pieces of thread or twine, one so that it shall come just below the ears,
as the person lies upoln the table, and the other just above them, bringing the ends of both around under the chin; and just as the plaster is
about to set, taking one of these threads by the two ends, he pulls it out
laterally so as to divide the mass into two parts, as if cut with a knife.
QuEsTIONS. —What is the effect when powdered gypsum is exposed to a
moderate heat?  What now is the effect when it is maixed with water?
Describe the mode of forming plaster busts of living persons.'




336                   SAL TS OF  LIME.
When the second thread has been drawn out in this way, the plaster
inclosure of the face and head will of course be divided into three parts,
the upper part covering the face, and beneath this a ring covering the
ears, and below this the third part covering the back of the head and
neck.  The part covering the face is now to be carefully removed, which
may be done without difficulty; but the second piece which incloses the
ears, will have to be divided below the chin and at the top of the head,
and removed in two pieces. This being done, the subject of the operation is again at liberty to remove himself from the table, leaving the
remaining piece in its place.
The four pieces being brought together, each in its proper place, it is
)vident that the operator has a perfect model or mould of the head and
ll the features of the face, from which the bust is to be prepared; but a
further description of this part of the process will not be needed.
If a part of the breast is to be included with the bust, the arrangements
must of course be made accordingly, in preparing the mould. The operation requires some labor, but is less disagreeable to the subject than might
be supposed before making the trial.
Sulphate of lime is extensively used as a manure in many
countries, with excellent effect.  It is slightly soluble in water,
and is often found in well and spring water, and gives it the
property called hardness.
Phosphates of Lime. —There are several of these salts. One variety is
found native, and is called apatite; it is an essential ingredient of all
fertile soils, and is contained in all varieties of grain used for bread. It
also constitutes the chief part of the solid matter of the bones of animals.
408. Hypochlorite of Lime, CaO,C10.-This is the well-known
chloride of lime, bleaching-powder, or bleaching-salt of commerce.
It is formed by passing a current of chlorine through recentlyslaked lime.  It is a white powder, and emits a faint odor of
chlorine. Great use is made of it in bleaching (229). For this
purpose it is dissolved in water, and the articles to be bleached
soaked in the solution, and then dipped in very dilute acid. The
chlorine which is thus liberated produces the bleaching effect.
The process is usually several times repeated.  It is also used as
a disinfecting agent, the chlorine, as it is gradually liberated,
having the property of destroying deleterious gases present in tha
atmosphere.
The commercial value of bleaching-salt depends entirely upon the
quantity of chlorine it is capable of evolving when used, and is usually
*determined by the quantity of indigo a given weight of it will bleach.
Q usrTrToNs.-What is said of the phosphates of lime?  408. What is
hypochlorite of lime? What use is made of it?




BINARY COMPOUNDS OF MAGNESIUMi. 3o
Tests of Lime. —The proper test for lime is oxalic acid, which
forms with it, in solution, an insoluble white precipitate.  Oxalate
of ammonia is generally used.  A salt of lime dissolved in alcohol
gives to the flame a red color, very similar to that'communilcated
by strontia (402), but of a slightly different tint.
MA G N ES I U M.
Symzbot Mg; Equivalent, 12; Density, 1'87
409. History, Etc. —Magnesium is obtained from  its chloride,
by passing vapor of sodium  or potassium  over it when heated to
redness in a glass tube; the alkaline chloride formecd,. and any
undecomposed chloride of magnesium  which may iremain, are
washed out with cold water, and the metallic magnesiumn subsides.
It is a white metal, of considerable brilliancy, and quite malleable.  Heated in the open air, it readily tak-es ire, and burns
with a brilliant flame, producing the protoxide of the m ietal.  It
is rapidly oxydizedc by boiling, but not by cold water.
Bina'o CGonpousnds of ioynesium,.
410. Protoxide of lfagnesium-g-u~,'essio, t MgO.-Miagnesia
is best obtained by heating the carbonate to redness, by which the
carbonic acid is expelled.  It may also be:prepared by decomposing nitrate of magnesia by heat.:t is a soft, white powder,
and is usually sold under the name of ca7cimed  magn?esia.  It is
very slightly soluble in water, requiring for this purpose 5000
or 6000 times its own weight of water.;  Hydrate of magnesia,
MgO,HO, is found native at H-Ioboke, New Jersey, and other
places.  Magnesia is very infusible, and communicates this property to minerals in which it predominates, as tale and soapstone.
Magnesia is extensively used in medicine as an antiacid. In
QUESTIONs. —What tests of lime are mentioned?  409. How is magnesium obtained? What is said of the metal? 410. Describe the protoxide
of magnesium. What use is made of magnesia?
29




838               SALTS  sOF R  AG NESIA.
the state of hydrate it is said to be a good remedy in cases of
poisoning with arsenic.
Chloride of 1Magnesium, MgCl.-Chloricle of magnesium, which, as we
have just seen, is made use of to obtain the metal, is best procured by
dissolving magnesia in hydrochloric acid, and adding to the solution an
excess of sal-ammoniac; and, after expelling the water, heating the
residue in a platinum crucible, by which means the sal-ammoniac used
will be driven off. Without the sal-ammoniac, the chloride of magnosium would be decomposed by the heat required to expel the water.
Salcts of Miagnesia.
4AlT  Carboat0e of Maagnesia, MgO,C02.-Carbonate of mnag
nesia i. found native, in the maynesite of mineralogists, and may
also be formed from the native sulphate by precipitation with an
alkaline carbonate.  It is nearly insoluble in pure water, but dissolves in water impregnated with carbonic acid, forming the liquid
magnesia of the shops.  When obtained by precipitation with an
alkaline carbonate, it always contains a portion of hydrate of magnesia, and is usually seen in beautiful square blocks, which are
remarkable for their lightness.
It is extensively used in the practice of medicine.
Sulphate of R.naglesia, MgO,SO. -This is the well-known
Epsomt saCt, used in medicine.  It is not unfrequently found in
the w.aters of mineral springs~, as at Epsom, in England, and Dmay
readily be formed by dissolving magnesia, or its carbonate, in
sulphuric acid, and by the action of this acid. upon the mineral
called dolomite, which is a double carbonate of magnesia and
lime.  Its crystals contain 7 eq. of water of crystalization.
It is very soluble, and has a bitter, saline taste.  It may readily
be distinguished from sulphate of soda by the form of its crystals,
or by pouring int.o a solution of it some qaustic potassa, which will
cause a white precipitate.  In sulphate of soda, no precipitate will
be formed.
QUESTIONS.-Dcscribe the mode of preparing chloride of magnesim.l
411. Describe the carbonate of magnesia. What is the common nan'e
of sulphate of imagnesia?  Where is it sometimes found?  1-How  many it
be distinouished from sulphate of soda?




ALUM INUM.                             339
Silicates of Fagnesia, of which there are several, abound in nature.
especially in the talcose and serpentine rocks.
There is no specific test of magnesia, but it is distinguished friom other
substances by different tests; and from most of its soluble salts phosphate
of soda, with ammonia, separates a white precipitate, wvhich is,a double
phosphate of magnesia and ammonia.
GROUP III.
ALUMIINUMI 1
G AuoINuTIT
ZUIRCNIU O ~    J]etals, the protozides or sesquhioxidcls  oq whih are eart/s.-.
ZiTucrouusIU    { The oxides of these metals, which constitute -the earths, are
TTToRIUs      called alumina, gloociza, zirconeia, thorinca, ylt'i, &c.  They
YETBTIUNI     are distinguished from both the alkalies andl a,:lskalin b   earths
ERBIUnu
T ERsB iU A     by being quite insoluble in water, and, of course, destitute
CERI'UM       of any alkaline reaction.  They, howiever, combine readily
LAINTHANUMT   with, and neutralize the most powerful acids.
DinvaDussu J
A L U M I N U Al.
SnJmbol, Al; Equivalent, 13'7; Density, 3 7.
412, Listory, Etc.-The metal aluminum  is obtained by de
composing chloride of aluminum  by the action  of sodiul  or
potassium, in the same manner as magnesium  is prepared fr'om
its chloride.  It is found, after the process, in small globules;
which nay be brought into a single mass by melting it in a close
crucible, or under dry chloride of sodium.  Instead of chloride
of aluminum, the  mineral called cryolite, which  is a double
fluoride of aluminum and sodium, may be used in its preparation.
Aluminum  is very -malleable, and has the brilliant lustre and
white color of silver.  It is not oxydized in the atmosphere at
ordinary temperatures, but burns brilliantly when heated to redness.  Cold water does not affect it.  A  small piece that had
been rolled was found to have a density of 3'7, as given above.
The name of this metal, aluminzum, is derived from alum, a double sulphate of alumina and potassa, from  which the earth is very readily
obtained.
QUEsTIoNs. — What metals belong to Group III.?  I-Iow are they characterizec?'412. How is metallic aluminurm prepared?  What native
mineral may be used for the purpose, instead of the chloride?  Describe
the mletal.




3-10    BIDNA1tY  COMPOUNDS OF  ALUMINUM.. -i;zaiy (Yompoznclz7s of Aluminum.
413, Sosrudioxide of Aluminum, A]203. —This is the earth
aCum'Lnca, and is one of the most abundant of nature's pro.
ductions.  Like silica, it is found in every soil, and in almosdt
all rocks upon the face of the earth.  Crystalized, it forms the
rubyb and the salpphire, two of the most valuable gems.  Emzery,
also, so much used in the arts, is chiefly composed of this earth.
It forms a large part of clay, and gives to it its tenacious character,
fitting it for the use of the potter.
Pure alumina is a white powder, without taste or smell.  It is
easily prepared by pouring solution of caustic potash into a solution of alum,  and washing and heating the soft mass that is
precipitated.  It contracts much in drying, and the dried mass
adheres tenaciously to the tongue when applied to it.
Alumina, though usually serving as a base in the compounds
which it forms, occasionally becomes the electro-negative element, and serves the part of an acid.  Thus, it combines with
potassa to form  aluminate of potassa, and with baryta in like
manner.  The mineral called spinedle is a native aluminate of
magnesia.
This earth is remarkable for its tendency to unite with organic
substances.  If a cotton cloth is immersed in a solution of acetate
of alumina, the earth will deposit itself completely on the fibres
of the cotton and leave the acetic acid free.  On this principle
depend some of the most important processes in calico-printing.
When heated with nitrate of cobalt, it forms a beautiful blue compound.
Native hydrate cf alumina is occasionally found, as gibbsite and
diaspore.
Chloride of Aluminum, A12C13.-This compound is interesting as furnishing the means of obtaining the metal aluminum. For this purpose
it must be anhydrous, and is obtained by passing a current of dry
chlorine through a mixture of alumina and charcoal, heated to redness,
in a porcelain tube.
QUESTIONS.-413. What is-said of the abundance of alumina?  What
gems are mentioned as composed of this earth?  Describe alumina.
Does it, in combination, act as a base or an acid?  What is said of its
tendency to unite with organic substances?  How is chloride of aluminum
formed?




SALTS OF ALUMIjNA.                       341
Sctwts qo Alumina.
414, Stulphate of Alumina, A1,0,,3SO0,. - This salt, though
containing 3 eq. of acid, is considered a neutral (349) sulphate.
It is obtained by treating the purest clays with sulphuric acid,
moderately diluted.  It is very soluble in water, and may be
obtained in small crystals, which contain 18 eq. of water.  It is
used in dyeing.
415. Sulphate of Alumina and Potash, A'10,,3 SO,-  KO,SO,.
-This double salt is the well-known alumn of commerce.  It is
usually formed from a mineral substance called alum-slate, which
is an argillaceous, slaty rock, containing iron pyrites. It is sometimes found naturally formed as an efflorescence upon the surface
of the rock.
Alum is usually seen crystalized in octahedrons, which always
contain 24 eq. of water; it is very soluble in boiling water, and
has a sweetish, astringent taste.  When the crystals are heated,
they melt and froth up very much, in consequence of the large
quantity of water they contain.  Alum is much used in medicine
and in the arts, especially in dyeing and calico-printing.
The alumen ustuzm, or burnt alum, used in medicine as a caustic,
is alum that has been deprived of its water of crystalizatiou by
heat.
Common or potash alum is the type of a whole family of alums;
as soda alum, ammonia alum, iron alumr, chr~omium alan, &c.
Soda and ammonia alums are produced by causing these substances to replace the potash in common alum; and iron and
chromium alums, by replacing the alumina by the sesquioxides
of iron and chromium.  These alums are all exceedingly alike in
their various properties, and all contain, when crystalized, 24
atoms of water.
The relation of these different alums (183) to each other in
composition will best be seen by comparing their formulae.
QUESTIONS.-414. HOW is sulphate of alumina formed? 415. What is
the composition of alum?  From what is it usually formed?  What use
is made of it?  What are some of the different alums that are knowat
29 *




342                SALTS OF ALU M I  A.
1. Potash, or common.....................,S   A0,33  + 2410.
1. 2.. Soda al......................... m.NaSO,83 + A120a, 3S0 + 24H10.
3. Ammonia alum.................. NAi u40,S03 ~ Al2O.,3S0  - + 24H0
4. Ferio-potassa alum.............  KO, SO3, q+ Fe,O,,380s, + 2410O..  5. 5. Ferio-soda alum.............  SNaO,,03 + Fe203,,3S03    24H0.
6. Ferio-ammonia alum......... NH40,SO, + Fe,2,3803, + 24110.
III.  7 Manganeso-potash alum....... O,S03 + Mln20a,3SO,  + 241H0.
IV. 8. Chromio-potash alumn..........', SOa - Cr203,3SO, +- 241H0.
Both the manganeso and chromo series have a soda and an ammonipt
alum, the same as the other series.
Cubic al, um, so called because its crystals usually are cubes, is
formed by pouring solution of carbonate of potassa into a saturated
solution of common alum at about 1220, constantly stirring the mixture for some time. Its composition is KO,SO3+ A1,0,2S0 + 9H11.
416. Silicates of AluAmi.na.-Several double silicates of alumina
and other bases are found native, some of which are of great importance in the arts.  Fetclspar is a double silicate of alumina
and potash, while albite, or Cleave'landite, is a double silicate
of alumina and soda.  Spodumeme and petalite are the same as
the latter, except that they contain less soda, and a small portion
of lithia.
Sometimes feldspar undergoes a natural decomposition, losing
its potash and part of its silica, and is then called kaoini.  This
substance, which is essentially silicate of alumina, more or less
pure, is the basis of all the varieties of porcelain or Chi'na-iware.
The articles are made of this of the proper form, and, when dry,
are exposed to a high temperature in a furnace, by which they
become very compact, but do not fuse.  They are then dipped in
the glaze, which consists chiefly of feldspar, ground to a fine powder, and suspended in water, a coating of which adheres over the
surface; and when the articles are dried and again subjected to
the heat of the furnace, it fuses and forms a glassy envelope,
which incorporates itself with the body previously formed, and
increases its compactness and strength.  The glaze also renders
QUTESTIONS.-Of those alums mentioned in the table, what is the difference in composition between the first and second?  The first and
third?  The first and fourth?  First and seventh?  Seventh and eighth?
416. What native silicates of alumina are mentioned?  What is kaolinl?
What use is made of it?  Describe the mode of manufacturing articles
of porcelain.




SALTS OF ALUMINA.                         343
&henm impervious to liquids, and even to the gases.  For the finer
kinds of porcelain, the kaolin, which constitutes the body, is
mixed with some substance, as alkali or lime, by which it is rendered partially fusible, and the glaze therefore becomes more
perfectly incorporated with it, so as to render articles made
of it slightly translucent.  The colors are applied after the first
burning, and before the glaze, and are composed entirely of
metallic oxides.
417. All the different kinds of clay are composed essentially
of alumina and silica, both of which are very infusible, except
when mixed with the alkalies or lime, or certain metallic oxides,
especially the oxides of iron. Common clay always contains carbonate of lime and oxide of iron, and is therefore quite fusible.
]?ire clay, so called because of its infusibility, contains no lime;
when free from metallic oxides it is called pi~e clay, and articles
made of it are uncolored when removed from the fire.
Stone-ware is made of an infusible clay; and when the articles
are sufficiently heated in the furnace, common salt is thrown upon
them, the soda of which, combining with the materials of the
clay, forms a fusible compound that constitutes the glaze.  Without this the articles would be porous, and water and other liquids
would percolate through them.
Red earthen-ware is made of the most common kinds of clay,
which contain lime and iron, and is so fusible that only a moderate heat is needed in baking articles made of it.  The articles,
after being shaped upon the potters' wheel, are thoroughly dried,
and then coated over with litharge (oxide of lead), in fine powder,
which, by the heat of the furnace afterwards applied, fuses and
spreads over the surface so as to form a fine glaze.  Such vessels,
however, should never be used with acids, which would attack
the oxide of lead and produce poisonous compounds.
Bricks are usually made of the same kind of clay as that just
described.  No glaze is required for them.  The best bricks are
now pressed'when partially dry, to render them more solid, and
QUESTIoNs.-417. Of what are all the different kinds of clay comp osed? What is fire clay? How is the glaze applied to articles of stonlware? Describe red earthen-ware. I-ow are bricks made?




3-14  GLUCINUM) ZIRCONIUM, AND  THORIUM.
to give them  a smoother surface.  The red color is occasioned by
the oxide of iron in the clay, or the sand mixed with it, which,
by the heat in burning, becomes peroxidized.
418. Glucinum, G; Eq., 4.7.-This metal receives its name from the
circumstance that the salts of its oxide, glucina, are sweet (Greek, glukurs,
sweet,) to the taste. It is obtained from its chloride in the same manner
as magnesium and aluminum.
Glucina is an oxide of the metal, but whether it is a protoxide, GO,
or a sesquioxide, 0G203, has not been determined. It is obtained chiefly
from the mineral species called beryl, and therefore the metal has by
some been called beryllunz.  If we consider it as a sesquioxide, the equivalent of the metal will be 6-96, instead of the number given above.
419. Zirconium, Zr; Eq., 34.-Zirconium, in combination with oxygen,
is found in the mineral species zircon, which is a silicate of zirconia.  It
is present also, in small quantity, in some few other minerals.
The earth zirconia is believed to be a sesquioxide of the metal, Zr203.
420. Thorium, Th; Eq., 59.6.-Thorium is found only in a few very rare
minerals, as thorite, pyrochlore, and monasite.
The earth thorina is a protoxide, ThO.
Yttrium, Erbium, and Terbium are found associated in a very few rare
minerals, especially in gadolinite, a mineral species obtained chiefly from
Sweden.
Cerium, Lanthanum, and Didymium occur together in several mineral
species, cerite, allanzite, orthite, &c., but are obtained only in small quantity.
Of these six metals last mentioned, little is really known; —except yttrium
and cerium, they have but recently been discovered.
Gnovr IV.
MIANGANESE,
IRON
ZINC
CiraonMIUI      Mletals which decompose vapor of water at a red heat, but
CAimur    ( are not acted upon by liquid water.
TIN
COBALT
421. The metals of this group are not as well characterized as
those of some of the other groups.  All that we have named as
included in it do indeed, at a red heat, decompose the vapor of
QUESTIONS.-What occasions the red color of bricks?  418. Describe
glucinurm, and the mode of preparing it.  419. In what is zirconium
found?  420. What other metals are mentioned as belonging to this
group?  Name the metals of Group IV.  I-low are they characterized?
421. Are the metals of this group as well characterized as those of some
other groups?




MANGANESE.                         345
water, but some of them  also act slightly upon liquid water.
This is the case more particularly with the first named, manganese; but some of the others, as iron and zinc, are oxydized by
water, at ordinary temperatures, especially if atmospheric air be
also present.
M A N GA NE SE.
Symbol, Mun; Equivalent, 28; Density, 8 3.
422. History. —-Manganese was first obtained by Gahn, from
the substance then called magnesia nigra, which has since been
found to be an oxide of this metal. It received its present name
to distinguish it from  magnesium, which has already been described. It is never found in nature in its metallic state, but its
compounds are very generally diffused, and traces of it occur in
both animal and vegetable substances.
423. Preparation.-Metallic manganese, in consequence of its
great affinity for oxygen, is not obtained without considerable dificulty. To procure it, the black oxide, in fine powder, is mixed
into a paste with oil and lampblack, and exposed, in a close crucible, to the highest heat of a powerful furnace.  The oxide
should first be heated alone in a covered crucible,
to reduce it to the form  of protoxide, and this
then mixed with the lampblack and oil, as directed  >
above.  The last heating, which should be con-    l
tinned two hours, is best performed in a porcelain
crucible, well closed by a cover, and then luted
in a common H-essian crucible, as shown in the
figure, which represents a section through the  Preprtion o
centres of both crucibles.  A  little powdered   Man anese
borax mixed with the materials facilitates the collection of the
metallic globules into a mass.
The metal will be found in a button at the bottom of the
crucible.
QUESTIONS. —422. Give the history of manganese.  323. How is the
metal prepared?




3;46   BINARY  COMPOUNDS  OF  MAN GANESE.
424. Propertes. -  Manganese is a hard, brittle metal, of a
grayish-white color, and granular texture.   It is exceedingly
infuasible, requiring the highest heat of a wind-furnace for fusion.
It soon tarnishes on exposure to the air, and absorbs oxygen with
rapidity when heated to redness in open vessels.  In water at
ordinary temperatures it is slowly oxydized, and the action becomes
mnore decided as the heat is raised.
The metal is best preserved in pieces of glass tube, hermetically
ealed.
B inary Coompounds of jiangaaese.
425, Oxides of ianganese. —There are six oxides of mangatnese, viZ. 
The protoxide, MnO, which is a powerful base.
The sesq'uioxide, IMnO,0, which is a weak base.
The red oxide, Mn3O4,= MnO+ Mn20,, a saline oxide (344: 4).
The binoxide, MnO,, called also peroxide and blackc oxide.
Manlganic acid, MInO,, and
Pcrmaqeganic acidd, In2,O,
426. Protoxide of Manganese, MnO.-This compound, though existing
frequently in combination, is obtained in a separate state with some
difficulty, in consequence of its strong tendency to absorb oxygen fiolm
tble air.  The following is the best method of procuring it. A glass tube
with a bulb, A, near the middle, is provided, ancl the bulb partly filled
Preparation of MnO.
with powdered carbonate of manganese.  A larger tube, b3, is filled
loosely with dry chloride of calcium, or pieces of pumice stone impregnated with strong oil of vitriol, and connected with the first tube, as
QUESTIONS. 424. What are the properties of manganese?  425. -low
many compounds of manganese and oxygen are there?  426. D)scribe
the mode of preparing the protoxide by means of hydrogen gas.




BINARY COMPOUNDS OF MANGANESE. 347
shown in the figure.  The two-necked bottle, C, contains pieces of zinc
and water.
When the whole is arranged as represented, some oil of vitriol is poured
into the bottle, C, and the whole interior of the apparatus is soon filled
with hydrogen gas, which is deprived of its moisture by passing the tube,
B, so that dry hydrogen only surrounds the manganese compound. A
spirit-lamp is now placed under A, the heat of which decomposes the
carbonate of manganese, leaving the protoxicle as a fine powder; and the
absorption of oxygen is prevented by the hydrogen.
After a proper time the tube, A, may be removed, and the extreme
point closed hermetically by the lamp; the tube on the other side of tihe
bulb may also be drawn out and closed
in the same manner, which is accomplished the more readily if, after intro-       __
ducing the manganese compound, the
tube has been a little reduced, as         Preparation of MnO.
shown in the accompanying figure.
Prepared in this way, the protoxide is a powder of a delicate green
color; and thus inclosed from the air, may of course be preserved fo)r
any length of time.
427. Peroxide of Manganese, MnO. —This is the common,
or black oxide, of this metal. It is found in considerable abundance in the State of Vermont, and in other places in this country,
and in Europe.  Heated alone, it is reduced to the sesquioxide,
nID20O,, but when heated with sulphuric acid it is reduced to the
protoxide, with which the acid combines.  This last operation
may be performed in glass vessels.  Heated with hydrochloric
acid, chloride of manganese is formed, and chlorine evolved.  It
is much employed in the arts, in the manufacture of glass, and
bleaching-salt, and for'other purposes.  When crystalized, it is
called by mineralogists pyrolusite.  The sesquioxide very mzuch
resembles the peroxide in appearance, and is often fraudulently
sold for it.
428. Manganic Acid, MnO3. —This compound has never been obtained
in a separate state, but only in combination with bases. It is interesting
as the first metallic acid we are called to consider in the progress of our
course.  It is formed, in combination with potash, by heating equal
weights of peroxide of manganese and nitrate of potash to dull redness ill
an open crucible. The compound, maezganeate ofpotash, is of a dark-grecL
color, and has long been known by the name of chameleon mineral. Di;:solved in cold water, it forms a beautiful green solution, which by continued dilution changes to blue, purple, and, finally, to a brilliant red.
QUESTIONS.-427. Is the black, or peroxide, found native?' What use
is made of it?  428. Describe the mode of preparing manganate of potash.
What is it called?




348        SALTS OF MANGANESE. —-IRON.
Hence its name. The changes are much more rapid when hot water
is used.
429. Permanganic Acid, Mnn0,. —This acid, in combination with potash,
is formed when solution of the manganate of potash is made with hot water,
as above described, by the absorption of oxygen from the air. It is to the
formation of this compound that the red color is owing, which is finally
obtained by solution of chameleon mineral.
From this red solution purple crystals of permanganate of potash may
be obtained; but when an attempt is made to separate either this or the
preceding acid from the bases with which they are united, they are
decomposed.
Chloride of MIanganese is formed by digesting the black oxide in hydrochloric acid. There are two known, the protochloride, MnC1, and sesqulchloride, Mn2C13.
Salts of.langanese.
There are several salts of manganese, but the only one of importance in the arts is the following:
430. Sulphate of langanese, MnO,SO,. —This salt is formed
by digesting the peroxide in strong sulphuric acid by the aid of
heat, and filtering when it has become cold.  The crystals of the
salt are of a rose-red color, and are very soluble in water.  They
always contain some water of crystalization, the quantity depending upon the temperature of the solution in which they are
formed.
Carbonate of Manganese, MnO,CO0, is found native in the mineral
called diallogite.
IR ON.
Sym1bol, Fe (F~rrlnm); Equivalent, 28; Density, 7 7 to 7'9.
431. History.-Irn, the most abundant and most useful of
all the metals, has been known friom  the remotest antiquity.
The ores of' the metal, as well as the metal itself, and some of its
manufactures, are mentioned in the writings of M3oses, and it is
well known the ancient Greeks and Romans were acquainted
with it.
Iron has been found native in small quantities in different
QUESTIONS.-429. How is permanganate of potash formed? 430. Describe the su-lphate of manganese. 431. Has iron been long known? Has
it been found native?




IRON.                          349
countries, but recently a real mine of very pure iron seems to
have been discovered in the territory of Liberia, on the western
coast of Africa.
The occurrence of iron of meteoric *origin, associated with
nickel, and sometimes with cobalt and other metals, is not
uncommon. One mass, at least, of this kind was actually seen
to fall from  the atmosphere, which was subsequently examined;
but many others have been found in such situations as to leave
no doubt that they originated in the same manner. As no such
compound has ever been found in proper iron-mines, it is believed
that these bodies must have their origin in some region foreign
to the earth.
Common meteorites, which have often been seen to fall from
the atmosphere, are of a different composition, containing usually
no metallic iron, but various compounds of iron, manganese,
sulphur, &c.
There are many ores of iron, but the most important are the
hydrated peroxide, called by mineralogists brown hematite; the
peroxide (specular iron, or red hematite), and the black or magnetic oxide, which is a compound of the two preceding.  The
last is the natural magnet, or loadstone.  English iron is obtained
chiefly from the clay-iron stone, which is an impure carbonate of
iron, found abundantly in connection with the coal-measures;
but in this country the metal is extracted almost entirely from
the ores previously mentioned.
432. Preparation.-The   preparation of perfectly pure iron is
a matter of considerable difficulty; but the ordinary method of
reducing it from its ores, is, to heat them intensely, after having
been reduced to small fragments, with charcoal or coke, and lime
or siliceous sand, as the nature of the particular ore may require.
The oxygen of the oxide of iron is absorbed by the heated carbon
and carried off as carbonic acid, while the flux -for so the lime
or sand is called when used for this purp1ose- unites with the
earthy part of the ore and forms a fusible compound, that remains
QUESTIOs.- What is said of meteoric iron? What metals are usually
found in combination with meteoric iron? What are some of the most
impolitant ores of iron? 432. Describe the ordinary modes of reducing
the ores of iron. Why are fluxes used in the operation?
30




350                           I R  N.
upon the surface; the melted iron, by its superior weight, falling
to the bottom.
The nature of the flux used must depend, in any particular case, upon
the character of the ore that is used. Most iron ores occur in the granite
rocks, and therefore the gangue (that is, the earthy matter of the ore,) is
mostly silica, which of itself is very infusible (323), but forms a fusible
mass when mixed with lime. Limestone, in fragments, is therefore introduced with the ore, which is first by the heat changed to caustic lime, by
expulsion of the carbonic acid; and the lime then unites with the silica,
producing the fusible silicate of lime, which, at the high temperature,
flows freely, and allows the reduced particles of iron to unite in a mass.
Occasionally, an iron ore occurs in a limestone region; and then, the
lime alone being also infusible, a flux of silica (sand) is required.
When a sufficient quantity of melted iron has accumulated in
the furnace, it is drawn off by an aperture at the bottom, which
is opened for the purpose. After the iron has been removed, the
slag, formed by the union of the flux with the earthy matter of
the ore, is also drawn off.
0tt~1  ~     The accompanying  figure  represents a
a   5 1!,>\\ section of a blast-furnace, which is used
for the reduction of iron ores.  It is usually
built of stone, thirty or forty feet high, and
lined inside with fire-brick.  The charcoal,
or coke, and the ore, in proper proportion,
with.the necessary flux, are thrown in at
top; and AA  are pipes leading  from  a
A          I   IA  powerful bellows, worked by water or steampower, for supplying the blast of air.  This
air thus forced in, will, of course, be of the
Blast-F'urnae.
same temperature  as the  external atrnosphere, and constitute the cold blast; but sometimes the hot
blast is used, in which case the tubes are so arranged over the
top of the furnace that they are kept hot by the blaze from the
burning mass, and the air, passing through them, becomes heated,
and enters the fire at a temperature of 400~ or 600~.
When once put in operation, a furnace is usually kept in fi:lly
employment for many months, until repairs are needed; the fuel,
QUESTIONS.-What is used for flux when the ore is dug from silicoo.n
rocks?  Describe the blast-furnace used for reducing ores of iron.  HIRu w
is the air sometimes heated before being forced into the furnace?  1is a
furnace, when once heated, kept long in operation?




IRON.                            351
with a proper proportion of ore and flux, being regularly supplied
at the top.
The iron obtained by this process is the cast or pig-iron of commerce, and contains a considerable quantity of carbon and other
substances, by which it is rendered much more fusible than pure
iron, but is at the same time harder and more brittle.
It receives it name from the fact that it may be cast, or melted,
and poured into moulds, so as to form articles of any desired figure
For this purpose, a pattern of the desired article is formed of wood,
and moulded in sand;
and the melted metal is
poured into the cavity
thus  produced.   The
iron is usually melted                 Pouring Cast-iron.
in a cupola furnace, and drawn off in vessels lined with clay (see
figure), from which it is conveniently poured.
To convert cast into malleable iron, it is exposed, in a melted
state, to.a current of air, which plays over its surface, or is forced
through it. The process is usually    7 
conducted in a reverberatory furnace, a section of which is shown
in the figure in the margin.  G is
the grate upon which the fire is
kindled, and  H H   the  hearth
which contains the melted metal.
As the blaze from the fuel passes
to the chimney, C, it comes in           /      /nu 
contact with the melted iron, and 
the carbon it contains-and per-              PuddlingFurnace.
haps other impurities —is gradually burnt out, and the iron
becomes malleable.  This process is called puddling.
But it is not absolutely essential that cast-iron should be fused
in order to be changed into the malleable state.  When small
QUESTIONS.-What is the kind of iron obtained by the process describecl?  Why is it called cast-iron?  How is it fashioned into articles
of any desired form?  How is cast-iron converted into malleable il'on?
Ma.'y small articles made of cast-iron be converted into malleable iron
without being fused? Describe the process.




352                          IRON.
articles made of cast-iron are heated for a time in contact with
powdered oxide of iron in close vessels, they are converted into
malleable iron, and still retain their form perfectly.  The carbon
is gradually extracted by the oxygen of the oxide of iron used.
433. Properties. —We have already, under the last head, in
part described the properties of iron.  It is a hard metal, of a
peculiar gray color, and strong metallic lustre, which is sus.
ceptible of being considerably heightened by polishing.  HIeated
to redness, it becomes very soft and pliable, and is easily worked
under the hammer, which gives it a decidedly fibrous structure.
When malleable iron is strongly heated, it does not at once
change to the liquid state, like most of the other metals, but
becomes soft and pasty at the surface; so that two pieces in this
state, upon being hammered or firmly pressed together, unite in
one piece, or are welded together.  Iron is, perhaps, all things
considered, the most useful metal known, and it is owing in a
great measure to this property, in which it is peculiar; only a
few other metals possessing it, in an inferior degree.
Iron has a strong affinity for oxygen, and exposed to the air
and moisture, it rusts, or oxydizes.  Heated intensely in the
blacksmith's forge, or in the flame. of the compound blowpipe, it
burns with brilliancy. The same effect is produced by igniting a
wire in a receiver of oxygen gas (192), or dropping iron-filings
into the flame of a spirit-lamp.  It has the property also of becoming magnetic, under the influence of another magnet (121),
or of the galvanic current (136).  But pure iron loses its magnetism when the influence of the current is removed.  Some of
the compounds of iron, especially steel and the black oxide, however, retain their magnetism permanently.
The iron of commerce is never pure, but contains in combination more
or less carbon, and other substances.
Perfectly pure iron can be obtained only by heating one of the oxides,
QUESTIONS.-433. Describe the properties of iron. How is malleable
iron affected when heated to redness?  Describe the process of welding.
Are there other metals capable of being welded?  What is said of the
affinity of iron for oxygen?  IHow is it affected when exposed to air and
moisture?  How may iron be made to burn?  I-low may pure iron bn
procured?




IRON.                            353
or the protochloride, in an atmosphere of hydrogen. For this purpose,
the same apparatus may be used as figured in paragraph 426 for forming
protoxide of manganese.  The oxide or chloride being heated by a
lamp, is decomposed by the current of dry hydrogen, and the iron
remains as a grayish-black powder, which may take fire spontaneously
if the air be admitted, but may be preserved any length of time by sealing the tube hermetically. By reducing the iron in a porcelain crucible,
at a very high temperature, it may be obtained in a solid mass, with a
metallic lustre.
434. Steel is a carbonide of iron.  It is formed by heating
bars of malleable iron in close vessels in contact with charcoal,
by which process a small quantity of carbon is absorbed and
incorporated with the iron. This process is called cementation;
and, although the proportion of carbon absorbed by the iron is
small, yet very important changes are produced in its properties.
It becomes more fusible, and may now be melted like cast-iron,
and at the same time has become harder, and is capable of being
temvpered, that is, of being made hard or soft, at pleasure.  This
is done by first heating the article to redness, and then cooling
it suddenly by plunging it into cold water, or oil, by which it is
made very hard and brittle, and subsequently heating it moderately, and allowing it to cool slowly.  By the last heating, a
partial annealing (336) is effected, and, if the operation has been
well conducted, a proper degree of hardness is produced.
Bars of steel, from the cementation process, always present a
blistered surface, occasioned by the liberation of gaseous matte r-probably carbonic oxide-within their substance; but when
the metal has been melted and cast in moulds, it has a perfectly uniform texture, and is called cast-steel.
The melting of blistered steel, to form cast-steel, requires a very high
temperature, and is performed in a furnace, a vertical section of which
is represented by the first figure on next page. A is a small rectangular
chamber, containing the crucible and fuel, and connects with the chimney, C, by a horizontal flue, B. The top of this chamber is covered with
a lid, E F, which may be removed, at pleasure, to allow the introduction
of the fuel and the crucibles, and the current of air is regulated by a
lamper, R. The crucibles are made of the most refractory clays, and
of the form represented in the second figure. When the steel is perfectly
QiUESTIONS.-434. What is steel? How is it formed? In what does it
liffer from iron in its properties?  Htow are bars of blistered steel convelted into cast-steel?  I-low are articles made of steel tempered? What
is meant by this?
30a




354                           I RON.
fiised, the crucible is withdrawn, and the melted metal poured into iron
ingot -moulds prepared for the purpose.
3i{elting Furntace.                 Crucible.,_Bina~'y C6omiozounds of I5'on.
435.,Oxidces. of Iron. -There are four oxides of iron, as
follows, Xviz1:/     A        S
The protoxides, Fe, whiroch is a powerful b oxides of ironase.
The sesquioxide, Fe2O,, which is a feeble base, isomorphous
with alumina, Al203.  It is often called the peroxide.
The oxide, FeO,, called also black or mcgnetic oxide, which is
considered a compound of the proto and sesgui'oxides; —thus,
FeO + Fe20, — Fe304.   It belongs  to  the  class of "saline
oxides" (344: 4).
iFerric acid, FeO3.
The red, or sesquioxide of iron, is obtained by heating green
vitriol (sulphate of the protoxide of iron) to redness in the open
air, and is used' as a polishing-powder, under the name of rouge
QUESTION.-435. Describe the oxides of iron.  How is the red or sesquioxide obtained?




I oN.                             355
or colcotihar.  Earth or clay highly imnpregnated with it forms
the red ochrge used by painters.  The black oxide constitutes the
scale that always forms upon the surface of iron when heated to
redness in the open air.  Large accumulations of it are often seen
by the side of the smith's anvil.  This oxide, found native, constitutes the native magnet, or loadstone, as stated above.  It is
found crystalized in beautiful octahedrons, and in masses, and is
one of the best ores of' the metal.
IFerric acid, FeO3, in combination with potash, as ferrate of potash, is
formed by heating a mixture of iron-filings and nitrate of potash in an
iron crucible; and the salt m,~y be separated from the mass by treating
it with cold water.  It cannot be obtained in a separate state.
436. Chlorides of Iron.-There are twd chlorides of iron, the protochloride, FeC1, and the sesquichloride, FeoCl,; the first may be obtained
by dissolving iron in hydrochloric acid, alad the second by treating the
sesqluioxide in the same manner.  They possess no particular interest.
437. Sulphides of Iron. —The Protosu7Lphide, FeS, of iron is
readily formed by heating a mixture of iron-filings and sulphur,
or by pressing a bar of iron heated to whiteness into a mass of
sulphur.  The sulphur and iron c6mbine. with great energy, and
the liquid sulphide collects in a mass at the bottom, forming, on
cooling, a hard, brittle solid.  It is used in preparing hydrosulphuric acid (263).
Bisu7phlicle of iron, FeS2, is the iron p1yrl tes of mineralogists.
It is of a beautiful yellow color, resembling gold, for which it has
often been mistaken.  It is usually crystalized in cubes.  It is
used in the manufacture of green vitriol and sulphuric acid, and
sometimes for extracting its sulphur.
Though the sulphides of iron are very abundant in nature, they
cannot be used for the extraction of the metal, because of the
great expense it requires, and the iron obtained is of an inferior
quality.
438. Carbonides of Iron. -Both cast-iron and steel, as we hlave
seen, are considered as carbonides of iron, but the ingredients do
QuESTIONS.-W~ hat is the red ochre of painters?  What is the naturarl
magn et, or loads toee   436. Describe the chlorides of iron. 437. Describe
the sulphidos'of iron.  HIow may the protosulphide be formed?  For
what is the bisulphide solmetinmes mistaken?  438. What is said of the
carbonicles of iron?




856 If;SALTS  OF IRON.
not seem to be united exactly in definite proportions.  Cast-iron
usually contains from 2 to 5 per cent. of carbon, while steel
seldom  contains as much as 2 per cent.  Graphite, called also
plumlbago, and blackc lead, has been considered as a carbonide of
iron, but probably it is only a particular form of carbon, usually
containing a portion of iron as an accidental impurity.  It is
found abundantly in nature, and is used in the manufacture of
pencils and crucibles, and as a polishing-powder for stoves and
other articles made of iron.
PJrotiodide of iron, FeI, is formed by digesting iron-filings or wire in
water containing iodine, and evaporating the solution obtained. It is
used ill medicine.
Salts of Iron.
439. Carbonate of Iron, FeO,C02, occurs native and is called
sj)(thcC ifron, or steel ore, by mineralogists.  An impure variety
is called clcy-iron stone.  It may also be obtained by adding
solution of carbonate of soda to solution of green vitriol.  Carbonate of iron, though insoluble in pure water, is dissolved by
water charged with carbonic acid, and is thus contained in the
wIa-iter of c7halybeate springs.
440. Salphate of iron, FeO,SO,.-This salt is the green vitriol
or cop2iecras of commerce, so extensively used in the arts   In crystals it contains 7 eq. of water, and its formula of course is FeO,SO,
-i-7HO.  The crystals belong to the monoclinic system.  It is a
sulphate of the protoxide, and is prepared on a large scale at
Strafford;  Vermont, and other places, from  iron pyrites, which
is first roasted slightly, and then exposed in heaps to the atnliosphere, friom which oxygen is absorbed, converting the sulphur
into sulphur'ic acid, and the iron into oxide of iron; the two
together then uniting to form  the salt in question.  For use in
the laboratory, it is readily formed by the action of dilute oil of
vitriol upon metallic iron.  It often forms upon specimens of
QrUssTIoNs..-What is graphite?  439. Is carbonate of iron found native?  What is it called by mineralogists?  440. What is the green
vitriol or copperas of commerce?  Ilow is it manufactuled in Vermont?
What use is made of it?




C II RO MI UM.                       357
iron ores contained in cabinets, by the action of the atmosphere,
and is seen as a yellowish-white powder.
It is used in coloring black, and in the manufacture of writingink, and for other purposes.
When this salt is heated it first parts with its water, and at
a, full red heat, with its sulphuric acid, a portion of which is decomposed into sulphurous acid and oxygen, but the rest passes
off unchanged.   By the oxygen of the decomposed acid, the
iron is peroxydized, forming the colcothar of commence, before
mentioned.
441. Nitrate of Iron, FeO,N05. —Nitric acid acts readily upon iron, and
at the same time uith the nitrate of iron there is formed also nitrate of
ammonllia, the ainlmonia being produced by the union of a portion of the
nitrogen of the acid with the hydrogen of the water.  The nitric acid
shotuld be considerably diluted.
442. Tests of Iron.-The usual test for iron is solution of yellow prussiate of potash, which forms with it a beautiful blue.  For
an experiment, let a small quantity of common hydrochloric acid
be largely diluted with water, and then pour into it a few drops
of solution of this prussiate, which will instantly give a fine skyblue color if iron be present in the acid, as is almost certain to be
the case.  The iron is derived from  the utensils made use of in
the manufacture of the acid.:
WTith tincture of nutgalls, the soluble salts of iron formn at first
a dark-blue precipitate, which finally becomes black.
C II tR O M I U M.
Symbol, Cr; E'guivalent, 26'7; Density, 6.
443. History, Etc. —Chromium  was discovered in 1797.  It
is found  in  considerable abundance in  Massachusetts, Pennsylvania, and other States, in the mineral called chromze iron,
and also in combination with oxide of lead.  Its name comes
from  the Greek chroma color, in allusion to the splendid color
QUESTioNs.-441-. How is nitrate of iron formed?  442. What tests
of iron are mentioned? 443. What is said of chromium? From what is
the name derived?




58            SALTS  OF1  CHIROMIC ACIID.
of many of its compounds.  It is prepared by heating its oxides
mixed with charcoal, but not without difficulty.  The metal has
a white color, and distinct metallic lustre.  It is very brittle, and
with difficulty fusible.
Metallic chromium  is not used in the arts, but several of its
compounds are important.
Binary ComChponzcls of ChJromium
444. Oxides of Chromium.-Oxygen forms several compounds
with chromium, which, in composition and many of their properties, are analogous to the oxides of iron and manganese; so
that these three metals form a kind of natural family, in the same
manner as potassium, sodium, and lithium.  Only two of these
oxides, the sesquioxide, CrO,, and the teroxide, or chromic acid,
CrO,, are of sufficient importance to claim attention here.
The former of these, Cr203, in combination with protoxide of iron, forming the componMd, FeO,Crar0, constitutes the native chromic iron, which
is the most abundant ore of the metal. It may be prepared by vNarious
modes, but the following is perhaps the best, as it leaves the oxide in a
proper state for use in the arts.  Heat in a crucible an intimate mixture
of 4 parts of bichromato of potash and 1 part of starch, and wash the
mass thoroughly with hot water, to separate the carbonate of potash that
has been formed. The residue, after being dried, is again heated, and
the pure sesquioxide remains.
Sesquioxicle of chromium is not decomposed by heat, and when fuised
with fluxes, it imparts to them a green color. It is used in staining glass
and porcelain. It replaces alumina (415) in the ch1romic aluIms.
C/hromic acid CrO0, is prepared by decomposing a saturated solution
of bichromate of potash with 11- times its volume of oil of vitriol; bisulplhate of potash is formed, and the chromic acid separates in brilliant
red crystals, which are very soluble in water, and deliquescent in the air.
]t is a powerful oxydizing agent, and stronog alcohol thrown upon the dry
crystals is very soon inflamed. With bases it forms important salts.
The chlorides and sulphides of chromium  are not important.
Salts of Chromic Acid.
445. The Chromates of Potash are formed by heating a mixture of native chrome iron in powder with nitre, digesting the
QUESTIOcNS.-444. What is said of the oxides of chromium? How may1n
the sesquioxide be formed?  How is chromic acid prepared?  What is
said of the action of alcohol upon it?  445. How is bicliromate of potasl
formned?




ZINC.                             359
mass obtained in hot water, and saturating the solution with dilute;r
sulphuric acid. After a little time the clear red liquid is poured
off, and evaporated, when crystals of bichronmate of potash, KO,
2Cr03, are separated, from  the excess of sulphuric acid present,
and the sulphates of iron and alumina.
The neutral chromate of potash, KO,Cr03, is now easily procured by neutralizing a solution of the bichromate with carbonate'
of potash, and crystalizing.
The bichromate, which is of a deep red color, is  much used i n
dyeing, and in calico-printing, and for many purposes in t1I:
chemical laboratory.
446. Chroinate of Lead, PbO,CrO,. -This is the beautiful
chrome yellow, used as a paint.  It is formed by mixing solutiiions
of one of the chromates of potash and acetate or nitrate of lead.
The beauty of the color will depend somewhat on the strengtih
of the solutions used, and other circumstances.   Chronme yreen is
formed by mixing the chromate of lead with Prussian blue, in a
particular stage of the process of manufacture.
Z I N C.,ymbol, Zn; Eqzuivaent, 325; Denlsity, 7.
447. Itistory. —This metal has been known several cenlturies,
but was not, for many years, much used.  Its chief ores are
calaminfte, which is a native carbonate, and blecnie, rwhich  is:
sulphide; but several others are known.  These ores are found
in considerable abundance in New Jersey, and other parts of this
country.
448. Preparation.-  The ores of zincare reduied lby firSt,
ronsting  themr  in the open air, and then dRii:tillin' tlhem  with
charcoal in close crucibles, fromt which a tube iles ce:,s directly
Qua sTosi.o  How is the neutral clromaito of potas  fto-[id?  4.   ),scribe thle mole of preparing chromate of lead.  oy'hat n er.I'  is it
familiar1ly know n?   What cuse is macle  of it?  HIo-w is c;rioll,,!i "rn [,r.pared?  4147. Has.inc been long( kno\wn?  NWhi,et o(o'S 0o' it.no (:nill
tioled? 418o. Descriie the mode of reducing the meta d io'(  i.t - jie oe5.




360                           Z IN
through the bottom.  The metal is volatilized by the heat, and
descends through  the tube, from  which it is received into  a
vessel of water.   The necessity of excluding the air perfectly,
arises from  the fact that vapor of zinc, on coming in  contact
with the oxygen of the air, is at once oxydized; and the
object of having the tube which conveys away the volatilized
metal pass directly downward, is, to preserve
its temperature so high that it shall not be>     come clogged by the condensed metal.
The figure in the margin represents the section
of a crucible used for this purpose, with its charge
of ore and charcoal, and tube made of fire-clay
is carefully luted on, and it is supported a little
above the grate of the furnace by a fire-brick.
The zinc, as it is separated from  the ore, taking
the gaseous state, passes downward through the
tube into a basin of water placed below to receive
b      E' Il  ]  it.  The part of the tube below the bottom of the
crucible, not being surrounded by the fire, remains
comparatively cold; and the metal, before it reaches
the water, is condensed to the liquid state, and falls
in drops into the water.
Crucible fon reducing  Commercial zinc usually contains iron, lead, and
other impurities, from  most of which it may be
separated by distillation in this manner.
V.9, Propertics.-Zinc has a bluish-white color and a strong
metallic lustre.   In masses, it always has a highly crystaline
structure, and in commerce it is called spelter.  When cold it is
quite brittle; but heated to about 3000, it becomes malleable,
and may be rolled into thin sheets.  Heated to 7730, it melts;
at a little higher temperature, in the open air, it takes fire and
burns with a brilliant white flame, producing the protoxide, which
assumes an exceedingly delicate gossamer appearance, and has
been called nil/vil ctdb.zmm, pIhilosoplhers' wool, and by other names.
Zinc is much used in tthe arts, in the preparation of brass, in
the construction of galvanic batteries, and, rolled in thin sheets,
as a substitute for sheet-iron and tin-plate.  Recently it has been
QuESTIONS.-W'hy is it lecessary to excdclue the air? Describe tlhe
form of crucible used in reducl ing  tllese boes.  449. Describe the properties of zinc. What -is its molting point? What is prod-lceld AV0when it
is highly heated in thile open air?   What use is made of zinc?




SALTS OF  ZINC.                         361
considerably used as a coating for sheet-iron, in the same manner
as tin, to protect it from  oxydation.  The iron thus prepared is
known in the arts as galvanized iron.
Bincrary Compoounds of Zinc.
450. Protoxide of Zinc, ZnO.-This is the only oxide of zinc
known.  It is of a yellowish-white color, and may be prepared, as
above described, by heating zinc in the open air, or by precipitating it from solution of white vitriol (sulphate of zinc) by carbonate of ammonia.  It is much used in painting as a substitute
for white lead; and is manufactured on a large scale directly from
the ores of zinc, in France, and in New Jersey.
451. Chloride of Zinc, ZnC(l.-Chloride of zinc is formed by
dissolving commercial zinc in hydrochloric acid, or by burning
zinc in chlorine gas.  By evaporation it may be obtained as a
white solid, but is very deliquescent in the air.  Mixed with
sal-ammoniae, it serves an excellent purpose in tinning articles
of copper, brass, and other metals.
Sulphide of Zinc, ZnS.-This compound of zinc is found( native, and
constitutes, as has been stated, one of its ores. It may be prepared artificially by heating the metal with sulphur.
Salts of Zinc.
There are several salts of zinc, btit the most important is the
following:
452. Sulphate of Zinc, ZnO,SO,.-Sulphate of zinc is a white
salt, which, in commerce, is called white vitriol.  It is very
soluble in water; and is sometimes used in medicine as a powerful emetic.
The ordinary salt contains 7 atoms of water of crystalization,
and its formula is ZnO,SO, + 7O0; but by using the proper
means, it may be crystalized with 5, 2, or even 1 atom of water.
QUESTIONS.-450. What is the only oxide of zinc that is known? What
use is nmade of it?  451. How is chloride of zinc formed?  To what use
is it applied?  452. What is sulphate of zinc called in comlmerce?
31




362                  C A D MI U M. -T I N.
Oxide of zinc is precipitated from its soluble salts by the caustic alkalies, but the precipitate is again dissolved by an excess of the alkali,
C(arbonate of zinc is found native, and called calaminle.
CADMIUM.
Symbol, Cd; Etquivalent, 56; Density, 8'6.
453. History, Etc.-Cadmium is a very volatile metal, usually
found associated with zinc. In appearance it can scarcely be distinguished by the eye from tin, but is rather harder. It melts at 442~,
— the melting point of tin,-and sublimes at a temperature but little
above the boiling point of mercury.  Its properties indicate that
it would be a useful metal in the arts, but it has hitherto been
found only in small quantities.
Protoxide of Cadmium, CdO, is the only compound of these two elements
that is known.
The protosulphide, CdS, is found native, as thegrenockite of mineralogists.
TI N.
Symbol, Sn (Stannum); Equivalent, 58; De.nsity, 73.
454. History. -  Tin has been known from  the most remote
antiquity, and was in common use in the time of 3Moses.  It is
supposed the ancients obtained it chiefly from Cornwall, England,
the mines of which still yield a large part of the tin of commerce.
It is found also in India, Germany, Chili, and Mexico; but has
not yet been discovered in the United States, except a few small
crystals of the oxide in Chesterfield, 3Massachusetts, and at Middletown, Connecticut, and a small vein of the same ore in the
town of Jackson, New 11ampshire.  The chief ores are the oxide
and sulphide.
4.55. Preparation and Properties. -  Most of the tin of commerce is obtained from the oxide, which is reduced by the action
QUESTIONS.-_453. What is said of cadmium?  What is its meltilng
point?'454. Has tin been long known?  Where was it obtained in
ancient times?  What countries now produce tin?  Is it found in tlhe
United States?  What are the chief ores of tin?  455. Mention soile
of its more imlportaint propertieS.




BINARY  COMPOUN'DS OF  TIN.                       363
of charcoal at a high temperature.  It is a brilliant white metal,
like silver, but is less hard than the latter   It is very malleable,
and is rolled into very thin leaves, called tin-foil.  It is inelastic,
and when a rod of it is bent, a peculiar crackling noise, called the
cry of tin, is produced, occasioned by its crystaline structure.  It
melts at 4420, and at a red heat is rapidly oxydized; at a white
heat it burns with flame.
Tin is not readily acted on by the atmosphere or by moisture, but is
dissolved slowly by hydrochloric acid, forming chloride of tin, and byhot sulphuric acid, forming sulphate of the protoxide; by dilute nitric
acid it is converted into the binoxide, which is insoluble in the acids.
Uses. —Tin is used for many purposes in the arts, both alone
and combined with other -metals, as in Britannica metal, which is
an alloy of tin and antimony, with a small proportion of copper.
It is also used extensively to coat sheets of copper and iron, to
prevent the oxydizing influence of the air and moisture, and other
agents.  Thin sheets of iron, coated over with tin, constitute the
well-known and highly useful tin-plate.. Binary Cominounds of Tin.
456. Oxides of Tin. — There are two well-defined oxides of tin, the
protoxide, SnO, and the peroxide, SnOb; but the latter alone possesses
sufficient importance to require a description.
Peroxide of Tin is formed by exposing the metal to the action of nitric
acid a little diluted. It may also be precipitated from a solution of the
perchloride of tin (soon to be described) by an alkali. As obtained by
the mode last mentioned, it is soluble in acids, but not as procured by the
other mode. It is of a yellowish-gray color, and from the circumstance
that it is capable of combining with bases in the manner of an acid, it
has been called stannic acid.  It is much used as a polishing-powder,
under the name of plutty of tin.  Melted with ingredients for forming
glass, it produces a white enamel.
457, Chlorides of Tin.-Protochloride of Tin, SnCl, is formed by dissolving the metal in boiling hydrochloric acid.  By evaporating the
solution it may be obtained in crystals, which contain 2 eq. of water.
It is used as a mordant in dyeing, and as a powerful deoxydizing agent
in the laboratory.  The perclloride, S1C12, is formed by distilling a mixture of 1 part of tin-filings and 3 parts of corrosive sublimate, or by cauQUEsTIOsN.-To what use is tin applied? What is the tin-plate of com:,
mterce?  456. What oxides of tin are known?  What is the substancecalled pltty of tin?  To what use is it applied?  457. What chlorides
of tin are there?




364        COBALT.-BIRNAR~Y COMIPOUNDS OF COBALT.
tiolsly dissolving the metal in nitro-hydrochloric acid.  It is much used
as a mordant in dyeing, and as a disinfecting agent.
There are two szlp ides of tinll;-the persulp hide, SnS., sometimes called
Caurm  nt21siveUm, or mosaic gold, has a yellow color, and metallic lustre,
and is used as a paint, and also instead of the zinc amalgam (90) for
exciting electrical machines.
There are no important salts of tin.
COBALT.
Syrnbo1, Co; Equeivcaent,  29'5; Dcensty, 8'5.
458. Ilistory, Etc.-Cobalt is almost always found associated
with nickel, the metal next to be described;-as found in mines
both are usually in combination with arsenic.  The pure metal
is obtained with some difficulty.   The best mode is to heat oxalate of cobalt in a small crucible, on which a cover is closely
luted.  It is of a reddish-white color, and is hard and brittle, and
difficult to fuse.  It is capable of becoming magnetic.
Cobalt is comparatively a rare metal.  In combination with arsenic, it
is found at Chatham, in Connecticut, in the minerals called smnalatie and
chloanthite.
Binary andt Otuterl Compo^nds of CocZal.
459. Oxides of Cobalt —There are two oxides of cobalt, the protoxide,
CoO, and the sesquioxide, CoOa3, the former of which, mixed with some
impurities, is sold in commerce as a gray powder, under the name of
zaf'e.  Fused with silica and potash, it forms smnalt, which is used for
coloring glass, porcelain, &c., blue.  The sesqgi orperoxide is unimportant.
460. Chloride of Cobalt, CoC1, is formed by dissolving zaffre in hydrochloric acid.  The solution has a pink color, and yields by evaporation
small crystals of the same tint.  Writing made with a diluted solution
of it is nearly invisible, but becomes of a beautiful but pale blue color
when the paper is warmed by the fire, and again disappears as the paper
cools.  It has been called HIellot's Sympathetic Ink.  The addition of a
salt of nickel gives the writing a green color.
The salts of cobalt possess no especial interest.  The subcarbonate is a
fine powder of a very delicate pink tint.
QUESTIONS. —What sulphides of tin are there?  458. With what other
metal is cobalt.usually found associated?  Where is this metal found?
459. What oxides of cobalt are there?  460. How is chloride of cobalt
formed?  Describe the mode of using Hellot's Sympathetic Ink




NI C K E L.-A N T I 0  N Y.                 365
N I C K E L.
Sym2bol, Ni; -Equivalent, 29'6; Density, 8-8.
461. History, Etc.-Nickel and cobalt, as before intimated,
are in nature almost inseparable companions. Arsenical nickel
and cobalt are found at Chatham, in Connecticut, and also in
Missouri, and in various places in Europe; but mines of these
metals are not common.  Nickel is generally, if not always, combined with meteoric iron (431), of the mass of which it sometimes
constitutes as much as ten per cent.
Pure nickel has a grayish-white color, and strong metallic
lustre.  It is quite hard, but malleable, and is nearly as difficult
to melt as iron. Like iron and cobalt, it is capable of becoming
magnetic.  It is not readily acted upon by the air or by moisture.
It is much used in the arts to form  the alloy called Germann
silter, which is composed of copper 10 parts, zinc 6, and nickel 4.
None of the compounds of nickel possess sufficient interest to
require description here.
GtOUP V.
ANTIMONY    1
BISIUTH
(1rPPER          Metals which are incapable of decomiposing w'ater, and
VANADIUhA      whose oxides are not redzced by the mere action of heat.
MOLYBDENUM       All of them, except lead and copper, are brittle; and
TUNGSTEN       all, except antimony, bismuth, lead, and copper, are
TITANIUMi     fusible only at very high temperatures.
URANIUMI
COLuMBIUM
PELOPIUIo    J
ANTIMONY.
Sygmbo7, Sb (Stibintmz); E2ucivalent, 129; Densitty, 6'7.
462. History. — Antimony is remarkable as having been the
first metal discovered after the seven metals (332) known to the
QUEsTIONs.-461.  What is said of the metal nickel?  In what is it
almost always found? Describe the metal. For what is it used? How
are the metals of Group V. characterized?  Name the metals of this
group. 462. For what is antimony remarkable?
31 *




36 6    BINARY  COMPOUNDS  OF ANTIMONY.
ancients.  It has been found in the metallic state, but is prepared
chiefly from the sulphide, which is not of unfrequent occurrence.
463. Preparation. —The metal, called also regflu s qf annimony,
is obtained by heating the sulphide with iron-filings, or carbonate
of potash.  When iron-filings are used, the sulphur is simply
transferred from the antimony to the iron, and, of course, sulb
phide of iron is formed; but the metal thus obtained always
contains a portion  of iron, and is otherwise impure.  By the
other process, the sulphur is converted into sulphuric acid, which
combines with the potash, forming sulphate of potash; and the
metallic antimony, being thus set fiee, falls to the bottom  of the
crucible.
464. Properties.-Antimony is a very brittle metal, of a white
color, and brilliant lustre.  It always has a highly crystaline
structure, and melts at a temperature a little below redness; and
may be slowly distilled in a current of hydrogen gas. A small
fragment, heated on a piece of charcoal, before the blowpipe,
takes fire; and when thrown upon the floor breaks into numerous
globules, which continue to burn as they are scattered, leaving a
train to mark their path, and filling the air with fumes of the
oxide.
465. Alloys of Antimony.-Antimony, being very brittle, is
not adapted for use alone in the arts, but with other metals it
forms several very useful alloys. One of these, called Bri'tangzia
metal, is composed, of tin 88 or 90 parts, and antimony 12 to 10
parts.   Sometimes a small proportion of copper is added, not
exceeding 3 or 4 per cent. of the whole.
Its alloy with lead will be described hereafter.
]Binary Compoulndcs of Antimony.
466. Oxides of Antimony.- Antimony forms with oxygen two compounds which are well'defined, viz., oxide of antimony, SbO0, and antimonic acid, Sb05; but these are capable of combining with each other so
as to form one or two other intermediate compounds.
QUESTroNs. —463. How is antimony obtained from the native sulphide?
Describe the two processes. 464. Describe the metal. How is it affected
when intensely heated in the air?  465. What alloys of antimony are
used in the arlts?  460, What oxides of antimony are mentioned?




BISMiUTH.                            367
467. Chlorides of Antimony. — There are two chlorides of antimony,
SbC13, and SbC15, corresponding in composition, it will be seen, with the
oxides. The terchloride, SbCs3, is sometimes called butter' of antimony.
It is soluble in a small quantity of water, but if the solution be diluted, a
white powder is precipitated, called powder of algoroth.  It is an oxychloride, SbC13,2SbO3 + HO.
468. Sulphides of Antimony.-Two sulphides of antimony are known,
corresponding in composition with the oxides and chlorides, and having
the formulse SbS3, and SbS5.  The first of these is the native sulphide;when this is roasted in the air, oxygen is absorbed, and oxysulphid
of antimony, SbS3 + SbO3, is formed, often called glass of antimony, or
liver of antimony.
When the native sulphide is boiled in a solution of potassa or soda, a
liquid is obtained, from which, on cooling, an orange-red matter is deposited, called Kernmes mineral.  On subsequently neutralizing the cold
solution with an acid, the golden sulphide of the pharmacopoeia is obtained.  These compounds now possess little interest, but formerly were
much used in medicine.
The salts of antimony are unimportant, except tartar emetic, used in
medicine, which will be described hereafter.
BISMUTH.
- Stymbol,  Bi; E-Fuivalent, 213; Delns;ty, 9'8.
469. History, Etc. —Metallic bismuth is found in small quantities in Monroe, Connecticut, and other places, but is chiefly
obtained from  the native sulphide.  In mass, it much resembles
antimony in its crystaline structure, but has less lustre, and is
of a reddish color.  It is brittle when cold, but may be hammered when moderately heated.  It melts at about 4770, and
sublimes at a high temperature.   By melting a considerable
quantity in a large crucible, placing it in a situation to cool
very slowly, and pouring off all that remains liquid, as soon as it
begins to solidify at the surface, crystals of considerable size may
be obtained.
The metal is unchanged in the atmosphere, but tarnishes
slightly by moisture. Heated in the open air it burns with a
bluish flame.
It is too brittle for use by itself in the arts, but with some other metals
QuEsTIONS.-467.  What is said of the chlorides of antimony? 468. What
sulphides of antimony are known? 469. Is bismuth found native?  Describe the metal.  May it be obtained in crystals?  What is said of its
use in the arts?




368                          LEAD.
it forms important alloys. It may be substituted, in whole or in part, for
antimony in Britannia metal (465).
In some of their chemical properties, antimony and bismuth are analogous to phosphorus and arsenic, and also to nitrogen.
Binary and other Compounds of Bismuth.
There are several oxides, chlorides, &c.; but they possess no special
interest.
470. Nitrate of Bismuth, BiO,NO5. —This salt is formed by dissolving
the metal in nitric acid. It is soluble in water; but if the solution is
largely diluted, the salt is decomposed, and subnitrate of bismuth precipitated.  This last salt is used in medicine, and also as a cosmetic.
L EAD.
Symbol, Pb (Plumburnm); E2'quivalcent, 103 7; Dentsity, 1144.
471. History.-Lead is one of the seven metals known to the
ancients.  Its most important and most abundant ore, from which
all the lead of commerce is extracted, is the sulphide, the galena
of mineralogists; but it is found in many other forms, as carbonate,
sulphate, phosphate, &c.  It is very abundant in different parts
of this country.
472. Preparation.-The metal is reduced from the native sulphide by first roasting it in the open air, and subsequently heating
it with lime in a charcoal fire.  The ore usually contains a little
silver, which remains in combination with the lead.
The metal is also easily reduced by heating the native sulphide,
in fine powder, with iron nails, in a close crucible. The sulphur
of the ore, in this case, passes directly to the iron, forming sulphidcle of iron.
473. Properties. -  Lead  is a bluish-gray metal, and when
recently cut has a strong metallic lustre; but the surfhce soon
tarnishes on exposure to the air.  It is soft and malleable, but
QuESTIONS. —470. Describe the nitrate of bismuth.  471.. What is the
most common ore of lead?  What other ores are msentioned?  4:72. Iow
is the metal reducedlfrom the native sulphide? What is the second mode
mlentioned?  473. Describe the properties of lead.




BINARY  COMPOUNDS OF LEAD.                       369
not very tenacious.  H-leated to about 635~ it melts, and at very
high temperatures is slightly volatilized.  Exposed to the air and
moisture, it is gradually corroded; and a crust, the white carbonate, is formed upon its surface.
The peculiar properties of lead fit it for use in the arts for
many purposes; but one of its most important uses is in constructing pipes for conveying water.  But when the water is to
be used for drinking, care should always be taken to have the
tubes kept constantly filled with water, as the introduction of air
tends to form the highly poisonous carbonate; and even then the
water should not be used until it has been proved by experiment
that the particular water to be discharged by the tube is not
capable of acting upon the lead.
Lead is gradually acted on by boiling sulphuric acid; but its
only proper solvent among mineral acids is the nitric, which forms
with it a soluble salt.
474. Alloys of Lead.-Lead forms with other metals many
useful alloys.  Two parts of tin and one of lead, fused together,
form  soft solder, which is much used in cementing together the
different pieces of articles made of tin-plate, Britannia metal, &c.
A coarser kind, which requires a higher temperature to melt it,
is composed of lead 3 parts and tin 1 part.  Petwter is an alloy
of lead and antimony, and sometimes a little copper.  Typemetal is an alloy of 3 parts of lead to 1 of antimony.  Tin, lead,
and bismuth, form a very fusible alloy; when made of 8 parts
of bismuth, 5 of lead, and 3 of tin, it will melt in boiling water.
Binary Compounds of Lead.
475. Protoxide of Lead, PbO.-Protoxide of lead is formed
by heating lead, in the open air, a little above its melting point;
oxygen is gradually absorbed, and a yellow powder formed, which
was formerly used as a paint, and called massicot. As usually
manufactured, it is in the form of reddish-yellow scales, occaQUESTIONS.-What is said of the use of lead for water-pipes?  What
is the only mineral acid that dissolves lead?  474. What alloys of leniad
are mentioned?  What:- is pewter?  Type-metal?  What alloy of lead
melts in boiling water? 475. How is protoxide of lead formed?




370                    SALTS  OF  LEAD.
sioned by its having been partially fused.  It is much used in
painting as a dryer, and is called litharle. It fuses readily at
high temperatures, and enters into combination with several of
the earths and alkalies, producing a transparent glass, which
renders it an excellent substance for glazing some kinds of
earthenware. With powerful bases it is capable of combining
as an acid.
476. Peroxide of Lead, PbO2. -- This oxide is obtained by
digesting red lead (the compound next to be described) in nitric
acid, which dissolves out the protoxide, leaving the peroxide quite
pure, in the form of powder.  It is also called plumbic acid.
477. Red Oxide of Lead, Pb304.-This compound is the rted
lea(d, or 7miniunt, of commerce, much used in the arts as a paint,
and as one of the ingredients in the manufacture of flint glass.
It is formed by heating metallic lead to a temperature of 500~ or
6000, in the open air, so as to oxydize it without fusing the oxide,
and continuing the heat for some time.  Heated to redness, it
gives up a portion of its oxygen and is reduced to the protoxide.
Minium is a compound of the proto and peroxides (2PbOPbO,),
and is therefore a plumbate of the protoxide of lead.
478. Sulphide of Lead, PbS.-This compound has already been mentioned as constituting the only important ore of lead, called galena.
It is also formed by passing a current of sulphuretted hydrogen through
a solution of any salt of lead. As it occurs native, its color very much
resembles that of metallic lead, and its structure is always crystaline.
Salts of Lead.
479. Carbonate of Lead, PbO,C02.-This is the white lead
of commerce, so extensively used in painting.  It is formed by
several different modes, and is also found as a natural production.
Nearly all the white lead of commerce, at the present time, is
adulterated by mixing sulphate of baryta (399) with it in fine
powder. By treating the mixture with nitric acid, the carbonate
QuEsTIONs.-What use is made of the protoxide of leadl?  What is said
of its fusibility? 476. Describe the mode of preparing the peroxide.
477. What is the red lead or minium of commerce? What use is made
of it?  478. Describe sulphide of lead. 479. What is the white lead
used by painters?'With what is it usually adulterated?  IHow may the
firaud be detected?




COPPER.                             837
of lead will be dissolved, and the baryta left as a white powder.
Taken into the system, white lead acts as a violent poison, producing the disease called painte2rs' cholic.
480. Sulphate of Lead, PbO,S03. — Sulphate of lead is found native,
and called anglesite by mineralogists.  It is also formed when solultion
of any sulphate, as sulphate of soda, is mixed with solution of any salt
of lead. It is sometimes used in painting as a substitute for white lead.
Nitrate of Lead, PbO,NO5.-Nitrate of lead is easily formed by dissolving metallic lead, or its protoxide, or carbonate, in nitric acid.
Zinc, iron, and tin precipitate lead from all its soluble salts in its
metallic state.  Make a solution of 1 part of nitrate or acetate of lead i-l
24 parts of distilled water, acidulated with acetic acid, and suspend in it,
near the top, a piece of clean zinc; the precipitation of the lead will
immediately commence, and in the course of 24 or 48 hours, the met al
will appear in the form  of large thin leaves, called sometimes arbor
Saturni.
481. Test of Lead.-Hyclrosulphuric acid precipitates lead as a darkcolored sulphide from all its soluble salts, and even blackens those that
are insoluble, as the carbonate, when suspended as a fine powder in
water.
COPPER.
S     0ymbol, Cu (Ctcprum); Equivalent, 31.7; Density, 89).
482. History. —Copper has been known from the earliest ages,
and is often found in the earth in its metallic state.  Mlasses of
immense size of nearly pure metal have been found in the region
of Lake Superior.  One, 40 feet long, was estimated to weigh
200 tons.  It is also found as a carbonate, sulphide, and oxide,
as well as in other combinations.  The ores of copper are very
generally diffused, some of them  being found in almost every
country.
483. Preparation.-Metallic copper is obtained from the oxides
and the native carbonates, simply by heating these ores with charcoal; but the sulphide, especially when mixed with iron, is
QUuSTIONS.-480.   What is said of the sulphate of lead? Describe tihe
mode of forming the arbor Saturni.  481. What test of lead when in
solution is mentioned?  482. Has copper been long known?  What is
said of masses that have been found native?  What ores of copper aro
mentioned?  483. HTow may the metal be reduced from its oxides and
orhbonates?




372    BINARY COMPOUNDS OF COPPER.
reduced with more difficulty, and the process is too complicated
to be given here in detail.
484. Properties.-Copper is distinguished by its peculiar red
color.  It is very ductile and malleable, but less tenacious than
iron.  To fuse it a bright red heat is required, but its melting
point is much below that of cast;iron.  It forms crystals belonging to the monometric system.  It is less liable to be corroded by
air and moisture than iron, but is gradually acted on by the joint
agency of these elements, and becomes coated with a green crust,
which is carbonate of copper.  Heated to redness in the air, i't
becomes oxydized, and nitric acid readily dissolves it.  It is used
extensively in the arts, both alone and in combination with other
metals.
485. Alloys of Copper. —Copper forms with other metals many
very useful alloys.  Three parts of copper with one of zinc constitutes brass; and by a variation of the proportions, the alloys
called tombac, Dutch gold, and pinchbeck, are produced.  Bronze
is an alloy of copper and about 10 per cent. of its weight of tin;
and bell,-neta4l, an alloy of 4 parts of copper with 1 of tin; while
speculuzm   mnetl, used for the mirrors of reflecting telescopes, contains about 2 parts of this metal to 1 of tin.  Equal parts of copper
and zinc form  hard  solder, which is used in soldering articles
of brass.
Biniar&y Compounds of Copiper.
486. Oxides of Copper.  Red oxide of copper, Cu,O, is a suboxide; it is found native. The black or protoxide, CuO, is also
found native, and is produced when copper is heated to redness
in the open air.  It is also easily procured by heating to redness
the sulphate or nitrate of copper.  There are two other oxides.
Chlorides of Copper.-()f these there are two, the subchloride, Cuo2C,
and the protochloride, CuCi, but they possess no special interest.
Sulphides of Copper.-There are two sulphides of copper, corresponding
in composition to the chlorides, viz., the subsulphide, CuS, and the pro-tosulphide, CuS.  Copper pyrites, vitreous copper, and variegated copper are
native sulphides of copper, or copper and iron.
QuEsTIoNS.-484. How is copper readily distinguished from the other
metals?  Describe its properties. 485. What alloys of copper are used
in the arts?  486. What oxides of copper are there?  What chlorides?
What sulphides?




SALTS  OF  COPPER.                          373
Salts of Copper.
487. Sullphate of Copper, CuO,S03, or, in crystals, CuO,S03
+ 511O. —This is the blue vitriol of commerce; and is formed
by dissolving the protoxide in sulphuric acid.  It is very soluble
in water, and is extensively used in the arts.  Its color is a
fine blue.
488. Nitrate of Copper, CuO,N05, or, in crystals, CuO,NO5 + 811HO, is
easily formed by dissolving metallic copper in dilute nitric acid.  It does
not crystalize readily; and is deliquescent in the air, and exceedingly
corrosive.
489. Carbonates of Copper.-There are several carbonates of copper,
as azuirite and gr#een malachite, which are found native, and are made use
of as ores of copper.  They also contain water.  Green verditer, or mineral
green, is a hydrated subcarbonate, obtained by precipitating a solution
of blue vitriol with carbonate of potash or soda.
Silicates of Copper, more or less hydrated, are found native in the mineral
species called dioplase and chrysocolla.
490. Arsenite of Copper, or Scheele's green, is prepared by first dissolving
arsenious acid and pearlash together in warm water, and then pouring
into it gradually warm solution of sulphate of copper.  It is of a beautiful green color, and is much used in painting.  In commerce, it is called
Paris green.
Test of Copper.- Ammonia produces a deep blue color in diluted
solutions of any of the salts of copper, by which they may always be
distinguished.
491. Vanadium, V; Eq., 68.6.-This is a metal of rare occurrence,
being found only in some iron ores in Sweden, some lead ores in Scotland and Mexico, and recently in some copper ores from Lake Superior.
Molybdenum, MIo; Eq., 46. -Molybdenum  is found as a sulphide in
the mineral species called molybdenite, and also in other combinations.
It is a white metal, and has a density of 8.6.
Tungsten, W, (WVolfram); Eq., 95. —This metal is found in several
mineral species, especially the species called wolfram, which is a tungstate of iron and manganese.  It forms several oxides, chlorides, sulphides, &c.
Titanium, Ti; Eq., 25. —Titanium is found in several mineral species,
as rztile, anatase, and brookite. It is of a red color, and resembles copQurSTIONS.-487. What is the commercial name for sulphate of copper?  488. How is nitrate of copper formed?  489. What is said of the
carbonates of copper? 490. What use is made of arsenite of copper?
What test of copper is mentioned?  491. What other metals are mentioned as belonging to this group?
32




374                       MERCURY.
per. Its density is about 5'3. The native oxide is used in coloring
mineral teeth, so as to imitate the color of natural teeth.
Uranium, U; Eq., 60. —Uranium  occurs in several species as pitch,
blende, urcnite, &c. Many binary compounds of it are known, as well as
some of its salts.
Columbium, Cb, is the name given to a metal found in the mineral
species called columbite, which is obtained at Middletown and Haddmll,
in the State of Connecticut.
Tantalum, Ta, is a metal very similar to the preceding, which is obtained from the European mineral, tantalite. Little is really known of
these two metals last mentioned. The existence of the two metals named
pelopium and noriumn (Table, p. 145), is doubtful.
GROUP VI.
MERCURY
SILvrR
SILvERD    iXoble metals, whose oxides are reduced by a red hleat.-No
PLArTINUM    0one of them, except osmium, is capable of decomposing
OsPATINur    water under any circumstances.
IRIDIUM        The oxides of iridium and ruthenium,  and some of those
PALLADIUM'l  of osmium, are not perfectly reduced by heat, without the
RHODIUnM     presence of carbon, or some deoxydizing agent.
RUTHrrENIUMI J
MERCURY.
Symbol, Hg (Tlydrar/gyrte); EY             t O0; ivalnt 100; Densiy, 13 6.
492. History and Preparation.-Mercury, or qcuickcsilver, is
one of the seven metals of the ancients.  It is sometimes found
in its metallic state; but most of the mercury of commerce is
reduced from  the native sulphide, called cinnabar.  It is not
very generally diffused, there being but few mines that afford it
in any considerable quantity.  Most of the mercury used in this
country comes from  Spain; but it is obtained also in Germany,
Siberia, in Southern Asia, and in California.
The metal is extracted from the native sulphide either by
roasting it alone, so as to oxydize the sulphur and sublime the
mercury; or by heating it with lime.
QUESTIONS.-What use is made of the native oxide of titanioum?  How
are the metals of Group VI. characterized?  Name the metals of this
group. 492. Was mercury known to the ancients? By what other nanmer
is it Iknown? From what ore is it obtained? What is the mode of exC
tracting the metal from the native sulphide?




M ER CURY.                           375
-Besides the native compound above mentioned, there are other ores
of the metal, but they are found only in small quantities.
493. Properties.-  Mercury  is distinguished from  all other
metals by being liquid at ordinary temperatures.  It is white as
silver, and has a brilliant lustre.  Cooled to — 400, it freezes or
becomes solid, and is then very malleable, and nearly the color
of lead; at 6620, it boils and forms a colorless vapor, the density
of which (air being 1) is 6'976.  At lower temperatures, even as
low as 700, it gives off vapor, as is shown by the whitening of
pieces of gold-leaf suspended above it in a close glass bottle, and
by its action upon the iodized silver plates in the Daguerreotype
process.
The best method to obtain solid mercury is by means of solidified carbonic acid (58).  A portion of the solid acid is made in
the form of a ball, with a cavity in the upper side to receive the
mercury, and the whole enveloped in cotton to protect it from the
atmosphere.  In a few minutes the mercury will be solid, and
may be preserved in this condition for several hours with a very
small quantity of the solid acid.  The metal is also readily frozen
by a mixture of the solid acid and ether.
By slow cooling, mercury formls crystals belonging to the
monometric system.
494. Mercury is usually imported into this country in strong iron
bottles; and generally is very pure, and serves for every purpose without
purification.  In this state it is scarcely oxydized by the atmosphere,
but as it is capable of dissolving other metals, as tin, lead, silver, and
gold, by use in the laboratory it often becomes contaminated with them,
and thus is more liable to become oxydized, as will be shown by a pellicle
of oxide floating upon its surface. In this state, a portion will adhere to
the fingers, or other substance, when dipped in it; and it does not roll in
perfect globules over the surface of other bodies, like pure mercury.
To purify mercury, several processes are resorted to;-one method is
to pour it into a bottle with some sulphuric acid, or dilute nitric acid,
which oxydizes and dissolves the foreign metals. It should stand in the
bottle several days, and be frequently shaken to expose all the metal to
the action of the acid. At the proper time, the mercury is to be removed
and washed with water.
QUrSTIONS. —493. Describe the properties of mercury.  Give its freezing and boiling points. Does it evaporate at temperatures below its
boiling point?  -low may it be solidified?  494. What other metals will
mercury dissolve?  How may it be known when other metals are held in
solution in it? Describe the method of purifying mercury.




376                        M:E RCURY.
Another method is to distil the
mercury, by which it is separated
perfectly from silver, gold, and tin,
but not from. arsenic, zinc, or cad-,  __   _         b-y        mium, which are also volatile.  To
distil mercury, a cast-iron vessel is
used of the form represented in the
figure.  When using it, the cover
should be well luted on, and the
tube kept cold by a constant stream
of cold water.
To obtain mercury of sufficient'x l',_-_  0   ipurity for use in thermometers and
Distillin;g Merciury.    barometers, and especially the latter,
it will generally be found necessary
to subject it to both of these modes of purification in succession, the
distillation being first in order.
695. The only acids that act on mercury are the sulphuric and
nitric acids.  The former has no action whatever in the cold;
but on the application of heat, the mercury is oxydized at the
expense of the acid, pure sulphurous acid gas is disengaged, and
a sulphate of mercury is generated.  Nitric acid acts energetically
upon mercury, both with and without the aid of heat, oxydizing
and dissolving it with evolution of binoxide of nitrogen.
496. Uses.-Mercury is made use of for many important purposes, in medicine, in the laboratory, and in the arts.  In the
construction of thermometers and barometers it is absolutely
essential, and for the mercurial bath, to enable the chemist to
collect and transfer gases that are absorbed by water.  In union
with various other substances it constitutes the bases of many
important medicines.   Several of these preparations will be
described in their proper places.
497. Amalgams. —  This term  is exclusively applied to the
alloys of mercury with the other metals.
Quicksilver unites with potassium  and sodium  when agitated
in a glass tube with that metal, forming a solid amalgam.  When
the amalgam  is put into water, the alkaline metal is gradually
QUESTIONS. —What will be necessary, in order to obtain mercury of
sufficient purity for thermometers and barometers?  495. What acids
only act upon mercury? Explain the action of sulphuric acid.  Of nitric
acid. 496. To what uses is mercury applied?  497. To what is the
nama amalgam given?




BINARY COIPOUNDS OF MERCURY.  377,xydized, hydrogen gas is disengaged, and the mercury resumes
its liquid form.
A solid amalgam of tin constitutes the silvering of lookingglasses; and an amalgam made of 1 part of lead, 1 of tin, 2 of
bismuth, and 4 of mercury, is used for silvering the inside
of hollow glass globes.  This amalgam  is solid at common temperatures; but it is fused by a slight degree of heat.
The amalgam of zinc and tin (90) is used for promoting the
action of the electrical machine.
Binary Compounds of Mercury.
498. There are two oxides of mercury, the gray oxide, which
is considered a suboxide, Hg O, and the protoxide, HgO, which
is of a red color, The suboxide, Hg,O, is readily prepared by
mixing calomel briskly in a mortar with pure potassa in excess,
so as to effect its decomposition as rapidly as possible, and then
washing the precipitate formed in cold water, and drying spontaneously in a dark place.  This oxide is a black powder, and is
insoluble in water, but unites with the acids as a weak base.
The protoxide;, HgO, is the red precipitate used in medicine.
It is formed either by heating mercury nearly to its boiling point
in a vessel to which the air has access, or by cautiously heating
tihe nitrate so as to expel the nitric acid. The latter mode is the
one usually adopted. It is usually seen in very small, shining,
crystaline scales, which have a brick-red color. Heated to redness, it is decomposed, yielding mercury in the gaseous state, and
oxygen.  Red oxide of mercury is slightly soluble in water, and
gives it an alkaline reaction.
499. Subchloride of Mercury, HgCl; eq., (200 + 35.4 =)
235.4.-This compound, the well-known calomel used in medicine, is easily prepared by pouring a solution of nitrate of the
suboxide of mercury into a dilute solution of common salt, when
QuESTIONS. —What is it that forms the silvering of mirrors? 498. What
oxides of mercury are there?  How is the suboxide prepared? How is
the protoxide prepared?  What is it called? How is it affected when
heated? Is it soluble in water?  499. What is calomel?  Describe tho
mode of preparing it. To what use is it applied?
32*




378     BINARY  COMAPOUNDS  OF  MERCURY.
the calomel is precipitated as a white powder, which is insoluble
in water and the acids when cold.  It is sometimes found native,
and is called horn-quicksilver, or native calomel.  Its density is
about 7.
Calomel is sublimed without change by a moderate heat, and
may be obtained in small crystals.' It is usually seen as a white
powder, with a slight yellowish tinge; and may always be known
by instantly turning black as ink, when touched with a drop of
aqua ammonise, or solution of any caustic alkali.
This compound of mercury has long been extensively used in medicine,
and the estimation in which it has been held may, perhaps, be inferred
from the names by which it has been known at different times, and in
different countries.  The following are some of them: —lercurtius dzlcis,
draco miligatus, sublimatum duice, aquila alba, aquzila miligata, 72manna metallornm., paolchygmogogunzm  inerale, panchymogoguni qzeercetanus!
Calomel vapor has a density of nearly 82, and is composed of 1 vol.
of mercury vapor, a of a vol. of chlorine condensed to 1 vol. Thus,
1 vol. of mercury'vapor weighs 6.976
"   chlorine."     "   1.220
1 vol. subchloride vapor weighs 8-196
500. Chloride of Mercury, HgCl; eq., (100+35'4 -) 1354.
-Chloride of mercury —the corrosive subinmate of the pharmacopoeia-is obtained either by acting on mercury by nitrohydrochloric acid, or by sublimation from a mixture of sulphate of the
protoxide of mercury, and common salt.  The latter is the mode
usually adopted in practice.   Both the sulphate and the salt
should be perfectly dry and well mixed;-thc reactions will then
be as follows:
HgO,SO0  + NaC1 = NaO,SO, + HgCl.
The sublimation may be effected in a retort of hard glass over
a charcoal fire; and the operation should be conducted in such a
situation that all the fumes escaping -may be immediately conveyed away by a strong draft of air.
QUESTIONS.-Mlay calomel be sublimedl? How many volumes of its
constituents does one volume of it contain? 500. How is chloride of
mercury prepared? By what name is it known in pharmaycy? Deiscribe
the reactions when sulphate of mercury and common salt are used in its
preparation.




BINAtRY  COMPOUNDS OF  MPERCURY.    379
As corrosive sublimate is usually seen, it is colorless) semitransparent, and has a crystaline structure.  It has an acrid,
burning taste, and leaves a nauseous metallic flavor on the tongue.
It has a density of 6'5, fuses at 5090, and boils at 563~.  It is
soluble in 16 times its weight of water, and in alcohol and ether.
When its solution in water is agitated with ether, the latter
abstracts the bichloride, and rises with it to the surface of the
former; and it may thus be separated from many other substances
when contained with them  in solution.  Its aqueous solution is
gradually decomposed by light, calomel being deposited.
Applied externally, it is highly corrosive to the flesh; and
taken internally is a most deadly poison.  Albumen precipitates
it as an inert compound, and is therefore indicated as a proper
remedy in cases of poisoning with it.
501. The kyanizing (from the name of the inventor, Mr. Kyan,) of timbor consists in soaking it for a time in a solution of this substance, which
protects it from the attacks of worms and insects; and also, by combining
with the albumen contained in it, preserves it from decay.
The method given above for the preparation of calomel, though very
easy, is not the one usually adopted in practice; a better result is
obtained by mixing 100 parts (1 eq.) of mercury and 135'4 parts (1 eq.)
of corrosive sublimate, and subliming with a moderate heat, the whole
being converted into calomel. Thus,
IHg +- HgC1 = Hg2C1.
502. Iodides of Mlercury.-There are two iodides of mercury, corresponding in composition with the oxides and chlorides. The protiodide
is precipitated as a beautiful red powder by mixing together solutions
of iodide of potassium  and chloride of mercury.  The powder, after
washing and drying, may be sublimed by a moderate heat, but it then
becomes yellow. After cooling, the color gradually changes to red; and
the change is instantaneous if it is rubbed in a mortar.
Its vapor has the highest density of any known gaseous substance,
being 15'69. It appears to be composed of equal volumes of mercumy
vapor and iodine vapor, condensed to one volume.
1 vol. iodine vapor weighs 8.710
1  " mercury  "    6'976
1 vol. vapor of HgI weighs 15'692
QussIoaNs. —Describe chloride of mercury. Is it poisonous?  HIow is
a solution of it affected by albunlen?  601. In what does the kyaniziyng
of timber consist?  Describe the mode of preparing calomel (or subchloride) by using the chloride and metallic mercury.  502. What iodides
of' mercury are there?  Describe the protiodide, and the mode of preparing it. 1Wllhat is said of the density of its vapor? Of what is a volume
of the vapor composed?




380                 SALTS OF MERCURY.
503. Sulphides of 1Mercury. —There are two sulphides of mercury,
which are exactly analogous in composition to the preceding compounds.
The protosulphide, HgS, as we have seen, constitutes the chief ore of
mercury, being found native, as cinnabar.  It may also be prepared by
nlrt in several ways, and then forms the brilliant red pigment called
verzillion.
In vapor the density of this substance is about 5.4; and 1 volume of it
contains 3 of a volume of mercury vapor, and I of a volume of sulphur
vapor, as shown below:
vol. mercury vapor weighs (6976 X 3 =) 4651
I vol. sulphur  1"      c      6 (6  -4)   0.739
1 vol. vapor of HIgS weighs                5,390
As _ + -   - 2  -   6 +  7-, it is evident that the union of these two substrances is accompanied by an expansion; —it is the only instance of the
kind yet known.
The other binary compounds of mercury possess no special interest.
Sults of Mercury.
504. Nitrates of Mercury.-Nitrlic acid acts violently upon mercury,
a.,nd forms with its oxides several salts, differing from each other according as the temperature may be more or less elevated. or the'acid more or
less diluted.  Cold, dilute nitric acid acts slowly upon mercury, and forms
ivith it a salt of the suboxide, which crystalizes with two atoms of water,
and has for its formula HgI2O,NO5+t-2HO; but if the acid is hot, ncld of
the usual strength, a salt of the protoxicle is formed, which, when crystalized, has the formula, 21gO),NO5 + 2HO.  Still other nitrates of this
metal may be formed, but these are the most important.
505. Sulphates of Mercury.-Sulphuric acid acts but slightly upon
mercury when cold; but if heated, a sulphate of either the suboxide or
protoxaide is formed, according to the'temperature.  If 5 parts of sulphiuric acid are boiled upon 4 parts of mercury, sulphate of the protoxide,
HgO, SO3, is formed-the compound used (500) in the manufacture of corrosive sublimate.  Boiling water decomposes this sulphate, forming a
yellow basic salt, 3HgO,S0s, called tUpeth mnineral.
506, Chlorosalts of Xercury.- Protochloride of mercury combinereadily with other metallic chlorides, forming numelrous crystahlizable
salts, which by some have been called liydrarno-chloides.  Compounds
QUESTIONS. —503. What is said of the sulphides of mercury?  What is
vezrmillion?  Of what is one volume of vapor of HgS composed?  What
is said of the union of these twto substances?  504. What is said of the
nit rates of mercury?  505. What is said of the action of sulphulric acid
upon imercury?  506. Does chloride of mercury combine with other
metallic chlorides?  What are the compounds called?




SIL VER.                            381
of this character, with the chlorides of potassium, sodium, lithium, amnlonium, barium, &c., are made simply by mixing their solutions.  The
double chloride of mercury and ammonium was formerly used in medical
practice, under the name of salt of alenzbroth.
SILVE R.
Symbol, Ag (Ar~gewut.u); Eztivcaent, 108; Densitg, 10-5.
507. History.-This metal was known to the ancients.   It
frequently occurs native in  silver mines, both  massive and in
octahedral or cubic crystals.  It is also found in combination
with gold, tellurium, antimony, copper, arsenic, and sulphur.
In the state of sulphide, it so fiequently accompanies galena, the
chief ore of leadc that the lead of commerce is rarely quite free
from traces of silver.
3Most of the silver mines, which afford the metal at the present
day, are in South America and Mexico; but in smaller quantities
it is obtained in several countries of Europe, and other parts of
the world.
Nearly all the silver obtained from the mines at the present
time is found native, or is extracted from the sulphide; but there
are many other mineral species which contain the metal.
508. Preparation.-When metallic silver is contained in small
particles, disseminated through the ore, it is extracted by triturating the ore in fine powder with mercury, which dissolves the
silver, and separates it at once from the mass, as an amalgam.
The amalgam  is then subjected to pressure in leather bags, by
which a portion of the mercury is separated, and the remainder
is expelled by heat.  This is called the process of acnalcamaction.
Other ores of silver require to be treated differently, but the
numerous processes adopted cannot be here described.
Silver is purified from small quantities of othemr metals present,
except gold, by the process of cupellation, which has been practised from  a very remote age.  The process depends upon  the
QuEsTIONs.-What is salt of alem?zbroth?  507. Has silver been long
kilown?  With what other metals is it found associated?  From  what
cres is most of the silver of commerce extracted?  508. Describe the'ot'de of extracting silver fr'om its ores by the amalgamating process.




382                         SI LV ER.
fact that the metals (except gold) which are usually in combinaQ
tion with silver, as copper, lead, tin, &c., are more oxidable than
silver, and therefore when the alloy is kept for a time at a high
temperature in the open air, these metals are oxydized, and the
silver left perfectly pure.  In large refineries, the oxide, as it is
formed, is blown off by a bellows, so as to expose constantly a
fresh surface to the air; but in small operations, as in the testing of coin or plate, the
cupel proper is used, which is made of bone_         earth, of the form of a small cup, as represented
Cupel.      in the figure.  This has the peculiar property
of absorbing the mixed oxides as they are formed, and thus the
necessity of using the bellows is avoided.  For
small operations, cupels are made about an inch
in diameter, and half an inch deep.  A vertical
Section of Cupel.   Section is shown in the annexed figure.
509. We will suppose the object is to test some coin or plate,
which contains with the silver some copper, and perhaps a little
tin or lead.  A  small piece of the alloy is accurately weighed,
and placed in the cupel with 10 or 20 times its weight of pure
lead, and subjected to a strong heat, in such a manner that the
air shall have constant access to it.  When it becomes sufficiently heated, oxydation of the  lead and other metals commenc.es, and the mixed oxides being absorbed as they are formed,
after a little time the silver is left perfectly pure.  The cupel
with the silver is then removed, and when cold the button of
silver is detached and again carefully weighed.
The heating is usually conducted in a muffle, placed
in a proper furnace, so as to exclude dust and smoke,
but allow the access of air.  The muffle (see figure)
Muffe.       is in fact a small oven, made of fire-clay, and is
placed in the furnace so as to be entirely surrounded
by the burning fuel, as shown in the figure on next page, which represents a vertical section of the furnace through its centre, with the muffle
in its place.  M is the muffle, with several cupels in it; A, B and C
openings, which may be closed at pleasure by means of fire-brick doors,
A, B, C, prepared for the purpose.  To insure perfect success in the
QUESTIONS.-509. Describe the process of cupellation.  Of what is the
cupel formed?  What purpose does it serve?  Describe the mulffie.




SILVER.                            883
operation, attention is required to various
particulars, which cannot be here given in
detail. 
Alloys of gold, subjected to the same
process, are purified firom all other metals
except silver and platinum.
510. Another mode of testing alloys
of silver, called the wet method, is to
dissolve the silver alloy in nitric acid,
and precipitate the silver by a standard
solution of common salt, previously prepared with accuracy.  This solution is
made of such a strength, that 1000 parts'
of it, by measure, will precipitate exactly
1000 parts by weight of pure silver; and
the proportion of silver in the alloy will         i           I Jj
of course be determined by the number
of parts of the solution required to pre-.
cipitate it.  This is the mode practised
at the United States mints, to determine......
the fineness of coin. 
This method cannot be used when the                       t
alloy contains a metal, as mercury, whose 
chloride is insoluble.                    Section of Furnace and Muffle.
511. Properties.-Silver is a soft, white metal, and is very
malleable and ductile.  It has a brilliant lustre, and is susceptible
of receiving a very fine polish.  It is not acted upon by the
atmosphere or by moisture, but is readily blackened by sulphur.
Articles of silver often become tarnished, merely by the sulphurous
gases which are diffused from the fires in houses in which mineral
coal is used for fuel.
Its melting point is about 18730, and if kept some time in
fusion it absorbs oxygen in large quantity, which is given off again
when the metal cools.
Silver is attacked by sulphuric acid only by the aid of heat,
but is freely dissolved by nitric acid, even when cold.
Silver is used in every country for many important purposesfor coin, and for manufacture into various articles of utility or
ornament; but to render it more stiff and hard it is always
alloyed with a portion of copper.
QucrESTIONS.510. Describe the wet method of testing alloys of silver.
611. Describe the properties of silver.  What acids act upon it?  For
what purposes is silver used?




884L       BINARY  COMPOUNDS OF  SILVER.
The standard of purity for silver coin varies in different countries;
but the coin of the United States contains 900 parts of pure silver an:ld
100 parts of copper;-that is, one-tenth part of the weight of the coin is
copper, except the three-cent piece, of which -3ths are silver and  -th
copper.
At the present time, the largest silver coin issued froml the United
States Mint is the half-dollar, which is required to weigh 1092 grai-ns;
the weight of the smaller coins being in the same proportion, except that
of the three-cent piece, which is 128 grains.  The quantity of pure silver
in the half-dollar is, according to the above, 172-8 grs. =192 —19'2.
This gives as the value of pure silver $1,38.8 per ounce.
The value of coin is always estimated in proportion to the amount
of pure metal it contains, no attention being paid to the alloy.  It is
remarkable that the addition of copper scarcely produces any change in
the brilliant white color of silver, provided it does not exceed about oneeighth of the latter metal.
Silver combines with other metals, forming alloys, which, however,
possess no particular interest.
Binary Conmponds of Silver.
512. Oxides of Silver.-Silver forms with oxygen three compounds, a
suboxide, Ag20, protoxide, AgO, and binzoxide, AgO2; but only the protoxide
is important.  This is thrown down as a dark-colored powder, when solution of caustic potash is poured into a solution of nitrate of silver. IHeated
to redness it gives up all its oxygen, and pure silver is obtained.  It forms
the base of all the oxysalts of silver;-is slightly soluble in water, but
very soluble in aqua ammoenie.
By digesting this oxide for a time in concentrated aquna ammoniei, a
black compound is formed, which is highly explosive, sometimes calledl
fulnminating silver. Its composition has not been satisfactorily determinedl.
The most probable opinion is, that it is a nitride of silver, NAg3, formed
by the reaction:
3AgO + NI- = NAg3 + 3110.
513. Chloride of Silver, AgCl; eq., (108 + 35 4=) 143-4.-This compound is occasionally found as a natural production, and called horsn
silver, and is easily formed artificially, by pouring solution of common
salt into a solution of nitrate of silver.  Formed by this mode, it is a
beautiful white powder, which, however, soon becomes purple in diffused light, or black if exposed to the direct light of the sun, or if warmed
before a fire.  It is insoluble in water, but soluble in ammonia and
hyposulphurous acid.
QUESTIONS.-What proportion of the silver coin of this country is silver?  What is the alloy?  What is the largest silver coin now issued
from  the United States Mint?  What does this give as the value per
ounce of pure silver?  In estimating the value of coin, is any allowance
made for the value of the alloy used?  512. What oxides of silver area
there?  Which of these constitutes the base of the salts of silver?
513. Describe the chloride of silver.  I-low is it prepared artificially?




SALTS OF  SILVER.                         385
Nascent hydrogen reduces it to the metallic state by absorbing the
chlorine to form hydrochloric acid. To effect the recluction, the chloride
is covered with water acid-alated with sulphuric acid, andlg  pieces of zinc
introduced, and the whole occasionally stirred.  The metallic silver is
obtained in fine grains.
Iodide of Silver, AgI, is found as a natural production, and may also
be formed by precipitation from solution of nitrate of silver by iodide
of potassium.
Sulphide of Silver, AgS. —This compound is found in nature, alone,
and in combination with other metallic sulphides, particularly sulphide
of lead, in the ore called argentiferous yalena.  Sulphide of silver may also
be formed artificially by several processes.
Salts of Silver.
614. Nitrate of Silver, AgO,Na5. -  This is the only salt of
silver of any practical importance, and is well known by the
name of lunar caustic.  It is usually sold in small sticks, which
are wrapped in paper, but may also be obtained in beautiful
white, tubular crystals.  The sticks usually contain a portion of
nitre, which has been melted with it when cast in the moulds.
Nitrate of silver is formed by dissolving silver in nitric acid,
diluted with twice its weight of distilled water.  It is soluble in
one-half its weight of boiling water, and its own weight of cold
water.   It is the basis of indelible inkc, as it is called; but
writing done with it, and stains made by it, may be removed by
solution of cyanide of potassium.  Nitrate of silver is very caustic
to the flesh, and is used in medicine as a cautery.  From its solution, metallic copper precipitates the silver as a fine powder; by
mercury, the silver is thrown down in an arborescent form, which
has been called the arbor.Diance.
Sulphate of Silver, AgO,SO,, may be formed by boiling sulphuric acid upon metallic silver.  It is a colorless salt, slightly
soluble in boiling water.
QUESTIONS. -Describe the mode of reducing the chloride by means
of zinc and oil of vitriol. What other binary compounds of silver are
mentioned?  514. What is lunar caustic?  Describe its properties.
W1sat use is made of it?




G o L D. 
GOLD..m bol~, Au (Aurum.); Eluivalent, 19S; De~nsity, 19.26.
515. History. -- Gold appears to have been  known to tle
earliest races of men, and to have been esteemed by them as
much  as by the moderns.   With the exception of the rare
mineral teliuride of gold, it has hitherto been found only in the
metallic state, either pure, or in combination with other metals.
It is sometimes found in quartzose rocks, but more frequently in
alluvial depositions, especially among sand in the beds of rivers,
having been washed by water out of disintegrated rocks in which
it originally existed.
Though usually found in irregular rounded lumps and grains,
it is sometimes obtained in crystals of the monometric systeml as
Crystals of Gold..represented by the accompanying figures, taken from the American
Journal of Science.
Gold is obtained at the present day in large quantities in
California, Australia, and some parts of the Ural MBountains,
and less abundantly in Hungary, and other countries of Europe.
In small quantities, it occurs in Georgia, North Carolina, and
Virginia.
518. Preparation.-As gold exists in its ores in the metallic
state, it is generally separated from them by the process of anealQUI,:sTro-Ns.-515. Give the history of gold. In what situations is it
found?  Is it occaIsionally found in crystals?  516. Describe the me3,cle
of separating silver from gold, called quartation.




GOLD.                           387
gamation, similar to that already described for obtaining silver,
by which means it is separated from all other metals except silver.
To remove -this, so much silver must be added to it that the gold
shall constitute but a fourth of the whole, and the mass boiled in
nitric acid, which then readily acts upon it, dissolving out all the
silver, and leaving the gold in a state of purity.  This process
has been called quzartation, from  the circumstance that the proportion of gold, in order that'the nitric acid shall dissolve out all
the silver, must not exceed a juarter of the whole mass.  Other
metals, except silver, may also be separated from  it by cupollation (508).
To prepare absolutely pure gold, a piece of coin may be dissolvedl in aqua regia, and precipitated with solution of sulphate
of protoxide of iron.  The reactions are as follows:
AuC3l  + 6FeO,SO3 = Au + Fe2C,1 + 2(Fe20,,3S0,).
The gold thus obtained is in a minutely divided state, and is of a
purplish brown color.  It is to be collected on a filter, and washed
with very dilute hydrochloric acid, and fused with a little borax
and saltpetre.
517. Properties.-Gold is readily distinguished from  all other
metals by its brilliant yellow color, and by its great malleability
and ductility. It is capable of being beaten out into leaves so
thin that light may be transmitted through them, which then
appears of a greenish yellow color.  It is not acted upon by air
or moisture, though exposed to their influence for ages; nor is it
oxydized by being kept in a state of fusion for any length of time.
When intensely heated by the galvanic current, or by means of the
compound blowpipe, it burns with a greenish blue flame, and is
dissipated in the form of a purple powder, which is supposed to
be an oxide.  Selenic acid, aided by heat, dissolves it, and a
mixture of selenic and hydrochloric acids, without heat; but its
proper solvent is aqua regia, which is a mixture of 1 part of nitric
and 2 parts of hydrochloric acid.  It fuses at about 2016~.
QuTJsTIONs.-Whly does the process for separating silver from gold here
described receive the name quarltation?   oI-w may absolutely pure gold
beo prepared?  517. How is gold distinguished from the other metals?
Describe soime of its propertie;. What is the only proper solvent of gold?




388         BINARY  COMI POUNDS OF  G OLD.
5:8, Gold and silver, from the estimation in which they have been held,
have been long known as the "precious metals;" and it is usual to estimate their purity in carats.  A carat is to be understood as oath part
of the mass; and a piece of gold or silver is 14, 18, or 20 carats fine,
when so many 24ths of the whole are fine metal, the rest being alloy.
But in the Miint of the United States, their fineness is estimated in thousanLdths: thus, gold or silver is said to be of the fineness 654, 789, 921,
or 99.4 thousandths, when so many thousandths of the whole mass con
sist of pure metal, the rest being alloy.  The alloy of silver is always
copper, but the alloy of gold may be either copper or silver, or a mixture
of the two.  Pure gold is so soft that some alloy is always needed to give
it the proper stiffness, and to prevent too rapid wearing.  In the gold
coins of this country, one-tenth part is alloy, which is a mixture of silver
and copper.  The gold eagle of the United States weighs 258 grains, of
which 25 8 grains are alloy.  The value of standard gold is therefore
estimated at $18.604 per ounce, and that of pure gold at $20.671 per
ounce.
Nativo gold is almost always alloyed with silver, but the proportion
of this metal is very variable.
Gildling consists in coating over the surfaces of bodies with a thin film
of gold.  Articles made of metal were formerly gilded by applying to
their surface, properly cleaned and smeared with nitrate of mercury,
amalgam of gold, and then expelling the mercury by heat; but this mode
has been entirely superseded by the electrotype process, heretofore (116)
described.  In both cases the surface of gold requires to be burnished.
Articles made of non-metallic substances are gilded by a coating of
gold leaf.
Binary Copozclndsc of Gold.
519. Oxides of Gold,-There are two, and perhaps three, oxides of gold;
but the teroxide, AuO3, alone possesses any special importance.  It is of a
yellow color when first formed, but becomes black when all the water is
expelled.  It is used in coloring glass and porcelain purple.  In some
cases it seems to act the part of a feeble acid, and has been called
auric acid.
520. Chlorides of Gold.-There are two chlorides of gold; the terchloride,
AuC13, the one usually seen, is formned when gold is dissolved in aqua regia.
By evaporating the solution carefully, the chloride may be obtained as a
solid, which is very soluble in water, alcohol, and ether.  Solution of
chloride of gold is very easily decomposed by green vitriol, and by organic
QUESTIONS.-518. Why have gold and silver been called the precious
metals? How has the fineness of these metals, or rather alloys of them,
usually been estimated?  What is meant when an article of gold or silver
is said to be 18 carats fine?  How is the fineness of these metals estimated at the United States Mint?  What is the alloy used for the gold
coins of this country? What is the weight of the United States eagle?
What does this give as the value per ounce of standard gold?  Of pure
gold?  How is gilding performed?  519. What oxides of gold are there'?
520. What chlorides?




PLATINUM.                              389
srbostances, Protocllorilde of tin forms with it a beautiful Purple powder,
called purple of Cassi'us.
Aqua ammonia precipitates, from  solutions of terchloridle of gold, a
fulminating compound calledl fulmizating gold, of uncertain composition.
Salts of Gold.
521. The oxides of gold do not unite as bases with the acids, but the
telioxidce, as an acid, combines with bases, forming some unimportant
tsalts, which are called aturates.
Chlorosalts of Gold. —Terchloride of gold combines with many other
n met-llic chlorides, like the chloride of mercury, forming a series of clloroBsalts, sometimes called azuo-chlorides.
PLATIN U M.
Symbonl Pt; Eqtivalent, 99; Density, 21'5.
522. H]-istory. —Platinum  was first recognised as a distinct
metal, in  1741, but was not described  until 1749.   It has
hitherto  been  obtained  chiefly  from
Brazil, Peru, and somue other parts of
South  America,  and  from   the  Ural
Mountains.   It occurs only in the metallic state, associated with other metals,
as gold, silver, lead, palladium, osmium,
iridium, and rhodium.
523. Preparation.-To prepare pure
platinum, the  native  grains, or commnercial platinum, are dissolved in boiling
cqua regia, and, after standing for a time,
the clear solution is poured off, and the
platinum  precipitated by solution of salarnnmoniac,  as a double chloride of platinum  and ammonium.  By heating this
precipitate, both  the chlorine and am-             -
monia are  expelled, and  the  metallic   Platinum-in-Aqua Regia
QrcEsToNs. —How is purple of Cassius formed?  521. What is said
of the chlorosalts of gold?  522. Give the history of platinum.  What is
the state in wlich it occurs?  523. Describe the mode of preparing pure
platinum.
3 *




390                      PL  A T I N UI.
platinum remains as platinum  sponge, which, when treated with
hot water, appears as a dark gray mud.
This is now pressed in a hollow cylinder, by which means the
particles of metal are made to adhere, so that the disc thus
obtained may be carefully heated, and hammered on an anvil.
The metallic grains now become firmly welded together, and the
mass may be worked in any desired form.
52%,. 3rroperties.-Platinum  is a white metal, much resembling
silver, but of a darker color, and of inferior lustre.  When pure,
it is very malleable and ductile.  It is the most dense substance
known to man (except, perhaps, iridium), but is quite soft; and
pieces of it, when heated, may be welded like iron, though not
so easily. No single acid attacks it, but it is soluble in heated
aqua regia.  By heated nitre, or potassa, or soda, it is oxydized.
It cannot be melted by the most intense heat of the hottest furnace; but may be fused by the compound blowpipe.  When a
large surface of the metal is exposed to a mixture of oxygen and
hydrogen, it has the singular property of causing them to combine, either silently or by an explosion.  It acts in this way more
readily when used in the spongy form (200, 523), as precipitated
from its solution by sal-ammoniac.
Plathingu, blacc, in which the metal is in a still more finely
divided state, acts energetically in the same manner, causing the
rapid union of various gases besides oxygen and hydrogen, when
submitted to its influence.  This form of platinum
is prepared by electrolizing a dilute solution of
chloride of the metal, or by boiling a solution
of the chloride mixed with carbonate of soda and
sugar.
If a coil of platinum wire, recently ignited, be sus- /-   pended in a deep glass, containing a little ether at the
bottom, it will instantly become incandescent, and glow
Wre of Plati- with a red heat, until the ether is entirely dissipated.
alm over Ether. The same effect may be produced by placing a coil of
QUESTIONTS.-How are the particles of finely divided metal made to
unite so as to form a solid mass?  524. Describe the properties of platinRun. By what alone is it dissolved? How is it affected by heated nitre
or potash?  How is a mixture of oxygen and hydrogen affected when
expotsed to a large surface of this metal? What is said of plateizu  black
in this connection?  Describe the experiment with a coil of platinum
wire and ether.




BINARY  COMPOUNDS  OF PLATINUM.    391
small platinum wire over the wick of a spirit-lamp,
and after lighting it, suddenly extinguishing the flame.
The wire will continue at a red heat until all the
alcohol is consumed. Such a lamp (called a fiameles    /,
lamp) is represented in the accompanying figure.
525, Uses.-Platinum  is of great importance
in the laboratory, and is much used in the arts,
especially for retorts for condensing (261) sulphuric acid.  Its present value in the market is   amees Lamp.
about half that of gold.  It was formerly issued
as coin by the Russian government, but the practice has been
discontinued.
Binarly Compounds of Platinum.
526. Oxides of Platinum. —Platinum forms with oxygen two compounds,
the protoxide, PtO, and theperoxide, PtO2, both of which are feeble bases,
and unite with sdme of the acids to form salts.
Chlorides of Platinum. —Two chlorides of platinum are known, analogous in composition to the oxides. The bichloride, PtC12, is the most
important of all the compounds of this metal, and is obtained by treating
the metal with boiling aqua regia, and carefully evaporating, to expel the
excess of acid. It is much used in the laboratory.
Sulphide of Platinum, PtS, may be formed by heating platinum-filings
in vapor of sulphur.
527. Salts of Platinum.-The salts of platinum, at least the oxysalts,
are not important.  Oxalate of the protoxide, and sulphate and nitrate
of the binoxide, are known.
Chlorosalts of Platinum.-The bichloride of platinum  combines with
other metallic chlorides, forming a series of chlorosalts, called also
piatino-chlorides.
528. Osmium, Os; Eq., 99-5.-This rare metal is in combination with
platinum and iridium;-with the former in the so called native platinum
grains, and with the latter in the mineral species called iridosmine. It is of a
grayish color, and metallic lustre; is slightly malleable, and has a density
of about 10.  It combines readily with oxygen when heated, and is
attacked by nitric acid, which converts it into osmic acid.
Small grains of the native iridosmine are used for the tips of gold
pens, because of their hardness and capability to resist the corrosive
action of the ink.
QESTIONS. - Describe the flameless lamp.  525. To what uses is
platinum applied?  526. What oxides of platinum are known?  What
chlorides?  I-low may sulphide of platinum be formed? 527. Are there
any important salts of platinum? 528. What is said of osmium? What
use is made of the native grains of osmium and iridium?




392     BINARY  CO MPOUNDS OF  PLATINUM.
There are known no less than five oxides of osmium, viz., OsO, Os20
OSO2, OsOs, and OS04; of which the last two possess acid properties, and
are called the osmious and osmic acids.
Two chlorides only of osmium are known, a protochloride and a bichloride.
529. Iridium, Ir; Eq., 99.-Iridium, as stated above, is found chiefly
in combination with osmium.  It has not been obtained in a malleable
state, but only as a hard compact mass; and its density cannot therefore
be well determined, but by some it is believed to exceed that of platinum.
It is not attacked by nitric acid, nor even by aqua regia when pure, but
at a red heat enters into combination with chlorine, with which it forms
twlo compounds, the protochloride, IrCl, and the bichloride, IrCl2.
530. Palladium, Pd; Eq., 53-3. —This metal, often contained in platinum ores, is obtained chiefly from a native compound of this metal with
gold, found in some parts of South America.  It is nearly as white as
silver, and scarcely less fusible than platinum. It is malleable and ductile,
and receives a fine polish under the burnisher.  Its density is 11'8.
Palladium is used for the construction of the beams for delicate balances,
and also for the graduated scales of astronomical instruments.
531. Rhodium, Rh; Eq., 52 2. —Rhodium, which receives its name from
tlhe rose-color of some of its compounds, is contained in small quantities
in most platinum ores, and is sometimes found in combination with gold.
It is of a gray color, and even more infusible than platinum.  It is
attacked by aqua regia only when alloyed with platinum, or some other
metal.  Its density is 10-6.
Ruthenium, Ru, is the name given to a metal recently discovered in
some platinum ores.  In its general properties it resembles iridium.
QUESTIONS. —What oxides of osmium  are known? 509. In what is
iridiumn found?  530. Describe palladium.  What use is made of it?
531. Describe rhodium.  What is said of ruthenium?




PAR T IV.
SPECIAL  CIIEMISTRY-O R  ANIC.
GENERAL PROPERTIES OF ORGANIC BODIES.
532. Introduction.-In the preceding part of this work, we
have traced the chemical history of all the elementary substances
at present known, and that of many of their most important compounds, as they are produced by the action of their affinities,
uncontrolled except by the agencies of heat, light, and electricity;
but we have now to discuss altogether another class of compounds,
called organic, because produced almost exclusively by the organs
of plants and animals, or derived from substances so produced.
Organic Chemistry, therefore, is that branch of the general
science of Chemistry which treats of the history, properties, and
transformations of animal and vegetable substances.
These are always compound, and differ from inorganic or
mineral compounds chiefly in their origin, and in the circumstance that most of them are of a more complex composition.
533. Organic and Organized Bodies —There is, however, a
certain class of organic bodies,-called organized bodies, —whose
essential physical properties are altogether peculiar.  These are
always insoluble, and incapable of crystalization, and exhibit an
organized structure, often visible to the naked eye, and always
apparent under the microscope.  To this class belong all the
proper tissues of the animal and vegetable systems, constituting
the organs by which all their various functions are performed.
Sugar, gum, alcohol, and urea are organic substances, the twc
QuESTIONS.-532. What has been treated of in the preceding parts
of this work?  What are now to be treated of? Define Organic Chemistry. How do organic bodies differ from inorganic? 533. What are
orlganized bodies? What is said of sugar, gum, &c?
(393)




894               CDGE NERAL  PROPERTIES
former being found ready formed in plants and sometimes in
animals, and the two latter, being derived usually from  substances so produced, but they
are  not organized.   On  the
other hand, the cellular tissue
of wood, the pith of an elder
tree and the skin of an animal,
~~~ ~         are organized; and their pecu-'o -   t: [her~4'~-~~,~~ a~'~ 1  liar structure is apparent to the
eye, at least when aided by the
microscope.  The figure in the
margin, from Regnault's Chemistry, represents a cross section
lPith of Elderonof the pith of the elder, as seen
Pith of t Eider.
under the microscope.  This exhibits a peculiar regularity of structure, which, however, is not
common;-the structure of two different organized bodies seldom
presents any striking similarity.  Of
the next two figures, the first represents a microscopic view of a longiStalk of Asparagus.               Cross Section of Same.
tudinal section of a stalk of asparagus, and the second a cross
section of the same.
534. Vitality.-In the production of organic bodies, the simple
affinities of the particles of which they are composed are overQuesTIons.-What is said of the various tissues of the system?  I-Tow
maiy the organized structure always be seen?  What is represented by
the figure in the margin?  What by the next two figures?  534. By
what are the atfinities of matter controlled in the production of organic
compounds?




OF  ORGANIC  BODIES.                       895
ruled or controlled by another power or force, called the viteat
power, vitcality, or the principle of life.  Its influence is absolutely essential for the production of most organic compounds,
which, it is believed, can never be formed by the simple operation of the ordinary affinities of the elements of these compounds.
And it follows, as a necessary consequence, that after death, that
is, when this principle has ceased its influence, and the simple
affinities of the elements of an organic compound are left uncontrolled, they will show a disposition to break up, and re-arrange
themselves in a new order. In this way the old compound is
destroyed, and perhaps several new ones formed; or the simple
elements may be entirely set free.  This is what is termed the
spontaneous decay, or putrefaction of a substance.  Often this
process is affected by the presence of the atmosphere, and is
always much influenced by the temperature, and other circumnstances.
Although many organic compounds are found, as such, in the bodies
of plants and animals, by far the greater number are produced by the
actions of the various reagents, as the acids, alkalies, and salts, either
cold or aided by heat, upon these compounds. Thus, sugar and starcel
occur abundantly in plants, but from them, by the action of reagents, a
long list of other compounds are produced, which are never found in thle
plants themselves. Alcohol, the almost innumerable ethers, and mally
acids, are of this kind. Some compounds, as acetic and oxalic acid,.are
found ready formed in organic bodies, and may also be produced by the
action of reagents upon other organic substances.
But it is not to be understood that all organic substances are equally
liable to decay; some of them, as sugar, wood, and gum, of vegetable
origin, and gelatine, of animal origin, if kept dry, may be preserved
apparently for any length of time.
The chief elements of organic bodies are carbon, hydrogen, oxygen,
and nitrogen, which are combined in different modes, and in different
proportions; but besides these some organic substances also contain sulphur, phosphorus, chlorine, calcium, potassium, sodium, magnesium,
iron, silicon, &c.
Some few organic compounds have been formed artificially, that is,
without the aid of the vital principle; but not any organized body.
QUESrIONS.-Is the influence of this principle of vitality essential to
the production of organic compounds?  Why, after death, do most
organic substances spontaneously decay? Are most organic compounds
found ready formed in the bodies of plants and animals?  What is said
of alcohol and the ethers? May some organic bodies be preserved for a
long period? What are the chief elements of organic bodies?




396              GENERAL PROPERTIES
535. Molecular Structure of Compounds.-It is well known
that two compounds, exactly the same in composition (172), often
differ very considerably in their properties. This difference is
believed to be occasioned by differences in the mode of arrangement of the particles in the compounds, or, in other words, in
their molecular structure. In general, while we understand well
the elements of many compounds, we really know little of the
mode in which these elements are grouped together in any
particular case.  We know, for instance, that the equivalent
of sulphuric acid, SO,, contains I atom of sulphur and 3 atoms
of oxygen, but we cannot say whether these are grouped as
S+30, SO + 20, or SO,2+ O  for these three modes are all alike
possible. Here it would seem that there can be only three modes
of combination, but in more complex compounds the number of
possible modes may be greatly increased.
This supposed difference in the mode of combination or grouping of the
atoms of a compound, may be represented to the eye by means of a diagram. Thus, let us suppose that we have a compound of two simple
Modes of Grouping.
subilstances, and that in the atom of the compound there are 8 atoms
of each of the elements;-representing the particles of one kind of matter by the dark squares, and the other by the light ones, the four figures
show as many independent modes of grouping. Now, as every independent mode of grouping of the particles may produce a new substance,
it is plain that we may thus have four substances, all having the same
ultimate composition, yet possessing properties altogether different.
536. Compound Radicals - Nomenclature.-Compound radicals are chemical compounds which are capable of performing the
functions of simple substances; they combine with elementary
bodies and with other compounds in the same manner as simple
QUESTIONS.-535. May substances having the same composition differ
in their properties?  How is this difference believed to be occasioned?
What is said of sulphuric acid in this connection? How is the supposed
difference in the mode of grouping among the atoms of a compound illustrated by the figure? 536. What are compound radicals?




OF ORGANIC BODIES.                           397
substances, and may often be substituted for these in the compounds of which they form a part.
One of the best known of these compound radicals is cyanogen,
C,N (316), which, as is shown by the formula, is a bicarbonide
of nitrogen. This group of atoms, it is well determined, is capable
of combining with the metals and other substances in the same
manner as oxygen, chlorine, sulphur, &c., producing compounds
similar to the oxides, chlorides, &e., which are called cyacnidles.
United with oxygen it forms cyanic acid, with hydrogen it forms
hydrocyanic acid, &c.  So through a long series of other compounds, this group of atoms is found everywhere performing the
functions of a simple substance.
Other compound radicals which have been determined are metlhyle,
C2T13; ethyle, C4H5; butyryle, C6H,; valyle, CsHg; amyle, Cl0H1l, &c.
Still other compounds of the same character, but having a more comnplex composition, are benzyle, C 14I502; cacodyle, C4H6As; sfanmethyle,
C4H5Sn; zincmethyle, C2H3Zn; stibmetihyle, (C2I3S)3Sb, &c.
537. That these groups of atoms, and many others, do enter, as such,
into composition with the simple substances, and with each other, and
are capable of being transferred by single or double decomposition from
one compound to another, are facts too well established to be controverted. All those mentioned above, except perhaps benzyle, have also
been obtained in a separate state; and many that have not been thus
obtained may, with gr at probability, be assumed as having a real
existence.
Considering the existence of these groups denominated compound
radicals as fully established, it will be seen at once that it furnishes
a ready mode of classifying organic compounds, and also for forming for
them a systematic nomenclature.  Thus, if we take ethyle, C4HX, as the
basis or starting point of a series, we have for its binary compounds the
oxide, chloride, iodide, sulphide, &c.; and for salts of its oxide, the
hyponitrite, nitrate, acetate, &c., as follows, viz.:
Binary Compounds.
1. Ethyle............ C4H5.
2. Oxide of ethyle, C4Ht50, common sulphuric ether.
3. Chloride   "    C4HC1, hydrochloric      "
4. Iodide'    C4H5], hydriodic    "
5. Sulphide  "    C4H5S, hydrosulphuric'
Salts of Oxide of Ethyle.
1 Nitrite of oxide of ethyle, C4H150,NO4,  hyponitrous ether.
2. Nitrate    "       "   CsH50,NO5,  nitric "
3. Acetate    "       "4 C4H0,C4H303, acetic          "
QuEsTrIONs. — What compound radicals are mentioned?  537. Have
many of these groups have been obtained in a separate state?
34




398               ( GENERAL  PROPERTIES
The foregoing are given as examples only; —this series might be
extended much further, and many other series might be introduced, as
the methyle series, which would include the compounds of methyle, C2Hs3
analogous to the above, the acetyle series, the cacodyle series, &c.  A
nomenclature of organic compounds constructed on this principle has
been adopted by able and judicious chemists; but as there is no proof
that such a nomenclature truly represents the real molecular structure
of these compounds, we do not make use of it in this work.
538. A slight examination only is needed to show that most organic
compounds may be arranged in series in a variety of ways, each new
mode requiring or supposing a new molecular arrangement. Thus in
the compounds represented in the table above, if we commence with olefiant gas, or ethylene, C4H4, instead of ethyle, C4115, then we may consider the latter, C4H-=C411H4,H, as the hydride of ethylene, and ether,
C4H O —Ca4FH0, as hydrate of ethylene, hydrochloric ether, C4H1CC1
C4H,,HC1, as hydrochlorate of ethylene, &c.
539, The real mode in which the particles of organic compounds are
arranged (535), at least in most cases, has not yet been satisfactorily
determined; and it is therefore impossible, in the present state of our
knowledge, to fix upon a proper systematic nomenclature.  The same
may also be said of the formule used to represent these compounds.  A
distinction is often made between empirical and rational formulse, the
former representing the composition as determined by ordinary analysis,
without any attempt to indicate the arrangement of the particles; the
latter, on the other hand, representing not only the composition of the
compound, but also its molecular structure.  Thus, the composition
of acetic acidl, as determined by analysis, is C411-04; but when this acid
combines with a base it always parts with one equivalent of water (or its
elements), so that its salts, the acetates, have the general formula,
RO,C4H11303.  This would seem to indicate that the formula for the acid
should be written C4H303,110.  But certain considerations have led us to
the belief that in anlhydrous acetic acid, CaH303, 1 equivalent of the
oxygen is held in a different state from the rest, and therefore its formula
should be C41,302,0.  Adopting these views, then, while it is admitted
that the empirical formula, C4I1404, represents correctly the elements
of acetic acid, its rational formula Will be, C4H,3020 + HO.  In other
woirds, it is a compound having for its primary radical, acetyle, C413, and
for its secondary radical, C4T1302.-(Dr. Gibbs' Report, 2p. 43~)
540. In the following pages, a systematic nomenclature, according to
any particular theory, is not attempted; — the names of compounds
adopted are those in general use, with a few unimportant modifications.
QuESTIoNs. —Why is not the nomenclature of the compound radical
theory made use of in this work?  538. May most of the organic coampounds be arranged in series in a variety of ways?  Give the illustratiol
inl the text.  539. Has the real molecular structure of organic coulpounid4
been determiuned? What are e7nzpiricacl, and What rational forlnulle? G ive
the illustration by reference to acetic acid.  540. What is said of the
nome-nclatlure used in the remaining part of this work?




OF  ORGANIC  BODIES.                       399
In many cases, compounds are named from some one of the natural productions in which they are found, as malic acid from malum, an apple;
ciltric acid, from citron, a lemon; valerianic acid, found in the root of the
plant called valeriana offcinalis; cinchonia, obtained from the bark of the
cinlhonia condaminea, &c. The formulse, in general, are to be considered
only as empirical; frequently, two formulas are given for the same compound, with the sign - between them. In such cases, the first is always
the empirical formula, while the second indicates something further, as it
regards the supposed constitution of the compound, or the mode of its
reactions with other substances. The formula for cane sugar, for instance, is written C12H11Ol —Cl12H0O9    2-HO, by which it is indicated
that 2 equivalents of water (or the elements of water) sustain a relation
to the compound different from that of the other atoms of these elements.
Laczws of Combination and Transformation.
541, We have seen (536), that in organic compounds certain
g'roups of atoms, called compound radicals, frequently are found
to perform  the functions of simple substances.  Many of these
groups are already known, and many more will probably be hereafter discovered. If all the groups capable of acting in this manner, with their properties and relations, were known, it is very
probable that the transformations of organic bodies would not
differ essentially from those of inorganic matter, except as they
are affected by this circumstance.   In  other words, all cases
of chemical action would be reduced to instances of direct union,
or of single or double elective affinity.
When potassium is burned in oxygen gas, direct union takes place
between the two elements, and potassa (oxide of potassium) is formed —
K + O =KO. But when potassium is thrown into water, we have a case
of single elective affinity, as shown by the equation representing the
reaction;-thus, K + HO = KO ~- H. We may say in this case, either
that the oxygen is transferred from the hydrogen to the potassium, or
that the potassium  has replaced the hydrogen of the water.  When
solutions of nitrate of baryta and sulphate of soda are mixed together,
we have an instance of what is called double elective affinity; and by a
double transfer of elements we have formed the two new compounds, sulphate of baryta and nitrate of soda. Thus,
BaO,NO + NaO,S03=BaO, SO3 + NaO,N05.
QUESTIONS.-How are compounds often named?  Are the formulra
given to be considered as empirical or rational?  541. What is said
of the transformations of organic compounds as compared with those
of inorganic matter?  What illustrations are given fiom  inorganic
chemistry?




400               GENERAL PROPERTIES
542. So in organic chemistry, most if not all reactions will be similar
to one or another of the above cases. When olefiant gas, C4114 (308),
which is properly an organic product, and chlorine, C1, are brought
together, they combine to form an oil-like liquid, C41H4CI2.  But often
when two compounds have in this way combined, the new and more complex compound that is formed may, by a slight change of circumstances,
or even spontaneously, break up into compounds of less complex constitution. We have a case of this kind in sulpho-vinic acid, which is form-,I
by the union of alcohol, C4H602, with sulphuric acid. Thus,
C41602+ 2(SO3,1HO) =C4I6o02,2(S03HO) = C41150,HO, 2(So30OTI).
This last substance, called monohydrated sulpho-vinic acid, when
heated, breaks up, not into alcohol and monohydratecl sulphuric acid,
but into ether, C41150, and 2S03,33HO.
But most of the transformations in organic bodies may be considered
as instances of double decomposition, or double elective affinity.  The
action of chlorine upon acetic acid is properly of this kind, as is shown
by the following equation.  Thus,
C4H404 + 6C1= C4C111304 + 310C1.
Acetic Acid.   Chloracetic Acid.
It is, indeed, true that chlorine, one of the substances used, is not a compound, but we are to consider that the action is the same as if each of
the three atoms of hydrogen were successively replaced, giving for the
first step in the process the reaction, C4HO04 + 2C1   C4H3C104 + HC1.
One atom of the chlorine is transferred to the acetic acid, which at the
same time gives up 1 atom of its hydrogen to combine with the second
atom of chlorine, to form hydrochloric acid. This reaction three times
repeated results as given above, in the replacement of 3 atoms of hydrogen
by as many atoms of chlorine.
543. Substitution or Netalepsy.-We have seen above that
by the action of chlorine upon acetic acid, C4H404, the latter loses
3 atoms of hydrogen, and takes in their place 3 atoms of chlorine;
in other words, 3 atoms of chlorine are substituted in the acid for
an equal number of atoms of hydrogen. The new compound,
C4I1C1304, is called chloracetic acid, and in most of its properties
closely resembles acetic acid, from which it has been formed.
Transformations of this kind are of very frequent occurrence;
QUESTIONS.-542. What is the effect when olefiant gas and chlorine
are brought together?  When two substances combine so as to form
a more complex compound, will they sometimes break up in such a
manner as to form compounds different firom those which at first united?
Give the illustration by reference to alcohol and sulphuric acid. What
is said of acetic acid and chlorine in this connection? 543. What is the
change produced in acetic acid by the action of chlorine?




OF ORGANIC  BODIES.                         401
and the exchange or substitution may take place between atoms
or groups of atoms (compound radicals) which are similar to each
other in their chemical relations.
Hydrogen seems to be more frequently replaced than any other element;
and there may be substituted for it chlorine, iodine, bromine, or a metal,
or even a compound radical, as methyle, ethyle, &c. Instances of the
latter kind are seen in ethylamine, diethylamine, &c., in which one or
more atoms of hydrogen in ammonia are replaced by ethyle.  Thus,
ammonia   NHHHII, ethylamine = N11HC4H1i, diethylamine   NH(C4H5)
(C415) = NHII(C4H5)2, &c.
As hydrogen, chlorine, iodine, &c., form a natural family, one of which
may replace another in the compounds they form; so nitrogen, phosphorus, arsenic, antimony, and bismuth form another family, the indiviluals of which sustain a similar relation to each other.  Arsenide
of hydrogen, AsH3 (292), corresponds to ammonia in which the nitrogen
is replaced by arsenic; and the compound, Sb(C4H5)3, may be regarded
as ammonia in which the nitrogen is replaced by antimony, and the
hydrogen by ethyle.
Still another natural family is formed by oxygen, sulphur, selenium,
andl tellurium.  Alcohol, C4H160, by a substitution of sulphur for its
oxygen, forms mercaptan, or sulphur alcohol, C41H682.
544. Conjugated or Coupled Compounds.-lMany of the compounds produced by transformations in accordance with the above
principles, are frequently called conjugated or coupled compounds.
They may be radicals only, or acids, or bases.  As the name
implies, they are supposed to be formed by the union of other
compounds; and usually the characteristic properties of one or
the other of the coupling compounds will be more or less preserved in the new  or coupled compound.  Thus, ethylamine,
NItHCICJ1,, is a coupled or conjugated ammonia; —it is a substance formed on the type of ammonia, and possessing nearly the
same properties, ethyle, C04H5, being the couplet.  So the compoundsj (C4H1-5),Sb, C4H5,Zn, C2HBi, &c., are called conjugate
metals.
545. Homologous Bodies. — Homologous bodies are bodies
which may be arranged in series, all the members of which
are similar in their general properties and chemical relations,
QUESTIONS.-Betwedn what may substitutions take place? What other
elements or compound radicals may be substituted for hydrogen?  What
elements constitute a natural family with nitrogen, capable of replacing
enach other?  544. What are conjugated or coupled compounds?  What
examples are given?  545. What are homologous bodies?
34*




402                 GENERAL PROPERTIES
and are composed of the same elements, but differ from each
other in composition by the addition or subtraction of the elements, CH2, or some multiple of this expression.  Of this kind
are the alcohols, all of which, though they differ greatly in some
of their properties, still have many points of resemblance.  The
composition of all that are known will be seen by the following
table:
Names.                                 Formulae.
1. Methylic alcohol (wood spirit)......1............ CHO,
2. Common, or wine alcohol......................... C4H602.
3. Propylic alcohol.................................  C6H02.
4.  Butyric   "4...................................  C8H o1002
5. Amylic    4"  (fusel oil)........................ CIoH11202
6. Caprylic   "..................................; C GH1O2.
7. Ethal (ethalic alcohol).................. C32H-302
8. Cerotine (cerotic alcohol)................    C54JI602.
9. MBelissine (melissic alcohol)....................... C6016202.
Each of these compounds, denominated alcohols, it will be seen, cont:ains 2 atoms of oxygen;-the first, or methylic alcohol, contains C2H;
the second, C4H6 =   2H4 +-  C2H2,; the third, C6AH, and so on for the
others, by the addition in each case of C2H2, or some multiple of this
expression. In the cases requiring a multiple of C2H2, it would seem
that one or more intermediate compounds are wanting.  These may hereafter be supplied;-as, for instance, between amylic and caprylic alcohol
the compound, C14H1602, is not yet known, but when a compound having
this constitution shall be discovered, it is safe to predict that it will have
the general properties of this class of bodies.
We have, therefore, as a general expressive for the alcohols, the
formula, C2T-H2(F, n  1)02.
Besides the above series of alcohols, many other series are known,
among which are the following, taken from Gibbs' Report:
Hydrogens.     Acetenes.     Formic Acids.    Oleic Acids.
H             C2H112       C021204           C6H404
C21H3         C4H14         041404           C8H604
C415          C6H6          C611H604         CoH1804
61H17         C81H8         C81804           C 12H11004
or.. C..-2nI+ 1   C2nH2n        C2nH21104        C2,H2(n_-1)04
546. The compound, C212, which in all these series sustains so important a relation, has been called the homologizing body.  But it is
QuESTIONS.-In what do homologous bodies of the same series differ
from  each other in composition?  What series of substances of this
kind is mentioned?  What is said of the composition of the alcohols?
Give the general folrmula for the alcohols.  546. What is the compound,
C2112, here called?




OF  ORGANIC  BODIES.                            403
probable, that in other series other compounds, or perhaps a certain
number of atoms of an element, may serve as the homologizing body.
Thus, the ethyle and phenyle compounds differ from  each other by Cs,
which may be considered as the homologizing body connecting the cor
responding compounds of the two classes, so as to form two terms of a
homologous series.
547. Homologous bodies of the same series are in general similarly
affected by the action of a reagent; and the resulting compounds will
be homologous. This is implied in the definition of those bodies given
above.  The alcohols, C2,,H2(n1l)02, for instance, by the action of
oxydizing reagents yield corresponding homologous acids, C2,1H2;,04;and intermediate between the alcohol and acid, in several cases, another
compound is known, called an aldehyde (from alcohol dehydrogelatus),
and having the composition, C2~H2Z,,2.   Other compounds of this series,
we may confidently anticipate, will hereafter be discovered.
The following table contains the formula of the alcohols, their corresponding aldehydes (when known), and acids:
Alcohols.                Aldehydles.         Acids.
1. Methylic... C2H402.................. CH204.
2. Wine........ C41ET602......... C4H4021........ C411404.
3. Propylic  C611802.........  C6H602......... C611H604.
4. IButyric.....  CsH1002......... CSH802......... CH8804.
5. Amylic.....  C 1202......... C101oH110(2......... C0oH1004.
6. Caprylic... C,6,802................... C16111H604
7. Ethalic..... C2 0.........        02........ C32H3204.
8. Cerotic.....  C54H5602..................  C545404.
9. Melissic....  C6o6202....0.6.6......... C60H6004
IBesicles the acids in the above list, several others are lknown of the
same series, some of which will hereafter be mentioned; but the corresponding alcohols and aldehydes have not been discovered.
548. In every homologous series as yet known, containing oxygen, the
number of atoms of this element is constant; and the same appears to be
true of nitrogen, as will hereafter be shown.
In the alcohol series, C2nH2(nl~1)O2, it is evident the smallest value
we can give to n is 1, and the formula then becomes C2H401, which
represents methylic alcohol, but what the extreme upper limit may be
we are ignorant.  If in the general formula for the alcohols we make._ o, the formula becomes 1-1202 12HO, which represents 2 atoms
of water.  Water is therefore said to be the type of the series.  In like
QuEsTIo Ns.-AMay there be other homologizing bodies?  547. What is
sai;d of the effect of reagents upon homologous bodies of the same series?
Into what are the alcohols converted by oxydizing reagents?    hat interlmedliate product is obtained in some cases?  What are contained in the
talble in this paragraph?  548. What is said of the oxygen and nitrogen
in the homologous series now known?  Why is water said to be the type
Of thlc series of alcohols?




4Od       C~GENERAL PROPERTIES OF ORGANIC BODIES.
manner the general  formula for the oleic acids, C2,H2(.,1 —)O4, when
7 == 1, becomes C204 _ 2CO2; the type of the series is therefore carbonic acid, CO.
549. Although all the compounds of any homologous series are essentinlily similar in their leading properties, yet we may often observe a
gradual transition as we pass from  one to another of the same series.
The carbo-hydrogens (Hlydrogens and Acetenes, p. 402,) having the
smallest number of atoms are gaseous at ordinary temperatures, but
as we ascend in the series, that is, as the number of atoms in the compound is increased, they become less and less volatile, until the higher
miembers of the series, at the ordinary temperature, are liquid, or even
solid.  Methylic alcohol, the first in the alcohol series, boils at 1520, and
tihe others have each a higher boiling point in proportion as the number
of atoms is increased.  The last three are solid at ordinary temperatures.
In general, in any series, the boiling point becomes higher as the whole
numnber of atoms in the compound is greater.
550. Analysis of Organic Substances.-The analysis of a compound has
for its object to determine its composition; and in organic chemistry may
be either proximate or ultimate.  By the proximate analysis of a substance
we separate and determine its proximate principles, or, in other words,
the several organic compounds which may be contained in it, as sugar,
gum, albumen, &c.; but by its ultimate anallysis we determine its ultiTrrlte
elemlents, as carbon, hydrogen, nitrogen, &c.  The methods of separating
the proximate principles will be described as we progress, but for general
modes of analyses the intelligent student will colnsullt works tideating
specially of Analytical Chemistry.
551. Proximate principles are the proper organic compounds, which
canluot be separated into other kinds without evidently changing their
nature; they are usually characterized by one or more of the following
properties, viz.:
1. Capability of combining in definite proportions with other elementary
substances, ol well determined compounds.
2. Capability of crystalizing, when obtained il the solid state, or having
a definite melting point.
3. Having a definite boiling point, and being capable of distillation, or
sublimation, without decomposition, or a change of properties.
These compounds are seldom found uncombined in organized bodies,
and their separation, or the proximate analysis of the substances contaminig them, becomes an important object to the cheminist, and is often
attended with no little difficulty.
QIuESTIONS.-549. Do we observe a. gradual transition in the properties
of the members of a homologous series as we pass from one to another?
Give an instance to illustrate.  550. Define what is meant by the proximllato and what by the ultimate analyses of an organic comlpolmd.  What
is ta proximate principle? 551. What are the characteristics by onle or
mmore of which an organic compound will usually be distinguished?




STARCH.                          405
STARCH, SUGAR, GUM, LIGNINE.
552. These four organic bodies constitute a natural famnily,
possessing this remarkable peculiarity, that each member is
composed of twelve atoms of carbon, united with a certain number of atoms of water, or rather with the elements of water,
oxygen and hydrogen.  In general, they are nutritious subttances, and do not possess any very active chemical affinities.
STARCH, OR FECUL A, C121t00100
553. Sources.-Starch, or fecula, is obtained from  a variety
of' vegetable substances, as the different grains; and from many
roots, as the potato; and also sometimes from the stems of plants.
It is contained in the cavities of the vegetable tissues, in the form
of small, white grains, which always have a rounded outline, but
vary considerably in size and form, as obtained from different substances. Each grain is inclosed in a delicate envelope that is not
readily acted upon by cold water, but is
ruptured by the expansion of the inclosed
substance, when the water is heated nearly
to the boiling point.
To show the appearance of the starch        0
globules, in their cells in the vegetable        o
tissue, cut a very thin slice of a potato,
and examine it carefully by means of the       Section of Potato.
compound microscope; —their appearance will be much as represented in the above figure.
If the slice before examination is       C..... —
moistened with a very dilute alcoholic  A   C..
solution of iodine, the starch globules  B        iiit 
will be colored blue, while the other
parts remain uncolored.
The next figure shows the arrange- C
mlent of the starch globules in a grain  Starch Globules in a Grain of Rye.
QUESTIONS. -552. Of what are starch, sugar, gum, &c., composed?
31, Froml what is starch obtaineC   How is each grain inclosed?  I-low
lmay the grains of starch be showvn in the potato?




406                         ST ARCH.
of rye.  A, the outer seed-coat, which constitutes the bran after
grinding; B, the gluten (to be described hereafter); and C, the
grains of starch.
The grains of starch from different sources vary greatly in size,
and present different outlines.  Of the following figures, A represents starch grains of the potato, B those of wheat, and C( those
of peas.
A                        B                      C,Starch Gramls of the Potato.  Ditto of Wheat.         Ditto of Peas.
554. Preparation anc Properties.-Starch is easily obtained
from potatoes by mashing the tubers, and then inclosing the pulp
in a piece of cloth, and
cold water sat the sane
55 4~~jI~~~             time  pressing  the mass
between the ha tds.
From  wheat  or rye
flour it' is easily procured
by placing the flour upon
as a tenaciousa piece of muslin, and
working it with the hand
/~ lwhile a small stream  of
water is poured upon it.
-  _~ _ ~_~_      -  The  starch  is washed
through with the water,
Separating Starch from Wheat Flour.  while the gluten remains
as a tenacious mass upon the muslin. After a few hours the starch
will all subside.
QuSTIoNS..-What is said of the appearance of starch globules from
different sources?  554. HIow may st.ah be obtained from the potato?
How from- wheat or rye flour?




STARCH.                               407
Starch is an insipid white solid, quite insoluble in cold, but
slightly soluble in boiling water. In the latter case, the granules
are broken, and the broken envelopes floating in the solution give
it the consistence of a jelly.  In this state it is used for stiffening
linen.
Though quite insipid to the taste, it forms a large part of many
articles of food, as the different grains, rice, the potato, and other
esculent roots.  It also performs important functions in nearly
all vegetables during their growth.
The substances known as arrow-root, tapioca, and sago are
different varieties of starch.
Iodine forms with starch a beautiful blue compound, which is quite
insoluble in water; it therefore serves as an excellent test for it.
555. When starch is kept for some time at a temperature between 300~
and 400~, it undergoes a peculiar change, and becomes soluble in cold
water, and is called British gum, or leiocorne.
A substance very similar to the above, but called dextrine, is produced
by gently heating starch in water acidulated with sulphuric acid, or containing infusion of malt.  It has the same composition as starch, but is
very soluble in cold water, and is not colored by iodine.  If the mixture
is boiled for somne time, grape-sugar is formed, of which more will be said
hereafter.
Diastase is a substance produced in small quantity in the process of
malting grain, and is found in the potato soon after germination comnlences, in~ the parts near the young germs.  It is noted for its specific
action upon starch, converting it first into dextrine, in the same manner
as diluted sulphuric acid, and afterwards into grape-sugar.  Diastase
is known to contain nitrogen, but its composition, further than this,
has not been well determined.
556. The operation of malgting consists in exposing grain (usually barley) to the proper degree of heat and moisture, with the free accession
of atmos]iheric air, to produce incipient germination, and then suddenly
checking it by elevating the temperature.  This is done by. first soaking
the grain in water until it is fully swelled, and then placing it in heaps
upon a floor until it begins to germinate, when the furthler progress of the
vegetable process is arrested by quickly drying it at a moderately-elevated
temperature.  During the incipient germination, a portion of diastase is
produced, by which, in the subsequent processes to which the grain is
subjected, Lmuch of the starch of the grain is converted into dextrine andl
grape-sugar; and the grain (now called mialt) becomes fitted for the uso
to which it is applied.  It is chiefly used in the manufacture of beer.
QUESTIONS.-What is said of the properties of starch?  What varieties
of it are mentionedl?  555. What test of starch is mentionedl?  How is
starch affected by a heat of 300~ or 4000?  What is dexrbi(,z9?  WhatNl.
diaslase?  550. What is malt?  What use is made of malt?




408                        SUGARS.
SU G ARS.
557-. There are several varieties of sugar, but the most important
are cane and grape-sugar,-names suggested by the sources from
which they are respectively obtained. All the varieties of sugar
possess a sweet taste, are soluble in water, and are susceptible
of undergoing a peculiar change, called the vinous fermentation,
by which alcohol is produced.
558. Cane-Sugar, CI2H,,O,. —Most of the sugar of commerce
is obtained from  the sugar-cane (arundo sacchlarifrea), represented in the figure;-scale, one inch to
four feet.  But it is procured also in-this
country in large quantities from  the sap
of the sugar-maple (acer sacclarinuvm).
Many plants contain it in their juices, as
the common beet and other roots, and
the stalks of Indian corn.  Their juices,
after being expressed from the plant, are
evaporated until a dense syrup is obtained,
from which a large portion of the sugar
crystalizes on cooling; and the remaining
liquid portion is then drained off and
constitutes treacle, or molasses.
Pure sugar is a white, inodorous substance, of a very agreeable, sweet taste,
which it imparts to its solutions.   By
slow evaporation, in a very warm  room,
it is obtained in large rhomboidal crystals, which are sold as rock-candy.  It
is very soluble in water, but is dissolved
Sugar-cane.      only in small quantity in alcohol.  Its
density is 1'6.  It melts at about 356~, and on cooling forms a
transparent, vitreous mass, called barley -sugar, which, however,
QUIESTIONS.-557. How are the sugars characterized?  558. From what
is cane-sugar obtained?  Give some of the properties of sugar?  Whra
is barley-stlgar?.




SUaARS,                             409
after a time, becomes white and opaque, and is then found to be
a mass of small crystals.  Its composition remains without change.
FBy heating cane-sugar to 4200 or 425~, a change of composition is
effected; it then gives up 2 atoms of water, and a brown substance is
formed, called caranel, which has the composition, C2H9109.
559. Grape-Sugar —Glucose, C,2HOll4-,,   C,2T-,O, 20+ 21HO.This substance, which much resembles the preceding, has for its
composition, when crystalized, C12H14014; but by a boiling heat,
two equivalents of water are expelled.   It is more generally
diffused in nature than cane-sugar, being found in the grape and
most other sweet fruits.  It constitutes also the solid part of honey.
It may be obtained from grapes by expressing the juice, and neutralizing the free acid with chalk, and then clarifying and crystalizing in the same manner as with cane-sugar.
Grape-sugar is less soluble in water, and fbrms a less tenacious
syrup, and is less sweet than cane-sugar.  One ounce of water
will dissolve three ounces of cane-sugar, but only about two-thirds
of an ounce of grape-sugar; and it is estimated that one ounce
of the former has an equal sweetening capacity with two and a
half ounces of the latter.   Grape-sugar does not crystalize as
readily as cane-sugar, and is soluble in oil of vitriol, wlhile canesugar is blackened by it.
A dilute solution of sulphate of copper, containing a little potassa, or
tartrate of potassa, is at once rendered colorless by grape-sugar, at the
ordinary temperature, but this effect is produced by cane-sogar onlly by
boiling.  This serves as an unfailing test to distinguish the two varieties
of sugar.  The color of the copper solution is destroyed by the precipitation of suboxide of copper, Cun2(O.
560. Grape-sugar may be prepared from  several substances
which have a similar composition, as starch, gum, and woodyfibre or lignine, and is ocecasionally found in the animal system,
as in the disease called diabetes.  It then makes its appearance
in the urine.  It is sometimes called starch, s.garg diabeeic oSlonar,
and glucose.  The latter name is more properly applied to the
QuESTIONS.-Wlhat is caramel?  559. Describe grape-sugar. lWhat is
said of its solubility in water and its sweetness, as compared -with canesugar?    o-low may the two kinds be distinguished fiom each other?
560. Doscribe the mode of preparing grape-sugar, or glucose, from
starch.
35




410                           SU G AR S.
sugar preparea from starch, &e., but the identity of this substanes
with the sugar of grapes is generally admitted.
To prepare grape-sugar fr oml starch, 1 part of sulphuric acid is mixed
with 200 parts of water, and heat applied until the mixture begins to
boil; 50 parts of starch are then added, and the boiling continued until
the liquid becomes perfectly clear.  Powdered chalk is then introduced,
a little at a time, in order to neutralize the acid; and by a few hours
standing the sulphate of lime formed will be precipitated, leaving the
liquid clear, which is now solution of glucose. By evaporation of the
water it may be obtained in crystals.
Wood, the composition of which, as we shall hereafter see, is nearly
the same as that of starch, also yields grape-sugar, or glucose, by boiling
with sulphuric acid.  The process is essentially the same as the above,
except that a large proportional quantity of the acid is used.
In both of these processes the acid remains unchanged, but by its presence, in some unexplained mode, it occasions the starch and the cellulose
cf the wood to unite with an additional quantity of water-or the elements
of water-thus converting it into sugar.  Thus,
Starch (or cellulose), C1211i010o +- 410 = C121Hf4014.
From clean linen, or cotton rags, more than their own weight of sugar
may be formed.
Grape-sugar, prepared in this way, is used to adulterate cane-sugar,
and in the manufacture of beer and alcohol.
Sugar of sour fruits, as currants, cherries, plums, &c., possesses the
composition, C12I1H2012,  and readily ferments, producing alcohol, but is
uncrystalizable.
561. Milk Sugar, Lactine, C24II124024 = C24H19019 + 51HO.-This sweet
principle is obtained by evaporating the whey of milk, purifying with
animal charcoal, and crystalizing.  It is less soluble in water than either
of the other varieties of sugar, and less sweet to the taste.  Under certain circumstances, it is capable of undergoing the alcoholic fermentation,
like the other varieties of sugar; and in some countries, it is well known
that an intoxicating drink is made from  camels' milk.  But when in
solution it is allowed to stand in the open air, at ordinary temperatures,
lactic fermentation takes place, and lactic acid, C6-1606-  C6I-505,HO, is
formedl.  This chacnge takes place in the ordinary souring of milk.  By
the action of dilute acids at 212~, lactine is converted into grape-sugar.
502. ~ananite, C6T-7,6, though not analogous to sugar inl composition,
is simlar to it in some of its properties.  It is found in many plants,
but clliefly in a substance, called amanna, obtained from  certain species
of tie'ash.
QuESTIONS.-Describe the mode of preparing grape-sugar from wood.
Doe,: tie acid reimain unchangred in the operation?  What is said of the
suinar of sour fruits?  561. What is mill-sugar, or lactine?  May it
undergo tile alcoholic fermentation?  562. Describe mannite.




GUMS.-WV O O D ODY  FIB  E.                    411
G U MAI S   C2lzEIoO10.
563. Wce designate by the name of gaumn a variety of vegetable
substances, which are very soluble in water, but insoluble  in
alcohol, and uncrystalizable.  Their composition is the same as
that of starch, but they differ from  this substance in several
of their properties.
The gums generally  exude from  the bark  of trees, as the
cherry and peach trees, and are found on the outside in transparent masses, which are more or less globular in form.
A gum is a colorless, transparent, insipid, inodorous solid, and
when perfectly dry is very brittle, and has a vitreous fractureo
When put into water, it first softens and swells up considerably,
and then dissolves, forming a mucilage which is often used as a
substitute for paste, for which it answers well.  Its solubility is
increased both by acids and alkalies.  Gum, Arabic, gum  Sene-.,itl, and  umn  trayacantlh are the most common varieties of this
substance.
Solutions of gum Arabic, and probably also those of the other gumls,
yield sugar by boiling with sulphuric acid;-boiled with nitric acid,
naucic acid is formed.
564. Pectine is a substance closely resembling gum, which is found in
many fruits and in certain roots; it is the substance contained in curl
rants, cherries, apples, &c., which they yield on being b6lsled, and especially when boiled with sugar.  It is a kind of vegetable mucus, and
found in small quantity in many vegetables.  By the action of an alkali,
or almost any base, it is converted into an acid, calledpectic acid.
WOODY  FIBRE) LIGNIJNE   CELLULOSE.
565. Wood from  a growing tree is of a very complex composition.   By examination  with the  microscope, it is found  to
possess a highly organized structure (533), consisting of vascular
tissue, having its cells filled with a variety of substances, as
starch, solution of sugar and mineral salts, albuminous conmQUrESTIONs.-563. Describe the gums.  From what are thoy obtained?
What are some of the varieties of gum?  How are the gums affected by
sulphuric acid?  By nitric acid'?  564. Describe pectine. 565., What is
said of the comlpositionu of growing trees?




412                   tWOODY   I R  i   E
pounds, oils, and resins, depending upon the natural family and
species to which the tree belongs.
The first figure in the mlargin represents a transverse section of the stem
K 77,,,-    of a tree.  A is the outer bark, which
<~/ /~    X~ ~is usually rough, and has lost its vitality,
/ ((i~/)/"~ \7 -" )   and' serves only as a covering to the
parts within.  B  is the inner fibrous
\  bark, in which  the  sap-vessels  are
found, serving  the  purpose  of the
t feins of animals.  Inside of this is
the wood, consisting of the  part C,
which is usually whiter than the rest, and is therefore called the
culburtll'm, or scpq-woood; and the  zeart-wood, D, which is more
solid and durable than the sap-wood, and of a darker color.  Both
the alburnumn  and the heart-wood are composed of concentric
layers, an  addition  of a layer being
A  made to the alburnum  each year, immediately beneath the bark.  The next
[,,"Si?'"~','1       figure represents a transverse section,
_   ~14].' 1_..,  B  magnified, of a piece of pine, showing
the two kinds of wood-A, the alburnum; B, the heart-wood.  The inner
Section 0oriule.'rings of the alburnum  are gradually
converted  into firm  heart-wood, and seem  then  no longer to
partake of the vitality of the tree.  In'annual plants, the woody
part corresponds to the albu-num of trees.
566. Cellulose, C211TO,00-  The vascular tissue of which we have
spoken is composed chiefly of cellulose, the composition of which, it
will be observed, is the same as that of starch, though it differs essentially from this substance in some of its properties.
Cellulose constitutes the basis of wood, and is obtained by digesting
saw-dust, paper, or linen or cotton rags, successively in alcohol, ether,
diluted acid, diluted alkaline solutions, and water, so as to remove everythiing which is soluble in these menstrua.
I-t is found in very different states; as indigestible and hard, in wood,
aLid in the shells of nuts; as tender and easily digestible, in the esculent
QulSTIroN's.-Whatl is represented by the first figure on this page?
Wha1t by the second?  566. In +what is cellulose found?  What is said
of its composition? 




WOODY  FIBRE.                            413
roots, and in the pulp of fruits, as the apple, pear, &c.; as light and
porous, in the pith of the elder, and in cork; and as soft and flexible, in
the fibres of cotton, flax and hemp.
567. Lignine, Woody Fibre.-The vascular tissue of plants,
when first formed, is composed of nearly pure cellulose, but afterw:lrds the cells become lined with a hard incrusting substance,
which, in trees and shrubs, for years increases in thickness and
tolidity.  This is called lignine, or sometimes woody fibre, though
the latter term  is more properly applied to wood as found in the
tree, and composed of both cellulose and lignine.  Lignine is
fbund more abundant in the heart-wood than in the alburnum.
The composition of lignine is believed to be essentially the same as
that of cellulose, but it has not been fully determined.
We have seen above (560), that wood treated by sulphuric acid is converted into grape-sugar, but it is only the cellulose that is capable of this
change; lignine is not affected by sulphuric acid, or only charred.
The mutual relations of starch, sugar, and woody fibre, are singular
and important.  Their composition, we have seen, is nearly the samlle;
tandl they are convertible into each other by easy processes; indeed, we
are able to recognise this conversion as really taking place, in certain
cases, in the natural process of vegetation, as shown in the malting
of' grain.  The same change takes place in the ripening of many friuits,
as the apple and pear, which are acid until they approachl maturity, when
they become more or less sweet.  The sap of the maple and other trees
contain sugar, which subsequently becomes changed into woody fibre,
and thus contributes to the enlargement of the tree.
Cha/nfes produced v2jon gWoody Fibre by Acids.
568. Wood, plunged into strong sulphuric acid, especially if
a little warm, is instantly charred, as if held near a hot fire..
This is occasioned, it is believed, by the strong affinity of the
acid for water, the elements of which, oxygen and hydrogen, are
abstracted by it from the wood, leaving the black carbon.
If the sulphuric acid be diluted, or if added in small quantities,
so as entirely to avoid any rise of temperature, the effect is to form
sugar, as we have already seen.
QUESTIONS.-567. In what is lignine or woody fibre found?  What is
sidl  of the mutual relations of starch, sugar, and woody'fibre?  Are
they capable of conversion one into another?  568. What is the effect
ot strong sulphuric acid upon wood? What if the acid is diluted?
35 *




414 i                      V t ooD Y  F' 1   B E.
569. Gun  Cotton - Pyroxyline. —This  substance, which  is
inoted for its explosive property, is formed by the action of very
strong nitric acid, or better, by a mixture of the most concentrated  nitric  and sulphurie  acids, upon  cotton, flax, paper, or
fine saw-dnust.
To prepare it, mllake a mixture of equal parts (by volumle) of the
strolngest nitric and sulphuric acids, and then press into it a's much
cotton as can be moistened with it; and, after standing five or teu
mlinutes, press out as much of the acid as possible, and w-ash thoroughly
with a lar.lge supply of pure water, and dry carefully without artificial
heat.  It will be found that two ounces of each of the isxed acids will be
sufficient for 75 or 100 grains of cotton.
Whein thus prepared, the cotton appears much as before the process,
but has a bharsh feeling, and the fibres are less tenacious than in the
original cotton.  It also gains considerably in weight duling the process,
so that firom 100 grains of cotton as much as 175 grarins of gun-cotton
will often be obtained.  It takes fire very readily, often at a temperature
even below 2120, especially if the heat is suddenly applied; and burns
-with an imllensse volulle of flamne.  Placed on a plate of metal, and very
gradually leated, it may sometimes be completely decomposed, without
igniting, leaving behind a residue of carbon.  When properly prepared,
it explodes wiith great violence, and is entirely consumed.  Its power to
propel balls is much greater than that of the best gunpowder, which is still
fu-ther increased by soaking it in a solution of chlorate of potash before
drying.
The composition of pyroxyline is is uncertain; but it is known that,
by the action of the acids, oxygen and hydrogen (in the form of water)
are separated firoml the cotton, and, at the same time, nitric acid combines witlh it.  T'lie most probable opinion is that 2 equivalents of cellulose
combine with 5 equivalents of nitric acid, giving up at the time 3 ecquivalents of water.  Thus,
C24H20020 ~ 5N05  C241H17017,5No5 + 38HO.
Gun-cotton, though insoluble in water or alcohol, is usually found quite
soluble in sulphuric ether containing a little alcohol.  But this is not,
alwalys the case; and it is believed there are at least two different conlpounds formed ill the process, one of them being soluble in alcoholic ether,
and the other insoluble.  The insoluble variety appears also to explode
with more violence than the other.
The gelatinous ethereal solution of gun-cotton is used in surgery, as a
substitute for sticking-plaster, or court-plaster, under the nasmes of collodionz and liiutid cuticle.
Xyloidile is an explosive fompound similar to pyroxyline, produced by
the action of strong nitric acid upon starch.
QUsTJEsTON.-569. Describe the process of preparing gun-cotton.  Give
its plroperties.  What is the most probable opinion concerning the coinposition of pyroxyline, or gun-cotton?  In what is it soluble?  What is
xyloidine?




OODY  FIBRIE                             415
Changles of Woocly Fibre, by Air an(d Moisture.
570. When lignine is kept perfectly dry, or constantly immersed in water, it may be preserved for any length of time;
but exposed to air and moisture, it undergoes a slow decay, called
eremacatztsis (from  erena, slow, and kausis, combustion), by the
absorption of oxygen, and the evolution of water, or its elements,
and carbonic acid.
The chemical changes which in this case occur, are very nearly
the smame as in combustion, except that they take place more slowly.
In both cases, the constituents of the wood, with the addition of
oxygen from the air, are converted into carbonic acid and water;
in both cases, also, the hydrogen is oxydized more rapidly than
the carbon, as is shown by the black color during combustion,
naod the dark brown during the slow decay of vegetable matter.
The flame which appears during the combustion of wood and
other vegetable substances, is occasioned by the burning of the
gaseous hydro-carbons, evolved as the first effects of the application
of heat.
571. Humus, Geine.-Every fertile soil contains more or less oroanic
matter in a state of decay, to which its fertility is, in a great measure,
owing, and which has received various names, as hl7mes, geine, ulnine,
e//e/able nzould, uzic, geic, and silmic acids, &c. This decaying matter,
which we will call vegetable m70ould, is ever changing, as the carbon and
hydrogen are oxydizedcl and separated; and from this and the carbonic
acid, water, and ammonia, formed from them in the soil, the plants cerive
their chief nourishment, by means of their roots, which are extended in
every direction.
572. Peat.-Peat consists of partially decayed vegetable matter, which
is found in beds, in moist places, in every country, and is usually Jmixed
with more or less matter of mineral origin.  It is formed from vegetable
matter when slowly decaying under water, and of course free fiom the
influence of the oxygen of the air. Water is decomposed, yielding its
oxygen to one portion of carbon, to produce carbonic acid, while another
portion of carbon unites with the hydrogen, forming light carbur'etted
hydrogen (807), which often issues from the soil in large quantities, as
the flre-damp of coal mines; but most of the carbon remains behind as
peat. Recently formed peat is also usually found interlaced with the
QUESTIONS.-570. May wood be preserved if kept perfectly dry?
What. is the effect when exposed to air and moisture?  What is said
of the chemical changes which take place in eremacausis?  571. What
is contained in every fertile soil?  572. Describe the formation of peat.




116                     WVOODY  FIBRE.
fibtous roots of growing  plants, and retains, more or Less distinctly, the
forms of many of the plants of which it has been composed; but old peat
is more homogeneous, and may be cut into the form of bricks, like moist
cla y.  In many countries it is used extensively for fuel, hbeing first
thoroughly dried.
573. Coal.-A  sufficient description of the different kinds of mineral
coal has already (298) been given.  Immense deposits of this mineral
are found in many countries, which have no doubt been formed fromn
vegetable matter, at a comparatively early period in the world's history.
They are usually not very distant beneath the surftace; anld are contained between rocky strata of great extent.  Occasionally these strata
are covered with many feet of rock and earth -everything indicating
thlat vast changes have taken place in the earth's surface since their
formation.
T'lhat all the varieties of mineral coal have been produced from  the
nmatter of plants, which in former periods grew up and flourished precisely as plants now do, is universally believed by men of science.  The
evidence is found in the position of the coal, which always occurs in the
forml of beds interstratified above and below with solid rock formed at
the same tii e with itself;-.in the vegetfable impressions which aboundl
io the rocky strata of every coal formation; — and in the organized
structure often exhibited by the coal itself.
We may suppose that, by the decay of the vegetable mlatter, peat was
first produced, which wtas subsequently converted into proper coal, in a
mannler not fully understood.
Mines of coal are limited to the temperate zone, none of it being found
in very warm or very cold climates.
574. Petroleum.-PetroleLum, or rockc-oil, is an odoriferous, oily liquid,
which, in many countries, exudes from  the rocks and ground, being
formed, in all probability, from vegetable niatter at the same time with
peat and coal.  It is often found upon the surface of lakes and springs,
as at Seneca Lake in New York, where it is called Selzeca oil.  By distillation, petroleum  yields a yellowish liquid, lighter than water, called
naphltha, or oil of naphtha; which is probably a mixture of several compounds that have not yet been separated.  It is the liquid used to preserve the alkaline metals, A sphaltum, or mineral pitch, is a substance
closely allied to petroleum.  When cold it is solid, but becomes soft as it
is heated, and melts at about 2120.  Dissolved in oil of turpentine, it
forms a varnish which is used for certain purposes.
575. Distillation of Coal and Wood.-Illuminatiang Gas.-Coal and wood
are subjected to distillation by heating them to redness in large cast-iron
retorts, prepared for the purpose.  Usually the retorts are kept at a red
heat, and are capable of being opened at one end, so that the charge
omay be changed when necessary.
QuEsTIONS.-What use is made of peat?  573.  -Iow have the deposits
of mineral coal been formed?  What evidence of this is there?  574. Describe petroleum.  How is naphtha obtained from it?  What is asphaltum,
or mineral pitch?  575. How are coal and wood distilled?.




WooDY FIBRE.                               417
Coal subjected to this process gives off large quantities of gaseous carburetted hydrogens (309), with carbonic acid and sulphuretted hydrogen,
atnd a resinous substance not unlike tar, called coal-tar.
This last substance is a mixture of several compounds, as naphthalene,
phenol, salts of ammonia, &c.
A gas, not unlike that prepared by the distillation of coal, is often
found to issue, ready formed, from  the earth, and may be collected and
used like that formed by art.  The village of Fredonia, in the State of
New York, is lighted by natural gas, in this way; and in some salt-works
in-Virginia, it is said, no other fuel is used for boiling the brine.
576. Wood by distillation yields illuminating gas with water, acetic acid,
creosote, pyroxylic spirit (nmethylic alcohol), tar, &c.  The acetic acid, as
filrst obtained, is mixed with creosote and other substances, and is called
pyroliygneous acid.
Creosote, C2l16C),0, which passes over, with other products, in the distillation of wood, is a colorless, transparent liquid, of an oily consistence,
a-d1 retains its fluidity at -17~.  It has a specific gravity of 1 04; boils
It 3970, and is a non-conductor of electricity.  It has a burningr taste,,niid its odor is like that of wood-smoke, or rather of smoked meat.  It is
l'ghllly antiseptic to meat: the antiseptic virtue of tar, smoke, and crude
pyroligneous acid, seems owing to the presence of creosote.  Its name
(L:rom 0krceas, flesh, and sozein, to save) was suggested by this property.
Creosote requires about 80 parts of water for solution, but is soluble in
everly proportion in alcohol and ether.  It has neither an acid nor alkalinle reaction with test-paper, but combines both with acids and alkalies.
It is used both internally and externally in medical practice.
Naphthaline, C2oH, is a solid substance, obtained by distillation from
coal —tar.  It is a white, crystaline solid, which melts at 175~, and boils
at about 422~.  It has a specific gravity of 1'05, and is insoluble in
water, but dissolves in alcohol and ether.
By the action of chlorine and bromine, and also by the action of acids,
as the sulphuric and nitric, upon this substance, various interesting compounds are formed.
Paraffine is sometimes found in petroleum, but is generally procured
by the distillation of wood-tar.  It is a white, waxlike solid, of specific
gravity 0'87, which melts at about 1100.  It may be distilled without,lrteration.  It received its name (parunm  affinis) from  the circumstance
thlLat it manifests little affinity for other substances.
Etlpione, C6H6, is a fragrant, colorless liquid, obtained by the distillltion of wood.  Its specific gravity is 0'655, and its boiling point
iabout 340~.
Phenol is obtained from  coal-tar by distillation.  Its composition is
CqH602, in which, as well as in many of its chemical relations, it reQUESTIONS.-What are formed when coal is distilled?  576. What compounds are mentioned as being obtained by the distillation of wood?
Describe creosote.  What is the derivation of the name, creosote?  Describe naphthaline.  Paraffine.  Eupione.  What is said of phenol?




18                    V WINE  ALCOHOL.
etiibloes the alcohols (547), and has therefore been called phenylic'1lcohol
By the action of reagents, many compounds are formed from it, analogous to those obtained from the alcohols.
ALCOHOLS AND SUBSTANCES DERIVED FROM TIHEM.
577. The name alcohol has long been applied to a well known
liquid, obtained by fermentation and distillation from solution
of sugar, and starch, or substances containing one or the other
of these compounds.  But in the progress of the science, several
other compounds, analogous to common alcohol, both in composition and properties, have been discovered, to which the name
is also given.   The general formula, C2,,H(f,,+)02 (545), may
rtepresent their composition.
The three most important of the alcohols are, common, or wine alcohol,
methylic alcohol, and amylic alcohol, which, with their derivatives, will be
here described; the others will be attended to in their proper places.
WINE ALCOHOL  C4H11602.
578. Common, or wine alcohol, is always produced by the fermentation of sugar or starch, or compounds containing one or the
other of these substances.
579. Fermentation.-By the fermentation of a substance, we
mean a change or modification which takes place in its constitution under the influence of another substance, called a ferment,
which acts simply by its presence.
Several different fermentations have received separate names,
as the vinous or alcoholic fermentation, by which alcohol is produced from  starch or sugar; the viscous fermentation, by which
sugar is converted into a viscous, or mucilaginous substance; the
acetic fermentation, by which diluted alcohol and other substances
are changed to acetic acid, &c.
The most important ferment used for inducing the vinous fermentation
is yeast, or leaven; but blood, albumen, caseine, and the juices of many
QUEsSTmoNS.-577. Give the general formula for the alcohols. Name the
three most important alcohols. 578. Ilow is common, or wine alcohol,
always produced?  579. What is meant by fermentation?  What diftforent fermentations are mentioned? What ferment is generally used to
produce the vinous fermentation?




WINE ALCOEHOL.                              419
fruits, as zurrants, apples, grapes, &c., are capable, after being exposed
for a time to the air, of producing the same effect.
Yeast is a substance which collects as a froth upon the surface of beer,
and other liquids, in the process of fermentation.  It always contains at
portion of nitrogen, which seems essential to it, but the mode of its
action has not been determined.
Active yeast is believed by many to
contain a kind of microscopic vegetable, a )<
which is developed spontaneously in the
organs of plants, and in many nitrogenized
substances when left to putrefy.  It can
be observed only by use of the microscope.  Ci(Q       X.- i.
See figure in the margin....
To induce the vinous fermentation, a:, -
quantity of sugar is dissolved, or an equal
quantity of starch diffused, in 4 or 6 times
its weight of water, a small quantity of            YeastPlant.
yeast stirred in, and the mixture placed in a situation where it may
retain a uniform temperature of 700 to 85~. After a time the solution
will be found in brisk effervescence, occasioned by the escape
of gaseous matter, which may
easily be collected over mercury (see figure), and on examinatiou  proves to be pure
calrbonic acid. When the action
has ceased the liquid again becoimes clear, and is found to
contain, not sugar, but alcohol,
which may be separated by distillation, and by other nmodes.            Alcoholic Fermentation.
In this way it is found that alcohol and carbonic acid alone are produced by the vinous fermentation, in the proportion of 2 equivalents
of the former to 4 equivalents of the latter.  It would not seem difficult,
therefore, to understand the nature of the change that takes place when
fruit-sugar (560) is used, for this sugar contains precisely the elements
of these compounds in this proportion. Thus,
C2H,120,,2 = 2(C4HI02) + 4C02.
But when  starcn, C ltoIlo0, cane-sugar, C2H111011, or grape-sugar,
C12H14O014, is fermented, the case is a little different, and the first effect
of the ferment is to convert them into fruit-sugar, by an obvious change.
580. Preparation and Properties. —Alcohol obtained by dis.
tillation always contains a portion of water, even  after sevcr:l
QuusirroNs.-What is yeast?  What is represented by the figure?
What are the products of the vinousfermentation?  How many equiv:alents of alcohol and carbonic acid are produced from an atom of fruitsunga?  580. May pure alcohol be obtained by distillation?




420                    WINE  A L o OOL.
successive  distillations.   When  most highly  rectified  in  this
mode, it contains about 90 per cent. of pure alcohol, the rest
being water.  The alcohol, or spirits of wine, of commerce is
seldom as pure as this.  To obtain absolute alcohol, or alcohol in
a state of purity, common alcohol is carefully distilled, by the
heat -of a water-bath, from pearlash or chloride of calcium, previously dried and mixed with it. The water combines with the
salt and remain.s behind, while the pure alcohol distils over.
Alcohol sufficiently pure for almost any purht )         pose, may be obtained, without distillation, by
means of well-dried pearlash.  For this purpose,
take common alcohol, or even proof-spirit, *or
~I, % l           \\\ whiskey, and pour into it half its weight or more
of pearlash, which has previously been thoroughly
dried by heat.  The whole is then to be shaken
together a few minutes, and allowed to stand
several hours; there will then appear in the
vessel two liquids entirely separate, one abovo
the other, as shown in the figure.  The upper
portion is to be carefully drawn off and subjected
to a second operation of the same kind, by means
of a fresh portion of dried pearlash; and this
Solution of Pearlash in   operation is to be continued as long as the introP'roof Spirit.   duction of the pearlash produces any effect.
Pearlash is soluble in water, but quite insoluble in alcohol; when,
therefore, a portion of it, perfectly dry, is introduced into alcohol containing water, the latter dissolves it, and the dense solution settles to the
bottom, while the alcohol remains above. After several repeated operations, all the water, or nearly all, is thus separated.
581. Pure alcohol is a colorless liquid, of a pungent taste and
odor; and at 60~ has a density of 0'795.  It boils at 1720; and
its vapor is highly inflammable, and burns with a pale yellowish
flame, without smoke.  It has never been frozen by any cold yet
produced; but at a temperature of  -146~, becomes thick and
tenacious, like melted wax. It is a powerful solvent for many
substances totally insoluble in water, especially many of the
resins.  Hydrate of potassa (and also of the other alkalies) dissolves readily in alcohol, forming a solution often used in the
laboratory.
When potassium  (or sodium) is immersed in absolute alcohol,
QUrsrTTON.-I-ow may pure or absolute alcohol be procured?  Describe tl-ohe mode by the use of pearlash.  581. Describe the properties
of alcoho'.




WINE  ALCOHOL.                          421
hydrogen is given off, and a crystaline compound formed having
the same composition as alcohol, except that 1 atom of hydrogen
is replaced by I atom of potassium. Thus.
C4H602 + K =  04H5KO2.
By contact with water, this compound is converted into alcohol
and hydrate of potassa.
Vapor of alcohol has a density, as determined by experiment, of 1.613 
but, as calculated from the densities of its constituents, it is 1'596'
Thus,
4 vols. carbon vapor weigh (.836 X 4) 3.344
12  "  hydrogen       "   (.069 X12)'828
2  "  oxygen         "  (1-106 X 2) 2'212
4 vols. alcohol vapor weigh         6'384
One vol. alcohol vapor therefore weighs 1-596.
Alcohol exists in every kind of spirituous liquors, and may be separated
from them by distillation.  The different kinds of brandy, ruzn, gin, and
whiskey, usually contain from 45 to 55 per cent. of pure alcohol; the
stronger wines from 18 to 25 per cent.; and the weaker, not more than
12 or 15 per cent. In cider, ale, and porter, the quantity varies from
4 to 10 per cent.
Alcohol is extensively used in the arts and
in medicine, chiefly in consequence of its
powerful solvent qualities. Taken internally,
it operates, as is well known, as a powerful
stimulant; and various alarming diseases,
often terminating in extreme moral degradation and death, attend its habitual use.
Used in lamps instead of oil, great heat is
produced, and the combustion is unattended
with smoke, for which reason it is much employed in the laboratory. A cover, a, fitting
accurately upon b, prevents evaporation when
not in use.                                      Spirit-lamp.
582. Bread-making.-The ordinary mode of raising bread by means
of yeast, also furnishes an instance of the vinous fermentation.  The
yeast contained in the flour-paste, or doiugh, causes the fermentation to
commence, as already explained, and both alcohol and carbonic acid are
formed in the dough; and the latter being retained in the tenacious mass
causes it to swell up, or rise. This effect is further increased by the
expansion of the gas by the heat in the process of baking, giving the
QUESTIONs.-What is the effect when potassium is immersed in alcohol?  In what is alcohol always contained?  582. What is said of breadmaking?
36




422                   WINE  ALCOHOL.
bread its light, porous character.  The small quantity of alcohol formed
is dissipated by the heat of the oven.
Bread is also raised, as is well known, by the use of bicarbonate of soda,
or potash, and an acid, as the hydrochloric or tartaric acid, or the acid
tartrate of potash (cream of tartar).  The rising is in this case produced
by carbonic acid liberated in the dough from the alkaline carbonate; and
the same light, spongy character given to the bread.
Products of the Oxydation of Wine Alcohol.
583, Aldehyde, C4,H,0. -  Aldehyde (from  alcotol deliydrogenatus), as will be seen by an inspection of its formula, is
dehydrogenated alcohol, -alcohol from  which  two  atoms of
hydrogen have been separated.  The separation of the hydrogen
is effected by distilling alcohol with highly oxydized substances,
which readily give up a portion of their oxygen to form water
with the eliminated hydrogen.
The best method for preparing it, is to mix in a retort equal
parts of powdered bichromate of potash and strong alcohol, and
then add, in successive portions, 1i  parts of sulphuric acid.
Energetic action commences at once, much carbonic acid is given
off, and aldehyde, mixed with a small quantity of acetic acid and
other substances, distils over into the receiver, which is kept
surrounded with ice.  To the liquid thus obtained, some ether is
added, and it is then saturated with ammonia, which forms with
aldehyde a crystaline compound, cadeleyde ammonia, NH3,,04H402.
This solid, distilled at a gentle heat with dilute sulphuric acid,
and then re-distilled from chloride of calcium, previously fused,
affords the pure aldehyde.
Aldehyde is a colorless liquid, of a peculiar suffocating odor;
at 600 its density is 0'790, and it boils at the low temperature
of 700 or 71~.  It is soluble in water, alcohol and ether; and
burns with a pale flame.  It dissolves sulphur, phosphorus, and
iodine; and is especially remarkable for its affinity for oxygen,
in consequence of which it is capable of reducing many of the
metallic salts,  Its action: upon nitrate of silver is remarkable.
If a solution of this saltisp:S'oured into a clean glass vessel, with
QUESTIONS. -What occasions the r'isig which gives to bread its spongy
characlter?  583. What is aldehyde?  Describe the mode of preparing
it.  What are some of its properties?




WINE ALCOIHOL.                            423
al little ammonia, the addition of some water, mixed with aldehyde, causes an immediate precipitation of the silver upon the
surface of the glass, which retains its perfect metallic lustre, like
the coating of a looking-glass.
Aldehyde is instantly decomposed by contact with an alkali; and if
kept only a short time, it changes spontaneously into one or two other
compounds isomeric with itself, depending upon the temperature;-these
are, elaldehyde and metaldehlyde, the former of which is liquid and the
latter solid. By combining with oxygen, aldehyde forms aldekiydic or
c1celools acid, C4H403.
584?; Acetic Acid, (4H404  -C4H30,,HO. —Acetic acid is well
known as the acid contained in vinegar (from  the French vin,
wine, and aigre, sour), which is, in fact, a very dilute acetic acid,
containing also much saccharine and mucilaginous matter.  Acetic
acid is one of the most important of the organic acids, and is
found, in combination with bases, in many plants.
This acid is formed artificially by a variety of processes, but
the usual method of preparing it is to subject liquids containing
alcohol, as the weaker wines, cider, &c., to the action of some
ferment, while exposed  to the atmosphere.   The process has
sornetimes been called the acetic fermentation; and the chemical
changes which take place in it consist in the separation from the
alcohol of 2 atoms of hydrogen by the oxygen of the air, forming
aldehyde and water, and the subsequent absorption of 2 additional
atoms of oxygen by the aldehyde.  Thus,
4114H602 + 20 = C41I402 + 210, and
C4H402 + 20 = C4H404.
The access of atmospheric air is absolutely essential to the formation of vinegar by the ordinary
process, as is well known; and its production is
much facilitated by a method invented in Germany.
A cask, as shown in the figure, is filled with wood
shavings, and closed at top by a pan, b, the bottom
of which is perforated with many small holes,
through which small threads are passed to conduct
the liquid downward.  The shavings, being first
well soaked in vinegar, are placed lightly in the
cask; and below them are several small holes, cc,
about half an inch in diameter, to admit the free    Prep. of Vinegar.
QurislloNs.-Can aldehyde be kept without change?  584. What is
vinegar? Hlow is it formed artificially?  Describe the German process.




'42-4                  W I N E W  AL CO  O  L.
accession of air.  If now proof-spirit, diluted with four times its weight
of water, and having mixed with it a very little honey or yeast, is poured
into the pan above, it gradually trickles clown upon the shavings, where,
a large surface being exposed to the atmosphere, rapid absorption of
oxygen takes place, the temperature is raised, and acetic acid is formed.
As the liquid passes down, it is collected in the vessel a; and when
passed through three or four times, which requires but about 36 hours,
it is converted into vinegar.
Acetic acid cannot be separated from water by mere distillation; but
the pure acid is obtained by distilling some acetate, as acetate of soda
or lime, &c., with a proper quantity of sulphuric acid, and collecting the
product in a cold receiver.
Wood-vinegar, or pyroligneous acid, is obtained by distilling wood in
close vessels.  It is a very impure acetic acid, having a disagreeable,
smoky odor, and containing empyreumatic oils, and other substances
dclerived from the wood. It is much used in calico-printing; andc often
the cloths, not having been properly cleansed, possess its disgusting
odor.
585. Pure acetic acid, at 63~, is a colorless liquid, of a pungent,
refreshing odor, and excessively sour to the taste.  Applied to
the skin for a time, it produces blisters.  It boils at 2480; and
cooled below 630, it may be obtained in crystals.  At 63~, the
density of the liquid is 1'06.  It mixes readily with water, ether,
or alcohol.
586. Acetal, C      I,,40,. —This compound is a clear, colorless
liquid, which boils at about 1670, and has
a density of 0'844.  It is formed by the
slow  action  of moistcned  platinum   blackl
i 11        upon  a mixture of vapor of alcohol and;ffilJI       Xoxygen, in a large bell-glass.   The  bell.
iif Ilglass is to be open  at top, and elevated
Ij Slll  a little from  the bottom  of the basin in
I| l i1which it is placed, as represented  in the
tfigure, so as to allow a gradual circulation
t t   lg   ^   of the air through it.  A  watch-glass, A,
is placed in the centre of the basin, containing a little platinum   black; and  a small
Prep. of Acetal.  funnel, with a long neck, B, contains strong
alcohol, which drops very slowly into the watch-glass.  By the
QUSTrIONS. What is pyroligneous acid?  585. Describe the properties
of ptre acetic acid.  586. How is acetal formed?




WINE ALCOHOL.                           425
catalytic action of the platinum, the alcohol is decomposed, and
acetal, aldehyde, and acetic acid, are formed, and, condensing
together upon the sides of the bell-glass, are collected in the
basin.   This liquid is now  to be neutralized with powdered
chalk, and carefully distilled from chloride of calcium.
Salts of Acetic Acid, and Other Allied Conmpounds.
587. Acetic acid combines with most bases, forming salts
called acetates.  In  combination, its composition  is C,4H,03;
from  which it appears that in the process of combining, one
atom of water-or the elements of water-is given up.  Or, we
may consider (with sonme chemists) the metal of the base as
simply replacing 1 equivalent of the hydrogen of the acid (353).
Thus, when acetic acid combines with soda, the acetate of soda
formed has for its composition, NaO, C4H303; and we may indicate the supposed relationship of the sodium as replacing 1 equivalent of the hydrogen, of the acid by writing its formula thus,
C4F1T,(Na)04.
Acetic acid is monobasic; that is, the salts it forms contain a single
equivalent of the acid with one equivalent of base. These salts are also
said to be monobasic (170, 349).
We shall describe only a few of the more important acetates.
588. Acetate of Lead, PbO,C4dH30, + 3HO. -This is the
suziar of lead of commerce.  It is formed by dissolving oxide
of lead (litharge) in acetic acid.  It is very soluble in pure water,
and has a sweet, astringent taste.  Taken internally, it is poisonous; but is used in various preparations in medicine. The
31H0 is water of crystalization.
If we consider the metal as replacing an equivalent of the
hydrogen of the acid, its formula may be written, (J4I,(Pb)O,.
Besides the above neutral acetate of lead, there are several other
acetates of the same base, which are formed by the combination of this
comrpouncd with additional equivalents of oxide of lead, as 2PbO,3CH,03,,
and 3PbO, C4Hs03. The latter of these, sometimes called tribasic acetate
of lead, is used in medicine, and in the proximate analysis of organic
QESTIONS. -587. What are the salts of acetic acid called?  What is
sadicl of acetic acid as it combines with bases? Is this acid monobasic?
Wh at is meant by this?  588. Describe acetate of lead. What is it
called in commerce?
32*




4'26                  WINE  ALCOHOL.
compounds. It is formed by digesting 7 parts of lithargc /z i  parts
of the neutral acetate in 30 parts of water, and evaporating the K.Alution
until crystals are formed on cooling. The solution is called in pharmacy
Gooulard's extract of lead.
589. Acetate of Copper, CuO,C4H,03. —Acetate of copper is
obtained by dissolving verdigris in hot acetic acid.  On cooling,
it is obtained in fine green crystals, w'hich contain one atom of
water, and is sometimes called dist'ied verdigris.  This salt i
capable of uniting with additional equivalents of oxide of copper,
forming sub-acetates; and the:.erdigris of commerce, used as a
paint, appears to be a mixtvz- of these.  It is prepared in large
quantities, in the south of France, by covering copper with the
refuse of grapes, after tl.e juice has been extracted for making
wine; the saccharine matter contained in the husks furnishes
acetic acid by fermn-atation, and in four or six weeks the plates
acquire a coating of the acetate.  A purer and better article is
prepared by covering copper plates with cloths soaked in pyroligneous acid
590. Acet,t, of Airmnlna, Ab203,3(C,H30,).-This salt is prepared by
decomposing solution of sugar of lead by alum.  It is used in dyeing,
and calico -printing.
591. Acetate of Iron.-By treating iron-filings with dilute acetic acid,
a mixture of the acetates of the proto and sesquioxides of iron is obtained,
which is considerably used in the arts.
592. Acetate of Ammonia, NIH,,C4HO303,HO =C4H3(NH4)04, is readily
forimed by neutralizing acetic acid with ammonia, or its carbonate. It
has been used in medicine under the name of spirit of iiniidererus.
593. Chloracetic Acid, C114H04C1],-C4Cl,O,,HO, or C4J1(C13)04.
-This acid is formed from acetic acid, by the abstraction of 3 atoms
of its hydrogen, and the substitution of 3 atoms of chlorine.  It is
prepared by placing some crystals of acetic acid under a large bellglass filled with chlorine, and exposing it to the direct rays 6f the
sun.  Other compounds are formed at the same time, which are to
be separated from it, and then it is obtained in colorless rhomboidal
crystals.
QUESTIONS.-589. How is acetate of copper formed?  What is the
verdigris of commerce?;How is verdigris prepared?  590. What otler
acetates are mentioned?  593. How is chloracetic acid formed?




WlNE  ALCOHOL.                           427
Neglecting the secondary compounds formed, the reactions will
be represented as follows, viz.:
CJ4H30,HO + 6C1-  CCl303,,IO + 31HC1.
The crystals, when heated, melt at 1130, and the liquid boils at
about 392~.  It closely resembles acetic acid in its properties,
neutralizes the same quantity of bases, and forms salts similar to
the acetates.
594. Acetone, C61-,02.- Acetone, or Tpyroacetic spirit, is a
limpid liquid, obtained-by passing vapor of acetic acid through a
red-hot tube, or by distilling a mixture of dry sugar of lead and
powdered quicklime, and condensing the product in a cool receiver.
TMuch uncondensable, gaseous matter passes over at the same time,
which is allowed to escape.  It has a density of 0'792, and boils
at 132~.  In some of its properties, acetone appears to be closely
allied to the alcohols, but in its composition it is isomeric with
the aldehyde of propylic alcohol (547).
In the preparation of acetone, another allied compound often makes
its appearance, called vmetacetone, orp'op'ioze, C6T-50.  (We should prefer
to call it proplyloe.) A corresponding acid is known, called the mnetacetonic, propioelzc, or propylic acid, C61-1604.
Action of Chlorine upon Alcozol.
595, When a current of dry chlorine is passed through anhydrous
alcohol, the first effect is to produce aldehyde and hydrochloric acid.
Thus,
C4H6002 + 2C1 = C4H402 + 2- IC1.
Two equivalents of chlorine, therefore, have separated 2 eq. of the
hydrogen of the alcohol, forming 2 eq. of hydrochloric acid, the residue
of the alcohol constituting aldehyde.
But if the action of the chlorine is continued, a new compound is
formed, called chloral, C4f3C1302. It may be regarded as aldehyde in
which 3 eq. of hydrogen have been replaced by 3 eq of chlorine.  The
reactions are as follows:
C4H402 + 6C+ Cl C4HC'1302 + 3HC1.
Or, regarding it from the beginning of the process,
C4TT602 + 8C1 — C4tIC1302 + 5-IC1.
QUESTIONS.-594. Describe the mode of preparing acetone. 595. What
is the first effect when dry chlorine is passed through pure alcohol?  What
is formed when the process is continued?  How may chloral be regarded?




428               MIEETIHYLIC ALCOHIOL.
Chloratl is an oily liquid, of specific gravity 1'5, which boils at 201~,
and has a strong affinity for water, being soluble in water, alcohol, or
ether.
TMETHYLIC  ALCOHI-IOL   OR  WOOD-SPIRIT CI,2-402.
596. Preparation and Properties.a-When wood is subjected
to distillation in a close vessel, besides the uncondensable gases
which pass over, there is obtained an aqueous liquid, composed
of pyroligneous acid (584), and other compounds; among which,
is a volatile, inflammable liquid, long known as wood-spirit, or
p7yroxylic spirit (fiom pur, fire, and xulon, wood).  But from its
resemblance to alcohol, in composition (547) and many of its
properties, it is more properly designated as rnethylic alcohol,
(from rnethu, wine, and xulon, wood).
To separate it from the other compounds, the crude liquid is
first neutralized with lime, and carefully distilled, only the part
that passes over first being preserved, as this will contain nearly
the whole of the wood-spirit.  To obtain it pure, it must be several
times re-distilled from chloride of calcium and lime.
IMethylic alcohol is a colorless liquid, with an odor and taste
so~mewhat resembling those of common alcohol.  It has a density
of 0'798, and boils at 1520, and burns fireely in a lamp.
It mixes readily with water, alcohol, and ether, and, like common alcohol, dissolves freely most resinous substances.  Some use
has been made of it in the treatment of diseases, under the name
of?wood najphtha.
The formula of this compound, C2H402, represents 4 vols. of its vapor,
the density of which, by calculation, is 1'109, as follows:
2 vols. carbon vapor weigh    ('836 X 2)    1-672
8 vols. hydrogen,           (-069 X 8)'552
2 vols. oxygen,            (1-106 X 2)   2'212
Giving for 4 vols. vapor of methylic alcohol, 4.486
The weight of 1 vol., or density, therefore, is 1.109
Products of the Oxrydation of Methylic Alcohol.
597. Formic Acid, C211204 =  C21H O,,10.-This acid was first
obtained, by distillation, from  the bodies of red ants (formica(
QUSTIONMs.-596. From what is methylic alcohol, or wood-spirit, ob.
tained? Describe mlethylic alcohol.  597. From what was forlmic acid
first )btained?




MI ETRYLIC ALCOHOL.                       429
r7'1tJ);. and hence its name. Its relation to methylic alcohol is
the same as that of acetic acid to common alcohol.  It may be
obtained by exposing the vapor of wood-spirit, mixed with air, to
the action of platinum black, under a receiver, water and formic
acid being produced at the same timec.  It appears that two atoms
of oxygen combine with 2 atoms of the hydrogen of the spirit,
forming 2 atoms of water; and then 2 atoms more of oxygen
unite with the residue to form the acid.  Thus,
C2140,  + 20 =  C21-1202 + 2HO0, and
C21202 +- 20 = C2H204.
Formic acid may also be produced by distilling a mixture of
sugar, bichromate of potash, and oil of vitriol, and by other
mlleans.
Formic acid is a clear liquid, of specific gravity 1'24, has a
stlrong acid taste and pungent odor, and quickly blisters the skin.
It boils at 212~, producing an inflammable vapor, and solidifies at about
332~.  It is contained in small quantities in many plants, as the nettle,
and produces the pain occasioned by
handling them.   The figure represents the " sting" of the nettle, greatly
magnified, with the sacks at the base
containing the acid.
When  this acid  combines with
bases, like acetic acid, it gives up
the elements of an atom  of water;
and is therefore by many considered                           =
as a hydrate, and its formula written
Sting of Nettle.
C,2H0, + HO.  Or, as in the case of
acetic acid (587), we may consider the metal of the base as
replacing 1 equivalent of the hydrogen of the acid.  Thus, the
formiate of lead, PbO,C,2HO,, on this supposition, will have for
its formula, C2H(Pb)O4.  It is monobasic, like acetic acid.
Q.uEsTINsTO.-What is said of the relation of formic acid to methylic
alcohol?  lay it be procured from sugar?  Describe the process. Describe its properties. Is it found in plants? What is said of the nettle?




430                  AMYLIC ALCOHOL.
598.  The form7ziales, in their general properties, resemble the cor.
responding acetates.  The alkaline formiates are used in the analyses
of some minerals.
599. ~Methylal, C6TTs04.-This substance is procured by distilling a
mixture, in proper proportion, of methylic alcohol, dilute oil of vitriol,
and peroxide of manganese, and purifying the product.  It is a colorless
liquid, of an agreeable aromatic odor, and burns with a yellow flame. It
has a density of 0'85, and boils at 108~.
AMYLIC  ALCOHOL, C               1O,.1202
600., Amylic alcohol is a peculiar oily substance, which is collected in the process of distilling  spirit from  potatoes.  It is
supposed to be formed from the starch (amyhlm) of the potato,
and hence its name.  It is also called potato oil, and fusel oil.
It is found in some kinds of brandy, and in other spirituous
liquors, being probably formed during the fermenting process,
in circumstances not well understood.
In distilling spirit from potatoes, it is particularly abundant
towards the close of the process; it is then mixed with water, to
which it gives a milky appearance, but after standing for a time
it rises to the surface.
Amylic alcohol is a clear, colorless liquid, insoluble in water,
but very soluble in alcohol and ether.  Its density is 0'82, and
it boils at 2700.  Its taste and smell are burning and pungent.
If its vapor, mixed with air, is breathed for a little time, asthmatic
pains and coughing are likely to ensue, and even vomiting.
It dissolves phosphorus, sulphur, and iodine, without change;
and, unlike wine alcohol, is congealed by a temperature of -40~.
The formula of amylic alcohol, CloHl202, answers to 4 vols. of the substance in the gaseous state. The calculated density of its vapor is 3.057.
Thus,
10 vols. carbon vapor weigh   ('836 X  10)    8.360
24  "  hydrogen       "       (069      24)   1'656
2  "  oxygen         "      (1106 X   2)   2.212
Thus, 4 vols. amylic alcohol vapor weigh     12-228
The weight of 1 vol., or the density, is therefore 3'057
QUESTIONS.-598. What do the formiates resemble in their general
pr'olperties?  599. )escribe methylal.  600. From what is amylic alcohol
obtained?  Describe its properties.  When its vapor, mised with air, is
breathed, what is the effect?




AMYLIC  ALCOHOL.                          431
Product of the Oxydation of Amnylic Alcohol.
601. Valerianic Acid, C,oH,04- = Co11903JI10. — This acid
sustains the same relation to amylic alcohol as acetic acid sustains
to wine alcohol, or formic acid to methylic'alcohol.  It is contained  in the valerian  root (valeriacna  o2ficinalis), which  is
extensively used in medicine, and is obtained by distilling the
root with water.  It is also formed artificially by dropping warm
potato oil upon platinum black in contact with atmospheric air,
or by distilling a mixture of amylic alcohol, sulphuric acid, and
bichromate of potash.
In the process of its formation from amylic alcohol, the same
chemical changes are required as in the formation of acetic acid
from wine alcohol; —the alcohol loses 2 eq. of hydrogen, which
combine with oxygen, forming water, and then 2 eq. additional
of oxygen are absorbed. Thus,
(,o011,2O  + 20: CoT-T,,loO  + 2HO. and
CloHloO2 + 20 = Clo0H204.
Pure valerianic acid is a colorless, oily liquid, of specific gravity
0'937.  Its taste is pungent and acid, and its odor like that of
valerian.   Its boiling point is 3470~.   It is little soluble in
water, but dissolves freely in alcohol and ether.  It combines
with bases, forming salts in many respects similar to the acetates
and formates.  When it enters into combination, it gives up the
elements of 1 equivalent of water, precisely like the acetic and
formic acids, and is therefore monobasic.
Some of the valerianates, especially valerianate of zinc, are used
in medical practice, as a substitute for the preparation of the
valerian root.
602. Amynlic aldeihyde, CoHIo02, analogous to the aldehyde of wine
alcohol, is formed by distilling valerianate of baryta.
QUESTIONS. —601. From what is valerianic acid obtained? How may
it be formed artificially?  Wlhlt is said of the chemiczal cllanges wvhiol
take place in its formation?  Describe its properties.  Whlat salt of this
acid is used in medical practice? 602. Ilow is anmylic alcollol obtained?




432                SULPHUR  Ar, CO HOLS.
The three alcohols above described are the most important of this
nomologous series (547), but six others are known, which will be hereafter described.  These all have the formula, C211112(1+ 1)02, as we have
before (545) seen.
Some other compounds, similar in their properties to the above, but
not strictly homologous with them, have been denominated alcohols, as
phenylic alcohol, C 2H602, and acrylic alcohol, C6H602.
SULPHUR  ALCOHOLS, OIR  MERCAPTANS.
603. These compounds are formed on the same type as the
alcohols, but differ from them by containing sulphur instead of
oxygen.  They are called mercaptans (nzercuriumn captans), because of their great affinity for mercury, with which they eagerly
combine, on coming in contact with its oxide.
Wine-alcohol Mercaptan, C4,682,    C4H5S, IS. -  This compound is formed by saturating a solution of caustic potash, of
density 1'3, with sulphuretted hydrogen, and distilling it with an
equal measure of sulphovinate of lime (a substance to be hereafter described,) of the same density.  It is a colorless liquid,
which has a specific gravity of about 0'84, and boils at 970~.  Its
odor resembles that of onions.
iMercaptan vapor has a density of 2-152, as may be thus calculated:
4 vols. carbon vapor weigh    (.836 X  4)   3.344
12 vols. hydrogen... ('069 X12)'828
f vol. sulphur   "."    (6 654 X  -)  4'436
4 vols. imercaptan vapor                    8'608
The density therefore is, or the weight of 1 vol., 2 152
By the action of this compound upon metallic oxides, 1 equivalent of its hydrogen unites with the oxygen of the oxide, forming
water, and the metal takes the place of the hydrogen in the original compound.   Thus, by the action of mercaptan  on oxide
of lead, PbO, we haveC41I682 + PbO-C4H5S,PbS + IIO-C4HI5PbS2 + HO.
These metallic compounds, of which several more are known,
are called mnercaticles.
QuEsTIoNs.-Are there other alcohols besides the three described
above?  603. What are the mercaptans, or sulphur alcohols?  Describe
wine alcohol morcaptan.  What are the compounds of this substance with
the metals called?




ETIHER S.                          433
The compound, C44SS, called nzercacptan ctdehyde, is known, as aro
also mnethTylic nlercaptan, C2H4S2, and acmylie rncrcaptoan, Clo0-112-2.
Selenium may be made to replace the sulphur in the commlon alcohol
mercaptans, forming scleno-me-rcaptans.
ETIHERS.  COUPLED) OR  VINIC  ACIDS.
604. The substance usually designated by the simple term,
ether, is a compound obtained by the reciprocal action of alcohol
and acids, as, the sulphuric, phosphoric, or arsenic, or the
chlorides of zinc, tin, &c.  It is often called supl'huric ether,
from the circumstance that sulphuric acid is generally used in its
preparation. The name ether, given to it, indicates its volatility.
But the term  is now extended to a very numerous class of
similar compounds, most of which are liquid at ordinary temperatures, and are very volatile, but differ from each other as to the
temperature at which ebullition takes place. Some few of them
are solid.
There are several families of ethers derived from  the several
alcohols; and in naming them, except in the case of those belonging to the common alcohol group, the family or group is
usually indicated.  Thus we have hydrochloric ether, methylic
hydrochloric ether, and amylic hydrochloric ether; the first of
which belongs to the wine alcohol group, but the others to the
groups severally indicated.
And in each alcohol series, there are also two distinct classes
of ethers, which we may call simple ethers, and comnpoundec ethers.
The former, or simple ethers, have the general formula, C2,,H-2,,+ la
(the Greek letter A being used to indicate one equivalent of any
one of the elements, oxygen, chlorine, bromine, iodine, fluorine,
sulphur, selenium, tellurium, or a compound radical, cyanogen,
bisulphide of carbon, &c.,) while the compound ethers always
contain an acid in combination with a simple ether, C,(2,,+,A.
Thus, common sulphuric ether is a simple ether, C4H1O; but
QUESTIroNS.-604. IHow is the compound usually called ether obtained?
Why is it often called szulphuric ether? How is the name ether now used?
Do the different alcohols afford ethers?  What two classes of ethers are
there in each alcohol series?  In what do the individuals of the two
classes differ?
37




434                        ET HFR s.
nitric ether is a compound ether having the formula, C4HNO, 
4'50O,N05.
There are some simple ethers which contain more than one
equivalent of a; and in both the simple and compound ethers,
one or more equivalents of the hydrogen may be replaced by
chlorine (and possibly other elements), as in the chlorocarbonio
ether, C4H3,C20lCO.
Ethers of Wine Alcohol.
I. SIIMPLE ETE RS.
605. lEther (Sulphuric Ether), C04,50.- This ether may be
formed by several modes; but the best is to distil a mixture of
equal parts of alcohol and strong sulphuric acid in a glass retort,
the process being discontinued as soon as the mixture begins to
become colored.  For distilling it, an alembic or other distilling
apparatus (48) may be used.
The product should be washed with water, to separate a little alcohol
and sulphurous acid that usually pass over with the ether. This is done
by filling a bottle about half full with the impure ether, and then pouring
in a quarter or one-half as much water, and shaking them well together.
After standing a few minutes, the liquids separate, and the water may
be drawn off by perforating the cork and inverting the bottle, taking
care to notice when the water has all escaped.
Pure sulphuric ether is a colorless liquid, of a hot, pungent
taste, and fragrant odor.  At the temperature of 600, its density
is 0'72, and it boils at 96~ or 98~ in the atmosphere, and at about
40~ below zero in a vacuum.  In the open air, it evaporates with
great rapidity, producing intense cold, so that water may easily
be frozen by it. It is very combustible, and burns with a yellow
flame.  Exposed to the light, in vessels partly filled with air, it
gradually absorbs oxygen, with the formation of acetic acid.
The solvent powers of ether are not as extensive as those of
alcohol, but it dissolves the essential oils, resins, and many of the
fatty principles.
606. When the vapor of ether is inhaled, it first produces a
species of intoxication, similar to that occasioned by exhilarating
QUEsTIoNs.-G605. Describe the mode of preparing ether.  What are
its properties? 606. What is the effect when vapor of ether is inhaled?




ET I ER S                          435
gas; and afterwards a kind of stupor follows, during which the
person is nearly insensible to pain; the effect being much the
sarne as that produced by chloroform.  When used for this purpose, it has been called letheon.
607. Suilp7ovinic Acid.- Theory of the Formation of Ether. —
By comparing the formula of alcohol, C4I-I602 =  C4,IIO,O, with
that of ether, C,41150 it is evident that the former may be considered as a hydrate of the latter; and the effect of the acid upon
the alcohol in producing ether is simply to abstract from  it one
equivalent of water, or its elements.  But although this is the
final result, other intermediate chemical changes take place.
When equal parts of sulphuric acid and alcohol are mixed, and
slightly heated, sulphovinic acid, C,0H50,2S03,HO, is first formed,
and may be obtained in a free state, as a syrupy liquid.  This
acid is capable of combining with bases and forming salts, which are
called sulphovinates, as sulphovinatIf baryta, BaO,C4H130,2SO,,
and sulphovinate of lime, CaO,C,4H0J,2S03.  These, and sulphovinates of other bases, are easily obtained in crystals.
Sulphovinic acid, though very stable at ordinary temperatures,
is decomposed when heated to about 310~, and ether is separated
in the gaseous state, and may be condensed, the sulphuric acid
and water remaining behind.   Thus we have, neglecting the
water of the oil of vitriol,
C4H602,2S03 =   4H50 + 2S03,H0.
608. By using alcohol nearly pure, and regulating the temperature
constantly at about 3000, both the ether and the water formed from the
alcohol may be made to distil over together, leaving unchanged the acid,
which has produced the whole effect.
Let A (see figure on next page) be a flask, with rather a wide mouth,
containing a mixture of five parts of alcohol and eight parts of sulphuric
acid, so as to fill it about half full. In the cork insert a bent tube, B,
through which the alcohol required in the process is to pass, and another, C, to connect with the condenser of the distilling apparatus (96);
QUESTIONS.-607. Why may alcohol be considered a hydrate of ether?
What is the effect produced upon alcohol by sulphuric acid? What is. first produced when equal parts of alcohol and sulphuric acid are mixed?
What is the composition of this acid? Is it capable of forming salts with
batses? What is the effect when sulphovinic acid is heated?  608. De]
scribe the mode of forming ether by a continuous stream of alcohol.




and  between  them
place  a  thermometer, T, the bulb of
which  must extend
f ~~+~v  __C _                   to the mixture with~       IfH       v           D 11 bv in, to determine the
temperature. So also
the alcohol tube, B,
should extend a little
below the surface of
the liquid, as repre.o
sented in the figure.
When  the  mixture
has  become  suffinF'-'~~     ciently  heated,  a
continuous stream of
0  alcohol is made to
enter, just so as to
keep  the liquid  in
the flask at its original level. The supply of alcohol is regulated by the stopcock
in the vessel D), which
must be supported a
Preparation of Ether.           little above the flask
by a shelf or stand.
['he ether and water that pass over are, of course, collected together;
but, as they do not mix, the ether is easily separated.  The mixture,
during the operation, should be kept continually boiling, and the heat
very carefully regulated.
The ether, after being separated from the water, should be redistilled
from  a weak solution of caustic potash, to separate it from  any acid
which may have passed over with it.
609. Many other acids, as the phosphoric, arsenic, carbonic,
oxalic, tartaric, &c., produce with alcohol vinic acids-called also
coypled acids-which  are entirely similar to the sulphovinic.
Such acids are properly to be considered as bibasic (or tribasic).
To indicate the basic character of the water in sulphovinic
acid, we may write its formule, HEO,C,1150,2SO,; -now  this
water may be replaced by another equivalent of ether, C4H10,
and we then have the compound, 2(C4H50,SO3), which is perfectly neutral, and is called a cornozud ether.
Q-usfTIONs.-C609. What other acids are mentioned as capable of forming'inic or coupled acids with alcohol?  To what class of acids do th.Ov
belonp:?




ET HERS.                           437
Some acids, as the sulphuric, oxalic, and carbonic, form both
vinic acids and compound ethers, while others, as the phosphoric,
form only vinic acids; and others still, as the nitric and acetic,
form only compound ethers.  Acids of this latter kind are strictly
monobasic.
Besides the acids, several of the chlorides (604), as the chlorides
of zinc and tin, and the fluoride of boron, effect the transformation
of alcohol into ether, with the elimination always pf an atom of
water.
By distillation with an alkaline solution, the compound ethers
and vinic acids are decomposed, and alcohol reproduced. In this
case the acid of the compound ether, or vinic acid, combines with
the alkali; and the ether, C4E150, as it is set free, unites with
an atom of water, thus reproducing alcohol, CH4602.
610. Hydrochloric Ether, (J4H1Cl.-This ether is formed by
saturating common alcohol with hydrochloric acid gas, and then
distilling with a very moderate heat.  As the vapor distils over,
it; should be made to pass through warm water, to free it from
impurities, and is then to be condensed in a receiver surrounded
by ice.
It may also be formed by distilling a mixture of equal parts
of alcohol and  the hydi'ochloric acid of commerce, and by
other means.
The reaction producing it is shown by the following equationC4t1602 + HC            1 = C4H5C1 + 2HO.
This ether is a colorless liquid, which has a density of 0'874,
and boils at the low temperature of 520. In the warm weather
of summer, it can be preserved only in tubes hermetically sealed.
By its formula it will be seen that its composition is the same
QUEsTIoNs.-What acids are mentioned as forming both vinic acids
and compound ethers?  What as forming only compound ethers?  What
is their character?  What other compounds are mentioned as being
capable of transforming alcohol into ether?  How are the compound
ethers and vinic acids affected when distilled with a solution of alkali?
610. How is hydrochloric ether formed?  What are the reactions by
which it is produced when alcohol and hydrochloric acid are used? What
Iar- sonie of the properties of this ether?
37 *




438                            ETHERS.
as that of sulphuric ether, except that the oxygen of the latter
substance is replaced by chlorine.
By passing a current of chlorine through a portion of this ether, in
direct sunlight, 1 equivalent after another of the hydrogen is replaced
by chlorine, until at length it all disappears, and we have only the compound C4C16.  We have therefore the following series of compounds, viz.:
Boiling Point.    Density.
Hydrochloric ether........ C4H5C1....... 52~.......  0'874
Bichlorinatgd  do........ C4H14C12....... 1470.......  1-174
Trichlorinated do........ C4H11C13....... 1670.......  1 372
Quadrichlorinated ether  C4H2C14....... 21510.......    1 589
Quinquechlorinated do.. C4HC15....... 295~.......  1,640
Sesquichloride of carbon C4H6 - C2T-I.......  356G
611. l/ydrobromic Ether, C14H5Br.-This ether is prepared firom a mixture of alcohol, phosphorus, and bromine.  It is a colorless liquid, having
a density of 1'47, and boiling at 1060~.
lydlriodic Ether, C4H51.-Preparation similar to the preceding.  It is
a limpid liquid, of density 1'97, and boils at 158~.
Ilydrosulphuric Ether, CJHsS.-This ether is very volatile, colorless,
and of a penetrating, nauseous odor.  its density is 0-825, and its boiling
point 163O~.
Hydrocyanic Ether, C4H,5Cy.-A poisonous, volatile liquid, of density'787, and having its boiling point at 180~.
iI. cOBIPOUND ETHERs.
612. Sulphuric Ether (proper), C4H50,SO,.-This is the only
compound properly called sUtlphuric ethe-r, on the principles adopted
in naming the other compound ethers.
It is obtained by the action of anhydrous sulphuric acid upon
ordinary ether.  It is a neutral, oily liquid, havidfg a density of
1'12, and a sharp, burning taste.  Heated to 285~ or 3000), it is
decoulposed, so that its boiling point cannot be ascertained.
613.  l1yponitrous Ether, C4HsN4O, -    41H      O,NO3. —This ether
may be formed by the direct action of nitric acid upon alcohol;
but a better mode is to  pass a current of nitrous acid  vapor
(obtained by the action of nitric acid upon starch) through dilute
QuESTJlONs.-What is the effect when a current of. chlorine is passed
thirough hydrochloric ether?  611. What other simple ethers are mentioned l?  i1.2. VWhat is the composition of sulphuric ether proper i'  low
is it obtaitiled?  613. Describe hlyponitrous ether.,




ETHERS.                           469
alcohol.  Heat is generated by the process, and the vapor is
condensed in a cold receiver.  As the action of the acid upon
the alcohol is often very tumultuous, the process should be conducted with caution.  Hyponitrous ether is a liquid of a pale
yellow color, and fragrant odor; its density is about 0'94, and it
boils at 70~.  In a pure state it cannot be kept long; but mixed
with alcohol it is more permanent, and is extensively used in
medicine, under the name of sweet spirits of nzitre.
Nitric Ether, C4H5NO, -   4I5C, 0,N05.-Nitric ether is formed
bv distilling equal parts of nitric acid and alcohol with a few grains
of urea.  It is a colorless liquid, of a sweet taste, and is heavier
than water.  It boils at about 185~, and its vapor explodes
by heat.
614. Carbonic Ether, C4H50,CO2..-This ether is obtained by
distilling oxalic ether (soon to be described) with potassium  or
sodium.  It is a colorless liquid, very volatile, and having an
aromatic odor and acrid taste.  Its density is 0'975, and it boils
at 2590.  With chlorine it yields several chlorinated carbonic
ethers, by the replacement of 1 or more equivalents of the
hydrogen of the simple ether, (4H150) by an equal number of
equivalents of chlorine.
615. Silicic Ethers.-Silicic ethers, of which there are two (or
perhaps three), are formed by the action of chloride of silicon
upon absolute alcohol. They are volatile liquids, having a penetrating odor and a pungent taste. By water, or by long standing
in bottles, from whichthe air is not perfectly excluded, they are
gradually decomposed; and the hydrated silica is left in hard,
vitreous masses, resembling quartz.
Acetic Ether, CHs04 -- C4H50,,C,4,30,. - Acetic ether may
be prepared by several modes, but the best is to distil a mixture
of 3 parts of acetate of potash, 3 of absolute alcohol, and 2 of
sulphuric acid.  Acetic ether is a volatile liquid, of a fragrant
odor, like that of strong vinegar.  It boils at 165~, and has a
density of about 0'89.
QUESTIONS.-What is said of nitric ether?  614. Of what is carbonic
ethler composed?  615. What is said of the silicic ethers?  What of
acetic ether?




440i                       E T H E R S.
616. Oxalic Ether, CHO,54- C4H50,C2,O,.-This ether is prepared by distilling a mixture of 4 parts of binoxalate of potash,
5 parts of sulphuric acid, and 4 of strong alcohol, and thoroughly
washing the product with water. It is a volatile liquid, which
has an aromatic odor, and is a little heavier than water.
Oxalic ether is decomposed by contact with an alcoholic solution
of potash, forming alcohol and oxalic acid. Ammonia acts upon
it, producing  two compounds, called oxamide, C,O2NH2,, and
oxamic acid, C45NH112,HO.   By the action of chlorine upon
it, several chlorinated compounds are formed.
617. Formic Ether, C611604 =  C4H50,C2HO,. —This ether is
formed by distilling a mixture of dry formiate of soda, sulphuric
acid, and strong alcohol.  It is also produced in considerable
quantity during the process for preparing fulminating mercury,
to be hereafter described.
Formic ether is a colorless liquid, which boils at about 1300,
and has a specific gravity of 0'915.  It has a very penetrating,
agreeable odor, and is soluble in about ten times its weight of
water.
Many other compound ethers of the wine alcohol series, cannot be hero
described. Recent writers enumerate nearly a hundred, formed by the
organic acids alone.
In their composition they evidently possess the character of salts,
being formed by the union of ether, C41150, acting as a base, with the
several acids; but in their properties they differ essentially from proper
saline compounds. This appears in the fact that the acid cannot be
detected by the ordinary tests; thus, oxalic ether is a compound of
vinic ether, C4H50, and oxalic acid, C203; but lime, which separates
oxalic acid from its saline compounds, forming oxalate of lime, will not
separate this acid from oxalic ether.
The same remark applies to the coupled, or vinic acids.
Ethers of Methylic Alcohol.
I. SIMPLE ETHERS.
618. XMethylic Ether —Wood Ether, C2H3O. - This ether is
formed from methylic alcohol, in the same manner as sulphuric
QUESTIONS.-616. How is oxalic ether prepared?  617. Formic ether?
How are the compound ethers formed? Are they really salts? Do they
differ in any respect from proper saline compounds?  Illustrate with
reference to oxalic ether.  618. IIow is methylic ether formed?




ETHERS.                            441
ether is prepared from common alcohol, by distilling methylic
alcohol with an equal volume of sulphuric acid.  It is a colorless gas, of a pungent odor and taste, and is rapidly absorbed by
cold water, but given off again unchanged by boiling.  It is condensed to the liquid form by a temperature of -3~; and is chiefly
interesting as taking the place, in this series, which the ether first
described (605), sometimes called sulphuric ether, occupies in the
common alcohol series.
The theory of its formation corresponds in every respect with
that already explained (607) in describing ordinary or sulphuric
ether.  When methylic alcohol and sulphuric acid are mixed,
at a moderately elevated temperature, sulplho-methylic acid is
formed, having the composition, CH40,,2SO3= CH,0,2SO,,HO,
which, by further elevation of temperature, is decomposed; the
imethylic ether being separated, and the sulphuric acid and water
alone remaining.
619. Hydrochloric Methylic Ether, C2,11C1. —This compound
is formed by distilling a mixture of common salt, wood-spirit, and
oil of vitriol.  It is a colorless gas, of a peculiar odor, and corresponds to the ether of similar name in the common alcohol
series; the oxygen of the preceding compound being replaced by
chlorine.
It is not reduced to a liquid state by a temperature of zero.
By the action of chlorine upon this ether, in the direct rays of the sun,
the several equivalents of hydrogen may be successively replaced by
chlorine, as heretofore shown in another case (610), and important compounds formed,-the formulae of which, with their densities and boiling
points, are given in the following table:
Boil. Point. Density.
Hydrochloric methylic ether, C2H3C1.....  0'0~...... 1.74
Bichlorinated    "         C3HC1...... 8.....87.  134
Trichlorinated   "     "   C2HC13...... 1420~..... 1'49
Sesquichloride of carbon,   C0114...... 1720...... 1'60
620. Chloroform, C11HC13, is the trichlorinated compound of
this series.  It is produced by the direct action of chlorine
Q-(usrTINxs.-What is said of the relation methylic ether sustains to
nethylic alcohol?  What is sulpho-methylic acid?  619. Describe hydrochloric methylic ether. What is the effect when a current of chlorine is
made to pass through this ether?  620. What is chloroform?




4 142                      E THERS.
upon hydrochloric methylic ether, but the best method of preparing it is to distil a mixture of hypochlorite of lime (common
bleaching salt) and wine alcohol, or wood-spirit.
Chloroform is a dense, oily liquid, of an agreeable ethereal odor,
and sweetish taste.  It is not dissolved by water, but mixes readily
with alcohol.  Its density is 1'49, and it boils at about 1420.  By
breathing its vapor mixed with atmospheric air, a kind of intoxication is produced, much like that occasioned by exhilarating gas, or
the vapor of sulphuric ether.  If the vapor is breathed some time,
total insensibility to pain is produced, and loss of consciousness,
during which difficult surgical operations may often be performed,
without even the knowledge of the patient.
It readily dissolves caoutchouc and gutta percha, and solid
carbonic acid.
By alcoholic solution of potash, chloroform is changed into
formniate of potash and chloride of potassium. It was this circumstance that suggested the name chloroform.
rodoformn, C2HIs, bromoform, C2HBr3, and sulphoform, C2HS3, are analogous compounds of iodine, bromine, and sulphur.
621. Hydriodic Methylic Ether, C2H3I, is a colorless liquid, obtained
by distilling a mixture of iodine, methylic alcohol, and phosphorus. It
is remarkable for its great density, which is 2'24.
Hydrobromic Methylic Ether, C,2HBr, is prepared in a manner similar
to the above, only substituting bromine instead of iodine. It is liquid at
temperatures below 55~.
Hydrosulphuric Methylic Ether, C2H3S, is a liquid, of a density 0'845,
which boils at 1060.
Still other simple methylic ethers are known, but they cannot be here
described.
II. COMPOUND METHYLIC ETHERS.
622. Sulphuric Methylic Ether, C,H,O,SO3.-  This ether is
formed by distilling 1 part of methylic alcohol with 8 or 10 parts
of sulphuric acid. It is a liquid, having a density of 1'32, and
boils at 370~.
Nitric Methylic Ether, C2113N06 = CH,30,NO5. —This ether
corresponds to the ether of similar name in the common alcohol
QuESTIONS. —How is chloroform prepared?  What use is made of it?
6(21. What other methylic ethers are mentioned?  622. How is sulphuric methylic ether formed?  Describe nitric methylic ether?




ETHERS.                           443
series. It is formed by distilling a mixture of wood-spirit, nitrate
of potash, and sulphuric acid.  It is a dense, colorless liquid,
which boils at about 1500. Its vapor, when heated to 2480, is
decomposed with a violent explosion.
Oxalic lethylic Ether,  4H304 —       C2H0,CO203. -- Oxalic methylic ether is prepared by distilling a mixture, in proper proportions, of sulphuric acid, binoxalate of potassa, and methylic
alcohol.  At ordinary temperatures, it is a white crystaline solid,
which melts at 1240, and boils at 322~.
Acetic lethylic Ether, 061604 -      H3,O, C,,,4H3. —This ether
is formed by distilling an acetate with methylic alcohol, and sulphuric acid. It is always formed in the distillation of wood. It
is a colorless liquid, of an agreeable ethereal odor, and has a specific
gravity of 0'919.  It boils at a temperature of 137~.
The close resemblance between the methylic ethers and those of the
common alcohol group will be seen at once.  There are many more
of this group, which cannot be here described, late writers enumerating
more than seventy.
Ethers of Amylic Alcohol.
623. Amylic alcohol, treated with sulphuric acid, produces
sulphoamylic acid, similar to the sulphovinic and sulphomethylic
acids, which is easily obtained in combination with bases, but
with difficulty in a free state.
Treated with an excess of concentrated sulphuric acid, and
heated to boiling, a carburetted hydrogen, CoH,,, is obtained,
called amylene, which is a volatile, colorless liquid, boiling at
1020. At the same time two other compounds, isomeric with
it, are usually obtained, called _paramylene, C2oHo2 and metamyp
lene, C40H140.
624. Amylic Ether, C,oH,1O. —This ether is prepared from
the hydrochloric amylic ether, to be next described, by the action
of a strong solution of potassa.  It is a liquid of an agreeable
odor, the boiling point of which is about 2340~.
QUEsTIONs.-What is said of the resemblance between the methylic
ethers and those of the common alcohol series? 623. What is said of the
sulphoamylic acid? What is amylene? What two substances isomeric,
with it are mentioned?  624. What is amylic ether?




444                    VOLATILE  OILS.
This ether, it will be seen, corresponds precisely to common
ether in the wine alcohol group of ethers, and to methylic ether
in the methylic alcohol group.
IHydrochloric Amylic Ether, CoH,1C1.-To obtain this ether,
equal parts of amylic alcohol and perchloride of phosphorus are
distilled in a glass retort, and the vapor condensed in the ordinary
mode.  It is a colorless liquid, with an aromatic odor, and boils
at about 215~.
It m ay also be obtained by the action, long continued, of hydra..
chloric acid upon alcohol.
625. Hlydriodic amylic ether, CloHlI, and hydrosuliphuric amylic ether,
CloHlNS, are known. The latter has the smell of onions.
Acetic Amylic Ether, C14111404= Clo01,O,10C4303. —To prepare acetic
amylic ether, equal parts of amylic alcohol and oil of vitriol are distilled
with 2 parts of acetate of potash, and the resulting liquid purified. It is
a limpid liquid, a little lighter than water, with an agreeable aromatic
odor. Its boiling point is 257~. By some its composition is said to be
3(CHnT1O),C4HsOo.
The odor of this ether closely resembles that of the ripe banana fruit,
and it is used to give the banana flavor to sugar-candy.  The preparation
is sometimes called banana drops.  The peculiar flavor of many ripe
fruits may in this mode be very closely imitated by the use of ethers.
Oxalic Amylic Ether, C12hT1103=0 11o0IlO, C20,-This compound is procured by distilling a mixture of amylic alcohol and oxalic acid.  It is
liquid at ordinary temperatures, and boils at 500~. Its odor is exceedingly offensive.
VOLATILE) OR ESSENTIAL OILS.
626. These oils constitute a very numerous class of compounds,
and, as the name indicates, are distinguished by being volatile at
ordinary or slightly elevated temperatures.  Most of them  are
liquid at a temperature of 500, or above; but a few are solid, as
common camphor.
They are also usually distinguished by their powerful odor,
which is often very agreeable.  Most of them  are obtained from
QUESTIONS.-What relation does amylic ether sustain to this series
of ethers?  What other ethers of this series are mentioned?  625. What
is said of the odor of acetic amylic ether?  626. What is said of the
volatile oils?  Are any of them solid at ordinary temperatures?  What
is said of their odor? From what are they obtained?




VOLATITLE OILS.                          445
the leaves and stalks of plants, but some are found in the flowers,
fruit, bark, wood, or in the pericarp.
In general, these oils are obtained by distilling the part of the
plant containing them, with water;-both the oil and the water
pass over in vapor, and are condensed in the usual mode; and are
afterwards separated by the oil rising to the surface.  In a few
cases only is the oil heavier than water, when,
as a matter of course, it sinks to the bottom.
To separate such as are lighter than water, a    A
vessel of the form represented in the margin answers
well. It is simply a vessel of proper size, with a
small spout which starts nearly from the bottom,
and rises nearly as high as the mouth. It is first
filled with water to the line A, and then the mixed
liquids are poured into it in a small stream, the oil
remaining at the surface, while the water escapes            I l
at C. This, it is evident, may be continued until          I
the vessel is nearly filled with the pure oil; or until,   _-  _
if more were added, the oil itself would begin to
escape by the spout C.                           Separating Volatile Oils.
Water is necessary in the distilling process, to prevent the decomposition of a portion of the oil by the heat; and in most cases the
distillation can be effected in this mode, even though the boiling
point of the oil be considerably above that of water.  In some
cases, a higher temperature than 2120 is required, when sonle
soluble salt is added to the water, as common salt; a saturated
solution of this compound boiling at about 2300~
Some few of the essential oils are obtained from the plant
by pressure, or by the action of a solvent, as alcohol or ether.
627. These oils being volatile, if a small portion is dropped on
a piece of white paper, the stain produced soon disappears, especially if the paper be warmed. In this way they may be distinguished from other oils, which produce upon paper a permanent
stain.
Most of the essential oils consist of at least two principles; one
of which is less fusible than the other, and may be separated by
cold.  Thus, exposing oil of peppermint to severe cold, a solid
QTESTIONS.-Why is water necessary in distilling these oils? 627. How
may the volatile oils be distinguished? What is said of the composition
of most of them?
38




44t                   VOLATIEL   OILS.
not unlike camphor is crystalized out, and may be separated from
the portion that remains liquid. These solids, sometimes called
stearoptens, are different in the different oils; some being much
more easily solidified than others.   Their composition is also
various; some being isomeric with the oil which yields them, and
others, hydrates or oxides of the oil.
Most of them exist, as such, in the plant or part of the plant
from which they are obtained, but some are formed in the process
of distillation frorn materials contained in the substance distilled.
628. If we have regard to the elements of which these oils are composed, we may divide them into three classes, viz.:
1. Oils composed entirely of carbon and hydrogen.
2. Oils which, in addition to the above elements, also contain oxygen; and
3. Oils of which sulphur is an ingredient;-these also usually contain
nitrogen.
Carbo-h7iydrogye  Volatile Oils.
629. Oil of Turpentine —Camphene, C2oH,1. —This oil is procured by distilling common turpentine with water.  Turpentine
is obtained from several species of the pine, in the wood of which
it is contained in large quantities.  At the proper seasons of the
year, incisions are made with an axe in the trunks of the trees,
fiom which it gradually exudes, and is collected and preserved.
This viscous substance is a solution of resin (common rosigl) ill
oil of turpentine, and the latter is separated in the process of
distillation.
Common spirits of tuTpenltine is an impure camphene, containing a portion of resin in solution.
Exposed to the air, oil of turpentine evaporates rapidly, but at
the same time oxygen is absorbed, and a portion of the oil is converted into resin, which remains in solution.  It can therefore be
preserved pure only in vessels from which the air is perfectly
excluded.  When pure, it is a limpid liquid, of specific gravity
0'87, which boils at 315~.
QUESTIONS. —DO the essential oils exist ready formed in the plant?
628. Into what three classes may they be divided?  629. 1-ow is oil
of turpentine procuredl?  Frorn what is it obtained?  What are the
ordinary spirits of turpentine?




VOLATILE  OILS.                           447
Oil of turpentine is not soluble in water, but dissolves readily
in alcohol and ether, and in other essential oils.  Mixed with
three or four times its volume of strong alcohol, it constitutes the
ordinary burning fluid.
When left for some time in contact with water, a portion of the two
unite, forming a solid hydrate of canphene, which has the formula,
C2oH,6,6HO.  Other hydrates may: also be prepared, containing, severally, 4, 2, and 1 equivalents of water.
Many substances, as caoutchouc, insoluble in alcohol and ether, dissolve readily in this oil, which renders it an important substance in the
arts.  It is also largely used in mixing paints, in the manufacture
of varnishes, and in the practice of medicine.
630. I~T/drochlorate of camphene, or artificial camphor, C20H116, C1, is
prepared by passing a current of dry hydrochloric acid gas through pure
oil of turpentine.  It makes its appearance as a white crystaline solid,
which melts at about 302~, and may be sublimed, without change, at
about 8380.  In many of its properties it closely resembles common
camphor.
The portion which remains liquid has the same composition as the
crystals, but it cannot be solidified, so far as is known, by any temperature.
IIydriodic and hydrobromic acids form with oil of turpentine compounds similar to those formed by the hydrochloric.
Sulphuric and nitric acids act readily upon oil of turpentine, forming
several interesting compounds.
631. Oil of Lemons, C,1o1. —This oil is obtained by pressure
from  the yellow part of the peel of the fruit, and is isomerie with
the preceding, having the same ultimate composition, but its equivalent being only one-half that of oil of turpentine. By distillation it
yields two oils, which differ in their boiling points.
Oil of lemons has a specific gravity of 0'847, and it boils
at 338~.
By the action of hydrochloric acid, it forms two camphors,
similar to those formed from oil of turpentine, one being solid
and the other liquid.
Orange peel yields an oil isomeric with the above, but having a different specific gravity, and a different boiling point.
Oil of elenmi, oil of juniper, oil of pcper, &c., have a similar cormposition
to the above, and they are all isomeric.
Q.UESTIONS. -What is the effect when oil of turpentine is left in contact
with water?  What use is made of this oil?  630. What is artificial camt.plior?  I-low is it formed?  631. Describe the oil of lemons. What is
baid of oil of elemi, oil of juniper, &c.?




448                   VOLATILE OILS.
Oxygenated Volatile Oils.
632. Oil of Bitter Almonds.-Benzoic Series of Compounds.
-Bitter almond oil, C14H,602, is obtained from the kernels of
bitter almonds by distillation with water after the fixed oil contained in the seed has been expr'essed.  It does not pre-exist in
the seed, but is formed from  the amygdaline of the seed, in a
manner soon to be explained.  Its density is a little above that
of water, and it boils at 3560. It is quite colorless, and has a
pungent taste and fragrant odor, and is poisonous.
After the fixed oil has been expressed, the pulp is allowed to
stand for some hours, and a kind of fermentation takes place in
the amygdaline by virtue of' the presence of another proximate
principle contained in the almond, called synaptase, or emulsine.
During this fermentation there are produced, besides the oil,
hydrocyanic acid and glucose.
633. Anygdaline, C4oH07NO22, may be obtained in a free state. It is a
crystaline, colorless powder, very soluble in water and alcohol. Synaltase
also may be isolated;-it is a yellowish-white solid.
634. Chlorinated Oil of Bitter Almonds-Chloride of Benzyle, C14I5ClO02.
-This substance is obtained by passing a current of dry chlorine through
oil of bitter almonds, and expelling the excess of chlorine by heat. It is
a colorless liquid, heavier than water, and has a peculiar, disagreeable
odor. It is formed from the oil by the substitution of an atom of chlorine
for one of hydrogen. Iodine and bromine form similar compounds.
When this chlorinated oil is treated with gaseous ammonia, there are
formed benzaomide, C14H502,NH2, and hydrochlorate of ammonia, Thus,
C14H5C102 + 2NH3 = C1,4H502,NH2 + NH3,,HC1
Benzamide is a white crystaline solid, and may be entirely purified
from  the sal-ammoniac by washing it with water.  By remaining long
in contact with water, benzamide is converted into hydrobenzamide,
C42H1,N2,6HO; and this, by solution in alcohol and boiling, is reconverted into bitter almond oil and ammonia.
Benzoic Acid.-When exposed to the atmosphere, oil of bitter
almonds rapidly absorbs oxygen, and is converted into benzoic
acid, C14H604-   C,4H503,HO.  This acid is also formed when
QUESTIONs.-632. Describe bitter almond oil. From what proximate
principle contained in the kernel is the oil formed?  633. Describe
amygdaline. 634. Describe the chlorinated oil. Describe benzoic acid.




VOL ATIL   OILS.                          449
the oil is boiled with a solution of potassa.  It is a beautiful,
crystaline solid, which melts at 248~, and boils at about 463~.
It may, however, be sublimed at a temperature considerably
below its boiling point.
Benzoic acid is found in considerable quantity in the resinous
substance usually called gum  benzoin; a product of the laurus
h)emzoiin.  From  this compound it may be procured by
direct sublimation, in the following manner.  Place a
small quantity of the resin, coarsely powdered, upon a
plate of metal on a stand, and put over it a glass receiver,
having suspended in it a small twig of mint, or other
substance, as shown in the figure, and apply the heat of          _
a lamp beneath it.  In a short time the leaves will be
covered with delicate crystals of the acid.
Benzoic  acid with  bases forms numerous salts called benzoates, but none of them are of sufficient importance to require
description here.
635. Benzoic Ether, C4H,0,C,4150,  is formed by distilling a
mixture of 1 part of benzoic acid, 2 parts of alcohol, and 6 parts
of hydrochloric acid.  It is a colorless liquid, heavier than water,
and boiling at 410~. By substituting methylic instead of wine
alcohol in the mixture, benzoic-methhylic ether is formed, which
boils at 226~.
636. Benzoine, C28tH1204, is formed when crude oil of bitter almonds is
shaken with an alcoholic solution of potassa, and is separated by crystalization.  The crystals melt at 248~.  It is isomeric with the oil.
It may be sublimed without change; but by passing its vapor through a
red-hot tube the oil is reproduced.
By heating benzoine with nitric acid, it loses 2 equivalents of its
hydrogen, and a new compound is formed, called benzile.  By the addition of oxygen, benzilic acid is formed.
637. Bemzolne, C26g,1002, is a compound formed when benzoate of lime
is distilled. It is a solid, little soluble in water, but very soluble in alcohol and ether.
638. ]Bemzene, C,2HT6, at ordinary temperatures, is a liquid of specific
gravity 0'85, which boils at 187~. It is formed by distilling a mixture
of 3 parts of dry recently-slaked lime and 1 part of benzoic acid.  It is
QUESrIONS.s.-Describe the mode of subliming a small quantity of benzoic
acid.  (3;f5. Describe benzoic ether.  636. Describe benzoine.  687. Benzonei.  (38. Benzene.
q q$




450                   VOLATILE OILS.
of a sweet taste and agreeable odor, and crystalizes when cooled to 32~.
It has also been called benzol and phene; and is produced by the decomq
position of many organic substances by heat.
639. Oil of Spireea Ulmaria.-Salicine Series of Compounds.
-Flowers of the plant called meadow-sweet (spirwza ulmaaria),
when distilled with water, yield an acid essential oil, C,,H4604,
which, like the oil of bitter almonds, is of special interest because
of its intimate relations with numerous other compounds. It does
not pre-exist in the flowers, but is formed in the process of distillation.  It is a liquid more dense than water, and boils at 385~.
In composition it is isomeric with benzoic acid, and is sometimes
called salicylous acid.
640. Salicine, C2611H,014, is a substance obtained from the bark
of certain species of willow (salix), and from  many other plants,
by digesting them with water, and then precipitating the gummy
matter also contained in the solution by boiling with oxide of
lead. After precipitating the lead by means of sulphuric acid,
and sulphide of barium, salicine is obtained by evaporation in
small, white, acicular crystals.  Its taste is bitter, and it is very
soluble in hot water and alcohol, but not in ether.  Cold sulphuric acid dissolves it, forming a deep red solution.
A mixture of equal parts of salicine and bichromate of potash,
digested for some time with 6 or 8 times their combined weight
of dilute sulphuric acid, and afterwards distilled, yields salicylous
acid, or oil of spirtea ulmaria, described above.
Treated with dilute sulphuric or hydrochloric acids, or with nitric
acid, various other compounds are produced, which cannot be here
described.
641, Salicylic Acid, C14H606 = C,4UT505,HO.-This acid is formed when
salicylous acid is heated with an excess of caustic potash. The alkali is
then separated by a mineral acid, and the salicylic acid is obtained in
colorless crystals, which are soluble in boiling water and in alcohol and
ether.
When salicylic acid is distilled with an excess of lime, carbonic acid
and a new compound called phenol or phenylic alcohol, C12H1602, are
formed. Thus,
C141606 - C,12602 + 2C02.
QUESTIONS.-639. Describe the mode of procuring oil of spirte  ulmnaria.
640. Describe salicine.  How is salicylous acid, or the oil last mentioned,
obtained from salicine?  641. Describe salicylic acid. What is phenol
or phenylic alcohol?




VOLATILE  OILS.                           451
Phenol is sometimes classed with the acids, and called carbolic acid.
It resembles the alcohols in many of its properties.
642. By distilling a mixture of 2 parts of absolute alcohol, 1 part
of sulphuric, and 121 parts of salicylic acid, salicylic ether, C4H50,C14H505, 
is obtained. It is a dense liquid, boiling at 4370, and possesses acid
properties, readily combining with bases and forming proper salts. By
substituting methylic alcohol in the above mixture, and using 2 parts
of salicylic acid, we obtain salicylic vmethylic ether, C,2HO,C14H505, which
is of special interest as being identical with the chief constituent of oil
of winter-green (gaultheriaprocunebens), a substance well known, as obtained
by distilling with water the leaves and berries of this plant.
The oil is an aromatic liquid, heavier than water, having its boiling
point at 4350~.
643. Oil of Cinnamon. - Cinnamic Series of Compounds.Oil of cinnamon is prepared  by distilling with water the cinnaimon of commerce, which is the prepared bark of two or more
species of trees, found in Ceylon and other Eastern countries.
It possesses the peculiar taste and odor of the bark.  Its composition when pure seems to be C,Hs02,O but when exposed to the
air it absorbs oxygen, and perhaps undergoes other changes not
understood, so that different chemists have arrived at different
results as regards its true composition.
644. Gnnamic Acid, CHI170,,HO, is always found in the oil
after it has been kept for a time exposed to the air, and is also
contained with benzoic acid in the balsams of Tolu and Peru.
It is a crystaline solid, which melts at 264~0, and boils at
about 570~.
Cinnamic acid forms ethers with common and mnethylic alcohols, analogous to those formed by salicylic acid.
When vapor of cinnamic acid is made to pass through a glass tube
heated to dull redness, it is decomposed, and a carbo-hydrogen, C16Hs, is
formed, called cinnamene. It is a colorless liquid, of an agreeable, penetrating odor.  This compound may also be obtained from- the resinous
substance called styrax, and has in consequence sometimes received the
name styrole.
By treament with different reagents, still other compounds belonging
to this series may be obtained.
645. Oil of Aniseed.-Anisic Series of Compounds.-Aniseed
(the seeds of the anisem sativsum), when distilled with water,
QuEsTIOoNs.-642. Describe salicylic ether.  What is said of the oil
of winter-green?  643. How is oil of cinnamon procured?  644. Describe cinnamnic acid. 645. Describe aniseed oil.




~4;)/                 ~     ArVOLATILE  OILS.
yields an essential oil from which crystals are deposited at a low
te1mperature, having the composition, C20H1202.   Treated with
reagents, it forms a series of compounds known  as the anisic
series.'Among them  are anisic acinl, CjH,705,HO, which, with
Nwine and methylic alcohols, yields ethers, and anisene, C,,4H,.
These sustain the same relation to each other, and to the oil, as
cinnamon sustains to cinnamic acid and the oil of cinnamon.
646. Oil of Cumnin, obtained  by distilling  with  water the
seeds of the cuemitnum cyminunZn, treated in a similar manner
with reagents, forms a series of compounds, analogous to the
above.  Another series, called the eugenic series, is formed from
the oil of cloves or oil of pinzento.
647. Oil of Peppcrmint, C0oHU2O2, is contained in the leaves
and stem of the plant, from which it is separated by distillation
with water.  This oil is used in large quantities by confectioners;
anid in some of the western states the plant is extensively cultivated, to be distilled for the oil.  Dissolved in alcohol, it forms
the well-known  essence of.peppermzint.   This is the general
method of preparing what are called essences.
Oil of peppermint is liquid at ordinary temperatures; but,
when cooled gradually, it deposites a white crystaline steatr<open,
(')27), resembling camnphor, which has the sanie composition as
the oil.
There are very many other oxygeznatedl volatile oils, but as they
possess no properties giving them  peculiar interest, they cannot be
here described.
Su,)pl7,uretted Volatile Oils.
648. Oil of JBlack 7eustard, CTH5NS2.'-This oil does not exist, as such,
in the seed, but is formed from substances contained in them, after the
fixed oil has been expressed, as in the case of bitter almond  oil.  T1le
active substances in tlle mustard-seecl, producing the oil when the;brnised seed is digested with water, are calledl aryrosire and  r9myron'ic acid,
botih of which have been isolated; but their composition has not been
determined.
Oil of mustard is a colorless liquid, boiling at 293~, and forming a most
p:rgerlt, irritating vapor.  Treated with reagents, it formis several other
compounds.
QUESsTIONS.-646. From what is oil of cumin obtained?   647. Describe oil of peppermint. (648. What is the composition of oil of black
marIustard?




VOLATILE  OILS.                         453
649. Oil of Garlic, C6H15. —This oil is procured by distilling garlic with
water, and redistilling the product first obtained in a salt-water bath,
and then rectifying it with potassium. It is a colorless liquid, lighter
than water, and of an offensive odor. It has been called sulphide of alyl,
being composed of sulphur and the carbo-hydrogen, C6H5, called'ayl.
CamplIors.
650. The camphors are allied both to the essential oils and to
the resins.  There is a large number of' them, if we include the
stearoptens (627), deposited at low temperatures from the vola
tile oils; but only common or Japan camphor, and Borneo
camphor, with a few of the compounds formed from  them, will
be here described
651. Common, or Japan Camphor, Co11,602.-This substance,
which is always seen as a white crystaline solid, is obtained by
distilling with water the roots
arnd wood of the laurus campthora, a   tree found  in  the
island of Japan, and other parts
of the East (see figure).  It is:
a little lighter than water, and  $
is readily  soluble  in alcohol,
and ether, and every variety of 
ardent spirits.  Water dissolves.
about  one-thousandth  of  its
veight, which  is sufficient to
communicate  to  it something
of its  peculiar, pungent, but
agreeable odor.   At 3470 the           -
solid  melts, and  at 4100  it
boils.  In the open air, at ordi-         Laurus Camphora.
nary temperatures, it gradually evaporates.  When some lumps
of it are contained in a close glass vessel, of somewhat larger
capacity than is merely sufficient to receive it, the vapor that forms
is gradually condensed in small crystals upon the sides of the
QUEsTroNs.-649. What is the composition of oil of garlic?  650. To
vwhlat are the camphors allied?  651. From what is common camphor
procured?  Describe its properties.




4541                V~OLATILE  OILS.
glass; and if the vessel stand in a place so that the light can fall
only on one side, the chief deposition will be on the side exposed
to the light.
When subjected to the action of chlorine, a part of the hydrogen
of the camphor is replaced by chlorine, forming chlorinated camphor, C20HoC1602.
By the action of heated nitric acid upon camphor, camphoric
acid, C,20oI,608    C2oHI406,2HO, is formed, which is bibasic, and
forms with alcohol a coupled acid (609) and a compound ether.
By the action of a mixture of potassa and lime, at an elevated
temperature, upon vapor of camphor, another acid is formed, called
the campholic acid, the composition of which is C,1oH703,O1,O.
Distilling this acid with phosphoric acid, we obtain the carbohydrogen, Cls11,6 called campAolene, which is liquid, and boils
at 275~.
Borneo Camphor, C2,,,,8O,. — This compound comes chiefly
from  the island of Borneo, and hence its name.  In some of its
properties it closely resembles the preceding, but its odor and
taste are different.  It melts at 3830~, and boils at 4190.  In
composition it differs from  Japan  camphor only by containing
two more equivalents of hydrogen.  By heating it with nitric
acid, these two equivalents are separated from  it, and common
camphor formed.
(oumagvizne.
651* By this name a crystaline, odoriferous substance is known, which
is extracted from the Tonlca bean, but is also contained in several plants,
as the sweet vernal grass (anthoxantlhum  odoratumn). It is procured by
cligesting the bruised beans in strong alcohol, which dissolves the odoriferous principle.  Coumarine is the basis of the perfume called vanilla.
By the action of reagents itforms couznaric acid, ClHO76,HO.
QuESTIONS.-What effect is produced when common camphor is subjected to the action of chlorine?  How is camphoric acid formed?
W-hat is said of Borneo camphor?  652. From  what is coumarino
obtained? In what perfume is it used?




FIXED   OILS  AND  FATS.                       455
FIXED   OILS  AND  FATS.
653. The fixed oils are so called because, unlike the essential
or volatile oils, they are incapable of being volatilized without
change; consequently, when spread upon paper they produce a
permanent stain.  The fats are essentially the same as the oils,
except that they are usually solid at ordinary temperatures, while
the oils are generally liquid.  But the distinction is unimportant.
Fatty substances —a phrase which may include both the fixed
oils and fats-are found both in the animal and vegetable kingdoms; and their ultimate elements are always carbon, hydrogen,
and oxygen.
The fatty substance of a plant is usually found in the seeds or
pericarp, occasionally upon the surface of the leaves or bark.
When contained in the seed or pericarp, it exists in peculiar cells,
which require to be broken before it can be separated; and usually
heat is applied to render it more liquid, when the separation is
effected by severe pressure.  Animal fats are separated from  tile
tissues containing it either by pressure or by the protracted
action of heat.
Most oils absorb oxygen from the atmosphere, by which their consistency is changed; but by some the absorption is much more rapid
than by others.  Such as absorb oxygen rapidly —as linseed oil-are
called siccative, or dryigy oils, and are used in painting.  When mixed
with the coloring substance, or pigment, and spread upon the surface
of wood, or other material, by means of a brush, oxygen is absorbed and
a resinous coating formed, by which the coloring substance is firmly
retained.  By heating a drying oil nearly to the point at which decoliposition begins to take place, the tendency to absorb oxygen is increased.
This effect is still greater if, before heating, some highly oxydized body,
as oxide of lead or manganese, is mixed with the oil.
Unctuous oils are such as do not absorb oxygen from the air, or do it
but slowly.  Rancidity in oils is usually occasioned by the absorption
of oxygen.  Somne oils, while they absorb oxygen also give off carbonic
acid or hydrogen.
654. Proximate Principles of the Fats. —All the fats and
fixed oils are composed of several proximate principles, which
QuEsTro s.s-'-653. Why are the fixed oils so called?  Are they folund
both in animal and vegetable bodies? In what part of the plant are thliey
usually found? CWhat are siccative, or drying oils? - What are unctuous
oils?  654.  Wha.t are the chief proximate principles of the fats?




456              FIXED  OILS  AND  FATS.
are usually combined in definite proportions. The most common
of these are glycerine, stearilne, margarine, and oleine, of which
nearly all the animal fats and oils are almost wholly composed.
In several fatty substances, as butter, we find, in addition, small
quantities of other proximate principles, as buttyrine, cac2rine, and
cacproine.   In  some instances still other principles are found,
which will be described in their proper places.
The proportion of stearine, margarine, and oleine in the different fats is exceedingly variable, and occasionally one or another
of them  may be wanting; in the more solid fats stearine and margarine are more abundant, while oleine is the chief constituent
of the oils and more fusible fats.  All of them  contain glycerine
except spermaceti, in which, instead of this principle, another
peculiar compound is found, called ethal, a substance in comrn
position allied to the alcohols.
The fats and fixed oils generally are capable of combining with the
caustic alkalies to form soaps, and are therefore said to be saponifiable.
The process consists in digesting the fatty substance with a solution of a
fixed alkali, as potassa, or soda, when the stearine, margarine, oleine, &c.,
disappear, and corresponding acids, called stearic, 7maryaric, oleic, &c., acids,
are formed, which unite with the alkali, glycerine being at the same time
set free.
These acids probably do not exist as such in the fats, or even in the
proximate principles from which they are derived, but are formed during
the process of saponification, as will appear more clearly hereafter.  The
presence of water is necessary to the process, a small portion of it, as
we shall see, being required to produce the compounds formed.
Gycerine.
655.  Glycerine, CTO,6   C6,H,O HO, was  discovered  by
Scheele, and called the "sweet principle of fat."  It is best
obtained by boiling, for some time, a mixture of equal parts of
olive oil and oxide of lead diffused in water, filtering the liquid
which remains, and then passing through it a current of sulphuretted hydrogen, to separate all the lead.  Lastly, it is heated
for a few moments to the boiling point, and all the water carefully evaporated in a vacuum.
QUESTIONS. —In what fats do stearine and margarine usually abound?
In what is oleine the chief constituent?  What is said of spermaceti?
What is meant by the saponification of a fat?  What are formed in the
process of saponification?  655. How is glycerine obtained?




FIXED  OILS  AND  FATS.                       457
As thus prepared, glycerine is an oily liquid, very soluble in
water and alcohol, but insoluble in ether; quite inodorous, but
having a sweet taste.  Its specific gravity is about 1'27.   Its
name is derived from the Greek, glffckus sweet, in allusion to its
taste.
With sulphuric and phosphoric acid it forms coupled acids (607)
similar to those formed by these acids with the alcohols, which are
called respectively the sulphoglyceric and the phosphog/yceric acids.
Glycerine is not volatile, but is decomposed when heated, yielding a
peculiar, acrid volatile principle, called acroleine, C6H402. It is this substance which constitutes the acrid, irritating fumes always perceived
when any fatty substance is decomposed by heat, in such circumstances
that the product of the decomposition cannot be immediately consumed,
as in the manufacture of gas from oil.
Stearine anz7 Stearic Acild.
656. Steariqe,  H142111400,6. -  Stearine (Greek, stear, tallow)
forms the chief constituent of tallow, and is a white crystaline
solid, much resembling spermaceti.  It exists in nearly all fats,
and in many of the oils, both animal and vegetable; and is found
in greater proportion as the point of congelation of the fat or oil is
more elevated.  The best method to obtain it is to heat moderately
some mutton suet with 8 or 10 times its volume of camphene, in
which it will be dissolved; and, on cooling, the stearine will be
deposited in white pearly crystals. These are entirely insoluble
in water, and melt at 140~.
Stearine, by saponification with potash, forms stearate of potash,
and hydrated glycerine is set free; and the stearate, by subsequent decomposition  by a mineral acid, yields stearic acid,
C    6,I-H6sO,=C6Is0,5,2IHO, which is obtained as a white, crystaline solid.
Stearic acid is the substance of which " stearine" and  adamantine" candles are formed; and therefore constitutes an important article of commerce.  It melts at 1670, and solidifies at
about 1580~.
QuaSTIONus. —Describe the properties of glycerine. What is acroleine?
656. What is the derivation of the word stearine?  From what is this
substance obt.ained?  How is stearic acid formed?  Describe it. What
use is made of it?
39




4t58              F T IXED -OILS AND  FATS 
657. Stearic acid for the manufacture of candles is prepared by two
different processes.  One method is to digest the natural fat, as tallow,
with lime-water, aided by heat, by which an insoluble lime-soap is formed:
and this is then decomposed by dilute sulphuric acid, the lime of course
all being separated, as a sulphate.  The fatty acids now rising to the top
are washed to separate the glycerine, and compressed to remove the oleic
and most of the margaric acids; and the cakeu of nearly pure stearic acid
are ready for use.
By the other mode dilute sulphuric acid is used, by which nearly the
same effect is produced, this acid combining with the glycerine to form
sulphoglyceric acid (655), which is washed away with the water.  The
fatty acids now obtained are distilled, at a high temperature, in an apparatus in which a partial vacuum is kept up, and through which a current
of steam is continually passing. -By pressure most of the oleic acid is
now separated, and the mixed stearic and margaric acids obtained.
The composition of stearine corresponds to 2 equivalents of anhydlrous
stearic acid, and 1 equivalent of hydrated glycerine.  Thus,
C,421-40,16 = 2(C65s6605) + C6H705,,HO.
658. Stearic ether is formed by treating wine alcohol with stearic acid,
and passing through the solution a current of hydrochloric acid; and by
a similar process with methylic alcohol stearic vethylic ether is formed.Both are solid at temperatures below about 85~ or 900.
J]iargjare e and lfa2raric Acid.
659. Maryarze and margaric acid have the same composition, respectively,
as stearine and stearic acid, of which they are isomeric modifications. Tho
melting point of margarine is 1180, and that of margaric acid 140~.
660. Mllargarone, C6sT6602,, is a white pearly substance, formed by distilling a mixture of 4 parts of margaric acid and 1 part of lime.  Tlle
following equation illustrates the chemical changes produced in the acid
to form the margarone:
C6s8s11688 + 2CaO = C66I6 O-02{- 2CaO,CO2 + 2HO.
Oleine and Oleic Acid.
661. Oleine is the chief ingredient of most of the fixed oils,
and is found also in many of the fats.  It is difficult to obtain it
pure, and therefore its formula cannot be given with certainty.
QUESTroxs.-657. What two methods are given for preparing stearlie
acid for tlhe manufacture of candles?   658. Describe stearic etler.
6;59. What is said of the relation of margarine and margaric acid to
stearine and stealic acid respectively?   660. What is margaromle?
661. What is said of oleine?




FIXED  OILS AND -FATS.                          459
It is best prepared. from  olive oil.  Oleine is a yellowish liquid,
of an oily consistency, which requires a temperature of about zero
for congelation.
Oleic acid, CJ,,30,,HO, is an oily liquid, having a density
of about 0'808, and solidifies at about 320.  It is formed by
saponification of oleine, and subsequent decomposition of the soap
Dy hydrochloric acid.
By distillation in close vessels oleic acid forms sebacic acid, C1oH,O3,H It);
vhich, distilled with alcohol and hydrochloric acid, forms scbacic ether.
Action of Nitric Acid upon the Fatty Acids.
662. Nitric acid acts energetically upon the fatty acids, producing a variety of other acids, some of which are volatile, and
others fixed  at moderate  temperatures.   The former are the
formic, acetic, propylic or acetonic, butyric, valerianic, cct2proic.,
oenanlzthylic, caprylic, pelargonic, and caloric acids; all of which
are homologous, and have the general formula, C2,,,H,,O40
C2JT2,0_,O3,HO.
At the same time the following non-volatile acids are formed,
and may be separated by the proper means, viz., the succinic,
adliic, ic, 2en, szuberic, and sebacic.  These also are homologous,
and have the general formula, C2,l2,(,,_,)Os =  C2,,H2(,2),,O6,2tO.
Most of these acids, it will be observed, are also obtained from
other sources. The pelargonic is obtained from the rose-geranium
(pelargoniunt, roseunt), the succinic,  from  amber (Latin, succnusm), and the suberic, from  cork, which is the prepared bark
of the quercus suber.
Other Proximate Principles of the Fats, as Butyrine, Palmatine, &c.
663. Butter contains several proximate principles, besides those
above described, as buty rine,  caprine, and caproine, but it is
difficult to separate them.
By digesting butter with an alkali, decomposing the compound
formed by tartaric acid, and distilling, butyric acid, C5sHs04QuesTroNs.-Describe oleic acid.  662. What is said of the action of
nitric acid upon the fatty acids?  663. What is said of butter?  I-low is
butyric acid obtained?




460              FIXED  OILS AND  F'ATS.
Cs:,On,IO,O   is obtained, mixed  with  other substances, from
which it is easily separated.
Butyric acid may also be formed from  sugar, by mixing with a
solution of it a little curds of milk and powdered chalk, and allowing it to stand for a time in a place where it shall be kept at a
temperature of about 90~.  A peculiar fermentation takes place,
called the bct'yric fermentation, and the butyric acid, as it forms,
combines with the lime, and forms butyrate of lime, which is
decomposed by hydrochloric acid, and the butyric acid separated
by careful distillation.
IButyric acid is liquid at ordinary temperatures, and boils at
about 327~. Its density is about 0'963, and it is soluble in both
water and alcohol.
With alcohol and sulphuric acid butyric acid forms buctyric
ether, C(1-H, CsH,70,.  This substance, dissolved in 5 or 6 times
its volume of alcohol, forms pine-apple oil, which is used by confectioners for its pine-apple flavor.
B/tyolTone, C71H0, and the compound, CsTT,O,, sometimes called biy/ratl,
are formed by distilling butyrate of lime. 13utyral is the proper aidehyde (547) of butyric acid, and may be called bu1yric atdeliyde.
C'aproie, capaylic, and capric acids, are also obtained from the decomposition of butter. Each of them forms a vinic and a methylic ether.
664. Castor oil (obtained from the plant called rici!n7s commun-is)
by saponification forms ricinoleic acid, Cs-I3606 = C,3sH3505,H O;
and this acid, distilled with solution of potassa, yields the compound, C]6H110.2, which is evidently homologous with the alcohols,
and has been placed in our list (547) as caEpry7ic alcohol.
Pablnatire, and palmitic acid, C64HT5O_408C==, H60,206 0, are obtained
from palml oil, which is imported largely into this country from the coast
of Africa, and used in the manufacture of soap.
665.,ASpermaceti-ealled also cetine, when pure-is a beautiful
white substance, found mixed with oil in cavities of the heads of
certain species of whales.  The oil is separated from it by pressure; and the hard, white, crystaline substance thus obtained
QusisioNs.-lHow may butyric acid be formed from sugar?  Describe
its properties.  How is butyric ether formed?  What is butyrone? What
is said of butyric aldehyde?  664. How is caprylic alcohol procured?
665. W7ha.t is ethal? From what is it obtained?




FIXED  OILS AND  FATS.                      461
melts at about 1200, and may be sublimed unchanged, in close
vessels, at about 680~.
Spermaceti contains no glycerine; but in its place a peculiar
principle called ethal, C32H,40,, is found, which may be separated
as a colorless, crystaline solid.
Ethal in many of its properties, as has been stated, closely
resembles the alcohols; and various bodies are derived from  it
similar to those derived from  the alcohols.  Thus, when treated
with sulphuric acid, it forms a coupled acid, called the sullZ7etharc/i
acid,  which corresponds to the sulphovinic acid; and, distilled
with perchloride of phosphorus, it yields a liquid ether, C,,H,,Cl,
corresponding exactly with the hydrochloric ether, C4H,Cl, previously described.
This substance yields an acid, called the ethalic, C2H 3204 = C22Hi3,O, IIO,
corresponding to acetic acid in the common alcohol series.
66. Wax. —Many substances, mostly of vegetable origin, are
known as wax, of which bees'-wax is the proper type.  This, as
is well known, is obtained from honey-comb, by heating it with
water; the wax melts and swims upon the surface, while the
impurities it contains are dissolved in the water, or settle to the
bottom.  It appears to be a compound of two principles, cerize
and myricine, which may be separated by boiling alcohol.  Comi
mon bees'-wax is of a yellow color, but is whitened by exposing
it in thin layers to the action of the atmosphere and of light.
Ba'cyberry tallow, or myrtle wax, is a fat obtained from  the
fruit of the common bayberry (nzyrica cerifera).  It is obtained
from  the berries by steeping them in hot water, and is found in
other vegetables.  Its composition is essentially the same as common tallow, but it contains other principles in small quantity,
among which is myricine.  It melts at 117~, but is very hard.
when cold, and may be formed into candles.
667. Jl3yricine, Cs2H9204, subjected to the action of a boiling
alkaline solution, is converted into palmitic acid, C32H11204, and
QuESTIONS.-IVlWhat is said of the properties of ethal? 666. From lwhat
is bees'-wax obtained?  TWhoat two principles are mentioned as contained
in it?  From what ik myrtle wax.procured?  What use is made of' it?
667. What is melissic alcohol?




4i62              IXE)  OILS ANDL  FATS.
a compound called melissine, C60H,20,, which, being analogous in
composition to the alcohols, may be called melissic alcohol.
Treated with potassa or lime, melissic alcohol forms melissic acid,
C6oH6004 - CCoH5903,HO (547).
Cerotbie, C54H56,,2 and cerotic acid, Cs4Ts404   C54H5303, 10,
are other compounds obtained from wax.  The former substance
in composition ranks with the alcohols, and may be called ccratib'
alcohol.
Soas and Plasters.
668. Soaps.-Frequent allusion has already been made to the
action of the alkalies upon the fats and oils;-wbhen these are
boiled together, Union takes place between them, and a well-known
and very important substance is formed, called soap.  The acids
contained in the fat or oil, as the margaric, stearic, oleic, &c.,
described above, combine with the alkalies, forming proper salts,
which exist in the soap together with other substances.
The soaps formed by potassa, soda, and ammonia only are
soluble in water.  Potash soaps are generally soft, while those
made with soda are hard; but their consistency depends also
upon the nature of the fat used.  All soaps contain a large proportion of water in their composition.
Potash or soda for soap-making should be in the caustic state,
in order to act readily upon fatty substances.
Soft soaps are made entirely of potash and tallow or oil, and
often other animal matters.  For the coarser kinds, very impure
fats are used, without even separating them from the animal
tissues in which they are contained.  The common yellow hard
soaps contain a portion of common rosin.
Toilet soaps are often perfumed with the essential oils.
669. The mode in which soaps of all kinds operate to produce their cleansAng effects is easily understood.  All soaps are always more or less alkaline,
as the alkalies contained in them are not entirely neutralized by the oily
acids with which they are combined; they are therefore ever ready to
combine with more fatty or oily matter with which they may come in
contact, as that constantly given off in the insensible perspiration from
Qu,:STIONrs. —What is cerotic alcohol?  668. How are soaps formed?
What soaps are soluble in water?  What are insoluble? What are soft,
acnd what hard soaps?  609. Explain the action of soaps.




RESINOUS SUBSTANCES.                           463
the skin.  Caustic alkali always has a soapy feeling to the fingers, from
the circumstance that it attacks the cuticle, and forms with it a soapy
compound, at the same time absorbing a portion of water from  the
atmosphere.
670. Plasters.-The lead-plaster, or diachylon, used in surgery, is a kind
of metallic soap, which is made by boiling olive oil and oxide of lead
together, with a little water.  The oleic and margaric acids contained in
the oil unite with the oxide of lead, in the same manner as they conlbine
with the alkalies'(oxides of potassium  and sodium) in the formation of
soaps.. There are two kinds of diachylon, the yellow and the brown
the former of which is made with litharge, and the latter with red lead;
but their properties are essentially the same.  Both are quite hard at
ordinary temperatures, but melt with a moderate heat.
RESINOUS  SUBSTANCES.'
671. Resins are solid substances contained in many plants and
trees, usually in a state of solution in some essential oil.  When
exposed to the air the oil evaporates, and the solid resin is obtained.
By fr'iction they usually become negatively electrical.  They are
all insoluble in water, but most of them are soluble in alcohol,
ether, and the essential oils.
Mlost of them act as weak acids, and are capable of combining
with the alkalies and other metallic oxides.
Comqmon resin, or rosin (French, colophcane), is obtained from
different species of pine, in which it exists combined with oil of
turpentine.   The substance called turpentine is obtained from
the trunk of the tree by incisions made in it while growing; and
this, by distillation, yields the oil of turpentine, the resin remaining
behind in the boiler.
There are, in commerce, several different kinds of turpentine, as
TPentice turpentine, Strasboaurg turpentine, Canada balsamn, &c.
When the tree is felled, and the turpentine extracted by heat, it is
partially decomposed, and acquires a dark color, and an offensive burnt
odor, and is called tar. By heating tar, so as to expel all the oil of turl
pentine contained in it, the common pitch of commerce is obtained.
From the different turpentines, by the action of reagents, many important substances may be formed, as the pimnaric, silvic, and pinic acids.
672. Lac, or gnum lac, as it is often called, is procured from a
species of tree called Jicts, by punctures made in the bark by
QUESTIONS. —670. How is lead-plaster or diacliylon formed? 671. What
are resins?  What is common resin or rosin?  How is tas obtained?
67"2. From what is lac procured?




464             RESINOUS SUBSTANCES.
insects. It is soluble in alcohol and heated oil of turpentine, but
is quite insoluble in water.  Its composition seems to be quite
complex, there being contained in the common lac of commerce a
mixture of as many as five different resins.
Lac is much used in the preparation of varnish and the manufacture
of sealing-wax.
Co3al  is the resin of the rihus copallinurm  and eleocarlpus
copaliferus, trees found only in warm  climates.  It is of a light
yellow  color, and very hard, and without odor or taste.  Its
specific gravity is about 1'11.  It is believed to be a mixture
of several different resins, which, by proper processes, may be
reparated from each other.
This resin is quite insoluble in common alcohol or ether, but is
softened, though not dissolved, by some of the essential oils.  Its
complete solution is effected by carefully fusing it, and then treating
it with boiling alcohol or oil of turpentine.
Copal varnish is made by fusing the resin in a deep copper vessel, to
prevent it from igniting, and then pouring in hot linseed oil, and oil
of turpentine, to give the proper consistency.
MIastic and sandarac are other resins used in the preparation of
varnishes.
673. Amber (electron of the ancient Greeks, and succinum
of the Romans,) is always found as a fossil, but it appealrs to be
the resin of some ancient tree that has become extinct.  It is
found on the shores of the Baltic sea, on the Yorkshire coast
of England, and in some of the United States, as in New Jersey.
It is found in masses seldom weighing more than a few ounces,
and in small grains.  Its color is usually some shade of yellow,
often inclining to red.  It has a specific gravity of 1'07 to 1'09,
and is insoluble in water, and is acted on but slightly by alcohol,
ether, or the oils.
It is capable of being worked in the lathe, and is often seen fashioned
into ornaments of various forms.  It is used also in the prepatration
of varnishes.
674. Ccaoutchouc. -This substance, sometimes called gum elastic,
or India-rubber, is prepared from  the milky juice which exudes
QuESTIONs.-)What use is made of lac?  From what is copal procured?
What use is made of it? 673. Where is amber found? Give a description
of it. 674. From what is gum elastic obtained?




VEGETABLE ACIDS.                          465
from  certain trees, as the ficus elastica, when incisions are made
in them.  The white milky juice which exudes is received on
masses of clay, and dried by exposure to the heat and smoke
of fires kindled for the purpose.
As usually seen, caoutchouc is a solid of a dark color, and
specific gravity a little less than water.  At 320, and lower temperatures, it is very hard, and has little elasticity; but at 600 or
700, it is exceedingly flexible and elastic.  It is quite insoluble
in water, and alcohol, but dissolves slightly in pure ether and
some of the essential oils.  Chloroform  dissolves it readily, as
does also a solution of sulphur in oil of turpentine,
By distillation it yields several peculiar products.
Vulcanized India-rubber is formed by heating caoutchouc with a
portion of sulphur, which becomes incorporated with it, increases its
elasticity, and renders it less liable to be affected by changes of temperature. It is used for many important purposes.
675. Guztta.Percha is a substance, in many of its properties,
closely resembling the preceding; it is prepared in the same way
froml the milky juice of a tree found only in tropical climates.
Like India-rubber, it is quite insoluble in water and alcohol,
but is dissolved in small quantities by pure ether and some of the
essential oils, and more largely by chloroform and sulphide of
carbon.  Its specific gravity is about 0'97.
Gutta percha is less elastic than caoutchouc, and at ordinary
temperatures is quite hard, but becomes soft at 2000 to 212~,
and may be formed into any desired shape.  It is becoming of
considerable importance in the arts.
VEGETABLE ACIDS NOT INCLUDED IN THE PRECEDING  GROUPS.
676. These acids are all found ready formed in plants, a circumstance in which they differ from most of those heretofore
described.  Sometimes they occur in a free state, but generally
they are found in combination with bases.
QuEsTIONs.-Describe the properties of gum  elastic.  How is vul
canized India —rubber prepared?  675. From what is gutlta percha obtained?  Describe it.  676. What is said of the acids of this group?




466                v E G E TVEGETABLE  ACIDS.
677. Oxalic Acid, CHO, = C(40,2HO.-Oxalic acid, in com-il
bination with bases, is found in many plants, especially in certain
species of the sorrel (oxalis), and also in certain minerals. It
may likewise be prepared artificially, by digesting starch, or sugar,
with nitric acid, and by other processes.
To prepare it artificially, add, in successive portions, 24 parts
of starch to 144 of nitric acid of commerce, diluted with 10 parts
of water, and heat gently till the nitrous vapors cease.  When
the action is over, set the whole aside to crystalize.
Pure oxalic acid is a crystaline solid, in external appearance
not unlike Epsom salt, for which it has sometimes been mistaken.
It is very soluble in water, exceedingly sour to the taste, and
poisonous. Its composition in crystals is 04H208 +  2H0.
678. Salts of Oxalic Acid. —Oxalic acid is bibasic, and, as in
the case of other bibasic acids, both equivalents of its basic water
may be replaced at the same time by a fixed base, or only one
of them, producing the two series of salts of the forms 2(RO)C406
arid RO,C406,1H0;-RO  being used to indicate any base.
679. Oxalate of lime, 2CaO,C40o, is found in many plants, in the cells
of which it may often be detected in small crystals by the microscope.
The crystals when thus found, or if formed by other means, always contalin 2 equivalents of water of crystalization.  It is very insoluble.  With
potash it forms three salts, called the neutral oxalate, 2KO,C40s, the
biuoxalate, KO,C406,IIO, and the quad&roxalate, the latter containing twice
as much acid as the next preceding.  The binoxalate is often used in
solution to remove stains of iron-rust, under the name of salt of sorrel.
Oxalic acid forms with the alcohols, both coupled acids (609) and compound ethers.
680. Tartaric Acid, CSH601,2   CsIH40,0,2HO.-Tartaric acid,
in combination with potash, exists in many fruits, especially in
grapes and in pine-apples. When the expressed juice of the
grape is fermented, as in the manufacture of wine, this salt, in
an impure state, is precipitated upon the inside of the cask, as
argol, or tartar.  From  this the pure acid is obtained, which is
a white solid, very soluble in water, and of an agreeable acid
taste.
QUlEST10NO.-677. In what is oxalic acid found?  I-low may it be prepsaled artificially?  Describe its properties.  678. What is said of the:.alts of oxalic acid?  679. In what is oxalate of lime found?  680. In
what is tartaric acid found?




VEGETABLE  ACIDS.                            467
Tartaric acid is bibasic, and forms two series of salts, according
as one only or both equivalents of its basic water may be replaced
by the base.
There are only two or three important salts of this acid, among which
the acid tartrate of potash, or cream of tartar, takes the first place.  It:s
composition is KO,C8H40o0, HO.  It is prepared entirely from the impureo
tartrate, or argol, forming the settlings of wine-casks by repeated crystalizations and filterings.
By saturating a solution of cream of tartar with soda, or carbonate
of soda, a double tartrate of potash and soda is formed, called Rochelle
salt.
681. Tartar-emetic is a double tartrate of potash and oxide of antimony,
which is formed by boiling equal parts of cream of tartar and the oxide
illn 6 parts of water. It is much used in medicine.
By the action of heat upon tartaric acid its characters are changed,
and it is converted into other acids, which are generally isomeric with
itself, as the metatartaric, isotartaric, and paratartaric or racetmic acids.
With the alcohols tartaric acid also forms coupled acids and compound
ethers.
682. Citric Acid, C,2H80,4 = C12115011   3 HO.-Citric acid is
obtained chiefly from  the lemon (citron), but is found in other
fruits, as the orange, currant, gooseberry, strawberry, &c.  When
pure it forms crystals, which are very soluble in water, and have
an agreeable sour taste.  It is used in calico-printing, and for
medicinal and domestic purposes.
To prepare citric acid, lemon-juice is first saturated with lime,
and then the citrate of lime, so formed, mixed with several times
its weight of warm water, is decomposed by sulphuric acid.  The
clear liquid is then drawn off and evaporated until the crystals
of citric acid are deposited as the solution cools.
Citric acid is tribasic, and forms three series of salts, according
as one, two, or three equivalents of its basic water may be replaced
by the fixed base.
By heat this acid is decomposed, forming carbonic acid and other products, among which is aconitic acid, C4IO,,110, so called because first
obtained from  the aconitulm napelluzs.  By distillation it also yields the
itaconitic and citraconic acids.
Citric acid with alcohol forms two different coupled acids, and a compound ether.
QCrESTIONS..-What iS said of the salts of tartaric acid?  What is cream!f tr7tar?  Rochelle salt?  681. Describe tartar-emnetic.  What acids isomoreic with tartaric acid are mentioned?  682. From what is citric acid
obtainedP Describe its properties.




468                  VEGETABLE  ACIDS.
683. Malic Acid, C8H1O,o = Cs-H40,,21O. —Malic acid is found,
in many vegetables, both free and in combination with bases, especially in  many fruits before coining to maturity, as the apple
(malhum), and the plum.   It is abundant in the fruit of the
mountain ash (sorbuts aClucparia), and in the stalk of the rhubarb
or pie-plant.
Pure malic acid forms crystals which are very soluble in water,
and which melt at about 181~. With alcohol it forms a coupled
acid and an ether, in the same manner as other bibasic acids.
By the influence of heat, carefully managed, it may be converted into
two other acids, which are isomeric with each other, called the maleic,
and the parasanleic or fumaric acids.  The latter is also found in some
plants, and in Iceland moss.
684. Tannic Acid, C,0H8012 =  C,611,09,3HO. - Tannic acid
(called also tannin), occurs in the bark and leaves
of many trees, as the oak, chesnut, and hemlock,
but is especially abundant in nut-galls, which are
excrescences that form  upon the leaves of several'Y(' ": species of the oak.
Bi,             To prepare it, nut-galls, in coarse powder, are introduced into a funnel, of the form A, represented in the
figure, the mouth having been loosely filled with a little
cotton, and pouring over them some sulphuric ether that
has been previously washed.  The funnel is placed in a
vessel of the form B, into which the liquid gradually percolates, and separates spontaneously into two portions;the lower being a solution of the acid in water (a little
of which was contained in the ether), with the lighter and
Prep. ef Lanic   nearly pure ether above it.  The acid solution can be
Acid.      easily separated; and by evaporation it yields the tannic
acid as a solid mass.
This acid  is soluble in water, and has a peculiar astringent
taste.  It is a feeble acid, but forms salts with bases.  With
salts of the peroxide of iron, it forms a deep blue or black precipitate, which is the basis of writing-ink.*   It forms an insoluble
* To prepare an excellent black writing-ink, pour 6 pints of boiling rain-water upon'6 ounces of the best nut-galls in powder, and add 4 ounces of gum-Arabic, and let the
whole stand two days in a wooden or earthen vessel. Then strain the liquid and mix
with it 4 ounces of clean copperas, and let it stand one or two months, stirring it fiequently, nlmd pour off the part free from sediment for use.
QU.STIOxNs.-683. Describe umalic acid.  684. In what does tannic acid
or tanninl occur?  Describe the mode of preparing it.




ALKALOIDS.                          46$
and very important compound with gelatine, which is the basil
of leacther.  Raw hides, after the hair is removed, are soaked fol
a time in a decoction of bark which contains this substance, and
are thus cnanged into leather.
685. Gallic Acid, C,14160,   C4-,407,3HO. -- This acid is
usually associated with the preceding, and is always formed when
a solution of that acid is left for some time to the action of the
atmosphere, or is boiled for a time with sulphuric acid.  In the
latter case, the reaction is attended by the formation of grapesugar.  This acid is readily obtained in crystals, which are quite
insoluble in cold, but very soluble in hot water.
By the action of heat two other acids are formed from gallic acid,
called the pyrogallic and metagallic acids.
OR0GANIC  ALKALIES, OR  ALKALOIDS.
686. VWe have seen above, that many organic compounds are
acids; so also there are others which are properly alkalies, as
they readily, like potash, soda, &c., combine with acids which they
neutralize, forming true salts.
All the organic alkalies contain nitrogen and hydrogen, and in
some sulphur is found.  Some of them  exist ready formed in
plants, but others are produced by their destructive distillation.
Nearly all of them are poisonous.
687. Morphia, or Morphine, C,,4H,,NO. —This substance is
an essential ingredient of opibum, which is the dried juice of certain species of the poppy, cultivated largely in different parts of
Asia.  To separate the morphia, the opium  is digested several
days in water, and the solution precipitated by ammonia, which
is added cautiously in small portions.  The impure morphia thus
obtained is then further purified by dissolving it in boiling alcohol, from which it crystalizes on cooling.
The morphia in opium seems to be in combination with a peculiar acid called mzecoinic acid (from mecone, a poppy).
QUESTIONs. — What is leather?  685. Describe gallic acid. 686. What
are the organic alkalies? What is said of their composition? 687. From
what is morphia obtained? Describe the method of separating it.
40




470                      ALKALOIDS.
Pure morphia is a crystaline solid, but slightly soluble in water,
and of a bitter taste. It combines readily with acids, forming salts,
the most important of which are the sulphtate, acetate, and hcydrochlorate.
These salts are the compounds of this substance, generally used in
medical practice under the name of nzorphine, and not the pure alkaloid,
which is but slightly soluble in water, and therefore inert.
Narcotine and codeine are other compounds, of a similar character,
procured from opium.
688. Quinia, or Quinine, C,8H,,4N,O,.-Quinia is obtained only
from the bark of certain species of' a tree called cinchona, which
grows chiefly in South America. In commerce it is called Peruvian bark, and is extensively used in medicine.
To prepare quinia, the bark, in powder, is digested in water,
and from the solution obtained, the alkali is precipitated either by
lime or ammonia. The quinia may then be dissolved in alcohol,
and crystalized.
Quinia is a crystaline solid, slightly soluble in water, and
intensely bitter.  It combines readily with acids, as the sulphuric
and hydrochloric; and the salts formed are extensively used in
medicine, especially in certain fevers.  With the sulphuric acid
it forms two salts, a neutral and an acid sulphate.
689. Cinchonia, or Cinchonine, C,,,H4NO22.-Cinchonia always
accompanies quinia in Peruvian bark, and is obtained from it by
a similar process.  It differs in composition from quinia, in containing 2 atoms less of oxygen; but in most properties, the two
substances are much alike.  Alone, it is but slightly soluble in
water, but the salts it forms with acids dissolve more readily, and
are used in medicine..
Quinia and cinchonia exist together in the bark, the former
being most abundant in that which is of a pale color, while the
latter (cinchonia) occurs chiefly in the red bark.
QuEsTIoNs.-What are some of the properties of morphine?  What
other alkaloicls are procured from opium?  688. From what is qui:nia
prepared?  Describe the mode of separal:ing it from the bark?  689. In
what does cinchonia differ from quinia?  What is said of -the color of tih
bark containing these alkaloids?




ALKALOIDS OF THE  ETHERS.                         471
690. Stsrchnia, or strychnine, C,42,,,N204, is a vegetable alkali
obtained from nux vomica, and other plants.  It is the poisonous
principle of the famous UpCas, of the island of Java, of which so
many fables are told.  It forms an extensive series of salts with
the acids, and is one of the most violent poisons known.
ZBrucia, or 6bucine, is a similar alkaline substance, obtained
from the same source.
691. Isatine, C161NO04, is derived from indigo by heating it with dilute
nitric acid.  It is a crystaline solid, of an orange-red color, soluble in
lhot water and in alcohol.  From this substance isatinic acid is derived,
and several other compounds.
Theine, and Caffeine, obtained from tea and coffee, appear to be the
same substance.  It is found also in the fruit of some other plants, and
is contained in larger quantity in tea than in coffee.  It is not certain
that these articles, so extensively used among civilized nations, owe their
peculiar properties to this principle.
Nicotine is an alkaloid obtained chiefly from the tobacco-leaf.  Piperins
is extracted from black pepper;-it is a crystaline solid, and acts as a
f'eeble base.
Picrotoxine, from the coculus Indicus, cantharadine, from cantharides,
asparagine, from the roots of asparagus and other plants, and phloridzine,
from the fresh bark of the apple, pear, plum, and cherry trees, are compounds of a similar character.
ALKALOIDS  OF  THE  ETHERS    OR  CONJIUGATED
AM MONIAS.
692. The alkaloids of the ethers, like the ethers themselves,
and the alcohols, are not found in nature, but are produced only
by artificial means.  They closely resemble ammonia in most of
their properties, and indeed may be considered as ammonia in
which one or more atoms of hydrogen has been replaced by
equivalent quantities of the compound radicals, ethyle, C44H5,
methyle, C2H,, acetyle, CH,, &c.  A  few  of these only can be
described; and in doing so we shall find it advantageous occasionally to represent ethyle, C4H5, by Et; methyle, C2I3,, by
Me; amyle, C,lH,,, by Ayl; acetyle, C,4H3, by Ae, &c.
QUESTIONS. —690. What is said of strychnia? From what is it procured? What other alkaloid accompanies it?  691. From what is isatine
obtained?  What is said of theine and caffeine?  What other alkaloids
are mentioned?  692. Are the alkaloids of the ethers found in nature?
What do they resemble? From what may they be considered as formed?




472         ALKALOIDS OF THIE ET HERS.
693. Ethylamine, C4UN = NH1C41H = NH,2Et. —Ethylamine
is formed by various processes, as by the action of strong aqua
amnmonie upon hydrobromic ether (bromide of ethyle), and then
distilling from  potash or lime.  The ammonia and ether are put
together into a glass tube, which is sealed hermetically, and immersed fifteen minutes in boiling water;-the reactions are as
follows, viz.:
C4H5Br + NIt3 — = C4H7,NH-Br - NHT3),C 45,Br.
If, as intimated above, we consider ethylamine a conjugated
ammonia, that is, ammonia in which 1 atom of hydrogen is
replaced by ethyle, then it is evident the compound, N-H3C4-5NI3,Et, is ammonium in which 1 atom of hydrogen is replaced
by ethyle.  It is called ethylammoniurn.  The compound, NH,,
C4115,Br, may therefore be called bromide of ethylarnmmonium;
and this when distilled with lime or an alkali yields ethylamine,
precisely as sal-ammoniac, NH4Cl, distilled with lime, yields
ammonia (224).
Ethylamine is a colorless, limpid liquid, having a density of
about 0.696, and boiling at about 68~.  It has a pungent odor
like ammonia, and alkaline reaction, forming salts with acids.
With hydrochloric acid it forms dense white fumes, in the same
manner as ammonia.
694. By the proper modes, 2, 3, and even 4 atoms of hydrogen in ammonia
and ammonium may be replaced, producing the compounds, biethylwanine,
NH( C4H )2=NIiEt2, triethylanmine, N(C4HI5)3=N NEt, and tetrefl/ylc7aine,
N(C4H5)4 = NEt4.  The latter, called also tetrethylammlonium, like its
prototype, ammonium, can only be obtained in combination, as an iodide,
bromide, or chloride.
695. Methylamine, C,2HN  N-NE2C2-I,= Ni25e.-This compound is prepared in the same manner as ethylamine, simply
substituting in the process a methylic ether.  It is a colorless
gas, having a strong ammoniacal odor, and alkaline reaction.  1Py
a cold a little below zero, it is condensed to a limpid, mobile
liquid.  In the gaseous state, it is more soluble in water than
QUESTIONS.. —693. What is the composition of ethylamine?  What is
etbhlanimonium? Describe the properties of ethylamine.  694. WhYat is
biethylamine? Triethylamine? Tetrethylaminc?  695. -low is methyl
mine formed?  In what does it differ from ethylamine?




ALKALOIDS OF THE  ETHERS.                        473
any other known gas, water at 70~ taking up 1000 times its own
volume of the gas.
696. Binzethylanmine, NH(C2,), = NHSe2, trimethylamnie, N(C02T3)3=
NMAle,, and tetramelthylanine, N(C2H,)4= NMe4, sustain the same relations
in the methylic compounds, as those of corresponding name, above described, in the ethyle series.
697. Amylamine, CoH3N = NH2C,0H,,- N-H2Ayl. -  Amylamine is prepared by a process altogether similar to those above
given for preparing the corresponding compounds in the ethyle
and methyle series.  It is a limpid liquid, which boils at a little
-above 200~, and has a density of 0'750.  It has the odor of ammonia, and is strongly basic, forming salts with the acids.
Bianrylamine, &c., corresponding to ethyle and methyle compounds,
above described, are known.
698. Aniline, C,,H,N = NTH,C,2H5, is obtained from  phenol,
ard also by the action of nitric acid upon indigo.  It is an oily
liquid, having a density of 1'028, and is distinctly alkaline,
forming salts with the acids.  It may be considered as ammonia
in which 1 equivalent of the hydrogen is replaced by the group
C,2H,, called phenyle.  The alkaloid might therefore be named
phenalctnine.
699. We may even have compounds answering to ammonia in
which the three atoms of hydrogen have been replaced successively
by different groups, or compound radicals, as in etlzylmet-hyThenyZlagaine, NC2H, C4H, C12H115 -- N,.M eEt,Pyl.
700. In all these compounds, it plainly appears that the groups, or
compound radicals, ethyle, C4H5, methyle, C~2H,'  &c., are equivalent to
It, and replace it, in ammonia, NH3, and ammonium, NH4. Now, phosphorus, P, is equivalent in combination to N; and without experiment
we might expect P to replace N in ammonia, as it does in the compound
called phosphuretted hydrogen, PH3.  So a series of compounds has
been discovered, answering to ammonia, with its hydrogen replaced by
the groups, ethyle, methyle, &c., and the nitrogen by phosphorus. Thus
we have the compounds, P(C2H3)3=PMe3, P(C4H5)3=PEt3, &c.
QUESTIONS.-G90. What is bimethylamine? 697. Describe amylamine.
6(98. Describe aniline. Why may we name it phenylamine? 699. What
i, the composition of othylmethylphenylamine?  700. Mlay the nitrogen
ill these compounds be replaced by phosphorus?
40.




474          ALKALOIDS  OF THIE ETHERS.
701. The nitrogen in these compounds may even be replaced
by a metal, as antimony, bismuth, or tin, as in the following
examples.
Stibethyle, Sb, C,2H, —Sb(C,H,),= SbEt3. —Stibethyle is prepared by the action of hydriodic or hydrobromic ether upon antimonide of potassium; and afterwards distilling carefully in an
atmosphere of carbonic acid.  It is a transparent, colorless liquid
which boils at 317~, and has a density of' 1'33.  A drop of it
exposed in the open air, first emits dense, white fumes, and then
takes fire spontaneously. Stibethyle combines readily with oxygen,
sulphur, chlorine, and other elements, forming both binary compounds and proper salts.
702. Stibncthyle, Sb(C2H3)3 =  SbMe,, is a corresponding
compound, containing  antimony and methyle; as is also bismethyle, Bi((C,4,),   BiEt,, of bismuth  and  ethyle.   These
latter, and many others pf' similar character, though formed on
the type of ammonia, have less the characters of ammonia, and
react with chemical agents more like simple metals.  They are
therefore sometimes called conjugate metals.
All the preceding compounds have the same molecular type as ammonia
and ammonium; and it is worthy of notice that those having the type
of ammoniumn, like ammoniumn itself, have been obtained only in combination.
703. There are other compounds similar in their general characters to
the above, but the molecular type of ammonia does not appear in them.
Of this character are such compounds as the following, viz., bisethyie,
B3i,4Hs5  Bi,Et; zincethyle, Zn,C45- Zn,Et; stannetlhyle, Sn,C 4H5Sn,Et; hydrargeth/yle,  Ig2C4Hs, &c. Each of these (and many others)
combine with oxygen, sulphur, chlorine, &c., forming binary compounds;
and these again uniting with other compounds form salts.
704. Cacodyle, As,C4H16= As,lie,. -  This substance (named
from  the Greek, ]cakos, evil, and ule, principle,) serves as the
basis of a long series of compounds, in which it performs the part
of a quasi-metal.  By distilling a mixture of equal parts of acetate
of potash and arsenious acid, we obtain a liquid substance long
QUESTIONS.-701. May the nitrogen be replaced by certain metals?
What is the composition of stibethyle? Describe its properties.  702. Dce
scribe stibmethyle. 704. From what does cacodyle receive its names




ORGANIC COLORING-MIATTERS.                           475
klnown as Cadet's fuming liquid.  Its composition is As,MIeO,
which corresponds to oxide of cacodyle, but it is more frequently
called alcarsine.  When pure it is a colorless liquid, which is
higihly corrosive and poisonous.
According to Regnault, gaseous alcarsine has a density of 7'8; by calculation we make it 7.824.  Its equivalent, as given above, represents
2 volumes, and its density is calculated as follows:
4 vols. carbon vapor weigh    (.836 X  4)    3-344
12  "  hydrogen        "       ('069 X 12)      *828
1  "  arsenic vapor  "                      10.370
1  "  oxygen          "                       1.106
Thus giving for 2 vols. alcarsine vapor,      15'648
The weight of 1 vol., or its density, therefore is 7-824
705. Alcarsine, by digestion in hydrochloric acid, is converted
itnto chloride of cacadyle, AsMe2,Cl, which is decomposed by a
mlctal, as iron or zinc, and yields cacodyle, As,CU6, which is a
colorless, transparent liquid, having a density a little above that
of water, and boiling at about 338~.  In the open air it takes
fire spontaneously; and even when covered by a film of water it
gradually absorbs oxygen from  the air, being converted first into
aicarsine, As,Me20,   and then into alcactgen, or cacodylic acid,
As Me2,O.
Cacodyle forms important binary compounds with oxygen, chlorine,
sulphur, &c.; aand from these many interesting salts are derived, not
here described.
ORGANIC COLORING-MATTERS.
708. Color is a property which pertains to every substance; but
it is proposed to treat here of certain compounds noted for their
color, and the practical uses made of them in the art of coloring.
Infinite variety exists in the colors of organic substances; but
QuIJsTrors.-IIow is Cadet's fuming liquid obtained?  What is it com-.oosld of?  What is it soletimes called?  What is the density of alcarsine
aplspor?  705. What is formed when alcarsine is digested in hydrochloric
ac?  TIHow is cacoclle obtained from its chloride?  Describe cacodyle.
What is said of the compounds of cacodyle?  706. What are to be treated
of under the head of or ganic coloring-matters? What is said of the great
variety of colors presented in nature?




476         ORGANIC  COLORING-MATTERS.
the prevailing tints are red, yellow, blue, and green, or mixtures
of these colors.
707. The art of dyeifng consists in attaching the different coloring —matters to the fabrics to be colored.  This is accomplished in
various modes, as by adding some substance that forms an insoluble compound with the coloring-matter, or one that has the
property of causing the coloring-matter to attach itself permanently to the fibre of the cloth.  A substance used for this last
purpose is called a mordant.
As a general rule, substances of an animal origin, as wool and silk, are
more easily colored than those composed of vegetable matter, as cotton
or -flax.
Many coloring-matters combine readily with certain of the metallic
oxides, as those of aluminum, tin, &c., forming insoluble compounds,
called lac'es, which are much used for painting in oils.
Nearly all colors are injuriously affected by the action of light; or, in
popular language, are said to fade.  This, it is believed, is generally
occasioned by the absorption of oxygen, which causes a decomposition
of the coloring substance.
708. indigo, C,6H5NO. —This is a beautiful blue coloringsubstance, extracted by a kind of fermenting process, from  the
leaves of several different American and Asiatic plants, as the'is.ltiS tinctorfiao, 2potgontum tfinctoiriunn, gymnemna ti'gens, &c.
The leaves of the plant are digested for eight or ten days in
water, during which a yellow coloring-matter appears, and is held
in solution by the water.  This is then drawn off, and, by standing, absorbs oxygen from the air, and gradually becomes blue, and
is deposited as a thick sediment.  This is collected, and pressed
in the form of square blocks, and constitutes the indigo of
commerce.
Indigo of commerce is far from  being pure;-it is a mixture
of indigo with other matters.   Pure indigo-sometimes called,ilg(o)tifnee-may be obtained from it by sublimation with a gentle
heat, and by other means.
Pure indigo is an insipid, inodorous substance, insoluble in
water, but soluble in small quantity in alcohol.  In strong sulQUESTro Nos.-707. In what does the art of dyeing consist?  Wha.t is a
mnordant?  What are laces?  What occasions the fading of colors?
708. From what is indigo obtainedl?  Describe the process of preparing
it.  Whiat is said of the action of sulphuric acid upon indigo?




ORGANIC  COLORING-MATTERS.                       477
phuric acid it dissolves readily, with the formation of several new
coupled acids, as the sulphidigotic, szuphindylic, &c.  Alkalies
act readily upon it, producing many important compounds, some
of which have been described,
Deoxydizing bodies, as protosulphate of iron, protochloride of
tin, &c., have the effect to destroy entirely the color of the above
indigo-called often indigo blute-and produce another compound,
called indigo vwhite.  This unites readily with bases, and forms
several soluble compounds which serve admirably for coloring.
The solutions, though yellowish at first, gradually become blue by
exposure to the air; and articles impregnated with the solution
undergo the same change.
Solution of indigo in sulphuric acid is much used for coloring
the Saxon blue.
709. Litmtus, arch7il, or turnsol, is a coloring substance resembling indigo, obtained from  several species of lichen, as the
leconora parella, and the rocella tinctoria.  It is seen in small
cubical masses, which are partially soluble in water, and the
solution communicates a beautiful blue to substances immersed
in it. This substance is much used in chemical investigations for
detecting the presence of acids and bases; the former of which
change its blue color to red, and the latter again restore the blue.
It is a compound of several principles, as lecanorine, orcine,
rocelinine,  &c.
710. 3Madder is a red coloring-substance, obtained from  the
roots of a plant called rubia tinctoria.  It contains several principles, the most important of which is a red crystaline compound
which has received the name alizarine, C30HO8.  Some of the
other principles obtained from  it are madder purple, or pur-'
purile, C2s8Ho0015, madder red, C28,,,O,, and xanthine.
By means of different mordants, madder is made to produce
various shades of red, pLrple, brown, and orange.  The beautiful
crimson, called Turkey-red, is produced by it by means of a corn.
plicated process which has not been fully explained.
QusT IroNs.-Wh att is the effect of deoxydizing bodies upon in ligo?
70()1 From what is litmus procured? What use is made of it? 710. From
wh1at is madder.1rocurecd?




478                         AMIDES.
711. Cochineal. —This is a dried insect, which  was named
coctus cacti by Linnuus.  It is a native of Mexico, and feeds
upon a species of the cactus.
As seen in commerce, it is of a dark brown, inclining to red,
but when macerated in water, it yields a very beautiful red coloring-matter, which is much used in dyeing. The beautiful red
pigment called carmine is prepared from cochineal by boiling in
clean water, and adding a little alum;-as the solution cools, the
carmine is precipitated, and is collected and dried.
712. Brezeline is a crystaline solid, of an orange color, obtained from
Brazil-wood, which is soluble in water and alcohol.  With mordants, it
gives a beautiful red.  The same substance is contained in the African
wood called cam-wood.
Hfematoxyline, Cl6H708. —This coloring-matter is procured from  the
wood of the tree called hcenzotoxylon Campeachianuml, and frequently, inll
commerce, log-wood.  It is separated front the wood by digestion inl
water, and may be obtained in crystals.  This substance, with salts
of iron, gives a permanent black, and with other mordants, different
shades of purple or red.
713. Quercitrine, C,611Hs09,HO, is a yellow coloring-matter, contained in
the bark of the quercus tinctloia, and probably in other vegetable substances used in coloring yellow.  A fine yellow is also produced by the
tiramericroot, and by the root of the common barberry (berberis vulgaris).
Chllorophyle.-This name has been applied to the green coloring-mnatter
of the leaves of plants.  It is contained only in those parts of plants
which are exposed to the light, and this agent may therefore be supposed
to have an important influence in its formation.  It is a substance of a
waxy nature, and is soluble in alcohol, but not in water.
The above are the most important coloring-substances obtained from
vegetable bodies; by their combination with each other, and by the use
of different mordants, in different modes, all the endless variety of tints
are produced.
THE AMIDES AND NITRILES.
714. Amides. —An amide is a nitrogenized compound answering
to a salt of ammonia less one (or more) atoms of water (or its elements). Thus, oxamide (731), C,02,NH2=C,03,HO,NH3I-2O0;
-that is, it answers to oxalate of ammonia less 2 atoms of water.
So benzamide, CO,4HN02 = C141502,NH2 = C4UH50,,HONH3QUsrSTION.-711. What is cochineal?  712. From what is brezelino
obtat:ined?  What is hematoxyline?  713. What is quercitrilne?  Describe chlorophyle. 714. Describe an amide.




AMID ES.                           479
2HO;-that is, it answers to benzoate of ammonia less an atom
of water, or, less 2 atoms of water) if we have regard to the basi.c
water of the salt.
It is also characteristic of the amides, that they are capable of
resuming the water lost so as to regenerate the ammoniacal salt;
or if a fixed alkali is used, a salt of this alkali is formed, and
ammonia set free.   Thus, when benzamide is treated  with a
boiling solution of potassa, benzoate of potassa is formed, and
ammonia, being gaseous, escapes.
715. The amides are formed by several different modes, as by
the simple distillation of a salt of ammonia, by the action of aqua
ammonise upon the compound ethers, by the action of ammonia
upon certain chlorides, &c.  Oxamide, for instance, is formed by
the distillation of oxalate of ammonia, but it may also be prepared by the action of aqua ammonise upon oxalic ether (616),
alcohol being also at the same time reproduced from the ether.
Thus,
04H1502C203 + NH3 =  C4H1602 + C202,NII,.
Benzamide is usually prepared by the process last mentioned
from the chloride of benzyle. Thus,
C14H5C102 +- 2NH3 =  C14H1502, + NH4CI.
It is solid, and capable of being crystalized — at a temperature
of about 240~ it melts, and at a still higher temperature may be
sublimed.
Oxamide also, mentioned above, is solid, and without odor or
taste.  At a high temperature it may be sublimed, but some of it
-will be decomposed.
716. illalamide, C8118N,06-  CsH406,2NHT2, is the amide of malic acid
(683), and is identical in composition with aspacagine, a substance found
in the young shoots of asparagus, in liquorice root, and the root of marshmallow, and in several other plants. It may be obtained in crystals,
which require about 60 times their weight of water for solution. By the
action of acidcL, it is converted into ammonia and aspartic acid, C8H7NOq -
QanF.STIONS.-How may the ammoniacal salt be regeineratecl? 715. 1lWhanl
are some of the modes by which the amides are formed?  Describe thf
mode of preparing benzamide.  716. What is malamide, or aspfaragine?




480             N ITRILE S.-CYANOGE N.
CsHN06,2HO.  This acid is also to be considered as an amide, formed
from the acid malate of ammonia by the loss of an atom of water. Thus,
CST40, HO, NE 3-H-IO   C8H50,,NH2 - CsHIINO, 2HO.
The above examples are given as illustrative of the mode in which
bodies of this class are formed, and of their relation to the ammuoniacal
salts; many are known that cannot be here mentioned. AIost of them
are neutral in their reactions, but they may be acids-as aspartic acidor bases. Those that are acid, are usually formed from acid salts of
ammonia.
717. Nitriles.-Many of the amides are capable of parting with
still another atom of water, being then converted into compounds
called nitrites.  There are not many known; and they are not
important.
Acetonitrile, C4,HN, is formed from  acetamide, C4430,,NH2,
by distilling the latter with anhydrous phosphoric acid, which
causes it to part with 2 atoms of water.  Thus,
C4H1302,NH2 -  2HO -  C413N.
Butyronitrile, C8H7N, is an oily liquid, which boils at about 2450. It
is prepared by distilling butyrate of ammonia, or butyramide, with
anhydrous phosphoric acid, which separates an atom of water.  lalero-,nitrile, Cltfg1N, is obtained in a similar manner from valeramide.
CYANOGEN7 AND ITS COSMPOUNDS.
ymbol, C,2N, or Cy; Equivalent (12 + 14 =)26; Density, 1'82.
718. IHistory.-Cyanogen has already been mentioned (315).
It was discovered by Gay Lussac, in  1814, and in 1817 was
recognized by Berzelius as a compound radical (536). In many
of its properties it resembles chlorine, bromine, and iodine, combining like these with other simple substances, and forming
compounds called cyanides.
Like the elements above mentioned, also, it combines with
oxygen, forming oxacids, and with hydrogen forming a hydracid;
QUESTIONS.o-Describe the mode of preparing aspartic acid. Are there
acid and basic as well as neutral amides?  717. How are the nitriles
formed?  718. When was cyanogen discovered?




CYANOGEN.                            481
and  in many other respects, it reacts precisely as a simple
substance.
719. Preparation. -Cyanogen may be prepared by several
modes.  Its elements do not combine directly, but a cyanide is
first formed, and this being decomposed yields the pure cyanogen.
The best method to procure a small quantity, is to heat gently in
a small retort cyanide of mercury, and collect the cyanogen over
mercury.  At the same time a brown mass will be formed, and
remain in the retort, which has received the name of paracyalnogen.   It is isomeric with cyanogen.
720. Properties.-Cyanogen  is a colorless gas, of a density
1'82, and has a peculiar, but not disagreeable odor, resembling
that of wild-cherry water. By a temperature of -4~, or by a
pressure of 4 atmospheres, at the ordinary summer temperature,
it is converted into a liquid.
The following method serves well to prepare a small quantity in the
liquid form.  Introduce into a strong glass tube, bent as in the figure,
a little cyanide of mercury, and
seal it hermetically.  It is then
to be held horizontally, and the
heat of a lamp applied at the extremity, a, containing the cyanide      Preparation of Cyanogen.
of silver. The other extremity, b,
is to be kept cool; and in a short time the liquid cyanogen will be seen
to collect in it.
In the liquid form, cyanogen is colorless and limpid, and has a density
of about 0'9. By long keeping, it undergoes a change, forming paracyanogen.
Comnpounds of Cyanogen and Oxygen.
721. Cyanogen and oxygen form no less than three isomoric
compounds, all of which are acids.
722. Cyanic Acid, CyO,HO. -  Cyanic acid is always formed
when an alkaline cyanide, as cyanide of potassium, is exposed to
QUESTIONS.-What simple substances does cyanogen resemble in many
of its properties?  719. How is cyanogen prepared?  D)escribe paracyanogen.  720. What are the properties of cyanogen?  May it be
obtained as a liquid?   May it be preserved in the liquid form?
721. How many compounds of cyanogen and oxygen are known?
722. Describe cyanic acid.
41




4S2        COMPOUNDS OF CYANOGEN  AND OXYGEN.
the air at a red heat; oxygen is absorbed, and the acid, as it is
formed, combines with the alkali.  But it is best prepared by
heating gently cyanuric acid, a compound to be hereafter described.
It is a clear transparent liquid, with a penetrating odor not
unlike that of acetic acid, and is very corrosive to the flesh.
Cyanzates.-Cyanate of potash is prepared by heating the yellow prussiate of potash (soon to be described) with peroxide of manganese, and
digesting the mass in alcohol.  It is a white crystaline solid.  C6yanate
of anzmmonia, which is isomeric with urea, is formed by bringing together
hydrocyanic acid gas and ammonia, and by the action of cyanate of potash upon sulphate of ammonia.  It is also contained in the urine of
animals, and is therefore called urea.
723. Cyanic Ether, C4H1O,CyO.-Cyanic ether is formed by distilling
a mixture of cyanate of potassa, and the sulphovinate (607) of the same
base. It is a liquid less dense than water, and has a pungent, irritating
odor.  Dissolved in ammonia, it forms a crystaline compound, C6Hs1N202,
which has been called ammoniacal cyanic ether.  When this substance is
treated with water, carbonic acid is given off, and a new  substance
formed, called cyaimethene, having the composition, C10H12N202.
Treated with solution of caustic potash, cyanic ether forms 2 equivalents of carbonate of potash,:and is transformed into a new compound,
called ethylamine, C4T7N N= I-2,C4H.,, which in its properties closely
resembles the vegetable alkaloids (6938).
724. Fulminic Acid, 2CyO,210O.-Fulminic acid has not as
yet been obtained in a separate state, nor even in combination;With water.  It is formed by pouring alcohol into a strongly acid
solution of nitrate of mercury or silver, and applying a little heat,
if necessary, so as to produce brisk ebullition.  The acid, as it
forms, combines with  the oxide of the  metal used, and the
metallic salt formed is at once precipitated.   By digesting  a
solution of the metallic fulminate with another base, as potassa,
the fulminate is decomposed, and the acid transferred to the
new base.
This acid receives its name from the tendency of its salts to explode
violently by heat or friction, or other causes.
Fulminic acid is bibasic, and, like other acids of this character, forms
two series of salts, the neutral, which contains 2 equivalents of fixed
base to each equivalent of the acid, and the acid salts which, for ea-h
equivalent of acid, contain 1 equivalent of fixed base and 1 equivaileLn
of water.
QUESTIroNS. -What is area?  723. How  is cyanic ether formed?
7241. Has fuhlninic acid been obtained in a separate state?




COMPOUNDS OF CYANOGEN AND OXYGEN.                 483
725. Thle Fulminates.-There are several fulminates known,
but those of mercury and silver are the most important.  The
former, f2ulmirnate of mercury, is prepared by dissolving 200
grains of mercury in an ounce of strong nitric acid by the aid
of heat, and, when cold, pouring into it 4 or 6 ounces of alcohol.
The mixture should be contained in a large glass or earthen vessel,
and a little heat applied, if the action does not commence in a few
minutes after adding the alcohol. When the action has once
commenced, it goes on violently, without the further aid of heat,
attended by the evolution of white fumes, consisting of aldehyde,
acetic, formic, and nitrous acids, and their corresponding vinie
ethers, and the deposition of the solid fulminate in small crystals.
The powder thus formed should be immediately well washed and dried,
and may then be preserved for any length of time, if kept in the dark,
but is acted upon slightly by light.
Fulminate of mercury is a brown crystaline powder, without odor, but
hlaving a styptic, metallic taste. By slight friction with any hard substlnce, or by a blow, or by the contact of the minutest quantity of nitric
or sulphuric acid, it explodes with great violence;-even when moist, it
will often explode with a slight blow, and should therefore never be
touched with anything harder than wood or paper.
726. Fulminate of mercury is much used for filling percussion caps, for
exploding fire-arms; and for this purpose it is mixed with a little less
than half its weight of nitre, and some solution of resin in alcohol, to
cause it to adhere to the capsule, and to prevent the action of the air.
727. Fulmriinate of Silver is prepared very nearly in the same
manner as the above.  A dime is to be dissolved in about 2 ounces
of common nitric acid, and the solution diluted with 2 ounces
of distilled water, and then 2 ounces of alcohol added, and the
whole mixed well by shaking.  By application of heat, rapid
ebullition will soon commence, when the heat should be removed,
and the fulminate will be gradually deposited, and should be
immediately washed and dried.  It is a beautiful white solid, and
should be handled with the utmost care, as it explodes most
violently, even when damp, by the slightest friction, or by the
mere contact of sulphuric acid.
QUESTIONs.-725. Describe the mode of preparing fulminate of mer
cuvy. Describe its properties. 726. What use is made of it? 727. How
iv fulminate of silver prepared?  What is its character?




484       COMPOUNDS OF CYANOGEN AND HYDROGEN.
It is very improperly made the basis of a small toy called a torpedo,
which consists of a little of the salt mixed with some gravel, and done up
in paper.  It explodes merely by being thrown upon a hard substance.
Fulminates of copper and zinc may be prepared by digesting the fulminates of mercury or silver with these metals.
728. Cqyanuric Acid, 3CyO,3HO.-Cyanuric acid is a white crystaline
solid, with little taste or odor, and may be sublimed; but a part of it is
by the operation converted into cyanic acid. It is best formed by beating
urea, and digesting the mass in strong sulphuric acid, adding a few drops
of nitric acid until the solution becomes clear.  To the whole then add ai
equal volume of water, and as it cools the acid will be deposited in smal
crystals.
It is a tribasic acid, as the above formula indicates, and, like other
tribasic acids, forms with bases three series of salts.
Cyanidide is an isomeric modification of this acid.
729. Cyanuric Ether, 3C41TT0,3CyO, is prepared by distilling carefully
a mixture of the cyanurate and suiphovinate of potassa.  It is solid at
ordinary temperatures, but melts at about 185~0, and boils at 529~.
Boiled for some time with an alcoholic solution of potash it is decomposed, yielding alcohol, ammonia, and carbonic acid, according to the
following equation:
3C4I-5O38CyO    + 12110 = 3(J411H02 + 3NTIs+ 6SCO,
Compound of Cyanoyen and Hydlrogen.
730. Cyanogen and hydrogen form one compound only; which,
however, is exceedingly important.
Itydrocyanic Acid (Prussic Acid),  ~2N,, or HICy.-Hydrocyanic acid is prepared by various processes, one of which is to
decompose cyanide of
mercury  by  concentrated    hydrochloric
_    acid, by the  aid  of
heat. The mixed gases
__-'~~                       __.....are passed through a
___________________              etube  containing  first
pieces of carbonate of
Preparation of Ilydrocyanic Acidp
lime, to separate any
free hydrochloric acid, and then fused chloride of calcium  to
absorb all the moisture; and the hydrocyanic acid, mixed now
QUESTIONS. —728. Describe cyanuric acid.  729. Describe cyanurlo
ether. T730, HIow is hydrocyanic acid prepared?




SULPHOC YANATES.                           485
with only carbonic acid, is condensed in a bent tube, surrounded
by a freezing mixture, the carbonic acid escaping into the air.
Pure hydrocyanic acid is a limpid, colorless liquid, of a strong
odor, similar to that of peach-blossoms.  Its specific gravity is
about 0'70.  Its point of ebullition is 80~, and at 50 it congeals.
When a drop of it is placed on a piece of glass, a part of it becomes
solid, because the cold produced by the evaporation of a portion
is so great as to freeze the remainder.  It unites with water and
alcohol in every proportion.
Hydrocyanic acid is a powerful poison, producing, in poisonous
doses, insensibility and convulsions, which are speedily followed
by death.  A  single drop of it placed on the tongue of a dog
causes death in the course of a very few seconds; and small
animnals, when confined in its vapor, are rapidly destroyed.
The pure acid decomposes spontaneously when long kept, especially
if exposed to the light; but if largely diluted with water it may be preserved, and is in this state used in medicine.  It is contained in water
distilled from the blossoms and leaves of the peach and other allied
fruit trees.
Sulphocycsnates or Stlj7lhociyanicdes.
731. The sulphocyaanates or sulphocyaxnides constitute a class
of compounds corresponding to the cyanates with the oxygen
replaced by  sulphur.   Thus the  composition  of cyanate of
potassa is KO,CyO, while that of the sulphocyanate is KCyS2 =
KS,CyS.
732. Sulphocyanate of Potassium, K,CyS2 = KS,CyS.-This is properly
a sulphur salt. It is obtained by making a mixture of 46 parts of ferrocyanide of potassium, 17 parts of pearlash, and 16 of sulphur, and melting
them together; and when the whole has cooled, dissolving out the sulphocyanate by boiling alcohol.
It is a solid, and crystalizes in long prisms, which are without color,
and deliquesce in the open air. It is used as a delicate test of iron.
733. Sulphocyanic Acid, HCyS2=-  HS,CyS. —This acid, called also
]hydrosulphocyanic acid, is prepared by distilling sulphocyanate of potassa
with phosphoric acid. It is a colorless liquid, of a sour taste, and forms
with peroxide of iron salts of a deep red color.
QUESTIONxS.-What tare the properties of hydrocyanic acid?  Is it used
in  medical practice?  731. What is said of the sulphocyanates? 732. How
is sulphocyanate of potassium formed?  7383. Sulphocyanic acid?
41*




486      COMPOUNDS OF CYANOGEN AND) THE METALS.
734, The following compounds are derived mostly from the sulphocyanates:
l-iellon, C6N,, is a yellow insoluble compound, obtained by distilling
sulphocyanate of potassium in an atmosphere of chlorine.  It is capable
of combining with metals, forming compounds which are called mellonides.  _eslam, C12H lNs, is a grayish-white powder, procured by decomposing, by heat, the sulphocyanate of ammonia.  Jirelanzine, C6H6N6,
results from the action of solution of potash, at a bciling heat, upol
melam.  It is a transparent solid, scarcely soluble in water, if cold, bu1
very soluble in boiling water. When dry it may be sublimed.  At t] o
same time with the compound just described is formed anlmeline, CI6H5N,02
a basic substance, capable of combining with the nitric and other acids,
to form salts. It crystalizes in fine silky needles.  Amnmmelide, C12H, 9Ng 6,
is formed by boiling ammeline in some'acid;-it is a white compound,
insoluble in water and alcohol, and possesses little interest.
(lompounlds of (Jyanoqen and the JIetals.
7'35. C(yanogen combines readily with nearly all the metals3
but a few only of the more important of the compounds thus
formed can be here noticed.
736. Cyanide of Potassium, K,C,N, Oc  KCy.-This compound
is best prepared by heating in a covered crucible 8 parts of yellow prussiate of potash, and adding three parts of pearlash, both
being first well dried.  On the large scale for the manufacture
of prussiate of potash above mentioned, it is prepared by heating
together in an air-furnace animal charcoal and pearlash. This
cyanide thus formed, acting afterwards upon iron, or oxide of
iron present, produces the yellow prussiate soon to be described.
Cyanide of potassium is largely used at the present time in the processes of gilding and plating by means of galvanism.
737. Cyanide of Mercury, IIgCy, is prepared by pouring a hot solution
of nitrate of silver into a hot concentrated solution of cyanide of potassium, and purifying, by recrystalization, the. solid cyanide of mercury
which is deposited when the mixed solution cools.  It has already been
mentioned as affording  a ready means for procuring cyanogen.
738. Cyanide of Silver, AgCy, is precipitated as a solid compound by
mixing hydrocyanic acid with solution of any salt of silver.  It is insoQUESTIONS.- 734. What other compounds are mentioned as derived
from the sulphocyanates?  735. What is said of cyanogen in relation to,the metals?  736. HIow is cyanide of potassium formed? What use is
made of it?  737. What is said of cyanide of mercury?  738. Cyanide
of silver?




DOUBLE  CYANIDES.- IOLYCYANID)ES.  487
llble in water, but is soluble in aqua ammonia, and in solution of nitrate
of silver.
By modes altogether similar to the above, the cyanides of gold, zinc,
cobalt, nickel, lead, copper, palladium, &c., mlay be procured, but the
compounds are not here described.
Douzble Cyanides.-Polycyanides.
739. Nearly all the metallic cyanides are remarkable for thei.
tendency to combine with each other, so as to form double cyanides, This is especially true of the cyanides of iron, but many
others of the class show the same tendency.
740. I1ydroferrocyanic Acid, FeCy,2HCy==H2Cy,Fe.-This
acid is best prepared by mixing a saturated solution of yellow
prussiate of potash with strong hydrochloric acid, firee from contact with the air, and then adding a small quantity of sulphuric
ether.  The acid is at once precipitated in small white crystals,
which are to be collected and'dried in a vacuum, after being
washed with ether.
This acid may be preserved any length of time free from contact with
the air and moisture; but in the air it is gradually decomposed, leaving
a residue of Prussian blue. It acts readily upon the metals and meta.llic
oxides, producing ferrocyanides.
741. Ferrocyanide  of Potassium. - Yellow  Prussiate  of
Potassa- 2KCy,FeCy,3H0 = K2Cy,Fe,3H10. -  This compound
is prepared, on the large scale, by heating potash with animal
matter, as horns, hoofs, leather, woollen rags, hair, and other
animal offal, by which cyanide of potassium  is formed; which,
being digested with warm water, containing fragments of iron or
smithy scales, acts upon the iron to produce the compound in
question.  After filtering, the yellow Prussiate, in solution, is set
aside to crystalize.  Instead of animal substances, as here described, common charcoal alone may be used with the carbonate
of potash, and bringing in contact with it when intensely heated
atmospheric nitrogen, prepared by passing a current of air through
burning coke.
QUESTIONS.-739. What is said of nearly all the metallic cyanides?
7410. How is hydroferrocyanic acid prepared?  741. Describe fcrrocyanide of potassium.




488   DOUBLE  CYANIDE S.-POLYCYAN I                       D ES.
Ferrocyanide of potassium is a crystaline solid, of a lemonyellow color, very soluble in water, but insoluble in alcohol and
ether.  It is much used in the arts as a coloring substance, and
as an important reagent in the laboratory of the chemist.
Many other ferrocyanides, as those of sodium, barium, calcium, &c,
must be passed by unnoticed.
742. Hydroferrideyanic Acid, 3 HCy,Fe2Cy, - H3Cy6,Fe2. -
This compound is prepared by passing a current of hydro-sulphuric acid gas through a newly prepared solution of ferrid.
cyanide of lead.  It is obtained in crystals, which are soluble in
water, and have an acid, astringent taste.
It may be considered as a compound of 3 equivalents of hydrocyanic
acid with sesquicyanide of iron, as indicated by the first of the above
formulae, or as a compound of 3 equivalents of hydrogen with the
assumed radical Cy6Fe2, as indicated by the second formula.
743. Ferridcyanide of Potassium. —Red Prussiate of Potash,
3KCy,Fe2Cy3=K3Cy6Fe2. —Red prussiate of potash is prepared
by passing a current of chlorine through a solution of the yellow
prussiate, until it ceases to give a blue precipitate with solution
of the persalts of iron, and evaporating the solution until crystalization takes place.
The action of the chlorine is to separate from 2 equivalents
of the ferrocyanide one equivalent of potassium, thus forming
chloride of potassium  and the compound in question.   Thus
2(2KCy,FeCy) + C1 = I3KCy,Fe2Cy  + KC1, the water always
contained in the crystal of the ferrocyanide being omitted.
The crystals belong to the trimetric system, are of a red color,
and readily burn when held in the flame of a candle. They are
partially soluble in cold and very soluble in boiling water, but
insoluble in alcohol.
Sometimes, during the process, the solution becomes green, by
the formation of the magnetic cyanide of iron (FeCy,Fe2Cy,),
which, however, disappears by boiling with a little caustic potassa.
Ferridccyanide of potassium forms characteristic colors with solutions
of several of the metals, producing with them precipitates in which the
QUEsTIONs.-What use is made of ferrocyanide of potassium? 749. How,may hydroferridcyanic acid be procured? Of what is it composed? 743. Describe the red Prussiate of potash. W.hat is said of the colors produced by
this compound with metallic solutions?




DOUBLE  CYANIDES. —  OL YCYA NIDES.    89
potassium of the ferridclcyanide is replaced by an equal number of equivalents of the new metal. Thus, with solution of the protosalts of iron it
gives a blue, with those of uranium a reddish-brown, with those of nickel
and bismuth a brownish-yellow, and with those of silver and zinc an
orange yellow.
Similar compounds of sodium, barium, calcium, and magnesium are
known.
744. Ferridcyanides of Iron. — Prussian Blues. — There are
several different compounds known by these names.   The one
most common is'prepared by precipitating an acid solution of
sulphate of iron with solution of the yellow prussiate of potash.
The compound thus formed is of.a deep blue color, uncrystalizable,
and insoluble in water and alcohol. When properly dried, it has
a peculiar metallic, coppery lustre, and is much used by painters;
but the color is liable to fade, and is at once destroyed by the
action of the caustic alkalies which decompose it.
The production of the proper blue precipitate in this case requires the
presence of the air, from which oxygen is largely absorbed. When a:itLt of the peroxide is made use of, this is not required.
T'he Prussian blue of commerce is very soluble in solution of oxalic
acid, and a good blue writing-ink is prepared from it.
Prussian blue receives its name from the fact that it was first made at
Berlin, Prussia, about the year 1710. It is sometimes called Berlin blue.
The compound just described as the ordinary Prussian blue of commerce, is probably a mixture of several different cyanides of iron.
Ttlrnbull's or Paris blue, 3FeCy,Fe,Cy,, is a definite compound; it is best prepared by mixing a solution of the red
Prussiate of potash with solution of a protosalt of iron, the 3
equivalents of potassium in the Prussiate being replaced by 3
equivalents of iron.  Its color is less intense but more clear than
that of the ordinary Prussian blue.  Its formula may be written
Fe,Cy6Fe,.
By precipitating solution'of pernitrate or perchloride of iron
with a solution of yellow Prussiate of potash, a definite compound
is also formed sometimes called neutral Prussian blue, or sesquifericyanilde of iron, or l7nfqrridccyanide ofiron.  Its composition
is 3FeCy,2FeCy,.  This probably constitutes the chief part of the
common Prussian blue of commerce.
QUESTIONS.-744. What is said of the Prussian blues?  How anny a
blue writing ink be formed from Prussian blue?  May other Prussian
blues be formed?




490              PROTEINE  COMPOUNDS.
Another compound, called basic Prussian blue, is formed by proe
cipitating a protosalt of iron with solution of ferrocyanide of
potassium, and exposing the white compound thus obtained for
some time to the action of the air for the absorption of oxygen.
Several other similar cyanic compounds of iron are known, called
soluble Prussian blues, but they cannot here be particularly described.
745. Cobaltocyanides.-Several other metals, as cobalt, nickel,
and mercury, enter into combination with cyanogen, forming comrcunds in which these metals perform  essentially the same office
as the iron in those of the above list.
746.  ydrocobaltocyanic Acid, 3HCy,Co2Cys= I-3Cy6Co2, is obtained
by decomposing cobaltocyanide of lead by hydrosulphuric acid, separatinag the sn'lphide of lead by filtration, and then evaporating so as to
crystalize.  The crystals thus procured are colorless and fibrous, and
very insoluble in water.  The solution has a very sour taste, and acts
readily upon the alkaline carbonates with effervescence.
It will be seen that this compound corresponds to the hydroferriclcyanic
acid of the iron series of cyanic compounds.  Like that acid, too, it
is tribasic.
747. Cobalticyanide of Potassiuzm, 3KCy,Co2Cy-3 = KCy6Co2, is formed
by dissolving cobalt, or its carbonate, or cyanide, in solution of cyanide
of potassium  containing excess of hydrocyanic acid, and evaporating so
as to crystalize.  It will be noticed that the compound is altogether
analogous in composition to the ferridclcyanide of potassium, with which it
is also isomorphous.  The crystals are of a yellowish color, and are very
soluble in water, forming a colorless solution.
Very many other metallic polycyanides are known, as the platinocyanides, aurocyanides, argentocyanides, mercuriocyanides, &c., but it would
extend our work too much to describe them.
ALBUMINOUS, OR  PROTEINE  COMPOUNDS.
748. These compounds, three in number, arefibrine, albumen,
and caseine.   They are found both  in vegetable and animal
bodies, and, like sugar, starch, and woody-fibre, are capable, in
certain circumstances, of being converted into each other.  They
are believed to be compounds of a proximate principle called
QUESTIONS.-745. What other metals form  cyanides similar in their
properties to those of iron?  746. Describe hydrocobaltocyanic acid.
7417. Describe cobaltocyanide of potassium.  Are there other metallic
polycyanidos?  748. What are the albuminous or proteine compounds?




PROTEINE COMPOUNDS.                          491
proteine, (proteuo, I am  first), and having  the  composition,
C40113,N5012.  Its real composition, however, cannot be considered
as settled.
To obtain proteine, albumen or caseine is to be digested suc-.cessively in water, alcohol, and ether, in order to separate everything that is soluble in these liquids; and the mass that remains
is to be soaked for a time in diluted hydrochloric acid, and then
dissolved in a weak solution of caustic potash.  From this, acetic
acid, cautiously added, precipitates the proteine.
As thus obtained, proteine is a white, inodorous solid, which is
insoluble in water or alcohol, and is capable of forming different
compounds both with acids and bases. From its acid compounds
it is readily precipitated by tannic acid, with which it forms an
insoluble compound, by ferrocyanide of potassium, and by the
alkalies.
In the open air it rapidly absorbs moisture, and becomes a gelatinous
mass; and by heat is decomposed, exhibiting the phenomena usually
attending the combustion of nitrogenized bodies. It leaves no residue
after combustion.
749. Fibrine.-Gluten. — Fibrine receives its name from  the
circumstance that it enters largely into the composition of tl:e
muscular fibre of the animal system.
It is best obtained by whipping a quantity of fresh-drawn blood
with a bunch of twigs, until it coagulates, and then carefully
washing with water the stringy mass thus obtained.   Subsequently it is to be washed with alcohol and ether, to remove all
fatty matter adhering to it, and dried.
When thus obtained, fibrine is a yellowish opake mass, whicth
is quite insoluble in water, alcohol, or ether.  When long digested
in water, at a very high temperature, a small proportion is dissolved, but slight decomposition also takes place.   It is not
soluble in the acids, but dissolves readily in dilute solutions of
t}e alkalies.
Fibrine, obtained in the above manner from venous and arteri:tl
blood, does not appear to be exactly the same in all its properties;
QUESTIONS.-Is the composition of proteine known with certainty?
HIow may it be obtained?  What are its properties?  749. From what
does fibrine derive its name?  How may it be procured?  Is it the
same, whether obtained from venous or arterial blood?




192             PROTEINE  COMPOUNDS.
as that from venous blood, when triturated with solution of nitrate
of potash, at a high temperature, it becomes soluble, and very muchk
resembles albumen, while that from  arterial blood is not so
affected.
Fibrine may also be obtained from the flesh of animals, of
which it seems to form the essential part.  When procured from
this source, it resembles that from venous blood.
When the juice of various roots, as beets, turnips, carrots, &c., is
allowed to stand for a time, a portion of it coagulates very much like
blood, and may be separated from the uncoagulated part. It has been
called vegetable fibrine, and seems to be the same as fibrine of animal
origin.
750. Gluten is a substance obtained from the cereal grains
It may be procured readily from wheat flour by kneading (554) it
for some time in a large quantity of cold water, to wash away all
the starch and other products, and then boiling for a time in
alcohol.  A soft, adhesive, elastic mass is thus obtained, which
appears to be identical with fibrine.  It is to this substance that
wheat flour (which. contains 20 or 25 per cent. of it) owes its
adhesive, plastic nature; and it is this substance also, in a state
of decomposition - mixed, probably, with starch in the same
state-which constitutes yeast.
751. Albumen. —This compound is found nearly pure in the
whites of eggs, from which it derives its name. Like fibrine, it
exists in two states-as a liquid, in the whites of eggs, serum
of the blood, humors of the eye, &c.-and, as a solid, in the brain
and nerves of animals, and in the seeds of plants.  The latter,
called vegetable albumen, is considered as altogether identical with
that of animal origin.
Liquid albumen may be coagulated, or solidified in various
ways, as by heating to a temperature of 1400, or more, or by the
action of chemical reagents, as alcohol, tannic acid, corrosive sublimate, and creosote; but when once coagulated it cannot be redissolved.  As it forms an insoluble, and therefore inert compound with corrosive sublimate, it is considered a good antidote
in cases of poisoning with the latter substance.
QUESTIroNs.-What is said of the juice of certain roots, as those of beets,
turnips, &c.?  750. What is gluten?  What is yeast?  751. Describe
albumen.




PRO rEINE  COMPOUNDS.                        493
Vegetable albumen is found in the leaves and stalks of plants, and in
the seeds, and in some cases in the roots. As obtained from plants, it is
sometimes white, but is often colored. It is contained in considerable
quantity in wood, and has great influence in causing its decay. It is
therefore found that wood which has been saturated with a solution of
corrosive sublimate is rendered more lasting when subjected to the
influence of the atmosphere and moisture (501).
752. Caseine.-Legumine. —Caseine in many of its properties
closely resembles albumen.  It is most readily obtained from
milk; and derives its name from  caseum, curd.  A very little
Fulphuric acid stirred in some skimmed milk causes it to coagulate in a short time; and the curds so formed being well washed
with water, and digested for a time with carbonate of baryta to
separate the acid, afford the pure caseine.  When dried it is but
slightly soluble in water, but very soluble in solutions of the alkalies, or alkaline carbonates.
LeguSnine, believed to be identical with the caseine from milk,
is procured from peas, beans, and other similar seeds, by bruising
them in water, and straining through a fine sieve; the liquid
which passes through is a solution of this substance, and contains
some starch, which settles by standing. The supernatant liquid,
being poured off, possesses all the characters of skimmed milk,
and from it the legumine, or vegetable caseine, may be procured
in the same manner as from milk.
Caseine, in milk, is held in solution by free alkali present;it is not coagulated by heat, like albumen, but coagulates readily
by the action of repnet, or by acids, except the phosphoric.
The three important compounds above described very closely resemble
each other in many of their properties, as well as in composition; but
they are at the same time, in other properties, essentially different.
Fibrine coagulates spontaneously by standing, but the other two undergo
this change only by the application of certain agents. Albumen is not
coagulated by acids, nor by rennet, but coagulates by heat, by contact
of alcohol, and some of the metallic salts, and other compounds. Caseine
does not coagulate by heat, nor by alcohol, but is readily coagulated by
most of the acids, and by rennet. Probably what is considered as liquid
caseine is only the substance held in solution by an alkali; and the
coagulation of it by an acid results from the neutralization of the alkali
by the acid.
QUESTIONS.-In what parts of plants is vegetable albumen contained?
752. Describe caseine. Describe legumine. How is caseine coagulated,
How are fibrine and albumen coagulated?
42




494    PHENOMENA OF VEGETATION.
Each of these substances appears always to contain a small quantity
of sulphur; and fibrine and albumen contain, in addition, a little phosphorus. Decomposed by heating with acids or other reagents, they afford
very complex results.
When kept for a time they undergo spontaneous decompostion, and in
certain circumstances also induce peculiar changes in other organic compounds, as in the production of the alcoholic and other fermentations.
Being so nearly the same in composition, if not absolutely identical, it
is altogether probable that, both in vegetables and animals, frequent
transformations of one of these substances into another take place, by
means and processes not yet understood.
CHEMICAL PHENOMENA OF VEGETATION.
753. Geirmination. is the process by which a new plant originates from  seed.  A seed consists essentially of two parts, the
germ of the future plant, endowed with a principle of vitality,
and the cotyledons, or seed-lobes, both of which are enveloped in a
common covering or cuticle.  In the germ two parts, the'radclel
and plumula, may be distinguished, the former of which is destined to descend into the earth and constitute the root, the latter
to rise into the air and form  the stem of the plant.  The office
of the seed-lobes is to afford nourishment to the young plant until
its organization is so far advanced that it may draw materials for
its growth from extraneous sources.
The conditions necessary to germination are threefold; namely,
moisture, a certain temperature, and the presence of oxygen gas.
The necessity of moisture to this process has been proved by
extensive observation.  It is well known that the concurrence
of other conditions cannot enable seeds to germinate provided
they are kept quite dry.
A certain degree of warmth is not less essential than moisture.
Germination cannot take place at a very low temperature; and
a high temperature, as that of boiling water, destroys the vitality
of the seeds.  The most favorable temperature for the germination
of most seeds is between 600 and 800~.
In the process of incipient germination a kind of saccharine fermentLation (556) takes place, by which nutriment is supplied for the young
QUESTIONS.-753. What are the essential parts of a seed? Describe
the process of germination in a seed?  What are the conditions re quired
for healthy germination?




PHIENOMENA  OF VEGETATION.                         495
plant during the early stages of its growth. This seems to be occasioned
bly the influence of the active principle diastase, which is not pre-existent
in the seed, but is formed by the action of the air and moisture on the
substances contained in it. When the process of germination is over, the
plant is found provided with the necessary organs for procuring its nutriment from the atmosphere and soil; and there remains of the seed only
its ligneous husk, which sometimes perishes in the ground, but at others
rises to the surface and performs for a time the functions of leaves,
754. Respiration of Plants. -  Assinilation of Carbon. -  We
have already noticed (213) the beautiful provision, by which the
two great classes of organized bodies mutually compensate for the
change each produces in the constituents'of the atmosphere, and
continue that proportion of them which is conducive to the
healthful existence of both.  Animals, by respiration, are constantly giving off carbonic acid, while plants, by the action of
light upon their leaves, absorb carbonic acid and exhale oxygen.
It will be seen, therefore, that a process is ever going on in
plants-at least when under the influence of light-not unlike
the respiration of animals, in which the leaves perform the office
of lungs.  But the changes produced in the atmosphere being the
reverse of those occasioned by the respiration of animals, the two
processes serve to  support each  other; and  the proportional
quantity of oxygen and carbonic acid in the atmosphere is preserved ever the same.
The carbon obtained by plants by this respiratory process, and the
water which is absorbed by the roots and leaves, furnish the elements
of woody matter, and other substances, as sugar, starch, gum, &c.,
which contain oxygen and hydrogen in the proportion to form water.
But the actions that really take place are usually much more complex
than this would seem to indicate. The absorption of carbonic acid, and
the liberation of oxygen, take place only in the light; in the dark, an
opposite process sets in-oxygen is absorbed and carbonic acid is given
off. But it has been well established that, on the whole, the quantity
of carbonic acid absorbed is much greater that that evolved, whilst the
quantity of oxygen evolved is much greater than that absorbed. Very
many plants, it is believed, receive a large part of the carbon they contain from the atmosphere, while some few probably receive the whole.
Others derive a part from the soil.
Now it is not difficult to trace some of the further changes which no
doubt take place in the plant. All the softer parts of most plants conQUESTIONS.-754. What is meant by the respiration of plants?  What
different effects are produced upon the atmosphere by the respiration
of plants and animals? Does the absorption of carbonic acid take place
orTv in the light?




496         PHENOMENA  OF VEGETATION.
tain abundance of starch; even in the tubes and cells of ordinary wood
it is found. This is so closely allied to sugar, gum, and woody-fibre, and
the transformations of them from one to another so easy, that we may
suppose them to be constantly taking place.
The other numerous secondary products, as the vegetable acids, oils,
coloring-matters, &c., which characterize plants, may be formed from
starch during the inverse respiratory action just alluded to, in which
carbonic acid is given off, and oxygen absorbed from the atmosphere.
During the day the assimilating power of the plant is in action, and carbonic acid is rapidly absorbed, and oxygen evolved; but during the
night, while the plant is in repose, this nutritious action ceases, and a
different process commences, during which the various substances natural
to the plant are elaborated, attended by the absorption of oxygen from
the atmosphere, and the evolution of carbonic acid and water.  This
change is well illustrated by certain plants, as the cacalia ficoides, the
leaves of which are bitter in the evening, but in the morning are sour',
like those of sorrel. During the night oxygen has been absorbed, and
an acid generated from materials that were combined the evening previous,
in a different mode.
Nitrogen is an essential ingredient in many of the products of plants;it is believed to be obtained chiefly from the soil.
755. Inorganic  Constitutents of Plants. -Besides the substances which form  She organic matter of plants, various inorganic bodies, as alkaline and earthy salts, are usually found
contained in them, and no doubt serve an important purpose.
If a plant is made to vegetate in a soil containing in it small
quantities of several salts, we find that, while it continues in
health, it seems to exercise a remarkable discretionary power,
absorbing  some, and  rejecting  others.   Those absorbed most
freely are such as are required for its proper growth, and are
not given up to the water in which the plant may be immersed;
while some are absorbed and again given offW and others still
are entirely rejected, as being injurious.  Miost plants contain
a small quantity of some salt of potassa, which exists as a carbonate in the ashes resulting from their combustion; but plants
that grow near the sea, or springs of salt water, usually contain
soda instead of potassa.   Silica, lime, magnesia, &c., are also
often contained in plants.
As these inorganic substances are necessary for the proper growth
of plants, and all plants do not require the same substance, it is plain
that a particular plant can be expected to flourish only in soils containing
the substances it requires.
QuFSTIONs.-Is nitrogen assimilated by plants?  From  what is it
delived?  755. What are the inorganic constituents of plants?  Do different plants absorb very different substances from the soil?




PHENOMENA  OF VEGETATION.                        497
756. Ntature awnd Use of Manures.-Every substance is called
r manure which, applied to a soil, increases its productiveness.
In a particular case it may be a substance which is required in
the proposed crop, but of which the soil is deficient; or it may be
a substance designed merely to give the soil a proper texture, so
that it may more easily be penetrated by the rootlets of the plants,
or to increase its adhesiveness and enable it to retain longer the
moisture that falls upon it.  It is in the manner last mentioned,
probably, that most mineral manures, as lime, marl, &c., usually
operate.
From  the preceding remarks, the great advantage of rotatiom
of crops may readily be seen.  The mineral constituents of a soil
are derived from the disintegration of its subjacent rocks; and
some of them being contained only in small quantities, by continued succession of the same crop, may be entirely removed, and
the soil become impoverished.  By substituting another crop,
which requires little or none of the material which has been
exhausted, an abundant harvest may be obtained; and the soil,
by the gradual decomposition of its subsoil, recover its former
constitution.
757. The great value of organic manures is supposed to depend almost
entirely upon the nitrogen they supply to the soil.  The most of the
nitrogen in plants is contained in the seed, tubers, &c., those parts which
are selected by man for food, or for medicinal purposes, in consequence
of the active principles they contain; and but little is found in the stem,
leaves, root, &c., which are rejected as useless. The residue of a former
season, therefore, may manure the land abundantly, so far as carbon is
concerned, but there will be a deficiency of nitrogen, an essential element of the future desired crop.  This deficiency is supplied by the
dlecaying animal and vegetable substances used as manures; the value
of which will therefore be very nearly in proportion to the nitrogen they
supply. If mere ammoniacal salts are used, or perishable animal substances, their whole benefit is imparted to the crop immediately succeeding their application; but organic substances, which decay but slowly,
yield a more permanent benefit: their nitrogen is gradually evolved, and
though little benefit at first appears, the soil is at length found to be
essentially improved.
758. In healthy vegetation, light serves a most important purpose;
indeed, without it, no plant could come to perfection. A plant which
grows in darkness, as in a cellar, however rich may be the soil in which
QuI:sTIONs.-756. What are manures?  Explain the different modes in
which manures operate to produce their effects?  758. What is said of
the importance of light to healthy vegetation?
j,]o,.




4982                 ANIMAL TISSUES.
it stands, remains soft, its color pale, and its woody fibre unformed.
When brought to the light, it perhaps increases in volume less rapidly,
h)ut the healthy action of the organ at once commences; the green color
appears, and all the parts of the plant begin gradually to advance to
maturity.
COMPOSITION OF TiE ANIMAL TISSUES.
759. By the animal tissues we understand all the various solid
found in the system, not excepting the bones and teeth.
The JMluscles.-The muscles are the organs of motion to the
animal, and they act solely by their contractions, which take
place at the will of the animal. Their structure is always fibrous,
and in the mammalia they are of a red color, and receive from
the circulation a large supply of blood. The chief substances
contained in them  are fibrine, albumen, and gelatine.  The two
latter substances are contained  chiefly  in  the
membranes  which  envelope the fibres.
The accompanying fig-~zll~~ ~           N    ure represents a piece of
muscle, and  shows its
fibrous structure. When
Piece of Muscle.
P  taken from  the animal
and dried at a moderate temperature, it contracts greatly by the
loss of water, and its weight is eventually reduced to one-fourth.
760. The Cartilages, Skin, and lIenmbranes. —The cartilages
appear to have essentially the same composition as the skin and
the membranes generally.   They are all composed of gelatine
and chondline, both of which are entirely dissolved by long continnued boiling, and form  with water a transparent jelly.  Their
exact composition has not been fully determined.  Chondrine is
most abundant in the cartilages.
The common glue of commerce is dried gelatine, and is prepared by boiling cuttings of parchment, or the skins, ears, and
Q(JESTIONS.-759. What are the muscles of animals?  What are they
chiefly composed of?  760. What is said of the cartilages, &c.? What
is glue?




ANIMAL TISSUES.                          499
hoofs of animals, and evaporating the solution.  Its use is well
known.  Ising7ass, which is a very pure variety of gelatine, is
prepared from the sounds of fish of the genus acipenser, especially
from the sturgeon. The animal jelly of the confectioners is made
from the feet of calves, the tendinous and ligamentous parts of
which yield a large quantity of gelatine.
Gelatine is insoluble in alcohol, but is dissolved readily by most of the
diluted acids, which form an excellent solvent for it.
Gelatine manifests little tendency to unite with metallic oxides. Corrosive sublimate and acetate of lead do not occasion any precipitate in a
solution of gelatine, and the salts of tin and silver affect it very slightly.
By boiling gelatine with dilute sulphuric acid, and precipitating the
acid with chalk, a sweet crystaline compound is obtained called glycocoll
(g/lukes, sweet, and kolla, glue), or gelatine sugar, the composition of
which is C4H5NO4.
The action of tannin or tannic acid (684) upon gelatine is peculiar and
important, resulting in the production, in certain cases, of the well
known and most useful substance, leather.
Leather is usually formed by subjecting the skins of animals for some
time to an infusion of bark which contains a large proportion of tannic
acid; and the chief chemical change which takes place is believed to
consist in a union of this acid with the gelatine of the skin. This is the
common leather of which shoes are made: other varieties of this useful
manufacture are prepared by diffelent modes. Glove-leather, for instance,
is prepared by impregnating the skin, after having been deprived of all
its fatty matter by soaking in a weak alkali, with solution of common
salt and alum, from which chloride of aluminum is formed, and unites
with the gelatine of the skin.
The Brain and Nerves.-The substance of the brain, nerves,
and spinal marrow differs from that of all other animal textures.
The white and gray portions differ essentially in their nature,
but are composed chiefly of water, albumen, a fatty matter, and
traces of phosphates and other salts.  Only about one-fifth of the
wlhole is solid matter.  The fatty matter is peculiar, and is quite
unlike that of other parts of the system.  The phosphorus in the
brain is said to amount to 3 or 4 per cent. of all the solid matter
contained in it.
761. PTze Bones. -  The bones of animals consist of earthy
matter, which is chiefly phosphate and carbonate of lime, and
animal matter, which is essentially the same as cartilage. These
QUESTIONS.-Whlat is said of the action of tannic acid upoml gelatine?
Ilow is leather prepared?  761. What is said of the composition of the
bones?




13o                       THE  BLOOD.
may easily be separated from each other. To separate the solid
or eartbT matter, it is only necessary to digest the bone for a time
in dilute hydrochloric acid, in which both the phosphate and
carbonate of lime are soluble, so that they will be entirely removed, leaving  the cartilage  soft and  flexible, but retaining
perfectly the form of the bone.  The cartilage may be removed
by heating the bone some time in the open air, so as to burn
away all the organic matter; or by digesting it in solution of an
alkali, or in water at a high temperature, under pressure.  In
some cases of disease, as rickets, to which children and youth are
chiefly liable, there is a deficiency of earthy matter in the bones;
and they are, in consequence, weak, and incapable of affording the
necessary support to the system.
Ilfrn differs from bone in containing only a trace of earth. It consists
cliefly of gelatine and a cartilaginous substance like coagulated albumen.
The composition of the nails and hoofs of animals is similar to that of
horn; and the cuticle belongs to the same class of substances.
7062. The hair seems to have essentially the same composition as horn,
but the color is occasioned by an oil, which is soluble to ether, and may
therefore be removed by it. It contains sulphur, and is therefore blackcned by nitrate of silver, or other metallic salt.
When horn or hair is heated, it is first fused, and then swells up,
gliving off carbonate of ammonia, and carburetted hydrogen, the last
of which takes fire, and burns with a brilliant flame.
Shells are composed of a mixture of phosphate and carbonate of lime.
The shells of the crustacea, as lobsters, crabs, &c.., usually contain 4 or
(; per cent. of phosphate of lime, and 50 or 60 per cent. of the carbonate,
Utle rest being animal matter.  The shells of the molusca, as the oyster
and clam, are nearly pure carbonate of lime, containing only a mere
trace of animal matter.
T II E  BLOOD.-  P H ENOMENA  OF  R ESPI RATION
AND DIGESTION.
763. The support of life in animals is attended by many chemical
phenomena, which are constantly taking place in every part of the
body, but especially in the blood, the lungs, the digestive system,
and in the glands.  The substances taken into the mouth are
modified in the process of digestion, and distributed to every part
QuEsTioNs. -How does horn  differ in composition from  bones?
762. What is said of hair?  763. What is said of the chemical changes
Irwhich take place in the system 




THE  BLOOD.                         501
by the circulation of the blood, where they come in contact with
oxygen received from the air in the lungs. Among these different principles, received in the processes of nutrition and respiration, important chemical changes are taking place, by which the
animal heat is kept up, and the waste of all the various tissues
supplied, and, indeed, all the animal functions supported.
The blood of the different orders of animals is not the same,
but we propose here to speak of that of the higher orders, or
vertebrated animals, in which it is always of a red color.
In these, the blood which is brought from the lungs, and propelled by the heart through the arteries to every part of the
system, is of a bright red or scarlet color, and is called arterial
blood; but as it is returned to the heart by the veins, to be again
sent to the lungs, it is of a dark red or purple, and is called venous
blood.  The blood is therefore of two kinds; but, chemically,
they seem to be essentially the same.
Tlhe Blood.
764. C(Joposition of the Blood. — The blood is easily dis
tinguished from  all the other fluids by its color.  Its taste is
slightly saline, its odor peculiar, and to the touch it seems somewhat unctuous.  Its specific gravity is variable, but usually about
1'05; and in man its temperature is about 980 or 1000.  While
flowing in its vessels, or when recently drawn, it appears to the
naked eye as a uniform homogeneous liquid; but if examined
with a microscope of sufficient power, numerous particles of a
discoid form  are seen floating in a nearly colorless liquid.  Most
of these discs are red, and in the blood of man are about  I  1~th
of an inch in diameter, and one-fourth as thick; but there are
also others which are without color. The figure on next page
represents these discs in human blood, as seen under the microscope,-a and b colorless discs.  The figure at the right represents these discs as they are sometimes seen united in rolls like
pieces of coin.
QrEsTIoNs. —Is the blood the same in all animals?  What two kinds
of blood are there? 764. What is said of the composition of the blood?
How does it appear when viewed by the microscope?  What is the form
of these corpuscles? Their size?




502                    THE BLOOD
o   0
o                   o
Discs in Human Blood.
These discs vary considerably in size in the blood of different
animals, being considerably smaller in the blood of the common
domestic animals than in man, but larger and
0[~            of an oval form in oviparous vertebrates.  They
X ~ 0       are larger in the blood of the elephant (see
figure in the margin) than in that of any other
Q3   <'   a mammalian species.
765. When the blood is withdraw.n from the
/(I),  ( I system, these discs or globules contract into a
solid mass or coagulum, which, by standing,
Discs in the Blood of  entirely separates from the liquid serum.  This
the Elephant.    is a thin yellowish liquid, of sp. gr. about
103, and coagulates when heated to about 1400.  It has a slight
alkaline reaction, owing to the presence of soda, and contains a
considerable quantity of albumen.
In the living body the blood also contains fibrine in solution,
which, however, soon separates from  the coagulum  after its
extraction frem  the system.  Various salts also are found, as
common salt, phosphates of lime, magnesia, and ammonia, and
lactates of soda and magnesia.
The relative proportion of the ingredients of the blood must necessa:rily vary, independently of disease, even in the same individual,
according as the nutrition is scanty or abundant. Slight variations are
also occasioned by difference of age and sex.
QUESTIONS.-765. What change occurs in the blood when withdrawn
f'oln the system?  What substances are mentioned as contained in the
~4,fa!:l v




PHENOMENA OF DIGESTION.                           503'
The following table contains the results of several analyses of blood:W ater...................................................  90-5
Albumen..............................................   8'0
Chlorides of sodium and potassium............. -6
Lactate of soda and extractive matter........4.   4
Soda and phosphate of soda.......................41
Loss.....................................................  09
100-00
The coloring-matter of the blood is confined entirely to the discs or
corpuscles spoken of above, and has been called hematosine.  In many
of its properties it closely resembles albumen. It is composed of carbon,
hydrogen, nitrogen, oxygen, and iron, the latter of which constitutes
between six and seven per cent.
766. Coagulation of the Blood.-The coagulation of the blood,
to which allusion has already been made (765), consists in the
agglutination of the fibrine it contains, by which the red globules,
and other suspended particles, are inclosed, forming the clot.
The time required for the coagulation of the blood depends much
upbn temperature, being promoted by heat and retarded by cold.
The process is also influenced by exposure to the air.  If atmospheric air be excluded, as by filling a bottle completely with
recently-drawn blood., and closing the orifice with a good stopper,
coagulation is retarded. It is singular, however, that if blood be
confined within the exhausted receiver of an air-pump, the coagulation is accelerated.
Some substances, introduced into the blood, either retard or
entirely prevent its coagulation, as saturated solution of chloride
of sodium, hydrochlorate of ammonia, nitre, and a solution of
potassa.  The coagulation, on the contrary, is promoted by alum
and the sulphates of the oxides of zinc and copper.  The blood
of persons who have died a sudden, violent death, by some kinds
of poison, or from mental emotion, is usually found in a fluid state.
Phenoanena of Digestion.
767. Digestion is the process by which the food is fitted to
nourish the system, and supply the constant waste that is required,for the support of the powers of life.  The blood is the agent by
QUESTIONS.-What is the coloring-matter of the blood called? 766. What
is said of the coagulation of the blood?  767. What is digestion?




'504         PHENOMENA  OF DIGESTION.
which the matter required for the support of the system is supplied to the various parts where it is needed; but it is from the
food that it is first received.
768. The Saliva.-The saliva is a slightly viscid liquid, secreted by several glands about the mouth, called the salivary
glands.  It serves to keep the mouth constantly moist; and the
sight, or even thought of food, causes it to flow rapidly in the
mouth. Besides water, and a small quantity of several salts, it
contains a peculiar principle called ptyaline, which may be precipitated from it by absolute alcohol.
The use of the saliva is to mix with the food during mastication, and form a soft, pulpy mass, suitable to be swallowed.
Probably it aids also in the process of digestion, by fitting the
food to be more readily acted on by the juices of the stomach.
The saliva is often much affected by disease, and occasions the bad
taste in the mouth, especially on rising in the morning.  In some
diseases, as intermittent fever, it is often very acid.
769. The Gastric Juice.-The gastric juice is an acid fluid
secreted by the coats of the stomach, and contains in solution
several salts, mucus, albumen, and a nitrogenized substance called
pepsine.  It has the property of softening down and dissolving,
more or less perfectly, all the various substancss which serve for
food.  When the food is introduced into the stomach, it is there
intimately mixed with this juice, by the agency of which it is
converted into a semi-fluid matter called chyme.   That this
change is owing to the solvent power of the gastric juice has been
fully determined; and it seems to be well established as a further
fact, that the gastric juice secreted in the stomachs of animals
of any species is especially adapted for dissolving the particular
kind of food upon which the species usually feed.
While the food is in the stomach, it is constantly kept in
motion by a peculiar movement of the muscular walls of the
intestine, called its peristaltic motion.   This has the  effect
thoroughly to mix every part, and also to propel the mass slowly
forward.
QUESTIONS.-768. Describe the saliva. What purpose does it serve?
769. By what is the gastric juice secreted? What purpose does it serve9
What is chyme i2




PHENOMENA OF DIGESTION.                        505
The chyme, as it passes from the stomach, appears as a homogeneous, semi-fluid mass; but it has recently been found that
the solvent action of the gastric juice is chiefly limited to the
nitrogenized part of the fluid, as the albumen, fibrine, &c.; the
non-nitrogenized parts, as the starchy and fatty compounds, being
only mechanically divided and mixed up with the mass.
From the stomach, the chyme passes to a large intestine called
the duodenum, where it is subjected to the action of two other
fluids, the bile and the pancreatic juice, which we will now proceed to consider.
770. The Bile.-The bile is a liquid secreted by the liver, and
preserved in the gall-bladder, which, when the stomach is filled,
is slightly pressed and made to discharge its contents through a
small duct into the duodenum.  It is of a yellow, or greenishyellow color, and has a peculiar sickening odor, and a taste at first
sweet and then bitter, but exceedingly nauseous.  Its consistence
is variable, being sometimes limpid, but more commonly viscid
and ropy.  It contains a peculiar principle called cholesterine, and
two organic acids called the cholic, and choleic, both of which are
in combination with soda.
It seems now to be very well determined that one, if not the chief,
purpose served by the bile is to aid in the digestion of the fatty and oily
substances taken for food. In connection with the pancreatic juice, it
also aids in the separation of the chyle.
Biliary caleuli are concretions which occasionally form in the gallbladder, or duct leading from it. They differ much in composition, but
not unfrequently they are composed, in great part, of cholesterine.
771. The Pancreatic Juice.-This is a secretion of a certain
organ called the pancreas.  It is a limpid, colorless, alkaline
liquid, with a saltish taste, like that of the serum of the blood.
It is slightly viscous, and coagulates by heat, and by the acids.
The pancreatic juice is poured into the duodenum at the same
time with the bile. Both of these liquids act energetically upon
fatty and amylaceous substances, and produce important changes
QuEsTIoNs.-What fluids are poured into the blood next after it leaves
the stomach? 770. By what organ is the bile secreted? Describe it.
What compounds are contained in it?  What purpose is served by it?
771. What is the character of the pancreatic juice?
43




506        PHENOMENA  OF RESPIRATION.
in them, by which they are prepared to enter into the circulating
system.
We have seen that the substances taken for food, after having
been acted upon in the stomach by the gastric juice, and reduced
to a homogeneous mass called chyme, pass into the duodenum,
where the mass receives the bile and the pancreatic juice; immediately a change takes place, and a milky liquid appears diffused
through the mass, called chyle.  This is the part of the food,
which, by the digestive process, has been prepared for the nourishment of the system, the rest being thrown off as refuse matter;
and, as the mass passes on through the intestinal canal, it is
absorbed by numerous little tubes opening into its side, called
lacteals, and conveyed by them to a common reservoir, the thor-acic
duct.  From  this it is discharged into the left subclavian vein,
and becomes incorporated with the blood, forming a part of its
substance, and fitting it for the proper continuance of its functions.
Phenomena of Respiration.
772. All organized bodies require constantly the presence of
atmospheric air for the proper performance of their various functions, and their continued existence in the living state.  All the
larger land-animals are provided with lungs, in which, by the
action of certain muscles, air is constantly inhaled and again
expelled, and thus a continued circulation is kept up; but in
some of the smaller ones, as insects, the breathing is by tubes
called trachea, or is performed by the whole surface of their
bodies. In fishes, certain organs called gills perform the cffice
of lungs, and the air that is breathed is first absorbed by the
water, and from  this imparted to the animal.  In every case the
process by which the air is made to perform its office upon the
living being is called respiration.
The important chemical changes that attend the respiration
of animals are, the constant absorption of oxygen, and the formation and evolution of carbonic acid.
QvUESTIONS.-What is the chyle? What purpose does it serve?  Tow
is it conveyed to the blood?  772. Do all organized bodie, require the
constant presence of air?  What purpose is served by the lungs of anlimals? What important changes attend the respiration of a, nimals?




PHENOMENA  OF RaESPIRATION.                      507
To show the presence of carbonic acid in the air
expelled from the lungs, it is only necessary to apply
a small tube to the mouth, and blow, a few seconds,
in to some recently-prepared lime-water;-the carbonic
acid in the air from the lungs will unite with the lime,
forming carbonate of lime, which gives the solution a
milky appearance. It is true, there is a little carbonic
acid in the air before it is taken into the lungs; but while
there the quantity is very considerably increased. This
is shown satisfactorily by blowing in the same manner
by a hand-bellows into another portion of lime-water,
when it will be found that a much longer time will be ing through
required to produce the milkiness alluded to (304).  Lime water.
773. The change in the blood from the venous to the arterial
state, is effected in the living animal during the passage of the
blood through the capillary vessels of the lungs, where it is
exposed to the action of an extensive surface of atmospheric air,
through the thin membranes which separate these from the airvessels; and the arterial blood, in traversing the capillary system
of the body, imparting nourishment to it, gradually assumes the
dark-colored condition in which it is returned to the heart by the
veins. The same change is produced when venous blood, just
taken from the system, is brought in contact with atmospheric
air, and is attended with the evolution of carbonic acid gas.  It
takes place more speedily when air is agitated with blood; it is
still more rapid when pure oxygen is substituted for atmospheric
air; and it does not occur at all when oxygen is entirely excluded.
The quantity of carbonic acid developed very exactly corresponds
with that of the oxygen which disappears.
The quantity of oxygen withdrawn from the atmosphere, and of carbonic acid disengaged, is variable in different individuals, and in the
same individual at different times, depending very much upon the state
of the system. In a state of health, anything that accelerates the respiration increases the amount of oxygen absorbed, and the quantity of carbonic acid exhaled; but in certain cases of disease, as in inflammatory
fevers, though the respiration may be very rapid, little oxygen is withdrawn from the air, and the venous blood is found to be very florid.
QUESTIONS. —How may the presence of carbonic acid in the air exhaled from the lungs be shown?  773. How is the change in the blood
firom the venous to the arterial state effected?  What change is again
produced in the blood as it circulates through the system?




508        PHN O ENOMENA  OF RESPIRATION.
774. Amimcal leat.-N-utrition.-It has long been known that
there is a close connection between the function of respiration,
and the development of heat in the animal system,
Thus, in all animals whose respiratory organs are small and
imperfect, and which, therefore, consume but a comparatively
minute quantity of oxygen, and generate little carbonic acid, the
temperature of the blood varies with that of the medium in which
they live. In warm-blooded animals, on the contrary, in which
the respiratory apparatus is larger, and the chemical changes more
complicated, the temperature is almost uniform; and those have
the highest temperature whose lungs, in proportion to the size
of their bodies, are largest, and which consume the greatest
quantity of oxygen.  The temperature of the same animal at
different times is connected with the state of the respiration.
When the blood circulates sluggishly, and the temperature is
low, the quantity of oxygen consumed is comparatively small
but, on the contrary, a large quantity of that gas disappears when
the circulation is brisk and the power of generating heat energetic.
It has also been observed, that when an animal is placed in a very
warm atmosphere, so as to require little heat to be generated
within his own body, the consumption of oxygen is unusually
small.
We have seen already that the digestion of the food is performed, in part, in the stomach, by the gastric juice dissolving
the nitrogenized or albuminous portion, and partly in the duodenum, where the amylaceous and fatty parts are acted on by the
bile and pancreatic juice. This indicates an important division
of the substances taken for food into two kinds; and we find that
the same distinction is also observed in the purposes they serve
in the system.  It has been determined that the albuminous or
nitrogenized parts of the food, go to support the waste of' the
tissues, while the non-nitrogenized parts, as starch, sugar, and
the fats and oils, are consumed in preserving the temperature
QUESTIONS. —774. Is there any immediate connection between the
function of respiration of animals and thee temperature of their systems?
What facts are mentioned as illustrating and proving the point?  What
two purposes are served by the food?  What ave the elements of respiration and nutrition?




PHENOMENA  OF RESPIRATION.                       509
of the system.  The latter may therefore be called the elements
of respiration, and the former elemenzts of nutrittion.
775. The combustion of carbon and hydrogen in the open air,
as is well known, is always attended by the evolution of heat;
and the same effect is produced in the system when these substances unite with the oxygen introduced into the blood in the
process of respiration.  The only essential difference is, that in
combustion the process is more rapid, and the heat produced proportionally more intense; but the absolute quantity of heat produced by the consumption of a given amount of carbon or
hydrogen is, in all probability, always the same.
We here find the origin of the carbonic acid which is given
off during respiration, and also by the insensible perspiration
fronl the skin, while the water produced by the combustion of the
hydrogen unites with the large quantity ever present in all parts
of the body.
We see, therefore, that the oxygen of the air is tending to consume all
living beings, as really as if they were in a burning fire; in fact, this
consumption, which is a kind of combustion, is ever going on while
eespiration continues. To keep up the combustion, a constant supply
of fuel is needed, which is found in the respiratory food, as before
stated; and when these elements enter into combination within the animal system, heat is as necessarily developed as when the same thing
takes place in the open air, in ordinary combustion.
776. Use of the lFut in, the Animal Econoniy.-The fat and
oils found in animals appear to be stores of respiratory food, laid
up by a wise foresight of nature for time of need.  Thus, it is
well known that when food is abundant the fat accumulates,
which is again gradually wasted away when the supply of food
becomes deficient. When the supply of food is wholly withheld
from an animal, the fat rapidly disappears, its carbon and hydrogen
going to supply the demands of respiration; and when this has
all been consumed, the substance of the muscles is attacked,
which become lean and flaccid, and lose their contractile power;
and at length the brain and nerves yield to the same influence,
QuESTIONS.-775. What always attends the combustion of carbon and
hydrogen? Is the same effect produced in the animal system? 776. What
purpose is served by the fat in the animal system? What becomes of the
fat when the supply of food is short?
43 *




51. O            ANIMAL  SUBSTANCES.
and death speedily closes the scene of suffering..  In animals that
lie torpid during the winter, nature has provided that in the summer season a large accumulation of fat is laid up to supply the
demanqcs of respiration during the time they lie torpid in their
dens; and, on the approach of the warm weather of spring, they
are consequently found lean and weak.
It is important to observe that the composition of the nitrogenized food
consistin.g chiefly of the proteine compounds and gelatine, is the same a
that of many of the tissues, the waste of which it supplies; and it is the
opinion of many that these compounds are never produced in the animal
system, but are appropriatec directly from the food, unchanged.
It is, however, known that some substances are formed in the system
from the materials supplied by the food. Thus, it has been found that a
lean goose, fed on Indian corn, will in a few days increase in weight
several pounds, in consequence of the fat that will be formed in the system, which must have been contained in the corn, or formed from the
substance of the corn by the organs of the animal. Now that the most
of it has been formed in the latter mode is certain from the fact that all
the oil or fatty matter contained in the corn will amount only to a small
fraction of the fat found in the goose. So bees will form wax when fed
on pure honey or pure sugar. It has been found by experiment that fox
twenty parts of honey consumed they will form about one part of wax,
SEVERAL ANIMAL SECRETIONS AND EXCRETIONS NOT BEFORE NOTICED.
777. M3i7k. —This well-known liquid is secreted by females
of the class mammalia, for the support of their young.  It is of a
white color, and is a little heavier than water, usually having a
density from  1'02 to 1'04.  Its composition varies in different
animals, and also in the same animal, according to the food that
is taken.  On an average, that of the cow contains, in an hundred parts, water 87-4 parts; butter, 4-0; milk-sugar, or lactine,
and soluble salts, 5-0; caseine, albumen, and insoluble salts, 3a6.
When milk is examined by a microscope, it is found to be a
transparent liquid, with numerous minute globules floating in it,
which consist chiefly of fatty matter, and which, if the milk stand
at rest a few hours, rise to the surface as cream.  If, now, the
cream is separated, and violently agitated for a time, the memQUESTIONS.-777. What substances are contained in cow's milk. What
is cream?




AN IM NAL SUBSTANCES.                      511
branes enveloping these fatty corpuscles are broken, and it collects
into a mass of butter, which floats in the watery liquid.
SMilk is not coagulated by heat, but this effect is readily produced by acids and by rennet, which is prepared by soaking the
inner coat of a calf's stomach in water.  The coagulum so formed
is called curd, and when pressed and otherwise prepared, con.
stitutes cheese.
778. When milk is allowed to stand some hours, at a tempera.
ture of between 600 and 70~, it sours; and, on examination, a
peculiar acid is found in it called lactic acid, the composition of
which is C61606.  When highly concentrated, it is a thick,
colorless liquid, of specific gravity 1'21, and has a very sour taste.
It is soluble in alcohol and water, but cannot be crystalized.
Lactic acid may also be formed from sugar by mixing with it
in solution some curds from milk, and some chalk to unite with it
as it is produced, and allowing the whole to stand for some time
at a temperature of about 80~.  The chemical change that takes
place appears to be very simple, as an atom  of fruit-sugar contains
exactly the ingredients of two atoms of lactic acid.  Thus,
C,22,20,2 = 2(C61H606).  It is this acid which is contained in
the gastric juice.
Lactic acid is also formed when the juices of beets, carrots, &c.,
are allowed to ferment at high temperatures.  At the same time
a viscid, slimy substance is formed, from which circumstance this
has been termed the viscous fermentation.
Milk may also be made to undergo the vinous or alcoholic
fermentation.  For this purpose it is exposed for some hours to
a temperature of about 100~; and the alcohol, which, no doubt,
is formed from  the milk-sugar. it contains, may subsequently be
distilled from it.  It has long been known that some barbarous
nations are accustomed to prepare an intoxicating drink from
milk, by some fermenting process.
779. Lymph.-Lymph is a watery fluid, secreted by many of
the membranes; it lubricates all the cavities, and moistens the
QUESTIONS.-778. What acid is formed in the souring of milk?  Mifay
it be formed from sugar? May milk be made to undergo the alcoholic
fermentation?  779. What is lymph?




512              ANIMAL  SUBSTANC E S.
cellular tissues of the body.  It much resembles the serum of the
blood, and mixes readily with water.  Sometimes, in diseases,
this liquid, or a liquid analogous to it, is secreted in one or more
organs, so abundantly as to constitute dropsy.
780. Urine. —This is a yellowish liquid, secreted by the kidneys, by which various substances, constantly accumulating in the
blood, are separated from it during the healthy state of the system.  This excretion is essential, as without it the substances
thus thrown off would, in a short time, accumulate in such quantity
as to destroy life. It has usually a specific gravity of about 1'02,
and consists of water, holding in solution a small portion of urea
and several different salts, as well as a little free acid, from which
it acquires an acid reaction. A little mucus is also usually present, derived from the urinary passages; and in consequence of
this it putrefies if kept for a time at a summer temperature.
The quantity of the urine is affected by various causes, espe.
cially by the nature and quantity of the food and the liquids
received into the stomach; but on an average, a healthy person
voids between thirty and forty ounces daily. The quality of this
fluid is likewise influenced by the same circumstances, being sometimes in a very dilute state, and at others highly concentrated.
~ The urine of birds, insects, and reptiles, is solid, and consists
chiefly of urate of ammonia.  Guano, which has been so largely
imported within a few years, to be used as a manure, is composed
chiefly of the urine and other excrements of birds, which have
been collecting for ages in the places where they are found.  It is
imported chiefly, if not entirely, from islands on the coast of
Africa, and the west coast of South America.
781. Urea, C,H,N,O, 0   CyO,NH, + HO.-This substance is
always found in healthy urine, and may also be prepared artificially. Its crystals, when pure, are transparent and colorless,
of a slight pearly lustre, and have commonly the form of a foursided prism.  It leaves a sensation of coldness on the tongue, like
QUaSTIONS.-780. What purpose is served in the animal system by the
secretion of the urine?  What is guano?  781. From what is urea
ob tained?




ANIMAL SUBSTANCES.                            513
nitre, and its smell is faint and peculiar, but not urinous.  Its
specific gravity is about 1'35.
Water, at 600, dissolves more than its own weight orfurea, and
boiling water takes up an unlimited quantity. It requires for
solution about five times its weight of alcohol at 60~, and rather
less than its own weight at a boiling temperature. The aqueous
solution of pure urea is very permanent, but if the other constituents of urine are present, it putrefies with rapidity, and, by a
heat of 250~, it is melted and resolved into carbonate of ammonia,
and other products.
Though urea has not any distinct alkaline properties, it unites
with the nitric and oxalic acids, forming sparingly soluble compounds, which crystalize in scales of a pearly lustre.
Urea is prepared artificially as follows. Four parts of dry Prussiate
of potash are intimately mixed with 2 parts of peroxide of manganese,
and heated to dull redness in a1n iron vessel. When the mass has become
cold it is digested in cold water, and frequently stirred, until all that is
soluble is taken up by the water.  This is now decanted, and mixed with
3 parts of sulphate of ammonia previously dissolved in water.  Sulphate
ot' potash and cyanate of ammonia are at once formed; and on the application of a moderate heat the latter compound is converted into urea, which
~is only an isomeric modification.
To separate the urea, the whole solution is evaporated to dryness, and
the urea taken up by strong alcohol.
782. Uric Acid, ClOT4N406, is found, in combination with bases,
in the urine of many animals, especially that of birds of prey, and
of serpents. It is a white, tasteless, and inodorous solid, but sparingly
soluble in either cold or hot water.  Urcte of amnmonia constitutes a large part of the best guano.
When uric acid is boiled with peroxide of lead a substance called
al/lantoine is formed, which has tile composition, CI8HoN406, carbonic acid
being also evolved.  It is a solid, and capable of being crystalized.
Boiled with the strong acids, it forms urea and allantoic acid, C6H,4N2O.
Alloxan, alloxantine, alloxanic, and dialuric acids, are other closely allied
substances.
783. Besides the above substances, there is found in the urine
of herbivorous animals, as the cow and horse, another important
Qur.s'rmoN-s.-Describe the artificial mode of preparing urea. 782. What
is ur'ic acid? 783. From what is hippuric acid obtained?




ANIMAL  SUBSTANCES.
acid, called the hUippuric acid (from  hippos, horse).  Its composition is CHIIN06 =  C,181HsN05 + HO.
To prepare this acid, the fresh urine may be concentrated by a
gentle heat,-taking care not to cause it to boil, —until its volume
is diminished one-half; and hydrochloric acid then added until
an acid reaction is produced.  By standing for a time, impure
Ilippuric acid will make its appearance in the form of long, slender
crystals.  These are then to be redissolved in boiling water, mixed
with some milk of lime and animal charcoal, and the resulting
solution of hippurate of lime carefully filtered before cooling.
To decompose this, hydrochloric acid is to be added until an acid
reaction appears; and, on cooling, the pure hippuric acid will be
obtained in beautiful crystals.  These are only slightly insoluble
in cold, but very soluble in boiling water.
Some of the relations of this acid are curious and important. When
boiled for some time with a strong acid, it is converted into benzoic acid
andl:l glycocoll (760), 2 atoms of water being absorbed in the process.
Thus,
C,18H9N06 + 2110 = C14H1604 + C4H5NO4.
By boiling with peroxide of lead, hippuric acid is converted into benzamide (634), carbonic acid and water being formed at the same time.
The action of nitrous acid upon the hippuric, results in the production
of a new acid, called the benzoglycollic, which has the formula, C36Hl60,6;
water and nitrogen being eliminated. Glycocoll acted on by nitrous acid
forms glycocollic acid, Cis-80il.
QUrESTIoNs.-Describe the process of obtaining hippuric acid. When
it is boiled with a strong acid, what compounds are formed from it?




AP P E N DIX.
Tables of Weights and Measures, Proportion of Alcohol ir
Spirits of different Specific Gravities, etc.
WEIGHTS.
English Imperial Standard Troy Weight.
24 Grains       = 1 Pennyweight.
20 Pennyweights = 1 Ounce = 480 Grains.
12 Ounces       = 1 Pound = 5760 Grains.
Apothecaries' Weight.
20 Grains  - 1 Scruple D.
3 Scruples = 1 Drachm 5.
8 Drachms = 1 Ounce 5 = 480 Grains.
12 Ounces  = 1 Pound = 5760 Grains.
The Grain, Ounce, and Pound are the same in both the above weights.
Avoidupois Weight.
1 Drachm  = 27'34 Grains.
16 Drachms = I Ounce = 437'5 Grains.
16 Ounces  = 1 Pound = 7000 Grains.
28 Pounds  -1 Quarter.
4 Quarters = 1 Cwt. or 112 lbs.
20 Cwt.    = 1 Ton.
-Flrench Decimal Weights.
Gramme       = 15'443 Grains.       Gramme        -                  15'443 Grains,
Decigramme  -  1'544        Decagramme  -   10 Grammes = 154'43,c
Centigramme =  0'154   "            Ilectogramme =  100   "        = 1544-3  "c
Milligramme -  0015   "             Kilogramme  = 1000    "        = 15443'   "
The Itilogramme = 2'206 lbs. Avoid., and 2'68 lbs. Troy.
Troy weight is used in all cases in weighing the precious metals, the ounce being generally made the unit. Physicians, in making their prescriptions, and druggists, in compounding their medicines, make use of the subdivisions of the pound called Apothecaries'
weight; but drugs are always bought and sold by Avoirdupois weight.
In scientific researches, as in chemical analysis, and the determination of specific
gravities, either Troy weight or the French decimal system is used. When Troy weight
is used, the grain is made the unit.
MEASURES OF CAPACITY,
Wine or Apothecaries' lMfestlre.
60 Drops   = 1 Drachm 3.
8 Drachms = 1 Ounce O.
16 Ounces  = 1 Pint.
8 Pints   = 1 Gallon = 231 Cubic Inches.
The cubic inch of pure water at 620 weighs 252'458 grains, or 16'283 grammes.,
Fresnch Decimal Measure.
Litre    = 61'025 Cubic Inches.
Decilitre =  6'102     "
Centilitre =  0'610    "
Millilitre =  0'061    6
The Litre = 1056 quart wine measure.
EEASURES OF LENGTH..French Decimal System.
Metre     = 39'371 Inches.
Decimetre  =  3'937   "
Centimetre =.393  "
Millimetre =   039  "
The French Metre is one ten millionth part of the distance, upon the surface of the
earth, from the equator to either pole.
The Gramme (the unit of weight) is the weight of a cubic centimetre of pure water, at
its greatest density.                                                (515)




516                               APPENDIX.
TABLE  showing  the Specific  Gravity  of Liquids, at the  Temperature  of
550 Fahr., corresponding to the Degrees of Baumi's Hydrometer.
FOR LIQUIDS LIGHTER THAN WATER.
Deg. Sp. Gr.  Deg.   Sp. CGr. Deg.   Sp. CGr. Deg.   Sp. Gr'. Deg.    sp. CGr.
10 =  1-000     17  ='949      23  ='909     29  ='874       35  =   842
11'990     18'942     24'903    30'867     36'837
12'985     19'935    25'897     31'861     37      *832
13'977     20'928     26'892    32'856     38'827
14'970     21'922     27'886     33'852     39'822
15'963     22'915     28'880     34'847     40'817
16'955
FOR LIQUIDS HEAVIER THAN WATER.
Deg.,Sp. Gr. Deg.   Sp. Gr. Deg.   Sp. Gr. Deg.   Sp. Gr. Deg.   Sp. Gr.
0 =  1000    15        1-114    30  =  1-261    45  =  1-455    60  =  1717
3      1'020    18     1140    33      1-295   48       1-500    63      1-779
6     1-040    21      15170   36      1'333    51      1'547    66      1'848
9     1'064    24      1'200    39     1'373    54      1-594    69      1'920
12     1'089    27      1'230    42     1-414    57      1-659    72      2'000
TABLE showing the Quantity of Absolute Alcohol in (100 parts of) Spirits
of different Specific Gravities, at 600 Fahr., the spirits being supposed  to
contain nothing but pure alcohol and pure water.
ALCOHOL. SP. GRAVITY.  ALCOHOL.  SF. GRAVITY.  ALCOHOL. SF. GRAVITY.
100        0-796          66        0 881          32        0 955
99        0.798          65        0 883          31        0 957
98        0-801          64        0 886          30        0 958
97        0 804          63        0 889          29        0-960
96        0 807          62        0 891          28        096R2
95        0 809          61        0 893          27        0 963
94        0 812          60        0 896          26        0 965
93        0 815          59        0 898          25        0 967
92        0 817          58        0 900          24        0 968
91        0 820          57        0 002          23        0 970
90        0 822          56       0o904           22        0.972
89        0 825          55        0 906          21        0 973
88        0 827          54        0 908          20        0 974
87        0 830          53        0 910          19        0 975
86        0 832          52        0 912          18        0 977
85        0 835          51        0 915          17        0 978
84        0 838          50        0-917          16        0 979
83        0 840          49        0 920          15        0 981
82        0 843          48        0 922          14        0 982
81        0 846          47        0 924          13        0 984
80        0 848          46        0 926          12        0 986
79        0 851          45        0 928          11        0 987
78        0-853          44        0 930          10        0 988.77       0-855          43        0 933           9         0 989
76        0 857          42        0o935           8        0o990
75        0-860          41        0 937           7        0.991
74        0 863          40        0 939           6        0 992
73        0 865         39         0 941           5        0.993
72        0 867          38        0 943           4        0 994
71        0 870         37         0 945           3        0996
70        0 872         36         0 947           2        0 998
69        0 874         35         0 949          1         0999
68        0 875         34         0.951           0
67        0 879         33         0 953




INDEX.
PAGE
PAGE  Acid, chloric........................ 211
Acettdl..........,,,,,,,,..... 424       chlorous.....................  210
Acetamide.................. 480         choleic...................... 505
Acetone.......,..,.............. 427          cholic.........................  05
Acetonitriles........................   480   chromic,..,............. 358
Acids, coupled...................... 422      cinnamic..................... 451
defined,................... 153       citraconic................... 467
metallic.................... 347     citric.........................  467
vinic......................... 433     cobaltocyanic.........     490
Acid, acetic....................... 423       coumaric.                   454
acetous....................... 423     cyanic................ 481
acetonic..................... 459      cyanuric..................... 484
aconitic..................... 467      dialuric,..,,,. 513
adipic........... 49  ethli............. 461
aldehydic................, 423        ferric  i................5..  835
alloxanic.................,  13         oborac...
anisic.           452         fluosiliciC.................... 280
antimonic......         366         formi...............        428
arse*nic.~ 252  ~fumaric.                           468
arsenic.................... 252
arsenious251ic.................... 482
aspartic.......            479         gallic............ 469
auric............   388                 geic......   415
glycocollic.............    54..... 414
benzoglycocollic........... 514        hippuric......  13
benzoic....................... 448mic415
benzyi..humic..................... 4..   416
benzylic.......,,.. 449
boraci.          283          hydriodic,,.,   217
boracfm....................... 2
bromic..........  219                  hydrobromic................  219
butyric..............  359             hydrochloric.........      211
cacodylic.................... 475      hydrocyanic484
campholic.......,,. 454             hydroferrocyanic.,...... 487
camphoric.............., 454          hydroferridcyanic........ 488
capric....,,.,,       459         hydofluoric...2 21........ 221
caproic......,   w,. 459      hydrofuosilicic.....281
caprylic....               459         hydrosulphocyanic........ 485
carbolic,.,        451          hydrosulphuric......        234.... 234
carboni....,,,,.,,..,.,   263     hydrotelluric............... 241
cerotic......,,,,,,,,.,,.....   462.   hypochloric.,,,,..... 210
44                                                   (517)



518                                      I NDEX.
PAGE                                             PAGE
Acid, hypochlorous............. 210   Acid, propylic.....................  427
hyponitrous................. 199                Prussic..................          484
hypophosphoric............   245                pyrogallic................... 469
hyposulphuric.............. 225                 pyroligneous.......... 417, 424
hyposulphurous............ 225                  pyrophosphoric.                247
iodic.......................... 217      racemic...................... 467
iodous..........                 217            ricinoleic..................... 460
isotinic....................... 471             salicilic................e.......  450
isotartario.................. 467             salicilous..................... 450
itaconitic.......... 467                        sebacic.......................  459
lactic.......................... 511            selenic........................ 240
malic.......... 468           selenous......................     240
manganic................... 347                 silici...................... 279
margaric............... 456, 458                stannic....................... 363
melissic...................... 462              stearic...............  456, 457
meconic..........     469            suberic......................  459
metacetonic.............  427                 succinic...................... 459
metagallic................... 469               sulpharsenic.............. 253
metaphosphoric............ 247                  sulpharsenious............. 253
metatartaric................ 467                sulphethalic................  460
mucic.......... 411      sulphindigotic..........     477
muriatic..................... 211               sulphindylic................ 477
myronic...................   452                sulphocarbonic............  276
nitric......................... 200       sulphocyanic................  485
nitrous....................... 199              sulphoglyceric.............   457
oenanthylic.................. 459               sulphomethylic............. 4-41
oleic.....456, 458                              sulphovinic................. 435
oxalic.................   466                  sulphuric...................  228
oxamic.....................   440               sulphurous......                 225
palmitic......................  460             tannic........................ 468
paramaleic.................. 468                tartaric......................  466
paratartaric................. 467               telluric....................... 241
pectic........................ 411              tellurous.................... 41
pelargonic.......        459            umic..................... 415
perchloric............           211            uri........ 513
periodic....................  21                  leiic                              1
permanganic...........           348  Acroleine....................    457
phosphoric.................. 246  Affinity............................... 158
phosphorous................ 245   Agate....                      279
phosphoglyceric........ 457   Air, atmospheric.................. 1!)2
pimelic....................... 459            empyreal.......................       4
propionic..... 427          fixed..........2...6............. 263




INDEX.                                           519
PAGE                                             PAGE
Air, inflammable...................    181   Anhydrite........................... 335
vital.............,............... 174  Animal heat........................  511
Alabaster............................ 533    Anisene.............................. 452
Aldehyde......,................ 422  Anthracite...................258, 259
amylic................... 431   ANTIMONY.....................   365
Albite.........................   42  Aqua fortis.....................           201
Albumen............................. 492               regia......................213
Alcargen.....                           47    Achil........................ 477
Alcarsine...........                     475 Argol.466, + 
Archl..............................  467
Alcohol, acrylic...........              432 Arrowroot............407
amylic.................... 4I'2  AR'sENi.............................. 250
m2.ARSENs....... 250
butyric...........402, 403............259
caprylic.                    460 Asparagine..........................471, 479
cerotic................. 462    s lt.sum...........................       416
Astatic needle.................          116
mIelssc...............  4625
bAtmosphere...............,    4 192
aethylic.................. 428  A sp            orie..
phenylic........       432, 450   At           theory150
sulphurAt.............................    14
lphwneur.......              418            specific heat of............. 151
wine....................... 418Attas tion n             ee de................  141
Algaroth, powder of............. 367                                                        14
Aiarsie.................437 Aurum  usivum......................... 364,A-lkali, volatile..................             A 20191
Allanite.............3................. 44
Allantoine...................            513
Allotropism......       157  Balloons......................   184
Alloxan.................., 513  B3alsam, Canada................. 463
Allosxantine........................  513             Peru....................... 451
Alum.................  341                                  Tolu................           451
Alumina............... 340  Ballistic pendulum......3......... 307
ALUMINUM n........3.............                    315
Amalgams........................... 376  BARIUM...............  328
Amber...                                 464 Baryta, barytes............ 2..... 328
Amides.............................., 478   Batteries, galvanic................  92
Ammelidel~~..f...........  486   Bees'-wax.......4...61.......... 461
Ammeline...48    Bell-metal.......3............. 372
Ammonia..................,  202   Benzamide.............      448
Ammonium......................... 319  Benzene..................... 449
Amylene........443..........;....   443    enzile...........................   449
Amygdaline......................    448   Benzoine................. 449
Amylamine473                                           ne.............................  449
Anatase.............................. 37    BERYLlUM......37    BRY............. 344
Anchor ice...................   29   Biliary calculi......................   505
Aniline...........................   473    Bile........................  05




520                                    INDEX,
PAGE                                          PAGE
Bisethyle............................. 474  Camplhor, Japan..45............ 453
BISMiUTH............................. 367      Borneo.................. 454
Black lead........................... 258  Cantharadine....................... 471
flux............................ 290  Caoutcho-Lc......                      464
Bleaching salt...................           Cprine............456  459
Blende................................ 359  Caproine.................6, 4..
Blonde.~~~~~  Caproine.~~~456, 459
Blood................5.............  501  Caramel..........................   409
Blowpipe.....................         273............ 0478
Caramiel.............................. 478
compound.........           187  Cartilage.................,... 498
CBoiling point.e....41CARBON.............................. 256, omolound Va...............~~,,,  187
Bologna vial.3......27  Cellulose............................ 412
Boines........................ 499Cement.3
~~~~~Borax~~CA                           n.....................3.16...............84
BoRonail.........................  328
Cerite..3...4.4................         41
CERIUM....344
Brain....4.................... 499.
~~~~Brandy                  421 ~~Cemien..............4...C....r......4 36
Brass.................................    372
Brozeline..               478  Chameleon mineral............... 347
BCharcoal.........................257, 260
BrickslC.................................  848
British..............     407  Cheese........................... 4511
Britandnia mefal...........366  Chemicaleqia..15..           5.....  41
BROMINE...18Chnawr............................  42
Bromoform.........4..........I.......    ChloantLite....36...4...............
Bronze................72 Choral.............                                        427
Brom, Brucine................471  Chalor ine............... 3
Brn         fluid............... 7... 4      Chloroform..............441..... 
iButter.......................... 45  Choro9ale.                                    478..........., 
Butyrine.......................456  459  Chokedap....................    5
Buty~~~~~~ronze,~...460 3         Cholesterine.........50...5.... 511
Butyronitarile........48... 0... 480  Chrome green.........3....                     59.... 5
B~ltn   fi,...,.,,                     ironl;........................   57
yellow.........3.........    59... 842
B~ ~ ~ ~~~~~~~~~~~iromoform...........,........42Coahie..................... 857
BCacodyle............................. 474  Chrysocolla.......................... 472
rCadet's fuming liquid...................   475  Chyloe.............................. 505
uCADrIUn........................ 362  Chlyme.....................              50.....   04
Caffeinel............................ 471  Cinchonia, ench e.....             470
Calamine........................359, 362  Cinnabaro......................... 3574
CALCIu M...........................  3 31  Cinnamene........................    451
Calcedony........................     279                                           451
yellow ~~~.~. ~~~~............ S5
CHRoMIV~..............,...,. ~....... 357
Cacodyle...........,.................. 474 Chrysocolla.......................... 372
Cadet's fuming ilniquid....,....... 475 Chyle.,...,........................... 505
Calomel.........3............. 36277  Clahyme........343................ 504
Caffeine,....,..,.....,.,..,.,.......... 471 Cinchoniat, cinchonine..........., 470
Calamine.............39     Cinnabar................  3 74
CALCIW~ ~~~...........................331 Cinnamene.....~.....,..,............. 451
Calcedony....,.,.......,............. 279 Cinnam~on...........,...,..........;... 451
Calomel............l......,........... 377 Clay...........................,..,..., 343
Camphene........................... 446  Classification of elements.......  172
Campholene........................  454  Cleavage............................. 169
Camphor, artificial............ 447  Cleavclandite................. 342




INDEX.                                        521
PAGE                                          PAGD
Clouds...............................  54  Derbyshire spar.................... 343
Coal....................... 257  Dew...................................  52
tar.................... 417  Dextrine.................... 407
COBALT...................... 251, 364  Diachylon............................ 463
Cochineal........... 478  Diallogite.................... 348
Codeine....................... 470  Diamond,....................... 258
Coke.................. 259  Diamagnet................... 112
Colcothar......................... 357  Diaspore................ 340
Collodion............... 414  Diastase................. 407
CoLUInBIUvM......................     374  DIDYMIUM.........................      344
Columbite................... 374  Dimorphism..................... 170
Combination, laws of............ 143  Dioptase............................. 373
Combustion..... 179  Dipping-needle................ 114
of iron..               174  Distillation........................    47
Compound bodies..          14  Drummond light................... 188
radicals...............  396  Dutch gold....................... 372
blowpipe............. 187                          E
Conjugated compounds..                 401    arths............................. 328
Copal..463                             alkaline....................  339
COPPER.n                                           E i..4..............1. 371        33l9o 41
pyrites....................372  Elaldehyde.....................  23
variegated..         72   lcricity......................  74
vitreous.................... 372                atmospheric...........  85
Copperas................    356                 conduction of.............  76
Corrosive sublimate............. 378                     distribution of........  80
Cotton............................... 413  induction of..........  78
gun.......................... 414          nature of............  74
Coumarine............. 454                thermo............  85
Coupled compounds........... 401                          of chemical action...  87
Cream..................... 510                theories of...........   74
of tartar............. 467                 sources of....8.....    81
Creosote.............................. 417  Electrodes...........  92
Cryolite.........................    339  Electro-magnet..125
Cryophorus........................  49 Electro-magnetic engine........ 127
Crystalography................ 158                      telegraph..... 133
Cupel................................. 382  Electrometer......................  76
Curd...................... 511  Electro-metallurgy.............. 109
Cyamelide........................... 484  Eilectrophorus................   84
Cyamethene.........................   482  Electrotype........................ 109
Cyanogen................... 275 Elements.........    1,37
classification of........ 172
D                                                               340
~~~~D  ~Emery.......................... 340
Daguerreotype........ 72 Empyreal air................... 174
De la   ive's ring................... 119  Emulsion.....................    448
44 *




522                            INDEX.
PAGE                                 PAGE
Enamel................................. 324 Ether, hydrochloric amylic...... 444
Engine, electro-magnetic........ 127      hydrosulphuric amylic... 444
Epsom salt......................... 338   oxalic amylic.............. 444
ERBIUMr................... 344 Ethylamine.                          472
Ethal............................. 456, 451 Ethylammonium................... 472
Ethers.. 433 Eudiometers........................ 193
hydrobromic............... 438 Eupione.............................. 417
hydrochloric............... 437 Evaporation........................ 44
sulphuric........433, 434, 438 Expansion of gases..............  22
Ether, acetic.....................  439          liquids......       21
amylic....................... 443          solids............. 19
benzoic......................  449
butyric......................  459F
Fats,.fi........................ 455
carbonic..4.05 439
Fe cula................................ 405
cyanic.......................  482
Feldspar.............................  342
foyrmic....................  484  Fermentation, acetic............. 423
butyri............ 460
hydriodic.438                              butyi... 4i0
f...........vinous............. 418
hydrocyanic............... 411
hydrosulphuric...       438......... 438
Fiine....................yine in......  491
byponitrous....4......... 438.
methylic.................... 440  Fire-damp.............267, 415
nitric...................... 439  syringe................... 60
Fixed air.................... 263
osxalic.................... 440
oilspar......................... 455
salicylic.... 45...1   oils..          455 451
sebaci................... 459
Silicic....................  Fint            239
hySoicmtyl.42FLrOmNEezin...omxue................. 220
stearic                          O....................220  333
wood.          440,  Fluor-spar.~220, 333
F1UX~ blZ1C       AC...  9........  290
acetic mtylic. ethy...443          black..
benzoic methylic..........,  4492
hydriodic methylic...... 442100.. 4 Freezing mi.............    38
hydrobromic methylic..  442  Freezing mixtures........
sulpharc.   l......point.....s.................  21
hydrochloric methylic... 441          oi..
Fusel oil.,...............    430
hydrosulphuric methylic 442
nitric methylic............ 442               G
oxalic methylic........... 443  Gadolinate..................  344
shlicylic methylic......... 451  Galena............................  368
stearic methylic........... 458  Galvanoscope................. 117, 121
sulphuric methylic....... 443  Galvanic batteries................ 92
acetic amylic............... 444 Galvanometer................ 87
hydriodic amylic.......... 444  Gastric juice....................... 504




IND E X.                               523
PAGE                                   PAGS
Geine................................ 415  IHeat, specific......................  58
Gelatine..................   498          ta             f...........   35
G      erman,              65 Heavy spari.......................... 330
Germaan silver.............. 365 Heavy spar............ 330
Germination of seeds.......... 494  Hematite................   349
Gibbsite.............           340  Hematosile.5,  0
Gin....................................   421    Hematoxyline.............   478
Hematoxyline...4................... 478
Glass...................        322  Hepar sulphuris............. 30
Glauber's salt..............   34  Homologous bodies..............  401
Glucina...............      4Honey............................   409
GLUCINUBI34  s.....................                                  50044
Glucose..,          409,,,,,,,,,,,,.,. 409
Glue    4 9.......8........... 40           quicklsilver............... 378
Glue ten......................492          silver................ 384
Glycerine...........................  4   Humus..................,   415
Gly1COCOlln.................. 498  Hydragetbhyle.............  474
G-OLD.n...386  Hydrates.............................  198
Glrphite..............................                                  52181
Green,.........  255    ygroetrs.......................52
verditer..................377
Gi enockite.                    362
G-uano.......................... 8*2  Iceland spier......51.........   334
Guano................................    912
Gnm Arabic.411  Illuminating gas..... 2......... 269
elastic.........................   464  India rubberhy....................... 464
oSenegal                   411  IndigoL.................................  476
tragacant.0............... 411  Indigotine.......................... 4 6
Gnan cotton..     oeepeh***eeo414  pInflammable air.................... 181
pode........................30   Ink...ndelible             85
Gutta pech................... 463   sympathetic.................64
Grnotus   eletris................ iting468
Gynum elect.ic-L......   101 IODIN................    215
HIoDIUf...........................    442
Muail..................................   5 42   -cOn.........................,..
GHaArthi..........................2
I                     uairg s.. 5................. 222
Heart orn ti............202  Isin............. 471
Hleat, absorption of.  si3l4ss I                 ~iirgli5...  499
animal......      08  Isomerism..................       157
capacity for................   8  Isomorpism...................... 159
conduction of..........  29
convection of.....         3J..... 32
jet...................................   259
nature ofi....................  17
radiaion of..............    33                   K
reflection of............        aolin..........................  342
relative....  58  Kermes mineral............... 867
sources of,......  17  Ki.ng's yellow.. 2........... 253




524 -                                      INDEX.
PAGE                                               PAGE
L                           MAGNESIUM......................... 337
Lac.................................... 463   Magnesite........................... 338
Lactine......................... 410, 510   Magnet.......................... 111
Lakes...................... 476                 electro..................... 125
Lampblack...................... 261   Magnetic induction............... 113
LANTHANUM......................... 844            neele................
needle................... 114
Laughing gas....................... 196
Laughing gas.         196 Magnetism of earth............... 126
La:ws of combination............. 143                             terrestrial.114
LEAD................................... 1382
Magneto-electric machine....... 132
extract of..................... 426   Malachite...........................   73
sugar of....................... 424   Ma79
Leather........  4......... 469,  499   MANGANESE.....................   345
Leaven.............................   418410
Lecanorine.......................... 47710
Ma~Snnite............................410
Legumine............................  43                                                    49
MaI~nnures,,,,.....................
Leocome.407                                                                                   334
Marble............................... 884
Lepidolite........................... 818
Lepidolite.318.................. 485   Marcet's apparatus...............   43
Letheon.............................   7985. B  458
Light de copoitinon....Margarine.....................456,  458
cdouble refraMction of................. 73........ 48
nature of....................   60   Melams..................6............ 4869
refibaction  of.............       65
~reflection of....      65 Melissine462
double refaction of...... 7
theories of...........          Mercaptan..                                 432
Mela      tin e............................   482
refraction    of...............   65
Lightning rods.....................   85   MMercaptine......................... 432
Lignine.............     4....... 413      ac............ 374
inite........                             259        etcetone..................  427
Lime3 1o........................         M1  etaldeyde................    423
Liimestone.................               33.. 4   Metalepsy.........................  400
Liquefaction  of gases.............   54  MIetallurgy, electro............. 109
Litharge....3.................,  370   Metamylene...................... 443
Lithia............................. 318   Metl.ylal.......................... 430
LITHIUM.....Metbylamine................... 472
Litmus..............              477    il...................   10
Live  of sulphur...................,  304                 sugar of..........    410
Loadstone......................111,               Mieral, chameleon..............  347
Logwoo.............................en....................   73
Lunar caustic.......................385                        pitch..................... 416
Lymph.............                        510       inil...................... 
h.................. 8............... 7 0
M                           Molasses.....................4.., 408
adder........................... 47                  olybdenite.......373
Maigic circle........................ 125  MOLYBDENUM...................... 373




INDEX.                                             5 25
PAGE                                               PAGE3
NIonasite............................. 344  Oil of winter green................  451
Mordants..................... 476   Oil, castor........................... 460
Morphia, Morphine..............    469                  fusel.................... 430
Mortar............... 333   Oleine..................... 456
Mosaic gold........................ 364   Opium................................ 469
Muscles........   498   Orcine...............................   477
M'yricine.............................   461   Organic bodies............   393
hMyrosine............................ 452   Orpiment............................  253
Myrtle wax....................... 461   Orthite......3... 344
N                           OSMIUM.............................    391
Oxamide....................... 440
N          aphtha........................ 416
Naphthalene417   OXYGEN.......................... 174
Napht halene........0....    417
Naphthaline........................ 417                                   P
Narcotine........................ 470   PALLADIU..........................
*XX@ PAL;ADIUM.,,..,..I..,,,,.....       e392
Nascent state....................... 205 Palmatine........................ 460
Natron..............................   19   Pancreatic juice...............    505
NICKEL............................... 365
Paracyanogen...................... 481
Nicotine..............................470   Paraffine 47017
Paramiylne......................... 414
Nitre...................3..........   05
Nitriles~~~..480 Paramylene......... 443
NiTEOGEN.~0~~~~~~.~II  194 Paris green..................., 373
Pearlash...............  304
Nomenclature...................... 151
Nutgalls.............................                               415
Pectine.....t...o  5.......8 Pc....... 411
Nutrition............................. 508
PELOPIUi M........................ 374
0                           Pendulum, ballistic............... 307
Ohm's formula:..................... 100   Pepsine......................... 504
Oil of aniseed...................... 452   Petalite............................... 342
bitter almonds.............. 448   Petroleum........................... 416
cinnamon...............    451   Pewter............................... 369
cumin..................... 452   Phenol......450  417
cloves................. 452   PHosPHo          Us........................ 241
elemi.......................... 447   Photography.............   70
garlic....... 453   Photometers...................   63
juniper....................... 447  Picrotoxine....................... 471
lemons................ 447   Pinchbeck.......................... 374
mustard, black........... 452   Piperine................... 471
pepper..............,  447   Pitchblende....................... 374
peppermint......4.......   52   Plasters..................  463
pimento................ 452   Plaster of Paris.................... 334
spirisea ulmaria.............    450   PLATINUM............................ 389
turpentine...................  446   Plumbago.................258, 356
vitriol...................... 228   Polynierism.................... 157




526                                  INDEX.
PAGE                                          PAGE
Porcelain............................  342  Ruby.............................., 340
Potassa, Potash............. 301 Rum.......421
PoTAssIUM.....................  298  Rupert's drops................ 327
Potato oil.................... 430  RUTHENIIUrM............... 392
Propione.................... 427  Rutile......................... 373
Prussian blue.............. 489
Ptyalie............................ 504                          S
Pulse glass..........................    50  Safety lamp......................... 270
Purple of Cassius.............. 389  Sago.................................. 407
Purpurine........................... 477  Salseratus...........................   305
Pyroacetic spirit.............. 427  Sal-ammoniac...8................ 321
Pyrochlore..........................  344      mirabile........................, 314
Pyrolusite.................. 347        soda...............................15
Pyrometer....................  27   volatile....................... 321
Pyroxylic spirit..............417, 428  Salt, common........ 312
Pyroxyline.......................... 414
Epsom......................... 338
Q                              Glauber's.............3....... 814
Quartz...............                microcosmic............          32
rock............................. 312
Quercitrine........................... 478
Quicklime..........3................ c31  Salicine............................  450
A  Saliva         i..............................0   504
Quicksilver -................... 3 74
Sa ndara.............................  464
Quinia, Quinine....................   47464
Sapphire............................. 340
R                        Scheele's green................255, 373
Rain.....................   54  Sealing-wax.................. 464
Rats-bane.......................... 251  Selenite.............................. 335
Realgar............................. 253  SELENXUM..................... 239
Red lead.............8... 370  Seneca oil...................... 416
precipitate............. 377  Shells................................. 500
Prussiate of potash........  488  Silica................................ 279
Register thermometer............  25  SILICON.................... 278
Repulsion...................   13  Silurus electricus............... 101
Resin.................... 463  SILVER..............................  381
Respiration of animals........... 506  Smalt,.................  364
plants............ 495  Smaltine.......................... 364
RHODI    n..............  392  Soap........................456, 462
Rocelinine......................... 477  Soda................................ 311
Rochelle salt...................      467         ash..................... 315
Rock candy........... 408            fountains..................... 265
Rock oil.................... 466  SODIUI............................... 310
Rosin................................. 463  Solder................................ 369
Rotation of crops.................. 497            hard...3................ 372




INDEX.                                       527
PAGE                                        PAGE
Solar  pectrum.....................  63  Sulphoform......................  442
Soluble glass........................ 280  SUrLPHUR.......................   222
Spathic iron........................ 356             springs............... 285
Specific gravity of atoms........  151  Symbols.............................. 155
Specular iron...8.............. 349  Synaptase.......................... 448
Speculum  metal......... 372  Sympathetic ink...............  364
Spelter............................... 360
Spermaceti.......................... 460                 T
Spheroidal state of liquids......  51
Spinelle.............................. 340  Tallow, bayberry.......461
Spirit of hartshorn.....              202  Tangential force........... 114
Sph'it of hartshorn................ 202  Tannin............................... 
Mindererus.............. 426  Tantalite.............................74
turpentine............... 446
st.......2     TANTALUM.......................... 374
sal                              Tapoca........................211407
Wine....................... 420  Tpioa.......................... 4.... ine.....................318420  cTar...........................    463
Spirit-lamp.......................... 421
coal........................0... 417
Spodumeme....................18, 3424
Tartar..............   466
Springs, sulphur........... 235   cream of.    eO 467
Stalactites.............e.. 334.4
em etic...................... 407
Stalagmites.......................... 334.Stalagmites............   Telegraph, electro-magnetic..... 133
Stanethyle.....TELLRIUM............ 474                                    240
Starch.............................. 405  TERBIUM............................. 344
Steam... Terrestrial magnetism............ 114
Stearine.............................. 456  Theine............................ 471
Stearoptens......................... 446  Thermography.73
Steel.................................. 353  Thermometers......................  22
Stereotype plates.................. 335  Th............... 344
Stibethyle......                     474  Thorite........................   344
Stibium.....................365T                                                 344
Stibium.............................. 365  TORIUM.....I..................... 344
Strichnia, Strichnine...........  471  TIN........................... 272
Strontia.................... 330  Tincal.......3........................ 816
STRONTIUM.........................   330  TITANIUM............................ 7 83 
Styrax........................... 451  Tomba.......................     72
Styrole.................... 451  Tonka bean........................,-)4
Substitution............    400  Torpedo......................  101, 4,4J
Sugar, barley....................... 408  Treacle..............................   409
cane........................  408  Trona..................,        15
diabetic..............  409  Troostite...........................  373
grape................... 409  TUNGSTEN...........................   73
milk..................  410  Turmeric root................  47S
of lead....       425  Turnbull's blue................  4]89)
of sour fruits........... 410  Turpentine, spirits of...........  646




528                                         INDEX.
PAGE                                                  PAG5R
rurpentine, oil of.............. 446                                        W
Turpeth, mineral..................  380   Water..............................  185
Turnsol.........,.............,   477             constitutional............... 296
Type metal.......................... 369                    of crystalization.....159, 296
lime........................... 331
Wax, bees'.,..................,. 461
myrtle........................ 461
Ulmine...............................  415   Whiskey.............................  421
Upas................................. 471   White lead...................... 376G
Uranite............................... 374   Witherite............................ 329
URANIUM..................         374   Wine.................................. 466
Urea.............................482, 512   Wolfram.............................. 373
Urine................................. 512   Woody fibre......................... 413
Wood................................. 411
Wood naphtha.................... 428
V                                     spirit...................... 428
Valeronitrile......,.......... 4.........24
VANADIUM.......................   373                            X
Vaporization................ 40            in..414
Verditer, green..................... 377 
Vermillion...........380............... 18
Vinegar.........................  423            chrome..............               359
Vinous fermentation..,                      418               king's.............. 253
Viscous  L'..............   511   YTTRIUM.........................              344
Vital air....................... 174
Vitality.....................14, 394                                  Z
Vitriol, blue........................ 373   Zaffre.............,,   364
green..................           35    Z..........              359
white..................... 361   Zincethyle........................... 474
oil of........................ 228   Zircon................................     344
Volatile alkali....................... 202   ZIRCONIUM......................... 344
Voltaic pile...................   92   Zirconia.......,,...................... 344
THE END.