Cornell University Library TD 380.M41 Examination of water, chemical and bacte 3 1924 004 249 052 BOUGHT WITH THE INCOME PROM THE SAGE ENDOWMENT FUND THE GIFT OF Henrg M. Sage 1S91 M^nt^A i'jImIis. The original of tliis book is in tlie Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924004249052 WORKS OF PROF. W. P. MASON FUBLISHEU BY JOHN WILEY & SONS. Water-supply, (Considered principally from a Sani- tary Standpoint.) Third Edition, Rewritten. Svo, vil + 448 pages, 49 figures, 26 half-tone plates. Cloth, $4.00. Examination of Water : Chemical and Bacterio- logical. Fourth Edition, Revised. I2ino,vi + iSo pages. Cloth, f 1.25, EXAMINATION OF WATER CHEMICAL AND BACTERIOLOGICAL WILLIAM P. MASON, PaoriSBoR or Chehistky, Renbsel^sh Polttechhio Institute ; Memher of the American Philosophical Society, the American Chemical Society, the American Public Health Association, the Royal Sanitary Inatitide (Oreat Britain) , Honorary Member Association Qinerale des Ing&nieurs Architectes etJIygiinistes Municipaux, the American Society of Civil Engineers^ the American Water-Works Association, the Washington Academy of Sciences, the New England Water-Works Association, the Amer- ican Institute Chemical Engi- neers, the Franklin Institute, etc., etc. FOURTH EDITION, REVISED. SECOND THOUSAND,. NEW YORK : JOHN WILEY & SONS. hosDOv: CHAPMAN & HALL, Limitbo. 1913 Copyright, 1899, 1901, 1906, 1909, BT WILLIA.U F. HAS ON. THE SCIENTIFIC PREBS ■OBKBT DRUMMOND ANI^ COMPANY BROOKLVN, N* V, PREFACE. Knowledge of ordinary quantitative analysis is here necessarily assumed; therefore the merest sug- gestions are given for determination of the mineral matters present in a water, while the items properly lying within the scope of a sanitary examination are dealt with more at length. Upon the bacteriological side, only so much is touched upon as has been demonstrated to be of real service to the water-examiner; leaving the great field of ultimate differentiation to be further explored, and rendered still more practically useful, by the professed bacteriologist. Especial effort has been made to place the analytical methods in harmony with the recommendations of the American Public Health Association. Rensselaer Polytechnic Institute, Tboy, N. Y. November, 1909. CONTENTS. CHAPTER I. PAOB Inthoductort 1 Popular Misconception as to the Character of Water Analysis. A Knowledge of the Source of the Sample Necessary to Proper Interpretation of Analytical Results. CHAPTER II. Chemical Examination of Water Directions for Sampling. Method of stating Analytieal Results. Special Laboratory Required. Turbidity. Odor. Taste. Temperature. Reaction. Color as to Ana- lytical " Standards." Total Solids. Loss on Ignition. Hardness. Chlorine. Nitrites. Nitrates. Organic Mat- ter. PVee Ammonia. Albuminoid Ammonia. " Required Oxygen." Lead. Copper. Iron. Zinc. Arsenic. Chro- mium. Alum. Phosphates. Analysis of Mineral Residue. Manganese. Dissolved Gases. " Putrescibility." Con- version of " Parts per Million " into Grains per U. S. Gallon. CHAPTER III. Bacteriological Examination of Water 119 Preparation of Media. Bouillon. Nutrient Gelatin. Sugar Media. Agar-agar. Nitrate Solution. Dunham's Solution. Sterilizing. Sampling. Sowing Media. In- r CONTENTS. FASE cubating. Counting Colonies. Gas-forming Bacteria. Test for Bacillus Coli communis. DiflSculty of Detecting Bacillus typhosus. Diagnostic Value.of the " Colon Group." Great Cold not Fatal to Bacteria. Enumeration of Or- ganisms not Bacterial. Appendix A: Inteepeetation op a Watee-examination 159 Appendix B: Method op Tbeatinq Oysters fob B. Coli 171 EXAMINATION OF WATER CHAPTER I. INTRODUCTORY. A GREAT deal of popular misconception exists upon the subject of the analysis of potable water, and it is commonly supposed that such an examination may be looked upon from practically the same point of view as the analysis of an iron ore. That this belief is founded on fallacy may, however, be readily shown. When an iron ore is submitted for analysis the chem- ist determines and reports upon the percentages of iron, phosphorus, sulphur, etc., found therein; and at that point his duties usually cease, inasmuch as the ironmaster is ordinarily capable of interpreting the analysis for himself. Even should the analyst be called upon f&r an opinion as to the quality of the ore, the well-known properties of the several constituents make such a, task an easy one, and, assuming the 2 EXAMINATION OF WATER. sample to have been fairly selected, the opinion may be written without any inquiry as to the nature of the local surroundings of the spot whence the ore was taken. A water-analysis, on the other hand, is really not an analysis at all, properly so called, but is a series of experiments undertaken with a view to assist the judgment in determining the potability of the supply. The methods of conducting these experiments are largely influenced by the individual preferences of the analyst, and are far from being uniform or always capable of comparison, thus often introducing ele- ments of confusion where two or more chemists are employed to analyze the same water. Some of the substances reported — "albuminoid ammonia," for in- stance — do not exist ready formed in the water at all, and are but the imperfect experimental measures of the objectionable organic constituents, which our present lack of knowledge prevents our estimating directly. Thus the niimerical results of a water-analysis are not only unintelligible to the general public, but are not always capable of interpretation by a chemist unless he be acquainted' with the surroundings of the spot whence the sample was drawn, and be posted as to the analytical methods employed. It wa§ formerly very common for water to be sent for INTRODUCTORY. 3 analysis, with the request that an opinion be returned as to its suitability for potable uses, while at the same time all information as to its source was not only unfurnished, but was intentionally withheld, with a view of render- ing the desired report unprejudiced in character. Such action is not only a reflection upon thie moral quality of the chemist, but it seriously hampers him in his efforts to formulate an opinion from the analyti- cal results. For. instance, a large quantity of common salt is a cause for suspicion when found in drinking-water, not because of any poisonous property attaching to the salt itself, but because it is usually difficult to ex- plain its presence in quantity except upon the sup- position of the infiltration of sewage. Thus an amount of salt sufficient to condemn the water from a shallow well in the Hudson valley could be passed as unobjectionable if found in a deep- well water from near Syracuse, N. Y. The writer once saw the contents of an ice-cream freezer dumped within a few feet of the mouth of a domestic well. So large an amount of salt thrown upon the ground naturally increased the quantity of chlorine in the water, and might have led to the con- demnation of the well had not the source of the chlorine been known. Hence we see how .'mportant it is for the chemist 4 EXAMINATION OP WATER. to be fully acquainted with the history of the water he is to examine in order that he may compare his results in "chlorine" with the "normal chlorine" of the section whence the sample is taken. A knowledge of the history of the water is no less important in order to interpret the remaining items of a water-analysis. Some time since, a water was sent from Florida to the author for examination, and was found to contain 1.18 parts "free ammonia" per million. Much "free ammonia" commonly points to contamination from animal sources, and had it not been known that the water in question was derived from the melting of artificial ice made by the am- monia process, the enormous quantity of ammonia found would have condemned it beyond a peradven- ture. As it was, the water was pronounced pure, the other items of the analysis having been found unob- jectionable. Analytical results which would condemn a surface- water may be unobjectionable for water from an artesian well, for the reason that in the latter case high figures in "free ammonia," "chlorine," or "nitrates" are often capable of an explanation other than that of sewage-infiltration. Even though such a water should, at a previous period, have come in contact with objectionable organic waste material, yet the in- tervening length of time and great distance of under- INTRODUCTORY. S ground flow would probably have furnished abundant opportunity for thorough purification. "Deep" samples taken from the same lake, at the same spot and depth, will vary greatly in anailytical results if the temperature of the water at the several dates of sampling should be markedly different, ow- ing to the disturbing influence of vertical currents. Again, suppose it is desired to determine whether or not the water of a river is so contaminated with up- stream sewage as to be unfit for a town supply. A single analysis of the water taken from the site of the proposed intake would very possibly be valueless. Examinations of any real value in such cases should always be of a comparative nature, and should extend over sufficient time to embrace seasonal and other changes common to such sources. Thus it is that a chemist must be in full possession of all the facts concerning the water which he is asked to examine, in order that his opinion as to its purity may be based upon the entire breadth of his past ex- perience, for in no branch of chemical work are ex- perience and good judgment better exercised than in the interpretation of a water-analysis. , A case such as this might arise: A water is con- demned because of high chlorine. It is completely stejilized by perfect filtration. After such filtration it contains as much chlorine as before but is then 6 EXAMINATION OF WATER. pronounced as safely potable. Note how important it would be to possess a knowledge of the history of the water in such an instance. As Nichols has well said, "It is a great mistake to suppose that the proper way to consult a chemist is to send a sample of water in a sealed vessel with no hint as to its source. On the contrary, the chemist should know as much as possible as to the history and source of the water, and, if possible, should take the sample himself." However faithfully the various laboratory tests may be applied to decide the question of the fitness or un- fitness of a certain water for dietetic purposes, there is nothing upon which greater stress should be laid than a thorough personal knowledge of the surroundings of the source of supply. In other words, it is essential to make a careful and thorough "sanitary survey." It was years ago laid down as a golden rule "never to pass judgment upon a water the history of which is not thoroughly known," and the nearer this maxim is lived up to to-day the fewer will be the mistakes in the reports issued. A water analysis is, for purposes of economy, rarely made complete. For ordinary drinking water the question is always asked " is it wholesome? " To answer tliis the analysis of the mineral residue left upon evap- oration is not usually required, so that much time and expense may be saved by simply reporting this as INTRODUCTORY. 7 "total solids." On the other hand, analyses of mineral waters deal with this feature of the examination very largely, and usually to the exclusion of those portions, such as "albuminoid ammonia," "required oxygen," etc., which are important in the sanitary analysis. The same may be said of the analyses of waters for boiler use. As it is to be regretted that many waters are analyzed and reported upon by those who know nothing of the sources whence the samples are derived, it is refresh- ing to note that at least one State laboratory is not disposed to encourage such practice : "Since July, 1904, endeavor has been made to dis- courage as much as possible the sending of promis- cuous samples of water to the laboratory by physicians or others in the State. It is considered necessary to do this for several reasons : " 1 . The analytical data obtained from such exam- ination are of Httle value to the person for whom it is made. "2. The analytical data are of even more doubtful value to the Board of Health. It is so easy to con- taminate by careless handling absolutely clean water bottles that the usual condition and character of con- tainers used for miscellaneous samples cause serious suspicion that the water sent is not truly repre- sentative of its source. For samples of this kind, 8 EXAMINATION OF WATER. greasy milk bottles, fruit jars with sticky rubber bands, medicine vials sealed with wax, etc., are often used; it transpires later that the samples were not properly taken to represient the true condition of the water; and several days often intervene before the sample is received at the laboratory, during which time it has had opportunity to change in essential features. Briefly, the laborious chemical analysis of water not secured in the proper manner is injudicious and wasteful of time and money. " 3. It is absolutely impossible to gain insight into the bacteriological character of such saifiples. The bacteriological examination, which is of so much impor- tance in passing judgment on a water, must necessarily be commenced at the time of collection by a trained laboratory assistant in order to be of value." CHAPTER II. CHEMICAL EXAMINATION OF WATER. DIRECTIONS FOR TAKING A WATER-SAMPLE, One-gallon glass-stoppered bottles are to be used for sampling. They should be most carefully cleaned, their stoppers tied down with cloth, and then sterilized. Upon being taken to the field they should be rinsed with the water to be sampled. Do not attempt to scour the interior of the neck by rubbing with either fingers or cloth. After thorough rinsing, fill the vessel to overflowing so as to displace the air, and then com- pletely empty it. If the water is to be taken from a tap, let enough run to waste to empty the local lateral before sam- pling; if from a pump, pump enough to empty all the pump connections; if from a stream or lake, take the sample well out from the shore, and sink the stoppered sampling-vessel towards mid-depth before removing the stopper, so as to avoid both surface scum and bottom mud. In every case fill the vessel nearly full, leaving but a small space to allow for possible expansion, and 9 XO EXAMINATION OF WATER. close securely. Under no circumstances place sealing- wax upon the stopper, but tie a piece of cloth firmly over the neck to hold the stopper in place. The ends of the string may be afterwards sealed if necessary. Stoneware jugs are not admissible for collecting water-samples. They are hard to clean and some of the salt used for glazing may remain in the interior. Bear in mind, throughout, that water-analysis deals with material present in very minute quantity, and that the least carelessness in collecting the sample must vitiate the results. Note the date of taking, the sample, and as full a description as possible of the soil through or over which the water flows, together with the immediate sources of possible contamination. Sketch the surroundings of the place of collection and give approximate distances of houses, privies, bams, and fertilized land, noting the general character and topography of the local watershed. Having secured the sample, the analysis should be begun at once, for the reason that water is liable to rapid changes in character during laboratory storage. For instance, the following analyses are of the same sample of water from the laboratory tap, drawn November 10, and allowed to stand in the sampling- bottle at ordinary room temperature: CHEMiCAL EXAMINATION OF WATER. II Nov. 10 Nov 12 Nov. 13 1 Nov. 14 Nov. 15 Dec. 15 Free ammonia Albuminoid ammonia Chlorine 0.037 • 0.220 4.5 trace 0.50 4.35 140. 0.042 0.178 0.42 0.19: 0.050 0.175 0.075 0.155 0.060 0.205 N in nitrites N in nitrates Required oxygen. . . . Total solids trace 0.525 4.6 trace 0.55 4.2 trace 0.60 4.4 trace 0.60 4.1 none 0.60 4.6 This water shows gradual oxidation of the nitrogen contents to nitrates, but on the whole is fairly stable. As showing, on the other hand, how rapid and how irregular the storage changes may at times be, the following analyses by Liversidge are given:* Horse-pond Fish- pond,- Peaty Water. - '3 - = 9 < .S il- ls y < December 11 10.00 2.00 8.00 7.00 6.00 5.00 4.00 2.00 0.50 0.07 7.00 2.00 4.00 4.00 2.00 2.00 1.00 0.50 0.25 0.07 0.12 0.11 0.16 0.16 0.38 0.52 0.70 0.90 1.38 1.50 0.90 0.92 1.04 1.03 0.69 0.56 0.38 0.30 0.06 0.04 0.72 1.12 1.12 1.08 0.03 0.02 0.01 0.19 12 04 " 13 13 " 15 12 " 16 04 " 19 03 20 i " 21 0.01 "10 These are, of course, exaggerated cases containing high ammonias, but they serve to point out the neces- * Chem. News, Ixxi. 249. 12 EXAMINATION OF WATER. sity of avoiding delay between the collection of the sample and the beginning of the analysis. At the most, very few days should intervene. Hitherto no small confusion has existed, on ac- count of the many ways in which the results of water- analyses were stated, but this difficulty, it is to be hoped, will be done away with by the general ac- ceptance of the method now widely recommended that all results be given in parts per million in weight. This method has the advantage that a litre, or fraction thereof, of water having been operated upon, and the substances found having been determined in milli- grammes, no long arithmetical calculations will be re- quired. Of course the assumption is made that a litre of water weighs a kilogramme — a true enough state- ment for potable waters, but one capable of introduc- ing error where mineral waters are dealt with whose specific gravities are appreciably above unity. In such a case the water to be analyzed is actually weighed, or else its weight is estimated from, the known specific gravity and volume. Water should not be filtered before analysis. If sediment be present, it should be equally distributed by thorough shaking before measuring. CHEMICAL EXAMINATION OF WATER. 13 The reason for this is that a water-analysis should represent the water as the consumer uses it, and not in a condition improved by filtration. Water-analysis cannot be conducted in a general laboratory, because many of the tests would be ruined by the fumes common to such a locality. TURBIDITY. Turbidity was formerl)'^ reported in words, not figures. In order to express it in parts per million, the writer some years ago suggested the use of a standard suspen- sion made by adding one gramme of exceedingly fine kaolin (obtained by eleutriation) to one litre of distilled water. Each c.c. of this preparation will contain one milligramme of suspended clay. Whipple and Jackson improved this standard by substituting fine diatomaceous earth for the kaolin and in that form it is used to-day.* The earth is ignited, ground, passed through a 200 mesh sieve and weighed. One gramme being suspended in one litre of water gives a turbidity of 1000. Suitable dilutions of this standard suspension are kept in bottles of the size used for water samples and a series of "turbidities" is thereby obtained ready for instant use. A few crystals of * The U. S. Geological Survey makes use of gear's Precipitated Fullers Earth. 14 EXAMINATION OF WATER. mercuric chloride are added to each bottle to prevent organic growths. Such a stock solution, as the above, when diluted with nine times its volume of water, will permit of a pla- tinum wire one millimetre in diameter being just visible at a depth of 100 millimetres below the water surface. A turbidity-rod, prepared for the U. S. Geological Survey and based upon the above standard, is very convenient for use in the field. The eye of the observer must be about 1.2 metres above the wire, and the reading should not be made in direct sunlight. The rod cannot be used for tur- bidities below seven. For turbidities over 500 the water should be diluted before the observation is made.* It must be noted that high color interferes with the use of the turbidity-rod. Thus the writer found that the water of the Black River at Georgetown, S. C, which showed a color of 162, gave a rod reading of 31, while its true turbidity was only five. Any quickly subsiding material present should be classed as "sediment" rather than "turbidity." To' determine the same it would be best to decant the water from above such deposit and then catch it upon a weighed filter or in a Gooch crucible. "Suspended" as distinguished from "dissolved" * See Circular 8, Div. of Hydrography. CHEMICAL EXAMINATION OF WATER. IS material may be determined by estimating the solids, as per page 23, both before and after passing the water Fig. 1. through a Berkefeld filter. The most convenient form of such filter is one illustrated in Fig. I. ODOR AND TASTE. It is customary to report such odor and taste as a water may possess, although in the great majority of cases very little information is derived from such examination, because of the frequency of negative results. A good water may be possessed of a slight marshy odor, while one of extemely dangerous char- acter may be limpid, tasteless, and odorless. The l6 EXAMINATION OF WATER. test is best applied both before and after heating the water nearly to the boihng-point, and after thorough shaking in each case. Both taste and odor are sometimes very pronounced, as when such organisms as "Asterionella" are present in quantity. Fortunately, disease has never been traced to such occurrence, however objectionable the water may be from an aesthetic standpoint. Organisms of this character are revealed by a miscroscopical examination. See page 155. TEMPERATURE. A cool water should, if possible, be supplied for public use, but studies of temperature are compara- tively rare, for the sufficient reason that questions of much greater weight determine the selection of a source of supply. The item of temperature is, however, well w:;rthy of consideration. No small economy in the matter of the ice bill will follow the introduction of a cold water in place of one equally pure but warmer. The advantage is especially noticeable in the poorer sections of a city. For comparison: in June 1906, with the atmospheric temperature at 76° F., the water of Troy as delivered to the consumer was 66° and required further chilling to make it acceptable to the taste. At the same time the deep well supply of Ithaca, N. Y., stood at 56° find was agreeable for drinking without more cooling. CHEMICAL EXAMINATION OF WATER. IJ The extreme variation of temperature for Croton water, as delivered by the street hydrants in New York City, for the year 1894, was: On February 24 34° F. On August 4 76° F. Should many temperature readings in deep water, as in a lake, be decided upon, no better device could be chosen for the work than the "thermophone," invented by Warren and Whipple. The following is clipped from a description issued by the makers, E. S. Ritchie & Sons, Brookhne, Mass. : "The thermophone is an electrical thermometer of the resistance type. It is based upon the principle that the resistance of an electrical conductor changes with its temperature, and that the rate of change is different for different metals. "The operation of taking a reading is as follows: Having connected the leading wires to the proper binding-posts of the indicator-box, the current is turned on and the telephone held to the ear. A buzz- ing sound in the telephone is found to increase or diminish according as the pointer is made to approach or recede from a certain section of the dial. By mov- ing it back and forth a position may be found where the telephone is silent. When at this point, the hand indicates the temperature of the distant coil. In- gtrunjents of ordinary atmospheric range, i.e., from l8 ■ EXAMINATION OF WATER. 15° to 115° F., may easily be read to 0.1° even by an inexperienced observer. With a smaller range, or with an instrument having a larger dial, a greater pre- cision may be obtained. "It is more sensitive than a mercurial or other expansion thermometer, because the rate of change of resistance per degree is greater than the rate of ex- pansion of liquids or soUds, and, moreover, slight changes in resistance may be more easily and ac- . curately measured than slight changes in length or volume. "It sets quicker than most mercurial thermome- ters. In obtaining the temperature of water of vari- ous depths one miiiute has been found to be sufficient time to allow for setting. "It is independent of pressure." * REACTION. The reaction of natural water is commonly slightly alkaline, although waters holding much free acid in solution, usually sulphuric, are by no means rare. * The deepest sounding found on the Challenger expedition was in lat. 11° 24' N., long. 143° 16' E. The depth was 4475 fathoms. Temperature of bottom-water 33.9° F. " surface-water 80° F. Most of the thermometers employed were crushed by the great pressure of five tons per square inch. More recently the still greater depth of 5269 fathoms has been recorded. See Engineering News, Nov, 22, 1900, CHEMICAL EXAMINATION OF WATER. IQ Determination of alkalinity. — Place 100 c.c. of the water in a casserole, and titrate with N/10 hydro- chloric acid, using methyl orange as an indicator. Should the water be originally acid, make it sUghtly alkaline with a known amount of potassic hydrate before titration. It is convenient to report alkalinity as representing so many parts of CaCOs per million of water, and to note that such a form of result is quickly obtained by multiplying the number of c.c. of hydrochloric acid, used in the above titration, by fifty. Acidity may be stated in the same terms, using a negative sign, or else as H2SO4. Methyl orange is not a suitable indicator in presence of aluminum sulphate or of iron sulphate; therefore when examining the filtrate from a mechanical filter- plant it is better to substitute either lacmoid or the erythrosine indicator as recommended by the American - Public Health Association. Place 100 c.c. of water in a 250-c.c. glass-stoppered bottle. Add 2.5 cd. or erythrosine (0.1 gramme of the sodium salt * in one litre of distilled water) and 5 c.c. of chloroform. Shake after addition of each drop of the standard acid. The disappearance of the rose- color marks the end reaction. *NajCa,H,IA. 20 EXAMINATION OF WATER. This method is the more convenient of the two if the water under examination be high in color or turbidity. Information is sometimes desired as to the cause of the alkalinity of a water. Is it due to hydroxides,* carbonates, or bicarbonates? To determine this point advantage is taken of the difference in action of two indicators towards these several compounds. Thus while hydroxides, carbonates, and bicarbonates react " alkahne " with methyl orange or erythrosine, only the two former so react with phenolphthalein. While, there- fore, the " alkalin ty " determined by the use of methyl orange or erythrosine might represent that produced by any single one of the three classes of substances above mentioned, or else by a mixture of carbonates and bicar- bonates on the one hand or of carbonafes and hydroxides on the other, the " alkalinity " as measured by using phenolphthalein could be due only to the hydroxides present plus one half the normal carbonates. The following conditions are possible: 1. If the alkalinity determined by use of phenol- phthalein (P) should be zero, then the alkaUnity shown by methyl orange or erythrosine (M) would be due to bicarbonates alone. 2. If P should be equal to one half M, then the alkahnity would be due to normal carbonates alone. 3. If P should be less than one half M, then both * As in the effluents from softening plants. CHEMICAL EXAMINATION OF WATER. 21 carbonates arid bicarbonates would be present and their quantities would be : Carbonates =2P, Bicarbonates = i^ — 2P. 4. If P should be greater than one half M, then bicar- bonates would be absent and the alkalinity would be due to carbonates and hydroxides and their quantities would be : Carbonates = 2(M- P), Hydroxides=M-2(iW-P)=2P-M. COLOR. Hazen's platinum-cobalt color standard* is pre- pared as follows: Dissolve 1.246 grammes potassic platinic chloride (which amount contains 500 milli- grammes of platinum) and 1 gramme cobalt chloride in 100 c.c. strong HCl and dilute with distilled water to one litre. This solution has a color of 500. By placing 1, 2, 3, 4, etc., c.c. of such solution in 50-c.c. Nessler tubes and diluting to the mark with distilled water, standard colors of 10, 20, 30, 40, etc., are obtained. A similar Nessler tube is filled with the water to be examined and comparison is directly made with the color standard. A water possessing a color in excess of 70 should be diluted before reading the color, and then allowance for the amount of dilution should be made. * Am. Chem. J., xiv. 300. 22 EXAMINATION OF WATER. Turbid waters should be filtered through a Berkefeld filter before reading the color. The investigations of the Boston Water Board show that both iron and manganese often enter largely as a cause of color in water from the stagnant layer of a deep pond, but the color of a purely surface water is mainly due to solution of organic material* AS TO ANALYTICAL " STANDARDS." The establishment of hard-and-fast " standards for interpretation of analytical results " is simply an impos- sibihty. Results which would be considered satisfactory for one locality might be entirely inadmissible in an- other. Local standards are the proper ones by which to be guided, and it is to be regretted that local " nor- mals " are not more frequently found on record. For New York and New England the informa- tion is more full, as is instanced by the fine charts of "normal chlorine" prepared for those States.f Following the description of each analytical process to be given hereafter there will be found a paragraph headed "Comparates," but the expression must not be permitted to mislead. The author's intention is * An excellent paper by Mrs. Ellen H. Richards on "The Color- ing-matter of Natural Waters" is published in J. Am. Chem. Soc, January, 1896. t See Water-supply and Irrigation Paper, No. 144, U. S. Geol. Survey. CHEMICAL EXAMINATION OF WATER. 23 simply to place before the reader sundry data arid the opinions of various authorities, and he absolutely dis- claims any desire to set boundaries to the free use of the analyst's good judgment. TOTAL SOLIDS. ; Source. — Material dissolved or suspended in water is natupally derived from the strata through which the water passes, or the surface over which it flows. Thus are obtained waters of all degrees of hardness (see "Hardness") and of great variety of color and turbidity. Determination. — Thoroughly shake the vessel con- taining the sample and then measure out 100 c.c. of the unfiltered water by means of a pipette into a weighed platinum dish. Evaporate to dryness on the water-bath, being careful to place a filter-paper between the dish and the water in the bath in order to prevent any deposit of impurities on the under side of the dish. (A better plan is to make use of a porcelain water-bath filled with distilled water.) When dry, place the dish and contents in an air-bath and maintain the temperature at 105° C. for half an hour. Cool in a desiccator and weigh. Replace in the air-bath and repeat the weigh- ing at intervals of half an hour until a constant weight be obtained. The final weight, less the known weight 24 EXAMINATION OF WATER. of the dish, will give the amount of total solids. This weight multiplied by ten will give the weight of solids per litre of water, which, expressed in milligrammes, will represent parts per million. Should much MgClg be in the water, add a known amount of Na2C03 before evaporation, and allow for such addition in the final weighing. Otherwise there will be loss due to the decomposition of the MgClg. Fig. 2. The author is in the habit of evaporating more than 100 c.c. for this determination in some cases, thereby lowering the experimental error. In order to avoid the trouble of constantly watching and re- filling the platinum dish he makes use of an inverted flask of long neck with a mouth ground to a bevel. Such an arrangement permits of a constant and safe delivery of water to the dish. (See Fig. 2.) The "loss on ignition " is obtained by gradually rais- CHEMICAL EXAMINATION OF WATER. 25 ing the dish and its contents to redness and reweigh- ing after cooling in a desiccator. It is important to note that while no quantitative results of much value are to be expected from the ig- nition in question, yet considerable insight may often be obtained as to the character of the water by ob- serving the intensity of the charring and the presence or absence of fumes. As Dr. Smart says: "The blackening during the process is of more interest than the mere loss of weight. No matter how few parts are lost, if the lining of the capsule blackens all over and the carbon is afterward dissipated with difficulty, the water is to be viewed as suspicious. What are called 'peaty' waters here con- stitute the exception." * Angus Smith pointed out that "in water contain- ing nitrates and nitrites no organic matter would be apparent on burning unless more should be present than these salts could oxidize " — a fact always to be borne in mind. If it be desirable to distinguish between "suspended" and "dissolved" solids, the latter may be determined by evaporating the water after passing through a Berke- feld filter. Comparates.f Average in sundry surface-waters known to be pure 74 " " " " " " polluted 194 " " " ground-waters " " "pure 144 " " " " " " " poUuted 642 * Report Nat. Board of Health, 1880. t See page 21. 26 EXAMINATION OF WATER. These averages are really of but small sanitary value, for the reason that a polluted water may be low in total solids, or vice versa, according to the charac- ter of the soil through or over which the water flows. The Rivers Pollution Comrnission of Great Britain gives as averages out of 589 samples of unpolluted waters analyzed for total solids: Rain 29.5 Upland surface 96 . 7 Deep well 432.8 Spring 282 . Dr. Smart (Nat. Board of Health, 1880) : Safe limit 300 To be condemned 1000 A. R. Leeds (Water Depart., Wiknington, 1883): Standard for American rivers 150 to 200 Wanldyn regards as permissible . . . 575 Colby considers* that water containing over 306 of carbonate of sodium or of common salt is not suitable for irrigation. He beUeves also that for drinking purposes the soluble salts should aggregate not over 680. HARDNESS. Before entering into the question of quantitative es- timation, let it be premised here that "hardness" may be classified under two heads, viz., "permanent" - » : ' * Col. Agric. Expr. Sta;., 1903. CHEMICAL EXAMINATION OF WATER. 27 and "temporary," and many samples of water possess them both. The former is occasioned by the presence of calcium sulphate, and other soluble salts of cal- cium and magnesium, not carbonates, held in solu- tion by the solvent action of the water itself; such a water cannot be materially softened by boiUng under ordinary pressure. "Temporary " hardness is caused by carbonates of calcium and magnesium held in solution by carbonic acid present in the water. Boiling such a water ex- pels the carbonic aeid, whereupon the bulk of the salts separate from solution. Not all of them, how- ever; thus a water gave: Before boiling .... 259 parts CaCOa per million After " 28 " " " " With some it is considered that the calcium is present as a soluble bicarbonate which breaks up upon boiling into carbonic-acid gas and insoluble nor- mal carbonate ; but, as A. H. Allen says, it is not neces- sary to assume the existence of calcium bicarbonate in order to account for the solubility of calcium car- bonate. One water which he examined evolved very small quantities of carbon dioxide on boiling, and yet the precipitated calcium carbonate jvas large in amount. He considers it "probable that calcium carbonate is capable of existing in a soluble colloid 28 EXAMINATION OF WATER. condition, changing, on boiling the liquid, to the or- dinary insoluble modification." * " Permanent hardness " is determined by Hehner's method -t The measured water is boiled to dryness with a known excess of Na2C03. Recently boiled dis- tilled water is added. Precipitated CaCOs is filtered off, and the remaining Na2C03 determined by titration with standard acid and methyl-orange or erythrosine. The loss in Na2C03 is calculated to a corresponding amount of CaSOi. " Temporary hardness " is usually equal to the "alkaUnity," previously determined. See page 18. Should sodium or potassium carbonates be pres- ent, the acid required to neutralize the water residue, after boiling down as above, will be greater than the amount corresponding to all of the standard NaBCOs solution added, for no permanent hardness could be present in such a case. From such excess of acid the carbonates of the alkali metals can be calculated. Their equivalent in terms of CaCOs should be sub- tracted from the total "alkalinity " in order to cor- rectly state the "temporary hardness." Soap-consuming Power. — ^Whether a water be per- manently or temporarily hard it will destroy soap, andsuch destruction is often assumed to measure the total hardness. The assumption is an error, however, * J. Soc. Chem. Ind., vii. 801. t Analyst, viii. 77. CHEMICAL EXAMINATION OF WATER. 29 for water alone will decompose soap, and the pres- ence of carbon dioxide in solution will increase the loss of soap to a notable degree. In short the "soap test " has shown itself unsatisfactory except for the determination of what its name suggests, "the soap- consuming power of the water." Ordinary ha,rd soap is somewhat complex in struc- ture, but for practical purposes we may consider it to consist of sodium stearate, NaCi8H3g02. This salt, coming in contact with the calcium carbonate or sul- phate contained in a hard water, is immediately de- composed, with formation of insoluble calcium stea- rate according to the following equations: CaCOs + 2NaCi8H3502 = Ca(Ci8H3602)2 + Na2C03 or CaSO4 + 2NaCi8H3502=Ca(Ci8H3502)2+Na2S04. Of course none of the soap can be depended upon for detergent purposes until all the calcium salts pres- ent have been thus provided for; hence the enormous waste resulting from the use of some waters may readily be imagined.* * "While no exact rule can be given for estimating the increased expense to a community caused by the use of hard water, in general it may be said (Eng. News, January 31, 1885) that each grain of carbonate of lime per gallon of water causes an increased ex- penditure of 2 ounces of soap per 100 gallons of water. The 30 EXAMINATION OF WATER. In undertaking the estimation of "soap hardness " advantage is taken of the reaction above stated. A solution of soap of known strength is prepared, and is then poured into a given quantity of the water to be examined, until a permanent lather is formed, where- upon, from the known quantity of soap used, the amount of "hardening" salts present may be calcu- lated. This soap test, commonly known as Clark's, is not accurate, and is in some respects unscientific; but it is not without value, especially in a locality such as Troy, N. Y., where the enormous laundries use soap by the ton. Soa-p Solution. — From a new cake of Castile (Syria) soap scrape ten grammes of shavings. Dissolve them in one litre of dilute alcohol (J water). If not clear, filter, and keep tightly stoppered. Sodium oleate may be used in place of soap. Standardizing the Soap Solution. — Carefully weigh out one gramme of pure CaCOs. Dissolve in a little IICl. Evaporate to dr5mess to expel the excess of acid. Neutralize with a slight excess of NH4OH and dilute to one litre. Each cubic centimetre of this so- Southampton water contains about 18 grains of lime and mag- nesian salts per gallon. With such hard water it is probable that the increased expense for soap in a household of five persons would amount to at least $5 to $10 yearly; hence the inhabitants could afford to pay a higher water-rate by the amount of this difference for a soft-water supply." {Engineering News, April 16, 1892.) CHEMICAL EXAMINATION OF WATER. 31 lution will contain an amount of calcium salt equiva- lent to one milligramme of CaCOa. Place 10 c.c. of this solution in an eight-ounce glass- stoppered bottle, make the volume up to 100 c.c. with pure water, and run in the prepared soap solu- tion from a burette, little by little (shaking after each addition), until a lather be formed which persists for five minutes. Even when the amount of soap solu- tion required is approximately known, never add more than half a cubic centimetre at once, and never fail to shake after such addition.* Note the amount of soap solution used. Now re- peat the experiment, using 100 c.c. of pure water only (no calcium salt solution), and again note the amount of soap solution required. This second reading will give the amount of soap solution (no inconsiderable quantity) used up by the 100 c.c. pure water, and by subtracting the same from the reading obtained in the first instance knowledge will be reached of the quantity of soap required for the calcium salt alone. Estimate now the value of 1 c.c. soap solution in terms of calcium carbonate and record the result on the bottle. Perhaps an example would be in keeping: 8.2 c.c. soap solution are required for 10 c.c. CaCOa solution +90 c.c. water. 0.6 c.c. soap solution are required for 100 c.c. water. * See Chem, News, August, 1886, 32 EXAMINATION OF WATER. Hence 7.6 c.c. soap solution are required for 10 mg. CaCOa. Hence 1 c.c. soap solution corresponds to 1.316 mg. CaCOa. Always place the date of standardizing on the bottle, and re-standardize frequently, as the soap so- lution is not permanent. Determination. — Place 100 c.c. of the water in the eight-ounce bottle, run in tne standard soap solution in the manner already stated, read off the amount re- quired, multiply by the known value for 1 c.c. soap solution, multiply this again by ten, and there will be obtained the hardness expressed in so many parts of CaCOs per million of water. It was formerly customary" to report hardness in "degrees " rather than parts per million, but the diffi- culty of deciding which of the several systems of de- grees was referred to provoked so much confusion that a change was made to the present simpler mode of expression.* Magnesium salts decompose soap rather slowly; therefore do not conclude that the end point has been * In England the Clark scale is still in use. Each degree corre- sponds to one grain of CaCOj per imperial gallon of water, i.e., one part in seventy thousand. Water below 6 degrees is considered soft. In France one degree corresponds to one part of CaCOs per 100,000 parts of water. In Germany one degree corresponds to one part of CaO per 100,000 of water, Missing Page CHEMICAL EXAMINATION OF WATER. 33 reached until after the lather has been observed to readily return upon shaking after a few minutes' waiting. If the hardness due to salts of magnesia be required separately, shake the water up with a little solid am- monium oxalate, filter off the precipitated calcium oxalate on a dry filter, and determine the hardness in the filtrate. When a water is so hard as to require a greater amount of soap solution for the 100 c.c. of the water than suffices to saponify 23 mg. CaCOs, better re- sults are obtained by diluting the water with an equal bulk (or more, if necessary) of pure water, inasmuch as too heavy a precipitate of the calcium stearate ap- pears to interfere with the proper lathering. Of course the influence of the additional quantity of water must be allowed for. For constant results the hardness of a water should be taken at a temperature of 15° C* Comparates. — The average hardness of good waters as given by the British Rivers Pollution Commission stands : Rain 3 Upland surface 54 Deep well 250 Spring 185 Wanklyn allows 575 * J. Chem, Soc„ Ixiv. ii, 347- """" 34 EXAMINATION OF WATER. Leeds's standard for American rivers, 50 for soft, 150 for hard. Middleton thinks that from 40 to 70 parts per mil- lion of hardness will give the most satisfactory results generally, and that the hmit of hardness for pubhc supply should be placed at 350 parts per milhon* Pearmain and Moor f consider that "a greater hard- ness than 300 is undesirable from the hygienic stand- point." They classify as follows: Very soft 30 to 50 per million Moderate 50" 100 " " Hard. 100" 300 " " Very hard. above 300 " " The rating of water as "hard" or "soft" is very often a matter of local preference. Thus the writer has encountered cases of complaint from people using a water of as low a hardness as 30 parts per million; and has heard others described as of " good quahty for boiler and laundry uses " a water which ran 66 in hardness. Mter wide in- quiry among industrial water users the author has concluded to classify waters as " soft " which do not * " Water-supply," page 17. f "Water-analysis,'' page 48, Missing Page Missing Page CHEMICAL EXAMINATION OF WATER. '35 exceed 50 in hardness; to call those ''hard "which exceed 100; and to consider the intermediate values as a sort of neutral ground where local conditions and preferences shall govern. CHLORIlvrE. Water is rarely found free from chlorine, yet,, not- withstanding its almost constant presence, there is hardly a factor in the sum total of water-analysis tow- ards which attention is more quickly turned, or re- garding which there is closer scrutiny. In most instances chlorine is present in the form of common salt, washed from the air or soil, or added as one of the constituents of sewage. Salt itself is, of course, unobjectionable in the quan- tity usually present, but, it being so largely used in our food, there is always warrant for suspecting sewage contamination where the figures for chlorine run high. True it is that those figures are at times mislead- ing, but they, like other data in water-analysis, must be considered with judgment, and due weight be ac- corded the character of local surroundings. If the district whence the water comes be naturally rich in salt, as is the. case with the deep-seated waters of Central New York, such fact must be borne in mind when formulating an opinion as to quality. 36 EXAMINATION OF WATER. Comparison should be made with a local water, of the same general character, known to be pure; and for that purpose State maps, such as those issued for New York and New England, are most valuable, and their construction is well worth the expenditure of public money.* The influence of the sea upon the "normal chlo- rine " of these States is made apparent by the charts. Such influence is naturally marked in an insular country like England. "Normal chlorine" of a district is the amount of chlorine occurring in the unpolluted waters thereof. Ponds are the best waters to use for its determination. The " normal chlorine " for deep-seated waters should be placed in a separate class. Variation in the chlorine-contents of rain-water always occurs inland, although not to the same de- gree as upon the coast. For instance, the mixed monthly rain and melted snow at Troy, N. Y., dur- ing 1896, contained the following amounts of chlo- rine : * The chlorine maps for Massachusetts and Connecticut are given as illustrations. More complete "isochlor charts" will be found in Water-supply and Irrigation Paper No. 144, U. S. Geol. Survey. CHEMICAL EXAMINATION OF WATER. 37 January 2 . 50 per million February 1.07 " March 1.55 " April 0.75 " May 1.25 " June 1.15 " July 1.05 " August 2.00 " September 0.60 " October 3.00 " November 2.25 " December 2.50 " Mean. 1.64 While not strictly city rain-waters, the Troy sam- ples were doubtless ■ affected by the neighborhood of the city. Although varying with the locality, yet the amount of common salt lifted from the ocean in spray and subsequently dropped upon the land in rain is always noteworthy. Professor Clark reports the Roth- amsted, England, figures as 24 pounds per acre per annum. Ground-water is more directly influenced than rain- water by the presence of human habitation. Thus 38 EXAMINATION OF WATER. the Massachusetts Board of Health (1890 [1], 680) found that twenty persons per square mile will add, on the average, 0.1 part per milUon of chlorine to the water flowing from such, district. The determination of chlorine in water is extremely simple. It depends upon the fact that if to a solu- tion of a chloride which has been colored yellow by addition of a little potassium chromate a solution of silver nitrate be added, white silver chloride will be produced until the last trace of chlorine be disposed of, whereupon red silver chromate will begin to appear. The reagents required are : Standard Silver Solution. — Prepared by dissolving 4.8022 grammes of crystallized silver nitrate in one litre of water. Each cubic centimetre of such a solu- tion is of a strength sufficient to precipitate one milli- gramme of chlorine. In common with all other reagents for water-analysis, it should be kept in bottles having caps covering the stoppers; such as are used for volatile' liquids. Potassium Chromate, Indicator. — Dissolve 2 grammes of the pure salt in 100 c.c. of distilled water. Should the reagent not be perfectly free of chlorine add a little CHEMICAL EXAMINATIO^' OP WATER. 39 silver nitrate until red silver chromate begins to pre- cipitate; let the precipitate settle and decant the liquid for use. Determination. — One hundred c.c. of the water to > be examined are placed in a large Nessler tube; 1 c.c. of the potassium chromate solution is added, which will give a distinct yellow color, and then the standard silver solution is run in from a burette, until the red tint of the silver chromate just appears. From the known amount of silver solution used the amount of chlorine present is obtained, and this, multiplied by ten, will give the chlorine in milligrammes per litre or parts per niilUon. To determine with accuracy the first appearance of the red tint, it is best to make the examination in yel- low light, either by the use of a photographic ' dark room " lantern with a front of yellow glass, or by simply looking through a plate of such glass. Reflec- tion from a porcelain tile throws the light through the length of the Nessler tube, and side light is cut off by a black screen. For the sake of accuracy it is better, during the titration, to have a second tube of the water, also col- ored with potassium chromate, in order that the forma- tion of the red tint in the vessel operated upon may be, by contrast, more readily detected. A(Sd waters should bs neutralized with Na2C03 before beginning the chlorine determination. On the 40 EXAMINATION OF WATER. Other hand should a water's alkaUnity be due to normal carbonates or to hydroxides, as in the case of an overdose of lime in the softening process, it should be neutralized with H2SO4, any excess of which is in turn neutralized with Na2C03. In all of these cases the indicator used should be phenolphthalein. Different waters, equally clear, and containing the same amount of chlorine, differ greatly in their ability to give a sharp " end reaction." It therefore often aids the eye to prepare a third tube containing distilled water to which has been added the chromate indi- cator and 1/10 c.c. of the silver solution. This " over- dose " having been matched by operating upon the unknown water, allowance is made by subtracting 1/10 c.c. from the burette reading. Many waters possess such deep color, or such tur- bidity, as to interfere with proper titration; under such circumstances it is best to heat 500 c.c. of the water with 3 c.c. recently precipitated and washed aluminum hydroxide and then filter it, or allow it to stand twenty- four hours in a tall glass cylinder. The coloring matter or turbidity is thus removed, and the water cleared for use, With waters high in chlorine it is often very difficult to decide just when the red color begins to appear, for the reason that it is hard to compare the clear yellow liquid of the comparison-vessel with one which has become turbid from precipitation of silver chloride. In such a case it is well to roughly determine the CHEMICAL EXAMINATION OP WATER. 41 chlorine present and then to make a second deter- mination, using for comparison 100 c.c. of the water to which has been added not only the chromate indicator, but also an amount of silver nitrate solution just short of that necessary to satisfy the chlorine present. By these means the eye is greatly aided in noting the slightest appearance of red tint, for in respect of turbidity both vessels are practically ahke. The eye can be further aided in chlorine determina- tions by observing the comparison tubes through a sheet of yellow glass. It makes no difference at what rate the silver solu- tion is added during titration. Circumstances sometimes demand, for purposes of special comparison, a closer reading for chlorine than is possible when only 100 c.c. of the water are en- ployed. For such purpose it is best to place the measured quantity of water in a large porcelain casse- role and to make it shghtly alkaline with NaaCOs before concentration. After reduction of the volume to 100 c.c. the process is continued as already described. It is important that the same volume (100 c.c.) be always secured before running in the silver nitrate solution; therefore distilled water must be added if the concentration should have been carried too far. The porcelain of the dish does not interfere with this determination, but it is very important to care- fully scrub and wash down its sides after evaporation. 42 EXAMINATION OP WATER. When the chlorine is very low it is good practice to add to the water in the Nessler tube J c.c. standard salt solution (see page 53) and then allow for the chlorine so added. The eye is aided thereby in determining the end point. High chlorine often causes confusion in reading the end point. A false end point must be always guarded against by the addition of several extra drops of the silver solution, which overdose will produce a marked red coloration if the true end point be already reached. Although a water high in chlorine may Be diluted before applying the method described, yet perhaps better results would be secured by employing Volhard's Process, as follows: Take 100 c.c. of the water, or a larger bulk concentrated to that volimie after addition of a little sodium carbonate. Add 3 or 4 c.c. ferric alum solution, and '2 c.c. strong nitric acid (free from nitrous fumes). Add small* excess of the standard silver nitrate solution Filter, wash, and titrate the excess of silver with standard KCNS solution. The silver solution used up by the chlorine can be calculated. Do not omit to filter, as it avoids risk of action between the AgCl and Fe(CNS)3. Comjparates. Aveiage In sundry surface-waters known to be pure 3 .57 " ■' ■' " polluted 6.06 " " " groundwaters " " " pure 3.3 " " polluted 91.7 * For objection to large excess, see/. Am.fihem. Soe., xs^fiii, 1344. CHEMICAL EXAMINATION OF WATER. 43 The Rivers Pollution Commission reports the average amount of chlorine in 589 samples of unpolluted English waters as follows : Rain 8.22 Upland surface 11.3 Deep well 51 . 1 Spring 24.9 (Great Britain being an island, chlorine would naturally run high.) Leeds's' standard for American rivers, 3 to 10. Ordinary sewage, about 110 to 160. Human urine (average of 24 samples), 5872. NITROGEN AS NITRITES. Frankland writes: "When fresh sewage is added to water already containing nitrates, the latter are gen- erally reduced to nitrites," and it may be there are none to disagree with him; but when he adds that "when nitrites occur in shallow wells or river-waters, it is highly probable that these waters have been very recently contaminated with sewage," Wanklyn op- poses such a view and declares that "nitrates and nitrites have been erroneously regarded as measuring the defilement of water." Finally, in the report of the National Board of Health for 1882, Mallet concludes: "With the facts of this investigation before me I am inclined to attach special and very great importance 44 EXAMINATION OF WATER. to the careful determination of the nitrites and nitrates in water to be used for drinking." This statement of Prof Mallet so entirely accords with the uniform experience of the writer as to force him to regard it as conclusive. Broadly stated, the presence of nitrites, especially in shallow well water, is to be considered as unfavorable. They are at times due to a harmless reduction of nitrates, as by the iron piping of an unpolluted well, but more commonly they are an in transitu product of the oxida- tion of the organic nitrogen derived from a source of contamination. In either case it is necessary to estimate their quantity. Of the several methods used of late for the deter- mination of nitrites the second one suggested by Griess seems to be the most deserving of favor. It depends in principle upon the red coloration ("azobenzol- naphthylamine sulphonic acid") produced whenever "sulphonic acid" and "naphthlamine hydrochloride" are added to an acidified solution of nitrite. N = N / NH2.C6H4.HS03+HN02 = C6H4 +2H2O \ SO2-O N = N H H N N H / H/\/\H H/\HH/\/\H ^' \ ^ H V\/'h ^ hUh hUx/'h SO2-O NH2 H HSO3 NH2 H See Richter's Organic Chemistry, 664, 665, 910, CJS&MICAL EXAMINATION OP WATER. 45 The test is exceedingly delicate and is capable of distinguishing one part of nitrogen as nitrous acid in one thousand million parts of water. The reagents are prepared as follows: Sulphanilic Acid. — Dissolve 1 gramme of the salt in 100 c.c. hot water. The solution keeps well. Naphthylamine Hydrochloride. — Boil J gramme of the salt with 100 c.c. water for ten minutes keeping volume constant. Place in glass-stoppered bottle. The solution tends to grow slightly pink on standing, but not sufficiently so to interfere with its use. Standard Solviion of Sodium Nitrite. — Sodium nitrite may be bought, but its purity is always to be questioned, and moreover it is too deliquescent a salt to be weighed with ease and accuracy. It is better, therefore, to prepare the silver salt, which may be readily handled, and from it the solution required may be made. To a cold solution of commercial sodium or potas- sium nitrite add a solution of silver nitrate as long as a precipitate appears. Decant the liquid and thor- oughly wash the precipitate with cold water. Dis- solve in boiling water. Concentrate and crystallize the silver nitrite from the hot solution. Dry in the dark at the ordinary temperature (using vacuum is better) and keep it in a black bottle. Weigh out 0.22 gramme of the dry silver nitrite. Dissolve in hot water. Decompose with slight excess of sodium chloride, cool if necessary, and dilute to one 46 EXAMINATION OF WATER. litre. Allow the precipitated silver chloride to settle, remove 5 c.c. of the clear solution, and dilute the same to one litre. This second dilution (which is the standard solution to be used) will contain an amount of nitrite per cubic centimetre equivalent to 0.0001 milligramme of nitrogen. Determination. — In order to undertake the deter- mination of nitrites place 100 c.c. of the water to be examined (decolorized with aluminum hydroxide if necessary) in a Nessler tube. Acidify with one* drop concentrated HCl. Add 2 c.c. of the sulphanilic acid solution, followed by 2 c.c. of the solution of hydrochloride of naphthylamine,, mix,t cover with a watch-glass, and set aside for thirty minutes. Pre- pare at the same time other Nessler tubes contain- ing known amounts of the standard solution of sodic nitrite and diluted to the 100-c.c. mark with nitrite- free distilled water, adding the reagents as above. At the end of the time stated (thirty minutes) examine the depth of the pink color formed, and by comparing the unknown with the known an accurate determination of the amount of nitrogen present as nitrites may be made. If much gas be burning in the room, nitrites will * Addition of too much acid might cause nitrates to react as well. (Analyst, xii. 51.) t To accomplish this mixing it is best to use a stout glass rod ten inches long, at one end of which is fused a cross, composed of two pieces of glass rod | inch in length. The mixer is used as a plunger. CHEMICAL EXAMINATION OF WATER. 47 be in the atmosphere. Hence cover the tubes or re- move them from the room during the half-hour interval before reading. It may be worth while to call attention to the fact that the error due to the presence of burning lamps is often much greater than is suspected. In the au- thor's water laboratory the pure distilled water is prepared by the use of a large copper retort heated by a very broad Bunsen burner. Only one other lighted burner is constantly in the room, and that a small one. Distilled water, as delivered by the tin worm, was tested with the following results, dupUcates being run in each instance. One Nessler tubeful of the water was exposed to the room atmosphere, after addition of the "nitrite " reagents, and its duplicate was carefully protected therefrom. The results are stated as parts per million. Nitrites Nitritsa ConditloDs under which Distilled Water was Present in Present in Collected. Protected Unprotected Tube. Tube. Not allowed to come in contact with air of laboratory none 0.0015 Slight contact with air. Tin condensing tube entering neck of receiving bottle .002 .003 Water allowed to drop six inches through open air to receiving casserole 0.007 0.008 Comparates. — In a report upon the presence of nitrites in eighteen "natural waters, believed from actual use to be of good, wholesome character," and collected from every variety of source, Mallet's deter- minations show an average of 0.0135 part nitrogen as nitrites per million parts of water. The average, by 48 EXAMINATION OF WATER. the same investigator, for nineteen waters "which there seems to be fair ground for believing have actu- ally caused disease " is 0.0403 part per million. The author's experience has been that the average amount of nitrites found in good waters is very much less than the value given by Mallet. Over .002 part per million should be looked upon as unfavorable. In this connection it would be well to bear in mind Frankland's statement that "the presence of these salts in spring and deep-well water is absolutely with- out significance; for although they are in these cases generated by the deoxidation of nitrates, this deoxida- tion is brought about either by the action of reducing mineral substances, such as ferrous oxide, or by that of organic matter which has either been imbedded for ages, or, if dissolved in the water, has been subjected to exhaustive filtration." This is merely another in- stance of how careful the analyst should be to become famihar with the source of the water before under- taking to pass judgment upon its quality. Nitrites should always be looked upon with sus- picion if found in ground- or surface-waters. The absence of nitrites, moreover, proves nothing. The author has had a most foul cistern-water for analysis which showed but a trace of nitrites and no nitrates, and yet the water was contaminated with the entire house-drainage and produced serious illness. CHEMICAL EXAMINATION OF WATER. 49 Average in sundry surface-waters known to be pure 0.000 " " " " " " polluted 0.006 " " " ground-waters " " " pure 0.000 " " " " polluted 0.003 Leed's standard for American rivers, 0.003. NITROGEN AS NITRATES. Nitrates present in water are but an additional step in the oxidation of nitrogenous organic matter. They are more liable to indicate putrefaction of animal rather than of vegetable tissue, not only because of the greater quantity of nitrogen present in the former, but also on account of its more ready decomposition. Stoddart claims that "natural waters can, at most, obtain but from 1/10 to 2/10 grain of nitrogen as nitrates per imperial gallon (1.43 to 2.86 per million) from sources other than animal matter; and practi- cally the whole of the nitrogen of sewage may be oxidized into nitric acid without diminishing the risk involved in drinking it." "The proposal to consider a water safe so soon as the nitrogen has assumed the oxidized condition, ir- respective of the quantity that may be present, is en- tirely irrational." * The above warning is really unnecessary for no one would risk an opinion based upon chemical data alone. A knowledge of results derived from a bacteriological examination would supplement the chemical analysis and guard against an error of judgment. '^Analyst, xviii. 293, JO EXAMINATION OF WATER. Eain-water washes a very considerable amount of nitric nitrogen from the atmosphere; thus an official report gives the following amounts of nitrogen as nitrates in sundry rain-waters, showing at the same time the tendency of neighboring towns to increase this item : Parts per Million. England, interior 0.19 cities 0.22 Scotland, near the coast 0.11 " interior 0.08 cities 0.30 Glasgow 0.63 Montsouris, Pdris, average of 18 years 0.73 Nitrogen in the soil is increased by the fixing oi atmospheric nitrogen through the agency of the roots of leguminous plants, such as peas, the process being aided by bacterial action.* Such fixed nitrogen eventually enters the ground- water, and a knowledge of the local "normal" for nitric nitrogen is consequently of advantage when studying the domestic well-waters of a neighborhood. Surface- and ground-waters of good quality are * An interesting experiment to show this was recently made in France. Peas were grown in a closed space, and the nitrogen lost by the confined air was found equal to what was gained by the ground and plants. No such fixation of nitrogen was ob- tained when the soil wa.s previously sterilized. CHEMICAL EXAMINATION OP WATER. 51 low in nitrates, for the reason that such material is quickly absorbed by growing vegetation. As an instance of prolonged influence of organic matter upon well water Thresh* states that he found a large amount of nitrates in a certain well water to be accounted for by the fact that nearby trenches had been filled with bodies after one of the battles of the Civil War in the time of Charles I. After having tried many ways for the determination of "nitrates" in potable water the writer has adopted a modification of the old "picric-acid method," as giving, on the whole, the greatest satisfaction. Phenol di-sulphonic acid is made by the action of phenol on sulphuric acid : CeHsOH + 2H2SO4 = CeHaCOH) (S03H)2 + 2H2O. This reagent, reacting with nitric- acid, forms trinitro- phenol, C6H3(OH)(S03H2)+3HN03 = C6H2(0H)(N02)3 + 2H2S04+H20, which in turn forms yellow ammonium picrate when acted upon by ammonium hydroxide : f C6H2(OH) (N02)3 + NH4OH = C6H20NH4(N02)3 + H2O. The intensity of this yellow color, produced in the water under examination, is compared with standard * Examination of Waters, p. 75. , t See Analyst, x. 200; also a more recent view by Chamot, J. Am. Chem. Soc., xxxi. 922. 52 SXAMINATION OF WATER. colors of known strength, and the quantity of nitrate present thus determined. The interference of chlorides with this process, result- ing in readings decidedly lower than the truth, is well known, but the method is so easy and convenient that it occurred to the writer to try the addition of sodium chloride to the comparison standards in cases of high chlorides rather than abandon the process. The "chlorine" in the water under examination having been previously determined, an appropriate volume of standardized sodium chloride solution is added to each evaporation of standard potassium nitrate solution. Thus the water to be examined, and the nitrate solutions with which it is compared, all contain the same quantity of chlorine. The results are very satisfactory. If the chlorine be below ten parts per million it does not interfere with the nitrate determination. Sabatini suggests the removal of chlorides, before testing for nitrates, by shaking the water at intervals for two hours with an excess of Ag20, filtering and using the filtrate to determine nitrates. Ag2S04 has been similarly used in Germany. — Chem. Abstracts iv: 942. The solutions required for determination of nitrates are : Phenol di-sulphonic acid. — Sulphuric acid, pure and concentrated . . . 37p grammes Pure phenol 30 " CHEMICAL EXAMINATION OF WATER. 53 Place these in a flask and keep the same surrounded by boiling water for six hours. Disulphonic, instead of monosulphonic, acid, is thus produced by the prolonged high temperature, and reacts readily upon the nitrate.* Standard Potassium-nitrate Solution. — Dissolve 0.7221 grammes pure KNO3 in 1 litre distilled water. Evaporate 10 c.c. of this solution just to dryness on the water-bath. Thoroughly moisten with 2 cc. of the phenol-sulphonic acid and dilute to 1 litre. Each cubic centimetre of this solution will correspond to 0.001 milligramme of nitric nitrogen. f Standard Sodium-chloride Solution. — Dissolve 1.6479 grammes pure fused NaCl in 1 litre distilled water. Each cubic centimetre will contain 1 milli- gramme of chlorine. Determination. — Evaporate 100 c.c. (or less, accord- ing to nitrate-contents) of the water to dr3mess on the water-bath, having previously added 1/10 c.c. satu- rated sodium-carbonate solution to prevent possible loss from volatilization of nitric acid. Thoroughly moisten the residue with 2 c.c. of the phenol-sulphonic acid, being careful while doing so to keep the dish covered to avoid mechanical loss, due to the action of the acid upon carbonates. Dilute with water and make alkaline with ammonium hydroxide. Pour into a 100 c .c. Nessler tube. Dilute with water to the mark, mix and * Sanitary Investigation of ttie Illinois River, page 9. ■(■ J. Infectious Diseases, May, 1905, 54 EXAMINATION OF WATER^ compare the depth of color with those produced by dilut- ing different amounts of the standard potassium nitrate solution to 100 c.c, each such comparison-tube having 5 c.c. strong ammonic hydroxide added before filUng to the mark. In case the chlorine be high there should be also added to each tube an amount of standard sodium-chloride solution sufficient to correspond with the amount of chlorine previously found to exist in the water. The evaporations are best made in deep evaporating- dishes of glass which easily hold 100 c.c. After dry- ness is reached the dish, with its contents, should be at once removed from the water-bath. In order to economize time, when dealing with waters low in chlorine, it is convenient to make use of a series of standard "nitrate color solutions." They keep their normal strengths of color quite well, but should not be trusted after having been a few weeks in stock. Before evaporating for the nitrate determination it is best to remove turbidity and to decolorize the water with aluminum hydroxide as under " Chlorine " (see p. 40). Comparates. Average in sundry surface-waters known to be pure . 139 " " " " " polluted... 0.749 " " " ground- waters " " pure ....... 1.4 " " " " " " polluted,... 11.9 Referring again to Mallet's report before quoted,* we find a very marked difference between the average * Report National Board of Health, 1882, CHEMICAL EXAMINATION OF WATER. 55 amount of nitrates present in good, as compared with the quantity found in bad, waters. In thirteen samples of water "known to be pure" the nitrogen present as nitrates averaged 0.42 (the extreme Umits being and 1.04), while in twenty samples of water believed to be objectionable the average figures ran 7.239 (the extreme limits being and 28.403). Such differences justify Mallet's statement that he regards the determination of nitrates as of great importance. Leeds's standard for American rivers 1 . 11 to 3 . 89 The Rivers Pollution Commission gives the follow- ing averages from 589 unpolluted English waters for nitrogen as nitrites and nitrates together: Rain 0.03 Upland surface . 09 Deep well 4.95 Spring 3.83 As illustrating how widely the nitrates may vary in deep wells of good character the following hst is taken from the Analyst, xx. 84: Depth of Well in Feet! N aa Nitrate 200. Stratford 0.00 200. Wimbledon 0.43 490. Chatham 6.85 • 900. Southend 0.71 56 EXAMINATION OF WATER. Depth of Well in Feet. N as Nitrate 600. Witham 6.43 160. Mistley 0.71 -430. Braintree 0.28 305. Colchester 0.00 400 . Norwich 11.43 It is frequently observed that deep waters have their nitrates entirely removed by the reducing action of the iron well-casing. Under such circumstances the nitro- gen appears as high "free-ammonia." Jamieson reports heavy nitrates in Connecticut well- waters, and notes that they produce pitting in boilers. He found in a well-water from the city of New Haven the nitrogen as nitrates as high as 41 .3 parts per million. He also gives a list of twenty other well-waters running from 15.4 to 2 per milhon. Fresh sewage is often found entirely free of either nitrites or nitrates simply because the organic nitro- gen present has had, as yet, no sufficient opportunity to become changed to the oxidized form. For in- stance, the sewage of Troy, N. Y., contains (sample of December, 1895) : Parts per Million. Free ammonia 0.875 Albuminoid ammonia. 0.675 Nitrogen as nitrates . . . none Nitrogen as nitrites . . . trace Parts per Million. Chlorine 31 ' ' Required oxygen "... 89 Total residue 489 on ignition 315 * J. Indust. and Engr. Chem., i. li CHEMICAL EXAMINATION OF WATER. 57 A curious case of pure water with very high "nitrates" came under the writer's observation. The water was from a deep rock-drilled well, which had been "torpedoed" by fifty pounds of nitroglycerine. Note how important the " history of the case " was to a proper interpretation of the analytical results in this instance. NITROGENOUS ORGANIC MATTER. A revolution has been wrought during recent years in the determination of organic matter in potable water. Methods have arisen and disappeared. Authors of the highest rank have combated each other in print, with a success in establishing their views that has not always been commensurate with their positiveness in stating them. It was in an effort to throw a little unprejudiced light upon the several processes of rival writers that Mallet undertook the investigation from the report of which we here so often quote — an investigation that required a period of years for its accomplishment, and which marks an era in the history of water- analysis. It will be remembered that the "cycle of organic nitrogen" may be represented as starting with the nitrogen firmly bound in the organic molecule, whence it is released through disintegrating agencies and appears towards the end of its course as a con- 58 EXAMINATION OF WATER. stituent of ammonia, then of nitrites, and finally of nitrates; after which, through its availability as plant- food, it again starts upon its organic career. The most general method now employed for obtain- ing information as to nitrogenous organic impurity is Wanklyn's Albuminoid-ammonia Process. — By the employment of this method a knowledge of the amount of "free ammonia" present is also obtained. We may outline the process as follows: The "free ammonia" is distilled from a measured quantity of the water, and its amount is determined by what is known as Nessler's method, which will be de- scribed later. A strongly alkaUne solution of potassic permanganate is then added to another portion of the water and the distillation is repeated. Nitrog- enous organic matters are thereby broken up and the resulting ammonia ("albuminoid"), which distils over with the "free," is determined by the Nessler method in like manner as before. It must be noted that the so-called "albuminoid" ammonia does not exist ready formed in the water, but is a product of the decomposition of organic nitrogenous substances by the alkaline permanganate. The term is derived from the fact that albumen gives off ammonia in like manner when similarly treated. The reagents necessary are : Nessler's Solution. — ^Dissolve 35 grammes potassium CHEMICAL EXAMINATION OF WATER. 59 iodide (KI) in about 200 c.c. pure water. Add a satur- ated solution of mercuric chloride (HgCl2) until a faint show of ' excess is indicated. Add 160 grammes solid potassium hydroxide (KOH). Dilute to one litre, and finally add strong solution of mercuric chloride, little by little, until the red mercuric iodide just begins to be permanent. Do not filter from excess of mercuric iodide, but let the same settle to the bottom of the vessel. The finished reagent should have a pale straw color. It is improved by age. Nessler's solution will give a distinct brownish- yellow coloration with the most minute traces of am- monia or ammonium salts. If the quantity of am- monia be at all considerable, a brown precipitate will appear. The reaction in case of either precipitate or coloration will be 2(2KLHgl2) +NH3 +3KOH=NH2HgOHgI +7KI+2H2O. Pure Water. — This must be prepared with great care, in a room free from the usual laboratory fumes. In short, as has been already said, the entire ex- amination of potable water should be undertaken in a locaUty other than a general working laboratory. A most suitable retort for this purpose is of copper, five gallons in size, and with a tin condonsing-worm. Fill it with good spring-water, add a few crystals of 6o EXAMINATION OF WATER. potassic permanganate, distil, collect distillate in 50-c.c. Nessler tubes, and to each successive tubeful so collected add 2 c.c. Nessler solution. No mixer or stirrer is ever employed in " Nesslerizing " as the high gravity of the Nessler solution causes it to quickly sink into and mix with the comparatively light dis- tillate. After waiting five minutes, should a brown tint be observed upon looking through the liquid (Jongitudinally) at a white procelain tile or piece of white paper, the presence of ammonia is indi- cated. Continue the distillation and the Nesslerizing of the successive 50-c.c. portions of the distillate until no coloration is obtained after standing for five minutes. When ammonia ceases to be detected, the distilled water may be collected for use. The dis- tillation should not be pushed too far, both on ac- count of danger to the retort and of possible produc- tion of ammonia from decomposition of the organic material remaining in the bottom. Alkaline Potassium Permanganate. — Dissolve 200 grammes solid potassic ^^hydroxide (KOH) and 8 grammes crystallized potassium permanganate (K2Mn208) in 1250 c.c. of pure water. Boil down in a porcelain dish to one litre and keep for use. Standard Ammonium-chloride Solution. — Dissolve 1.5706 grammes of pure dry ammonium chloride in CHEMICAL EXAMINATION OF WATER. 6 1 half a litre of -pure water. Dilute 5 c.c. of this solu- tion to a half-litre with pure water. This second solu- tion will represent a strength of 0.01 mg. of NH3 per cubic centimetre, and is the standard solution used, DETERMINATION OF FREE AMMONIA. Fit a one-quart glass tubulated retort to a large Liebig condenser,* letting the neck of the retort pass well into the condensing-tube (3 or 4 cm.) and through a large-size soft-rubber stopper. This con- nection mu3t be thoroughly tight. Place 210 c.c. pure water in the retort and add about \ gramme sodic carbonate. Distil off three 50-c.c. tubes of water, and Nosslerize the third in order to be sure that no ammonia yet remains in the retort. Any ammonia that may have resulted from the imperfect cleaning of the apparatus, or that may have been present in the sodic-carbonate solution, will usually all go over in the first 50 c c. of distillate, but the same quantity (i.e., 150 c.c ) must be distilled off in all cases in order that when the actual analysis of the water is started the condition as to volume may be con- stant. In fact, it may be conveniently stated here that * For a description of the retorts, condensers, etc., used by the author see pages 68 and 69. 62 EXAMINATION OF WATER perfect uniformity of conditions is a requisite for success in water-analysis. To the contents of the retort is now added half a litre of the water to be examined. Distil and catch the distillate in 50-c.c. Nessler tubes. The rate of the distillation should be so man- aged as to allow about fifteen minutes for the filling of each 50-c.c. tube. Add 2 c.c. Nessler reagent to each tubeful, and continue the operation with each suc- cessive portion of the distillate until no further re- action for ammonia is apparent after waiting five minutes. Usually four tubes will be sufficient to carry off all free ammonia, but it is the author's custom to always distil off six. From a small burette measure definite amounts of the standard ammonium-chloride solution into several clean Nessler tubes. Dilute each to the 50-c.c. mark with pure water, add 2 c.c. Nessler solution, and after standing for five minutes compare as to depth of tint with the distillates already Nesslerized. With a little practice it will be found easy, by varying the amounts of standard ammonia solution used, to pro- duce tints corresponding to those existing in the dis- tillates, and thereby a most accurate knowledge of the quantity of ammonia actually present may be ob- tained. Such ammonia existed ready formed in the water, either free or as an ammonium salt, and passed DEVICE FOR BEADING NESSLEB TUBES. CHEMICAL EXAMINATION OF WATER. 65 over unchanged with the steam; it is therefore tech- nically known as "free ammonia." The author makes use of the following device for reading Nesslerized ammonia-tubes.* The illus- tration shown on page 63 requires but little expla- nation. Two disks of brass 1/4 inch thick and 6| inches in diameter are joined together by twelve tubes of brass 13/16 inch in inside diameter and 9f inches in length. The glass Nessler tubes, which are 3/4 inch in diameter and 8 inches to the 50-c.c. mark, just fit these brass tubes and are kept from falling through the open bottoms by the holes in the lower brass disk being slightly smaller than the diam- eter of the brass tubes. Each lower brass disk is furnished with a very short but broad pivot (3 by 1/4 inch), which fits into a socket on the wooden stand, thereby permitting the set of tubes to be rotated about a vertical axis. The wooden stand in question has a base of 6f by 13^ inches, supporting the pair of wooden sockets. Between the sockets is a small mirror set at an angle of 45°, which throws light up through the two Nessler tubes under comparison, and permits the observer to see them in the upper mirror as though in horizontal position. The Nessler standards being placed in the set of tubes on the left and the "free" and " albuminoid " ammonias in the set on the right, the two sets can be. ■f Supplied by Emil Greiner & Co., New i'ork, 66 EXAMINATION OF WATER. rotated at will until the colors on the right hand are matched by those of the standards on the left. To make clear the calculation of results let us cite an example: Suppose the first tubeful to have required 9 c.c. standard ammonia solution (diluted to 50 c.c.) to match its color when Nesslerized, the second one 3 c.c, and the third 1 c.c. Then, since each cubic centimetre of the standard ammonia solution corre- sponds to 0.01 mg. NH3, the whole amount of "free ammonia" present in the original half-litre of water would be: 1° 0.09 2° 0.03 3° 0.01 4° 0.00 0.13 mg. Multiplying this by two to obtain the quantity for an entire litre, and remembering that 1 mg. is the millionth part by weight of a litre of water, we find the total "free ammonia" present in the water to be 0.23 -part -per million. Permanent Standards.* — In laboratories where much work is done in water-analysis it is very convenient to keep at hand sets of standards for quickly reading * Technology Quarterly, xvii. 277. CHEMICAL EXAMINATION OF WATER. 67 the Nesslerized ammonia-tubes and the colors due to the iron and other determinations. Such standards are prepared by diluting suitable mixtures of sundry- colored solutions. Useful as they are to men of ex- perience, it is questionable if it be wise to put them into the hands of students who may by their use lose sight of what the real standards are. The writer objects to their employment in a laboratory of instruction for practically the same reason that he opposes the too liberal use of factors in general quantitative analysis. ALBUMINOID AMMONIA. Throw out the residue remaining after the distilla- tion for /ree ammonia, clean the retort thoroughly, and refit it to the condenser. Place in the retort 200 c.c. pure water and 50 c.c. of the alkaline permanganate solution. Distil off three 50-c.c. tubes, and Nessler- ize the third one in order to insure freedom from ammonia. Add half a litre of the water under examination, and proceed with the distillation, and the Nesslerizing of the successive 50-c.c. portions of the distillate, as in the determination of free am- mxmia. The distillation is to be continued until six 50-c.c. tubes are filled. The ammonia determined by this distillation will be total (i.e., "free" plus "albuminoid"); therefore from the Nessler reading of each tubeful of distillate must be subtracted the read- 68 EXAMINATION OF WATER. ing for the corresponding tubeful for "free ammonia": the difference will give the "albuminoid anamonia" for that tube. The calculation is entirely similar to that for free ammonia, as stated. It must be understood that the retorts, condensers and fittings just described are such as would be found in a general laboratory and are not the best and most convenient for special water work. The "ammonia table" used by the author is pictured on page 69. The supports are all of piping. Those holding the retorts also carry gas for the lamps and those for the condensers convey the cooling water. Along the middle of the table are openings leading to the sewer through which the condenser water escapes. Con- nection between retort and condenser is made by a mercury seal.* In working the "albuminoid-ammonia" process it is of importance that sundry minor details should be observed in order that concordant results may be ob- tained. The Nessler tubes used are long and narrow, being 11 J inches total length, and 8 inches from the * All the glassware here described c^n be supplied by Einil Cireiner & Co., New York, o z; S D n ID a o o OS o H « o CHt.MICAL EXAMINATION OP WATER. 71 bottom to the, 50-c.c. mark. They should always be rinsed with ammonia-free water immediately be- fore using. A very convenient lamp for heating the retorts is the broad flat Bunsen (3J inches diameter) with numerous small jets over its surface. Keep the current of cooling water passing througn the condenser at a velocity such that the difference between the temperature of the inflowing and out- flowing water shall not exceed one degree centigrade. Be very careful to have the "standard ammonia" solutions and the distillates at the same tempera- ture when the Nessler solution is added; otherwise equal strengths of ammonia would strike different shades of color and produce error. This end is best achieved by allowing the distillates to attain the tem- perature of the room before adding the Nessler solution. Daylight is better for reading Nessler colors, but, if necessary, a Welsbach burner may be used. Even with the utmost precaution some ammonia will be lost through imperfect condensation, and this 72 EXAMINATION OF WATER. loss will be greater in proportion as the rate of distil- lation is made more rapid; for instance, the follow- ing different results for "free ammonia" were ob- tained from the same tap-water by varying the time required to fill a 50-c.c. Nessler tube : Tube Number. 5 Minutes. 10 Minutes. 15 Minute.^. 20 Minutes. 1. 2 3 4 5 6 0.0050 0.0025 trace 0.0075 0.0050 0.0050 trace trace 0.0250 0.0075 0.0060 0.0025 trace 0.0250 0.0075 0.0065 0.0025 trace 0.0075 2 0.0175 2 0.0410 2 0.0415 2 0.0150 0.0353 0.0820 0.0830 The amount of ammonia in the distillate being therefore a function of the time employed, it becomes necessary to ehminate, so far as may be, any error that might arise from this source by conducting all distil- lations as nearly as possible at the same rate. So manage the lamp, therefore, as to fix the time re- quired for the distillation of each 50 c.c. at p,jteen minutes. It is not sufficient to note the total amount of "free" and "albuminoid" ammonias, but the full notes of the Nesslerizing process must be retained, CHEMICAL EXAMINATION OF WATER. 7^ that the rate at which the ammonia passes over may be determined. (See page 82.) Do not observe the tint of a Nesslerized solution until five minutes after the addition of the reagent. After the expiration of that time the color may be considered constant, no further material change tak- ink place in twelve hours. Consequently, in the case of the examination of many successive samples, the Nesslerized standard solutions need not be made up for each water, but those prepared in the morn- ing may be used during the entire day, proper care being taken to protect them from the action of the atmosphere by covering them when not in use. The routine standards are: 0.00, 0.0025, 0.005, 0.0075, 0.01, 0.015, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, and 0.08. Higher colors than these cannot be read with accuracy. Should the ammonias run beyond the highest of the above standards, remove a definite amoimt from the Nessler tube, dilute it to the 50-c.c. mark, compare with the routine standards, and allow for such dilution. Much trouble was formerly experienced from the low standards becoming clouded or "smoky." This was found to have been due to the fact that, in mak- ing the distilled water, the water in the copper retort had been allowed to run too low, resulting in volatile 74 EXAMINATION OF WATER. decomposition products being evolved from the con- centrated organic matter. Occasionally a citron-green color is produced which masked the ammonia reaction and renders its estima- tion difficult. Dr. Kidder, of the navy, observed this interference with the ammonia coloration, and attributed it to the presence of substances evolved in the putrefaction of organic matter. He concluded f rorn the few experiments he made that the amines are not necessarily concerned in its production, as he found that butyric acid gave a somewhat similar interference to that met with.* As has been already pointed out, water-samples will not keep many days; whence the necessity for a speedy analysis after the collection is once made.f With many waters the tendency is for "free am- monia" to disappear upon keeping; and, as a rule, the "albuminoid ammonia" also diminishes, but this rule is by no means uniform. For instance, the writer found that a certain brown water, after ten days' storage, showed an increase in "free ammonia" from 0.]25 to 0.28 and a decrease in "albuminoid ammonia" from 0.255 to 0.235. The following equation,} giving * Reference Handbook of the Medical Sciences, p. 157. t The changes which take place in water upon keeping havef been carefully investigated by Smart and Mallet (Nat. Board of Health, 1882). X Barwise, "Purification of Sewage," p. :i.'!. CHEMICAL EXAMWATION OF WATER 75 the decomposition of albumen, illustrates the breaking up of albuminoid materials and the increase of "free ammonia." C7H14N2O3 + 6H2O = (NH4)2C03 + 3CH4 + 3CO2 + 3H2. It indicates one of the steps in the "cycle of organic nitrogen." From observations made upon the appearance and disappearance of nitrites there seems to be little doubt that the loss of "free ammonia" is to be accounted for by a process of nitrification. Nitrites are formed at the expense of the ammonia, and they, in their turn, are converted into nitrates by further oxida- tion. Nitrogenous organic matter in water may be considered as belonging to two classes : first, "that which, passes readily into the condition of 'free ammonia' through putrefactive agencies," and which is consequently easily acted upon by the alka- line permanganate solution; and, second, that which is more stable, and from which no ammonia is evolved during distillation with the above reagent. Upon standing for any considerable time this latter class becomes slowly converted into the less stable variety, which in its turn is gradually converted into "free ammonia," the ammonia in turn becoming finally nitrified, as already stated. Thus we have a perfect system of changes, from the stable nitrogenous or- ganic matter on the one hand to the fully oxidized nitrate on the other. _0f course we are citing but a 76 EXAMINATION OF WATER. typical case, and must be prepared to see all manner of departures therefrom in special instances, accord- ing as the character and amount of materials and the nature of the environment may differ. It is good practice to redetermine the albuminoid ammonia after the sample has stood a number of days. By such means an idea may be obtained of the stability of the nitrogenous organic material whence such ammonia is derived. Should hydrogen sulphide be present in the water it would pass into the distillate and react with the Nessler solution. In such a case pLice the half liter of water in the retort. Add 50 c.c. normal H2SO4. Distil off 100 c.c. of water. Add 50 c.c. of normal NaOH and 10 c.c. saturated sodic carbonate solution emd proceed as usual.* Interpretation of Results. — Concerning the interpre- tation of results, Wanklyn, the originator of the method, is very dogmatic, and says: "The analytical characters, as brought out by the ammonia process, are very distinctive of good and bad waters, and are quite unmistakable. There is, indeed, hardly any branch of chemical analysis in which the operator is less exposed to the risk of failure." This statement is altogether too strong. Waters of high organic purity or those of gross pollution are undoubtedly * Bartow and Har.ison. Science, 32, xxxii.477. CHEMICAL EXAMINATION OF WATER. I'j easy to classify, but with the numerous cases which lie about the boundary-line between "good" and "bad" the greatest care is to be exercised in the reading of results and the passing of judgment. One rule, already mentioned, and upon which too much stress cannot be laid, is never to give an opinion con- cerning a water whose history and surroundings are not thoroughly known. As an illustration of variation in the ammonias, the following data are offered : Free Albuminoid Aniizioiiia. Aaunonia. Average in sundry surface-waters known to be pure 0.063 0.066 Average in sundry surface-waters known to be polluted 0. 182 0.228 Average in sundry ground-waters known to be pure 0.009 0.007 Average in sundry ground-waters known to be polluted 0.107 0.081 The "free ammonia" in artesian wells is often ex- cessive under circumstances that make animal con- tamination an impossibility, and even rain-water, freshly collected after periods of long drought, will often exhibit properties calculated to mislead the analyst. C. B. Fox gives the following determinations in pure deep-well waters : Free Albuminoid „^ „ , , Ammonia. Ammonia. Well 230 feet deep . 80 05 " 250 " " 0.76 0.04 " 300 " " ;. 0.74 0.03 " 330 " " 0.37 0.06 " 385 " " 0.59 0.04 " "verydeep" 0.41 0.07 yS EXAMINATION OP WATER. This excess of free ammonia may be due either — "1. To entrance of rain-water; "2. To the beneficial transformation of harmful organic matter into the harmless ammonia, through the agency of sand, clay, and other substances which act on the water in a manner similar to the action of a good filter; "3. To some salt of ammonia existing in the strata through which the water rises; or, "4. To the decomposition of nitrates in the pipes of the well. Mr. H. Slater suggests that the agent concerned in this reduction may, in the case of the deep-well waters, be the sulphide of iron which is found in the clay. "We conclude, then, that the presence of free am- monia in such comparatively large quantities in these deep-well waters is due to the reduction of nitrates and nitrites by sulphide of iron, or some kinds of or- "ganic matter, or some other agent, such oxidized nitrogen salts having been produced in past ages by the oxidation of organic matter." * Free ammonia in deep-well water may, however, be derived from very objectionable sources; as when surface pollution is admitted because of cleavage and fracture cracks in friable rocks, and because of the "dip" of the strata being nearly vertical. The writer has seen numbers of such cases. * Fox, "Sanitary Examinations of Water, Air, and Food." CHEMICAL EXAMINATION OF WATER. 79 Take, for instance, the water from a rock-drilled well in friable shale. The boring was 57 feet deep and was located in a city containing many privy- vaults, the nearest of which was 75 feet distant. The "free ammonia" reached the very high figure of 2.025, and curiously enough there was no "albu- minoid ammonia" whatever. An additional item con- demning this water was the large amount (69- parts per million) of chlorine present. Free ammonia is at times very high in the rain- water collected near large cities, and is liable to run higher in winter than in summer. Of course high figures under such conditions are without objection, assuming a clean roof and a clean cistern; but when dealing with rain-water it must be always borne in mind that storage cisterns are often very foul. Dr. Drown points out the low values commonly found for both "ammonias" in ground-Waters of good quality, and places that for albuminoid ammonia as rarely exceeding 0.025. He shows the influence of growing plants in reducing free ammonia in surface waters, and quotes as illustration the great difference in this item in the water of Mystic Lake with change of season; thus two readings for free ammonia were: August 0.000 January . 573 A further point that is mentioned by the same observer is the liability to high free-ammonia read- So EXAMINATION OF WATER. ings in water from wells sunk in ferruginous, swampy- regions, because organic matter associated with oxide of iron furnishes in absence of oxygen favorable con- ditions for development of ammonia.* Water passed through newly laid and rusty mains will often become materially changed in chemical character as well as in physical appearance. The in- fluence of the iron-rust is to reduce the nitrates present and increase the nitrites and free ammonia. A good water might thus be very readily condemned upon the analytical results alone did the analyst not know its antecedents. Wanklyn would clear away all difficulty of interpre- tation by holding that "albuminoid ammonia above 0.10 part per million begins to be a very suspicious sign; and over 0.15 it ought to condemn a water ab- solutely." Such a hard-and-fast rule is too severe for general appUcation. Many an excellent water is seen to greatly exceed these limits, particularly the brown waters supplying some of our Eastern towns. Numerous peaty waters, of proved wholesomeness, far exceed them. As has already been pointed out, waters of a brown or peaty character are always to be looked upon very narrowly, but some of them are unquestionably of good quality, * Mass. Board of Health, 1892, 324. CHEMICAL IlXAMI\ATION OF WATER. 8l and all of them would be condemned by the proposed standards. The analyst must here again use his good judgment and decide whether or not there is natural and harm- less cause for the high ammonia readings. The depth of color of the water will be a material guide to his decision. The analysis of the water from a mountain lake situated far away from all possibility of sewage con- tamination, gave the following results: Free ammonia .01 Albuminoid ammonia , . 34 An excellent mountain stream recommended for a city supply, although but slightly colored, ran : Free ammonia . 055 Albuminoid ammonia 0.230 As a result of the analysis of fifteen drinking-waters from widely scattered sources, many of them city sup- plies, and all of them beheved to be wholesome. Prof. Mallet gives figures for "albuminoid ammonia" that show an average of 0.152 part per miUion (highest = 0.325, lowest =0.020). Most of these would be con- demned by the Wanklyn standard. 82 EXAMINATION OF WATER. In his report to the Water Department of the City of Wilmington for 1882 Dr. Leeds, as the outcome of his experience in the analysis of American waters, says: "I should venture to propose, as an aid in de- termining whether a water-supply, derived (as most of our American cities' water-suppUes are) from a flowing stream, is good and wholesome, the following highest limits as a standard of purity: Free ammonia . 01 to . 12 per milhon Albuminoid ammonia. ... 0.10 to 0.28 " " Some years ago Dr. Smart pointed out that the rate at which the ammonia is evolved is of an im- portance at least equal to, if not greater than, the total amount of the same; he holds that: "Gradual evolu- tion of albuminoid ammonia indicates the presence of organic matter, whether of vegetable or animal origin, in a fresh or comparatively fresh condition, while rafid evolution indicates that the organic matter is in a putrescent or decomposing condi- tion." This is entirely in accord with present experience. Thus the evolution of albuminoid ammonia was found as follows when analyzing the water of a mountain lake in which was a considerable growth of pond-lilies and other water-plants : CHEMICAL EXAMINATION OF WATER. 83 Nessler tube No. 1 0.0600 " 2 0.0450 " 3 0.0250 " 4 0.0150 " 5 0.0100 " 6 0.0075 " 7 0.0050 " 8 0.0025 0.1700^<2=0.34 "Water giving such results can be looked upon with much more favor than one presenting an albuminoid record such as the following: Nessler tube No. 1 0. 1000 " " "2 0.0350 " 3 0.0125 " 4 0.0025 " 5 0.0000 0.1500X2 = 0.30 Thus we see that the interpretation of results is en- tirely a question of opinion and sound judgment, and in this connection Mallet's conclusion cannot be read without marked interest; he says: "It is impossible to decide absolutely upon the wholesomeness or un- wholesomeness of a drinking-water by the mere use of any of the processes for the estimation of organic 84 EXAMINATION OF WATER. matter or its constituents. I would even go further, and say that, in judging the sanitary character of a water, not only must such processes be used in con- nection with the investigation of other evidence of a more general sort as to the source and history of the water, but should even be deemed of secondary im- portance in weighing the reasons for accepting or rejecting a water not manifestly unfit for drinking on other grounds. There are no sound grounds on which to establish such general standards of purity as have been proposed." As a further aid to judgment analyses of sundry waters in different parts of the country are given on the next page, several of them having caused disease. Also a few instances of waters of reUable quality. As elsewhere throughout the book, the results are in parts per million. It will be observed that a goodly proportion of the impure waters quoted have figures for free ammonia higher than those for albuminoid ammonia. This is always a suspicious sign, unless both numbers in question be low. One of the worst waters in the list, number two, would not have been condemned upon the ammonia items at all, thus showing the importance of judging from the completed analysis. Water number three, from Erie, Pa., is a rare case in the writer's experi- CHEMICAL EXAMINATION OF WATER. 8S ence, showing no albuminoid ammonia. The well is drilled in friable shale and within short distance of city privies. Water number four was from an isolated country summer residence. The water is materially higher in "chlorine" and "nitrates" than the local "normals," and is exposed to drainage from outhouse and stables. s ■a « Is ■gs a 7 " 8 g 10 11 ^hallow city well.. . . : City well 30 ft. deep (o&used typhoid) Roek-drilled city well 57 ft. deep Spring-water (caused re- peated cases of dysen- tery) Well near city Country well, strong salty taste Town well City well 250 ft. deep " " 255" " ■' "226" " Deep well in large stock- yard, Kansas City Hudson River, at Troy, dur- ing freshet Deep city well, in "niadel ground" ' 0.025 0.005 2.025 0.01 0.005 0.59 0.815 1.59 0.31 1.11 1.725 0.42 exces- sive 0.08 0.035 0.025 0.045 0.245 0.075 0.395 0.02 0.08 0.025 exces- sive 122 146 6 24 2S^ '36 102 58 199 80 3 }47 17.38 10 0.025 0.5 0.875 trace 0.25 trace trace trace trace 1.4 1 0.^6 8 554 769 487 35 215 5225 421 681 635 779 205 637 14 15 16 17 18 £19 0^21 22 23 24 Peaty mtn. stream (autumb ) Same stream in winter. . . . Mountain spring Town supply, Elizabeth- town, N. Y Large well-situated spring. . High mountain lake (peaty). Lake Erie (middle of lake) . Lake Superior (40 miles from shore) Flowing wells (N. J. coast). Driven wells (Hempstead, N. Y ) Domestic well (Catskill Mountains). . . . .' 0.055 0.055 0.04 0.23 0.117 0.048 2.4 1.9 4 0.08 1.404 trace 7.4' 6.6 0.3i 0.35 ! 6.6; 1.25 / 0.04S 0.027 0.01 0.045 0.002 0.006 0.34 0.112 1.05 2,2 2 3.5 0.05 1.6 0.08 trace 0.03 0.023 0.02 0.05 1 9 0.1 0.5 trace J;i» 1 0.013 0.004 2.5 1.25 0.35 0.016 0.007 0.75 175 0.35 34 47 i228 106 90 43 134 54 30 22 32 85 EXAMINATION OF WATER. In water number six it is impossible to account for such an amount of chlorine except by assuming some saline deposit. Water number nine was from a well drilled into Hudson River shale, and was protected from immediate surface drainage. The chlorine rose from 58 to 64.3 some fifteen hours after emptying a bushel of salt into a privy-vault fifty feet distant. Water number ten was from a drilled well, in shale rock, constructed with much more care than usual. Extreme precautions were taken to shut out all im- mediate surface drainage, and they were undoubtedly successful. Nevertheless the neighboring privies con- tributed their seepage, raising the "free ammonia" and "chlorine" tremendously above the local "nor- mals." Such results show us how unsafe it is to trust to the purity of rock-drawn water, when, owing to the seamy character of the rock, and the direction and angle of its "dip," almost direct connection may be established between the bottom of the well and the surrounding sources of surface pollution. The bore-hole In some rocks, if not in all, is not circular in section and opportunity is presented for pollution to flow down in the space between the well- casing and the rock wall, thus reaching the bottom of the well. A comparison of waters fourteen and fifteen shows the influence of freezing weather in tying up the foun- tains of "peaty" contamination. CHEMICAL EXAMINATION OF WATER. 87 OXYGEN-CONSUMING CAPACITY. ("REQUIRED OXYGEN.") This detennination (which must not be confused with that of "dissolved oxygen") deals principally with the carbon present in the organic matter and is Kubel's modification of the old permanganate process of Forschammer. The original mode of procedure was published in 1850, and "consisted merely in adding a solution of potassic permanganate of known strength, without any other reagent, to a measured amount of water to be examined, until the liquid had acquired a faint permanent tinge, and then noting the quantity used. It was afterwards ascertained that more uni- form results could be obtained, and with less expendi- ture of time, by causing the permanganate to act in the presence of frise acid or free alkali." Kubel uses a boiling temperature. The reagents required are: Standard Potassium Permanganate Solution . — ^Dissolve 0.3952 gramme of the salt in one litre of distilled water. Each cubic centimetre of such solution will contain 0.1 mg. of oxygen available for oxidation. The available oxygen of the permanganate in pres- ence of sulphuric acid may be represented by the equation KzMnzOs + 3H2SO4 = K2SO4 + 2MnS04 + SHaO + 50. Dilute Sulphuric Acid.— One part of the strong acid to three of distilled water. S8 EXAMINATION OF WATER. Solution of Oxalic Acid (H2C204'2H20). — Dis- solve 0.7875 gramme of the crystallized acid in one litre of distilled water. This solution if titrated against the permanganate solution (while hot, and in presence of H2SO4) should correspond to it c.c. for c.c. In practice, however, this correspondence will be found to be approximate only. The equation is K2Mn208 + 3H2SO4 + 5(C2H204 ■ 2H2O) = K2SO4 + 2MnSO4+10CO2 + 18H2O. The solution tends to grow weaker quite rapidly with lapse of time, and must be restandardized every time it is used. This is, however, but a slight incon- venience, and is accomplished as follows: Ten c.c. of the oxalic-acid solution, diluted with 200 c.c. pure water and 10 c.c. of the dilute sulphuric acid, are titrated, boiUng, with the standard potassium permanganate solution, and the amount of the latter required to produce a faiat pink tinge is recorded. Determination. — Place in - a porcelain cassdrole 200 c.c. of the water under examination, and add 10 c.c. of the dilute sulphuric acid. Heat rapidly to incipient boiling, and run in the standard perman- ganate solution from a burette until the water has a marked red color. Boil ten minutes, adding more permanganate from the burette from time to time, if necessary, in order to maintain the intensity of red CHEMICAL EXAMINATION OF WATER. 89 color observed at the start. Do not let the color fade nearly out, and then add the permanganate in quan- tity, but strive to keep the color as nearly constant as possible by gradual addition. Remove the lamp, add 10 c.c. (or more, if neces- sary) of the oxalic-acid solution to destroy the color, and then add the permanganate solution from the burette until a faint pink tinge again appears. From the total permanganate used deduct that correspond- ing to the 10 c.c. (or more) oxalic acid employed, and from the remaiinder calculate the milligrammes of "required oxygen" consumed by the organic matter present in the water. Correction must be made for nitrites, ferrous salts, or hydrogen sulphide if any of them be present. Example : c.c. Total permanganate solution used 25 Less that required for the oxalic acid 9.7 Hence that required to oxidize organic matter ... 15.3 corresponding to 1.53 mg. oxygen. Therefore "required oxygen" is 1.53X5 = 7.65 per million. Comparates. — ^As this determination deals princi- pally with the organic carbon present, the readings are naturally high in the cases of brown peaty waters, go EXAMINATION OF WATER. and surface-waters carrying organic matter in sus- pension. (See the list of analyses, page 85.) Average in sundry surface-waters known to be pure 1 . 58 " " " " " " polluted 3.00 " " " ground-waters " " "pure 0.31 polluted 1.06 tl i c Leeds's standard for American rivers. . . 5 to 7. Averages from determinations by Dr. Smart: Impure (14 samples) 5.880 Doubtful purity (5 samples) 3 . 073 Medium purity (15 samples) 1.414 Pure (18 samples) 0.581 The severe character of the following French clas- sification is due to the fact that spring-waters are popular in France, and surface-waters are filtered before use: Very pure 1 Potable 2 Suspected 3 to 4 Impure above 4 In the opinion of the writer the determination of "required oxygen" does not furnish information of great value. Deeply colored waters, otherwise pure, are sure to give high results, because of the quantity CHEMICAL EXAMINATION OF WATER. 91 of carbon present, and a simple inspection, with measure- ment of the color, would give equally valuable information. LEAD AND COPPER. For the accurate determination of either lead or copper considerable quantities of the water should be evaporated and the residue then examined by the scheme to be found in works on general quantitative analysis. For the approximate estimation, which is usually sufficient, the ease with which their dark sulphides may be formed provides a ready method (Miller). Prepare a standard solution of lead nitrate, Pb(N03)2, by dissolving 1.599 grammes of the salt in one litre of distilled water. Each cubic centimetre will con- tain 1 mg. metallic lead. Precipitate metalUc copper electrolytically in a plati- num dish, weigh, dissolve it in a few drops of HNO3 and dilute with sufficient water to allow each c.c. of the solution to contain 1 mg. metallic copper. Use this as the standard copper solution. Place the water in a 100-c.c. Nessler tube, slightly acidify with HNO3, pass H2S, and match the tint by operating in a similar manner with measured amounts of the standard lead or copper solution diluted to 100 c.c. 92 EXAMINATION OF WATER. This method will not, of course, distinguish between copper and lead, but distinguishing is not commonly necessary. For the determination of copper in water which has been treated with copper sulphate for algse removal, evaporate several htres to small bulk; slightly acidify with sulphuric acid and deposit the copper electrolyt- ically. Should the deposit be too small to weigh, dissolve it in a little nitric acid, dilute to 100 c.c. pass H2S and determine it by color as above. A convenient test for the presence or absence of copper is the following : Concentrate if necessary. Add a few drops of formaldoxime * (prepared by dis- solving 1 part of hydroxylamine hydrochloride in 5 parts of formaldehyde) . Add some strong KOH solution. A violet color indicates copper. The color fades quickly and must be matched at once for quantitative purposes. IRON. This metal is objectionable if in considerable quan- tity, particularly in water to be used for washing white goods, and for dyeing. A knowledge of the presence of * Trans. Chem. Soc, 1898. CHEMICAL EXAMINATION OF WATER. 93 iron will, moreover, aid in guarding against an invasion of iron-secreting algae such as crenothrix. The standard iron solution is prepared by dissolving 0.1 gramme pure iron in a little HCl to which a few drops of HNO3 have been added, evaporating to dr)Tiess, moistening with HCl, and then diluting to one litre. One c.c. of this solution will contain .1 miUigramme of iron. Determination. —T&ke 100 c.c. of the water; evapo- rate to dryness; ignite sufficiently to decompose organic matter; add 5 c.c. HCl; warm, dilute slightly, filter, and wash; add enough K2Mn20s solution (5 grammes per litre) to make the slight pink color persist five minutes; add 10 c.c. KCNS solution (20 grammes per litre); dilute to 100. c.c. in aNessler tube, and compare the depth of color produced with those formed by known amounts of standard iron solution which have been treated with similar quantities of HCl, K2Mn208, and KCNS, and then diluted to 100 c.c. The standards must be made at the same time because time is an element in this determination. The red color produced tends to pale out even after a few minutes' standing. Comparison must be made at once. Iron which tends to increase in a well-water as the draught upon the underground supply grows in vol- ume is a discourag.ng sjTnptom; for the probabili- ties are' "strong-'that the water will eventually become 94 EXAMINATION OF WATER. unfit for use unless the ever-increasing iron be arti- ficially removed. Klut* considers that iron in water should be rated in parts per million, as follows: Very low 0.2 Average . 2 to 1 . 5 Considerable 1 . 5 to 3 . In his " Filtration of Public Water Supplies," page 186, Hazen says: "Three-tenths of a part per million of metallic iron very rarely precipitates or causes any trouble. "In iron removal plants an effluent containing less than 0.5 is regarded as satisfactory. One containing less than 0.2, as in the case with many plants, is all that can be desired." As the result of wide inquiry among those interested in water for laundry purposes, the writer concludes that iron to the extent of 0.25 part per million may be considered satisfactory: more than 0.5 part per million unsatisfactory; and the values between doubtful. In this connection note the conflicting statements made by the following Massachusetts communities;, the figures given indicate the amounts of iron in the several waters; * Chem. Abstracts, ii. 2409. CHEMICAL EXAMI.\'ATION OF WATER. 95 Methuen . 365 satisfactory Grafton 0.507 Newburyport . ... 0.720 " Cohasset . 380 not satisfactory Hyde Park 0.859 It is well to note in this connection that it takes about 0.3 part per million of iron in solution (not col- loidal nor suspended) to sustain a growth of crenothrix. ZINC. Zinc is not a cumulative poison, but its presence in a water is nevertheless undesirable. Galvanized-iron pipe is attacked by certain waters, especially those that are soft, and spring-water is at times zinc-bearing, as has been especially noticed in Southern Missouri.* For the determination of the metal in absence of lead, copper, and manganese it is best to evaporate three litres of the water to dryness in presence of HCl. Bake for an hour at 110° C. Moisten with HCl, add * Zinc-bearing spring-water from Missouri : Parts per Million. PbSO, trace CuSO, 0.5 CdSO, 0.9 ZnSO^ 297.7 FeSO^ 1.6 MnSO, 6.3 A1,(S0,), 2.5 Parts per Million. CaSO, 109 , 9 MgSO, 19.0 KSO^ 5.6 Na^SOi 5:9 NaCl 4.3 CaCO, 72.0 SiOa 13 . 7 539.9 (Hillebrand, Bui. 113, U. S. Geol. Sur.) g6 EXAMINATION OF WATER. water and filter off SiG2. Make alkaline with NH4OH, boil and filter off the hydroxides of iron and aluminum. Dissolve this precipitate in a little HCl and reprecipitate it with NH4OH. Filter and reject the precipitate. Unite the two filtrates. Boil off the ammonia. Make acid with acetic acid, and, while still hot pass H2S. Let the precipitate settle. Filter and dry. Remove the precipitate from the paper. Ignite the paper ia a porcelain Rose crucible. Add the precipitate and ignite for fifteen minutes in a stream of H2S. Weigh as ZnS. For qualitative purposes, Allen's test is useful: Render the water slightly alkaline with ammonium hydroxide; boil; filter, and add a few drops of potas- sium ferrocyanide. A white precipitate will form in presence of a trace of zinc. When applying this test it must be remembered that only the zinc in solution is detected. That por- tion which is present in insoluble form, suspended in the water, is often the larger of the two. Reports recording that a water contains so many parts per million of lead, zinc, or other metal are common enough, but it is rare to find advance state- ments of what a water is capable of doing in the way CHEMICAX-EXAMJlNATtON. OF WATER. n. of dissolymg mptals should opportlinity be afforded, it of coming in contact with them. In other words, a cUent who possesses a water supply which is very desirable at its source is seldom informed of the possible damage which may result thereto by reason of its being conveyed through metallic piping. After the pipes have been laid and the water admitted to them, record is made of the result as to the metallic solvency, but little is found in the nature of a prophecy antedating the outlay of capital; which prophecy, had it been uttered in time, might have had material bearing upon the investment. Again, if, as occurs in a few instances, the client be told that the water under examination is capable of acting upon certain metals, he is not given the information in such quan- titative form as will enable him to make comparisons between it and other waters with reference to this property. It is well known that all waters do not equally possess the power to attack metals and it is proper to ask that, granting such power to exist, how far is its exer- cise objectionable from a sanitary point of view; or, to state it differently, what amount of metallic salts in solution may be allowed with safety? There is some difference of opin"on among the authorities as to the amount of contained lead required to condemn a water, but all are agreed that even 98 EXAMINATION OF WATER. small quantities should be narrowly watched. Thus, the Massachusetts reports note that one-half part per milhon has caused serious injury.* Haines holds that 0.1 grain per U. S. gallon (1.71 per million) should cause a water to be rejected, f Whitelegge believes that "No water should be used for drinking which contains more than one part of lead per milhon, and any trace, however minute, indicates danger." (Hygiene and Public Health.) Middleton considers 1.4 parts per million of either lead or copper suflScient to condemn a water. | To quote Dr. Summerville in his recent paper in Water: "Lead to the extent of 0.25 part per milhon is sufficient to condemn a potable water." In four cities of Massachusetts where lead poison- ing was pronounced the average amount of the metal present during ordinary daytime use was one part or more per miUion. Occasional instances of "plumbism" were noticed in other towns and doubtless mild or unrecognized cases occurred elsewhere. § In the thirty-first annual report of the London local Government Board (1901 and 1902 Supplement on Lead Poisoning and Water Supply, Vol. 2, page 426), peaty moorland waters are shown to be especially * Mass. State Board of Health, 1898, XXXII. ^ J.Fk. Inst, Nov., 1890. t "Water-supply," page 21. §1*1388. State Board of Health, 1898, p. 543. CHEMICAL EXAMINATION OF WATER. 99 plumbo-solvent, to a degree chiefly governed by the amount of acidity present, and experiments show that such acidity is due, at least in part, to acid-forming bacteria residing in the peat.* The London report is so firm in its belief that the cause of plumbo-solvency has been located that it ventures to rate moorland waters as "safe" if they are neutral to lacmoid and as "dangerous" if they react acid with that indicator. H. W. Clark observed that carbonic acid in, a soft water was the main factor that caused lead to be taken into solution by the waters of Massa- chusetts.! It is by no means new to distinguish between the "solution" of lead and that "erosion" of the metal which some waters exercise whereby insoluble lead salts are formed with appreciable increase in the tur- bidity of the water. For our purposes it will suffice to note that "erosion" does not occur in the absence of oxygen, and we are also to remember that from the sanitarian's point of view "erosion" may be fully as objectionable as "solution" if no opportunity for clarification be fur- nished. In fact, the former may readily be the greater * See also Thresh, " Examination of Water," p. 186, f Engineering News, Dec. 1, 1904, lOO EXAMINATION OF WATER. evil of the two, because of its involving the possibility of the ingestion of large quantities of lead salts held in suspension. Piping water in tubes of galvanized iron is very common, and as zinc is often more easily attacked than lead it is pertinent to ask if it be equally dangerous. So far as our present experience caii guide us towards a correct solution of this question, the reply must be a negative one and the following opinions are presented in support of such contention:" In the journal of the German Society t)f Gas and Water Engineers for 1887, H. Bante collected statistics to show "thiat the use 6f galvanized pipes should be in no way detrimental to health." Similar views are entertained by V. Ehrnaim, director of the water supply of Wurtemberg.* According to Thresh f "there is no doubt that waters containing traces of zinc are used continuously for long periods without causing any obvious ill effects. The water supply to a small hospital with which 1 was connected for some years always contained a trace of zinc, probably never more than half a grain of the carbonate per imperial gallon (7.1 parts per miUion), *J. Fife. /ns«., 1890. t " Examination of Waters and Water Supplies," p.- 85. CHEMICAL EXAMINATION OF WATER. loi but I never observed any indications of its being dele- terious, although such effects were looked for." In the Massachusetts Board of Health report for 1900, page 495, the following table is given showing amounts of zinc in sundry public supplies, the metal having been dissolved from pipes of galvanized iron or brass during ordinary use. The results are averages and are in parts per million: West Berlin 18.46 Milbury 3.08 Newton 1.25 Marblehead 0.85 Grafton 0.73 Wellesley 0.68 Fairhaven . 52 Lowell 0.33 Webster 0.28 Sheffield 8.65 Palmer 2.90 Beverly 2.71 Fall River 0.07 The first of the above, West Berlin, drew its water through 4000 feet of galvanized iron pipes. The quantity of metal dissolved therefrom was certainly large but appears to have produced no evil results. "As far as is known the amount of zinc present 102 ■ EXAMINATION OF WATER. in ' these waters as used is not sufficient to have any effect upon the health . of the consumers of the water," "The Board has investigated the question of the presence of zinc in drinking-water supplies where galvanized iron pipes are used and, except in case of the use of some ground-waters, containing very large amounts of free carbonic acid, which dissolves zinc and many other metals very freely, the amount of zinc found in ordinary water supplies, where gal- vanized pipes are used, is not sufficient, in the opinion of the Board, to give anxiety." * In a private letter of more recent date the president of the above mentioned board, says: "It there had been any harmful effects of the presence of zinc in the pubhc drinking-waters of the state that fact would have undoubtedly been brought to our attention. No statement to this effect had been made, nor has there seemed to this board reason suspecting serious danger from this source." As an instance of long continued use of a water con- taining much zinc, the case of Brisbane, Queensland, should be quoted. In that city rainwater tanks built of galvanized iron are found in all the houses. The water, which is in common use, contains about 17.1 * Massachusetts Board of Health, 1902, XLIII, CHEMICAL EXAMINATION OF WATER. IP3 parts per million of zinc, yet no harmful effects have been observed.* In his experience the writer has been unable to trace any evil effect clue to the presence of zinc in drink- ing-water, even when the quantity rose as high as 23 parts per million in a water which is in constant use. It might be well to add, that in the particular case just cited the zinc was derived from a long stretch of galvanized iron pipes and the amount of the metal present was subject to great and frequent fluctuations for reasons that were not apparent. It must be admitted, however, that, even on the assumption that the presence of zinc in a water is of no sanitary significance, its being there is nevertheless not desirable, and the probability of a supply being able to dissolve it should be determined and reported. Determination of Action of Water upon Metals.— In order to report the possible action of water upon any of the common metals let such action, whether of solution or erosion, be stated in parts per million, and let it be that of one litre of water acting upon one.square decimetre of bright metal for one hour at 15° C. The mode of procedure followed by the writer is to submerge a piece of bright sheet metal, one decimetre square, in two litres of water contained in a wide- mouthfid bottle. The water is occasionally given a * Hazen, Eng. News, April 4, 1907. 104 EXAMlNATtON OP WATER. .. gentle motion and is kept at 15° for one hour, after which time the metal in solution or suspension is deter- mined. One hour is sufficient time to allow of the watching of metallic solvency, and let it be added, the limiting of the time of action to the standard period is important, for the rate of action of the same water is not only variable, but the ratio of the total action during different lengths of time is not a simple one. Thus, the quantity of metal attacked in ten hours is by no means ten times that acted upon during one hour. Let it be said that although we know in a general way that softness, acidity, dissolved gases, and the presence of much chloride or nitrate will tend towards metallic solvency, while alkalinity and hardness aro rated as protective agents, yet it is far better to actually, test a water with reference to its behavior towards metals than to attempt any prophecy of its action based upon anal3d;ical knowledge of what the water may contain. Arsenic occurs in some waters naturally, and both arsenic and chromium may be present from industrial waste. Should the presence of these elements be sus- pected, their determination should be undertaken, in the concentrated water, by the usual gravimetric methods. CHEMICAL EXAMINATION OF WATER. 105 ALUM. When examining the eflBuent from mechanical filters, it becomes essential to determine if any unde- composed coagulant (i.e., alum) passes into the fil- trate. For such purpose the "logwood test" pro- posed by Mrs. E. H. Richards is the most valuable. Boil some logwood chips in a little water for a few min- utes and drain off the resulting extract. Repeat the boil- ing and again discard the extract. Boil for the third time about fifteen minutes and keep the extract for use. Place about 100 c.c. of water in a porcelain dish, add a little of the logwood extract, followed by 2 c.c. acetic acid. If even a trace of alum be present in the water the logwood will produce a violet tinge which will not be discharged upon addition of the acetic acid. A "blank" should always be run for comparison. The logwood extract is reliable but for a short time, especially if exposed to air. It is never safe to trust it when more than a day old. Logwood for this test cannot be readily purchased, that obtainable from the druggists being absolutely worthless. The best method of obtaining it is to personally bore the chips from the centre of the log. When examining the filtrate from a mechanical plant by the logwood test, it would be well to take the alkalinity also. io6 EXAMINATION OF WATER. If the filtrate be alkaline, free alum cannot be pres- ent, and any logwood reaction then observed would be due to particles of A1(0H)3 passing the sand bed and becoming dissolved in the reagents employed. Lacmoid, or erythrosine, should be used as the indi- cator, as methyl-orange does not indicate an acidity due to alum.* (See page 19.) It is worth remembering that a "dose" of one grain per gallon of aluminum sulphate (containing^ 17 per cent AI2O3) will require about 8 parts per mil- lion of "alkahnity" in the water for its complete de- composition. PHOSPHATES. Phosphates are rarely present in more than minute traces in waters fit for domestic use, although not un- common in those which are contaminated. Excellent waters do at times contain them, however, in very notable quantities. For instance, the writer found as much as 2 parts per million (calculated as calcium phosphate] in an artesian water on the New Jersey coast. "Hehner suggests 0.5 part of P2O5 per million as the limit for good waters, but many excellent waters contain more than this amount, f To determine them Phipson's method is convenient. He takes a large measure of the water, adds a little alum solution, followed by a few drops of ammonia, * See Fullers' Louisville Report, 55 and 447. t Thresh, Exam, of Waters, p. 80. CHEMICAL EXAMINATION OF WATER. 107 and then makes the solution ae'.d with acetic acid. The aluminum phosphate is filtered off, dissolved in nitric acid, and precipitated with ammonium molyb- date solution in the usual way.* Woodman proposes a colorimetric method which takes but a short time.f Take 50 c.c. of the water. Add 3 c.c. HNO3. Evaporate to dryness on the water- bath. Heat for two hours in the water-oven. Extract with cold water. Dilute to 50 c.c. in comparison tube. Add 4 c.c. ammonium molybdate (50 grammes per litre) and 2 c.c. HNO3. Mix, and after three minutes compare with standards prepared by diluting standard phosphate solution (0.1 mg. P2O5 per c.c.) to 50 c.c. and adding reagents as above. A blank, using distilled water, should also be run. MINERAL RESIDUE, Should a partial analysis of the mineral residue be de- manded, which is not common except in the case of a " boiler " or a " mineral " water, one or more litres of the water are strongly acidulated with hydrochloric acid and evaporated to dryness in platinum. The dry residue is heated in the air-bath at 120-130° C. until acid fumes cease, then cooled, thoroughly moistened with strong hydrochloric acid, digested with water and the separated silica filtered off. * Chem. News, lvi.'251. t /. Am. Chem. Soc, xxiv. 737. lo8 EXAMINATION OF WATER. The silica is weighed, ignited with hydrofluoric acid, and determined by difference in the usual manner. Barium, if present, will be found in the residue after volatilizing the silicon fluoride. It should be fused, brought into solution, and pre- cipitated by sulphuric acid. Iron and Aluminum are weighed together as oxides after precipitation by ammonium hydroxide followed by ignition. Calcium is thrown out of the filtrate from the iron and aluminum by ammonium oxalate as is usual, and its filtrate is evaporated to dryness in platinum and ignited to remove excess of ammonium salts before precipitating magnesium in the customary manner. Lithium is determined by Gooch's method given in J. Am. Chem. Soc. XII, 214.* Sulphates are determined by use of barium chloride in a separate evaporation after removal of silica. For "boiler waters," however, Prof. Main suggests mak- ing the filtrate from the magnesium acid with hydro- chloric acid and then precipitating at once with barium chloride. This saves much time and is very convenient. C. B. Dudley, chief chemist of the Pennsylvania R.R., determines scale-forming ingredients by: De- * See also "Determination of Lithium," by Skinner and Collins, Bui. 153, Bureau of Chemistry, U. S. Dept. Agric. CHEMICAL EXAMINATION OF WATER. 109 termining the total solids as usual; treating the residue with 50 per cent alcohol and designating the undissolved material as "scale-forming." Manganese is now determined more frequently than in the past. The following rapid method is due to R. S. Weston. * Take enough of the sample to give from 0.01 to 1 mg. of manganese. Evaporate with about 25 c.c. of nitric acid (1 acid to 3 water). Gently ignite the residue or bake it for one-half hour at 130° C. Add 50 c.c. of the nitric acid and when the solution is cool add about 0.5 gramme of sodium bismuthate. Heat until the pink color disappears. Add enough sodium thiosulphate to clear the solution if manganese dioxide is precipitated, and heat to dispel all oxides of nitrogen. This step is usually unnecessary. To the cool solution add sodium bismuthate in excess, stir a few minutes, and filter through thoroughly washed asbestos in a Gooch filter. Wash with dilute 3 per cent nitric acid, transfer filtrate to a large Nessler tube, and make up to 100 c.c. with dilute nitric acid. In another tube put 100 c.c. of dilute 3 per cent sul- phuric acid and add standard potassium permanganate solution until the color of the sample is matched. From the volume of potassium permanganate used, cal- culate the weight of manganese. * J. Am. Chem. Soc, xxix. 1074. no EXAMINATION OF^'ATER. . ^ The presence of chlorides interferes with the deter- mination. Samples which contain large amounts of chlorine should be treated before evaporation with a slight excess of silver nitrate and then filtered. DISSOLVED OXYGEN. The following method is that devised by M. Albert- Levy, of the Montsouris Observatory, Paris : A pipette of about ipo c.c. capa^jity is provided with an upper and a lower stopcock^ and the capacity of the same between the stopcocks is determined. Above the upper stopcock the tube is expanded into a shgrt, cylindrical funnel. The pipette is completely filled with the water to he examined, and the funnpl is emplSed. The cocks having been closed, the pipette is wiped off and fixed in a suitable clamp. Two c.c. of* dilute potassic hydroxide solution are placed in the funnel and, by careful opening of the cocks, introduced within the pipette without the admission of air. After washing the funnel 4 -c.c. of a solution of ammonium ferrous sulphate are-placed therein, and, by similar means, also admitted within the pipette. In presence of the alkaline solution the oxygen dissolved in the water will in five minules, after gentle agitation, oxidize the ferrous salt to ferric, and a mixture of the two hydroxides will shortly settle to the bottom. After again washing the funnel 2 c.c. of concentrated sul- CHEMICAL EXAMINATION OF WATER. Ill phuric acid are placod ^rein, and the upper stopcock ^.lone is opened. The 4ftgher gravity of the acid will llcause it to slowly enter the gipette, where it will acidify the contents and dissolve the hydroxides of iron. The contents and washings of the pipette are turned into a flask and titrated with the staij^iijylHNhLtion of potassic tan^flpik^it ifflRTon, page' permanganate* already descflBWjon page'87. A. blank is now titrated containing «^'nilre of 100 c.c. of the water, 2 c.c. of the sulphuric acid, 2 c.c. of the jrotassic^ hydroxide solution, and 4 c c. of the ammonium ferrous *Should much chloride be present, as in sea-water, M. Albert Ijevy suggests the substitution of the bichromfte in place of the permanganate of potassium. 112 EXAMINATION OF WATER. sulphate solution. The difference between these two titrations (acid reaction having prevented oxidation in the second instance) will give the amount of ferrous salt oxidized by the oxygen dissolved in the water. The volume of the water operated upon will be the volume of the pipette (F) less the volumes of the alkaline and iron solutions, nahiely: ■ y-(2 + 4)'c.c. Note the temperature of the water, and report the dissolved oxygen when found as a percentage of that required for complete saturation at that temperature, making use of the following table : VOLUME OF OXYGEN, .IN CUBIC CENTIMETRES, RE- QUIRED TO SATURATE ONE LITRE OF WATER AT VARIOUS DEGREES CENTIGRADE. (Winkler.) ' Degree. C.C. Degree. C.C. Degree. CC 0. 10.187 11 7.692 21 6.233 1 9.910 12 7.518 22 6.114 2 9.643 13 7.352 23 5.999 3 9.387 14 7.192 24 5.886 4 9.142 15 7.038 25 5.776 5 8,907 . ^ 16 6.891 26 5.669 6 s.esar 8.467 «fill7 6.750 27 5.564 7 18 6.614 28 5.460 8 8.260 .,.J9 6.482 29 5.357 9 8.063 20 6.356 30 5.255 10 7.873 1 Beriohte, 22, 1889, 1772, CHEMICAL EXAMINATION OF WATER. ir3 Palmer points out that supersaturation of water with oxygen may be caused by the liberation of the gas through the action of either micro-organisms or larger plants containing chlorophyl.* Deep samples for dissolved oxygen are taken by attaching to the lower end of the pipette a short rubber tube, which may be flexed upon itself by pulling a string fastened to its extremity. The pipette having been sunk with the rubber tube closed by flexion and with both cocks open, water is admitted by allowing the string to slacken. Upon again tightening the string and raising the pipette towards the surface the cocks should be carefully closed before the surface is fully reached. Carbon dioxide in solution tends to cause a solvent action upon lead, especially if the water be soft. Should it be decided to include an estimation of carbon dioxide in the analysis, take 100 c.c. of the water and titrate with standard Na2C03 solution, using phenolphthalein as an indicator.f The determination of other gases present in solu- tion is not commonly of sufficient value to repay the expenditure of time required for such work. An odor hke that of sulphuretted hydrogen must * "Streams Examination," page 87. ■f Chemical News, Ixx. 104. 114 EXAMINATION OF WATER. device for collecting gases escaping prom water, (travers.) CHEMICAL EXAMINATION OF WATER. 115 not be taken as proof positive of the presence of that gas in a water, inasmuch as mixtures of sundry hydrocarbons will often greatly mislead the sense of smell, Samples in which dissolved gases are to be deter- mined should be examined in the field. They do not admit of transportation. When it is desired to secure for analysis a sample of the gas that sometimes is observed to bubble in considerable volume from some springs, the device illus- trated on page 114 will be found of value. The whole apparatus having been filled with water and then placed in the position indicated, the gas will be sucked over into the sampling cyUnder. The stop-cocks are then closed and the sample is ready for shipment.* PUTRESCIBILITY. Water analysts may be called upon to pronounce upon the fitness of a sewage effluent for admission to a stream, and to say whether or not it is likely to develop a nuisance. The writer is not prepared to formulate here a general definition of "a nuisance," believing, as he does, that much depends upon the character of the local conditions, but the ability of a water to * See Travers, "Study of Gases,'' p. 44. il6 EXAMINATION OF WATER. "care for itself" and oxidize its own organic matter has been widely accepted as a proper measure of its being in a condition suitable for admission to lakes and rivers. But even this rule must be used with judgment, for it would be manifestly unjust to apply it as rigor- ously for a large body of water as for a small. Jackson and Horton * have recently made certain changes in the test devised by Spitta which may be stated as follows: Use a 250-c.c. bottle, "closed by a perforated rubber stopper, in which is inserted a medicine dropper with a large tight rubber bulb." The dropper is filled with water and the bulb placed in position in " a collapsed state." Change in volume due to expansion of the liquid is thus provided for. Prepare a one-twentieth of one per cent solution of commercial methylene ^rgen_t (i.e., J gramme per litre) and use 1 c.c. of such solution for the 250 c.c. test as above. Incubate at 20° C. for four days. Decoloriza- tion indicates putrescibihty. For the softening of hard waters lime and sodium carbonate are used and an estimate has to be made of the quantities required. Determination of" Lime Value." — ^To a known volume of the water (say 250 c.c.) in a half-litre flask add 100 c.c. * Am. J. Pub. Hygiene, May, 1909, 319. t The report of the Am, Pub, Health Agso, recommends methylene blue CHEMICAL EXAMINATION OF WATER. 117 of saturated lime water. Boil, cool, dilute to the mark and mix. Quickly filter a part through a dry filter and titrate a measured portion of the filtrate with N/10 HCl, using methyl orange as an indicator. Such titration will give the excess of lime present, the strength of the lime water in terms of the acid having been previously determined. The quantity of lime required to precipitate the car- bonates which cause the " temporary " hardness in the water can be then readily calculated. Determination of "Soda Value." — ^Boil a measured voliune of the water in a half Utre flask. Add an excess of N/10 Na2C03, noting the amount used. Boil, cool, fill to the mark with distilled water and mix. Filter or allow to settle. Titrate in a portion the excess of Na2C03 remaining with N/10 HCl and calculate the quantity of " soda " required to dispose of the CaSOi which caused the " permanent " hardness. As already stated, water results are best reported in " parts per million," but at times a demand will be made for a report in " grains per U. S. gallon," and to facilitate conversion from one form to the other the table given on the opposite page was prepared. For ordinary use it is near enough to remember that " grains per gallon " multiplied by 17 equals " parts per million," ii8 EXAMINATION OF WATER. CONVERSION OP "MILLIGRAMMES PER KILOGRAMME" INTO "GRAINS PER U. S. GALLON" OF 231 CUBIC INCHES. One U. S. gallon of pure water at 60° F., weighed in air at 60° F., at atmospheric pressure of 30 inches of mercury, weighs 58334.94 grains.* Parts per Grains per U. S. Gallon. Parts per Grains per , Parts per Grains per Million. Million. U. S. Gallon. Million. U. S. Gallon. 1 0.053335 36 2.100058 71 4.141781 2 0.116670 37 2.158393 72 4.200116 //s 0.175005 38 2.216728 73 4.258451 '4 0.233340 39 2.275063 74 4.31.6786 5 0.291675 40 2.333398 75 4.375121 6 0.350010 41 2.391733 76 4.433456 7 0.408344 42 2.450068 77 4.491791 8 0.466679 43 2.508402 78 4.550126 9 0.525014 44 2.566737 79 4.608461 10 0.583349 45 2.625072 80 4.666796 11 0.641684 46 2.683407 81 4.725130 12 0.700019 47 2.741742 82 4.783465 13 0.768354 48 2.800077 83 4.841800 14 0.816689 49 2.858412 84 4.900135 15 0.875024 50 2.916747 85 4.958470 16 0.933359 51 2.975082 86 5.016805 17 0.991694 52 3.033417 87 5.075140 18 1.050029 53 3.091752 88 5.133475 19 1.108364 54 3.150087 89 5.191810 20 1.166699 55 3.208422 90 5.250145 21 1.225034 56 3.266757 91 5.308480 22 1.283369 57 3.325092 92 5.366815 23 1.341704 58 3.383427 93 5.425150 24 1.400039 59 3.441762 94 5.483485 25 1.458373 60 3.500097 95 6.541820 26 1 . 516708 61 3.558432 96 5.600166 27 1.575043 62 3.616766 97 5.658490 28 1.633378 63 3.675101 98 6.716825 29 1.691713 64 3.733436 99 5.775169 30 1 . 750048 65 3.791771 100 5.833494 31 1.808383 66 3.850106 32 1.866718 67 3.908441 33 1.925053 68 3.966776 34 1.983388 69 4,025111 35 2.041723 70 4.083446 * See article by the author on "The U. S. Gallon" in Ani.DruagUI,3a.nvia,vy, 1888. CHAPTER III. BACTERIOLOGICAL EXAMINATION OF WATER. The water 6xpert of to-day cannot afford to take the risk of basing his opinion upon any one form of in- quiry alone, and it behooves him to make himself familiar with all the means of throwing light upon the question at issue. In consideration of the magnitude of tlie bacterio- logical field, it is manifestly out of the question, in a book of this scope, to go very far beyond a simple enumeration of the bacteria present in a cubic centi- metre of the water under examination, supplemented by a determination of the probable presence or ab- sence of germs derived from an intestinal source, thus leaving the problem of final differentiation to be dis- cussed by writers upon bacteriology.* These elementary applications of the science are of especial value for the testing of filter^ and watching any variation in their efficiency. For such a purpose the simple count of germs per * The technique of such processes as "staining," "hanging drop, ' ' etc., will be found in any text book of bacteriology. 119 120 EXAMINATION OF WATER. cubic centimetre is most valuable, and differentiation is a secondary matter; the assumption being a just one that a filter which will remove the harmless bac- teria may be trusted to take out the objectionable ones as well. As to the value of the "count of bacteria per c.c." in the general cases outside of filter examination, much has been asserted to show its uselessness; and for "single-sample" examinations the objections are doubtless well taken, but for "comparative tests," such as watching the distance to which a stream of sewage is felt in a lake, or observing the relation be- tween sedimentation and river flow, there is no ques- . tion as to its being of great value. For instance, it was through such means that Dr. Shuttleworth, of Toronto, was led to the discovery that a section of the conduit, leading from the distant intake, was broken, and that, consequently, the city supply was being taken from within the zone of pollu- tion much nearer shore.* For the accomplishing of the determinations that are here proposed the following culture media should be carefully prepared and kept ready at hand.f Bouillon. — ^Take 500 grammes of lean beef, chop it *Jr. N. E. Water-works Asso., June, 1896, 211. t The formulse for culture media are largely based upon the recommendations of the special committee of the American Public Health Association. BACTERIOLOGICAL EXAMINATION OF WATER. 121 fine, and let it soak overnight in one litre of water in a cool place. Strain through a cloth with the aid of gentle pressure and make up to one litre with water. Add 10 grammes of peptone (Witte's). Heat in a double-walled "oatmeal-boiler" until the peptone is dissolved. Should the medium not be clear, cool somewhat, add the white of an egg, bring to 90° C. and filter while hot. The proper reaction of the finished medium should be +1 per cent (i.e., an acidity equal to what would be produced by the addition of 10 c.c. of normal hydro- chloric acid to one litre of the medium made neutral to phenolphthalein) . In order to secure such a reaction place 5 c.c. of the medium in a porcelain dish, add 45 c.c. distilled water and 1 c.c. of a solution of phenolphthalein (0.5 gramme phenolphthalein in 100 c.c. of 50 per cent alcohol). Titrate (while hot) to the neutral point with N/20 NaOH or with N/20 HCl (the former will be the solution most commonly required), and from these data calcu- late the amount of normal HCl (or normal NaOH) re- quired to be added to the bulk of the medium in order to bring it to the desired degree of acidity, namely, + 1 per cent. The said normal acid or alkali having been added, the " bouillon " is placed in test-tubes plugged with cot- ton, 10 c.c. in each tube. The cotton plug is then cov- 122 EXAMINATION OF WATER. ered with a small sheet of " tin-foil " to prevent evapora- tion, and steriHzation is accomplished by heating in an " Arnold steriHzer " for thirty minutes on three successive days. SteriHzation may be accompHshed by a single heat- ing in an autoclave to 15 pounds pressure (120° C.) for 15 minutes. This method is preferable. Keep the " stock bouillon " and all other stock media in a cool, dark, moist place, e.g. an ice-box. Nutrient Gelatin* — Take 500 grammes of lean beef, chop it fine, and let it soak overnight in one litre dis- tilled water in a cool place. Strain through a cloth and make up to one litre with distilled water. Add Gelatin (best French) 120 grammes Peptone (Witte's) 10 Heat in a double-walled " oatmeal-boiler " at a tem- perature of 60° C. until all is dissolved. Add the white of one egg, previously shaken up with about its own bulk of water, or else add 5 grammes of dried egg albumin powder, and stir thoroughly. Cover the mix- ture and keep it at 90° to 92° C. for 10 minutes. Filter, with the use of the hot-water funnel. Place * Miquel uses no beef in his medium. It consists of gelatin and peptone as above with 5 grammes of salt added. He makes it neutral to litmus with NaOH. It becomes slightly alkaUne on sterilizing. BACTERIOLOGICAL EXAMINATION OF WATER. 123 5 c.c. of the filtered medium in a porcelain dish; dilute the same with 45 c.c. water; titrate (while hot) with N/20 NaOH (or HCl) solution, as in the case of the prepa- ration of " bouillon," and from the data so obtained calculate what addition of normal HCl (or NaOH) should be made to the main bulk in order to carry its reaction to the desired point, namely, + 1 per cent. Pour the finished jelly into "Miquel" flasks or test- tubes, 10 c.c. in each. Plug the vessels with cottn and sterilize and store as described under "bouillon." It is best to make but a small quantity of any of the culture media at a time, as they do not keep well in stock. Dextrose Bouillon ("Smith's Solution"). — Prepared the same as the ordinary " bouillon " except that 10 . grammes of pure dextrose are added with the peptone, and except that 3 grammes of Liebig's beef extract* are used in place of the fresh beef. Its reaction should be neutral. Sterilize as usual. The best vessels in which to store " dextrose bouillon " are the " Smith fermentation-tubes " in which it is to be used (see page 147). Lactose Bouillon. — Prepared as above, substituting lactose for dextrose. Lactose Bile. — Medium " consists of sterilized un- * Chester prefers "Liebig's Extract" to fresh beef for use in all media, as being easier to handle and because "it contains no muscle sugar." — "Manual of Determinative Bacteriology." 124 EXAMINATION OP WATER. diluted fresh ox gall (or a 10 per cent solution of dry fresh ox gall) to which has been added 1 per cent of peptone and 1 per cent of lactose."* Sterilize. Agar-agar. — ^Although plate cultures for water ex- amination are best made by the use of "nutrient gelatin," it is sometimes convenient to employ a medium with a higher melting-point. It must be noted, however, that "counts" of colonies growing upon agar must not be compared with those upon gelatin; the latter medium being more favorable to an increased growth. To make one litre of agar-agar take — A. Chopped meat, 500 grammes. Water, 500 c.c. Mix and place in cool place overnight, then strain through cloth. Add Peptone (Witte's), 10 grammes. B. Agar-agar, 12 granames. Water, 500 c.c. Place B in octoclave, run up to about 30 pounds of pressure, put out flame, and allow to cool until below 100° C. before opening. Let the solution of agar cool still further to about 75° C, and then mix A and B. Add 5 grammes dry egg albumin powder. Bring to a boil for about three minutes, adjust reaction to * Jackson, Am. Pub. Health Assoc, Nov., 1908. BACTERIOLOGICAL EXAMINATION OF WATER. I2S + 1 per cent, and filter. The product is an absolutely clear jelly, which never forms any precipitate.* Place the finished medium in tubes, 10 c.c. in each, and sterilize as usual. Lactose Litmus Agar. — ^Agar prepared as above, but with one per cent lactose added and made neutral to phenolphthalein. It is melted and tinted slightly blue with sterile litmus solution immediately before using. The sterile litmus solution (5 per cent) is conveniently kept for use in a dropping bottle similar in form to those used for cedar oil. About 0.2 c.c. of the solution will give a proper depth of color to the 10 c.c. of lactose-agar used. Nitrate Solution. — Dissolve 1 gramme of peptone and 0.2 gramme of KNO3 in a litre of water. Place the solution in cotton-plugged flasks (50 c.c. in each) and sterilize. Dunham's Solution (For Indol test). — Dissolve 10 grammes of peptone in a litre of water. Neutralize if necessary. Place the solution in cotton-plugged flasks (50 c.c. in each) and sterilize. Empty glassware is sterilized by a single heating for one hour at 160° C. The best piece of apparatus to use for this purpose is the Lautenschlaeger sterilizer illustrated on page 126. ♦The above method for preparing agar-agar is due to Dr. M. P. Ravenel. (/. Applied Microscopy, i. 106.) 126 EXAMINATION OF WATER. The 1-c.c. pipettes used for the measurement ol the water should be plugged with cotton near the end (see Fig. 5), which is placed in the mouth; tha pipette should then be placed in a suitable tube con- FiQ. 4. Fig. 5. taining a cotton plug in its open end, and the whole sterilized. The writer employs also cylinders of copper with close fitting caps, wherein a number of pipettes can be placed during sterilization. Water-sam'ples for bacteriological examination are most commonly taken in 100-c.c. glass-stoppered bottles. The stopper and neck are covered with tin foil, secured in place by several thicknesses of cotton cloth carefully fastened, and the whole enclosed in a BACTERIOLOGICAL EXAMINATION OF WATER. 127 cylindrical copper box and sterilized in the hot-air steril- izer. Samples are also conveniently taken in bulbs of glass with long thin stems, similar to the stock articles in use for specific-gravity determinations. These bulbs can be steriUzed by the direct Bunsen flame and sealed while hot. Upon afterwards breaking off the point of the stem under water the water will enter the vessel because of the partial vacuum, and the stem can be at once resealed by using a candle-flame and a blow-pipe. Such bulbs are very convenient for taking deep sam- ples, as the point of the stem can be broken by a separate string while the bulb is held by the sinking-apparatus. During transportation the vessels filled with water- samples should be packed in ice, but it is very much better to make the enumeration sowings on the spot, rather than risk changes due to delay. Samples for bacteriological work are more quickly damaged by keeping than are those intended for chem- ical analysis; thus: SPRING-WATER, TROY, N. Y. Kept at room temperature. November 10 830 bacteria per c.c. " 12 8,12s " " " " 13 9,433 " " " " 15 12,740 " " " 128 EXAMINATION OF WATER. Much more striking instances are given by Miquel. Thus for the Dhuis water: Temperature. Bacteria per e.c. 12 noon 16.6°C. 57 1.30 P.M 19.5°" 143 3 P.M 20.9°" 456 For Vanne water: Temperature. Bacteria per c.c. Immediate 17° C. 56 After 24 hours 21 .2° " 32,140 Also for Vanne water: Immediate 15.9°C. 48 After 2 hours 20.6° " 125 " 1 day 21.0°" 38,000 " 2 days 20.5°" 125,000 " 3 days 22.3° " 590,000 Deep-well water (Frankland) : Immediate 20° C. 7 After 1 day 20° " 21 " 3 days 20° " 495,000 The last instance shows that multiphcation of bac- teria is not to be accounted for by a simple increase of temperature. BACTERIOLOGICAL EXAMINATION OF WATER. 129 As has been already stated, it is exceedingly im- portant to keep water-sampleg at freezing tempera- ture during transportation to the laboratory. Germs do not commonly multiply at such a temperature, but, as has been shown in France, this does not hold good for waters heavily charged with bacterial food. In one instance "sea-water, constantly maintained at 0° C, changed in bacterial contents from 150 to 520 per cubic centimetre in 24 hours." It may be noted here that great cold is not surely fatal to germ-life although the number of germs present per c.c. will decrease. The author submitted cultures of ordinary bacteria to the temperature of sohd carbon dioxide during many hours without causing their entire destruction, and more recently Ravenel has exposed them to the temperature of liquid air ( — 312° F.) with like result.* Sowing for the Total Count. — Thoroughly shake the sample and transfer 1 c.c. of the water, by means of a stenHzed pipette, to a sterile Petri dish. A tube of nutrient gelatin is hquefied by immersing the tube in warm water at 35° to 40° C, and the open end of the tube is held for a moment in the Bunsen * Medical News, June 10, 1899. 130 EXAMINATION OF WATER. flame. The melted jelly is then quickly poured into the Petri dish, and mixed with the water by tilting the dish forward and back. After the jelly has again hardened the dish should be maintained in a moist, dark closet, or incubator, at a temperature of about 20° C. When " agar " is employed, melt it at 100° C. and then cool it to about 42° C. before sowing. Each individual bacterium, finding itself imbedded in material supplying abundance of food, proceeds to surround itself by a multitude of its offspring, until at length the " colony " so produced becomes large enough to be seen by the naked eye. These colonies, each of which corresponds to one original bacterium, are of various sizes, as shown in the illustration on page 133. Some of them do, and others do not, liquefy nutrient gelatin. None of them liquefy " agar." Petri dishes which contain sowings in "agar" may be inverted during development to avoid the spreading of surface condensation-water. Some workers prefer to employ porous earthenware covers for the Petri dishes. Such covers absorb the water of condensation,* but they also tend to dry the medium. * Hill, J. Med. Besearch, 1904, N. S., 8, p. 93. BACTERIOLOGICAL EXAMINATION OF WATER. 131 For the sowing of water-samples some workers employ, in place of Petri dishes, conical " Miquel " flasks (Fig. 6), usually 2\ inches in diameter at the bottom, with a, tubulated glass cap, ground at the joint. The tubula- tion is plugged with cotton. Such flasks receive 10 c.c. each of the culture-jelly when it is first made, and are kept in stock like the test-tubes. Taken to the field, they receive, on the spot, the measured amount of water, and the chances of contamination during Fig. 6.— Miquel Flask, transfer, and of multiplication during the journey of the water-sample to the laboratory, are thereby avoided. It should be said that Petri dishes are also capable of being used in the field in similar manner. Should the water contain over 200 bacteria per c.c. the volume operated upon should be diminished. In place of sowing a fraction of a c.c. of water, the the " dilution method " should be employed. One c.c. or ten c.c. of the water are diluted 132 EXAMINATION OF WATER. to 100 c.c. with sterilized water and then 1 c.c. of the mixture is sown in the, medium. This is Miquel's favorite method. Of course this dilution must be done with great care, as any error is mul- tiplied. Hill found that "the actual size of the individual colonies increased in proportion as the dilutions rose : i.e., in a plate containing 3,000 colonies, the colonies were very small; in a plate containing half a dozen colonies, the colonies were relatively very large. This suggested that the discrepancy was due chiefly to overcrowding. If the original sample contains not over 200 bacteria, they wiU grow in a plate without introduction of those factors of food exhaustion or direct antagonism, which we place together under the term overcrowding. We regard as reliable only the not overcrowded plate, whichever that may be; recognizing it in the fact that the count lies between 40-200, ignoring all others, because the standard plate, containing the standard 10 c.c.'s of standard medium, will not support more than about 200 colonies without detriment to the weaker forms."* Counting the colonies of bacteria is undertaken forty- eight hours after the sowing, according to the ofiicial * H. W. HiU, Am. Pvh. Health Assoc, 1907, 300. PETRI DISH SHOWING COLONIES OP BACTEEIA. (OHLMULLER.) 133 BACTERIOLOGICAL EXAMINATION OP WATER. 135 German regulations,* and this period is also adopted by the Am. Public Health Association, but it is well in some cases to delay it longer if there be no danger of the colonies growing into each other and thus confusing the count. Of course what is required is the maximum count, and good judgment must be exercised as to when is the best time to secure it. For purposes of comparison in routine work (and usually comparison examinations are the most important form of water investigations) the above time, viz., forty- eight hours, will be found the proper interval between the sowing and the final counting of the colonies. Miquel does not usually count inside of two weeks, and at times waits even longer. Basing his estimate upon the examination of very many waters, he gives the following figures as showing the number of colonies visible on successive days follow- ing the sowing, calling the count on the fifteenth day 1000 :t 1 day 20 2 days 136 3 " 254 4 " 387 * P. Frankland, "Bact. Purification of Water," 29 and 73. t Miquel et Cambier, Traite de BacUriologie afpUquie. 136 EXAMINATION OF WATER. 5 days 530 6 " 637 7 " 725 8 " 780 9 " 821 10 " 859 11 " 892 12 " 921 13 " 951 14 " 976 15 " 1000 When sowings are naade in the field the warm weather of summer, or the heat of the expi-ess car in winter, may melt the gelatin and spoil the count. Many workers prefer to make use of agar for that reason. Agar counts are commonly somewhat smaller than those on gelatin at the same temperature, although all do not find them so. Professor Wesbrook reports his experience as just the reverse. The colonies appear to grow more slowly, however, and it is well to extend the time before counting agar plates. This may be readily done, as agar is not liquefied by any bacteria, although sundry of them liquefy gelatin. When it comes to a comparison of the counts between gelatin at 20° C. and agar at 37° C, then the difference is marked indeed. Bacteriological examination or.water. 137 The higher temperature is very fatal to common water forms, while those of intestinal type are favorably influenced. It must not be assumed that the high temperature count means an accurate enumeration of objectionable organisms, for sundry perfectly harmless germs will grow at blood heat; but there is undoubted value to be derived from a comparison of the two counts in question. Such irregular results as the following will be noted : Gelatin at 20° C. Agar at 37° C. 5268 495 240 88 37071 837 121 21 1400 82 5283 12 2033 1000 McWeeney and Savage consider that for good waters the count on agar at 37° C. should not exceed one-tenth of that on gelatin at 20° C. When the number of the colonies is large, countmg must be done with the aid of a ruled glass plate. The best device for this purpose with- which the writer 1 38 ^ EXAMINATION OF WATER. is familiar is the "Miller-McPherson" counting appara- tus, which needs but little explanation beyond what is given in the illustration shown on page 1^0.* The "Wolffhugel" device, which is still so commonly employed, has the disadvantage of not firmly fixing the "Petri" dish in place, so that there is no small danger of counting the same colonies more than once. Nor is it possible to make use of a " Miquel " flask as a substitute for the "Petri" dish, if the "Wolffhugel" counter be employed. The new apparatus is so arranged as to have the ruled glass plate a fixture, while the "Petri" dish rests upon a movable ebonite plate, which is raised or lowered by the wheel beneath it actuating a hollow screw. The dish may be thus always kept firm against the ruled plate, with no chance of slipping, and more, over it will be always in focus no matter what may be its thickness. The count should be made with a lens magnifying at least five diameters. The entire plate should be counted. Both Petri dishes and Miquel flasks are counted bottom upwards. When a Miquel flask is used the neck of the in- verted flask passes through a hole in the ebonite plate and into the hollow screw, while the wheel beneath raises the bottom of the flask against the * A good and simple modification of this has been made by Caird. BACTERIOLOGICAL EXAMINATION OF WATER. 139 ruled plate the same as when a Petri dish is em- ployed* The " count " of bacteria per c.c, although of prime importance for filter testing is of secondary value for the rating of untreated waters. No hard and fast standard of comparison can be given which will prove satisfactory, although sundry hav6 been pro- posed. The following is by McWeeney : * Pure water: Gelatin, 20° C. Colonies few or many; liquefiers few; chromogenic and slow-growing forms numerous. Agar, 37° C. Sterile or neai'ly so. Dirty water: Gelatin, 20° C. Coloniea at least 500; Uquefiers numerous. Agar 37° C. Not to exceed one-tenth of the count on gelatin. Sewage: Gelatin, 20° C. Colonies innumerable; lique- fiers many. Agar 37° C. Colonies innumerable; small and gray. The number of bacteria per cubic centimetre in water-samples taken from the same source at differ- * /. Boy. Ban. Inst., 31, 367. 140 EXAMINATION OF WATER ent times will greatly vary with the season and changes in local conditions. Thus the Hudson River water Fig. 7. sampled at Troy showed the following variation in bacterial contents during the colder half of the year; similar results for a Rensselaer County spring- water are also given : Hudson River. Spring. October 1,487 158 November ] 8 128 '^^^ December 1,463 1,620 January 4,022 2,519 February 3,322 166 March 8,520 April 476 ^ 117,665 The influence of high water in the river is well shown by the difl'ee:ce letv\een tl:e eaily and late BACTERIOLOGICAL EXAMINATION OF WATER. 141 April samples. Surface-washing is the cause of such an increase. The effect of melting snow, and conse- quent surface-washing, is also shown in the March sample of spring-water. In general it may be said that so long as a river is fed by springs, that is, during the hot months, the bacteria tend to remain low in numbers, but with the advent of floods germ-life increaees in quantity, be- cause of the washing of the surface of the ground by heavy rainfall and melting snow. During the period when severe frost ties up all surface sources the bac- teria again diminish in numbers. Differentiation of species, as has already been said, must be left for discussion to writers upon general bacteriology; but a moment may bo properly spent here upon the often broached topic of the recognition of the typhoid germ in water, and we should also add a consideration of the diagnostic value of the presence of BqcHIus coli communis. Laws and Andrew es in their report to the London County Council show that the chance of discovering B. typhosus in sewage is small. They entirely failed to find it in London sewage. They examined the sewage flowing (without dis- infection) from the Eastern Hospital at'Hbmeston, 142 EXAMINATION OF WATER. which same received the dejections of forty typhoid patients. Out of a whole series of samples examined from this latter source only two colonies of B. tyohosus were differentiated with certainty.* Similar experience was recorded by other observers, and consequently search for the typhoid germ in water became unusual. Of late attention has been again directed to this determination, but even though we possessed a method of proving with certainty the presence or absence of the typhoid bacillus, such knowledge would not greatly aid us. The information we desire is not alone the condition in which a water is to-day, but we wish to be also advised of the chances of its specific pollution to-morrow. In short, we want to guard against the use of a water which may become the carrier of disease organisms even though none be present at the moment of examination. The present position of this question is tersely summed up by Dr. W. H. Welch: " We possess no satisfactory method for the deter- mination of the presence of the typhoid bacillus in water. With our present methods the most which can be expected from the biological examination of water as regards this question is the determination, * See Rafter's, "Water of Lake Erie," page 14. BACTERIOLOGICAL EXAMINATION OF WATER. 143 not of the actual presence of the typhoid bacillus, but of the possibility or probability of its presence. Our principal guide at present in drawing conclusions as to the possible presence of the typhoid bacillus in suspected drinking-water is the recognition of fsecal bacteria, and more particularly of members of the colon group."* We seek, therefore, some index of faecal pollution which will indicate sewage inflow, even though such inflow be from sources which for the time being are not pathogenic. This brings us to a query regarding the diagnostic value of the " colon group." The Bacillus coli communis has its habitat in the intestines of man and the warm-blooded animals. In small numbers, it is of very wide distribution, and it is doubtful if a surface water could be found that would not furnish it, provided a sufficiently large volume of the water were examined. " Many excellent water supplies derived from upland surfaces would have to be condemned if we were to insist on the absence of B. coli from 10 c.c. Even after storage in open reservoirs B. coli is often present in considerable numbers, owing to the numerous sea-gulls that frequent such sheets of water." f E. G. Smith { has found it upon standing grain. It has also * /. Am. Pub. Health Assoc, xx. 502 t J. Boy. San. Inst, xxxi, 269. t Science, xxi. 710. 144 EXAMINATION OF WATER. been discovered in the excreta of fish,* but that might be accounted for by its presence in the water whence the fish came. Therefore it is its persistent presence in 1 c.c. samples of a water rather than its being occa- sionally found in those of larger bulk, that gives evidence of faecal pollution. " It is an assumption to say that B. coli communis does not occur in abundance in organic matters other than animal excreta." f It is certainly the author's experience that the " colon group " is widely distributed, he having found it in waters that a sanitary " survey " would unques- tionably pronounce pure; but it cannot be denied that its persistent presence in small samples is an indication of pollution that must not be overlooked; and, moreover, the proof of its absence serves to mate- rially aid in formulating an opinion in favor of the purity of a water. Sowing more than 1 c.c. of the water is rarely neces- sary because the presence of B. coli in a greater volume is not of especial diagnostic value, considering the wide distribution of the organism. Water which persistently shows B. coli in 1 c.c. sowings is of very questionable character, andj should similar results be found when operating with sowings of 1/10 c.c, the water should be condemned. * Hill, "Public Water Supplies," p. 28. t Analyst, xxii. 122 and 123. BACTERIOLOGICAL EXAMINATION OF WATER. 145 The Mass. Board of Health * found that for the six yeara 1898-1903 the raw water of the Merrimac River contained B. coli in 98.7 per cent of all the 1 c.c. samples examined, and that the average count of the organism per c.c. during that period was fifty eight. Fewer were found in winter than during summer, a fact probably due to dilution by storm water. Should it be decided to search for B. coli in 10 c.c. or 100 c.c. of the water, the volume selected is " enriched " as per (a), page 153, and the regular tests made from such " enrichment." Sundry bacteria are capable of inducing a fermenta- tive action, with evolution of gas (CO2 and H), or acid, or both, when sown in a medium containing one per cent of sugar. Dextrose. Acid. Gas. Lactose. Acid. Gas. Dulcite. Acid. Gas. Acid. Saccharose. Gas. B. typhosus t B. paratyphosus. . B. coli B. paracoli B. acidi lactici B. lactis aerogenes B. cloaca + + + + * Report of 1902, page 247. t / Soc. Chem. Ind., xxx. 323. 146 EXAMINATION OF WATER. To these may be added B. communior which gives gas in each of the four sugars. The following graphic arrangement is abstracted from the report of the water committee of the Am. Pub. Health Asso.: B. colt group. Dextrose + Lactose + '.,': Dulcite+ Dulcite — B. communior B. (rrogenes B. communis B. acidi-lactici Saccharose + Saccharose— Saccharose + Saccharose — B. communior B. communis B. arogenes B. acidi-lactici " The entire group is typical of the presence of faecal matter when water or sewage examinations are to be considered." The persistent presence of these germs in a sample of water is evidence of its contamination by intestinal products from man or the higher animals. When water samples have to be shipped long distances Wesbrook's method of sampling for B. coli is to be recom- mended.* To tubes containing about 1 c.c. of plain agar, melted and allowed to cool to 43° C, add 1 c.c. or * U. S. Water-Supply Paper, No. 193, page 157. BACTERIOLOGICAL EXAMINATION OF WATER. 14J 1/10 c.c. of the water. Mix, allow to solidify and ship. Upon reaching the laboratory break up the mass into fine particles with a thick, sterile wire; add a tubeful of plain bouillon, and mix; incubate at 37° C. for twelve hours and make the routine tests by inoculations from this instead of using the water directly. Tests for B. coli communis. — 1. To each of five Smith's " fermentation-tubes," charged with sterile dextrose or lactose bouillon (or lactose bile), add 1 c.c. of the water under examination, or else an inoculation from one of the Wesbrook tube cultures mentioned above. Mix by tilting the tube, and place in the incu- bator at 37° C. for three days. Incubate in like manner five more fermentation- tubes which have been sown with 1/10 c.c. of the water, measured by the dilution method (page 131), or inoculations from the 1/10 c.c. Wesbrook tubes men- tioned above. If any gas-forming bacteria be present, gas will collect in the closed hmb of the tube, and some knowl- edge of the numbers of such organisms present may be gained by observing how many of the two sets of tubes show the reaction.* * See the original article by Dr. Theobald Smith in The American Journal of the Medical Sciences, for September, 1895. 148 EXAMINATION OF WATER. If no gas be formed B. coli is absent. 2. The amount of gas produced is stated in per- centages of the length of the closed limb. B. coli com- FiG. 8. SMITH FBRMENTATION-TUBE. munis will usually fill this closed limb about half full of gas. A most convenient little device for reading the gas percentages was suggested by Frost,* and is illustrated * J. Applied Micro., Feb., 1899. BACTERIOLOGICAL EXAMINATION OF WATER. 149 iu Fig. 9. A sheet of cardboard or metal ruled in converging lines is placed in the angle between the bulb and the closed limb of the Smith tube. The top of the closed limb having been made to coincide with so- 100- FiG. 9. the upper or zero hne, the percentage of gas present can be read directly. As B. coli usually ceases to evolve gas by the end of the first day. the total gas will often be diminished in volume on the third day, due to solution of CO2 in the liquid present. Too little gas or too much would not point to- wards B. coli, especially if the other tests were nega- tive. Jordan reports finding the gas volume for B. coli as low as 10 per cent and as high as 75 per cent in some instances. Others have reported it as high as 90 per cent. 150 EXAMINATION OP WATER. In the original experiments by Smith the total gas averaged 52 per cent for B. coli, and about 23 per cent for certain "transitional forms"; while for B. lactis aerogenes and B. cloacce the average ran as high as 76 per cent. Sowings, made by the writer, from pure cultures gave the following averages: Total gas 35 . 3 per cent Gas formed during first day (as p. c. of total gas) . . 100 Ratio of H to CO2. 71 to 29 3. B. coli forms its gas rapidly, evolving most (often all) of it within the first twenty-four hours. If, however, the coli should be attenuated by reason of the pollution being not recent, then the rate of gas formation would be slower. Sundry other " gas- formers " also act more slowly. Therefore, note the volume of gas formed during each of the three days. i. Dr. Theobald Smith holds that B. coli forms a gas having the approximate composition of H:C02::2:1. The r£.tio found by the author is given above. With sundry other gas-producers the carbon dioxide is the greater. To determine the CO2, fill the bulb to overflowing with solution of KOH; close the orifice with the thumb and tilt the tube a number of times to cause the KQH to absorb BACTERIOLOGICAL EXAMINATION OF WATER. 151 the^ COa- The remaining gas is rated as hydrogen, although it contains also a httle nitrogen and methane, as shown by Pennington and Kiisel.* 5. The liquid in the bulb of the fermentation-tube must be distinctly acid to indicate B. coli. 6. Sow 1 c.c. of the water in lactose htmus agar and incubate at 37° C. for twenty-four hours. A count of the red colonies will give an approximate indication of the number of B: coli present. There being other " acid-forming " organisms such count is not accurate. 7. Indol (CgHrN) is a compound belonging to the aromatic series, which produces a red color when acted upon by nitrous acid. It is formed by the breaking up of peptone by the action of putrefactive bacteria, including B. coli. To test for its presence place about 20 c.c. of the water, together with 50 c.c. of sterile Dunham's solu- tion, in a sterilized cotton-plugged flask, and keep the same in the incubator at 37° C. for four days. The high temperature will destroy common water- bacteria, but will encourage the growth of the colon group. Place 2 c.c. strong sulphuric acid and 2 c.c. of the stronger sodium nitrite solution (see page 45) in a 100-c.c. " Nessler " tube. * J. Am. Chem. Soc.^ xxii. 560. IS2 EXAMINATION OF WATER. Dilute with 50 c.c. water, cool, and then pour in the previously cooled, incubated culture prepared above. A red coloration, forming within half an hour, indicates indol, and is an additional evidence of the presence of B. coli. When made directly from the water itself this test is much less valuable than when it is made by transfer from the fishing of red colonies as on page 155. A num- ber of " spore-formers " will give the indol test as well as B. coli. 8. Inoculate " nutrient gelatin " from the incubated Smith's tubes. Let the plates develop as usual and observe if the colonies are whitish and non-liquefying. Such characteristics point to B. coli. 9. If inoculations from the colonies obtained in 8 be examined as " hanging-drop " cultures, the bacilli will be found to be slightly motile if they be B. coli. This motility may be manifested, however, by only a portion of the bacilh present in the field, and its in- tensity will be far less than that shown by the t3^hoid bacillus. 10. Add about 20 c.c. of the water to a flask of " nitrate solution " and place in the incubator for four days. Test the contents of the flask at the end of that time for " nitrite," as directed on page 46. B. coli reduces the nitrate to nitrite. BACTERIOLOGICAL EXAMINATION OP WATER. 153 To recapitulate, the B. coli communis would be indi- cated should the tests show: 1. Gas in the " Smith " tube. 2. Gas measures 20 to 70 per cent of closed arm. 3. Gas about 30 per cent CO2 (not over 50 per cent). 4. Gas all, or nearly all, formed in first twenty-four hours (except in cases of attenuated organisms). 5. Closed arm turbid. 6. Bulb strongly acid. 7. Colonies in gelatin white and non-liquefying. 8. Hanging drop shows slight motility. 9. Gives " indol " reaction. 10. Reduces nitrates to nitrites. The foregoing have been termed the " presumptive tests " for B. coli. Longley and Baton * have shown that they err on the side of safety. Thus out of 794 instances where the " presumptive tests " indicated the presence of B. coli, the use of more exhaustive methods, confirmed the finding only 529 times. That is the presumptive tests were accurate 67 times in a hundred. Should more careful search for B. coli be required proceed as follows.f (a) Add some of the water to about six times its bulk of plain " bouillon " in a cotton-plugged flask * /. Infect. Diseases, iv. 412. t Practically the method suggested by Professor F. F. Wesbrook. 154 EXAMINATION OF WATER. and incubate at 37° C. for 12 hours. This is termed " enrichment." Too prolonged a period of " enriching " might cause an overgrowth of other organisms, with a masking of the B. coli reactions. Such overgrowth is at times noted when large sowings of the water are under examination. Thus 1 c.c. of water might show B. coli while negative results were obtained for volumes of 10 c.c. In this connection Whipple has very aptly said : " Whenever a positive test tor B. coli is obtained with a small quan- tity of water, it is safer to assume that larger quantities will also give a positive test, than to assume that the positive test in the small quantity was accidental." * (b) Sow from (a) into five " Smith-tubes " contain- ing " lactose bouillon," incubate 24 hours. If no gas forms transfer to another " Smith- tube " and repeat the incubation. Should no gas appear in 24 hours after such transfer report B. coli absent. (c) From the " gas tubes " of (b) sow in lactose litmus agar and incubate 24 hours. (c') Should no red colonies form in (c) repeat the sowing from (b) and incubate 24 hours. (d) Fish (c) or (c') red colonies to : 1. Plain agar slant — incubate 24 hours — smear and stain for form. * Am. Pub. Health Asso., 1902. BACTERIOLOGICAL EXAMINATION OF WATER. 155 2. Plain agar slant— incubate 48 hours — smear and stain " no spores." Cultures of B. coli will fail to grow if heated for 15 minutes at 80° C, showing it to be a non-spore former. 3. Plain bouillon — incubate 24 hours- — " hanging drop " gives slight " motihty." (Probably but not necessarily.) From the growth on the plain agar slant (1) transfer to— 4. Lactose bouillon — ^incubate 48 hours — gas reaction. Total gas should be 20-70 per cent of tube length. If gas volume be small resow to another tube. Gas formula should be H>C02. Bulb reaction should be acid. .5. Dunham's solution — ^incubate 4 days — ogives indol reaction. 6. Nitrate solution — ^incubate 4 days — ogives nitrite reaction. The use of " Lactose Bile " as a substitute for the older forms of sugar media gives very excellent result?. It is especially good as a substitute for dextrose or lac- tose bouillon. All the known members of the colon group "give positive gas tests with lactose bile while no other known species gives such a test except two very rare chromo- genie forms and B. welchii, a pathogenic bacterium also of fsecal origin." * * Report Am. Pub. Health Asso., 1912. 156 EXAMINATION OF WATER. Sterilizing a water by heat is not so easy as most people imagine. Absolute sterility can be attained in about forty-five minutes by heating the water, under pressure, to 115° C. Ordinary boiling for half an hour will destroy about 99 per cent of all bacterial life, and fortunately that which remains is entirely harmless. No pathogenic germs are capable of resisting such a temperature for half an hour. Experimenting with Seine water, which contained, at the ordinary temperature of 22° C, 848 bacteria per cubic centimetre, Miquel found the following de- crease in numbers of organisms as the temperature was raised : Water maiatained 15 Minutes at Bacteria per c.c. remaining. 43° C 640 50°" 132 60°" 40 70°" 27.2 80°" 26.4 90°" 14.4 100°" 5.2 For the enumeration of organisms not bacterial, in water, Prof. D. D. Jackson has devised a most valuable modification of the original Sedgwick-Rafter appara- tus. BACTERIOLOGICAL EXAMi:SAriON OP WATER. 157 The body of the filter is cylindrical and 2 inches in diameter. The distance from the top to the con- ical base is 9 inches. The small cylindrical prolonga- tion of the cone's apex is 2^ inches long and ^ inch Fig. 10. in diameter. A perforated rubber stopper, with its hole covered by a disk of fine bolting-cloth, is fitted to the smaller end of the funnel and about f inch of carefully screened fine sand (between 80 and 100 mesh) is poured into the narrow tube and wet down with distilled water. 158 EXAMINATION OP WATER., From 250 to 500 c.c. of the water under examina- tion are now permitted to filter through the sand. After the water has run through, the sand with the material strained off by it is washed into a test-tube by 5 c.c. of distilled water delivered from a pipette. The organisms, sinking in the test-tube much more slowly than the sand-grains, may be decantefi, with the water in which they float, into a second test-tube. From this decanted portion, after agitation, 1 c.c. is delivered by a pipette to the covered " counting-cell " (page 157), which it completely fills. This excellent device will be found of great service in recognizing and enumerating the various forms of life not bacterial, commonly met with in waters. For purposes of general differentiation recourse must be had to the writings of biologists who have made such work a specialty. Particularly valuable is the publication by G. C. Whipple, "The Microscopy of Drinking-water," published by John Wiley & Sons. APPENDIX A. (Extracted from a paper by the author in Science, n. s., Vol. XXI. No. 539, pages 648-653, AprU 28, 1905.) INTERPRETATION OF A WATER-EXAMINATION. Interpretation of a water-examination may be considered from two quite different points of view. It may mean the private weighing of evidence by the investigator himself, a procedure which finds expres- sion in his final opinion, or it may be his attempt, often a desperate one, to make analytical data in- telligible to an unscientific audience. The first is, of course, necessary and legitimate, the second is always of questionable policy, and frequently is an undeni- able mistake. In former days when 'standards' were still much in vogue, it was indeed a difficult matter for the analyst to escape from 'explaining' the analytical results to the assembled council of city fathers, and deep was the irritation felt by those 159 i6o APPENDIX. people that the figures given could not be ex- plained as clearly as they might have been were the case one involving the composition of an iron ore. Of course, those were times when the chemical data alone were considered sufficient whereon to formulate a pronoimcement as "to the quality' of the water, and it is to be admitted that the chemist himself fre^ quently found before him a very complex problem when he attempted to fit the. results of his analysis to the sanitary facts known to relate to the water in question. Bacteriology was as yet undeveloped and its bearing upon the ' sanitary survey ' had not as yet seen the light. A sample of water taken anyhow, in any kind of vessel and by anybody, was packed off to the chemist; all knowledge as to where it came from was intentionally withheld and a complete re- port of its sanitary qualities was confidently expected. Is it to be wondered at that in those early days a good share of discredit was cast upon a water-examina- tion? With the advent of bacteriology upon the scene, interest was greatly awakened. The new science promised much, and it seemed that the time had come for very positive and ready answers to the per- plexing questions which had bothered us so long Not so many years ago there met in the city of New York a sizable number of men who had gathered for the purpose of discussing the .merits of a chemical ^ APPENDIX. l6i versus a bacteriological examination of water. Advo- cates of the two methods advanced arguments in sup- port of their special views and offered illustrations calculated to expose the weak points of their oppo- nents. Unfortunately some remains of that spirit of rivalry still exist; but those who have the widest knowledge of the broad field of 'water-supply' readily admit that a competent investigation suitable for determining as to the purity of a city's water service cannot be undertaken in the laboratory of either the chemist or the bacteriologist or the microscopist alone, but must be the product of a draft upon the sciences represented by all three of those men, and must, fur- thermore, include the findings derived from what may be termed the 'sanitary survey.' I am speaking to scientific men, who need no instruction, but perhaps over their heads a few laymen may be reached who need it sadly. And now let it be asked, who are to be classed as the laymen? There is but one answer, to wit, all who have not given special study to this par- ticular subject. The field is so wide, is increasing at so rapid a pace, and covers such a variety of topics, that even those interested in this line of work have all they can do to keep in touch with the changes taking place about them. It is a mistake to underestimate the value of the 'sanitary survey,' by which we mean a thorough knowl- -l62 APPENDIX. edge of the source whence a water comes and of the opportunities for pollution, both constant and occa- sional, to which it may be exposed. In the writer's judgment it is not too much to say that if but one form of exa,mination be possible, the 'sanitary survey' should be the one selected. Then why not rest satisfied with such examination and permanently exclude chemistry and bacteriology from water cases; and why is not the city engineer an authority competent to express final judgment upon the matter in hand? In reply it may be said that because of the greatly increased pubhc interest in 'water-supply' which has developed during recent years, there has arisen a class of men who have devoted nearly their whole time to the consideration of water questions and who have brought to their aid a sufficiency of chemistry, bac- teriology, and microscopy to satisfy the requirements of their calling. Such men are, because of their special training and experience, enabled to view the question from more than one side, and their conclusions have, in consequence, greater scope. Although the writer believes that, taken alone, the 'sanitary survey' is, in the majority of cases, the most important form of examination, he begs not to be misunderstood. No amount of inspection could be substituted for APPENDIX. 163 the bacterial count in testing the efficiency of a filter- plant, nor would it be of value in warding off danger to a ground-water arising from the presence of an vuisuspected cesspool. As showing the utihty of the chemical examination take the following instance for example: A well which was most highly prized because of the cool, pleasing taste of its water was found loaded with chlorides and nitrates. Bacteriology gave no indication of pollution, and inspection of the sur- roundings was spurred into energy by the chemical results alone. Sewage, completely oxidized, from neighboring vaults was found to account for the ab- normal items in the analytical results. At the time of the examination no harm was being done, but would the owner of the well be justified in continuing to use such a water and take his chances of the purifying action of the soil being always effective? It is possible that some objection may be raised to the condemning of a water which shows as its only objectionable feature a chemical evidence of 'past pollution.' If the pollution be truly past and all of the nitrogenous organic matter be represented by nitric nitrogen; and, further, if bacterial examina- tion result favorably, then wherein lies the objection to the use of a water which, although once polluted, has regained its potable qualities? All pure waters, 164 APPENDIX. it may be contended, might be classed under such a head; for, after all, we are bound to use water over again sooner or later, contrive matters how we may. All this is true enough, but there is surely a prefer- ence as to the length of time between the date of present use and the period of 'past pollution.' It is true that every time we drink filtered river- water we are imbibing a purified sewage of greater or less concentration, and, with continued growth of our great cities, and the increased pollution of our watersheds, it would seem that the day is not far distant when a naturally 'safe and suitable' water shall become a thing of the past, and we shall be forced to employ a purified water as our only source of supply. Let it be remembered, however, that we can con- trol the artificial purifying devices of which we make use, and we can repair them should they at any time refuse their work. The case is quite different, however, when our safety lies upon the proper operation of those natural pro- cesses of purification which are Jaeyond our power to direct. Such purification, to be satisfactory, must appeal to us as being continuously effective. We know very well that the raising of water-vapor by solar heat will leave objectionable material behind, and we are satisfied that the result is perfect and that APPENDIX. 165 it will continue to be so during all time. We also know that the filtering and oxidizing power of the soil is very great, and in general we are willing to pin our faith upon its efficiency. But we cannot avoid a feeling of uncomfortable doubt when we note that a small amoimt of soil has been given a large quantity of work to perform, and we naturally ask, cannot the purifying' powers of such soil be overtaxed, with the result that our protective filter will become damaged at a point beyond reach of repair? Let an English case be quoted here : "A certain farmhouse was notoriously unhealthy. The inmates had suffered at various times from diph- theria and typhoid fever. The water had been ex- amined, and was reported to be satisfactory. Upon examining the premises it was found that there was a water-closet in the house, which was in good order, but where the contents were discharged was unknown. The drains were said to be satisfactory and never to get blocked, and upon tracing them, it was found that they discharged into a dry-steyned cesspool without overflow about four yards from the well, both sunk in the gravel, which here was twenty feet or more in thickness. This well yielded an unfailing supply of water, which was used for all. domestic purposes, and upon analysis it was found to be remarkably free from organic matter. It w^is S9,id to be always cool, bright, 1 66 APPENDIX. and sparkling, probably due to its containing a very excessive amount of chlorides and nitrates derived from the sewage percolating into the subsoil, arid the opinion was expressed that the water was a concentrated purified sewage. This was not believed at the time, but when the cesspool was filled in and the sewage carried elsewhere, the well ran dry. There is no doubt that in this case the same water was used over and over again. After being defiled by the closet, slops, etc., it ran into the cesspool, then filtered through the soil, in its progress the organic matters becoming com- pletely oxidized, and ultimately it found its way back to the well, to be utilized again for domestic purposes. Doubtless at times, possibly after heavy rains, the ces^ool contents filtered too rapidly for complete purification to be effected, and this impure water may have been the cause of the ill health amongst those who consumed it." In this instance, as in the one first given, the danger- signal was held out by the chemical side of the investi- gation alone, the other methods of inquiry failing to detect any trace of evil. It would seem that bacteriology deals with the present and that chemistry, besides throwing light upon the past, does, to some degree, prophesy what may happen in the future. Many a water which the bacteriologist has pronounced APPENDIX. 167 harmless has been condemned by the chemist because of what it might unexpectedly become at some future time; and, on the other hand, the bacteriologist has time and again shown the presence of unlooked-for pollution when the chemist might search for it in vain. A good instance of the saving of the situation by a 'sanitary survey' when both chemistry and bacteri- ology show adverse reports is to be found in the ex- amination of water from a new well or a recently 'developed' spring. Given an old and well-situated spring upon a hillside, the desire of the owner to 'im- prove' the property with a view of placing the water upon the market will commonly result in a disturbance of the immediately surrounding soil. From a sanitary outlook no harm has been done the water, and one familiar with the situation will offer no objection to continuing its use, but both the chemist and the bac- teriologist will secure analytical results which will re- quire to be explained to avoid an adverse report. The writer has seen many cases of this kind. Wells which are newly dug likewise furnish water of temporary apparent pollution. Distinction must here be made to allow for actual pollution arising from foreign substances being left at the bottom of the finished well. In such instances the evidence pointing to contamination will be found to persist, 1 68 APPENDIX. The tying up of pollution through the action of frost is another fruitful source of error, if the judgment be controlled by the laboratory data alone. Swamp waters commonly improve in winter, and samples of them will mislead the analyst who is unfamiliar with the districts whence they come. Again, the same agency will solidify surface sources of contamina- tion like those which produced such havoc at Ply- mouth and New Haven, and the laboratory exam- ination, whether chemical or bacteriological, will, throughout a northern winter, utter no prophecy of what is to be expected during the coming thaws of spring. Nothing short of a thorough sanitary survey can be depended upon in such instances. The water in a tidal river may be unimpeachable during ebb flow and quite the reverse at periods of flood. How could an analytical examination at the former stage of the stream predict what might be expected at change of tide? Instances very often arise when public clamor is heard loudly complaining of the taste and smell of water supplied to the people. Much irritation is felt whenever the senses are offended by its physical con- dition, although gross pollution by pathogenic organisms will be complacently accepted. This tendency of the public to be their own judge as to the suitability and safety of the water they are asked to drink reminds APPENDIX. 169 one of the decision of a Mississippi court in a case with which the writer had to do about a year ago. His honor said: "It is not necessary to weigh with tenderness and care the testimony of experts. An ordinary mortal knows whether water is fit to drink and use." Would that the ordinary mortal did know! Typhoid fever might then be relegated to the list of rare diseases, and much money and many precious lives be saved. When odors in water occur, what is the analyst to do? By the time the laboratory is reached all smell may have left the sample, and great discredit of the scientist will follow should his statement be that the water is sound, when the users thereof know to their sorrow that something is the matter with it. An examination in situ is what is needed in cases of this sort, and a view of the storage reservoir backed by microscopic detection of the offending organisms will do vastly more good than any amount of chemical analysis. A man now deals with the data of water-examination in a broad-gauged fashion, feeling that the day has gone by for blind adherence to cut-and-dried standards. He approaches his decision pretty much as does the medical practitioner frame his diagnosis at the bedside. It may be that the symptoms of the patient do not accord with the diescription of the disease as found in the books, and the practitioner's attention may be called 1 7^ APPENDIX. to those discrepancies by a coadjutor more recently from the schools; nevertheless the breadth of his experi- ence assures the more matiu-e man that his judgment is not at faxilt and it is experience that is of value in the end. APPEKDIX B. The method of testing oysters for B. coli as employed by the Mass. State Board of Health is as follows: * " The shellfish is washed with sterile water, opened with a sterile oyster knife and a portion of the shell water transferred to a fermentation-tube. The body of the shellfish is then removed from the shell, washed with sterile water, opened with a sterile scalpel and a portion of the alimentary canal transferred to another fermenta- tion-tube. Ten individual shellfish from each sampling station are tested in this manner. " If 50 per cent or more of shellfish from a location show B. coli, the location is dangerously polluted." " After a large amount of investigation the Bureau of Chemistry of the U. S. Department of Agriculture has decided to condemn oysters sold in interstate com- merce which show more than two samples out of five giving positive tests for B. coli types of organisms in one-tenth c.c. of the shell liquor. When oysters have been condemned on this standard, however, the exami- * Science, April 8, 1910. 171 172 APPENDIX nations have been supplemented with an inspection of the beds from which the oysters were obtained, and a bacteriological examination of the water bathing the oysters from these locaUties. " At the annual meeting of the American Pubhc Health Association held in September of this year, the Committee on ' Standard Methods of Sanitary Shell-Fish Examination ' gave considerable time to a discussion of bacteriological standards, but no definite action was taken. " The Rhode Island Shell-Fish Commission is now using the government ruling in passing upon the oyster grounds of that state, i.e., all oysters are condemned in which three out of five show the presence of colon bacilU in 0.1 of a c.c. of shell water." — Newlands and Ham. INDEX. PAGES Acidity determination 19 Acid waters, chlorine determination in 39 Agar-agar, preparation of 124 Agar and gelatin counts, comparison of 137 Agar, lactose litmus, preparation of 125 Albumen, decomposition of 75 Albuminoid ammonia in deep wells 77 Albuminoid ammonia, determination 67 Albuminoid-ammonia process 58 Albuminoid-ammonia process, interpretation oi results 76 Alkalinity, cause of 20 Alkalinity determination 19 Alkalinity usually equal to temporary hardness 28 Aluminum and iron, determination of 108 Alum, methyl orange not suitable in presence of 19 Alum, test for 105 Ammonia, high in city rain-water 79 Ammonia, high in swamp water 80 Ammonia, low in good groimd-water 79 Ammonia, rate of evolution, meaning of 82 Ammonia reduced from nitrates 80 Ammonium chloride solution, standard 60 Analysis, method of stating 12 Analysis of water, misconception of 1 Analysis rarely complete 6 Analysis, sanitary survey required for interpretation of 6 Analysis, imiformity of conditions required 62 Analytical results unintelligible to general public 2 Appendix 159 Arsenic, occurrence of in water 104 173 174 INDEX. Pase Bacillus coli communis, diagnostic value of 141 Bacillus coU communis from sea-gulls 143 Bacillus coli communis, gas evolved by 145 Bacillus coli communis, habitat of 143 Bacillus coli communis, testing oysters for 171 Bacillus coU communis, tests for 146 Bacillus typhosus, chance of discovering small 142 Bacteria, counting colonies of 132 Bacteria, device for counting colonies of 139 Bacteria, effect of low temperature upon 129 Bacteria, evolution of gas by 145 Bacteria, increased by melting snow 141 Bacteria,. increased by surface washing 141 Bacteria, method of sowing for total count 129 Bacteria, value of total count 120 Bacteriological examination 119 Barium, determination of 108 Berkefeld filter 15 Bile, lactose, preparation of 124 Bouillon, lactose, preparation of 123 Bouillon, preparation of 120 Brisbane supply, zinc in 102 Calcium, determination of 108 Carbon dioxide, determination of 113 Challenger Expedition, temperatiu-es reported by 18 Changes in samples during storage 11 Chemical examination of water 9 Chloride of sodium solution, standard 53 Chlorine 35 Chlorine comparates 42 Chlorine determination 38 Chlorine determination in acid waters 39 Chlorine determination, interference of color with 40 Chlorine in ground-water, influenced by population 38 Chlorine in rain-water, variation of 36 Chlorine, normal, charts of 32, 34 Chlorine normal, determination of 36 Chlorine, normal, influence of the sea upon 36 Chlorine, Volhard's process for 42 INDEX. 175 PAOB Chromium, occurrence of, in water 104 Clark's scale of hardness 32 Clark's soap test 30 Colon group, wide distribution of 143 Color, cause of 22 Color interference with use of turbidity rod 14 Color, standard 21 " Comparates," meaning of expression 22 Copper and lead 91 Copper, detection of 92 Copper, method of determining action of water upon 103 Copper, quantity allowable in water •. . 98 Copper solution, standard 91 Counting colonies of bacteria 132 Counting organisms not bacterial 156 Count of bacteria, method of sowing for 129 Count of bacteria, variation in 140 Counts on agar and gelatin, comparison of 137 Croton, temperature of water of 17 Culture media 120 Deep samples vary with temperature 5 " Degrees of hardness " 32 Determination of manganese 109 Dextrose bouUion, preparation of 123 Dilution method for total count 131 Directions for taking sample 9 Disease not traced to odor 16 Dissolved distinguished from suspended material 14 Dissolved oxygen, determination of ; 110 Dunham's solution, preparation of 125 EngUsh degree of hardness 32 Erythrosine as indicator for alkalinity 19 Examination of water, chemical 9 Fermentation-tube 148 Filter, Berkefeld 15 176 iNDEX. t>AOt! Formaldoxime reagent for copper 92 Free ammonia, determination of 61 Free ammonia, in deep wells 77 French degree of hardness 32 Frost's device for gas readings 150 Frost, great change in water because of 168 Galvanized iron, attacked by some waters 100 Gases, device for collecting gases in water 114 Gas in Smith tube, device for reading 149 Gelatin and agar counts, comparison of 137 Gelatin nutrient, preparation of 122 German degree of hardness 32 Germs, great cold not fatal to 129 Grains per gallon converted to parts per million 118 Griess, method of, for nitrites 44 Hardness 26 Hardness comparates 33 Hardness, degree of 32 Hardness due to magnesium 33 Hardness, permanent and temporary 28 History of water required to interpret analysis 4 Iron, allowable quantity in water 94 Iron and aluminum, determination of 108 Iron, determination 93 Iron solution standard 93 Indol, testing for 151 Interpretation of a water examination 159 Ithaca, temperature of water of 16 Lacmoid as indicator for alkalinity 19 Lactose bile, preparation of 123 Lactose bouillon, preparation of 123 Lactose litmus agar, preparation of 125 Lead, action of carbonic acid upon 99 Lead, action of peaty water upon 98 Lead and copper 91 Lead, erosion of 99 INDEX. 177 PAGE Lead, method of determiDing action of water upon 103 Lead, quantity allowable in water 97 Lead solution, standard 91 Lithium: determination of 108 Litmus solution 124 Logwood, test for alum 105 Loss on ignition 24 Magnesium, hardness due to salts of 33 Magnesium, determination of 108 Magnesium salts, action on soap 32 Manganese, determination of , 109 Metals, method of determining action of water upon 103 Methyl orange unsuitable for indicator in presence of alum ... 19 Mineral residue 107 Misconception of analysis of water 1 Miquel flasks 131 Naphthylamine hydrochloride solution 45 Nessler solution 58 Nessler standards 83 Nessler tubes, desbription of 68 Nessler tubes, device for reading 63 Nesslerizing, precautions 71 Nitrates absent from sewage 56 Nitrates, comparates 54 Nitrates, determination of 53 Nitrates due to use of nitroglycerine 57 Nitrates la rain-water £0 Nitrates, interference of chlorides with determination 52 Nitrates, nitrogen as 49 Nitrates, picric acid method for 51 Nitrates reduced by iron rust 80 Nitrate solution, preparation of 126 Nitrate solution, standard .' 53 Nitrite determination 46 Nitrite, standard solution of 45 Nitrites comparates 47 Nitrites in air of laboratory 46 178 INDEX. FAOB Nitrites ia well water unfavorable 44 Nitrites, method of Griess for 44 Nitrites, nitrogen as 43 Nitrites reduced from nitrates 80 Nitrogen, cycle of organic 57 Nitrogen, fixation of 50 Nitrogen in the soil 50 Nitrogenous organic matter 57 Nitroglycerine causes nitrates in deep well 57 Normal chlorine, charts of 22 Normal chlorine, determination of 36 Normal chlorine, influence of the sea upon 36 Odor and taste 15 Odor, relation of, to disease 16 Organic matter, nitrogenous 57 Oxalic acid, standard 88 Oxygen consuming capacity 87 Oxygen dissolved, determination of 110 Oxygen, solubiUty table 113 Oysters, testing for B. Coli 171 Parts per million converted to grains per gallon 118 Permanent hardness 28 Permanent standards 66 Permanganate solution, standard 87 Petri dish, showing colonies of bacteria 133 Petri dishes, method of sowing in 129 Petri dishes, porous covers for 130 Phenol-sulphonic acid 52 Phosphates, allowable quantity in water 106 Phosphates, determination of 106 Potassium chromate indicator 38 Potassic permanganate, alkaUne 60 Presumptive test for B. coli 162 Putrescibility, determination of 116 Rain-water, nitrates in 50 Reaction 18 " Required oxygen " 87 INDEX. 179 , PAQB Required oxygen comparates 89 Required oxygen determination 88 Samples change rapidly during storage 10 Samples for bacteriological examination 126 Sampling, directions for 9 Sanitary survey, great importance of 161 Sanitary survey necessary for interpretation of analysis 6 Scale-forming ingredients, determination of 108 Sea-gulls, source of B. Coli 143 Sediment, determination of 14 Silica, determination of 108 Silver solution standard 38 " Smith solution " 123 Soap, action of magnesium salts 32 Soap consuming power 28 Soap, expense for increased by hardness 30 Soap solution, standard 30 Soap test, Clark's 30 Solids, total 23 Sowing for the total count 129 Standard counting cell 157 Standard turbidity 13 Standards for interpretation of analjrtical results 22 Standards, Nessler '. 73 Standards, permanent 66 Standards, "_^8moky " 73 Sterilization by boiling not complete 156 Sterilization, methods for 122 Sterilizing glass ware 125 Sulphanilic acid solution 45 Sulphates, determination of 108 Sulphuric acid, standard 87 Suspended as distinguished from dissolved material 14 Swamp water, ammonia high in 80 Taste and odor 15 Temperature 16 Temperature causes variation in deep samples 5 Temperature, determination of, by thermophone 17 l8o\ INDEX. PAGE Temperature of Croton water 17 Temperature of Ithaca water 16 Temperature of Troy water 16 Temperatures reported by Challenger Expedition 18 Temporary hardness 28 Thermophone, determination of temperature by 17 Tides, great change in water with change in 168 Total count, sowing for 129 Total solids 23 Total solids " comparates " 25 Turbidity 13 Turbidity rod 14 Troy, temperature of water of 16 Troy, N. 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