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ing apparatus and the ventilating-ducts. The ward is heated chiefly by two steam-heaters in the basement, to which the out-door air is supplied through two cold-air boxes which cross the basement from side to side, so that the air may always enter from the windward side; a provision which ensures the possibility of regulating the ventilation in windy weather. A mixing valve at V permits the cold air to pass above the heater when it is necessary to cool the air, which enters the ward through two registers situated one each side of a large ventilating-chimney in the centre of the ward. Two open stoves, built into the ventilating-chimney, serve as auxiliary heaters, and their smoke-pipes, which pass upward inside the ventilatingchimney, heat the chimney and produce ventilation. A small grate in the lower part of the chimney can be used to heat it in summer. The main openings for removing foul air are at the floor level. They are ten in number, and distributed at equal distances around the walls of the room. A down-cast flue from each opening leads to the floor of the basement, beneath which all ten ducts converge to the bottom of the central chimney. Two openings into the chimney are provided near the ceiling for summer ventilation, and there are louvres over the windows, all of which can be opened and closed at will.

A general system for ventilating a dwelling can be arranged with a view to utilizing the waste heat from the kitchen fire to produce a motive force which will be active winter and summer. Ducts should be led from all the rooms to a tight collecting-chamber in the basement or cellar. A pipe must pass from this to the bottom of a large ventilating-flue, through the centre of which the hot smoke-pipe from the kitchen range must rise to the roof. If any such general system is adopted for a dwelling, there will be times when some of the openings to the ventilatingducts will need to be closed; as, for example, when open fires are burning whose draught tends to produce a reversal of the current of foul air. Indeed, it is probable that no system can be designed for any building which will not require some attention to ensure its regular operation, so many variable conditions occur which tend to counteract the necessarily feeble forces by which the movement of the air is produced.

Bibliography.-Tredgold, Principles of Warming and Ventilation (London, 1825); Reid, Illustrations of the Theory and Practice of Ventilation (London, 1844); Bernan, History of Warming and Ventilation (London, 1845); Peclet, Traité de la Chaleur (3d ed., Paris; new ed. in press); Hood, Treatise on Warming by Hot Water (London); Wyman, Treatise on Ventilation (Boston, 1846); Fairbairn, Glashier, and Wheatstone, Report of the Commission of the House of Commons on Ventilating Dwellings (1857); Ruttan, Ventilation and Warming of Buildings (New York, 1862); Morin, Etudes sur la Ventilation (Paris, 1863); Annales du Conservatoire, various articles (Paris, 1863-68); Tomlinson, Rudimentary Treatise on Warming and Ventilation (3d ed., London, 1867); Mondesir and Lebaitre, Ventilation par l'Air comprimé (Paris, 1867); Joly, Chauffage et Ventilation (Paris, 1869); Leeds, Lectures on Ventilation (New York, 1871); Smith

sonian Reports, translation from Morin (1873-74); Parkes, Manual of Practical Hygiene (London, 1873); Wilson, Handbook of Hygiene (London, 1873); Pettenkofer, Leetures, Relations of the Air to the House, etc. (London, 1873); Morin, Manuel du Chauffage, etc. (new ed. 1874; also translated from the French in the Smithsonian Reports for 1873-74). C. B. RICHARDS.

War'ren (JOSEPH), b. at Waterbury, Vt., July 24, 1829; studied at the Vermont University; became assistant editor of the Country Gentleman in 1849, associate editor of the Buffalo Courier in 1853, and chief editor of the latter paper in 1858; was chosen president of the New York State Associated Press in 1870. D. at Buffalo Sept. 30, 1876. He was a very active citizen, labored with great energy for establishment there of the State insane asylum, the State the construction of a public park in Buffalo, and for the normal school, etc., and held various offices of honor and trust.

Was'son (DAVID ATWOOD), b. May 14, 1823, at Brooksville, Me., of Scotch-Irish ancestry, who came to the country in 1724. In the remote village where he lived school was kept ten weeks in summer and eight in winter. Atten the lad's summer schooling was discontinued; at fifteen he studied Latin with the minister of the place; at sixteen had a term of study at a village academy; at nineteen was a teacher; in 1845 entered Bowdoin College, but stayed only a year; went to sea as a common sailor in hope of restoring tone to an overwrought frame and mind; studied law at Belfast, Me., but practised it for a short time only, being repelled by disagreeable features in it. An acquaintance with Carlyle's Sartor Resartus set his spiritual nature aflame. In 1848 he entered the theological seminary at Bangor; finished the course there; was approved by an examining council, and settled in 1851 at Groveland, Mass.; remained in that connection a year; then became preacher of an Independent" church in the same village; stayed there, with an interval of six months in Worcester, till 1857, when a severe attack of spinal disease put an end to all continuous labor for several years. In the spring of 1865 the society of Theodore Parker, worshipping in the Boston Music Hall, invited him to be their minister, but after some fifteen months of service ill-health compelled him to retire. Since then, save four years of subordinate service in the custom-house in Boston and a residence of two or three years in Germany, he has resided at West Medford, Mass., engaged in literary work. In spite of a hopelessly broken constitution, Mr. Wasson has been a diligent, brilliant, powerful, and original writer. The pages of the North American Review, the Atlantic Monthly, the Christian Examiner, and the Radical have been enriched by his contributions in prose and verse. Since his return from Germany he has printed in the Unitarian Monthly a paper on "State and Church in Germany," and another in the Inder on "State and Church in America." For a num ber of years Mr. Wasson has given much thought to political theories, and he has prepared two works on the subject of government, with especial reference to American problems. 0. B. FROTHINGHAM.

WATER ANALYSIS.

Wa'ter Anal'ysis has for its object the detection and determination of the various foreign bodies contained in natural waters, either in solution or in suspension. In this article space can be given to those methods only which are employed in the examination of fresh or potable waters; for the methods employed in the analysis of mineral waters reference must be had to special works on analytical chemistry.

I. THE COLLECTION OF SAMPLES.-Clean glass vessels should be used, either glass-stoppered or provided with new corks. The vessels should not be entirely filled, a space being necessary to permit expansion by changes of temperature. The stoppers or corks should be tied in, that the samples may not be tampered with on the way to the laboratory. Great care should be taken to secure a fair average sample; and when the water is from a river or a pond, it should be taken at a distance from the shore and sufficiently below the surface to avoid floating impurities. Before taking the sample the bottle and the cork should be thoroughly washed with the water which is to be sampled. From 1 to 5 gallons are required, according to the number and character of the determinations to be made. During the analysis the samples should be kept in a cool dark closet.

II. PRELIMINARY EXAMINATION. Physical Properties.(1) Taste: (2) Odor. Shake the vessel containing the water, to secure uniformity; then half fill a clean pint or quart bottle and warm the contents to about 100° F. Note the taste, and then, after violently shaking the bottle, the odor. (3) The reaction is determined with carefully-prepared litmus-paper or with cochineal solution. (4) The color and the turbidity are observed. If the water appears clear and nearly or quite colorless, it should be examined in comparison with distilled water in a glass tube 2 feet long and about 2 inches in diameter, ground at the ends, and closed with pieces of plate glass. If the water is turbid, a sample should be filtered previous to examination in the glass tube. The sediment may be collected by filtration or subsidence and examined chemically or microscopically. The percentage of suspended matter or sediment may be determined (a) by passing a measured quantity-500 or 1000 c.c.-through a weighed filter, drying at 100° C. and weighing. The inorganic portion of the sediment can then be determined by burning the filter in a platinum crucible. (b) Another method consists in determining the total solids and loss on ignition on both filtered and unfiltered samples of the water. (See further on Total Solids, etc.) The differences in the results will be due to suspended matter.

III. DISSOLVED SOLIDS.-Evaporate 250 c.c. of water in a weighed platinum dish on a water-bath. Dry for three hours in an air-bath, cool in a desiccator, and weigh. The result represents the (1) total solids dried at 100° C. This determination is not an accurate one, but is nevertheless of considerable value. It serves as a control on the subsequent analysis, and the next step, ignition, gives some valuable qualitative information with regard to the organic matters present. The inaccuracies of this determination of total solids are various: (a) Some organic constituents are lost by evaporation; (b) Some organic matters are decomposed and lost during the evaporation; (e) Some salts, as magnesic chloride, are liable to suffer loss by decomposition; (d) Some salts, as calcic and magnesic sulphates, retain considerable quantities of water of crystallization, thus increasing the amount of total solids. To remove water of crystallization, some prefer to dry the residue at higher temperatures-the Society of Public Analysts, at 220° F.; the Health Department of Berlin, at 110° C.; many chemists, at 130° C.; Tiemann, at from 150° to 180° C. Others suggest changing the calcic and magnesic sulphates and chlorides to carbonates by adding to the water, previous to the evaporation, a weighed quantity of pure sodic carbonate, the weight of which is to be subsequently deducted. Both these plans tend to increase the loss of organic matter.

2. Loss by Ignition, or Organic and Volatile Matter.After weighing the total solids it is customary carefully to expose the platinum dish to the flame of a Bunsen burner, noting the changes in appearance which its contents undergo, and also the odors given off. If the water is comparatively free from organic matter, no change in color will be noticed; otherwise, it may turn brown or black. Nitrates evolve nitrous fumes; animal matters give off nitrogenous (burnt-feather) fumes, ammoniacal or urinous odors, etc. The residue in the dish represents the incombustible or inorganic constituents of the water, and the difference between this and the total solids represents the "organic and volatile matters." In no case is this an accurate determination of the organic matters. The high temperature of the ignition expels, besides organic matter, water of crystallization, ammoniacal salts, carbon

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dioxide from the carbonates of lime and magnesia, and even alkaline chlorides. At the same time, nitrates and nitrites are decomposed with loss of nitrous fumes, and the magnesic chloride with loss of hydrochloric acid. To diminish those losses as far as practicable, the ignition is made as brief as possible, and is conducted at the lowest adequate temperature. Further to restore the lost carbon dioxide of the carbonates, the residue is moistened with distilled water saturated with this gas or with a solution of ammonic carbonate, and dried at 180° C. before weighing. At the Berlin health department the ammonic carbonate is used, and after drying the residue is gently ignited. The residue thus obtained may be used for the estimation of phosphoric acid, as directed farther on.

3. Silica, Oxide of Iron and Alumina, Lime, and Magnesia.-One or two litres of the water are acidulated with hydrochloric acid and evaporated to dryness in a platinum dish. The residue is moistened with hydrochloric acid, treated with distilled water, and boiled. If much calcic sulphate is present, care must be taken to use sufficient hydrochloric acid to bring it all into solution. The insoluble residue of silica is collected on a filter, incinerated, and weighed. In the filtrate the small quantity of oxide of iron and alumina is precipitated by ammonic hydrate; in the filtrate the lime is precipitated by ammonic oxalate; in the filtrate from the lime the magnesia is precipitated by sodic phosphate. If any of the filtrates become inconveniently bulky and dilute, they must be concentrated by evaporation.

4. The Alkalies.-One or two litres of water are concentrated in a platinum or silver dish to 200 c.c.; baric chloride is added, to precipitate sulphuric acid, and milk of lime or baric hydrate, to precipitate magnesia; the whole is boiled and filtered. To the filtrate ammonic carbonate and a little ammonic oxalate are added, to remove lime and baryta; the whole is boiled and filtered. The filtrate is evaporated and cautiously ignited, to expel ammonia salts; the residue consists of sodic and potassic chlorides. After weighing, the potassium is determined by platinic chloride.

5. Hardness is the soap-destroying property of the water. It is chiefly due to the lime salts present, though magnesia and oxide of iron may contribute. It is determined by a standard solution of soap, and is generally expressed in degrees equal to the quantity of calcie carbonate equivalent to the soap employed. The value of the degree is, in Germany, 1 part of CaO in 100,000 parts of water; in France, 1 part of CaCO3 in 100,000 parts of water; in England, I part of CaCO3 in 70,000 parts of water, or 1 grain to the Imperial gallon; in the U. S., 1 part of CaCO3 in 100,000 parts of water, or 1 part of CaCO3 in 58,318 parts of water, or 1 grain to the U. S. gallon.

The total hardness is due to the carbonates and sulphates present in the water. As the calcic and magnesic carbonates are precipitated by boiling, the hardness of the boiled water is caused by the sulphates; this is called permanent hardness, while that produced by the carbonates is called temporary. The standard soap-solution is best prepared by rubbing in a mortar 150 parts of lead-plaster with 40 parts of dry potassic carbonate. When thoroughly mixed, add absolute alcohol which has been standing a few days over dry potassic carbonate. Filter, and to the filtered soapsolution add an equal volume of recently-boiled distilled water. Preserve in a well-stoppered bottle. Although this potassic soap is said to keep better than soda soap, most chemists prefer the latter, as it can be procured of suitable quality in the form of ordinary white Marseilles soap. Dissolve 10 grammes in 1000 c.c. of strong alcohol, and filter. To standardize the soap-solution, prepare a solution of calcic chloride by carefully dissolving in a covered platinum dish with hydrochloric acid 0.5 gramme of Iceland spar; expel the excess of acid by successive evaporations with distilled water; finally, dissolve in water, and dilute to 500 c.c. Each cubic centimetre of this solution corresponds to 0.001 gramme of CaCO3. In place of the calcic chloride an equivalent solution of barie chloride may be used. It is prepared by dissolving 1.219 grammes crystallized BaCl2.2H20 to 500 c.c. Ascertain now how many cubic centimetres of the soap-solution will be required to produce a permanent lather or foam when shaken in a 250 c.c. glass-stoppered bottle with 10 c.c. of the calcic-chloride solution diluted to 100 e.c. with recentlyboiled distilled water. Then prepare a diluted soap-solution for use of such a strength that I c.c. will be equivalent to 1 c.c. of the calcic-chloride solution or .001 gramm CaCO3. The actual test of the water is made as follows: 100 c.c. of the water to be tested is poured into a glassstoppered bottle of about 250 c.c. capacity. The bottle is violently shaken, and the air above the water is then sucked out through a glass tube, to remove the carbon dioxide given off by the water; 1 c.c. of the standard soap

solution is added, and the bottle shaken. This addition | cipitate has settled, then decant the clear solution for use. of soap is repeated till a permanent froth is produced. As the reaction approaches completion the soap must be added in smaller quantities; finally, drop by drop. The operation is completed when the froth remains for five minutes. Each cubic centimetre of soap-solution is equivalent to .001 CaCO3 in the 100 c.e. of water used, or to .01 CaCO3 per litre of water, or to 1 part in 100,000 = 0.70 in 70,000 or 0.58 in 58,318 parts. The permanent hardness is determined by first boiling 100 c.c. water thoroughly, adding enough recently-boiled distilled water to replace the volume lost by evaporation, and proceeding as before. The difference between the total and the permanent will be the temporary hardness.

=

6. Chlorine may be determined gravimetrically by precipitation with argentic nitrate in the presence of nitric acid. It is, however, usually determined volumetrically with a standard solution of argentic nitrate, using potassic chromate as the end-reagent. With a tenth normal argentic nitrate solution containing 17 gms. per litre, each cubic centimetre .00355 Cl, or .00585 NaCl; with a solution containing 4.7887 gms. AgNO3 per litre, each cubic centimetre = .001 Cl. The silver solution may be verified with a solution of pure sodium chloride; the tenth normal solution will require 5.85 NaCl per litre. With 1.648 NaCl per litre, 1 c.c. = .001 Cl. The potassic-chromate solution is made by dissolving 10 gms. K2CrO4 in distilled water to 200 c.c., adding AgNO3 till a permanent red precipitate is formed, allowing this to settle, and preserving the clear solution. If the water contains much chlorine, 100 c.c. will be sufficient for the test. Add a few drops of the potassic chromate, and then run in the silver solution from a burette till a permanent reddish tint appears. If the water contains very little chlorine, 500 c.c., or even 1000 c.c., may be evaporated to about 100 c.c., filtered, and tested. If the water is very alkaline, evaporate to dryness after acidulating with acetic acid, dissolve in water, filter, and test. If the water is so colored as to obscure the end-reaction, it may first be partially evaporated with a little pure calcic carbonate or entirely with pure calcic hydroxide. In the case of very peaty waters which are not freed from color by either of these methods, evaporation with a little potash alum and filtering the concentrated water while hot answers the purpose. Titration with argentic nitrate is not very accurate with water containing much sewage. In this case Volhard's method is more accurate. It consists in adding an excess of the silver solution, thoroughly shaking it, diluting to a fixed volume, filtering through a dry filter, and determining the excess of silver in a portion by titration with ammonic thiocyanate, using ammonio-ferric sulphate as the endreagent. (See Salkowski, Chem. Centralbl., 1881, p. 203; Mallet, Report Nat. Board of Health for 1882, p. 261; and Sell, Mittheil. Kaisl. Gesundheitsamte, Bd. 1, 1881, p. 370.) This method is not absolutely accurate in the presence of large quantities of sewage, and recourse must be had to gravimetric analysis.

7. Sulphuric Acid.-One litre of water is acidulated with HCl concentrated to one-quarter and precipitated hot with baric chloride. The precipitated BaSO4 multiplied by 0.3436 gives S03; by 0.4123 gives S04. Volumetric methods may also be used. (See Tiemann-Kubel, p. 45; Flügge, p. 284. The full titles of these works are given at the end of this article.)

8. Phosphoric Acid.-The ignited residue from the total solids, already mentioned, is to be moistened with nitric acid and evaporated to dryness. The residue is moistened with a few drops of nitric acid, dissolved in a little water, and passed through a filter previously washed with dilute nitric acid. The fiitrate, which should not measure more than 3 c.c., is mixed with 3 c.c. molybdic-acid solution, gently warmed, and then set aside for 15 minutes, at a temperature of about 80° F. The result is reported as "traces," "heavy traces," or "very heavy traces as color, turbidity, or a definite precipitate is respectively produced after standing fifteen minutes. For a quantitative determination, 2 litres of the water must be evaporated to dryness in a platinum dish, gently ignited, and treated as above. The yellow precipitate must be collected on a filter, washed with dilute molybdic-acid solution, dissolved in ammonia, and the phosphoric acid determined with magnesia solution. (See Cairn's Quantitative Analysis, p. 189.)

9. Ammonia is determined by (a) distilling a measured volume of water and Nesslerizing the distillate. The Nessler solution is prepared by dissolving 35 gms. of potassic iodide in 100 c.c. water and adding to this, in the cold, a solution of 17 gms. mercuric chloride in 300 c.c. water till a permanent precipitate is produced. Then dilute with a 20-per-cent. solution of sodie hydroxide to 1000 c.c. Add mercuric-chloride solution till a permanent precipitate again forms. Allow the whole to stand till the pre

A standard solution of ammonic chloride is prepared by dissolving 3.146 grammes NH4Cl to 1000 c.c. in distilled water free from NH3; for use, dilute this to with distilled water free from ammonia. A 20-per-cent. solution of pure recently-ignited sodic carbonate is also requisite. Into a retort of about 1500 c.c. capacity connected with a Liebig's condenser put about a litre of ordinary water; add 5 c.c. of the solution of sodic carbonate and distill as long as the distillate gives a yellow color when tested with the Nessler solution. Then add 500 e.c. of the water to be examined, continue the distillation, and collect the distillate, in successive portions of 50 c.c. each, in Nessler tubes. To each of the tubes add 3 c.c. Nessler solution. Continue the distillation till the last 50 c.c. gives no color with the Nessler solution. To estimate the quantity of ammonia obtained, take five Nessler tubes. Into the first pour 50 c.c. distilled water free from ammonia; into the others put 1, 2, 3, and 4 c.c. of the tenth ammonic-chloride solution, and fill up to 50 c.c. with distilled water free from ammonia. Add to each of the five comparison-tubes 3 c.c. Nessler solution. The comparison-tubes will now contain: the first, no NH3; the second, .00001 NH3: the third, .00002 NH3; the fourth, .00003 NHa; the fifth, .00004 NH3. By carefully comparing the tints of the distillates with those of the comparison-tubes, the amount of ammonia in the distillate can be determined. If any of the distillates exhibit a deeper tint than the fifth comparison-tube, dilute to 100 c.c., throw out one-half, and compare again. Should the water contain unusual quantities of ammonia, less than 500 c.c. must be used for the distillation. It is well to test 100 c.c. of the original water with Nessler's solution beforehand.

(b) Another, simpler method, which is preferred by some chemists and is now used in the imperial health department at Berlin, is as follows: 300 c.c. of the water are put into a 500 c.c. stoppered cylinder. To this are added 2 c.c. of a 33-per-cent. solution of sodic carbonate, and 1 c.c. of a 33-per-cent. solution of sodic hydroxide, both free from ammonia. The cylinder is closed, shaken, and allowed to settle; 100 c.c. may then be poured off clear. If not, this quantity must be filtered through a previously-washed filter. This is then placed in a Nessler tube and Nesslerized in comparison with mixtures of the standard ammonic-chloride solution and distilled water, to which similar quantities of the solutions of sodic carcarbonate and hydroxide are added. (See Groves-Fresenius, Part II., p. 130; also, Sell, Mittheil. aus dem Kaist. Gesundheitsamte, Bd. 1, 1881, p. 366; also Flügge, p.

253.)

10. Nitrous Acid.—(a) The meta-phenylenediamine test of Dr. Griess consists in observing the depth of yellow color developed in 100 c.c. of the water on the addition of 1 c.c. of -per-cent. solution of this base in water supersaturated with sulphuric acid, and 1 c.c. of a 33-per-cent. sulphuric acid (by volume), in comparison with a standard solution of sodic nitrite. (See Frankland, p. 40.) (b) The naphthylamine test of Dr. Griess consists in observing the depth of pink color developed in 100 c.c. of the water on the addition of an acid solution of naphthylamine sulphate and a solution of sulphanilic acid in comparison with a standard solution of sodic nitrate. (See Warrington, Chem. News, vol. li. p. 40, and Mallet's Report, p. 281.) This is one of the most delicate reactions known.

11. Nitrous and Nitric Acids together.-(a) Walter Crum's method consists in concentrating the water to a very small bulk and agitating over mercury with a large excess of strong sulphuric acid. The whole of the nitrogen is then evolved as nitric oxide. (See Frankland, p. 87.) (b) The aluminium process involves reducing the nitrates and nitrites to ammonia by means of the nascent hydrogen liberated by the action of strong alkalies on aluminium. The ammonia is distilled off and Nesslerized. (See Frankland, p. 30.) (c) The copper-zinc process is now most generally used. Reduction of the nitrates, etc. to ammonia is in this process effected by zinc coated with metallic copper. Nearly fill a 300 c.c. wide-mouth, glass-stoppered bottle with coarse zinc-turnings. Cover the zine with water; add a few cubic centimetres of a 3-per-cent. solution of cupric sulphate. When the surface of the zine exhibits a black coating of metallic copper, pour off the liquid and wash thoroughly with pure distilled water. Rinse twice with the water to be examined, fill up with the water, add a pinch of crystallized oxalic acid, and allow to stand about twelve hours. The reduction may be completed in a shorter time by placing the bottle in a warm situation. The absence of nitrites by the naphthylamine test indicates the completion of the reduction. The ammonia produced is determined by Nesslerizing, either directly or in the distillate, from 50 or 100 c.c. to which a little pure sodic carbonate is first added. Deduct the free

1

WATER ANALYSIS.

ammonia contained in the water, and calculate the rest as nitrogen from nitrates and nitrites. (See Frankland, pp. 29 and 100.)

12. Nitric Acid.-No satisfactory method is known whereby nitric can be detected in the presence of nitrous acid. But two methods are available for solving the problem indirectly: (a) The nitrous acid may be destroyed by adding a little urea, slightly acidifying with sulphuric acid, and gently heating. The nitric acid may then be detected by the diphenylamine test and determined by the aid of the copper-zine process. The diphenylamine test is very delicate for either nitric or nitrous acid. A little diphenylamine is treated with water and then dissolved by the gradual addition of strong sulphuric acid; 1 or 2 e.c. of the water to be tested are placed in a small beaker, a drop of the diphenylamine solution is added, and then twice the whole volume of pure oil of vitriol. If nitric acid is present, a purple color will at once develop. (See Warrington, Chem. News, vol. li. p. 41.)

13. Organic Matter.-No method has yet been devised by which the quantity of organic matter contained in water can be accurately determined. This is due to the great variety and the comparatively minute quantities of the organic matters present, and to their loss by evaporation and their ready destructibility by the operations employed in chemical analysis. Nevertheless, such importance attaches to the estimation of the organic matter, even approximately, from a sanitary standpoint, that several methods are now in general use for this purpose.

(a) The loss by ignition, already referred to, is of no practical value as indicating the actual amount of organic matter present.

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the flame, a measured volume of the standard oxalic-acid solution added, sufficient to decolorize the excess of permanganate, and the excess of oxalic acid is then determined by dropping in from a burette permanganate solution to permanent redness. By using permanganate and oxalic-acid solutions of equal value the difference between the cubic centimetres of the two solutions used will indicate the permanganate required to oxidize the organic matter. If the permanganate solution contain 0.395 gm. pure potassic permanganate in 1 litre, each cubic centimetre will contain .0001 available oxygen. A tenth normal oxalic-acid solution should be prepared by dissolving 6.3 gms. oxalic acid to a litre; this should be tested against the permanganate solution, thus fixing the value of the latter in available oxygen, as 1 c.c. of this solution requires .0009843 oxygen. A portion of the oxalic-acid solution may then be diluted till it corresponds, volume for volume, to the permanganate. The permanganate must frequently be compared with the tenth normal oxalic-acid solution, as it is liable to undergo change. (2) In the Schultz method, as improved by Trommsdorff, 100 c.c. of water is placed in a 300 c.c. flask; half of a cubic centimetre of a 33-percent. solution of pure sodic hydroxide is then added, and 10 c.c. of the permanganate solution. The whole is then boiled for ten minutes, and allowed to cool to 50° or 60° C. Five c.c. of dilute sulphuric acid (25 per cent. by volume), and then 10 c.c. of the corresponding oxalic-acid solution, are run in. The permanganate is then added to permanent redness. (3) Tidy's process is extensively used by the English chemists. The reagents are a permanganate solution of which 1 c.c. equals .0001 gm. oxygen; a 10per-cent. solution of pure potassic iodide; dilute sulphuric acid, 25 per cent. by volume, which has received an addition of permanganate sufficient to give it a faint pink color after warming to 80° F. for four hours; a solution of sodic thiosulphate containing 1 gm. per litre; and a starch solution containing 1 gm. starch in 500 c.c. water. Two tests are made at 80° F.; in one the permanganate is allowed to act for fifteen minutes, in the other for four hours. The tests are made in 12-oz. glass-stoppered bottles; 250 c.c. water is measured into each bottle, which is then stoppered and placed in a water- or an air-bath and raised to 80° F. To each bottle is then added 10 c.c. of the dilute sulphuric acid and 10 c.c. of the permanganate. Fifteen minutes later one of the bottles is removed from the bath and two or three drops of the potassic iodide is added, to destroy the excess of permanganate, an equivalent amount of iodine being liberated. After thorough admixture run in from a burette the standard solution of thiosulphate till the yellow color of the iodine is nearly destroyed. Then add a little starch-water, and continue adding thiosulphate till the blue color of the iodide of starch disappears. At the end of four hours remove the other bottle and determine the excess of permanganate in the same way. The thiosulphate is standardized from time to time by adding to 250 c.c. redistilled water 2 or 3 drops of potassic iodide, 10 c.c. of the permanganate, and titrating with thiosulphate as above described. (For a full discussion of the permanganate methods see Flügge, Mallet, Sell, and Tiemann-Kubel.)

(b) The process of Frankland and Armstrong is fully described in Frankland's work on water analysis. It involves (1) the determination of the carbon of the organic matter which is not volatile during evaporation; (2) of the total nitrogen of the non-volatile organic matter and the ammoniacal salts; (3) the nitrogen in the form of ammoniacal salts, this latter by the methods already described for ammonia. One litre of the water is boiled in a flask with 20 c.c. of a saturated solution of sulphurous acid, to expel the carbon dioxide of the carbonates and to destroy and expel the nitrous and nitric acids present. The water is then very carefully evaporated to dryness in a small thin glass dish, with special precautions. To ensure the complete destruction of the nitrates, 1 drop of a solution of ferrous chloride is added to the first dishful of the water. The residue left on evaporation is mixed with cupric oxide, removed from the dish, and heated in a combustion-tube in connection with a Sprengel pump, to withdraw the resulting gases and transfer them to the measuring-tube. These gases consist of CO2 and N from the organic matter, with perhaps traces of S02, 0, and nitric oxide. A couple of drops of potassic bichromate are let up into the tube, to absorb the SO2. The volume of gas is then carefully noted, and potassic hydroxide is introduced, to absorb the CO2, the volume of which is determined by the reduction in volume. Pyrogallic acid is introduced, to absorb any oxygen present, which will be indicated by the color produced in the alkaline solution of pyrogallic acid. If oxygen is absent, a bubble of this gas is introduced, to convert any nitric oxide present into peroxide, which, with the excess of oxygen, will be absorbed by the alkaline pyrogallate. The resulting gas will be nitrogen, the volume of which is to be noted and subsequently corrected by deducting the nitrogen of the ammoniacal salts present. This method of analysis, which gives the carbon and nitrogen of the organic matter, is complicated and requires considerable experience. It has been extensively used in England, but has been much criticised, as have all the methods employed in determin-line, and the free ammonia is Nesslerized. ing organic matter. (See Mallet's investigation, in the Annual Report of the National Board of Health for 1882; Flügge, p. 240; Wanklyn and Chapman's work, etc.)

(e) The permanganate process depends upon the fact that potassic permanganate destroys organic substances to a greater or less extent by supplying oxygen. As the permanganate has a very deep purple color and is decolorized by the loss of oxygen, it is easily applied in the form of a standard solution, the value of which can be established by the use of a definite solution of oxalic acid or some other deoxidizing agent. This reagent was introduced by Forchhammer in 1849, and various processes have since been devised for its use. (1) In Kubel's process, which is used by the imperial health department at Berlin, a measured volume of water-sny 200 e.c.-is placed in a 400 c.c. flask, acidulated with 10 c.c. 25-per-cent. sulphuric acid, and treated with a measured quantity of the permanganate sufficient to give a persistent red color. It is then boiled for ten minutes, more permanganate being added if the water becomes colorless. The flask is then removed from,

(d) The Albuminoid-ammonia Process of Wanklyn, Chapman, and Smith is fully described in Wanklyn's book. It depends upon the destruction of the albuminoid organic matters by potassic permanganate, with the formation of ammonia. The operation is conducted in a retort, as in the process already described for the determination of ammonia, and the albuminoid ammonia in the distillate is determined in the same way by Nesslerizing: 500 e.c. of the water are first distilled, with the addition of a little freshly-ignited sodic carbonate, if it is not already alkaWhen the

free ammonia has all been expelled, a specially prepared solution of permanganate is added, and the distillation continued as long as ammonia is found in the distillate. The successive distillates, of 50 c.c. each, are Nesslerized in the usual way. The special permanganate solution is prepared as follows: 200 gms. of potassic hydroxide and 8 gins. of pure potassic permanganate are dissolved in 1100 c.c. distilled water and boiled rapidly down to 1000 c.c. This solution is preserved for use. As soon as the distillation for free ammonia is started 50 c.c. of this alkaline permanganate are measured out, diluted with 200 c.c. of water, placed in a flask, and boiled during the whole time that the distillation for free ammonia is going on, care being taken that the concentration does not proceed too far. There must be enough of this boiled, diluted permanganate to bring the volume of the water under treatment back to about the original 500 c.c. Some analysts prefer to use two portions of water, determining free NH3 in one and total NH3 in the other, counting the difference as albuminoid NHs. To determine the total NH3,

put about 300 c.c. tolerably pure water into the retort, add 50 c.c. of the alkaline permanganate, and distill as long as the distillate shows NH3. Then turn down the gas and introduce the 500 c.c. of the water to be tested; distill and Nesslerize as before. (For a full discussion of the merits of this process see Wanklyn, Frankland, Flügge, Mallet, Sell, etc.)

IV. THE DISSOLVED GASES may be expelled from a measured volume of water by boiling, collected over mercury, and the CO2, 0, and N determined as already described under Organie Matter. Reichardt's apparatus is specially adapted for this purpose. (See Zeit. f. an. Chem., vol. xi. p. 271; also Mallet's report, p. 284.) Schützenberger and Risler have devised an excellent method for determining the dissolved oxygen in the water without first expelling it. In this method the oxygen is determined by the amount of indigo white it converts into indigo blue. Standard solutions of ammoniacal cupric sulphate, sodium thiosulphate, and indigo carmine are employed. (See the Berichte, vol. xii. p. 1768, and Flügge, 266.)

V. MICROSCOPIC EXAMINATION.-The sediment should be examined with and without staining-fluids for the identification of vegetable and animal life, as well as for hairs, epithelial scales, fibres of wool, linen, cotton, etc. Small samples of the water should also be evaporated over sulphuric acid and dried on slides, to be stained and examined. Good results are also obtained by adding to 100 c.c. of water 1 c.c. of a 1-per-cent. solution of osmic acid and examining the sediment which is deposited on standing.

VI. BIOLOGICAL ANALYSIS, as introduced by Dr. Robert Koch of Berlin, is designed to enable the observer to count the number of bacterial germs in a given volume of water (1 c.c.) and to isolate and study the individual species. This is accomplished by adding 1 c.c., or fraction thereof, of the water to 10 c.c. of a sterilized medium, preferably a mixture of beef-juice, peptone, and a 10-per-cent. gelatine solution. Tubes charged with 10 c.c. of this culture-medium and plugged with sterilized cotton are carefully prepared and thoroughly sterilized, and may be kept till wanted. In making use of them, the gelatine is melted by immersing the tube in tepid water. The cotton plug is removed, the water added and thoroughly incorporated. The mixture is then poured out upon a sterilized glass plate, about 34 by 5 inches, kept cool and level upon an ice-box," and protected from dust by a glass cover. When the gelatine has set, the plate is removed to a sterilized glass culturechamber. In the course of two or three days the bacteria make their appearance in minute colonies scattered through the gelatine. These colonies are now counted, each colony being considered as representing at least one germ originally contained in the water. If the number of colonies is very large, the counting may be facilitated by the use of a glass plate ruled in squares, which is supported directly above the gelatine surface. Individual colonics are further investigated by transferring particles to suitable culture-media, such as gelatine, agar-agar, bouillon, bloodserum, potatoes, etc. The individual bacteria are identified by (a) their appearance under the microscope, both alive and properly stained; (b) by the peculiarities of the growth in or on culture-media; (e) by their effects when applied to animals by inoculation. (Consult, on this subject, Miquel, Ann. de l'Observatoire de Montsouris, 1880, p. 493; Koch's "New Method of Pure Cultivation of Bacteria," Q. J. Microscop. Sci., 1881, xxi. 650; Koch, "Zur untersuchung von Pathogenen Organismen," Mitth. a. d. k. Gesundheitsamte, Berlin, 1882, Bd. 1, p. 36; Vejdovski, Thierische Organismen der Brunnen Wasser von Prag, Prag, 1882: Nägeli, Untersuchungen ueber niedere Pilze, Munich, 1882; Certes, Sur l'Analyse micographique des Eaux, Paris, 1883; R. Angus Smith, "Gelatine Test for Organisms in Water," Med. Times and Gazette, May 26, 1883; Koch's methods are described in the Anhang zu den Verhandlungen der deutschen Gesellschaft f. oef. Gesundheitspflege, Berlin, 1883; A. Proust, Rev. d'Hygiène, 1884, vi. 915: E. Vallin, Rev. d'Hygiène, 1884, vi. 922; C. Girard, Rev. d'Hygiène, 1884, vi. 1023; E. Marchand, Compt. rend., xcvii. 49, 1884; J. Brautlicht, Chem. News, xlviii. 180, 1884; S. Maggi, Gaz. Chim. Ital., xiii. 323, 1884; H. Fol and P. L. Durant, Recherches sur le nombre des Germs virants que renferment quelques Eaux de Genève, Genève, 1884; R. A. Smith, Second Report to the Local Government Board, London, 1884; Becker, Reichs-Medicinal Kalender, 1884; G. Wolff hägel, Arbeiten aus d. kais. Gesundheitsamte, Bd. 1, Berlin, 1885, p. 5; Roth, Vierteljähresschrift für gericht. Med., vol. xliii., 1885; Cramer, Die Wasserversorgung von Zurich, Zurich, 1885; T. Leone, Chem. News, Dec. 4, 1885; Carpenter and Nicholson, The Analyst, ix. 94, 1885; C. J. H. Warden, Chem. News, lii. 52, 66, 73, 89, 101; P. F. Frankland, Chem. News, Dec. 18, 1885; Cornil et Babes, Les Bacteries, Paris, 1885; W. Zopf, Die Spaltpilze, 3d ed., Breslau, 1885; E. Klein,

Micro-Organisms and Disease, 2d ed., London, 1885; C. S. Dolley, The Technology of Bacteria Investigation, Boston, 1885; Sternberg-Magnin, Bacteria, 2d ed., New York, 1885; G. Bischof, Chem. News, Apr. 30, 1886; Meade Bolton, Zeitschrift für Hygiene, vol. i. 77, 1886; Dr. Link, Chem. News, May 14, 1886, p. 232; V. Malapert-Neufville, Fres. Zeitsch. An. Chem., xxv. 39, 1886; F. Hueppe, Die methoden der Bacterien Forschung, 3d ed., 1886; E. M. Crookschank, An Introduction to Practical Bacteriology, New York, 1886.)

VII. COMPUTING AND PRESENTING THE RESULTS OF AxALYSES.-Analyses are usually executed with the weights and measures of the metric system, but the results are reported in various forms. (1) Grains in one English (imperial) gallon of 277.274 cubic inches, or 70,000 grains, =4543 c.c.: (2) Grains in one U. S., wine, or Winchester gallon of 231 cubic inches, or 58,318 grains, at 62° F., = 3785.2 c.c.; (3) Parts in 100,000; (4) Parts in 1,000,000, or milligrammes in one litre; (5) Pounds avoirdupois in a million gallons. The analyst will be influenced in his selection from these different methods in any particular case by the end in view in making the examination.

VIII. GROUPING THE CONSTITUENTS FOUND BY ANALYSIS. -In some cases the bases, acid anhydrides, and salt radicals are reported separately as K2O, Ña2O, CaO, MgO, CO2, SO3, Cl, etc., but generally they are combined and reported as salts: KCl, NaCl, CaSO4, etc. There are no very generally-accepted rules for deciding the distribution, but it is most usual to proceed as follows: Combine Na with Cl, and K with SO4; any excess of K with Cl, then with CO2; any excess of Na with S04, then with CO3; any excess of SO4, after satisfying K and Na, with Ca, then Mg: Cl, after satisfying Na and K, with Mg, then with Ca: after Cl and SO, are provided for, remaining bases are combined with CO2. Carbonates are sometimes reported as anhydrous simple carbonates, sometimes as acid carbonates, as CaH2(CO3)2; the other compounds are reported as anhydrous. Silica is reported as such; oxide of iron and alumina as such-together, usually, owing to the small quantity present.

IX. INTERPRETING THE RESULTS OF WATER ANALYSIS.— Many chemists have given standards of purity to be used in interpreting water analysis, but experience shows that they cannot be relied upon. Dr. Elwyn Waller has brought these standards together in the Second Annual Report f the Board of Health of the State of New York. The judicious analyst compares the water under examination to other waters of known purity, and, having in mind the local conditions and history of the source of the sample, draws his conclusions accordingly. When biological analysis was first introduced, it was claimed that it would entirely supersede chemical analysis, and that it would in future be simply necessary to count the germs in a cubie centimetre of water and record the verdict at once. But thus far both methods of analysis have failed to recognize or reveal the particular constituents or organisms which in polluted water produce disease. All that either method has accomplished is to fix the amount of certain substances or the number of certain organisms in either case entirely harmless in themselves which are supposed to indicate previous contamination with refuse matters liable to include the germs of disease. While it is thus impossible to give exact standards of purity, the experienced analyst finds little difficulty, in most cases, in satisfying himself as to the quality of the waters which he examines.

X. CHOICE OF METHODS.-There is much to be said for and against the different methods for determining organic matter, etc. The writer very decidedly prefers the following determinations and methods: (1) Total solids dried at 110° C.; (2) loss by ignition, moistening with ammonie earbonate; (3) chlorine (volumetrically); (4) hardness, both total and permanent; (5) phosphates by molybdie-acid test; (6) nitrites by naphthylamine test; (7) nitrates by the zinc-copper couple, distillation, and Nesslerizing; (8) free and albuminoid NH3 by Wanklyn and Chapman's method; (9) Tidy's permanganate test-fifteen minutes and four hours at 80° F.

XI. LITERATURE.-Kubel, Dr. Wilhelm: Anleitung zur Untersuchung von Wasser, Zweite Auflage von Dr. Ferd. Tiemann (Braunschweig, 1874); Reichardt: Grundlagen zur Beurtheilung des Trinkwassers, 3te Auf. (Jena, 1875); Tiemann und Preusse; Veber Trinkwasseruntersuchungen Vierteljahresschr. f. ger. Med., Oct., 1877; Fox: Sanitary Examination of Water, Air, and Food (London, 1878); Frankland, Dr. E.: Water Analysis for Sanitary Purposes (London, 1880); Ludwig Hirt: System der Gesundheitspflege, 2te Auf. (Breslau, 1880); Eugen Sell: Ueber Wasser Analyse, unter besonderer Bernecksichtigung der im Kaiserlichen Gesundheitsamte ueblichen methoden, Mittheilungen a. d. k. Gesundheitsamte, Bd. 1, p. 360 (Berlin, 1881); Society of Public Analysts: Instructions for Water

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