WATER ANALYSIS CHARLES GRIFFIN & CO. LTD., Publishers With Four Folding Plates and Numerous Illustrations. Large 8vo. 8s 6d net WATER SUPPLY: A Practical Treatise on the Selection of Sources and the Distribution of Water By KEGLNALD E. MIDDLETON, M.Inst.C.E., M.Inst.Mech.E., F.S.I. " As a companion for the student, and a constant reference for the technical man, we anticipate it will take an important position on the bookshelf." PRACTICAL ENGINEER, In Large 8vo. Cloth. With 147 Illustrations. 15s net THE PRINCIPLES OF SEWAGE TREATMENT By PROF. DUNBAB. ENGLISH EDITION by HARRY T. CALVERT, M.Sc., Ph.D., F.I.C. " We heartily commend the book as a peculiarly fair and impartial statement of the present position of the sewage problem." LANCET. Beautifully Illustrated, with Numerous Plates, Diagrams, and Figures in the Text. 21s net TRADES' WASTE: Its Treatment and Utilisation. By W. NAYLOR, F.C.S., A.M.Inst.C.E. " There is probably no person in England to-day better fitted to deal rationally with such a subject. BRITISH SAMARITAN. SIXTEENTH EDITION, Thoroughly Revised. Price 6s PRACTICAL SANITATION: A Hand-book for Sanitary Inspectors and Others interested in Sanitation. By GEORGE REID, M.D., D.P.H. WITH AN APPENDIX ON SANITARY LAW By HERBERT MANLEY, M.A., M.D., D.P.H. " A very useful handbook, with a useful Appendix. We recommend it not only to sanitary inspectors, but to householders and all interested in Sanitary matters." SANITARY RECORD. SECOND EDITION, Revised. In Crown 8vo. Handsome Cloth. Profusely Illustrated. 8s 6d net SANITARY ENGINEERING: A Practical Manual of Town Drainage and Sewage and Refuse Disposal. By FRANCIS WOOD, A.M.Inst.C.E., F.G.S. " The volume bristles with information which will be greedily read by those in need of assistance. The book is one that ought to be on the bookshelves of every practical engineer." SANITARY ENGINEER. LONDON : CHARLES GRIFFIN & CO. LTD., EXETER ST., STRAND WATER ANALYSIS FOR SANITARY AND TECHNICAL PURPOSES BY HERBERT B. STOCKS FELLOW OF THE INSTITUTE OF CHEMISTRY FELLOW OF THE CHEMICAL SOCIETY MEMBER OF THE SOCIETY OF CHEMICAL INDUSTRY WITH EIGHT ILLUSTRATIONS LONDON CHARLES GRIFFIN AND COMPANY LIMITED EXETER STREET, STRAND 1912 All rights reserved PREFACE THE author has endeavoured in the following pages] to give a concise and accurate description of the methods adopted for the analysis of waters for sanitary and technical purposes, with the hope that the information may be of use to Public Analysts, Medical Officers of Health, and students who are interested in this branch of analytical work. In a short treatise it would not be possible to give a detailed description of all the processes which have been proposed for the determination of the various constituents in waters, even if any useful purpose could be served by so doing, there- fore attention has been directed to those processes which have been found after long experience to be particularly useful both for sanitary and for industrial work. Water analysis requires a considerable amount of practical experience in the laboratory along with the skill which comes from long practice, neither of which can be gained from books, but it is hoped that a practical manual such as the one now presented may render it easy for those beginning this work to successfully carry out any investigations which may be necessary, and also to interpret intelligently the re- sults which may be obtained. The processes described in the v 284573 vi PREFACE .present work are those of the chemist, that is physical and chemical. The biological examination is quite distinct from this and requires separate treatment. Simply culti- vating the bacteria in a nutrient medium and counting the colonies which develop may in special cases be useful, but in the majority of cases it adds little or nothing to the information already gained by the chemical examination. The microscopical examination is, however, included, as very often information is obtained from it which is exceedingly valuable. HERBERT B. STOCKS. WEST KIRBY, January 1912 CONTENTS PAGE INTRODUCTION 1 PART I. PHYSICAL EXAMINATION Colour 5 Suspended Matter 5 Taste 6 Odour 6 Microscopical Examination 7 PART II. CHEMICAL EXAMINATION 1. QUANTITATIVE ANALYSIS FOB SANITARY PURPOSES Determination of Free and Saline Ammonia 9 Albuminoid or Organic Ammonia 14 Solids in Solution 16 Loss on Ignition of Solids in Solution 17 Solids in Suspension 19 Loss on Ignition of Solids in Suspension 20 Organic Carbon and Nitrogen 21 Nitrogen as Nitrates 38 Nitrogen as Nitrites 50 Oxygen Absorbed * 53 Chlorine 58 Hardness 60 2. QUANTITATIVE ANALYSIS OF THE MINERAL CONSTITUENTS Alkalinity 68 Acidity 69 Basic Radicles 70 Acid Radicles 76 Calculation of the Results of the Mineral Analysis 80 3. DELETERIOUS METALS Lead 84 Copper 87 Arsenic 88 Zinc 89 Iron 89 vii viii CONTENTS 4. GASES CONTAINED IN SOLUTION Oxygen 93 Carbonic Acid, Oxygen, and Nitrogen by Gasometric Methods 100 APPENDIX I. Standards of Purity Recommended by the Rivers Pollution Commissioners 103 APPENDIX II. Tabular View of the Standards for Effluents adopted by Various Authorities 105 APPENDIX III. Average Composition of Unpolluted Water 106 APPENDIX IV. Tension of Aqueous Vapour 107 APPENDIX V. Reduction of Cubic Centimetres of Nitrogen to Grams 110 APPENDIX VI. Loss of Nitrogen by Evaporation of NH 4 HSO 3 111 APPENDIX VII. Loss of Nitrogen by Evaporation of NH 4 H 2 PO 4 112 APPENDIX VIII. Warington's Method of Estimating Nitrates. Table for Converting c.c. of Indigo Solution to Pts. of N. per 100,000 114 APPENDIX IX. Table of Hardness 115 APPENDIX X. Preparation of Re- agents Required for Water Analysis 117 INDEX 133 WATER ANALYSIS INTRODUCTION Water in its pure state is a compound of two atoms of hydrogen with one atom of oxygen that is, two parts of hydrogen and one part of oxygen by volume, or one part of hydrogen and eight parts of oxygen by weight. Pure water is, however, difficult to prepare artificially, and never occurs in Nature, the nearest approach to it being rain water, and water obtained from melted ice, collected fai inland and in districts remote from habitations. Even these contain small quantities of impurities, both gaseous and solid, and as water flows over the soil or percolates through the various strata below, it dissolves further impurities, the nature and quantity of which vary very considerably in different districts, being entirely dependent upon the composition of the soil and subsoil and of the rocks below. Waters may be placed in groups according to the sources from which they are derived, as follows : (1) Rain water. (6) Upland surface water. (2) Stream and river waters. (7) Lake water. (3) Spring water. (8) Brackish water. (4) Shallow well water. (9) Sea water. (5) Deep well water. The supply of potable waters is derived directly from the A 2 WATER ANALYSIS first seven groups .and indirectly from the last two by dis- tillation. In addition to waters from the above-named sources, the analyst has to deal with sewage, drainage from cultivated land, effluents from sewage works, polluted stream and river waters, effluents from various industrial works, &c., all of which may be examined by the same processes as are used in the analysis of waters for drinking purposes. The sanitary analysis of a sample of water is not a full analysis, nor is it necessary to estimate every constituent present in order to arrive at its suitability for drinking and general household purposes. The analysis is so arranged that it gives definite information upon the question whether a water contains sewage or other organic pollution, or any deleterious matters, such as poisonous metals, and this is done by apply- ing special qualitative or quantitative tests for those which are injurious ingredients. In searching for pollution by organic matter, the amount of carbon and nitrogen present in the latter are estimated, and, in addition, some of the products into which organic matter is known to decompose by oxidation are determined. Though a complete analysis with a long list of figures looks imposing, still for sanitary purposes all that is required is to prove whether the sample of water is fit or unfit for drinking purposes, and therefore the determinations can be narrowed down to a few tests which are absolutely essential. For an ordinary sanitary analysis the following estimations are made : Total solid matter, free ammonia, albuminoid ammonia, nitrogen as nitrates, nitrogen as nitrites, oxygen absorbed, and chlorine. The water is also examined physically for colour, taste, odour, and clearness, and any deposit it may contain, however small, is examined under the microscope. The reaction of the water to litmus is also determined. INTRODUCTION 3 For a fuller sanitary analysis, in addition to the above, the following estimations are made : Loss on ignition, organic carbon and nitrogen, total, temporary, and permanent hardness, poisonous metals, and action upon lead. Any suspended matter is also determined, and separated into organic and mineral. For sewage, a similar analysis to the full sanitary is per- formed, but without the hardness and poisonous metals tests. An ordinary analysis of sewage does not include, however, the estimation of the organic carbon and nitrogen. In special cases the gases dissolved in water may have to be separated, and the proportions of oxygen, nitrogen, and carbonic acid determined. A full mineral analysis of the water includes the separation and estimation of all the mineral constituents, and is required only in special circumstances. In examining waters for boiler or laundry purposes it i? necessary to determine the total solids and the temporary and permanent hardness. The amount of lime, magnesia, sulphuric and carbonic acids, and chlorine may also be estimated, and tests applied for iron and for acidity or alkalinity. If the water is acid its action upon iron should be noted. It may also be necessary to calculate the amount of lime or carbonate of soda required for softening purposes ; this can be done from the figures obtained in such an analysis. Amount of Water required for Analysis. The quan tity of water required for an ordinary sanitary analysis is one Winchester quart ; for a full sanitary analysis two Winchester quarts ; and for a full mineral analysis five Winchester quarts. The bottles should be stoppered bottles, and in order to make sure that they are perfectly clean they should be thoroughly rinsed with common hydro- chloric acid, washed with water, rinsed with caustic soda solution, and carefully washed with several changes of water 4 WATER ANALYSIS until the latter is neutral to litmus paper. The omission of the proper cleansing of the bottles, or the use of corks, often leads to erroneous results. Collection of Samples. Before taking a sample the bottle is about half filled with the water taken direct from the source, shaken, and emptied. The bottle may then be filled, the stopper put in and tied down. In taking a sample from a river or stream, the bottle is held mouth upwards below the surface of the water, and if the stream is shallow care should be taken not to disturb any deposit or mud at the bottom. At the time the sample is taken certain particulars should be noted for instance, number of sample, date, source of water (i.e. well, spring, deep well, &c.), nature of surroundings (i.e. whether any ash-pits, cesspools, open drains, or manure -heaps are in close proximity). In the case of a well or spring, the nature of the soil, subsoil, or rock may be noted, whether compact or porous, diameter and depth of well, and in the case of a river or stream the distance from the source ; also the position (i.e. whether taken from the side or centre, from the surface, or at what depth below the surface). Any other information that may be useful in coming to a decision as to whether there is anything in the surroundings that might now or in the future render the water impure or unfit for drinking purposes should also be given. A distinctive number corresponding with that in the note-book is placed on each bottle at the time the sample is taken ; this is very essential, and saves a lot of trouble. If the water is to be examined lacterially, a separate sample is taken in a sterilised flask in the way described in text-books on the subject. PART I PHYSICAL EXAMINATION Colour. The colour of water is examined in a " two-foot tube " that is, a glass tube about 1 in. in diameter and 2 ft. long, which is provided with glass covers at both ends ; one of the caps is fixed, and the other can be screwed off for the purpose of filling. Examined in a two-foot tube, very pure waters are either colourless or bluish ; algae colour the watei greenish, while yellow or brown tints are usually due to organic matter or iron. A quantitative measure of the nature and amount of colour can be made by means of Lovibond's tintometer and a series of standard colour-glasses. As the results of these examinations can be tabulated, it will be found an important test when periodical examinations o waters from the same sources are to be made. Suspended Matter. The clearness or freedom from sus- pended matter is observed at the same time as the colour of the water. Turbidity in a water may be due either to mineral or to organic matter ; in either case it must be regarded as pollution, and no turbid water should ever be allowed to be used for drinking purposes. On standing, the suspended matter may subside and the water become clear ; the deposit is then examined under the microscope, and if it is simply mineral matter it will prove of no very great importance, seeing that by filtration the impurity can be removed ; this should be recommenced by the analyst 5 6 WATER ANALYSIS On the other hand, a deposit containing a large quantity of organic matter and many infusoria would be much more serious, tending to show that pollution was gaining access to the source of the sample. Filtration in this case might not remove the whole of the polluting material. Where suspended matter is present, it may be necessary to estimate the amount and determine the proportion of organic matter present in it. In certain cases the turbidity of the water is permanent, or nearly so, little or no solid matter settling out on standing. This may be due to extremely minute oil-globules or to finely divided clay : the former is a truly permanent emulsion, while the latter settles out, though with extreme slowness. Taste. As a rule waters have no very decided taste ; deep well waters and the water of springs and mountain streams have, however, a sharp, pleasant flavour owing to being fully aerated. Stagnant, peaty, and polluted waters are decidedly unpalatable ; iron and magnesia render the water bitter, and excess of chlorides as in brackish water impart a salty flavour. Certain micro-organisms impart a distinct odour and taste to water, and, indeed, in some cases they have been the cause of considerable trouble in several public water supplies Taste and odour in these cases are very often akin to one another (see below). It is not advisable to make a general practice of tasting samples of water indiscriminately ; in many cases they are brought for analysis because they are suspected to be polluted, and may (and possibly often do) contain disease germs which it is not desirable to take internally. Odour. The odour of a water usually partakes of the same character as the taste ; that is, if the sample has a fishy taste the odour is also fishy. The odour is best developed by placing a little of the PHYSICAL EXAMINATION 7 water in a wide-mouthed test tube, warming to about 40 C., and then smelling it. Peaty waters have an earthy odour. Certain water-weeds, for instance, chara, &c., when de- caying, impart to the water a slight odour like decaying fish, and in some cases smell strongly of sulphuretted hydrogen ; the odour of sewage and putrefying organic matter is readily distinguished, while jungi growing on decaying vegetable matter will yield a musty odour. A foul odour the " pig pen " odour is evolved by the decay of Anabena or Nostoc. Whipple (The Microscopy oj Drinking Water, page 113) has given much attention to the odours of drinking water, and he concludes that certain odours are associated with the presence of particular organisms. For instance, aromatic odours are evolved by the diatoms. Asterionella, Cyclotella, Meridion, and Tabellaria ; grassy odours by the Cyano- phycece, Anabena, Rivularia, &c. ; fishy odours by the Chlorophycece, Volvox, Eudorina, Pandorina, &c. ; also by protozoa, such as Uroglena, Bursaria, Peridinium, &c. These odours are due in some cases to oily products, of the nature of essential oils, which are elaborated by the living organisms and stored up in their cells. In a few instances this has been conclusively proved by extracting the oils by means of petroleum spirit or ether, and allowing them to stand in contact with air, when they have been found to resinify in a similar manner to the terpenes. In other cases the odours are undoubtedly due to decay, and are therefore degradation products formed by bacterial activity. Microscopical Examination. The suspended matter in drinking waters is usually so small in quantity that it cannot be detected with the eye alone. If however the bottle containing the sample be allowed to stand for a few hours, the greater part of the water being then 8 WATER ANALYSIS carefully decanted and the remainder poured into a conical test glass and again allowed to stand, in most cases there is a trace of deposit which can be examined under the micro- scope. In deep well waters usually very little is to be seen except perhaps a few particles of sand. A little ochre may however be present, either brought up mechanically or deposited from solution, and in some cases the outer sheaths of the iron organism (Crenothrix) may be detected. The organisms mentioned attach themselves to the walls of deep boreholes and break away in such quantity as to render the water quite turbid. In other respects such waters may be ex- tremely pure. Unpolluted upland surface waters, especially previous to nitration, contain vegetable debris, many di- atoms, desmids, and confervse, also iron organisms and the manganese organism (Cladothrix), and sometimes crustaceans, e.g. Cyclops, Daphnia, &c. By filtration many of these are removed, but usually a few of the lower forms pass into the filtered water. Polluted shallow well waters, and drainage from cultivated land contain bacteria, Monas, Paramecia, Vorticella, &c., also decaying vegetable matter, starch grains, hyphaa and spores of moulds, vegetable fibres, scales of moths, and other portions of insects. In highly polluted waters the deposit is usually a living mass of bacteria, Monas, Paramecia, and other infusoria. Sewage in its raw state contains animal and vegetable debris and abundance of bacteria and Monas ; as it becomes purified and therefore aerated, large forms of infusoria, e.g. Paramecia, Oxytricha, Vorticella, Rotifera, Bursaria and others, appear and multi- ply. The sewage fungus (Beggiatoa), which decomposes sulphuretted hydrogen and stores up sulphur, may also often be found. PART II CHEMICAL EXAMINATION I. QUANTITATIVE ANALYSIS FOR SANITARY PURPOSES DETERMINATION OF FREE AND SALINE AMMONIA Ammonia may exist in water both in the free state and as salts of ammonia, and is produced during the first stage of the oxidation of nitrogenous organic matter ; hence its presence may (except in very special circumstances) be taken as undoubted evidence of sewage contamination. As a rule it is accompanied by organic matter in solution, the estimation of which will serve as a further indication of the degree of pollution, but in a few instances it has been found to be present in what would otherwise be regarded as pure samples, having been derived from nitrates by reduction, and it is always present in small amount in rain water even when the latter has been collected in the open country. As the majority of natural waters are alkaline in reaction, it may be assumed that any ammonia present exists in the state of ammonia, or as carbonate of ammonia, both of which are liable to be lost on standing. It is therefore very important that the determination of the free and saline ammonia should be commenced as soon after the receipt of the samples as possible. Polluted waters and sewage are especially prone to change in composition by keeping, even in closed bottles, owing to bacterial action, and these 9 10 WATER ANALYSIS must be analysed immediately in order that a true estimate of their composition may be obtained. The apparatus used in the estimation of ammonia (Fig. 1) consists of a 60-oz. plain retort (a stoppered one should not be used, as the stoppers are rarely tight and there is danger that ammonia may be lost), a large Liebig's condenser FIG. 1. Apparatus for estimation of free and saline ammonia. with a copper jacket and an inner tube of glass, a set of six Nessler cylinders, the mark on each indicating a volume of 100 c.c. The Nessler cylinders should be carefully chosen, so that the 100 c.c. marks are all at the same height, as this is important. A white porcelain tile or plate is also required, and a long pipette marked at 2 c.c. If the apparatus has not been used for some time, the condenser is disconnected, inverted, and the water in the jacket drained out. A little water is then placed in the retort, which is connected up with the condenser, and heated till steam is seen to issue from the open end of the latter. CHEMICAL EXAMINATION 11 This is the best way of ensuring that the apparatus is free from ammonia. The quantity of the sample to be taken for the estimation of free and saline ammonia will depend upon the quality of the water. To obtain some idea of the amount of ammonia present, 100 c.c. of the water are taken in a Nessler cylinder ; to it are added 2 c.c. of Nessler's solution, and after a few minutes' standing the colour is noted. If the preliminary test shows no colour or but a faint yellow tint, 500 c.c. is a convenient quantity to employ, but if the water is impure and shows a distinct yellow tint, 250 c.c. will be sufficient, while in the case of sewages 5 or 10 c.c. may be quite enough for the determination. When less than 500 c.c. of the water are taken, the total volume is made up to 500 c.c. with distilled water, free from ammonia (Appendix X). As soon as the apparatus has become cool it may be dis- connected and the retort emptied. A funnel is then placed in the neck of the retort, about 1 gram of recently ignited anhydrous sodium carbonate shaken into it, and washed into the retort with 500 c.c. of the water to be analysed. The retort is then connected up with the condenser, and the distillation proceeded with as rapidly as possible, taking care there is a good flow of water through the condenser. The distillate is collected in the Nessler cylinders, and as soon as 100 c.c. have passed over, the first cylinder is set aside, and a second one put in place of it ; if necessary a third 100 c.c. is distilled over. The subsequent procedure will entirely depend upon the amount of ammonia present. In distilling ordinary waters, practically the whole of the ammonia will be present in the first 100 c.c., but with sewages the whole of the ammonia may not have been obtained even after distilling off 300 c.c., and it is therefore necessary in such cases to allow the retort to cool, make up to the original volume with distilled water. 12 WATER ANALYSIS and continue the distillation till no appreciable quantity of ammonia can be detected in the water passing over. Pre- suming that we are dealing with an ordinary sample of water, the cylinder containing the second 100 c.c. of the distillate is placed on the white tile, and to it is added 2 c.c. of the Nessler's solution (Appendix; X), blowing through the pipette so that the air which escapes serves to mix the two liquids. If ammonia is present, a yellow colour will develop in a few seconds and become gradually deeper. At the side of the cylinder is placed a second cylinder containing distilled water free from ammonia, and as quickly as possible such a quantity of the standard solution of ammonium chloride (Appendix X) is added to it from a burette as may be considered sufficient to produce a similar colour, and after adding 2 c.c. of the Nessler's solution the two may be allowed to stand for a few seconds, and then their tints compared ; if the colour of the comparison test is found to be paler than that of the sample, a further small quantity of the standard solution may be taken, but a large quantity cannot be added in this way, as it tends to produce a turbidity which vitiates the result, so that it is necessary to make a fresh comparison with the larger amount of the standard solution added before the Nessler solution is put in. If the colour of the comparison test is found to be deeper than that of the sample, a second test is at once prepared with less of the standard solution. After a little practice, it becomes easy to match the tints with rapidity, and this is especially necessary to obtain accurate results, seeing that the tints increase in intensity the longer the tests are allowed to stand. When a comparative test having the same depth of tint as the sample has been obtained, the number of c.c's of the standard solution required to produce this tint is noted. The determination of the ammonia in the second 100 c.c. CHEMICAL EXAMINATION 13 of the distillate having been completed, the third 100 c.c. may be tested in the same way, and as a rule it will be found either free from ammonia or only containing a trace. If the amount of ammonia in the second 100 c.c. is extremely small, the first 100 c.c. may then be treated in a similar manner, but should it be large, then an aliquot portion (50, 20, 10, or 5 c.c.) of the first 100 c.c. is removed to another cylinder and diluted with distilled water to 100 c.c. before being tested. The reason for this is that a colour equivalent to more than 3 c.c. of the standard solution of ammonium chloride cannot be accurately judged ; it is therefore neces- sary to dilute the distillate before adding the Nessler solution to such a strength that not more than 3 c.c. of the standard solution are required to yield a similar colour. Assuming the distillates from 500 c.c. of a sample of water to require : First distillate, after diluting 20 c.c. to 100 c.c. (= 1 in 5) .... =2-5 c.c. Second distillate 1'2 c.c. Third distillate . . . . . 0'2 c.c. of the standard solution of ammonium chloride to yield similar colours, then the results may be tabulated as follows : First 100 c.c. = 2'5 x 5 = 12'5 c.c. Second 100 c.c. = 1'2 c.c. Third 100 c.c. = 0'2 c.c. Total . . . 13-9 c.c. 1 c.c. standard solution of ammonium chloride = '00005 grams NH 3 . /. -00005 X 13-9 x 200 = 0'139 part of NH 3 per 100,000. 14 WATER ANALYSIS The colour produced by ammonia with Nessler's solution is due to the formation of oxydimercuriammonium iodide (NH 2 Hg 2 OI). A good sample of water of any class should contain not more than O005 part NH 3 per 100,000 ; a larger quantity must be regarded as decidedly suspicious. Deep well waters are usually practically free from ammonia some, however, contain up to O'l part per 100,000. Un- polluted upland surface waters do not contain more than a trace to 0*008 part ; springs contain up to O'Ol part ; upland surface waters from cultivated districts to 0*25 part ; shallow well waters, being more liable to pollution with surface drainage, often contain appreciable quantities of ammonia, up to as much as 2'5 parts. Rain water always contains a small quantity of ammonia (about 0'03 part) which has been dissolved during its passage through the atmosphere, but provided the water is otherwise sound the presence of this ammonia cannot be regarded as a sign oi pollution. Sewage may contain 2 to 6 parts of ammonia, or even more. In one or two instances ammonia has been found to be present in considerable quantities in deep well waters, having been derived from nitrates by the reducing action of galvanised iron pipes ; when this is proved it may be affirmed that the presence of ammonia thus formed is not evidence of pollution. ALBUMINOID OR ORGANIC AMMONIA The term " albuminoid " ammonia was applied by "Wanklyn to the ammonia which is evolved when waters containing nitrogenous organic matters are heated with a strongly alkaline solution of potassium permanganate. There is no evidence to show that albuminous matters are present in such waters ; therefore it may perhaps be better to term this " organic ammonia," or " ammonia derived from organic CHEMICAL EXAMINATION 15 matters." Potassium permanganate, being a powerful oxi- dising agent, destroys the organic matter, and if this con- tains nitrogen the latter is converted into ammonia. It must, however, be clearly understood that rarely is the whole of the nitrogen in the organic matter evolved as ammonia ; this is shown conclusively by the experiments of Wanklyn* on pure compounds, only five of which yielded the theoretical quantities of ammonia, the others yielding one-half, one- third, or some other fraction or indefinite quantity. The albuminoids and similar bodies, though very unstable, belong to the latter class, gelatin giving 12 '7 instead of 22'22 per cent., albumen 1OO instead of 19'43 per cent., casein 7'6 instead of 19'43 per cent. Urea yielded 22 to 33 per cent, of the theoretical, and uric acid only 7'0 instead of 40*48 per cent. Several experiments with varying quantities of moist white of egg gave concordant figures, which would appear to show that the proportion of nitrogen obtained as ammonia by distilling albumen with alkaline permanganate, though not the theoretical, bears some relation to the total quantity. The fact that the ammonia obtained on distilling with alkaline permanganate is not the total quantity is also proved by comparison with the organic nitrogen found by Frankland's or KjeldahPs processes. The estimation of organic ammonia is performed upon the residue left in the retort after the determination of free and saline ammonia. The retort is allowed to cool, 50 c.c. of recently boiled alkaline permanganate (Appendix X) are added, and the contents made up to 500 c.c. with ammonia- free distilled water. To prevent bumping, which is rather apt to occur, a piece of ignited clay pipe-stem or pumice is added, and the distillation is then proceeded with in exactly * Jour. Chem. So?., 1867, p. 591 ; Water Analysis, by Wanklyn and Chapman, Appendix, p. 18. 16 WATER ANALYSIS the same manner as for free ammonia. The distillate is collected in the Nessler cylinders, and the amount of ammonia in each estimated in the manner already described. The albuminoid ammonia, being formed by the oxidation of organic matter, is not evolved so quickly as the free ammonia ; hence it may be necessary to distil several 100 c.c's before it ceases to be evolved. Especially is this the case with sewages and highly polluted waters. Deep well waters yield as a rule no albuminoid ammonia ; upland surface waters yield always a small quantity, 0*005 to 0'015 part per 100,000, derived from the peaty matter or from the vegetable organisms which it contains. A larger quantity than 0*015 part is usually evidence of animal contamination, and must be regarded with suspicion. SOLIDS IN SOLUTION For the determination of the solids in solution, a convenient quantity of water to take is 500 c.c., but if the water is a very hard one or the amount of solids is likely to be great, then a smaller quantity i.e. 250 c.c. or 100 c.c. will suffice, as the time- taken up in evaporation is curtailed, and the residue is much sooner dried. A platinum dish, after being thoroughly cleaned; is heated to bright redness over a blowpipe, allowed to cool in a desiccator, and weighed. It is then placed on a porcelain ring in one of the openings of the water-bath and filled with the water from the measuring flask ; as the water evaporates it is replenished from the flask, until finally all the water has been transferred to the dish, and the residue is quite dry. The platinum dish is then removed from the water- bath, wiped dry on the outside with a clean cloth, and placed in a hot-air oven, which is kept at a temperature of 105 C. It is allowed to remain in the air-bath for three hours, then CHEMICAL EXAMINATION 17 removed to a desiccator, cooled, and weighed ; it is sub- sequently again heated for one hour, and weighed. As a rule, it will be found there has been no loss during the second heating, and therefore the residue is quite dry, but if the loss should exceed 1 or 2 milligrams the heating must be repeated until the Weight remains constant. If 500 c.c. of water are used, the weight of solids obtained x 200 gives parts per 100,000. The solids in solution are very variable in quantity, Kain water contains the least amount i.e. about 2 parts per 100,000; upland surface waters contain from 2J to 10 parts, and deep well waters as a rule 10 to 50 parts ; the latter amount may be exceeded in very hard waters or those containing a large proportion of common salt as, for instance, in wells sunk in porous strata near the sea-shore, or in brine- producing districts ; shallow well waters often contain large amounts of solid matter, 30 to 150 parts, or even more, and when this is the case usually the nitrates are corre- spondingly high, as well as salts of lime and magnesia. It is not possible to lay down any hard and fast rules as to the significance of the amount of solids, but very soft waters are not the best from a dietetic point of view, though very desirable for household purposes ; on the other hand, very hard waters are not to be recommended either for drinking or for general household work. The solids obtained as above may be used for the estima- tion of the loss on ignition, or, when the amount of the water at the disposal of the analyst is small, for a qualitative examination of the mineral constituents. LOSS ON IGNITION OP SOLIDS IN SOLUTION The platinum dish containing the solids in solution is held over a blowpipe flame, and quickly moved about so that every part of it is raised to a bright red heat and the B 18 WATER ANALYSIS organic matter burnt off, the duration of heating being as short as possible consistent with perfect combustion. The dish is allowed to cool again in a desiccator and weighed as rapidly as possible. The difference between the weight of the total solids and the weight after ignition represents the " loss on ignition," and if 500 c.c. of the water have been taken the result x 200 will give the parts per 100,000. The determination of the loss on ignition, though originally devised for the estimation of organic matter, yields figures which bear no relation to the amount of the latter present in fact, the results are really not quantitative at all, as the amount lost is entirely dependent upon the temperature employed and the time of heating ; there is a considerable loss on heating, even when there is no appreciable quantity of organic matter present, and this loss may be due to one or more of the following : salts of ammonia ; carbonic acid from carbonates ; oxygen from nitrates ; loss of volatile chlorides ; and last, but not least, the water of hydrated salts, which either do not decompose at all or which lose only a portion of their water of crystallisation at the tempera- ture of the drying oven (105 C.), and the remainder at a higher temperature. Several salts of this kind occur in waters, and among them may be mentioned calcium chloride (CaCl 2 .6H 2 0), calcium sulphate (CaS0 4 .2H 2 0), magnesium sulphate (MgS0 4 .7H 2 0). The residues from ordinary waters do not show any signs of blackening on heating, but sewages and polluted waters blacken more or less, and an odour of burning wool or feathers can at the same time be perceived. This may be regarded as a qualita- tive test for the presence of nitrogenous organic matters. CHEMICAL EXAMINATION 19 SOLUS IN SUSPENSION In ordinary drinking waters the suspended matter or deposit ought not to be more than microscopic in quantity, but if an appreciable quantity should be present, this would be important, and an estimate of the amount might then be necessary. In the case of sewages and effluents which always contain more or less suspended matter, the amount and nature of this material is important, and in many analyses it is included in all the determinations that is, the sample is shaken up before taking out the quantities for analysis, this being done in order to get the composition of the whole sewage or effluent as it is received ; in addition, the solids in suspension are estimated in a separate portion ; on the other hand, it may be preferable to perform the analysis upon the supernatant liquid after the deposit has subsided. The method of procedure must be decided according to the requirements of each case. If the amount of the deposit has to be separately estimated, but is not to be included in the remainder of the analysis, then it is necessary before proceeding to the analysis to shake up the sample and measure out a sufficient quantity of the turbid liquid for the estimation of the solids in suspension, the remainder of the analysis being subsequently performed on what is left of the liquid after the solids have subsided. In no case is it advisable to filter a water or sewage in order to obtain a clear liquid for analysis ; filtration is in many instances very slow, and while standing on the filter decomposition may take place to such an extent as to vitiate the results ; the liquid is decanted as soon as the deposit has subsided. When the deposit is but small in amount, the whole of the sample is measured, the deposit allowed to settle out, the clear liquid decanted off, and the remainder reserved to 20 WATER ANALYSIS be filtered, but if an appreciable quantity of deposit is present the sample is shaken and 250 c.c. of the turbid liquid taken for the estimation. A filter paper of about 11 c.m's diameter is dried in the water-oven for one hour, then placed in a weighing tube, allowed to cool in the desiccator, and weighed. The water containing the deposit is filtered through the paper, and when it has all passed through, any solid particles left adhering to the flask are transferred to the filter paper by washing with distilled water, and the paper again dried and weighed in the tube. The gain in weight represents the solid matter in suspension. If the solids in suspension do not settle out readily and the liquid is difficult to filter, they are separated by means of a centrifugal machine, the clear liquid decanted, and the deposit washed out with distilled water. The amount of solids in solution is obtained by subtracting the weight of the solids in suspension from that of the total solids. When the amount of suspended matter is only trifling, and therefore not estimated, the solids in solution are called the total solids. LOSS ON IGNITION OF SOLIDS IN SUSPENSION If the solids in suspension are ignited the residue repre- sents the inorganic solids, and the loss the organic solids. To determine the loss, a platinum crucible is cleaned, ignited, and weighed, and the filter paper containing the solids having been transferred to it, is ignited until all the organic matter has burnt away and nothing but an ash remains ; after cooling in a desiccator the crucible is again weighed. The increase in weight after deducting the ash of the filter paper is the amount of the inorganic solids, while the difference between this and the total solids in suspension consists of the organic solids. CHEMICAL EXAMINATION 21 ORGANIC CARBON AND NITROGEN The quantity of the organic matter in water cannot be accurately determined by any known process. Numerous experiments have been performed with the object of estimating minute proportions of organic matter, but none of the pro- cesses put forward are sufficiently accurate for the purpose of water analysis. This being the case, the best alternative is to estimate the constituents of the organic matter by an ultimate analysis. For this purpose Dittmar and Robinson * devised gravimetric processes for separately estimating the carbon and nitrogen, and Dupre and Hake f a method of estimating the organic carbon ; the Kjeldahl process is also available for estimating the nitrogen. Frankland's Combustion Process. The best method, how- ever, is that devised by the late Dr. Edward Frankland, known as Frankland 's combustion process for the determina- tion of organic carbon and nitrogen. This process is to be relied upon to give concordant results, and though a delicate process and one requiring some little experience, it is by no means difficult. The most important point is that, the amount of carbon and nitrogen to be estimated being so extremely small, scrupulous care has to be taken that the reagents are pure, and that every trace of dust is rigidly excluded. In considering this process it is well to remember that carbon and nitrogen are present in water combined in several different ways. For instance : Carbon occurs (1) In organic matter. (2) In carbonic acid. (3) In carbonates. * Chemical News, vol. 38, p. 28. t Jour. Chem. foe., 1879, vol. i. p. 159, 22 WATER ANALYSIS Nitrogen occurs (1) In organic matter. (2) In nitrates. (3) In nitrites. (4) In ammonia. Before estimating the organic carbon and nitrogen it is necessary to eliminate as far as possible the other combina- tions of these elements. The carbonates are destroyed and the carbonic acid driven off by boiling with sulphurous acid, while the nitrates and nitrites are entirely decomposed by the addition of ferrous chloride. The free ammonia cannot at the same time be got rid of, hence, with the exception of a small loss by evaporation (which can be corrected for), it is fixed as sulphite, and the nitrogen in the free ammonia (after making the necessary correction) is deducted from the total nitrogen found by combustion. Albuminoid ammonia and organic nitrogen are practically synonymous terms, only that, as before stated, the albu- minoid ammonia represents only a portion of the organic nitrogen. One or two objections have been urged against this process for instance, that destruction of organic matter may occur during the evaporation with sulphurous acid ; also that a proportion of the organic matter is volatile. Edwin Lancaster, F.R.S., as early as 1828, clearly stated that organic matter is lost when a water containing it is evapo- rated ; Wanklyn * has shown that a proportion of urea is lost in this way, while fresh urine also lost some of its organic matter. Fresenius and others have proved the presence of volatile acids (acetic and butyric) in certain waters, these being formed by bacterial decomposition of carbohydrates they would escape during evaporation in an acid solution. Tiemann and Preusse have also drawn * Wanklyn, Jour. Chem. So-., 1867, p. 445 CHEMICAL EXAMINATION 23 attention to the decomposition which may occur on evapora- tion with sulphurous acid and ferrous chloride.* To obviate this loss, a process was devised by W. C. Young f for the estimation of both volatile and fixed organic matters, which is worth consideration, though the results obtained appear to vary more than can be considered consistent with real accuracy. For Frankland's process, in the preliminary treatment of the water, large flasks of a capacity of 1 J litres are required ; to make sure that they are free from dust, they should be rinsed first with sulphuric acid, and then several times with clean water, then allowed to drain before being used. When not in use these flasks are best covered with watch- glasses to prevent dust gaining access to them. One litre of the water is measured into one of the large flasks, 15 c.c. of a saturated solution of sulphurous acid (Appendix X) added, and the water boiled for a few seconds. In this way the carbonates are decomposed and the carbonic acid expelled ; at the same time the nitrates and nitrites are reduced, and their nitrogen is eliminated. After boiling, the water is ready to be evaporated. The apparatus used by Frankland for the evaporation consists of a self-filling water-bath upon which rests a flanged copper cup containing a little water, in which is floated the glass dish to contain the water to be evaporated. The flanged copper cup has a rim around its circumference, except at one point where there is a shallow depression which forms a lip, through which is passed a short piece of loose cotton wick which serves to drain off the condensed water into a jar on the bench. Resting on the flange of the copper cup is a cylinder of sheet copper, 3 in. high, which is slightly conical, and also provided with a flange for the * Jour. Chem. Soc. y 38, 29. t W. C. Young, Jour. Che;n. So:. Inlt., 1891, 883. 24 WATER ANALYSIS support of a tall, thin glass shade of the kind used for covering statuettes. In one side of the copper ring is a slit through which passes the tube of the flask. The glass dish is placed in cold water in the copper cup and gradually heated up ; it is then partly filled with the water to be evaporated. The remainder of the water is then poured into the flask, the FIG. 2. Apparatus used in the evaporation of water for determination of organic carbon and nitrogen. tube attached, and the whole inverted with the open end of the tube in the glass dish. During evaporation the flask is supported in the ring of a large filter-stand, out of which a segment has been cut to allow the neck of the flask to pass through. A weight is needed upon the wooden base of the stand to prevent it being overturned. The tube is provid_ed with a small side tube, which allows air to enter when the liquid has evaporated below the level of the junction, and thus allows more water to flow into the dish. When CHEMICAL EXAMINATION 25 inverting the flask and tube a small bubble of air is entrapped in the tube, and this serves as a trap which prevents con- vection currents causing the circulation of the liquid between the dish and the flask. If this is not done solid matter will be carried from the dish to the flask, and the experiment will, of course, be of no value. With this arrangement the evaporation of a litre of water may be concluded in from twenty-four to twenty-six hours that is, if commenced in the afternoon and the heat kept on all night the residue will be dry and ready for combustion some time in the after- noon of the next day. The above arrangement is not an absolute necessity in fact, it is so unwieldy that it is better dispensed with, especially when a number of evaporations are to be conducted at one time. The copper cup is placed upon an opening of an ordinary water-bath, a piece of wetted cotton wick laid upon the depression in the flange, and the cup partly filled with water. A glass dish is then carefully cleaned, rinsed with distilled water, and drained, but not dried ; it is then placed in the miniature water-bath formed by the cup. Over the dish is placed a glass shade to keep out the dust, and this rests directly on the flange of the copper cup (Fig. 2). Where a large number of analyses have to be made it is convenient to have a row of these water-baths arranged upon a stone bench covered with a ventilating hood con- nected to the chimney shaft. As soon as the water in the copper cup has become heated the glass shade is removed, and the glass dish filled up with the water which has just previously been boiled with sulphurous acid ; at the same time 2 c.c. of the saturated solution of sodium sulphite and two drops of ferric chloride solution (Appendix X) are added. The former serves to yield a residue which can be readily removed from the dish, and at the same time it 26 WATER ANALYSIS neutralises the effect of any free sulphuric acid formed when the nitrates are reduced by the sulphurous acid ; the ferric chloride is at once reduced to ferrous chloride, which ensures the destruction of any traces of nitrates or nitrites that may possibly be left unreduced. As the evaporation proceeds the dish is filled with water from the flask, and, in order that there may be no tendency to crack the dish by the addition of cold liquid, it is kept in a warm place so that the water has a temperature of about 60 C. In the evening the glass dish is rilled up with the water, and, if a small flame is left under the water-bath, a whole dishful of the water will have evaporated by the morning. The evaporation is continued until the whole of the water has gone and the residue in the dish is perfectly dry. The dish can then be kept in a desiccator until the combustion can be performed. Working in this way, the evaporation of a litre of water takes thirty-six hours ; that is, if it is commenced on the morning of one day and continued through the night it will be finished in the evening of the second day. In the case of a water containing a large quantity of nitrates, the sulphurous acid used in the preliminary boiling may not be sufficient to ensure the complete reduction of the nitrates and the expulsion of the whole of their nitrogen. Frankland therefore recommends that if the nitrogen as nitrates exceeds 0*5 part per 100,000, the dish containing the residue should be filled with organically pure distilled water, to which has been added one-tenth of its volume of the saturated solution of sulphurous acid, and the liquid again evaporated to dry- ness. If the nitrogen as nitrates exceeds 1 part per 100,000, then 250 c.c. of the 10 per cent, solution of sulphurous acid should be used ; if more than 2 parts, half a litre, and if more than 5 parts, one litre of the solution should be evapo- CHEMICAL EXAMINATION 27 rated. If less than one litre of the water is taken for the estimation of carbon and nitrogen, the quantity of sul- phurous acid solution employed will necessarily be smaller in proportion. In dealing with sewage and highly polluted waters it is advisable to take less than one litre for evaporation ; from 250 c.c. down to as low as 10 c.c. may contain quite sufficient organic matter for the estimation. The quantity to be taken must be decided upon after the estimation of free ammonia ; if the latter should be high it would almost certainly indicate the presence of a notable quantity of organic matter. During the evaporation of a water containing ammonia with sulphurous acid a certain proportion of the ammonia passes away. Dr. Frankland carefully investigated this point, and from experimental data constructed a table for the necessary corrections to be made (Appendix VI). These corrections are comparatively large, especially when the proportion of ammonia is high. For this reason he recom- mends that in the case of sewages 10 c.c. of a solution of metaphosphoric acid (Appendix X) should be used in the place of sulphurous acid. Metaphosphoric acid fixes the ammonia far more effectually than does sulphurous, hence the corrections required are smaller (Appendix VII). No preliminary boiling is required when phosphoric acid h used, nor must the acid sodium sulphite or ferric chloride be added, but in place of them about half a gram of pure ignited calcium phosphate is employed, in order to form a dry residue. Phosphoric acid does not decompose nitrates, therefore it cannot be employed when they are present. Nitrates are, however, never present in raw sewages, as they cannot exist in presence of decomposing organic matter. This being the case, phosphoric acid is preferable to sulphurous acid for this particular purpose. 28 WATER ANALYSIS By using borax or boric acid in place of sulphurous or phosphoric acids, the whole of the ammonia can be expelled, so that no correction is needed ; this will be found useful when very correct estimations of the organic nitrogen are required in presence of a large quantity of ammonia, but the organic carbon cannot be determined in the same residue, because boric acid does not entirely decompose carbonates. This necessitates a separate estimation of the carbon, using sulphurous acid as previously described. There seems to be no reason, however, why a combination of the two methods could not be used, boric acid being added during the first part of the evaporation to expel ammonia, and subsequently a little sulphurous acid to decompose carbonates and nitrates before the completion of the process. For the combustion of the water residue it is best to use combustion tubing of Jena glass of rather more than \ in. internal diameter ; this^is cut up into lengths of about 18 in., and these are very carefully cleaned by running water through them ; then a plug of cotton-wool attached to a string is pulled several times through the tubes, so as to loosen any particles of dust which may still adhere ; water is again run through them ; lastly they are then rinsed with distilled water and stood on end in a warm place to drain and dry. As soon as the tubes are dry they are sealed off at one end in the blowpipe flame, and the open ends covered with caps of filter-paper to prevent dust getting in. The glass dish containing the water residue is placed on a sheet of white paper sprinkled with powdered copper oxide (Appendix X), and the residue detached from the dish by scraping with a very flexible steel spatula. A little more of the fine oxide of copper may be rubbed up with the residue, and the whole transferred to the combustion tube. The combustion tube is first charged with about 1 in. of coarse copper oxide (Appendix X) ; then follows the CHEMICAL EXAMINATION 29 water residue mixed with the fine copper oxide, which is scooped out of the dish by using the open end of the tube, the last portions of the residue being transferred by means of a bent card. A little more powdered oxide of copper is sprinkled over the dish, again scraped down and transferred as before, then the tube is filled for a length of 10 in. with granular copper oxide, a small copper-gauze coil is put in, then about 1 in. of granular copper oxide, and (to keep all in position) this is followed by a small plug of asbestos, which is not rammed in too tight ; finally the end of the tube is drawn out and bent in the blowpipe flame, as shown in the figure. During the filling of the tube the oxide is shaken down by tapping the closed end of the tube on a sheet of asbestos millboard, in order that there may be no empty spaces liable to collapse under a vacuum at the high temperature used during the combustion, but the residue is not to be too closely consolidated, or air may remain in the end of the tube. To obviate this it is best, after the tube is filled, to lay it in a horizontal position and tap it a few times, so as to form a small air channel along one side. The apparatus used for the combustion consists of a small combustion furnace, and a mercury pump of the Sprengel or Topler type for exhausting the tube, the combustion being performed in a vacuum. The Sprengel pump is an ingenious arrangement for pro- ducing an almost perfect vacuum. It consists of a long syphon tube (Fig. 3), the shorter limb of which (A) is con- nected with a wide glass tube (B) and a large glass funnel (C) by means of very stout rubber pressure-tubing. The latter must be the thickest and strongest rubber tubing which can be obtained, as it is required to withstand^ considerable pressure of mercury. At D and E clamps are fixed for regulating the flow of the mercury. The longer limb of the f Combustion Tube Filled FIG. 3. Apparatus for combustion of the water residue in vacuo. Frankland's method for determining organic carbon and nitrogen. CHEMICAL EXAMINATION 31 syphon, F, which is bent upwards at the end, and the junction, G, are of small-bore tube. The junction is covered, when in use, by a seal of glycerine consisting of a wider glass tube fitted with a sound ordinary cork so that it may be pushed up or down as required. With the object of removing any air-bubbles carried down with the flow of mercury, a second smaller funnel with a long narrow tube is fixed in the wider tube, B, and held in position by the clamp, or a second syphon tube, H, is interposed, similar to the one described, except that the two limbs are nearly the same in length, and that in place of the straight junction there is a small funnel fused on the bend through which any air-bubbles can escape. The combustion tube is connected to the Sprengel pump by means of a piece of capillary glass tubing, K, bent as shown in the figure, and the two joints are made with thick- walled rubber pressure-tubing, which is drawn well up and wired on so that the glass tubes are pressed well together. To obviate the danger of air being drawn through these joints, they are both covered with liquid seals, glycerine being used in the tube G, and a small rectangular zinc trough filled with water is fixed in position at I before com- mencing the combustion ; the latter also serves to condense any water which may be given off during the combustion of the water residue. The combustion tube is placed in the furnace and the junction also made with the tube K, then the water seal may be placed in position and two of the burners in the front end of the furnace lit in order to heat the copper coil and a portion of the copper oxide. To prevent any heat at this stage reaching the water residue, a small sheet-iron screen can be put in behind the two front burners if it is found necessary. The pinchcock at E may now be loosened and the mercury 32 WATER ANALYSIS allowed to flow slowly through, ttte tube. As the mercury passes the junction at G, air is drawn from the combustion tube and a series of pistons of mercury and air pass down the limb F, the air subsequently escaping in bubbles through the mercury in the trough. After a time it will be noticed that the air spaces become smaller and smaller, and eventually there will be an undivided column of mercury of the baro- metrical height (i.e. about 30 in.), and each pellet of mercury passing the bend will fall rapidly in the tube, striking the top of the column with a decided click, indicating that a vacuum has been produced in the tube. If any difficulty be found in removing the last traces of air, the mercury may be allowed to flow much more quickly until the desired object is attained, whereupon the pump is stopped and a small gas-measuring tube, previously filled with mercury and inverted in the trough, is brought over the bent limb of the Sprengel and held in position by means of a clamp. The combustion proper may now be proceeded with by gradually turning on the burners, one or two at a time, and putting on the clay tiles, the temperature being gradually raised until the whole of the combustion tube is at a bright red heat. As the gas is evolved from the tube the tension will be relieved and the mercury in the limb F will be seen to fall, and if the total gas amounts to only a few c.c., nothing will escape from the Sprengel pump. As soon as the combustion tube is brought to a bright red heat throughout, the combustion will be completed, and the supply of gas may then be cut ofE ; the furnace is allowed to cool somewhat, say for ten minutes, and the gas then slowly pumped over into the measuring tube. It is not advisable to pump over immediately the combustion is completed, as the combustion tube, being softened by the heat, might possibly collapse under a vacuum; nor is it wise to wait CHEMICAL EXAMINATION 33 till the tube is nearly cold owing to the risk of its cracking during the cooling. A simple form of gas-measuring tube is shown at J ; this is a thick-walled glass tube about \ in. in diameter, narrowed to about J in. at the upper end. The total capacity of the tube is 20 c.c., the lower part being graduated inj 1 ^ c.c's and the upper part in -$ c.c's. Before filling with mercury, it is moistened with a drop of water, so that the gases are measured in a saturated condition. As soon as the whole of the gas has been pumped over, the flow of the mercury in the Sprengel pump is stopped and the gas tube removed to a cylinder of mercury. After standing for about ten minutes for the gas to assume the temperature of the laboratory, the measuring tube is depressed uitil the level of the mercury, within and without, is the same, and the volume of the gas then read off. A few drops of a concentrated solution of caustic potash are now transferred to the tube, this being accomplished by raising the tube in the mercury and blowing the liquid from a small pipette (Fig. 4), which is provided with two bulbs to ensure that no air passes along with the liquid into the tube. The solution is shaken with the gas until the absorption is complete, after which the tube is again depressed and the volume of the residual gas measured. The gas absorbed by the caustic potash is carbonic acid, and the residual portion nitrogen. In all combustions a small proportion of the nitrogen is evolved as nitric oxide, but the quantity of the latter is rarely more than one-tenth of the volume of the nitrogen. One-half of this consists of nitrogen, hence the error due to this cause is only about one-twentieth of the total nitrogen, and therefore may with safety be neglected. If extreme accuracy is required, the gas is transferred to a gas-analysis c 34 WATER ANALYSIS apparatus, such as that of Frankland, in which it can be more carefully analysed. Dr. Frankland states that the gas may, in addition to the above, contain traces of oxygen and sulphurous acid, and he gives the methods of separating these gases. If FIG. 4. Pipette for caustic potash solution. nitric oxide is present, and this is almost invariably the case, the gas is moist and cannot, of course, contain oxygen. Sulphurous acid is entirely absorbed by the moisture on the sides of the tube, so that it separates without any treat- ment. The gas formed during the combustion may there- fore be treated as a mixture of carbonic acid and nitrogen, and the usual method of estimating the proportions of these two gases is all that is required. The height of the barometer and the temperature of the CHEMICAL EXAMINATION 35 room having been observed, the data required for the deter- mination of the organic carbon and nitrogen are complete and all that remains is the calculation. The reagents used in the analysis are never perfectly pure ; therefore it is necessary to perform a blank com- bustion with each batch of copper oxide, adding the same quantities of the reagents as are used for an actual com- bustion to a litre of organically pure distilled water, evapo- rating and conducting the combustion as already described. The following figures may be regarded as average cor- rections to be applied : Corrections required Organic Organic carbon nitrogen For one litre of water . ' . 0'00027 0*00005 Parts per 100,000 . . 0-027 0'005 A table is given in Appendix VI for the necessary cor- rections due to loss of ammonia ; the correction there given must be deducted from the calculated amount of nitrogen in free ammonia, and the result deducted from the total nitrogen to obtain the organic nitrogen. No correction is required if the free ammonia is less than 0'009 parts per 100,000. Calculation of the Results. The reduction of 1 c.c. of nitrogen to its equivalent weight at any given temperature 0-0012562 is obtained by the formula Q'003670 760' w ^ c ^ ^ as been converted into logarithmic form for each tenth of a degree from to 30, the figures being given in Appendix V. The calculation is simplified if the carbonic acid is calculated in terms of nitrogen, the figure thus obtained, multiplied by f , then giving the organic carbon. One set of logarithms 36 WATER ANALYSIS thus serves for both, calculations. This will be clearly seen by comparing the following : C0 2 = N 2 = C or N x f = C. 44 = 28 = 12 or 7 = 3. An example will perhaps suffice to make the method of calcu- lation quite clear. One litre of water yielding the following : Total gas . 4*0 c.c. Absorbed by potash (C0 2 ) 3'8 c.c. Unabsorbed by potash (N) . 0-2 c.c. Free ammonia 0*009 = to nitrogen 0'007 Loss of nitro- gen during evaporation O'OOO To deduct from total nitrogen . 0*007 per 100,000 Barometric reading, 750 mm. Temperature, 18 C. Tension of aqueous vapour at 18 C. (Appendix IV) = 15*4 mm. Organic Carbon Log of 1 c.c. N at 18 . . . = 6*19046 750 - 15-4 . = 2-86610 3-8 = 0-57980 Log wt. of C0 2 in terms of N . 3'63636 Weight of C0 2 in terms of N, 0'00438 x f = 0'00185. 0-00185 -0-00027 (error due to chemicals) = 0'00158 C. Organic carbon = 00158 gram per litre, or 0'158 part per 100,000, CHEMICAL EXAMINATION 37 Organic Nitrogen Log of 1 c.c. N at 18 . . . . = 619046 760 - 15-4 . = 2-86610 ,,0-2 = 1-30100 Log wt. of N . . . . 4-35756 Weight of N, 0*0002278 ; - error due to chemicals '0000500 ; = 0-000178 gram N per litre. Organic nitrogen = 0'018 - 0'007 = O'Oll part per 100,000. The amount of organic carbon in a deep well water of good quality does not exceed 0'06 part per 100,000, and the organic nitrogen 0'02 part per 100,000. In upland surface waters the quantities are greater, owing to the presence of peaty matter, being about 0'30 part and 0'03 part respectively. It is therefore necessary, in judging the quality of a water, to take into account the origin of the sample. Another point which may influence the decision of the analyst is the relationship between the organic carbon and nitrogen. In waters con- taining only vegetable organic matter in solution, such as upland surface waters from uncultivated districts, the ratio C : N is very high, i.e. about 10 : 1, but many rise even as high as 20 : 1, or may fall to 6 : 1. If the ratio is less than 6:1, animal contamination of some kind may be suspected, either drainage from cultivated lands or sewage. In waters contaminated with animal matter the ratio falls to 3:1, or even lower for in- stance, in sewage it may be 1 : 1 ; on the other hand, it may be as high as 9 : 1 where the soil is porous and active oxidation of the organic matter is taking place as a consequence of intense bacterial action. The presence of nitrates or nitrites in quantity in such waters would, however, show that previous sewage contamination had existed ; and if from any cause, such as a flood or the gradual consolidation of the soil, the 38 WATER ANALYSIS bacterial activity should cease, unaltered sewage might pass into the supply. Thus in shallow well water any sign of contamination, past or present, even though slight, should be regarded with grave suspicion ; the purity of the water cannot be judged by the amount of organic matter alone, as this may have been almost entirely destroyed by oxidation, and yet disease germs remain. In deep well waters the ratio C : N is low, being 5:1, but this is of little importance, as these waters contain only very small quantities of carbon and nitrogen. It shows, however, that during oxidation of organic matter the nitrogen in the residual portion is rather more resistant than the carbon. Dr. Frankland places waters under two different categories, Upland Surface Waters and Water other than Upland Surface, and divides them into classes according to their content of organic elements (carbon and nitrogen), thus : Water of great organic purity UPLAND SURFACE WATER OTHER SOURCES Containing not Containing not more than more than 0'2 part per O'l part per 100,000 100,000 Water of medium ) . _ , \ 0'2 to 0'4 part O'l to 0'2 part purity J Water of doubtful ) . . > 0'4 to 0'6 part 0'2 to 0'4 part purity J ( More than 0'6 More than 0*4 Impure water | part part NITBOGEN AS NITRATES The nitrogen present in the form of nitrates and nitrites is derived from organic matter containing nitrogen by oxidation, and must be regarded as evidence of past contamination. This oxidation is brought about by bacteria and occurs in CHEMICAL EXAMINATION 39 several stages, in each of which certain organisms preponderate. In the first stage the organic matter is broken down into simpler forms ; much of it is oxidised, the carbon appearing as carbonic acid and the nitrogen as free nitrogen or as ammonia. If this decomposition takes place out of contact with air, the change is brought about by anaerobic organisms, the carbon then passing of! largely as methane, accompanied by hydrogen, while sulphuretted hydrogen is formed from the sulphates present. Thus the black colour of sewage and of the sewage mud is due to sulphide of iron. In the second stage, in contact with air, the carbonaceous matter is practi- cally destroyed, the nitrifying organisms convert the ammo- nia into nitrites, and finally into nitrates. The oxidation of organic matter is greatly hastened by perfect aeration, hence in porous soils sewage is rapidly destroyed, and the only products of the sewage which may find their way into wells in the vicinity are nitrates and sometimes nitrites, which are in some cases present in comparatively large amount. The bacterial method of treating sewage is an adaptation of this natural oxidation, the destruction of practically all the organic matter being accomplished by a few hours' contact with a bed of porous material, such as coke or clinkers, upon which a mass of the mixed organisms has been allowed to grow. The nitrogen of the organic matter is only partly converted into nitrates, a large proportion being evolved as free nitrogen, and some possibly being lost as ammonia, the nitrogen appearing in the oxidised state in a purified effluent being only about half the amount of that present in the original raw sewage. In the first stage of oxidation mentioned the liquid is strongly alkaline owing to the presence of the ammonia ; as soon as the nitrifying organisms become active the liquid becomes acid ; the soil is then acted upon, becoming very porous, and the reaction is accelerated, and thus a large amount of solid matter passes into solution. It is almost invariably 40 WATER ANALYSIS the case that when the nitrates are high the solids in solution are very considerable. Thus in the second stage of the oxidation of nitrogenous matter the reaction is accelerated if sufficient bases are present to neutralise the free acid and the liquid remains neutral. As an illustration of this may be quoted the analyses given by Frankland,* from which it is seen that the waters from deep wells and springs in calcareous strata contain as a rule far more nitrates than those from other deposits ; especially remarkable in this respect are the supplies from the magnesian limestone, which rock is well known to be a very porous material. For the estimation of the nitrates in water there are quite a number of methods, and from them the author has chosen four for description, these being accurate when properly carried out, and not too complicated in the working. They are the indigo process of Warington, Crum's method, the copper-zinc couple of Gladstone and Tribe, and the phenol- sulphuric acid method. 1. The Indigo Process. The indigo process depends upon the reaction between indigo and nitric acid, nitric acid con- verting the blue indigotin into yellow isatin. C 8 H 5 NO + = C 8 H 6 N0 2 . The process is an empirical one and requires a little experi- ence, as the same method of working must be strictly adhered to in all cases, otherwise the results will be hopelessly wrong. The method of working is that of Marx as modified by Warington, who was the first to make of it a really workable process. Certain other modifications have, however, been ntroduced which render it more simple in operation. Instead of preparing a series of standard solutions of nitre as given in Frankland's Water Analysis (p. 31) only two need be kept, and the heat required for the reaction is produced by * Water Analysis, Appendix, p. 116. CHEMICAL EXAMINATION 41 using a mixture of ordinary and Nordhausen sulphuric acids instead of a calcium chloride bath. Ordinary sulphuric acid alone does not give sufficient heat to make the process a quantitative one. The working solution of nitre is of ^- strength, made by dilution of stock solution. The indigo solution is to be previously standardised against this as given in Appendix X. The sulphuric acid used is a mixture of 1 part of Nordhausen sulphuric acid of the best quality and 3 parts of pure sulphuric acid (free from nitrates). 20 c.c. of this mixture should give when quickly mixed with its own volume of water an initial temperature of 180 C. For the determination of nitrates in an ordinary water, as a preliminary test take 20 c.c. of the sample into a Jena beaker of 20 oz. capacity ; place this on a white plate and run into it 5 c.c. of the standard indigo solution from a burette (Fig. 5). Now measure into a graduated cylinder 27 c.c. (25 c.c. + 2 c.c. for drainage) of the mixed acids, and quickly pour it into the centre of the water, rotating the beaker gently with the left hand so as to bring the two liquids into intimate contact, but without undue agitation. If the blue colour is discharged, run in more indigo rapidly from the burette, keeping up the rotation all the time until the liquid assumes a permanent faint blue colour. The observation of the colour can best be made by holding the white plate behind the beaker in an inclined position, so that it acts as a reflector. The first experiment is rarely accurate, because the temperature may fall so low during the titration that the reaction is not complete, and the amount of indigo then required is far below the full amount. The number of c.c's of indigo used in the first experiment is noted, and in the second experiment this quantity is added to the 20 c.c. of water in the beaker, a corresponding amount of the mixed acids being employed EO that the liquid may be 42 WATER ANALYSIS raised to the desired temperature. In subsequent estimations run into the beaker the quantity of indigo solution required in the previous one, and after a little practice the determination FIG. 5. Apparatus for determination of nitrogen as nitrates and nitrites. Indigo process. will be found a matter of very little difficulty. If the quantity of nitrates is high, so that more than 20 c.c. of the indigo solution are required, it will be best to dilute the sample 1 in 2 or 1 in 4, as the case may be, until about 10'5 c.c. of CHEMICAL EXAMINATION 43 the indigo solution are required, that being the quantity for which the test is most accurate. It will be seen from the table, page 114, that the amount of indigo oxidised is not strictly in proportion to the nitrate present, less and less of the former being required for proportional increases in the amount of nitrates. If, on the other hand, after addition of 5 c.c. of the indigo solution the colour is not discharged when the mixed acid is added, the amount of nitrates can be but small ; therefore in the second experiment only 0'5 c.c. of the indigo solution should be added to the water before the acid, and if it should be required a further quantity may be run in after the colour is discharged. A blank experiment should be performed with 20 c.c. of distilled water, 0'5 c.c. of the indigo solution, and 20 c.c. of the mixed acid ; if the latter is free from nitrates the colour will not be discharged. Should, however, a trace of nitrates be found to be present, the number of c.c's of indigo solution required in this blank test must be deducted in all subsequent estimations. In this process the nitrites are estimated and expressed in terms of nitrogen as nitrates, the amount being found by reference to the table (Appendix VIII). 2. drum's Method. In this process a concentrated solution of the -soluble solids is prepared and acted upon by sulphuric acid in presence of mercury, the nitric oxide evolved being measured and then calculated to its equivalent of nitrogen. For the determination, the total solids obtained by evapo- rating 500 c.c. of the sample may be employed, but if the nitrates are present in large quantity a smaller volume of the water 250 c.c. or 100 c.c. should be evaporated specially for the purpose. To the dry residue in the dish add 2 or 3 c.c. of hot distilled water and loosen the solid matter by means of a glass rod covered with rubber tube ; pass the solution through a small filter paper and collect the filtrate in a clean dish, wash the 44 WATER ANALYSIS residue once or twice with the same quantity of hot water, and then concentrate the liquid to about 1 or 2 c.c. The nitrometer used in the estimation consists of a thick FIG. 6. Apparatus for estimation of nitrogen as nitrates and nitrites. Crum's method. glass tube (Fig. 6) about 8 inches long and J inch internal diameter, provided with a small cup and a stopcock at one end, the other end being open. It is graduated in -^ c.c's. The nitrometer should be carefully filled with mercury, inverted in a glass cylinder containing mercury, and held in CHEMICAL EXAMINATION 45 position by means of a clamp. The solution of the water residue should be poured into the cup of the nitrometer, and by opening the stopcock and raising the tube the whole of it can be carefully drawn into the interior of the tube. The beaker should be washed out once or twice with a little strong sulphuric acid, and the rinsings also transferred to the nitro- meter the volume of acid used being about one and a half times that of the solution. If a trace of gas is immediately evolved it will consist of carbonic acid liberated from soluble carbonates ; this must be removed by opening the stopcock and depressing the tube in the mercury. The open end of the nitrometer must now be covered with the thumb and the tube shaken with a rotary motion so as to subdivide the mercury into small pellets on the surface. If nitrates are present these pellets of mercury will assume a leaden appearance and bubbles of gas will at once appear, considerable pressure being felt against the thumb. The tube should now be replaced in the mercury, but it should be shaken again from time to time until the action ceases and the mercury becomes quite clean. The gas evolved is nitric oxide, formed by the action of the sulphuric acid and mercury upon the nitrates in the water. When the action is quite completed the nitrometer should be depressed in the mercury until the levels within and without are the same, and the volume of the gas may then be read off. Nitric oxide (NO) contains half its volume of oxygen ; therefore if 500 c.c. of water are taken for the estimation the volume of nitric oxide evolved will be equal to the amount of nitrogen as nitrates and nitrites present in 1 litre of the sample, and the amount of nitrogen present as such in 100,000 parts of the water is calculated in exactly the same way as for organic nitrogen, using the table in Appendix V, the factor 0-0012562 _, for 1 c.c. of N bemg ___ Thus, supposmg 46 WATER ANALYSIS 3 c.c. of nitric oxide is evolved from 500 c.c. of the water, this would be equal to 3 c.c. of nitrogen in 1 litre of water, or 300 c.c. in 100,000 c.c. The temperature being 20 C. and the barometric pressure 750 mm., then Log of 1 c.c. N at 20 C. . 618748 Log of 750 . . . . . 2-87510 Log of 300 . ' . . . . 2-47710 Log wt. of N . . . . 1-53968 = to 0*346 part N as nitrates and nitrites per 100,000. If the water contains both ammonia and nitrites, these may react to form ammonium nitrite, which would decompose on evaporation with loss of nitrogen. For this reason the portion taken for the estimation of the total solids could not be employed. A fresh portion is therefore taken, and previous to evaporation it should be acidified with one or two drops of sulphuric acid and a dilute solution of potassium permanganate added, drop by drop, until a faint but permanent pink colour is produced. The liquid is then rendered very faintly alkaline with sodium carbonate, and the evaporation proceeded with. By this method of treatment the nitrites are converted into nitrates and the loss of nitrogen is obviated. 3. Electrolytic Method Copper-zinc Couple of Gladstone and Tribe. Gladstone and Tribe showed that zinc coated with finely divided copper acts as a powerful reducing agent, the products being, in the case of water, hydrogen and zinc hydrate. Zn + 2H 2 = Zn(OH) 2 + H 2 . When nitrates are present they are reduced by the nascent hydrogen first to nitrites and then to ammonia, the final change being shown in the equation 2KN0 3 + 8Zn + 12H 2 - 2KHO + 8Zn(OH) 2 + 2NH 3 . This method of reduction was adapted by Williams for the CHEMICAL EXAMINATION 47 determination of small quantities of nitrates and nitrites such as are contained in ordinary drinking waters. The copper-zinc couple is prepared from thin sheet zinc by cutting it into strips about 1 inch long and J inch wide ; these are first boiled in caustic soda solution to remove grease and washed, then immersed in a weak (i.e. about 3 per cent.) solution of copper sulphate until they have become evenly coated with a thin black coherent film of metallic copper : the solution is then poured off and the copper-zinc couple washed several times with distilled water. About 20 grams of the zinc thus coated are placed in a flask along with 100 c.c. of the water, the flask being closed with a rubber stopper and allowed to stand in a cool place for twelve to twenty-four hours, when the reduction will be completed. The water is then decanted into a distillation flask, and the copper-zinc couple washed once or twice with a little distilled water, which is added to the original solution. Distillation is then proceeded with, and when 50 c.c. have passed over, the receiver is changed and a second 50 c.c. collected. The whole of the ammonia is contained in the two distillates. The second 50 c.c. should be tested first, 2 c.c. of the Nessler's solution being added as in the estimation of free ammonia. If an appreciable quantity of ammonia is found to be present in this distillate it will be necessary to dilute the first distillate before te3ting, taking 5 or 10 c.c. as* the case may be and diluting to 50 c.c., the results being multiplied by 10 or 5, according to the dilution. If the water contains free ammonia the amount found must be deducted from the total ammonia, and the remainder produced from the nitrates and nitrites is calculated as follows : Suppose that 100 c.c. of water after action of the copper- zinc couple has been distilled, the first 50 c.c., after diluting 5 c.c. to 50 c.o.. yielding a colour equal to 2*5 c.c., and the second 50 c.c. without dilution a colour equal to *5 c.c. of the 48 WATER ANALYSIS standard ammonium chloride solution. Suppose also that the water contains '025 part of free ammonia per 100,000. Then Standard solution First 50 c.c. = 2'5 x 10 = 25*0 c.c. Second 50 c.c. = -5 c.c. Total 25-5 c.c. 100 OOO 25-5 x '00005 x ' = total ammonia 1-275. 100 (1'275 '025) x -^ = T03 parts of nitrogen as nitrates and nitrites per 100,000. Dr. Thorpe recommends boiling the water with a minute fragment of quicklime for the purpose of expelling the free ammonia previous to the action of the copper-zinc couple. It is doubtful, however, if this is advisable, as it may cause decomposition of some of the nitrogenous matter. The matching of the tints with the standard solution must be quickly performed, otherwise owing to the fact that they deepen on standing the amount of ammonia may be much over-estimated. 4. Phenol-sulphuric Acid Process (for nitrates only). This process depends upon the fact that when phenol is acted upon by nitric acid it is converted into trinitrophenol, or picric acid, which has a yellow colour, rendered much deeper by addition of excess of ammonia. The reaction is as follows : C 6 H 5 (OH)> 3HN0 3 - C 6 H 2 (N0 2 ) 3 (OH) + 3H 2 0. This reaction does not take place with nitrites ; these form nitrosophenol, which is practically colourless. For the estimation of nitrates by this method take 50 c.c. of the water to be tested and evaporate it to dryness in a porcelain dish on the water-bath. Add 2 c.c. of the phenol- CHEMICAL EXAMINATION 49 sulphuric acid (Appendix X) and 2 c.c. of concentrated sulphuric acid. Rotate the dish until the whole of the water residue is moistened with the acids, then heat on the water- bath for fifteen minutes. Now add about 25 c.c. of distilled water to the contents of the dish, then ammonia in slight excess, pour the liquid into a Nessler cylinder and make up to 50 c.c. with distilled water. After observing the depth of the yellow colour a series of blank tests should be made by measuring different quantities of the standard solution of potassium nitrate (Appendix X) in separate dishes, treating them in the same way and sub- sequently comparing the tints with that produced by the sample of water ; for instance, 1, 2, and 3 c.c. respectively may be taken, and if the tint of the water is deeper than that of 2 c.c. but not so deep as that of 3 c.c. then a fourth test may be made with 2*5 c.c., and so on till the colour is exactly matched. As only a few c.c's are to be evaporated this does not occupy much time and the colours are quite permanent. It is, however, simpler to use only one standard which will give about the same tint as the sample and then to dilute either the sample or the blank test, whichever may be the deeper, until 50 c.c. of each correspond exactly in colour. The calculation of the quantity of nitrate present can then be made if the amount of dilution be taken into account. For instance, suppose that 5 c.c. of the standard nitrate solution, treated as above and diluted to 50 c.c., gives a deeper colour than 50 c.c. of the sample, and that when diluted with water till 50 c.c. has the same tint as the sample the total volume of the liquid is 123 c.c. Then the calculation is as follows : 50 100,000 0001 x5 XT^T X ^r =-406 part N as nitrates per 100,000. \.2to OU If the colour of the sample is deeper than that of the blank test the former must be diluted ; in this case the figures 50 and 123 in the calculation would be reversed. D 50 WATER ANALYSIS The depth of tint is influenced considerably by the time of heating and other factors, for which reason the standard method of working should be strictly adhered to in all cases both in testing the sample and in the preparation of the tints for matching, otherwise the results will be of no value. With reasonable care the process may be regarded as an approxi- mately accurate one, and being easy to perform and requiring very little time it will be found especially useful when a large number of determinations are required as quickly as possible. Qualitative Test for Nitrates Nitrates may be tested for qualitatively by adding a few drops of an alcholic solution of diphenylamine and one or two drops of dilute sulphuric acid ; in presence of nitrates a deep blue colour is developed. This will readily detect 1 part of nitrogen as nitrate in 200,000 parts of water, and correspondingly smaller amounts by previous evaporation of the sample. NITROGEN AS NITRITES Nitrites are produced from ammonia by the aerobic action of the nitrifying organisms, but under ordinary conditions the oxidation is quickly carried further to nitrates, so that they are rarely present in large amount. They are often formed by the reducing action of organic matter on nitrates, and in a few cases have been found to be present in uncon- taminated well waters in association with iron, which subse- quently deposits as ochre. This may be explained by assuming that the water has come in contact with some mineral containing iron, such as iron pyrites. A few instances have been recorded in which nitrites have been found in well waters owing to the reduction brought about by galvanised iron pipes or tanks. Nitrites are often present in considerable quantities in sewage effluents from " contact " beds, and also CHEMICAL EXAMINATION 51 in polluted shallow well water. They are never present in peaty waters. The presence of nitrites in a water should, however, always be regarded as a suspicious circumstance ; it is most fre- quently a sign of sewage contamination. It is rarely necessary to estimate the nitrites separately, as they are included with the nitrates in most of the processes already described. They may be tested for qualitatively and returned as a minute trace, a trace, an appreciable quantity, or a considerable quantity, as the case may be. The estimation of nitrites is performed colorimetrically by means of Greiss's test with metaphenylene-diamine (diamido- benzine), the other colour reactions given under the head of qualitative tests not being suitable, as the colours darken so rapidly that an accurate measure of the tints is out of the question. 100 c.c. of the water to be tested are placed in a Nessler cylinder, 1 c.c. of the metaphenylene-diamine solution and 1 c.c. of dilute sulphuric acid (Appendix X) are added and the whole well agitated. After standing about five minutes, three portions of the standard solution of potassium nitrite (Appendix X) are measured off from a burette into separate cylinders, for instance, '5 c.c., TO c.c. and 2 c.c. respectively, or whatever quantities may be judged necessary to form a similar tint to the sample, and, after making up with distilled water, a like quantity of metaphenylene-diamine solution and sulphuric acid are added. After shaking, these comparison tests are labelled and placed on the white plate along with the sample to be tested. After the lapse of half an hour, the sample is compared with the three standards, the one most nearly approaching it in tint indicating the amount of nitrite in the sample. If none of the tests exactly match the tint of the water, a second series of experiments is performed with a fresh sample of the water, and three other comparison tests, the quantities 52 WATER ANALYSIS of the nitrite solution to be taken being indicated by the preliminary tests. The comparison may also be made by the method of dilution as described in the estimation of nitrites by phenol-sulphuric acid, but if this is done, the amount of metaphenylene-diamine solution in the diluted sample should be made up to 1 c.c. As the colour produced by the action of nitrites on meta- phenylene-diamine deepens appreciably with lapse of time, it is absolutely necessary that the tests once started should be completed without delay in order that the conditions may be as nearly constant as possible. If a deep yellow colour is obtained immediately after the addition of the reagents, it will be found difficult to match ; therefore it is better in such a case to take only 10 or 20 c.c. of the water and dilute to 100 c.c. with distilled water for the estimation, subsequently making allowance for the dilution in the calculation. 1 c.c. of the standard solution of potassium nitrite = '0001 gram of N 2 3 . Qualitative Tests for Nitrites Greiss's test may be used for the detection of nitrites, but the two tests given below are even more delicate. (1) To 100 c.c. of the water to be tested add three drops of naphthylaminehydrochloride solution, two drops of sulphanilic acid solution, and one drop of dilute hydrochloric acid, shake and allow to stand. If nitrites are present a rose-red colour will appear in about ten minutes and will deepen considerably on standing. This will detect 1 part of N 2 3 in 1000 millions. (2) Add a few drops of potassium iodide solution, a few drops of starch solution, and one drop of dilute sulphuric acid . In presence of nitrites a blue colour quickly forms which leepens indefinitely on standing. Nitrates and nitrites are formed from the nitrogen of organic matter by oxidation. Very little, if any, is produced from vegetable matter, practically all from animal matter. In upland surface waters they are either absent or present only CHEMICAL EXAMINATION 53 in traces. In deep well waters they exist to the extent of 0*25 to as much as 2'0 parts per 100,000 ; in shallow well waters the ratio is sometimes as high as 5'0 parts. In raw sewage there are no nitrates or nitrites ; it is only towards the end of the oxidation, when most of the organic matter has been oxidised, that they appear. Nitrates being quite harmless in themselves it would not be wise to condemn a sample of water containing them unless they were accompanied by other products of the oxidation of sewage, as, for instance, nitrites, or ammonia. If, however, they should be present in large amount, that is, more than '025 part of N in an upland surface supply or more than 0*5 part in a well water, it would be well to see that the surround- ings were quite free from contamination before giving a certificate of purity. OXYGEN ABSORBED Forchammer's Process. In the estimation of the oxygen absorbed a dilute solution of potassium permanganate is employed. This process was first used by Forchammer in 1849, hence it is known as the Forchammer process, but in the hands of other chemists it has been more or less modified. It can only be regarded as an empirical method, because it does not serve to estimate any particular constituent. Waters containing relatively large proportions of organic matter absorb considerable quantities of oxygen, but the amount of oxygen used up is dependent more upon the nature of the organic matter than upon its amount, some organic substances being much more readily decomposed than others, and therefore absorbing correspondingly large quantities ot oxygen. Thus Dr. Tidy found that the relative proportions of oxygen absorbed in three hours by solutions containing three grains per gallon of various organic matters were as follows : Urea, ; sugar, '003 ; gum, -007 ; starch, '014 ; gela- tine, *021 ; hippuric acid, '046 ; uric acid, '282 ; strychnine, 54 WATER ANALYSIS '775 ; and morphine, T450 grains per gallon. These figures clearly show that the amount of oxygen absorbed from per- manganate bears no relationship to the amount of organic matter present, but that it is influenced considerably by the constitution of the material. Dealing with waters from one source only, as, for instance, upland surface supplies containing peaty matter in solution, the amount of oxygen absorbed may, however, be taken as a criterion of the quantity of organic impurity present. Frank- land has compared the amount of oxygen absorbed with the quantity of organic carbon and finds the relationship to be as follows : Oxygen Carbon River waters from Thames and Lea .1 2*38 Deep well waters . . . .1 5*8 Shallow well waters . . . .1 2 '28 Upland surface waters . . .1 T8 For the complete oxidation of carbon to carbon dioxide, 1 part of oxygen would be equivalent to '375 of carbon, so that in all the above cases the reaction falls far short of what would be required for complete oxidation. Various methods of conducting the test have been proposed from time to time. Forchammer determined the amount of oxygen consumed by warming the water with permanganate, but it is now usually carried out at the ordinary temperature of the laboratory or at some fixed temperature as, for instance, 80 F., as recommended by the Water Committee of the Society of Public Analysts. The tests are certainly more to be relied upon if performed at a definite temperature, and this may be fixed at 60 F. The permanganate is usually added in excess in an acid solution, and, after the lapse of a definite time, the surplus is determined. Usually two tests are performed, one after an interval of fifteen minutes, the other after three hours. (Tidy gave one hour and three hours.) In the case of sewages the times are three minutes and four hours. CHEMICAL EXAMINATION 55 The three-minute test is supposed to represent the nitrites (in absence of sulphuretted hydrogen), but as even in so short time quite an appreciable quantity of organic matter is oxidised this idea is no longer tenable. Several other modi- fications have been tried, as, for instance, boiling in an alkaline solution, and though the figures may vary according to the conditions of the experiments, not one of the methods leads to a total oxidation of the organic matter present, therefore a multiplication of methods is anything but desirable. Heat- ing the sample with permanganate in acid solution certainly would be altogether out of the question, as this results in the evolution of chlorine from the chlorides and the reduction of considerable quantities of permanganate. As this might possibly take place even at moderate temperatures, Dr. Dupre preferred to work at a temperature of C. For the determination of the oxygen absorbed it is con- venient to use stoppered bottles of 500 c.c. capacity, two of these being required for each sample, and a third for the comparison test which it is necessary to do each day in order to check the strength of the thiosulphate, as this rapidly deteriorates on standing. The bottles are first cleaned by rinsing with a little strong sulphuric acid and then several times with distilled water. Two lots of 250 c.c. of the sample are measured into two of the bottles and an equal quantity of pure distilled water (Appendix X) into the third. To each of these, 10 c.c. of dilute sulphuric acid (Ap- pendix X) and 10 c.c. of the standard permanganate solu- tion are added, the latter from a burette, and the bottles set aside in a cool, dark place. At the expiration of fifteen minutes one of the bottle? is opened and a few drops of a solution of potassium iodide added ; this results in the liberation of iodine in proportion to the excess of permanganate left unreduced. The solution is titrated with standard sodium thiosulphate solution till nearly colourless, a few drops of starch solution are then added, and the addition of the thio- 56 WATER ANALYSIS sulphate is continued cautiously till the liquid becomes colourless. Care is required towards the end of the titration, otherwise the thiosulphate will be in excess ; it is added drop by drop, and the bottle shaken after each addition. After the lapse of three hours the second bottle is titrated in the same way, and also the blank test, which serves for both determinations. The difference between the number of c.c's of thiosulphate required for the blank test and that for the sample represents the amount of permanganate, or, in other words, the amount of oxygen required to oxidise the organic matter contained in the water, and the calculation is performed as follows : 10 c.c. of permanganate = '00395 gram KMn0 4 or '001 gram of available oxygen. Suppose 38 c.c. are required for the blank test and 12 c.c. for the sample, then 38-12 x '001 38 OQ -If) y .A or - = '274 part per 100,000. 38 The reactions which take place in the foregoing test may be shown in the following equations, taking oxalic acid as an example of the organic matter. Action of permanganate on organic matter : 5H 2 C 2 4 + 2KMn0 4 -f 3H 2 S0 4 = K 2 S0 4 + 2MnS0 4 + 8H 2 + 10C0 2 . Action of potassium iodide on permanganate : 2KMn0 4 + 10KI + 8H 2 S0 4 = 2MnS0 4 + 6K 2 S0 4 + 8H 2 + 5I 2 . Action of thiosulphate on iodine : I 2 + 2Na 2 S 2 3 = 2NaI + Na 2 S 4 6 . As a guide to the quality of various waters, the following CHEMICAL EXAMINATION 57 figures given by Professor Frankland and Dr. Tidy may be taken, though the conclusions are liable to be modified by a consideration of the other analytical data : Water of great organic purity Water of medium purity Water of doubtful purity Impure water UPLAND SURFACE Absorbing not more than 01 part of oxygen per 100,000 [From 01 to 0'3 I part (From 0-3 to 0'4 1 part | Absorbing more I than 0'4 part OTHER SUPPLIES Absorbing not more than 0'05 part From 0'5 015 part From 015 0-2 part More than part to to 0*2 The Examination of Sewage and Sewage Effluents. The permanganate test must be slightly modified because of the large proportions of organic matter which they contain. The following is a description of the method used by the chemist to the Mersey and Irwell Joint Committee.* Two determinations are made, one at three minutes, the other after four hours, at a temperature of about 60 F. The solutions employed are the same as those for water except the thiosulphate, the strength of which is 4 grams to the litre. For the four-hours test, take 70 c.c. of the sewage effluent in a 5 to 8 oz. stoppered bottle, add 10 c.c. of dilute sulphuric acid and 50 c.c. of the standard permanganate solution. Allow to stand for four hours. If the pink colour should fade considerably, another 50 c.c. of permanganate must be added immediately so as to ensure a large excess of the reagent. At the expiration of four hours, add a few drops of potassium iodide solution and titrate with the standard thiosulphate solution, using starch solution for the final addition. * J. Carter Bell, Jour. Soc. Chem. Indt. y 1898, p. 11. 58 WATER ANALYSIS A blank experiment must be performed each day with 70 c.c. of pure distilled water, 10 c.c. of dilute sulphuric acid, and 50 c.c. of the standard permanganate solution, to determine the strength of the thiosulphate. In the three-minutes test, 70 c.c. of the sewage effluent are taken, 10 c.c. of dilute sulphuric acid added, and the standard permanganate dropped in from a burette with agitation until a faint pink colour appears. As every one knows who has tried this, the three-minute test is far from satisfactory, there being no point at which the pink colour becomes permanent. Even when the purest distilled water is used in the blank tests there is a slight reduction of permanganate, probably due to a trace of organic matter. In the examination of very pure waters this error may be very appreciable, so that in such cases it is better to add a few drops of permanganate, allow to stand for three hours, and then just decolourise with thiosulphate before using, or to titrate the blank test without allowing it to stand. CHLORINE Chlorine is invariably present in natural waters, both in combination with sodium as common salt and in a lesser degree with calcium and magnesium, the sources from which these chlorides are derived being sea water, brine springs, sewage, and the traces of common salt which are to be found in all rocks. Sea water contains a very high proportion of chlorine, i.e. about 2 per cent, or 2000 parts per 100,000, a certain proportion of which finds its way by percolation through porous strata into wells near the coast ; hence the amount of chlorine in such wells is sometimes considerable. Brine springs are more or less saturated with common salt, and wells in the neighbourhood of salt deposits may also contain a large quantity of this elemant. Sea water in the form of spray is carried quite long distances inland by wind, CHEMICAL EXAMINATION 59 and this explains the origin of the traces of common salt always found in rain, and also in upland surface waters. The following figures may be regarded as averages for the amount of chlorine contained in waters from various sources : Parts Cl per 100,000 Rain water . . . . . . 0*2 Spring water 2 '5 Upland surface water . . . . 1*2 Deep well water . . . . . 5*0 River water . . . . . . 1*8 Sewage . . . . . . . ll'O Sea water . . . ... . 2000 The determination of chlorine is performed by taking 50 c.c. of the sample into a porcelain dish, adding two or three drops of potassium chromate solution, and titrating with standard solution of silver nitrate (Appendix X), the solution being continuously stirred. After the addition of a few drops of the silver nitrate solution, the liquid becomes turbid, but retains its pure yellow colour until the titration is completed, the whole of the chlorine being then combined with the silver the slightest excess of the silver nitrate imparts a characteristic buff tint owing to the formation of a trace of silver chromate. If any difficulty is found in determining the end-point of the reaction, a few drops of a solution of common salt should be added to bring back the original yellow colour of the liquid, and the dish placed on one side to serve for comparison with subsequent titrations ; in this way the slightest change of tint is at once rendered apparent. It has also been suggested to observe the course of the titration through a yellow glass screen, a method which may also be recommended. If during the course of the first titration there is an indica- tion that a large quantity of the standard solution is likely to 60 WATER ANALYSIS be used up, it would be preferable to dilute the sample with a definite volume of distilled water or to take a smaller quantity of water and add distilled water to make up the volume to 50 c.c., calculating accordingly. Samples of water containing brine and also sea water should be titrated with a stronger solution of silver nitrate, say a decinormal solution, but even then sea water needs to be diluted. The end reaction appears sharpest when the potassium chromate is present in such a quantity as renders the liquid distinctly yellow, two or three drops of a moderately strong solution being sufficient for the purpose. Sodium chloride may be regarded as a normal constituent in all waters, and unless it is present in large quantities cannot be regarded as in any way injurious. At one time the presence of this substance in more than small quantity was regarded as evidence of sewage contamination, but this view cannot be upheld as there are some supplies of exceptionally pure water containing considerable proportions of the salt. Un- diluted urine contains a large proportion of common salt, i.e. 824 parts per 100,000, according to Frankland, but the amount in ordinary sewage is not very high, i.e. only about 11 parts per 100,000, so that a large amount of sewage might find its way into a supply without materially raising the proportion of this substance. The chlorine is usually ex- pressed as chlorine in chlorides, the calculation to common salt may be made by multiplying by the factor 1*649. HARDNESS Waters may be divided broadly into two classes, hard and soft waters. When used for washing purposes, those waters which feel harsh to the hands are termed hard waters, while those which have a smooth feel are known as soft waters. The hardness of a water is judged by its soap-destroying power : soft waters lather very quickly and freely with soap, but hard waters form a white curdy precipitate and much soap CHEMICAL EXAMINATION 61 is destroyed before a lather is obtained. Then again hard waters lead to scale formation in boilers. The hardness of a water is therefore of very great importance, especially in laundry work, and also in considering its suitability for boiler purposes. Hardness is due to certain mineral salts, principally to calcium carbonate and sulphate, in a lesser degree to mag- nesium carbonate and sulphate, and sometimes to other salts such as calcium chloride, magnesium chloride, calcium nitrate, and salts of iron, usually more than one of these salts being present. The use of soap with waters containing these salts results in the combination of calcium or magnesium with the fatty acids of the soap to form insoluble curdy precipitates. Common salt, when present in large quantities, prevents the lathering of soap, but in this case the hardness, if one may use the term, is due to the fact that ordinary soaps are insoluble in a solu- tion of common salt. Contrary to the view usually expressed, carbonic acid also destroys soap, combining with a portion of the alkali and liberating an equivalent quantity of fatty acid. It is a well-known fact that certain waters lose a considerable proportion of their hardness on boiling, and therefore this hardness is known as temporary hardness ; on the other hand, waters which remain hard even after boiling are said to be permanently hard. Temporary hardness is due principally to calcium and magnesium carbonates, which are held in solution by excess of carbonic acid, but which precipitate as soon as the gas is expelled by heat. CaH 2 (C0 3 ) 2 = CaC0 3 + C0 2 + H 2 0. Whether these are present as bicarbonates or simply as carbonates dissolved in excess of carbonic acid has not been definitely proved, it appears probable, however, that definite bicarbonates of these metals can be formed, though in natural waters there is almost invariably an excess of carbonic acid. 62 WATER ANALYSIS Permanent hardness is due almost entirely to the sulphates of calcium and magnesium, but other salts also have an effect. The estimation of hardness comprises the determination of two factors, total hardness and permanent hardness, the difference between the two figures representing the temporary hardness. Clark's Process. The method most commonly used is that of the late Dr. Clark, hence known as Clark's process : it is a volumetric one in which a standard solution of soap is added to the water with constant shaking till a permanent lather is obtained. It represents exactly the amount of soap de- stroyed by a water, but as applied by Dr. Clark to the estima- tion of the lime and magnesia salts in terms of carbonate of lime it must not be regarded as more than approximately accurate. Total Hardness. For the determination of total hardness, 50 c.c. of the sample of water are measured into a stoppered bottle of about 200 c.c. capacity, the standard soap solution (Appendix X) being added from a burette in quantities of 1 c.c. at a time with intervals of vigorous shaking. This is con- tinued until a lather appears which remains permanent and unbroken for at least five minutes, when the bottle is laid upon its side. This method of procedure must be strictly adhered to in all cases in order to obtain concordant results. A considerable amount of practice is required before this test can be successfully carried out. In some cases what is known as a false lather appears and may remain for a considerable time. Eventually, however, with continued shaking and the addition of a few drops of soap solution this false lather disappears and is not again observed, but finally further additions of soap solution and shaking result in the production of a true lather, which remains per- manent during the time specified for the test. The origin of this false lather is somewhat doubtful, but it is observed more CHEMICAL EXAMINATION 63 particularly in well waters which contain a considerable proportion of magnesia. The true lather may be distinguished by the soft sound which the water gives when shaken against the sides of the bottle, and also by the fact that it is not destroyed but becomes increased by further addition of the soap solution. This difficulty may be overcome to a very large extent by diluting the sample with boiled distilled water previous to the titration. Very hard waters should be diluted till less than 16 c.c. of the soap solution are required for 50 c.c. of the mixture, and water containing much magnesia should be so diluted that not more than 7 c.c. of the soap solution are required. The following table, prepared by Dr. Clark, represents the degrees of hardness in grains of carbonate of lime per gallon, each measure being equivalent to 10 grains of distilled water and the amount of water operated on 1000 grains. CLARK'S TABLE OF HARDNESS Di-irrcc of hardness M. n-ures of soap solution Difference for the next degree of hardness Degree of hardness Measures of soap solution Difference for the next degree of hardness 1-4 1-8 9 19-4 1-9 1 3-2 2-2 10 21-3 1-8 2 5-4 2-2 11 23-1 1*6 3 7-6 2-0 12 24-9 1-8 4 9-6 2-0 13 26-7 1-8 5 11-6 2-0 14 28-5 1-8 6 13-6 2-0 15 30-3 1-8 7 15-6 1-9 16 32-0 1*7 8 17-5 1-9 64 WATER ANALYSIS The soap solution at present in use is of the same strength as that recommended by Dr. Clark, but the weight and measures are converted into the metric system. The table now in use is given in Appendix IX. There are a few points to notice in connection with the latter table. In the first place, the figures commence at 7 c.c. ; this represents the amount of soap solution required to give a lather with 50 c.c. of distilled water, and therefore indicates no hardness. The ratio between the hardness and the number of c.c's of soap solution required also increases with increase in hardness. For this reason the number of c.c's of soap solution required for the diluted sample must first be converted to parts of carbonate of lime per 100,000 and then multiplied by the factor for dilution, and not vice- versa. For instance, suppose that a sample of water dil. 1 in 3 = 5'0 c.c. of soap solution. 5-0 = 6-0 pts. CaC0 3 . 6-0x3 = 18-0 pts. CaC0 3 per 100,000, and not 5-0x3 = 15-0 c.c. = 21-19 parts CaC0 3 per 100,000. Permanent Hardness. For the estimation of permanent hardness 200 c.c. of the water are taken and boiled gently for half an hour in an open flask. To prevent spurting, and at the same time to allow the free escape of steam and carbonic acid, a small funnel is placed in the neck of the flask. At the end of the time specified the flask is quickly cooled by allowing cold water to flow over it ; the volume is then made up again to 200 c.c. by the addition of recently boiled distilled water and the liquid is filtered. After throwing away the first portion, 50 c.c. are measured into the shaking bottle and the permanent hardness determined exactly as for total hardness. Simply raising to the boiling point is not sufficient for removal of the whole of the carbonates, hence the time of boiling should be half an hour in each case. Even then the CHEMICAL EXAMINATION 65 whole of the magnesium carbonate is not precipitated until considerable evaporation has taken place. A false lather rarely appears in the determination of the permanent hardness. The difference between the permanent and total hardness is the temporary hardness. The results obtained for temporary, permanent, and total hardness are expressed in terms of parts carbonate of lime per 100,000 or grains per gallon. 1 English degree of hardness = 1 grain CaC0 3 per gallon, or 1 part in 70,000. 1 French =10 milligrams CaC0 3 per litre, or 1 part in 100,000. 1 German ,, =10 milligrams CaO per litre, ,y* or 1 part CaO in 100,000. Carbonate of lime is slightly soluble in pure water i.e. about 3 parts in 100,000 ; this is not precipitated on boiling, hence it appears as permanent hardness. Judging from this, if the hardness is not more than 3 and is due entirely to salts of lime, there should be no temporary hardness. There are, however, exceptions, and we can there- fore only assume that the temporary hardness is due in these cases to some volatile constituent, probably carbonic acid. There is considerable variation in the amount and nature of the hardness in samples of water according to their source. Upland surface waters rarely have a hardness greater than 5, but deep and shallow well waters are usually very hard, the figures ranging from about 10 to even 50 or more. A figure greater than 20 may be regarded as indicating a very hard water. From a health point of view there is nothing to choose between soft and hard waters. In districts where soft water is used children are said to suffer from rickets owing to poor bone formation ; on the other hand, hard water induces a ten- dency to rheumatic and gouty complaints. A moderately 66 WATER ANALYSIS hard water, say one of 10 degrees of hardness, is probably the best for dietetic purposes. For household purposes, such as washing, and also for boiler purposes, the softer the water the better, as in the first case soap is wasted, and in the second boiler scale is formed, which leads to loss of heat and the attendant danger of overheating and failure of the boiler plates and tubes. The following figures may be regarded as normal for waters from the sources named, though the total hardness and propor- tion of temporary and permanent may vary within wide limits : Temporary Permanent Total Rain water ... 0'3 0'3 Upland surface water . 1*4 3'6 5'0 Spring water . . . 11*0 7'0 18'0 Deep well water . . 12*0 8*0 20*0 Shallow well water . 18'0 22'0 40*0 Hehner's Process. As Clark's process for determination of hardness does not yield an accurate estimate of the amount of lime and magnesia salts present, Hehner has proposed a method which may, for certain purposes, be found more useful. In this process the temporary hardness, or more strictly speaking the carbonates of lime and magnesia, are estimated by titration with a standard solution of sulphuric acid, using methyl orange as indicator, while the permanent hardness is found by evaporating to dryness with standard sodium carbonate solution, and determining the amount of sodium carbonate in excess over that required to convert the sulphates and chlorides into carbonates. For the determination of temporary hardness, to 500 c.c. N of the water are added a few drops of methyl orange and solution of sulphuric acid drop by drop until the colour of the liquid changes to orange. It is important to titrate as near CHEMICAL EXAMINATION 67 to neutrality as possible, therefore it is necessary to observe the slightest change which occurs in the colour of the solution, indicating the end-point of the reaction, and for this reason it is advisable to have at hand a second flask tinted with the same amount of neutral methyl orange for purposes of comparison. For permanent hardness, to 500 c.c. of the water are N added 50 c.c. of sodium carbonate solution, the liquid is evaporated almost to dryness in a nickel or platinum dish, and the residue is extracted several times with distilled water, filtering each time, the combined filtrate being then titrated N with sulphuric acid solution, using methyl orange as before. The number of c.c's of sodium carbonate solution added, minus the number of c.c's of decinormal sulphuric acid required to neutralise the filtrate, represents the amount of sodium carbonate equivalent to the sulphates and chlorides of lime and magnesia. This is calculated in terms of carbonate of lime as in Clark's method : N T 1 c.c. of H 2 4 = '005 gram of CaC0 3 . A If alkaline carbonates are present the alkalinity will be greater than the amount of sodium carbonate added ; in this case there will be no permanent hardness and the excess of alkalinity is calculated as sodium carbonate. The figures obtained by Clark's process and by Hehner's process cannot be compared. Hehner's method gives the true amounts of lime and magnesia salts, whereas Clark's method gives only approximately accurate figures, but apart from this 3 parts of carbonate of lime appear as permanent hardness with the soap test, so that the temporary hardness is lower and the permanent hardness higher at least to that extent. 68 WATER ANALYSIS II. QUANTITATIVE ANALYSIS OF THE MINERAL CONSTITUENTS ALKALINITY The great majority of waters are alkaline to litmus and methyl orange solutions, such alkalinity being due as a rule to the carbonates of lime and magnesia which are held in solution by carbonic acid (in some few cases carbonate of soda is also present). These waters, however, give an acid reaction with phenol-phthalein, which is a more sensitive indicator towards carbonic acid than the others. The estimation of the alkalinity of a water is performed by titration with decinormal hydrochloric acid and methyl orange, as in the determination of temporary hardness by Hehner's method (p. 66). If there is no carbonate of soda present, the alkalinity is the same as the temporary hardness, and should be expressed in terms of carbonate of lime. If however, carbonate of soda is the principal alkaline con- stituent, which rarely occurs, then the alkalinity must be calculated accordingly. Estimation of Caustic Soda in presence of Carbonates. Effluents from paper works may contain caustic soda as well as carbonate. In such cases the total alkali is obtained by titration as above described, and the relative proportions of caustic soda and carbonate of soda by the following method : Phenol-phthalein is first added, giving a pink colour, and a decinormal solution of hydrochloric acid is then run in till the liquid just becomes colour- less ; methyl orange is now added and the titration con- tinued till the colour of the solution changes to a slight orange. The figure obtained with phenol-phthalein in the cold represents the whole of the caustic soda and half the car- CHEMICAL EXAMINATION 69 bonate, while the remainder with methyl orange gives half the carbonate. This may be illustrated by an example as follows : Required when phenol-phthalein is used as indicator . . . 4 .10 c.c. Required when methyl orange is used as indicator . . . . .5 c.c. Total . . . .15 c.c. Amount due to carbonate = 5 + 5 = 10 c.c. Amount due to caustic = 10 5 = 5 c.c, ACIDITY The waters which usually show slight acidity to litmus solution are peaty waters from upland surface supplies. Acidity in these cases is due to organic matter, which may be the so-called peaty acids, crenic and apocrenic, the composition of which is not accurately known, or they may be volatile, as acetic, propionic, &c., and others non- volatile, e.g. lactic, &c. Acid waters are also derived from coal and other mines, while effluents from dye, galvanising, and chemical works are often very acid in their character. In a few rare cases shallow well waters and sewage effluents are acid owing to the presence of free nitric acid produced by nitrifying bacteria. Carbonic acid when accompanied by alkaline bases in the form of bicarbonates does not afiect litmus solution, hence waters which are alkaline to litmus may be acid to phenol-phthalein, but distilled water which contains free carbonic acid is distinctly acid to litmus. Total Acidity. The acidity is determined by measuring out 500 c.c. of the sample into a flask, which it should nearly fill, then adding a few drops of phenol-phthalein solution and titrating with decinormal caustic soda solution till a TO WATER ANALYSIS faint pink colour is produced. This gives the total acidity, including half the carbonic acid. Phenol-phthalein is very sensitive even to weak acids such as carbonic acid, for which reason the titration must be performed as quickly as possible, otherwise atmospheric carbonic acid may vitiate the result. Mineral acids, should they be present, may be estimated by using methyl orange as indicator and titrating till the colour of the solution changes to yellow. The non-volatile acids can be determined by evaporating 500 c.c. of the water to 50 c.c. in a platinum dish and titrating. The difference between this result and the total acidity represents the amount of volatile acids, also including half the carbonic acid. Volatile acids have been detected in certain samples by Fresenius, while there is almost invariably an appreciable loss of organic matter of an acid character when waters are evaporated to dryness with fixed acids. When the acidity or alkalinity to be estimated is very small, centinormal solutions should be employed. The calculation of acidity offers some little difficulty seeing that its nature is not determined, but it may be expressed in terms of sulphuric acid or in the amount of carbonate of soda or lime required for neutralisation. BASIC RADICLES Iron. If iron is present only in very small quantity, it may be determined volumetrically by the method given on p. 89. If in large quantity, then the gravimetric method must be resorted to, the determination being made in the filtrate from the silica. As, however, alumina and aluminium phosphate may also be present, these will have to be separated from the precipitate, and when a full analysis is required it will be necessary to determine the amount of each of these CHEMICAL EXAMINATION 71 constituents. If manganese is also present, a proportion of this metal is precipitated with the iron, and this necessitates a further separation. The filtrate and washings from the silica are mixed, ammonia is added in slight excess, and the liquid boiled gently till it no longer smells of ammonia ; the precipitate is then collected upon a filter paper and thoroughly washed with hot water. In order to simplify matters, it is well to previously evaporate half a litre of the water and test for phosphates by boiling with ammonium nitro-molybdate. If they are found to be absent, the portion of the separation referring to phosphates may then be eliminated. To separate manganese, the precipitate is dissolved from the filter with the least possible quantity of hydrochloric acid and washed into a beaker, neutralised exactly with ammonia followed by ammonium carbonate, excess of ammonium acetate then added, and the solution boiled. The iron and aluminium are precipitated as basic acetates, while the manganese remains in solution. The precipitate is collected upon a filter paper, washed, dried, ignited, and weighed. To separate the iron from alumina and aluminium phos- phate, the precipitate is dissolved in hydrochloric acid and the liquid diluted. To the solution about a gram of cream of tartar is added, followed by ammonia in excess and fresh ammonium sulphide. After standing a few hours the ferrous sulphide is filtered off, washed, dissolved in nitric acid, and the iron precipitated with ammonia as before. The ignited precipitate consists of pure Fe 2 3 . Factor for calculating Fe 2 3 to 2Fe = 0-70. Aluminium. In the absence of phosphoric acid, any difference between this weight and the original one is due to alumina, and may be calculated as such. If phosphoric acid is present, it is estimated as described 72 WATER ANALYSIS on p. 79, and the sum of this and the oxide of iron deducted from the weight of the original precipitate obtained with ammonia gives the alumina. Factor for calculating A1 2 3 to A1 2 = '5303. The iron and alumina are usually present in sufficient quantity to combine with the whole of the phosphoric acid, otherwise calcium phosphate would be at the same time precipitated. It is well, therefore, to test the solution containing the alumina for lime before disposing of it. Manganese. For the determination of manganese, the filtrate obtained after boiling with ammonium acetate and the washings are added to the main filtrate and the whole evaporated to a convenient bulk. Bromine is added, and the liquid kept gently heated until it appears faintly yellow, then ammonia added in slight excess and the liquid boiled. If the manganese precipitates perfectly and the liquid becomes quite clear the oxidation is complete, but should this not be the case more bromine should be added, and the operation repeated until the liquid does appear quite clear and colour- less. The precipitate is then filtered off, washed, . dried, ignited, and weighed as Mn 3 4 . Factor for calculating Mn g 4 to 3Mn = -7203. Calcium. The filtrate and washings from the manganese are mixed together and heated to boiling point. Ammonium oxalate is added as long as a precipitate occurs, and the beaker is set aside in a warm place for several hours. The calcium oxalate is then filtered off, washed, dried, ignited before the blowpipe, and weighed, the heating being repeated till the weight is constant. According to Dittmar, the lime thus separated contains 9 per cent, of impurities, consisting principally of magnesia and soda. To separate these, water is slowly added, then 5 c.c. of hydrochloric acid ; the liquid is then washed into a beaker, ammonia added drop by drop CHEMICAL EXAMINATION 73 in slight excess, and the liquid again boiled. Any precipitate which may be formed is filtered off, and the filtrate again precipitated with ammonium oxalate as above. Factor for calculating CaO to Ca = -7147. Magnesium. The filtrate and washing from tbe lime are evaporated to dryness in a platinum dish and gently ignited to get rid of ammonium salts, hydrochloric acid is then added, and the solution filtered if necessary. To the solution ammonia is added in moderate excess, followed by sodium phosphate. The beaker is set aside in the cold for twelve hours, as the precipitate of ammonium magnesium phos- phate requires some little time to separate entirely. The precipitate is collected upon a filter paper and washed with weak ammonia, as it is soluble in water. After drying, the bulk of the precipitate is transferred to a watch-glass, the remainder being dissolved from the filter paper with acetic acid containing a little nitric acid, and the solution collected in a platinum dish. After evaporating to dryness, the bulk of the precipitate is added, and the heating com- menced with a very small flame for about half an hour, the dish being meanwhile covered with a watch-glass to prevent spurting. The heat is then raised to a full red for about fifteen minutes, and the dish cooled and weighed. The ignited precipitate is magnesium pyrophosphate, Mg 2 P 2 7 . Factor for calculating Mg 2 P 2 7 to 2Mg = -2184. Alkali Metals : Potassium and Sodium. The alkali metals may be estimated together as chlorides and calculated to mixed metals without subsequently separating them. This will serve where great accuracy is not required, but at best it is only an empirical method, the assumption being that the alkalies are present in equal proportions, which is rarely, if ever, the case. For the estimation of the alkalies, one litre of the water is evaporated to a small bulk, hydrochloric acid is added in 74 WATER ANALYSIS excess, and the evaporation continued to dryness. The residue is moistened with concentrated hydrochloric acid, then with water, and the solution filtered to remove the silica. The filtrate and washings are mixed together and heated, and slight excess of barium chloride added ; after standing several hours the barium sulphate is filtered off, the filtrate and washings again mixed, evaporated to a small bulk, and milk of lime (pure, free from alkalies) added. The liquid is heated and filtered, and the precipitate washed until free from soluble salts. The filtrate and washings are again mixed and heated, ammonia is added, then ammonium carbonate, and ammonium oxalate to precipitate the lime and baryta, the solution being again filtered and the pre- cipitate washed. The filtrate and washings are evaporated to dryness in a platinum dish, and ignited gently till fumes cease to be given off ; a little water is added to dissolve the salts, followed by a few drops of each of the above reagents to ensure the removal of the last traces of the alkali metals ; after again filtering, the filtrate and washings are evaporated to dryness in a platinum dish, a few drops of dilute hydrochloric acid are added, and the dish is gradually heated to redness. During the first part of the heating the dish should be covered with a clock-glass to prevent loss of salts by decrepitation. The residue consists principally of sodium chloride, but contains a small amount of potassium. If no separation is made it is best to calculate to sodium chloride. In the mixed chlorides thus obtained the potassium can be directly estimated by the chloroplatinate method, or the proportions of the two metals may be indirectly calculated from the quantity of chlorine present. If the alkalies are to be separately estimated, the mixed chlorides are dissolved in a very small quantity of water, and excess of a solution of platinic chloride is added, to convert the chlorides into chloroplatinates ; the solution is evapo- CHEMICAL EXAMINATION 75 rated almost to dryness, 30 c.c. of absolute alcohol are then added, and, after standing about half an hour, 15 c.c. of absolute ether. The liquids are carefully mixed and the dish set aside under cover of a bell jar until the precipitate has entirely separated, the clear fluid being then decanted through a small filter paper, and the precipitate washed with a mixture of alcohol and ether in the above proportions until free from platinic chloride. Any small particles of the precipitate which may have passed on to the filter paper are washed back into the dish with a little hot water, the solution is then evaporated to dryness, and the residue heated at 130 C. till constant in weight. Factor for calculating K 2 PtCl 6 to K 2 = -1608. This weight may be verified by igniting the precipitate, washing out the potassium chloride with hot water, drying, and again igniting the metallic platinum left. Factor for calculating Pt to K = '4006. The proportion of the two alkalies may also be calculated as above indicated by determining the chlorine in the mixed chlorides, then multiplying its weight by 2'103, deducting from the product the weight of the mixed chlorides, and multiplying the figure thus obtained by 3 '6288, the result being the weight of the sodium chloride. Deducting this from the weight of the mixed chloride, the amount of potassium chloride is obtained. The two chlorides may then be calculated to metals by means of the following factors: KC1 to K = -5244. NaCl to Na = -3934. Usually the quantity of sodium is very much greater than that of potassium. Alkalies present as Carbonates. If alkaline carbonates are present in the water, no sulphates or chlorides of lime and magnesia will be present, the latter metals, if 76 WATER ANALYSIS present, being in the form of bicarbonates. In this case the alkalies present as carbonates may be estimated by evaporating 500 c.c. of the water to dryness, washing the residue with hot water until the washings are neutral, filtering, N and estimating the alkalinity of the nitrate with hydro- chloric acid, using methyl orange as indicator. 1 c.c. HC1 = -0053 gram Na 2 C0 3 . Ammonia. This is estimated as described on p. 10. ACID RADICLES Silica (Si0 4 ). One litre of the water is made acid with hydrochloric acid, and evaporated to complete dryness in a platinum dish. The residue is moistened with strong hydrochloric acid and heated on a water-bath for a few minutes, water is then added, and the liquid filtered. The silica is well washed with boiling water until free from acid, then dried, ignited, and weighed. Sulphuric Acid (S0 4 ). This may be estimated in the filtrate from the silica. For this purpose the filtrate and washings are mixed together and heated to boiling. Barium chloride is then added in slight excess, and the liquid set aside for several hours. The liquid is filtered and the barium sulphate collected upon the filter, treated with a few drops of dilute hydrochloric acid, and washed with hot water until free from chlorides. It is then dried, ignited, and weighed. Factor for converting BaS0 4 to S0 4 = -5884. Sulphuretted Hydrogen (H 2 S). This is rarely present ex- cept in medicinal springs and sewage ; it may be present as free sulphuretted hydrogen or, if the water is alkaline, as sulphides. The latter are unstable and give off free CHEMICAL EXAMINATION 77 sulphuretted hydrogen. Sulphuretted hydrogen is quickly lost in this way, and in contact with air it is destroyed by oxidation with liberation of free sulphur. H 2 S + = H 2 + S. The finely divided sulphur remains suspended in the water indefinitely, giving it a peculiar greyish- white milky appear- ance. For these reasons it is necessary to take the sample in a bottle, which is filled perfectly with the water before fixing in the stopper in order that no air may be enclosed with the water, and the sample should be examined immediately after its collection. The estimation of the sulphuretted hydrogen, both free and combined, is performed by taking 500 c.c. of the water, slightly acidifying with dilute sulphuric N acid, and titrating with solution of iodine, using starch J.UO paste as indicator. N Each c.c. of iodine sol. = '001 7 gram H 2 S (sulphuretted hydrogen). Alkaline sulphides may be detected by observing the reaction of the water, and also testing with sodium nitro- prusside, there being no necessity to proceed further. Carbonic Acid. Combined (C0 3 ) and Free (C0 2 ). Car- bonic acid may be present in water either as free carbonic acid, half -combined, in the form of bicarbonates, and combined, as in normal carbonates. Free Carbonic Acid. The amount of the free carbonic acid can be estimated by taking 500 c.c. of the water and titrating with a centinormal solution of sodium carbonate, using phenol-phthalein as indicator, as recommended by Archbutt. Bicarbonates being neutral to this indicator, a 78 WATER ANALYSIS pink colour appears as soon as the whole of the bases are converted into bicarbonates. Na 2 C0 3 + C0 2 + H 2 = 2NaHC0 3 . If there is no free carbonic acid present, one or two drops of the soda solution will be sufficient to produce a pink colour. 1 c.c. of A Na 2 C0 3 sol. = -00022 gram of C0 2 . The results are vitiated if other acids be present. In this case one of the following methods must be resorted to. The free and half-combined carbonic acid are also separated and estimated in the gaseous form (p. 100). Free carbonic acid can also be estimated by determining the total acidity in one portion of the sample, then aspirating air (free from carbonic acid) for some time through anothei portion, and determining the residual acidity, the loss being due to the free carbonic acid which is expelled. Free carbonic acid and that existing as bicarbonate are estimated together by means of a solution of barium hydrate, and as the results are vitiated in contact with air the determination is best performed in a stoppered bottle of a capacity of about 550 c.c. The barium hydrate solution need not be absolutely correct, but the oxalic acid solution must be of exact strength and the relationship of the two must be known. 500 c.c. of the water are measured into the bottle, 3 c.c. of a nearly saturated solution of barium chloride and 2 c.c. of a saturated solution of ammonium chloride are added, followed by 45 c.c. of the barium hydrate solution from a burette. The bottle is then closed and shaken from time to time. After about half an hour the precipitate is allowed to subside, 50 c.c. of the clear solution pipetted off, and titrated immediately with the oxalic acid CHEMICAL EXAMINATION 79 solution. The result multipled by eleven will give the excess of baryta in terms of oxalic acid for the whole sample. 10 c.c. of the original barium hydrate solution should then be titrated to determine its strength and the amount calculated for 45 c.c. The difference between the two figures represents the oxalic acid solution equal to the carbonic acid present in the sample. 1 c.c. standard oxalic acid solution = -0022 gram C0 2 , or I'll c.c. Carbonic acid is present in sufficient quantity in ordinary distilled water to show a distinctly acid reaction with litmus solution ; it is also abundant in deep well waters, and certain medicinal waters are aerated by it, but in upland surface waters it may be absent, or present only in small quantity, the acidity in these cases being usually due to organic acids (peaty acids). Combined Carbonic Acid. This is estimated with decinormal solution of hydrochloric acid, using methyl orange as indi- cator, as described under " Temporary Hardness," p. 66. 1 c.c. of HC1 = -0022 gram of C0 2 . Phosphoric Acid (P0 4 ). The dried residue from one litre of the water is moistened with strong nitric acid, evaporated to dryness, again moistened with nitric acid, water added, and the liquid filtered. The residue on the filter paper is washed several times with boiling water, and the washings added to the filtrate and evaporated to a small bulk ; excess of a solution of nitro-molybdate of ammonia is added, and the liquid then left gently heated on a sand-bath for several hours. If phosphoric acid is present, a yellow precipitate of ammonium phcsphomolybdate will be formed, which should be filtered off, washed with water containing ammonium nitrate till free from soluble salts, then dissolved off the 80 WATER ANALYSIS filter paper by means of ammonia. " Magnesia mixture " added to this solution precipitates phosphoric acid as ammonium magnesium phosphate. It is weighed as mag- nesium pyrophosphate, as described under "Magnesia." Factor for converting Mg 2 P 2 7 to P0 4 = '5661. This method is suitable only for large quantities of phos- phoric acid. When traces of phosphoric acid only are present this should be stated. Chlorine (Cl). This is estimated as described on p. 58. Nitric Acid (N0 3 ). For estimation, one of the methods given on p. 38 et seq. may be employed. Nitrous Acid (N0 2 ). This is determined by the method given on p. 50. Calculation of the Results of the Mineral Analysis The question of combining the acids and bases is a difficult problem, and it is probable that no two analysts would agree upon the same method of expressing the results. As a matter of fact the acids and bases are not combined in a dilute solution such as water, but are present as free ions, and it is only on evaporation that combination takes place. In all cases the figures of the analysis should be first expressed as they are estimated that is, in the form of metals and acid radicles. It is preferable to calculate the bases as metals rather than as oxides because they are partly combined as chlorides, which, of course, do not contain any oxygen ; if they should be calculated as oxides, an amount of oxygen equivalent to the chlorine has to be deducted, and this leads to unnecessary complication. The calculation is usually made on the assumption that the acids and bases are combined in the order of their affinities, which is probably the best method that could be devised. Therefore the strongest base is united with the strongest CHEMICAL EXAMINATION 81 acid, and anything left over is united with the next strongest acid, and so on. This requires a number of calculations, but when the results are completed they no doubt convey to the ordinary individual a clearer idea of the mineral constituents than would be the case if they were expressed only in the uncombined state. The method of combination adopted by Fresenius is shown in the very complicated analysis of the water of the Elisabethenquelle at Homburg. The sulphuric acid is com- bined first with barium, then with strontium, and finally with calcium. The bromine and iodine are combined with mag- nesium. The chlorine is combined with calcium, then with potassium, lithium, ammonium, sodium, and finally with magnesium. The phosphoric acid is combined with calcium. The precipitate obtained on boiling contains lime, magnesia, iron, and manganese, which are calculated to carbonates, and the excess of carbonic acid is expressed as free carbonic acid (C0 2 ). The silica is stated as such (Si0 2 ). For brewing waters Moritz and Morris give the following method of calculation : The chlorine is first combined with sodium ; if there is any excess it is combined with calcium ; if still in excess it is combined with magnesium, and any left over is combined with the potassium which may be in excess of that required to combine with the sulphuric acid. If sodium is in excess, it is combined with any sulphuric acid above that required to combine with the potassium, and if still in excess it is combined with nitric acid. If any calcium is left after combining with chlorine, or if there is no chlorine left over to combine with it, it is combined with nitric acid ; should there be any excess, this is combined with sulphuric acid, and if still in excess with carbonic acid. If magnesium should be in excess after combining with chlorine, or if there is no chlorine left to combine with it, it is combined with nitric acid, any excess with sulphuric acid, and, should F 82 WATER ANALYSIS there be still an excess, with carbonic acid. The sulphuric acid is combined first with potassium, any excess with sodium, then with calcium, and finally with magnesium. The nitric acid is combined first with sodium, then with calcium, magnesium, and finally potassium. Any sodium, potassium, calcium, or magnesium left uncombined are calculated as carbonates. The iron is calculated as ferric oxide (Fe. 2 3 ), aluminium as alumina (A1 9 3 ), and the silica as free Si0 2 . The two methods may be tabulated as follows for com- parison : Fresenius SO. I Br Cl ro CO, Free CO, SKX Ca Ca Mg Fe Mn C0 2 Si0 2 Moritz and Morris rNa Ca Mg K Cl so, NO, C0 3 Fe . Al . Si0 K Na Ca Mg Na Ca Mg K Ca Mg Na K Fe 2 3 AJ 2 3 Si0 CHEMICAL EXAMINATION 83 HI. DELETERIOUS METALS In the examination of waters for drinking purposes it is often necessary to test for poisonous or deleterious metals, and owing to the almost universal employment of lead pipes for its conveyance, this metal is the one which is most likely to be present. It may be dissolved from the service pipes, but a fruitful source of contamination is the use of lead cisterns holding a considerable volume of water, so that there is only an intermittent source of supply from the mains. The greatest amount of lead is found early in the morning when the water has stood in the pipes all night, and for this reason a considerable quantity of water should be run off before any is collected for household use. Copper is sometimes, though rarely, present in drinking waters ; it may be found when copper pipes are employed, and it is very likely to be present if tinned copper pipes are in use. The coating of tin being very seldom perfect, the copper dissolves by reason of the electrical action which is set up between these two metals. Arsenic may possibly be found in effluents from manu- facturing districts and in mine waters, but it is not likely to occur in ordinary drinking water. Zinc is occasionally found in drinking water, and when this is the case it is usually derived either by storage in a gal- vanised tank or by passage through galvanised iron pipes. Deep well waters containing nitrates are especially liable to act upon zinc, the nitrates becoming reduced to ammonia and the zinc dissolved as bicarbonate. It usually separates on the surface of the water as a film of zinc carbonate soon after the sample has been collected. Iron may be present in water either in the ferrous or ferric condition, derived from the rocks through which the water percolates. Mine waters often contain a considerable 84 WATER ANALYSIS proportion of iron in solution as ferrous sulphate. This is pro- duced by the oxidation of pyrites and is accompanied by free sulphuric acid, so that such waters are more or less acid. They deposit a considerable quantity of iron as a basic ferric hydrate by contact with air, and then become opaque and dark red or yellow in colour. Many medicinal springs contain iron in solution as bicarbonate (chalybeate waters), and also precipitate iron in the form of ochre as they come in contact with air. Upland surface waters usually contain small quan- tities of iron and manganese in combination with organic acids, and it is to these salts that the yellow or brown colour of such waters is due ; in this case the iron is in the ferric condition. LEAD The amount of lead found in solution is never very large, being usually less than 1 -0 grain per gallon ; therefore sul- phuretted hydrogen does not produce a precipitate of sulphide of lead, but merely a brown or black colouration, the intensity of which increases in direct proportion to the amount of the metal present, the liquid remaining clear for quite a long time. This being the case, it is possible, by using a solution of acetate of lead of known strength, to match the tint thus obtained, and to estimate with a fair amount of accuracy the quantity of lead present. This colorimetric process for estimating lead was devised by the late Professor W. A. Miller. If lead has been proved by a qualitative examination to be present, 100 c.c. of the water is taken in a Nessler cylinder and acidified with two drops of dilute hydrochloric acid, sulphuretted hydrogen is then passed in from a generator until the water smells strongly of the gas, and the cylinder placed on a white tile. The colour generated is judged by raising the cylinder a few inches above the tile and looking down through the column of liquid. 100 c.c. of distilled water are CHEMICAL EXAMINATION 85 now measured out, two drops of dilute hydrochloric acid are added, and then standard lead acetate solution in such quan- tity as may be deemed sufficient to yield a similar colour ; sulphuretted hydrogen is passed in as before, and the two cylinders are placed side by side and compared. If the colours are not quite the same, other comparative tests are made with less or more of the lead acetate solution until one is obtained exhibiting the same intensity of colour as the sample. The amount of lead acetate used in the final test represents the quantity of lead present. 1 c.c. of the standard lead acetate solution = -0001 gram of lead ; therefore each 1 c.c. of this solution required for 100 c.c. of the sample represents O'l part of lead per 100,000 parts of the water. Action of Water on Lead. In the examination of a water for a proposed new sjpply it may be necessary to determine its action upon lead. For this purpose 500 c.c. of the sample are measured into a tall cylinder and a strip of clean, but not bright, sheet lead 6 in. long and 2 in. wide is immersed in it. The cylinder is covered with a ground glass plate and set aside for a period of one or two days, or longer if it is considered necessary ; at the end of this time 100 c.c. of the water are measured out, and the amount of lead which it has dissolved is estimated by the method previously described. In the determination of lead by this method it is necessary that the same amount of acid should be used in all cases, as the proportion present appreciably affects the resulting colour ; it is sufficient if the water is rendered faintly acid. Some waters have a peculiar action upon the lead, causing it to scale ofl in minute flakes which do not dissolve ; these flakes considerably interfere with the estimation of the lead in solution, therefore it is necessary in such cases to filter the water before examination ; it may also be found advisable to estimate the amount of lead in suspension as well as in 86 WATER ANALYSIS solution, so as to obtain a true estimate of the action of the water on the metal. The total amount of lead thus removed would be estimated by ordinary gravimetric methods, the colorimetric process serving only for determining .the lead in solution. If the amount of lead in solution is more than 1 grain per gallon, it is somewhat difficult to match the tint exactly, and so it is preferable to dilute the sample with a known volume of distilled water and calculate accordingly. The action upon lead is most marked in the case of waters from upland surface supplies. These are peaty, acid in character, and contain but little mineral matter in solution. In the discussion on a paper by Frankland and Frew,* Allen stated that the acid in the Sheffield supply was clearly a fixed organic acid, as it was not removed by concentration ; also when the previously neutralised water was evaporated to dryness and the residue ignited it was found to be alkaline. Allen also mentions the fact that sulphate of lead is not nearly so insoluble as one would expect, the amount dissolved in pure water being equal to 3 grains ( = 2 grains of lead) per gallon. He also points out that if the acid had the same molecular weight as lactic acid (i.e. 90) it would dissolve more than its own weight of lead. TTie acid in question acts upon phenol- phthalein, but not on methyl orange ; therefore the quantity present can be determined in terms of caustic soda neutralised, if the former indicator is employed. Waters highly charged with carbonic acid, such as aerated waters, dissolve lead freely. Distilled water, rain water, and water from melted ice and snow also act upon lead vigorously. (Distilled water dissolves 0*25 part lead per 100,000 in two days.) The action in these cases is most probably due to the * Action of Water on Lead. P. F. Frankland and W. Frew. Jour. Soc. Chem, Indt., 1889, p. 247, CHEMICAL EXAMINATION 87 presence of carbonic acid and oxygen and the absence of mineral matters which have a retarding influence. Hard waters, such as deep well waters and spring water, have little or no action upon lead, the sulphates and carbonates being supposed to form a protective coating of insoluble lead salts on the surface of the metal. Ammonium nitrate, however, increases the action considerably. In their report on the action of water on lead made to the Water Committee of the Huddersfield Corporation in 1886, Messrs. Crookes, Odling, and Tidy * state that those waters taken from the service pipes which contained a notable quantity of lead gave on an average O21 grain of silica per gallon, those in which no lead was found gave 0-53 grain, while in those in which the action was intermediate the silica was equal to O39 grain per gallon, and they found that the activity of these waters towards lead was greatly reduced by passage through a filter composed of flint, carbonate of lime, and sand. That the action upon lead is reduced by such filtration was also proved by P. F. Frankland, though no material increase in the amount of silica could be detected. It is also of interest to note that Frankland found some waters containing as much as 0-5 grain of silica per gallon very active towards lead. The activity of these waters was, however, materially reduced by addition of sodium carbonate or phosphate. COPPER The most characteristic test for copper is the production of the red ferrocyanide, and if this metal has been proved to be present it can be estimated by a similar colorimetric method to that used for lead, replacing the solution of lead acetate with a standard solution of copper sulphate. * Action of Water on Lead. P. F. Frankland. Jour. Soc. Chem Indt.. 1889, p. 241. 88 WATER ANALYSIS 1 c.c. of standard copper sulphate solution = -0001 gram of Cu. The copper can also be estimated colorimetrically as ferro- cyanide, by acidifying with, acetic acid and adding a few drops of a solution of potassium ferrocyanide, matching the tint with the standard copper sulphate solution. This method is useful in presence of lead, as the accuracy of the test is not appreciably affected by the presence of this metal ; but iron interferes considerably with it, the blue colour produced entirely masking the red colour of the copper ferrocyanide. In such a case the iron is separated by evapo- rating to a small bulk, oxidising with nitric acid, precipitating the iron with ammonia, acidifying the nitrate with acetic acid, and making up to the original volume. The water can then be tested with ferrocyanide in the usual manner. Copper sulphate has been tried with success on several public water supplies in America for killing algae, bacteria, &c., which sometimes accumulate in large masses in reservoirs and on filter-beds, it being stated that the copper is entirely removed from the water by these organisms. If such method of treatment should come into regular use it would be neces- sary to examine samples from public water supplies more carefully for this metal, as it is very doubtful if the whole of the copper is removed from the water ; there is more probably a balance between the number of living organisms and the amount of copper in solution, and the decay of the dead organisms would leave the copper in a fit state to be re- dissolved. ARSENIC The estimation of this metal is performed by evaporating 500 c.c. of the sample after addition of a few drops of caustic soda solution. The residue is treated with hydrochloric acid and the solution transferred to a small Marsh's arsenic CHEMICAL EXAMINATION 89 apparatus containing zinc. The hydrogen evolved is passed through a U tube filled with granulated pumice-stone moistened with a solution of lead acetate to remove sul- phuretted hydrogen, then through a piece of combustion tubing drawn out to a long jet at one end. Previous to adding the solution, hydrogen is evolved for a few minutes to clear the apparatus of air, the gas lighted at the open end of the jet, and, after addition of the solution, a small Bunsen flame is applied to the tube at the point where it is drawn out. The heat decomposes the arseniuretted hydrogen, yielding a mirror of arsenic on the cool part of the tube. The mirror obtained in this way is compared with others obtained with known quantities of arsenic in order to estimate the quantity of arsenic present. The apparatus and chemicals should previously be proved to be free from arsenic by evolving a considerable quantity of hydrogen from the reagents and testing the gas as above described. ZINC Zinc is usually present in water as bicarbonate and separates out as carbonate, either as a scum on the surface or in the form of crystals. If this metal should be found by qualitative tests to be present, the amount may be determined by separating the iron by addition of ammonia, also the manganese by bromine and ammonia, then precipitating the zinc as sulphide and converting it into oxide by ignition. IRON Iron as a Ferrous Salt. About 1 litre of the water is taken, two drops of dilute hydrochloric acid added, then one drop of a freshly prepared saturated solution of potassium ferricyanide, and the liquid shaken ; it is then allowed to 90 WATER ANALYSIS stand for two hours and examined in the tintometer in a trough of convenient length, the tint being compared with the standard glasses. Similar tests are made with distilled water containing known quantities of the standard ferrous solution until a similar strength is obtained. By making notes of the combination of glasses equivalent to various quantities of iron it is possible to construct a table for future use. Waters are usually more or less coloured, hence it is necessary to examine the water itself in the tintometer and make any correction which may be found necessary. Iron as a Ferric Salt. This is determined by taking 50 c.c. of the water in a Nessler cylinder, adding 2 c.c. of dilute hydro- chloric acid and 2 c.c. of ammonium sulphocyanide solution, and matching the colour produced by the addition of standard ferric solution to distilled water to which the same quantities of reagents have been added. Total Iron. If the colour of the water interferes with the determination of iron, 250 c.c. should be evaporated to dryness in a platinum dish, gently ignited, the residue dissolved in 2 c.c. of dilute hydrochloric acid, and the estimation then proceeded with as above described. As hydrochloric acid frequently contains traces of iron, it is necessary to examine it for this metal before use, otherwise serious errors may be introduced. CHEMICAL EXAMINATION 91 IV. GASES CONTAINED IN SOLUTION The gases contained normally dissolved in water are those of the atmosphere, oxygen and nitrogen, and also carbonic acid, the total amount of atmospheric gases (oxygen and nitrogen) dissolved by one litre of pure water being 17'95 c.c. In this solution the relationship of oxygen to nitrogen is not the same as in atmospheric air, the oxygen being in excess. Thus on saturating water with air and subsequently liberating the gases and analysing them it was found that the proportions were : Oxygen . , . . 34-91 Nitrogen - . . . . . 65-09 100-00 the ratio between the oxygen and nitrogen being roughly 1:2, this result agreeing very closely with the proportions calculated by Dalton's law of partial pressures. In air the proportions are : Oxygen 20-96 Nitrogen . . . . . . 79-04 100-00 the ratio of the two gases being approximately 1 : 4. The quantities of oxygen and nitrogen dissolved by one litre of pure water are : Oxygen , . . 6-26 c.c. Nitrogen 11-69 c.c. 17-95 c.c. The proportions are, however, not the same in natural supplies, due no doubt, to several factors variations in pressure, quantity and nature of dissolved solids, &c. 92 WATER ANALYSIS In contact with, oxidisable organic matter the oxygen rapidly disappears, and there is a corresponding rise in the proportion of carbonic acid, the nitrogen, however, remaining stationary. This is clearly shown in the analyses by Miller of Thames water taken at different points above and below London : Kings- ton Hammer- smith Somerset House Green- wich Wool- wich Erith c.c. c.c. C.C. C.C. c.c. c.c. Total volume of gas per litre . ' . 52-7 62-9 71-25 63-05 74-3 Carbonic acid .' * 30-2 45-2 55-6 48-3 57-0 Oxygen . . " 7.4 4-1 1-5 0-25 0-25 1-8 Nitrogen "* 15-0 15-1 16-2 15-4 14-5 15-5 Ratio of oxygen to nitro- gen * 1 :2 1 :3-7 1 : 10-5 1:60 1:52 1:8 The proportion of oxygen, nitrogen, and carbonic acid vary very considerably in waters from different sources, as shown in the following analyses : Oxygen Nitrogen Carbonic acid Observer c.c. per litre Rain water . 6-37 13-08 1-28 Frankland Upland surface water (Cumber- land) * 7-26 14-24 2-81 Upland surface water (Loch Katrine) i 7-04 17-31 1-13 Upland surface water (Vyrnwy) 5-45 11-53 Campbell Brown River water (Thames) . 5-88 13-25 40-21 Frankland Deep well water in chalk 0-28 19-44 55-20 The deep well waters contain scarcely any oxygen and a large proportion of carbonic acid, showing that though the CHEMICAL EXAMINATION 93 water is now pure it contained at one time a large quantity of organic matter. The estimation of oxygen is more particularly useful in dealing with stream or river waters or effluents from sewage farms to determine the amount of aeration. The estimation of the gases dissolved in water may be made by ordinary volumetric means, with the exception of the nitrogen (p. 77), or the whole of the gases can be expelled by boiling and estimated by gasometric methods (p. 100). OXYGEN Thresh 's Method. This process is based on the fact that when nitrous acid is brought into contact with an iodide, iodine is liberated. If this reaction takes place out of con- tact with oxygen, the quantity of iodine liberated is directly proportional to the amount of nitrous acid present. 2HI + 2HN0 2 = I 2 + 2H 2 + N 2 2 . If, however, oxygen is present, then the nitric oxide acts as a carrier of oxygen, becoming alternately oxidised and reduced as long as any free oxygen is present. The amount of iodine then liberated is in proportion to the nitrous acid added, plus the amount of oxygen present. The reaction takes place in two stages : N 2 2 + 2 = N 2 4 . N 2 4 + 4HI = 2I 2 + N 2 2 + 2H 2 0. From these equations it will be seen that 1 atom or 16 parts of oxygen by weight is capable of liberating 2 atoms or 254 parts by weight of iodine, and as the estimation of iodine can be easily and accurately performed the process is one of extreme delicacy. The apparatus required is shown at Fig. 7, and consists of 94 WATER ANALYSIS a wide-mouthed bottle of about 500 c.c. capacity provided with a cork perforated with four holes. Through one of these is passed a jet connected by a short piece of rubber tubing to the burette containing the thiosulphate solution. To the second is fitted a stoppered separating funnel holding about FIG. 7. Apparatus for estimation of oxygen in water. Thresh's method. 250 c.c., the capacity of which is accurately known. The cork is also fitted with a tube connected to the gas supply, and an exit tube to which is connected a piece of rubber tubing with a glass jet and a cork to be fitted to the tubulure of the stoppered funnel when the liquid is to be delivered to the bottle. Before commencing a determination the bottle is cleaned CHEMICAL EXAMINATION 95 and dried. The burette is filled with the thiosulphate, taking care that the rubber tube and also the jet is filled with the liquid, and the bung is then fixed in the bottle. The separator is now filled entirely with the water to be examined, and to it is added 1 c.c. of the potassium iodide-sodium nitrite solution (Appendix X), followed by 1 c.c. of dilute sulphuric acid, delivered by means of a pipette with a long jet. As these reagents are heavier than water they pass directly to the bottom of the separator and an equivalent quantity of the water escapes. The stopper is now pub in carefully so that no air is introduced at the same time. The separator is now inverted several times so as to mi* the reagents thoroughly with the water, the separator being then placed in position in the rubber cork and the whole allowed to remain undisturbed for fifteen minutes to ensure the com- pletion of the reaction. Coal gas is now passed in a rapid stream through the bottle, and, after a few seconds, to allow most of the air to escape, it is lighted at the jet. After passing fifteen minutes every trace of air will have been expelled from the bottle, the gas is turned off for a second so that the flame dies out, the stopper of the separator is removed and the jet fixed in place of it, and the gas turned on again ; the water is then run into the bottle. Immediately afterwards the jet is removed and the gas again ignited. The iodine liberated is now titrated with the standard thiosulphate solution until the yellow colour almost disappears, following which some starch solution is run into the separator and 1 c.c. dropped into the bottle, the titration being continued till the liquid becomes colourless. After standing for a few minutes the liquid again acquires a faint blue colour, which is due to the oxygen contained in the thiosulphate used ; this may require '05 to '1 c.c. more of the volumetric solution to again render the liquid colourless. The thiosulphate required represents the amount of iodine liberated 96 WATEE ANALYSIS by (1) the nitrous acid, (2) the oxygen dissolved in the water, (3) the oxygen dissolved in the reagents added, (4) the oxygen dissolved in the thiosulphate. (1) and (3) may be estimated immediately after the comple- tion of the determination as above, by running in 5 c.c. each of the solutions of potassium iodide, starch paste, and sulphuric acid, taking every precaution to exclude air from entering the bottle. The iodine liberated is then titrated with thiosul- phate solution, and the number of c.c. divided by 5 equals the correction to be applied. (4) is only a small fraction, but it is difficult to determine. It is therefore assumed that the thiosulphate solution behaves in the same way as distilled water to oxygen and that the amount of this gas dissolved in the solution will be equal to that contained in the same volume of distilled water at the same temperature. To determine this correction, the separating funnel is withdrawn, and in place of it is fixed a second burette similar to the first contain- ing distilled water which has been fully aerated by shaking in a bottle only half full. Coal gas is passed as before, then the blue colour of the liquid in the bottle is destroyed by dropping in the thiosulphate solution ; when this has been done 10 c.c. of the distilled water are run in, and after standing a few minutes the iodine liberated is titrated with thiosulphate solution ^ of this volume equals the correction to be applied for each 1 c.c. of thiosulphate required. The calculation is as follows : Let A be the total amount of thiosulphate used ; B the amount of water used, less 2 c.c. for the reagents added ; C the amount of oxygen dissolved in the reagents ; D the amount of oxygen dissolved in 1 c.c. of the thiosulphate solution ; the number of milligrams of oxygen dissolved in 1 litre of the water. CHEMICAL EXAMINATION 97 Then 1000 If the separator holds exactly 250 c.c. - = unity and the 4B calculation is simplified to = (A C DA). If nitrites should be present in the water these will liberate iodine, thus vitiating the results. In such a case the nitrites must be estimated and the oxygen corresponding to them deducted. Sutton describes the following method of eliminating the oxygen from the sample of water and then determining the effect of the nitrite. 250 c.c. of the water is taken, rendered slightly alkaline if necessary, a few drops of potas- sium iodide solution added and the liquid boiled vigorously for a few minutes. The liquid is then run into the separator and from thence to the bottle, in which it is allowed to become quite cold while a current of coal gas is passing through, 1 c.c. each of the dilute sulphuric acid and starch solution are then run in and the titration performed as before. The amount of oxygen calculated from this is the correction required for the nitrite present in the sample. Nitrates have no influence on the reaction, but oxidisable organic matter, such as urea, etc., contained in sewage, interfere to such an extent as to render the test worthless ; the reaction which takes place between nitrous acid and ammonium salts with liberation of nitrogen and destruction of the nitrous acid would also vitiate the results. Winkler's Process as Modified by Rideal and Stewart.* This method is based upon the very great affinity which manganous hydrate has for oxygen, and the subsequent determination of the oxygen absorbed by liberating iodine from potassium iodide and titrating with thiosulphate. * Analyst, 1901, 141-148, G 98 WATER ANALYSIS The tests are performed in white glass stoppered bottles of about 300 c.c. capacity, of good quality with, stoppers well ground in. Each bottle is weighed empty and also entirely filled with water, the stopper being in in both cases. The difference between the two weighings is the amount of water it will hold, and this should be marked on the bottle with a writing diamond. The weight represents the capacity in c.c's with sufficient accuracy. For the estimation of oxygen, the bottle is filled with the water to be examined, and 1 c.c. of solution of manganous chloride (Appendix X) is added by means of a pipette made from a piece of glass tube drawn out at one end into a very long fine jet which serves to deliver the solution to the bottom of the water with little or no displacement or loss from the bottle. Then 3 c.c. of the mixed solution of caustic soda and potassium iodide are added, and the bottle is closed with the stopper, taking care no air bubbles are included, shaken several times to mix the contents, and allowed to stand for a few minutes. The precipitate, which is flesh-coloured at first, soon becomes brown owing to absorption of the oxygen and quickly settles out. The stopper is now quickly removed and 3 c.c. of concentrated hydrochloric acid delivered into it by means of a similar pipette. The bottle is closed, shaken, and allowed to stand for about five minutes in the dark, the liquid being then transferred to a beaker and titrated with standard sodium thiosulphate solution, using starch paste as indicator to show the end point of the reaction. 1 c.c of standard thiosulphate solution = -0008 gram of oxygen. The reactions which take place are shown in the following equations : 1. MnS0 4 + 2NaHO + .+ H 2 - Mn(OH) 4 + Na 2 S0 4 . 2. Mn(OH) 4 +2KI+4HCl=MnCl 2 + 2KC1 + I 2 + 4H 2 0. CHEMICAL EXAMINATION 99 Organic matter and nitrites entirely vitiate the results, therefore it is necessary in the case of sewages and effluents to oxidise these substances with potassium permanganate. For this purpose a separate portion of the sample is titrated with a standard solution of permanganate to arrive at the amount required for oxidation. Slightly more than this quantity (say 0*1 c.c. over) is then placed along with 1 c.c. of concentrated sulphuric acid in the bottle, which is then filled with the water to be examined and, after it has been allowed to act, the excess is destroyed by the addition of 0*5 c.c. of a two per cent, solution of neutral potassium oxalate. Should the amount of permanganate required for oxidation be more than 10 c.c. then 2 c.c. of sulphuric acid are added. The determination of the oxygen is then carried out as described above, only that a larger quantity of caustic soda is required for neutralizing the acid ; this may be 3 c.c. of a 50 per cent, solution containing 10 per cent, of potassium iodide. The corrections necessary are, in the first place, to deduct the volume of the reagents added from the total volume of the bottle (4 c.c. in an ordinary experiment). To arrive at the volume of water taken it is not necessary to take the hydrochloric acid into account as the oxidation is completed before it is added. In the case of sewage or effluents the volume of reagents added for oxidation must also be deducted. The reagents used may contain oxygen, but the amount is so small as to be negligible. The oxygen in the acid is expelled as described on p. 131. 100 WATER ANALYSIS ESTIMATION OF CARBONIC ACID, OXYGEN AND NITROGEN BY GASOMETRIC METHODS The extraction of the gases dissolved in water preparatory to their analysis is best performed in the apparatus shown at FIG. 8. Apparatus for extraction of the gases from water Harvey's method Fig. 8, which was devised by Harvey.* It consists of a bulb, pear-shaped and open at both ends, connected by means of thick walled rubber tube, on the one hand with a capillary tube and nitrometer, and on the other with a reservoir containing mercury. It can be fitted in a sheet -metal water * Sidney Harvey, Analyst xix. 121. CHEMICAL EXAMINATION 101 bath, the lower tube passing through a rubber cork in the bottom of the bath, thus allowing the rubber tube and mercury vessel to remain outside the bath. In the first place, before fitting up the apparatus, the capacity of the bulb is determined by filling it with water and allowing to drain into a measuring cylinder, or more accurately by weighing. A piece of rubber tube with a screw clamp attached is then drawn over the upper tube and wired on, after which the bulb is filled with water by suction and the clamp closed. The bulb is now fixed in the water bath by passing the lower tube through the rubber cork. When this is done, about one-third of the contents of the bulb are allowed to flow into a measuring glass and this amount deducted from the total volume of the bulb, the remainder being the amount of the water taken for the analysis. The tube containing the mercury reservoir is now wired on, the latter raised and the stopcock opened in order that all the air may be driven out, the water being allowed to pass to the end of the capillary which is then connected to a nitrometer, through which the last trace of air passes and escapes through the funnel. The mercury reservoir is then lowered and the clamp carefully opened so that mercury from the nitrometer passes over into and fills the capillary tubes ; the clamp is now closed, and the water bath filled with cold water, which is heated and kept boiling for two hours, after which the mercury reservoir is raised slowly, the clamp opened, and the gases driven over into the nitrometer. The stopcock of the latter is then closed and the apparatus allowed to remain undisturbed in order that it may cool down to the temperature of the laboratory. The total gas is first measured, then a little strong solution of caustic potash is added to absorb the carbonic acid, followed by a fresh solution of pyrogallol for absorption of the oxygen, the residual gas being nitrogen. The gases are saturated with moisture, and this, together with 102 WATER ANALYSIS the temperature and pressure, must be taken into account in the calculation. If any water condenses from the gases on cooling, the volume of this must be added to the carbonic acid, as water absorbs approximately its own volume of this gas. APPENDICES APPENDIX I STANDARDS OF PURITY RECOMMENDED BY THE RIVERS POLLUTION COMMISSIONERS FOR LIQUIDS ENTERING STREAMS. We recommend that, with certain exceptions in reference to standards (d) and (e), the following liquids be deemed polluting and inadmissible into any stream : (a) Any liquid which has not been subjected to perfect rest in subsidence ponds of sufficient size for a period of at least six hours, or which, having been so subjected to subsidence, contains in suspension more than one part by weight of dry organic matter in 100,000 parts by weight of the liquid, or, which, not having been so subjected to subsidence, contains in suspension more than three parts by weight of dry mineral matter, or one part by weight of dry organic matter in 100,000 parts by weight of the liquid. (b) Any liquid containing, in solution, more than two parts by weight of organic carbon, or 0*3 part by weight of organic nitrogen in 100,000 parts by weight. (c) Any liquid which shall exhibit by daylight a distinct colour when a stratum of it one inch deep is placed in a white porcelain or earthenware vessel. (d) Any liquid which contains, in solution, in 100.000 part* by weight, more than two parts by weight of any metal, except calcium, magnesium, potassium, and sodium. (e) Any liquid, which, in 100,000 parts by weight, contains, whetfier in solution or suspension, in chemical combination or otherwise, more than 0-05 part by weight of metallic arsenic. (/) Any liquid which, after acidification with sulphuric acid, 103 104 APPENDIX I contains, in 100,000 parts by weight, more than one part by weight of free chlorine. (g) Any liquid which contains, in 100,000 parts by weight, more than one part by weight of sulphur, in the condition either of sulphuretted hydrogen or of a soluble sulphuret (sulphide). (h) Any liquid possessing an acidity greater than that which is produced by adding two parts by weight of real muriatic (hydrochloric) acid to 1,000 parts by weight of distilled water. (i) Any liquid possessing an alkalinity greater than that produced by adding one part by weight of dry caustic soda to 1,000 parts by weight of distilled water. (k) Any liquid exhibiting a film of petroleum or hydro- carbon oil upon its surface, or containing, in suspension, in 100,000 parts more than 0'05 part of such oil. APPENDIX II 105 II TABULAR VIEW OF THE STANDARDS FOR EFFLUENTS ADOPTED BY VARIOUS AUTHORITIES d a 1 g 1 H O M 5 1 * - s * w S S |j 3 g 3 1 o P* {M Is 8 3 o 52; S a <5 < O J 9-8 476 M 7-0 379 5 9-7 473 > 6'9 375 J> 9'6 469 6'8 372 9'5 466 }> 6'7 368 J> 9'4 462 J? 6'6 365 )> 9'3 459 1. 6'5 361 9*2 455 j 6'4 358 J> 9-1 452 6'3 354 9'0 448 ?> 6'2 351 J> 8'9 445 ?> 6'1 348 8-8 441 M 6'0 345 8'7 438 w 5'9 341 J 8-6 434 M 5'8 337 J> 8'5 431 _j 5'7 333 )J 8-4 428 ?J 5'6 330 M 8-3 424 ?J 5'5 326 w 8'2 421 5'4 322 ^ 8-1 417 w 5'3 318 j> 8-0 414 H 5'2 314 j> 7-9 410 > 5-1 310 j> 7-8 407 )5 5'0 306 j> 7'7 403 4'9 302 > 7-6 400 4'8 298 7'5 396 JJ 4-7 294 J> 7-4 393 J> 4'6 291 J> 7'3 389 4'5 287 APPENDIX VII 113 Volume evaporated NH:i per 100,000 Loss of N. per 100,000 Volume evaporated NH 3 per 100,000 Loss of N. per 100,000 100 c.c 4'4 283 100 c.c. *7 148 > 4'3 279 6 143 ,, 4'2 275 > 5 137 ,, 4-1 271 4 132 ,, 4-0 267 3 127 ,, 3'9 262 1-2 122 ,, 3'8 257 ri 117 3'7 252 > 1-0 112 3-6 247 250 c.c. 0.9 096 .- 3'5 242 ?J 0'8 080 ?> 3'4 236 M 0-7 070 n 3'3 231 M 0-6 060 j? 3'2 226 500 c.c. 0-5 050 3-1 221 PI 0-4 040 }> 3-0 216 0'3 030 w 2-9 211 1000 c.c. 0-2 020 -_ 2'8 205 M O'l 010 2-7 200 9) 0'09 009 M 2-6 195 JJ 0-08 008 }) 2-5 190 0'07 007 >. 2-4 184 >5 0'06 006 2-3 179 J> 0-05 005 >t 2-2 174 0'04 004 > 2-1 169 M 0-03 003 2-0 164 j> 0-02 002 > 1-9 158 > O'Ol 001 1-8 153 114 APPENDIX VIII VIII WARINGTON'S METHOD OF ESTIMATING NITRATES IN WATER Table showing the parts of N per 100,000 parts of water for each *5 c.c. of indigo oxidised by the nitric acid in 20 c.c. of the water examined. c.c. Indigo N c.c. Indigo N c.c. Indigo N C.C. Indigo N 5 ooo 10-5 437 20-5 899 30'5 384 i-o 021 11-0 459 21'0 923 31-0 408 T5 043 11-5 482 21-5 947 31-5 432 2'0 065 12-0 504 22-0 971 32-0 457 2-5 087 12-5 527 22-5 996 32-5 481 3-0 109 13-0 549 23-0 1-020 33-0 505 3-5 131 13'5 572 23-5 1-044 33-5 530 4-0 153 14-0 594 24'0 1-068 34-0 554 4'5 175 14-5 617 24'5 1-093 34-5 578 5-0 196 15-0 639 25'0 1-117 35-0 603 5-5 218 15'5 662 25'5 1-141 35-5 627 6'0 240 16-0 684 26-0 1-165 36-0 651 6-5 262 16-5 707 26'5 1-190 36-5 676 7-0 284 17-0 730 27-0 1-214 37-0 700 7'5 306 17-5 753 27-5 1-238 37-5 725 8-0 328 18-0 777 28-0 1-262 38-0 750 8-5 350 18'5 801 28'5 1-287 38-5 774 9-0 371 19'0 825 29'0 1-311 39-0 1-798 9'5 393 19'5 850 29'5 1-335 395 1-823 10-0 415 20-0 875 30-0 1-359 40-0 1-847 APPENDIX IX 115 IX Table of hardness in parts per 100,000 (50 c.c. of water used). C.C. of Soap Solution CaCOs per 100,000 C.C. of Soap Solution CaCO :J per 100,000 C.C. of Soap Solution CaCO. per 100,000 7 oo 3'5 3'90 6'3 7-86 8 16 6 4-03 4 S'OO 1) 32 7 16 5 14 ro 48 8 29 6 29 i 63 9 43 7 43 2 79 '4-0 57 8 57 3 95 1 71 9 71 4 rii 2 86 7-0 86 5 27 3 5-00 1 9-00 6 43 4 14 2 14 7 56 5 29 3 29 8 69 6 43 4 43 9 82 7 57 5 57 2'0 95 8 71 6 71 1 2'08 9 86 7 86 2 21 5-0 6'00 8 10-00 3 34 1 14 '9 15 4 47 2 29 80 30 '.-. 60 3 43 1 45 6 73 4 57 2 60 '7 86 5 71 3 75 8 99 6 86 4 90 9 3-12 7 7-00 5 11-05 3'0 25 8 14 6 20 1 38 9 29 7 35 2 51 6-0 43 8 50 3 64 1 57 9 65 4 77 2 71 9-0 80 116 APPENDIX IX C.C. of Soap Solution CaCOg per 100,000 C.C. of Soap Solution CaCO-s per 100,000 C.C. of Soap Solution CaCO ;5 per 100,000 9-1 11-95 11-5 15-63 13-9 19-44 2 1211 6 79 14-0 60 3 26 7 95 1 76 4 41 8 16-11 2 92 5 56 9 27 3 20-08 6 71 12-0 43 4 24 7 86 1 59 5 40 8 13-01 2 75 6 56 9 16 3 90 7 71 10-0 31 4 17-06 8 87 1 46 5 22 9 21-03 2 61 6 38 -^15-0 19 3 76 7 54 1 35 4 91 8 70 2 51 5 14-06 9 86 3 68 6 21 13-0 18-02 4 85 7 37 1 17 5 22-02 8 52 2 33 6 18 9 68 3 49 7 35 11-0 84 4 65 8 52 1 15-00 5 81 "6 69 2 16 6 97 16'0 86 3 32 7 19-13 4 48 8 29 APPENDIX X 117 PREPARATION OF REAGENTS REQUIRED FOR WATER ANALYSES REAGENTS REQUIRED FOR THE ESTIMATION OF FREE AMMONIA 1. Standard Solution of Ammonium Chloride Two solutions of this salt are made : (A) Stock solution by dissolving 0-15735 gram of ammonium chloride in water and making up to one litre. (B) Working solution, by diluting 100 c.c. of the above to one litre. 1 c.c. of this solution = -00005 gram of Ammonia (NH 3 ). 2. Nessler's Solution For the preparation of Nessler's solution, 62*5 grams of potassium iodide are dissolved in about 260 c.c. of distilled water. A saturated solution of mercuric chloride is also prepared by dissolving 35 grams of the salt in 500 c.c. of water. 250 c.c. of the potassium iodide solution are now taken and the mercuric chloride is added gradually, stirring continually until the red precipitate of mercuric iodide which forms ceases to be dissolved. The remaining 10 c.c. of potassium iodide solution is now added, and this should be found sufficient to dissolve the precipitate readily. The mercuric chloride solution is again added, this time drop by drop, until a slight precipitate appears, which does not redissolve even after considerable agitation. To this liquid is added 150 grams of caustic potash dissolved in about an 118 APPENDIX X equal weight of water, and the whole is then made up to one litre. This solution, on standing, becomes quite clear and faintly yellow, with a slight yellowish deposit, which should be left in the bottle. It is best prepared several days previous to using as it becomes more sensitive after it has been kept for some little time. 3. Sodium Carbonate The pure anhydrous salt is heated to low redness in a platinum dish, and while still warm pounded in a mortar and transferred to a clean, dry, stoppered bottle. 4. Water Free from Ammonia Ordinary distilled water is rarely free from ammonia. Previous to being used it is tested with Nessler's reagent, and, if ammonia is found to be present, it is redistilled with a little sodium carbonate, rejecting the first portion, which will be found to contain the whole of the ammonia. REAGENT FOR DETERMINING ALBUMINOID AMMONIA Potassium permanganate 8 grams. Granular caustic soda 200 grams. These are dissolved in water and made up to one litre. This reagent is boiled for ten minutes to ensure the destruc- tion of any organic matter and the expulsion of any ammonia it might contain. It is kept in a bottle closed with a rubber stopper. APPENDIX X 119 REAGENTS REQUIRED FOR THE ESTIMATION OF ORGANIC CARBON AND NITROGEN The reagents used in the determination of organic carbon and nitrogen require to be specially pure, and are made with distilled water free from organic matter and ammonia. 1. Water Free from Organic Matter and Ammonia Ordinary distilled water, to which has been added one gram of caustic potash and -2 grams of potassium permanganate per litre is gently boiled in a flask connected with a reflux con- denser for about twenty-four hours. The water is then distilled with the neck of the retort inclined away from the condenser so that any of the liquid carried up in the form of spray may run back into retort. The first portion of the distillate is thrown away, subsequently a portion is tested with Nessler's reagent, and, if it is found free from ammonia, the remainder is collected, the distillation being stopped before the retort becomes dry. The distillate is slightly acidified with dilute sulphuric acid, and is redistilled from a clean retort with the same precautions as above. 2. Solution ol Sulphurous Acid Sulphurous acid, made by the action of pure sulphuric acid on clean copper turnings, is purified by passage through a three-necked Wolff's bottle containing water, and then conducted into water free from organic matter and ammonia until the liquid is saturated. 3. Solution of Sodium Hydrogen Sulphite Sulphurous acid, prepared as above described, is passed into a solution of pure sodium carbonate prepared with water free 120 APPENDIX X from organic matter and ammonia until small bubbles of carbonic acid cease to be evolved and the liquid smells strongly of the sulphurous acid. 4. Solution of Ferrous Chloride A solution of ferrous sulphate is prepared and precipitated by the addition of a slight excess of caustic soda, the pre- cipitate of ferrous hydrate is quickly washed and dissolved in the least possible excess of pure hydrochloric acid. A solution of pure ferric chloride, however, serves equally well, as it is reduced to ferrous chloride by the sulphurous acid. The solution should be free from ammonia, and must be kept in a glass-capped bottle with pipette. 5. Copper Oxide This is prepared by heating granulated copper, or copper wire cut into small pieces, in a muffle with full access of air till it is fully oxidised. It is cooled in a desiccator and kept in a stoppered bottle. A portion of this copper oxide is powdered in a mortar, passed through a fine sieve, and kept in a separate stoppered bottle. After a combustion has been performed, the tube is broken and the granular copper oxide shaken out. It may be used repeatedly, but it should be roasted in the muffle each time to fully oxidise it. 6. Metallic Copper Fine copper gauze is cut into strips about 80 mm. wide, and rolled upon a piece of thick copper wire, looped at each e id to prevent it falling out ; the whole is then covered with a piece of thin sheet copper without overlapping. Several APPENDIX X 121 of these cylinders are placed together in a combustion tube and heated in a current of air, the furnace is then allowed to cool, hydrogen passed through, and the tube again heated to redness for a few minutes. The tube is allowed to cool in the stream of hydrogen and the cylinders removed to a stoppered bottle. They require to be reduced in this way from time to time. 7. Solution of Phosphoric Acid 100 grams of pure glacial metaphosphoric acid is dissolved in distilled water and made up to one litre. 10 c.c of this should be diluted to 100 c.c. with distilled water and tested with Nessler's solution ; it should be free from ammonia. 8. Calcium Phosphate This is prepared by precipitating a solution of sodium phosphate with one of calcium chloride, the precipitate is washed with water by decantation, drained, dried at 100 C. and heated to redness for about an hour. REAGENTS REQUIRED FOR THE ESTIMATION OF NITRATES AND NITRITES WARINGTON'S INDIGO PROCESS 1. Stock Solution of Potassium Nitrate This is prepared by dissolving 1-011 grams of pure potas- sium nitrate in water and making up to one litre. This solution is of T -J-^th normal strength, and from it the working standard solution is made by dilution. 122 APPENDIX X 2. Working Standard Solution of Potassium Nitrate Is made from the above by diluting 30 c.c. up to 960 c.c. with distilled water, this solution is of 3^^ strength, and is equal to 0*437 part of N per 100,000. 3. Indigo Solution A strong solution is first prepared by macerating 4 grams of indigotin with an equal weight of Nordhausen (fuming) sulphuric acid, when the solution is completed a 4 per cent, solution of sulphuric acid is gradually added in sufficient quantity to make one litre. This forms a stock solution from which the working solution is prepared. For the preparation of the working solution 100 c.c. of the strong solution, prepared as above, is first diluted to one litre, and its strength is determined by titration against 20 c.c. of the standard solution of potassium nitrate, as described under the determination of nitrates (p. 40). The solution is then further diluted until 20 c.c. of the standard solution of potas- sium nitrate just discharges the blue colour of 10 c.c., but with 10-5 c.c. there is a faint blue tint. All the dilutions are made with a 4 per cent, solution of sulphuric acid. 4. Mixed Sulphuric Acid In the original test the temperature of the liquid was kept at about 140 C. by immersion in a calcium chloride bath, but it is preferable to produce the temperature imme- diately by the addition of a mixture of fuming and ordinary sulphuric acid. The mixture is made with one volume of fuming acid and three volumes of ordinary sulphuric acid. 20 c.c. of this mixture, quickly poured into an equal volume of distilled water, raises the temperature to 180 C. APPENDIX X 123 This mixture of acids should be entirely free from nitrates ; sometimes, however, traces are present ; these are estimated and -corrected for by running 20 c.c. of the acid into 20 c.c. of distilled water containing 0'5 c.c. of indigo solution, and, if the colour is discharged, adding the latter drop by drop till the blue tint reappears. The volume of indigo solution required in this blank test should be deducted from all sub- sequent determinations. If, however, the amount of indigo required is high the acids should be rejected. CRUM'S PROCESS 1. Concentrated Sulphuric Acid This must be entirely free from nitrous and nitric acids. 2. Potassium Permanganate Solution Made by dissolving 10 grams of pure potassium perman- ganate in one litre of water. 3. Sodium Carbonate Solution Prepared by dissolving 10 grams of pure dry sodium car- bonate in one litre of water. SPRENGEL'S OR PHENOL-SULPHURIC ACID PROCESS 1. Phenol-Sulphuric Acid Pure colourless phenol is melted on a water bath and 80 c.c. of the liquid added to 200 c.c. of pure concentrated sulphuric acid ; the mixture is heated for eight hours on a water bath and cooled, to this are added 140 c.c. of pure concentrated hydrochloric acid and 420 c.c. of water. 124 APPENDIX X 2. Standard Solution of Potassium Nitrate 0*7215 gram of pure potassium nitrate is dissolved in water and made up to 1 litre ; 1 c.c. of the solution = -0001 of N or 1 part in 100,000. A weaker solution is made from this by diluting 100 c.c. to one litre. 1 c.c. of the latter = -00001 of N or 0-1 part in 100,000. REAGENTS REQUIRED FOR ESTIMATION OF NITRITES GREISS'S PROCESS 1. Metaphenylene-diamine Solution Prepared by dissolving 0'5 gram of metaphenylene-diamine base in dilute sulphuric acid and diluting to 100 c.c. If the solution is highly coloured it may be bleached by treat- ment with animal charcoal (freed from phosphate) ; but there should be no difficulty in obtaining a pure product. 2. Solution of Sulphuric Acid One volume of sulphuric acid (free from nitrous acid) is diluted with two volumes of water. 3. Standard Solution of Potassium Nitrite The ordinary potassium nitrite of commerce is not suffi- ciently pure to be used for making a standard solution, the salt has therefore to be prepared by double decomposition from silver nitrite, and, as it rapidly oxidises, a fresh solution is required for each batch of determinations. Fortunately the estimation of nitrites is not often required. APPENDIX X 125 Pure silver nitrite is first prepared by the addition of potassium nitrite to silver nitrate, this is washed with distilled water by decantation and then dried at a low temperature on a watch glass in the dark. It easily decomposes, especially in contact with organic matter, for which reason special care has to be taken in its preparation. 0*405 gram of this pure silver nitrite is dissolved in distilled water ; this should be hot but not actually boiling. To this is added a solution of pure potassium chloride till no further precipitate of silver chloride is formed. The liquid is quickly cooled and made up to one litre. After the precipitate has subsided, 100 c.c. of the clear liquid is pipetted off and made up to one litre. 1 c.c. = -00001 gram N 2 3 , or -0000037 gram N. as nitrite. REAGENTS REQUIRED FOR THE ESTIMATION OF OXYGEN ABSORBED FORCHAMMER'S PROCESS 1. Standard Solution of Potassium Permanganate This is made by dissolving 0'395 gram of pure potassium permanganate in distilled water and making up to one litre. 10 c.c. of this solution = -001 of available oxygen. The solution is not perfectly stable, therefore it should be made up afresh at frequent intervals. 2. Solution of Sodium Thiosulphate Is made as required, and contains 0'5 gram of the salt in one litre. It need not be accurate. 126 APPENDIX X 3. Dilute Sulphuric Acid Strength one volume of acid to three volumes of water. A large quantity of this is prepared. As sulphuric acid often contains oxidisable matters, sufficient permanganate solution is added to it to render it very faintly pink, and it is then allowed to stand. 4. Potassium Iodide Solution This is a 10 per cent, solution. 5. Starch Paste Made by rubbing up 1 part of starch with 20 parts of water and heating to the boil. Soluble starch is preferable to ordinary starch for this purpose because it forms a thin clear solution. It should be preserved with a trace of mercuric chloride, or made up often, as it goes mouldy. REAGENTS REQUIRED FOR ESTIMATION OF CHLORINE 1. Standard Solution of Silver Nitrate 2 '3944 grams of pure re-crystallized silver nitrate dis- solved in distilled water and made up to one litre. 2. Solution of Potassium Chr ornate A strong solution of pure neutral potassium chromate (free from chloride) is prepared. 3. Standard Solution of Sodium Chloride Prepared by dissolving 01649 gram of pure sodium chloride in water and making up to one litre. This = 10 parts of 01. per 100,000. The silver nitrate solution is standardized against this. APPENDIX X 127 REAGENTS REQUIRED FOR ESTIMATION OF HARDNESS CLARK'S PROCESS 1. Standard Solution of Calcium Chloride Sometimes known as " Standard Hard Water." 0-2 gram of pure cryst. calcite is dissolved in dilute hydrochloric acid in a platinum dish, the dish being covered with a clock glass to prevent loss by spurting. When solution is complete the cover is removed, washed down with distilled water, and the solution evaporated to dryness, then a little water is added and the solution again evaporated. This is repeated several times to completely expel the excess of acid. Finally the calcium chloride is dissolved in distilled water and the solution made up to one litre. A standard hard water is made by some from barium chloride, but this is not to be recommended. 2. Standard Soap Solution 150 grams of lead plaster (oleate of lead) and 40 grams of dry potassium carbonate are rubbed together in a mortar. A small quantity of methylated spirit is now added and the whole thoroughly mixed until it forms a smooth, uniform, creamy mass. After standing several hours it is passed through a filter paper, the residue being treated with successive quan- tities of alcohol until the filtrate is made up to one litre. An alternative process is to dissolve 40 grams of white castile soap in methylated spirit, filter, and make up to one litre. It is advisable to store the solution in a cold place for several days, subsequently filtering off the flocculent precipi- tate which is formed. The strength of the soap solution is determined by taking 50 c.c. of the standard hard water and titrating, as described on p. 62. The soap solution is then diluted until 14*25 c.c. 128 APPENDIX X are equivalent to 50 c.c. of the standard hard water. The dilution is made with a mixture of 2 parts of spirit and 1 part of Water, calculating the soap solution as spirit. For instance, if 3 c.c. of the strong soap solution were required to produce a lather with 50 c.c. of the standard hard water, the dilution would be made as follows : Strong soap solution 300 c.c. } Methylated spirit 650 c.c.J = Water 475 c.c. 1 Total 1425 c.c. After dilution the solution should be again checked against the standard hard water and if necessary its strength further adjusted. REAGENTS REQUIRED FOR THE ESTIMATION OF LEAD 1. Standard Solution of Lead Acetate Made by dissolving 0-1831 gram of pure lead acetate Pb(C 2 H 3 2 ) 2 2H 2 in distilled water and diluting to one litre. 1 c.c. = -0001 gram Pb. 2. Dilute Hydrochloric Acid 1 part of pure hydrochloric acid diluted with 3 parts of water. 3. Sulphuretted Hydrogen This is best evolved as a gas from a generator when required, and purified by passing through a wash bottle con- taining a little water. APPENDIX X 129 REAGENTS REQUIRED FOR ESTIMATION OF COPPER 1. Standard Solution of Copper Sulphate Prepared by dissolving 0-3927 gram of pure copper sulphate, CuS0 4 5H 9 0, in water and diluting to one litre. 1 c.c. = -0001 gram Cu. 2. Dilute Hydrochloric Acid and Sulphuretted Hydrogen As p. 128. REAGENTS REQUIRED FOR ESTIMATION OF IRON 1. Standard Solution of Ferrous Salt 0-4977 gram of pure ferrous sulphate, FeS0 4 .7H 2 is dissolved in water, a few drops of dilute sulphuric acid are added, and the solution made up to one litre with distilled water which has been boiled to expel oxygen and cooled out of contact with air. The solution should be used imme- diately after it is made. 1 c.c. = -0001 gram Fe. 2. Standard Solution of Ferric Salt 0-4977 gram of pure ferrous sulphate is dissolved in a little water and oxidised by heating with nitric acid, the solution is evaporated to dryness with strong hydrochloric acid, this evaporation with hydrochloric acid is repeated several times to expel the whole of the nitric acid, finally the residue is dissolved in a few drops of dilute hydrochloric acid and made u p to one litre. T 130 APPENDIX X REAGENTS REQUIRED FOR ESTIMATION OF OXYGEN THRESH'S METHOD 1. Solution oi Potassium Iodide and Sodium Nitrite Sodium nitrite 0'5 gram. Potassium iodide 20 grams. Distilled water 100 c.c. 2. Dilute Sulphuric Acid One volume of pure sulphuric acid to three volumes of distilled water. 3. Standard Solution of Sodium Thiosulphate 7 '75 grams of pure sodium thiosulphate dissolved in water and made up to one litre. 1 c.c. = -00025 gram of 0. 4. Starch Paste 1 part of starch with 40 parts of boiling water. WINKLER'S PROCESS 1. Solution of Manganous Chloride 50 grams of manganous chloride, MnCl 2 .4H 2 0, is dissolved in distilled water and made up to 100 c.c. = 33 per cent, of MnCJg. 2. Solution of Caustic Soda and Potassium Iodide 33 grams of pure caustic soda and 10 grams of potassium iodide are dissolved in water and made up to 100 c.c. APPENDIX X 131 3. Hydrochloric Acid Pure hydrochloric acid is freed from oxygen by passing through it a current of carbonic acid and then boiling. 4. Standard Sodium Thiosulphate Solution N strength. 1 c.c. = -000084 gram or '06 c.c. REAGENTS REQUIRED FOR ESTIMATION OF THE MINERAL CONSTITUENTS These should be specially pure, as the slightest trace of impurities may cause considerable errors in the estimations. Any impurities the reagents are likely to contain should be tested for previous to use. INDEX ACID, nitric, estimation, 80 nitrous, estimation, 80 phosphoric, estimation, 79 sulphuric, estimation, 76 radicles, 76 Acids, mineral, estimation, 70 non-volatile, estimation, 70 volatile, estimation, 70 and bases, methods of com- bining, 80 Acidity, 69 total, estimation, 69 Action of water on lead, 85 Air, proportion of gases in, 91 Albuminoid ammonia, estimation of, 14 amount in waters, 16 preparation of reagents, 118 quantity yielded by various substances, 15 Albuminoid organic ammonia, 14 Alkaline permanganate, preparation of, 118 Alkalies present as carbonates, esti- mation, 75 Alkali metals, estimation, 73 Alkalinity, determination of, 68 Aluminium, determination of, 71 Ammonia, how formed, 9 albuminoid or organic, 14 and organic matter, preparing water free from, 119 free and saline, estimation of, 9 amount in various waters, 14 preparation of reagents, 117 preparing water free from, 118 Ammonium sulphite, loss of nitrogen on evaporation of, 111 phosphate, loss of nitrogen on evaporation of, 112 Amount of water required for analysis, 3 Apparatus for estimation of free ammonia, 10 nitrogen as nitrates, 42, 44 organic carbon and nitrogen, 24, 30 oxygen dissolved, 94 gases in water, 100 Aqueous vapour, tension of, 107 Arsenic in water, 83 estimation of, 88 Average composition of unpolluted water, 106 BARIUM hydrate solution, prepara- tion of, 78 Basic radicles, estimation of, 70 Boiler purposes, examination of water for, 3 Brewing waters, combining acids and bases, 81 CALCIUM, estimation, 72 Calculation of results, 13, 35, 45, 46, 48, 49, 56, 64, 69, 80, 96 Carbon compounds in waters, 21 Carbonates, estimation, 75 Carbonic acid, combined and free, 77 combined and free, estimation, 79 free, estimation, 77 estimation by gasometric method, 100 Caustio soda, estimation of, in presence of carbonate, 68 Chemical examination, 9 Chlorine, amount of, in various waters, 58 estimation, 59 133 134 INDEX Clark's process for determining hardness, 62 preparation of reagents, 123 tables of hardness, 63 Collection of samples, 4 Colour, 123 Copper, estimation, 87 reagents required, 129 in water, 83 Crum's process for estimating nitrates, preparation of reagents, 123 DEGREES of hardness, English, French, and German, 65 Deleterious metals, 83 Derbyshire County Council, standards of purity adopted for effluents, 105 EFFLUENTS from paper works, deter- mining alkalinity of, 68 sewage works, 2, 19 standards of purity, 105 Electrolytic method for estimating nitrates, 46 FALSE lather in determining hard- ness, 62 Ferrous salt, estimation of, 89 Ferric salt, estimation of, 90 GAS analysis, estimation of organic carbon and nitrogen, 33 carbonic acid, oxygen, and nitro- gen, 100 Gases in waters, 92 proportion of, in air, 91 in water, 91 Gasometric methods of estimating carbonic acid, oxygen, and nitro- gen, 100 German degrees of hardness, 65 Gladstone and Tribe's copper zinc couple, 46 Greiss's processf or estimating nitrites, 51 preparation of reagents, 124 HARDNESS, 60 Clark's process for determining, table, 63 Hardness, English, French, and German degress, 65 false lather, 62 Hehner's process, 66 of various waters, 65 permanent, estimation, 64, 67 preparation of reagents, 127 tables, 63, 115 temporary and permanent, 61 total, estimation, 62 Hehner's process for estimating hard- ness, 66 INDIGO, process for estimating nitrates, 40 preparation of reagents, 131 solution, standard, preparing, 122 Introduction, 1 Iron as ferrous salt, 89 as ferric salt, 90 estimation of, 70, 89 preparation of reagents, 129 in water, 83 LATHER, false, 62 Laundry purposes, analysis of water for, 3 Lead, action of water on, 85 estimation of, 84 preparation of reagents, 128 in water, 83 Loss by evaporation of NH 4 HSO.,, Ill NH 4 H. 2 P0 4 , 112 on ignition, 17 Lovibond's tintometer, 5 MAGNESIUM compounds, effect on soap test, 62 estimation, 73 Manganese, estimation, 73 Mersey and Irwell Joint Commis- sioners, standards of purity fixed for effluents, 105 Metals, alkali, estimation, 73 deleterious, 83 Method of combining acids and bases, 80 _ Micro-organisms giving rise to odours, 7 Microscopic examination, 7 Mineral acid, estimation, 70 constituents, purity of reagents required in estimating, 131 INDEX 135 NESSLER'S solution, preparation of, 117 Nitrates, estimation of, 40, 43, 46 preparation of reagents, 121, 122, 124 how formed, 38 qualitative test for, 50 Nitric acid, estimation, 80 Nitrites in water, 50 estimation, 51 preparation of reagents, 124 qualitative tests for, 52 Nitrogen as nitrates, estimation of, 40, 43, 46 table for, 114 nitrites, estimation of, 51 Nitrogen compounds in waters, 22 gasometric method of estimating, 100 loss of, by evaporation of NH.HSOo, 111 NH 4 H,P0 4 , 112 organic carbon and, relation of, reduction of c.c. to grams, 110 Nitrous acid, estimation, 80 Non-volatile acids, estimation, 70 ODOUR, 6 Organic carbon and nitrogen, estima- tion, 21 preparation of reagents, 119 quantity present in waters, 38 relationship of, 38 Organic matter and ammonia, pre- paration of water free from, 119 volatile, 22 Organisms in water, 7 causing odours, 7 Oxygen absorbed, 53 by various waters, 57 calculation of results, 56 estimation, 55 method for sewages, &c., 57 relation of, to carbon, 54 preparation of reagents, 125 Oxygen dissolved, estimation, 93, 97 by gasometric methods, 100 preparation of reagents, 130 PAPER works, effluents from, 68 Permanganate, alkaline, preparing, 118 process for estimating oxygen absorbed, 53 Permanent hardness, 64 Phenol-sulphuric acid process for estimating nitrates, 48 preparation of reagents, 123 Phosphoric acid, estimation, 79 Physical examination, 5 Potassium, estimation, 73 Preparation of reagents, 117 Pump, Sprengel, 29 Purity of reagents, 131 QUALITATIVE test for nitrates, 50 nitrites, 52 Quantitative analysis for sanitary purposes, 9 of the mineral constituents, 68 RADICLES, acid, estimation, 76 basic, estimation, 70 Reagents, preparation of, 117 purity of, 131 Reduction of c.c. of. nitrogen to grams, 110 Relation of oxygen absorbed to carbon in waters, 54 Results, calculation of, 35, 45, 46, 48, 49, 56, 64, 69, 80, 96 Ribble Board, standards of purity adopted for effluents, 103 Rivers Pollution Commissioners, standards of purity adopted for effluents, 103 SALINE and free ammonia, amount of, in waters, 14 estimation of, 9 preparation of reagents, 117 Samples, collection, 4 Sanitary analysis, 2 full, 3 Sewage, analysis, 3 and sewage effluents, estima- tion of oxygen absorbed, 57 Silica, estimation, 76 Soap solution for hardness, 127 Clark's table, 63 table for converting c.c. into parts carbonate of lime per 100,000, 115 136 INDEX Soda, caustic, estimation in presence of carbonate, 68 Sodium, estimation, 73 Solids in solution, estimation, 16 amount of, in waters, 17 loss on ignition, 17 suspension, estimation, 19 loss on ignition, 20 Sprengel pump, 29 Sources of supply, 1 Standard solutions, preparing, 117, 122, 124, 126, 129 Standards of purity adopted by various authorities, 103, 105 Sulphides, estimation, 76 Sulphuretted hydrogen, estimation, 76 Sulphuric acid, estimation, 76 Suspended matter, estimation, 5 TABULAR view of the standards for effluents, 105 Taste, 6 Temporary and permanent hardness, 64, 67 Tension of aqueous vapour, 107 Thames Conservancy, standards adopted for effluents, 105 Thresh's method for estimating oxygen dissolved, 93 Tintometer, Lovibond's, 5 Total acidity, estimation, 69 hardness, estimation, 62 solids, estimation, 16 amount "of, in waters, 17 UNPOLLUTED water, average com- position of, 106 VAPOUR, tension of aqueous, 117 Volatile acid, estimation, 70 organic matter, 22 WARINGTON'S process for estimating nitrates, 40 preparation of reagents, 121 Water, action of, on lead, 85 amount of, required for analysis, 3 chlorine in, 58 hardness in, 65 organic carbon and nitrogen in, 38 carbon compounds in, 21 composition of pure, 1, 106 free from ammonia, preparation of, 118 and organic matter, pre- paration of, 119 gases dissolved in, 91 arsenic, lead, iron, copper, and zinc in, 83 nitrogen compounds in, 22 oxygen absorbed by, 53 proportion of gases in, 91 relationship of carbon to nitro- gen in, 54 to oxygen absorbed, 54 unpolluted, average composition of, 106 Winckler's process for estimating oxygen, 97 preparation of reagents, 130 Zixc in water, 83 estimation, 89 BALLAXTYNE & COMPANY LTD. 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In Extra Grown 8vo, with 620 pp. and over 460 Illustrations. 15s. net. ourrx^XNEzs OF PRACTICAL PHYSIOLOGY: Being a Manual for the Physiological Laboratory, including 1 Chemical and Experimental Physiology, with Reference to Practical Medicine. PART I. CHEMICAL PHYSIOLOGY. PART II. EXPERIMENTAL PHYSIOLOGY. " Professor Stirling has produced THE BEST TEXT- BOOK ON PRACTICAL PHYSIOLOGY WHICH HAS APPEARED SINCE the publication of Sir J Burdon Sanderson's and his collaborator's well-known 'Handbook to the Phy>iological Laboratory,' published in 1875. The text is fall and accurate and the illustrations are numerous and well executed. . . . We do not think that the reader will ANYWHERE find so REMARKABLE and INTERESTING a collection of experiments on the eye. ear, and skin as are here given. . . . The work will prove a useful reminder even to lecturers." TVze Lancet (on the New Edition), THIRD EDITION. In Extra Croivn 8vo, with 368 Illustrations, Cloth 12s. &d. In Preparation. ouTH-riNrjES OF PRACTICAL HISTOLOGY: A Manual for Students. %* Dr. Stirling's " Outlines of Practical Histology" is a compact Hand- book for students, providing a COMPLETE LABORATORY COURSE, in which almost every exercise is accompanied by a drawing. Very many of the illustrations have been prepared expressly for the work. " The volume proceeds from a MASTER in his craft. . . . We can confidently re- commend this small but CONCISELY- WRITTEN and ADMIRABLY ILLUSTRATED work to students. They will find it to be a VERY USEFUL and RELIABLE GUIDE in the laboratory, or in their own room. All the principal METHODS of preparing tissues for section are given, with such precise directions that little or no difficulty can be felt in following them in their most minute details." Lancet. " The general plan of the work is ADMIRABLE. . . . It is very evident that the sug- gestions given are the outcome of a PROLONGED EXPERIENCE in teaching Practical Histology, combined with a REMARKABLE JUDGMENT in the selection of METHODS. . . . Merits the highest praise for the ILLUSTRATIONS, which are at once clear and faithful." British Medical Journal. LONDON: CHARLES GRIFFIN & CO,, LIMITED, EXETER STREET, STRAND. STUDENTS' TEXT-BOOKS. 91 In Large Crown Svo. Handsome Cloth. Beautifully Illustrated. 6s. net. The Plant Cell: Its Vital Processes and Modifications. BY HAROLD AXEL HAIG, M.B., B.S., M.R.C.S., L.R.C.P. This volume contains a unique and beautiful series of micro-photographs and many illustrations from drawings by the author. For Medical Students in the Branch of Botany, and Biology generally. In Large Svo. With 36 Plates and Blank Pages for MS. Notes. Cloth, 12s. Gd. THE PHYSIOLOGIST'S NOTE-BOOK: A Summary of the Present State of Physiological Science for Students. BY ALEX HILL, M.A., M.D., Master of Downing College and formerly Vice-Chancellor of the University of Cambridge GKNERAL CONTEXTS : The Blood Vascular System Nerves Muscle- Digestion Skin Kidneys Respiration The Senses Voice and Speech Central Nervous System Reproduction Chemistry of the Body. The Lancet says of it : "The work which the Master of Downing College modestly compared to a Note-book is an ADMIRABLE COMPENDIUM of our present information. . . . Will be a REAL ACQUISITION to Students. . . . Gives all ESSENTIAL POINTS. . . . The TYPOGRAPHICAL ARRANGEMENT is a chief feature of the book. . . . Secures at a glance the EVIDENCE on both . sides of a theory." %* For Dr. Hill's Translation of Prof. Obersteiner's Central Nervous Organs, see p. 80. A ZOOLOGICAL POCKET-BOOK; Or, Synopsis of Animal Classification. Comprising Definitions of the Phyla, Classes, and Orders, with Explanatory Remarks and Tables. By Dr. EMIL SELENKA, Professor in the University of Erlangen. Authorised English translation from the Third German Edition. By Prof. AINSWORTH DAVIS. In Small Post Svo, Interleaved for the use of Students. Limp Covers, 45. "Dr. Selenka's Manual will be found useful by all Students of Zoology. It is a COMPRE- HENSIVE and SUCCESSFUL attempt to present us with a scheme of the natural arrangement of the animal world." Edin. Med. Journal. LONDON: CHARLES GRIFFIN & CO., LIMITED, EXETER STRFET, STRAND. 9 2 GHARLBS GRIFFIN 4 OO.'S PUBLICATIONS. /fn E/ementarj/ Text-Book OF ZBIOLOO- BY J. R. AINSWORTH DAVIS, M.A., F.Z.S., PROFESSOR OF BIOLOGY, UNIVERSITY COLLEGE, ABERYSTWYTH EXAMINER IN ZOOLOGY, UNIVERSITY OF ABERDEEN. SECOND EDITION. In Two Volumes. Sold Separately. I. VEGETABLE MORPHOLOGY AND PHYSIOLOGY. General Contents. UNICELLULAR PLANTS (Yeast-plant, Germs and Microbes, White Mould, Green Mould, &c., &c.) SIMPLE MULTICELLULAR PLANTS (Wrack, Stoneworts, &c.) THE Moss PTERIDOPHYTES (Bracken and Male Shield Ferns, &c.) PLANT CELLS AND TISSUES GYMNOSPERMS (the Fir) ANGIOSPERMS (Buttercup, Snowdrop) VEGETATIVE ORGANS OF SPERMAPHYTES REPRODUCTIVE ORGANS OF ANGIOSPERMS PHYSIOLOGY OF HIGHER PLANTS DEVELOPMENT OF ANGIOSPERMS COMPARATIVE VEGETABLE MORPHOLOGY AND PHYSIOLOGY CLASSIFICATION OF PLANTS. With Complete Index- Glossary and 128 Illustrations. 8s. 6d. II. ANIMAL MORPHOLOGY AND PHYSIOLOGY. General Contents. PROTOZOA: Amoeba (Proteus Animalcule), Vorticella (Bell Animalcule), Gregarina CCELENTERATA : Hydra (Fresh-Water Polype), &c. PLATYHELMIA (Flat- worms) : Liver-fluke, Tapeworm NEMATHELMIA (Thread- worms) ANNELIDA (Segmented Worms) : Earthworm, Leech ARTHROPODA : Crayfish MOLLUSCA : Fresh-Water Mussels, Snail VERTEBRATA ACRANIA : Amphioxus (Lancelet) PISCES (Fishes) : Dogfish AMPHIBIA : Frog AVES (Birds) : Pigeon and Fowl MAMMALIA : Rabbit COMPARATIVE ANIMAL MORPHOLOGY AND PHYSIOLOGY MAN CLASSIFI- CATION and DISTRIBUTION OF ANIMALS. With Complete Index-Glossary and 108 Ilhistrations. los. 6d. NOTE The SECOND EDITION has been thoroughly Revised and Enlarged, and' includes all the leading selected TYPES in the various Organic Groups. "Certainly THE BEST 'BIOLOGY' with which we are acquainted. It owes its pre- eminence to the fact that it is an EXCELLENT attempt to present Biology to the Student as a CORRELATED AND COMPLETE SCIENCE." British Medical J ournal. "CLEAR and COMPREHENSIVE." Saturday Review. " Literally PACKED with information." Glasgow Medical Journal. DAVIS (Prof) : THE FLOWERING PLANT. (See p. 70 General Catalogue. ) DAVIS AND SELENKA: ZOOLOGICAL POCKET-BOOK. (See p. 91.) LONDON : CHARLES GRIFFIN & CO,, LIMITED, EXETER STREET, STRAND. STUDENTS' TEXT-BOOKS. 93 SIXTH EDITION, Revised. With Numerous Illustrations. 55. AN INTRODUCTION TO THE STUDY OF 1 3D "W I IB 1 IE IR, TT . For the Use of Young Practitioners, Students, and Midwives. BY ARCHIBALD DONALD, M.A., M.D., C.M.EDiN., Obstetric Physician to the Manchester Royal Infirmary ; Honorary Surgeon to St. Mary's Hospital for Women, Manchester. " HIGHLY CREDITABLE to the Author. . . . Should prove of GREAT VALUK to Midwifery Students and Junior Practitioners." British Gynecological Journal. "As an Introduction to the study of Midwifery NO BETTER BOOK could be placed in the hands of the Student." Sheffield Med. Journal. FOURTH EDITION, Thoroughly Revised. With Illustrations. 75. 6d. OUTLINES OF THE DISEASES OF WOMEN. A CONCISE HANDBOOK FOR STUDENTS. By JOHN PHILLIPS, M.A., M.D., F.R.C.P., Professor of Obstetric Medicine and the Diseases of Women, King's College Hospital ; Senior Physician to the British Lying-in Hospital ; Examiner in Midwifery and Diseases of Women, University of London and Royal College of Physicians. \* Dr. Phillips' work is ESSENTIALLY PRACTICAL in its nature, and will be found invaluable to the student and young practitioner. " Contains a GREAT DEAL OP INFORMATION in a VERY CONDENSED form. . . . The value of the work is increased by the number of sketch diagrams, some of which are HIGHLY INGENIOUS." Edin. Med. Journal. " Dr. PHILLIPS' MANUAL is written in a SUCCINCT style. He rightly lays stress on Anatomy. The passages on CASE-TAKING are EXCELLENT. Dr. Phillips is very trustworthy throughout in his views on THERAPEUTICS. He supplies an excellent series of SIMPLE but VALUABLE PRESCRIPTIONS, an INDISPENSABLE REQUIREMENT for Students." Brit. Med. Journal. " This EXCELLENT TEXT-BOOK . . . gives just what the student requires. . . . The prescriptions cannot but be helpful." Afedicat Press. LONDON: CHARLES GRIFFIN & CO., LIMITED, EXETER STREET, STRAND. 94 CHARLES GRIFFIN A OO.'S PUBLICATIONS. In Extra Crown Sw, with Litho-plates and Numerous Illustrations. Cloth, Ss. 6d. ELEMENTS OF PRACTICAL PHARMACY AND DISPENSING, BY W. ELBORNE, B.A.CANTAB., F.L.S., F.C.S., Demonstrator of Materia Medica and Teacher of Pharmacy at University College, London; Pharmacist to University College Hospital. GENERAL CONTENTS. Part I. Chemical Pharmacy and Laboratory Course. Part II. Galenical Pharmacy and Laboratory Course. Part III. A Practical Course of Dispensing, with Fae-Similes of Autograph Prescriptions. ' ' A work which we can veiy highly recommend to the perusal of all Students of Medicine. . . . ADMIRABLY ADAPTED to their require- ments." Edinburgh Medical Journal. "The system . . . which Mr. Elborne here sketches is thcn-oughly sound." Chemist and Druggist. \* Formerly published under the title of " PHARMACY AND MATERIA MEDICA." Crown Svo. Handsome Cloth. With Diagrams. 7s. 6d. net. TOXINES AND ANTITOXINES. BY CARL OPPENHEIMER, PH.D., M.D., Of the Physiological Institute at Erlangen. TRANSLATED FROM THE GERMAN BY C. AINSWORTH MITCHELL, B.A., F.I.C., F.C.S. With Notes, and Additions by the Author, since the publication of the German Edition Deals with the theory of Bacterial, Animal, and Vegetable Toxines, such as Tuberculin, Ricin, Cobra Poison, &c. "... Brings together within the compass of a handy volume, all that is of importance. . . . For wealth of detail we have no small work on toxines which equals the one under review." Medical Times. Large Svo, Handsome Cloth. 16s. LUNATIC ASYLUMS; THEIR ORGANISATION AND MANAGEMENT. BY CHARLES MERCIER, M.B., Lecturer on Neurology and Insanity , Westminster Hospital Medical School; Late Senior Assistant-Medical Officer at Leavesden Asylum, and at the City of London Asylum. ABSTRACT OF CONTENTS. Part I. Housing. Part II. Food and Clothing. Part III. Occu- pation and Amusement. Part IV. Detention and Care. Part V. The Staff. " Will give a much-needed IMPETUS to the study of Asylum Patients." Glasgow Medical Journal. LONDON: CHARLES GRIFFIN < CO,, LIMITED, EXETER STREET, STRAND, PRACTICAL MEDICAL HANDBOOKS. 95 "When in doubt, look in ' Humphry.' " Nursing Record. THIRTY-THIRD EDITION, Revised. With Numerous Illustrations, 3*. 6d. A MANUAL OF NURSING: /iDe&ical anfc Surgical. BY LAURENCE HUMPHRY, M.A., M.D, M.R.C.S, Physician and late Lecturer to Probationers at Addenbrooke's Hospital, Cambridge ; Teacher of Pathology and Examiner in Medicine^ University ofCambtidge. GENERAL CONTENTS. The General Management of the Sick Room in Private Houses General Plan of the Human Body Diseases of the Nervous System Respiratory System Heart and Blood-Vessels Digestive System Skin and Kidneys Fevers Diseases of Children Wounds and Fractures- Management of Child-Bed Sick-Room Cookery, &c., &c. " In the fullest sense Dr. Humphry's book is a DISTINCT ADVANCE on all previous M anuals." British. Medical Journal. " We should advise ALL NURSES to possess a copy of the work. We can confidently re- commend it as an EXCELLENT GUIDE and companion. ' Hospital. In Crown 8vo. Handsome Cloth. 3s. net. THE TREATMENT OF DISEASES OF THE DIGESTIVE SYSTEM. BY ROBERT SAUNDBY, M.D., M.Sc., LL.D., F.R.C.P., Professor of Medicine in the University of Birmingham, &c. GENERAL CONTENTS. Introduction. The Influence of the General Mode of Life and of Diet upon the Digestive Organs. Diseases of the (Esophagus: (a) Organic ; (6) Functional. Diseases of the Stomach: (a) Organic; (6) Constitutional ; (c) Functional. Indications for Operative Interference in Diseases of the Stomach. Diseases of the Intestines: (a) Organic; (6) Functional ; (c) Parasites ; (d) Diseases of the Rectum. Symptomatic Diseases. INDEX. 'The book is written with fulness of knowledge and experience, and is inspired throughout by a sane judgment and shrewd common sense." British Medical Journal. FOURTH EDITION, Thoroughly Revised. Handsome Cloth, 4. FOODS AND DIETARIES: H Manual of Clinical Dietetics* BY SIR R. W. BURNET, M.D., F.R.C.R, Phytician in Ordinary to H.R.H. the Prince of WaJes; Senior Physician to the Oreat Northern Central Hospital, Ac. GENERAL CONTENTS. DIET in Diseases of the Stomach, Intes- tinal Tract, Liver, Lungs, Heart, Kidneys, &c. ; in Diabetes, Scurvy, Anae- mia, Scrofula, Gout, Rheumatism, Obesity, Alcoholism, Influenza, Nervous Disorders, Diathetic Diseases, Diseases of Children, with a Section on Predigested Foods, and Appendix on Invalid Cookery. " The directions given are UNIFORMLY JUDICIOUS. . . . May be confidently taken as a RELIABLE GUIDE in the art of feeding the sick." Brit. Med. Journal. " Dr. Burnet'a book will be of great use ... . Deals with BROAD and ACCEPTED VIEWS . . . TREATED With ADMIRABLE SENSE and JUDGMENT." Lancet. LONDON : CHARLES GRIFFIN & GO,, LIMITED, EXETER STREET, STRAND. 96 GUARLS8 GRIFFIN : A Medical Guide to its Care and Management. BY ALBERT WESTLAND. Being Part III. of Dr. WESTLAND'S book, The Wife and Mother, issued separately in response to many requests, with additi( Section upon Physical Exercises. additions to the SECOND EDITION, Thoroughly Revised throughout. In Large Crown 8vo. Cloth. 33. 6d. INFANCY AND INFANT-REARING: A Guide to the Care of Children in Early Life, BY JOHN BENJ. HELLIER, M.D., Surg. to the Hosp. for Women and Children, Leeds ; Lect. on Diseases of Women and Children, Yorkshire College, Leeds; Examiner in the Victoria University. CONTENTS. Normal Growth and Development in the first Two years of Life. Difficulties and Problems of Infant- Rearing. Infant Mortality. Prevention of Infant Mortality. Pure Milk Supply. Infant Feeding. Hygiene of Infancy. Management of Newly Born and Premature Infants. The Significance of Certain Conditions Observed in Infancy. The Work of the Health Visitor. APPENDICES. INDEX. "Every aspect of child life in the first two years is carefully considered." Municipal Journal. "THOROUGHLY PRACTICAL. ... A MINE of information." Public Health. LONDON: CHARLES GRIFFIN & CO., LIMITED, EXETER STREET, STRAND. PRACTICAL MEDICAL HANDBOOKS. 97 GRIFFIN'S "FIRST AID" PUBLICATIONS. FIFTH EDITION, Thoroughly Re.vized. Large Crown Svo. Handsome Cloth. 4. A MANUAL OF AMBULANCE. BY J. SOOTT RIDDELL, M.Y.O., C.M., M.B., M.A., iior Surgeon and Lecturer on Clinical Surgery, Aberdeen Royal Infirmary : Examine) Clinical Surjrery to the University of Edinburgh : Examiner to tne St. Andrew's Ambulance Association. Glasgow, and the St. John Ambulance Association, London. With Numerous Illustrations and 6 Additional Full Page Plates. General Contents. Outlines of Human Anatomy and Physiology The Triangular Bandage and its Uses The Roller Bandage and its Uses Fractures Dislocations and Sprains Haemorrhage Wounds Insensi- bility and Fits Asphyxia and Drowning Suffocation Poisoning Burns, Frost-bite, and Sunstroke Removal of Foreign Bodies from (a) The Eye ; (6) The Ear; (c) The Nose; (d) The Throat; (e) The Tissues Ambulance Transport and Stretcher Drill The After-treatment of Ambulance Patients Organisation and Management of Ambulance Classes Appendix : Ex- amination Papers on First Aid. "A CAPITAL BOOK. . . . The directions are SHORT and CLEAR, and testify to the hand of an able surgeon. "Edin. Afed. Journal. " This little volume seems to ns about as good as it could possibly be. ... Contains practically every piece of information necessary to render First aid. . . . Should find its place in EVERY HODBKHOLD LIBRARY." Daily Chronicle. "So ADMIRABLE is this work, that it ia difficult to imagine how it could be better."- ColHtry Guardian. Ht Sea, THIRD EDITION, Revised. Crown 8vo, Extra. Handsome Cloth. 6s. A MEDICAL AND SURGICAL HELP FOR SHIPMASTERS AND OFFICERS IN THE MERCHANT NAVY. INCLUDING FIRST AID TO THE INJURED. BY WM. JOHNSON SMITH, F.R.C.S., Consulting Surgeon to the Seamen's Hospital, Greenwich, and to the Branch (Seamen's) Hospital. Royal Albert Docks. With 2 Coloured Plates, Numerous I/lustrations, and latest Regulations respecting Medical Stores on Board Ship. *.* The attention of all interested in our Merchant Navy is requested to this exceedingly useful and valuable work. It is needless to say that it is the outcome of many year's PRACTICAL KXHERIKNCE amontrst Seamen. " SOOND, JUDICIOUS, R RALLY HKLHKCL." Tilt Lantti. "It would be difficult to find a Medical and Surgical Guide more clear and comprehensive than Mr. JOHNSON SMITH, whose experience at the GREENWICH HOSPITAL eminently qualifies him for the task. . . . We BKCOMMEND the work to EVERT Shipmaster and Officer. "- Liverpool Journal of Ccmmtru. _____ LONDON : CHARLES GRIFFIN & CO., LIMITED, EXETER STREET. STRAW. 98 CHARLES GR[FFIN 8 "OPEN-AIR" SERIES. "Boys GOULD NOT HAVE A MORE ALLURING INTRODUCTION to Scientific pursuit* thau these charming-looking volumes. "Letter to the Publishers from the Head- master of one of our great Public Schools. SECOND EDITION, Revised. Handsome Cloth. 6s. net. OPEHU STUDIES HI BOTAflY: SKETCHES OF BRITISH WILD FLOWERS IN THEIR HOMES. BY R. LLOYD PRAEGER, B.A., M.R.I.A. Illustrated by Drawings from Nature by S. Rosamond Praeger, and Photographs by R. Welch. GENERAL CONTENTS. A Daisy-Starred Pasture Under the Hawthorne By the River Along the Shingle A Fragrant Hedgerow A Connemara Bog Where the Samphire grows A Flowery Meadow Among the Corn (a Study in Weeds) In the Home of the Alpines A City Rubbish- Heap- Glossary. "A FRESH AND STIMULATING book . . . should take a high place . . . The Illustrations are drawn with much skill." The Times. "BEAUTIFULLY ILLUSTRATED. . . . One of the MOST ACCURATE as well as INTERESTING books of the kind we have seen." Athenaeum. "Redolent with the scent of woodland and meadow." The Standard. With 12 Full-Page Illustrations from Photographs. Cloth. Second Edition, Revised. 8s. 6d. STUDIES I]l GEOLOGY: An Introduction to Geology Out-of-doors. BY GHENVILLE A. J. COLE, F.G.S., M.R.T.A., Professor of Geology in the Royal College of Science for Ireland, and Examiner in the University of London. GENERAL CONTENTS. The Materials of the Earth A Mountain Hollow Down the Valley Along the Shore Across the Plains Dead Volcanoes A Granite Highland The Annals of the Earth The Surrey Hills The Voids of the Mountains. "The FASCINATING ' OPEN-AIR STUDIES ' of PROF. OoLB give the subject a GLOW OF ANIMATION . . . cannot fail to arouse keen interest in geology." Geological Magazine. " A CHARMING BOOK, beautif ally illustrated." Athenaeum. Beautifully Illustrated. With a Frontispiece in Colours, and Numerous Specially Drawn Plates by Charles Whymper. 7s. 6d. OPEMII STUDIES HI SKETCHES OF BRITISH BIRDS IN THEIR HAUNTS. BY CHARLES DIXON. The Spacious Air. The Open Fields and Downs. In the Hedgerows. On Open Heath and Moor. On the Mountains. Amongst the Evergreens. Copse and Woodland. By Stream and Pool. The Sandy Wastes and Mud- flats. Sea-laved Rocks. Birds of the Cities. INDEX. "Enriched with excellent illustrations. A welcome addition to all libraries." West- minster Review. LONDON : CHARLES GRIFFIN & CO., LIMITED, EXETER STREET, STRAND, SCIENTIFIC ROMANCES. 103 SCIENTIFIC ROMANCES. HIS MAJESTY THE KING has most graciously condescended to accept a copy of each of these books. BY JOHN MASTIN, M.A., Sc.D., PH.D., F.S.A.ScoT., F.L.S, F.C.S., F.R.A.S., F.R.M.S., F.B.A. In Crown 8vo. Handsome Cloth. Gilt Lettering. Price 6s. THROUGH THE SUN IN AN AIRSHIP. A THRILLING SCIENTIFIC ROMANCE. " An immense display of resource and knowledge on the part of the author . . . the adventures and discoveries are well worth following." Times Literary Supplement. Mr. Muslin manures to make his tale absorbing at all points, the interest never slackens, his imagination never fails. The suggestions opened out are numerous and appal ing. Some of the discussions are on very deep subjibts, and though they do not lead us "far, and arc hardly as illuminating as the utterances of poets, they are put down soberly and in a convincing manner, which shows that the author takes his work seriously. His scientific knowledge aids him well in his task, and has enabled him to produce a fine novel as attractive to boys us to grown up people." Daily Telegraph. COMPANION VOLUME TO THE ABOVE. In Crown 8vo. Uniform with the above. Price 3s. 6d. THE STOLEN PLANET. SOME PRESS OPINIONS OF THIS. ' Certain it is that the reading of this capital story will prove exciting, for compared with the adventures therein written, the books of Jules Verne and H. G. Wells read like the placid pages of Miss Austen's novels.' Dailj/ Telegraph. ' Mr. Mastin's ingenious and engaging fantasy . . . he is to be commended for resi mi ce, ingenuity, and persistent vigour of narrative." Glasgow Herald. It is a -raphic and exciting tale." Times. THE ADVENTURES OF A SOUTH POLAR EXPEDITION In Crown 8vo. Handsome Cloth. Price 6s. THE IMMORTAL LIGHT. PRESS OPINIONS. " More daring than Poe's ' Narrative of Arthur onlo.i Pym of N'antucket" is Mr. Mastin's romance of Antarctic adventure; for Poe, having introduced a giant 'of the perfect whiteness of the snow," regrets the loss of his crowning chapters. Certainly, if the matter which they contained 'relative to the Pole itself, or at least to regions in i vi TV near proximity,' was as sensational as ' The Immortal Light,' the loss is deplor- able. . . . The story is wildly improbable, but confronts incredulity with a . onsiderable display of scientific detail. A strong religious feeling animates the last part of the book." Athenceum. These three volumes are uniform in size and binding. LONDON: CHARLES GRIFFIN & CO., LIMITED, EXETER STREET, STRAND A BOOK NO FAMILY SHOULD BE WITHOUT. THIRTY-NINTH EDITION. Royal Svo, Handsome Cloth. A DICTIONAEY OF Domestic Medicine and Household Surgery, BY SPENCER THOMSON, M.D., L.R.C.S. (Edin.), J. CHARLES STEELE, M.D., Late of Guy's Hospital, AND GEO. REID, M.D., D.P.H., Medical Officer to the Staffordshire County Council, with a Section on the Maintenance of Health and the Manage- ment of Disease in Warm Climates by JAS. CANTLIE, M.A., M.B., F.R.C.S., Lecturer on Applied Anatomy, Charing Cross Hospital; Surgeon, West-End Hospital for Nervous Diseases; formerly Surgeon, Charing Cross Hospital ; Dean of the College of Medicine, Hong Kong, &c,, &c. ; and an Appendix on the Management of the Sick-room, and many Hints for the Diet and Comfort of Invalids. IRevtsefc anfc brought &own to tbe {present State of * /iReoical Science BY ALBERT WESTLAND, M.A., M.D., AUTHOR OF "THE WIFE AND MOTHER;" "THE CHILD." In its new Form, DR. SPENCER THOMSON'S "DICTIONARY OF DOMESTIC MEDICINE' fully sustains its reputation as the "Representative Book of the Medical Knowledg< and Practice of the Day " applied to Domestic Requirements. The most recent IMPROVEMENTS in the TREATMENT OF THE SICK in APPLIANCES for the RELIEF OF PAIN and in all matters connected with SANITATION, HYGIENE, and the MAIN TENANCE of the GENERAL HEALTH will be found in the Present Issue in clear and fuL detail ; the experience of the Editors in the Spheres of Private Practice, of Hospital Treatment, of Sanitary Supervision, and of Life in the Tropics respectively, combining to render the Dictionary perhaps the most thoroughly practical work of the kind in the English Language. Many new Engravings have been included improved Diagrams oi different parts of the Human Body, and Illustrations of the newest Medical, Surgical, and Sanitary Apparatus. *** All Directions given in such a form as to be readily and safely followed. FROM THE AUTHOR'S PREFATORY ADDRESS. " Without entering upon that difficult ground which correct professional knowledge and educated judgment can alone permit to be safely trodden, there is a wide and extensive field for exertion, and for usefulness, open to the unprofessional, in the kindly offices of a true DOMESTIC MEDICINE, the timely help and solace of a simple HOUSEHOLD SURGERY, or, better still, in the watchful care more gener- ally known as 'SANITARY PRECAUTION,' which tends rather to preserve health than to cure disease. ' The touch of a gentle hand ' will not be less gentle because guided by knowledge, nor will the safe domestic remedies be less anxiously or carefully administered. Life may be saved, suffering may always be alleviated. Even to the resident in the midst of civilisation, the ' KNOWLEDGE IS POWER,' to do good ; to the settler and emigrant it is INVALUABLE." Dr. Thomson has fully succeeded in conveying to the public a vast amount of useful professional knowledge." Dublin Journal of Medical Science. "The amount of useful knowledge conveyed in this work is surprising." Medical Times and Gazette. "WORTH ITS WEIGHT IN GOLD TO FAMILIES AND THK CLERGY." Oxford Herald. LONDON: CHARLES GRIFFIN & CO., LIMITED, EXETER STREET, STRAND. 14 DAY USE RETURN TO DESK FROM WHICH BORROWED This book is due on the Ias?tee^3tffr4fl below, or on the date to which renewed. Renewed books are subject to immediate recall. DEC 15 1971 LD 21-50TO-G/59 (A2845slO)476 General Library University of California Berkeley