College of ^fjpsicians anb burgeons; m'^ P1^ SANITAEY UEXAMINATIONS OP WATEE, AIE, AND FOOD U, iiJ-J-ll, SANITARY EXAMINATIONS OF WATEE, AIE, AND FOOD WITH ONE HUNDRED AND TEN ILLUSTRATIONS By COENELIUS B. FOX, M.D., r.E.C.R Lond. FORMERLY MEDICAL OFFICER OF HEALTH OF EAST, CExNTRAL, AND SOUTH ESSES PHILADELPHIA P. BLAKISTON, SON^, & CO. 1012 WALNUT STREET 1887 F2 3 TO JOHN SIMON, C;B. D.C.L. F.E.S. WHOSE LABOUES IN THE DEVELOPMENT OP THE SCIENCE OF PREVENTIVE OR STATE MEDICINE MERIT THE GRATITUDE OF ALL MEN OP ALL NATIONS THIS VOLUME IS WITH HIS PERMISSION DEDICATED Digitized by the Internet Archive in 2010 with funding from Open Knowledge Commons http://www.archive.org/details/sanitaryexaminat1887foxc PEEFACE TO SECOND EDITION The universal recognition of the utility of this work, not only by Medical Ofiicers of Health, for whose assistance it was written, but also amongst that portion of the public which is interested in the promotion of Sanitary Science, has rendered the preparation of a new Edition needful. My retirement from the public health service, in conse- quence of an inabihty to sacrifice principle to expedi- ency, is not in one sense, perhaps, to be regretted, since the enforced leisure has afforded me the opportunity of studying those Biological Methods for the examination of Water and Air that have been introduced of late years, and which are considered by our German and French confreres to be as important as their chemical analysis. Great improvements have also been recently effected in the examination of Milk. My thanks are due to those health officers who have. Vlll PKEFACE TO SECOND EDITION in response to my invitation, sent me memoranda for the improvement of this Handbook. To Drs. Shea, Ashby, P. Frankland, J. W. Moore, Bond, Mill, and to the late Prof. Eipley Nichols, I am especially indebted for much valuable information. C. B. F. Ilfeacombe, Devonshire, September 1886. PEEFACE TO FIKST EDITION The demand for a third edition of my brochure on " Water Analysis," affords me an opportunity of offering to the public the results of an increased and more extended experience. The additions are so great as to compel me to re-write nearly all that I have pre^dously published on the subject. The many kind appreciative comments that have been made on it by the scientific world, and especially by that section of it that is engaged in the public health service of the country, coupled with the suggestions of friends, have led me to incorporate with my essay on "Water Analysis " sections on " Examinations of Air and Food." I trust that none of my readers will imagine that I have the presumption to place myself forward as a teacher of the Medical Officers of Health of the country. I wish rather to offer suggestions and hints, tliat, I am sure, will be helpful to those who have not plodded as I have, along long, tedious, and tortuous paths for many years, at the sacrifice of much time and labour, because I could not find a short cut. It does not follow that because there is "no royal road to learning," that the road which we X PREFACE TO FIRST EDITION have to traverse should be beset with all kinds of un- necessary obstacles and difficulties. The objects which I have kept steadily in view in writing the following pages have been : — 1. To avoid a consideration of these three subjects solely after the manner of an analyst who mechanically deals with chemical operations and arithmetical calcula- tions, but to treat them as a physician who studies them in connection with health and disease. 2. To render such detaiLs respecting examinations of water, air, and food, as fall within the province of the Medical Officer of Health, so free from technicalities and all cloudy and chaotic surroundings, as to enable any one who possesses the average chemical knowledge of a physician to teach himself by the aid of this vacle mecum of the health officer. Some of the information contained in this book treating of the examination of water and milk, may also be found in other analytical works, amongst which may be mentioned Mr. Wanklyn's " Water Analysis " and " MHk Analysis." It affords me much pleasure to acknowledge with gratitude the assistance rendered to me by scientific men throughout the country, amongst whom may be mentioned Drs. Attfield, Barlett, Brown, Cameron, F. de Chaumont, Hill, Shea, Thorne, Tidy, and Messrs. Dixon, Slater, Thomas, etc. Chelmsford, May 1878. CONTENTS PAGE Preface to Second Edition . . . . vii Preface to First Edition . . . . ix Introductory Observations .... 1 SECTION I.— SANITAEY EXAMINATION OF A DEINKING WATEE CHAPTEE I The Wholesomeness of a Water CHAPTEE II The Determination of the Amount and Nature of THE Organic Matter . . . .13 1. The SmeU of a Water . . . .14; 2. The " Keeping Powers " of a Water .' . 19 3. The Colour Test . . . .20 4. Heisch's Test . . . . . • 24 5. The Zymotic or Microzyme Test . . 25 Xll CONTENTS PAGE 6. The Oxygen or Forchammer Permanganate of Potash Process . . . .26 A. Qualitative Examination . . .26 B. Quantitative Examination . . .26 Drs. Letheby and Tidy's Process . .28 Drs. Woods' and F. de Chaumont's Process 33 An Improved Process . . .38 7. The WanMyn, Chapman, and Smith Process . 39 8. The Frankland and Armstrong Process . .53 Table exhibiting different classes of Waters . 58 A Comparison between the Residts furnished by the three last-named Processes . .63 Table of Comparison . . . .68 Value of the Frankland and Armstrong, Wan- klyn, Chapman, and Smith, and the Quanti- tative Forchammer Permanganate of Potash Processes in the Detection of Dangerous Pollutions . . . . .71 9. Koch's Biological Method . . .74 10. The Estimation of Dissolved Oxygen . . 86 CHAPTEE III The Determination of the Mineral Products re- sulting FROM Changes in the Animal Organic Matter . . . . . .91 1. Ammonia . . . . .91 2. Nitrogen as Nitrates and Nitrites . .95 A. QuaKtative Examination — the Horsley Test 106 B. Quantitative Examination . . .111 Modification of Thorp's Process . .114 CONTENTS XIU CHAPTEE IV PAGE The Determination op the Amount op Solid Resi- due, ITS Appearance Before, During, and Apter Ignition, and the Loss op Volatile Matters thereby occasioned . . . .124 A. The Amount of Solid Residue or Saline Matters 124 B. The Appearance of the Solid Residue Before, Diu-ing, and After Ignition . . .128 Table of Illustration . . .130 C. The Amount of Volatile Matters burnt off by Ignition . . . . .132 CHAPTEE V The Determination op the Amount op Chlorine . 135 CHAPTEE VI The Determination op the Hardness . .139 CHAPTEE VII The Determination op the Amount op Magnesia, Sulphates, and Phosphates . . .144 A. Magnesia — Sulphate, Carbonate, and Nitrate . 145 B. Sulphates of Lime, Magnesia, and Soda as An- hydrous Sulphiuric Acid . . .147 C. Phosphates . . . . .150 CHAPTEE VIII The Determination of Poisonous Metals . - . 154 xiv CONTENTS CHAPTEE IX PAGE MiCEOscopic Examination of a Water . .161 CHAPTEE X The Collection of Samples of Water for Analysis 170 CHAPTEE XI Time occupied in performing an Analysis . .172 CHAPTEE XII Entry of Analysis in Note and Record Books . 175 CHAPTEE XIII Mistakes of Water Analysts, and how to avoid THEM ...... 177 CHAPTEE XIV Useful Memoranda for Medical Officers op Health WHEN performing- WaTER ANALYSIS . .185 CHAPTEE XY Formation of Opinion and Preparation of Report AS TO Sample of Water submitted to Analysis . 188 CONTENTS XV PAGE A. Summary of Data on which to base an Opinion . 195 B. Valuation Tables and District Standards . 196 C. Diagnosis and Formation of an Opinion . 200 Diagnosis of a Peaty Water . . .205 Diagnosis of Pollution by Urine, or by Slop and Sink Water . . . .209 Diagnosis of Pollution by contents of Cesspools and Sewers . . . .210 D. Preparation of Report . . . .212 CHAPTER XVI Concluding Eemarks on Section I. . . .215 Recipes op Standard Solutions, etc. . .216 SECTION II.— SANITAEY EXAMINATION OF AIE CHAPTER XYII PAGE The Pueity of Aie . . . . .221 PART I Different Kinds op Impurities . . .231 CHAPTER XYIII Organic Matter . . . . .232 XVI CONTENTS CHAPTEE XIX PAGE Oxides of Caebon . . . . .240 A. Carbonic Acid ..... 240 B. Carbonic Oxide . . . .247 CHAPTEE XX Putrefactive Processes, Sewage Emanations, and EXCREMENTAL FiLTH .... 254 CHAPTEE XXI Poisonous Gases and Injurious Vapours . .257 CHAPTEE XXII Suspended Animal, Vegetable, and Metallic, as WELL AS Mineral Impurities . . . 258 CHAPTEE XXIII Emanations from Ground having Damp and Pilthy Subsoil — Subsoil Air, Churchyard Air, Marsh Air . . . . . . . 264 CHAPTEE XXIV The Deleterious Effects on Health of the Air of our Houses ...... 270 CONTENTS XVll PAET II PAGE The Detection and Estimation of the Amount of THE most Important Impurities found in the Air . . . . . . .291 DIRECT METHOD CHAPTEE XXV Modes of Observing Solid Bodies in the Air, and OF Separating them for Examination . .292 CHAPTEE XXVI Microscopical Examination of the Dust of the Air 301 CHAPTEE XXVII The Chemical Examination of Air . . .310 A. Organic Matter . . . . 312 B. Carbonic Acid . . . , .328 CHAPTEE XXVIII The Biological Examination of Air . . . 340 CHAPTEE XXIX Metallic Poisons : — Arsenic, Copper, and Lead . 343 & XVIU CONTENTS INDIRECT METHOD CHAP TEE XXX PAGE Estimation of Ozone and other Aie Purifiers . 349 PAET III Sketch of Relation between certain Meteorolo- gical Variations in the Condition op the Air, and states of health and disease . .358 CHAPTEK XXXI 1. — The Influence of Differences of Temperature, Solar Radiation, Moisture, and Barometric Pressure of the Air, Direction of the Wind, etc., on Health ..... 362 A. The Temperature of the Air = Air Warmth . 362 B. The Solar Radiation .... 367 C. The Hygrometric State of the Air . . 369 D. The Pressure of the Air . . .374 E. The Direction of the Wind . . .378 CHAPTEE XXXII -The Meteorological Conditions which appear to favour or retard the development of cer- TAIN Diseases ..... 380 1. Siu:gical Fever after Operations . . .381 2. Smallpox . . . . .383 CONTENTS XIX PAGE 3. Measles .... 384 4. Whooping-Cough 386 5. Scarlet Fever .... 387 6. Fever ..... 389 7. DiarrhcBa, Dysentery, and Cholera 391 8. Bronchitis, Pneumonia, and Asthma 396 9. Phthisis Pulmonalis 398 10. Diphtheria .... 398 11. Hydrophobia .... 399 12. Erysipelas and Puerperal Fever 399 13. Insanity .... 400 14. Eheumatism .... 401 Mortality at Different Ages and of each Sex . 402-405 PAET IV Mode of Observing the Meteorological States and Variations in the Condition of the Air . 406 CHAPTEE XXXIII 1. — The Atmospheric Pressure 407 CHAPTEE XXXIV 2. — The Temperature of the Air 411 CHAPTEE XXXV 3. — The Hygrometric Condition op the Air 422 XX CONTENTS CHAPTEK XXXVI PAGE 4. — The Dikection and Strength of the Wind . 430 CHAPTEE XXXVII 5. — The Electrical State of the Air . . 434 Kegistration of Meteorological Observations . . 439 SECTION III.— SANITAEY EXAMINATION OF FOOD CHAPTEE XXXVIII PAGE The Purity of Food . . . . . 443 CHAPTEE XXXIX Inspection and Examination of any Animal in- tended FOR THE Food of Man . . . 446 CHAPTEE XL Inspection and Examination op Carcases op Ani- mals, Meat and Flesh Exposed for Sale, or Deposited for the Purpose of Sale, or of Pre- paration for Sale, and intended for the Food OF Man . . . . . .449 CONTENTS XXI PAGE Characters of Good and Bad Meat . . . 450 The Prevalent Diseases of Stock in relation to the Supply of Meat for Human Food . . .454 1. Contagious Fevers . . . .454 2. Anthracic and Anthracoid Diseases, etc. . 458 Arguments against the Employment of Diseased Meat . 463 Arguments in favour of the Employment of Diseased Meat . . . . . .464 3. Parasitic Diseases .... 468 Immature Veal and Lamb . •. . .476 Poisonous Pork, Ham, Sausages, etc. . . .477 CHAPTEE XLI Ihspection and Examination of Poultey, Game, etc. 478 CHAPTEE XLII Inspection and Examination of Fish . . 480 CHAPTEE XLIII Meat of Poisoned Animals . • • • • 482 CHAPTEE XLIV Destruction op Condemned Flesh . . . 484 CHAPTEE XLV Inspection and Examination of Fruit and Vege- tables ...... 486 XXll CONTENTS CHAPTEE XLVI PAGE Turned Provisions ..... 488 CHAPTEE XLVII Inspection and Examination of Corn . . 489 CHAPTEE XLVIII Inspection and Examination op Flour . .493 Chemical Examination . . . . 495 MicroscoiDic Examination . . . .499 CHAPTEE XLIX Inspection and Examination of Bread . .508 Microscopic Examination , . . .509 Adulterations of Bread . . . .509 Chemical Examination . . . .513 CHAPTEE L Inspection and Examination op Milk . . 520 Microscoi^ic Appearance . . . .522 Physical Pecnliarities . . . . .523 Chemical Examination . . . .525 Milk supplied by, and tainted by, Diseased Animals . 535 Milk contaminated by water polluted with Organic Impurities . . . . .544 CONTENTS xxiii APPENDIX PAGE Distilled Water and Chemicals . . . 547 List of AiDparatus requisite . . . .548 Rules for Interchange of Different Expressions of Results of Analysis . . . . .550 Rules for Conversion of Degrees of Scales of Ther- mometers . . . . .551 Metrical Weights and Measures . . .551 Index ....... 553 INTEODUCTORY OBSERVATIONS The elementary principles on which the greater part of the work of the Medical OSicer of Health is based^ may be truly said to be the prevention of the pollution of Water and of Air with filth and its products, and the prevention of the consumption of articles of Food deleteri- ous to health. Pure Water, pure Air, and good, wholesome, unadul- terated Food constitute the pillars which form the trijDod on which rests the " mens sana in corpore sano." My ideal of a Medical Officer of Health is that of a physician who is thoroughly conversant with every ques- tion affecting Public Health, and who is able to analyze quantitatively water, air, and food ; and is so well versed in analytical work as to be able to take his oath in a court of justice respecting any matter requiring the assistance of a scientific expert in state medicine. Such a man should be debarred from private practice, and placed over a large area with definite boundaries, such as a county or riding. His appointment should be perma- nent, so that he may fearlessly and conscientiously per- form his duty. Every medical practitioner in his district should act towards him in the capacity of an assistant. The Medical Officer of Health should in fact be the Head Centre of all Public Health affairs in each county. B 2 INTRODUCTORY OBSERVATIONS First, as to Water. — The examination of drinking waters forms a very important portion of the duty of those who engage in a crusade against preventable disease. A health officer should not only be prepared to answer such a question as, "Does a w^ater contain a deleterious amount of organic matter ?" but should be able to reply to such interrogations as, " Is this water wholesome and good?" "Which of several specified wells furnishes the purest water ?" etc. Some are disposed to think that it is unadvisable for a Medical Officer of Health to analyze water. The list of his duties, as laid down by the Local Government Board, certainly contains no order that he should act as a water analyst. The latest Adulteration Acts (Food and Drugs Act of 1875, and the Amended Act of 1879) expressly excludes water from its provisions. Few, I should presume, would hold that water is not in some sense a food (much more so than either mustard or pickles) ; and that, having regard to the derivation of the word "adulterate," the sewage and water supplied by some wells could not strictly be considered to be "a change to another " (the exact meaning of the word) of an article of daily consumption, of a very serious character. A Medical Officer of Health who can promptly give an authoritative opinion as to the quality of a water is much more helpful to the Sanitary Authorities with which he may be connected, than one wdio is unable so to do. Continually cases arise, in the working of a large district, where a Sanitary Authority requires an immediate deci- sion as to the quahty of a water, in order that steps may be taken with the least possible delay in the prevention of the extension of a disease. If, as is customary in some places, samples of water are sent to professional analysts living at a distance, great loss of time is generally experi- enced, and the analyses of waters yield illusory results INTRODUCTORY OBSERVATIONS 6 in consequence of being examined in a stale instead of in a fresh condition. I Imxe often known a month or more to elapse before the report is received, when, frequently, the opportunity for acting on the opinion expressed has passed away. Moreover, a Medical Officer of Health requires, for his own guidance in tracing out the causes of diseases, and in taking measures to stop their spread, to ascertain expeditiously and with precision the state of waters. Secondly, as to Air. — What can be more important than the establishment of some rules of practice as to the purity of the air of our houses and public buildings ? There can be no question but that there is a distinct causative relation between consumption and re-breathed air, between the condition of the air in unventilated and crowded dwellings and the prevalence of lung affections. An enormous field is afforded to the health officer in the study of the subject of the defilement of the air by metallic, mineral, and other visible impurities, with a %dew to the discovery of some means whereby the condition of those classes who have to earn their daily bread by working at such unwholesome avocations as button manufacture, stone masonry, the cotton, wool, and silk industries, etc., may be ameliorated. Thirdly, as to Food. — The attention of the Medical Officer of Health should undoubtedly be restricted in his analytical examinations to the necessaries of life, and to those substances that are apt to be injurious in them- selves, or are liable to be adulterated with substances deleterious to health. Professional analysts, distinct from Medical Officers of Health, there always must be. On these officials devolves the duty of analysing foods, etc., which contain fraudulent but harmless admixtures, such, for example, as the compound of mustard, and of cocoa, with starch — an innocuous diluent, the mixture 4 INTRODUCTORY OBSERVATIONS of sardines and sprats with anchovies, and of salt with gelatine to increase its weight in the scales, etc. The duties of the Medical Officer of Health, as laid down by the Legislature, all rest on the assumption that he is the judge on all subjects relating to iniUic health. It is of course difficult to draw a hard and fast line in this matter, as in every other in this world. " 1st Duty. — He shall inform himself, as far as prac- ticable, respecting all influences affecting or threatening to affect injuriously the public health within the district. " 2cl Duty. — He shall inquire into, and ascertain by such means as are at his disposal, the causes, origm, and distribution of diseases within the district, and ascertain to what extent the same have depended on conditions capable of removal or mitigation. " 3cZ Duty. — He shall, by inspection of the district, both systematically at certain periods, and at intervals as occasion may require, keep himself informed of the con- ditions injurious to health existing therein. " Wi Duty. — In any case in which it may appear to Mm to be necessary or advisable, or in which he shall be so directed by the Sanitary Authority, he shall himself inspect and examine any animal, carcase, meat, poultry, game, flesh, fish, fruit, vegetables, corn, bread, or flour, exposed for sale, or deposited for the purpose of sale, or of preparation for sale, and intended for the food of man, which is deemed to be diseased, or unsound, or unwhole- some, or unfi.t for the food of man ; and if he finds that such animal or article is diseased, or unsound, or unwhole- some, or unfit for the food of man, he shall give such directions as may be necessary for causing the same to be seized, taken, and carried away, in order to be dealt with by a justice, according to the pro"\dsions of the statutes applicable to the case." The First Duty alone is comprehensive enough to INTEODUCTOEY OBSEEVATIONS 5 include the consideration of each of the three subjects treated of in the following pages, and even more. As Medical Officers of Health are often at present inundated with analytical work by those who are simply curious as to whether their drinking water is or is not good, or as to the reason why it does not make good tea, or as to why their sugar turns their tea of a black colour, or as to whether their wall-papers contain arsenic, or as to why their brandy and water assumes sometimes an inky hue, it is a great protection to the Medical Officer of Health if he refers all applicants to the Sanitary Author- ity of the district for an order, with the previous under- standing, arrived at with the Sanitary Authority, that it will not give him any instructions to analyze at the public expense, unless evidence is placed before it of a nature calculated to show that the substance respecting which the request is made has been or is likely to be deleterious to health, and that the applicant cannot afford to pay for the analysis out of his or her own pocket. As all chemical examinations to be exact must be quantitative, and as all inaccurate examinations are of little worth, and as, moreover, the quantitative analysis of a substance is not laid down as one of the duties of a Medical Officer of Health by the Government, it follows as a matter of logical sequence, that all quantitative analy- tical work conducted for a Sanitary Authority and for the public should be paid for. Work performed gratuitously is rarely valued. The progress of a knowledge of Preventive Medicine is exceedingly slow. The Medical Officer of Health, who is the schoolmaster of his district as to sanitary matters, must necessarily find his work of a very uphill character. He is continually regarded as an irreverent individual, who is wicked enough to interfere with the purposes and designs of the Almighty. Thousands are still to be found 6 INTEODUCTOKY OBSERVATIONS who believe that if a water is bright and clear, and not unpleasant to the taste, it must be good; whilst it has been proved, over and over again, that such a water may be polluted with unspeakable filth, and that an excessive brilliancy of a water is a suspicious sign. There can be no question, however, but that the ele- ments of sanitary science are slowly and surely influ- encing the people of this and of other countries for good. Such cases as that of the servant who, coming from an obscure village near the Dartmoor, objected to the pure water of a distant town where she was in service, on the ground of its being devoid of either taste or smell, are becoming rare. SECTION I SANITAEY EXAMINATION OF A DRINKING WATER CHAPTEE 1 THE WHOLESOilEXESS OF A WATEK PuEE spring waters, devoid of all metallic impurities, are undoubtedly the most wholesome waters for drinking purposes. Pure shallow and artesian well waters occupy a second place. The sahne waters furnished by some artesian wells, and the rain that descends in the country far away from towns and cities, occupy jointly a third position in order of merit ; and lastly come the waters of streams and rivulets, the majority of which contain more or less filth, and in times of hesivj rains, soil and mineral debris of every description. All will readily understand the reason that spring water should be placed first, and river water last in the order of wholesomeness, but the motive for assigning to highly saline artesian well water and rain water a situation inferior to both spring, shallow and deep well waters is perhaps not so obvious. Artesian well waters frequently contain an excess of saline matters (vick page 127). Eain water possesses an infinitesimal amount of saline substances, and is almost entirely devoid of lime — a substance which is so important in building up the bony tissues of young animals. I am aware that some few eminent men think that young creatures solely derive the lime which they require from their food-^ (vide, for example, the CAidence ^ One pound of flour contains only IJ grain of lime, and that in a form which is associated with the more insoluble part of the grain. 10 THE WHOLESOMENESS OF A WATER of Dr. Lyon Playfair in the Sixth Eeport of the Eivers Pollution Commissioners, page 189). Those who entertain this view consider, I believe, that water simply acts as a diluent or solvent in nutrition. I have no room here to combat this opinion, but can simply give it as my own that the young animal supplies the wants of its system for lime from every available source. Many towns in England and Scotland are supplied by waters collected from the surface of uncultivated land in lakes and reservoirs. These " upland surface waters " are often insufficiently aerated, and contain an excess of peaty and other vegetable matter which renders them unpalatable, and sometimes gives them a slightly bitter taste. In consequence of their softness, however, they are very useful for domestic and manufacturing purposes. It is almost impossible to define a wholesome water ; but here are two examples of most wholesome spring waters : — Name and Description of tlie Sample of Water. Grains per Gallon. Part per Million = Milligramme per Litre. Total Hard- ness. -o a |1 igen rates d ites. Albumi- noid Ammonia. Spring supplying vil- o ^1 < P lage of Woodham Walter, Essex 21- 2-4 •02 nil. •00 •01 6 Spring near Drew- steignton, Dart- moor, Devon 14- 1-6 •03 nil. •02 •01 8 N.B.— No metals in either water. It may be useful to give examples of the composition of good shallow well and good artesian well waters and pure rain water : — THE WHOLESOMENESS OF A WATER 11 Part per Million Total Name and Description of the Sample of water. Grains per Gallon. = Milligramme per Litre. Hard- ness. 3 itrogen titrates and i trites. .4, g III Ed Good shallow well 012 °^ ^c» » p < ^ ^ P water. Depth 25 feet 30- 7- •01 •2 •01 •05 13 Good Artesian well water. Depth 300 feet 85-4 27-1 •02 nil. •74 ■03 5 Good Artesian well water. Depth 175 feet lOG-4 37-7 •04 nil. y ti^si ^ Pure rain water col- if. lected in open Jr LtBRj i.'R^ country- 1- •6 •01 nil.V, •45 ^0^"' »^Mpj . Shallow well water. Artesian well water. Rain tfater. :4^t the temperature of the air. Some allow the permanganate to act for a few minutes, and others for hours. Some who employ this test prepare a solution by dissolving two grains of the pure salt in 10-|- oz. of distilled water. Ten minims of this solution is said to yield ^qqq of a grain of oxygen. The quantity of the solution required for a known quantity of the water is divided by 10, the result giving the number of thousandths of a grain of oxygen consumed. The calculation is as follows : — Well water labelled A B, 2 ounces = -^q- of 70,000 grains (1 gallon) taken for examination. 22 minims of Sol. Permanganate PotasL. required to give a decided j^ink colour. 22 X 80 = 1760 minims necessary for 1 gallon. 1760-^10 = 176 which are thousandths of a grain of oxygen. Result. — '176 of a grain of oxygen per gallon. The three best known quantitative processes are : — (1) that for many years practised by the late Dr. Letheby, and now employed by Dr. Tidy ; (2) that adopted by Drs. Woods and F. de Chaumont ; and (3) Prof Kubel's variety of the permanganate of potash process. The first mentioned is preferable to*ither of the others ; the second is employed much by army surgeons, being taught at Netley ; whilst the third, which is conducted at the boiling point, is open to the suspicion that loss of organic matter by volatilization with the escaping steam is inevitable. The higher figures yielded by Kubel's method are probably due to the increased length of IT 28 THE DETERMINATION OF THE AMOUNT a!!^ time during which the permanganate of potash is .allowed to act. Drs. Lethehy and Ticlys Permanganate of Potash Quantitative Process of Water Analysis} The following mo|^ of employing the Forchammer or oxygen process has been almost exclusively practised by Dr. Letheby and his successor. Before commencing the analysis the following solutions should be ready : — 1. Dilute Sulphuric Acid. — 1 part of pure strong sulphuric acid with 3 parts of distilled water. 2. Solution of Potassic Permanganate. — 2 grains in 1000 septems (x^th of a gallon) of water. (20 septems or '04 grain of potassic permanganate, contain '01 of available oxygen.) 3. Solution Potassic Iodide. — 1 part of potassic iodide in 1 of water. 4. Solution of Sodic Hyposulphite. — 5 "4 grains in 1000 septems (x^th of a gallon) of water. As a solution of this salt quickly decomposes, it is necessary to make a fresh one A'ery frequently. 5. Solution of Starch. — 100 septems of distilled water to be placed in a flask, and 10 grains of powdered starch having been added, the mixture should be boiled and filtered. Two glass flasks, each of abteut 2 oz. capacity, having ^ I am indebted in the description of this process which follows, to an exhaustive paper entitled "The Processes for determining the Organic Purity of Potable Waters," by Dr. Tidy, in Journal of Chemical Society, vol. XXXV. 1879, p. 46. It contains an account of a mode of conducting the process which is an improvement on that shown to me some time previoiis to its publication, in Dr. Tidy's laboratory, by his assistant in his absence. NATURE OF THE ORGANIC MATTER 29 been thoroughly cleansed^ 500 septems (2\)th part of a gallon) of distilled water" are ponred into each. Take ^ther flasks of the same dimensions, and pour the si Quantity of the water to be epamined into each. La each flask thus )f a . DistilH!iii» . (1 hour.) „ „ ... (3 hours.) Water under examination . (1 hour.) • (3 hours.) Any number of waters can be* commenced at the same time, one set of the distilled water series being sufficient as a blank experiment for all. (a) 20 septems of the dilute sulphuric ^la should be added by the help of a pipette, graduated into septems, to the contents of each of the four flasks. (&) 2 septems of the permanganate of potash solution should then be^un, by the aid of another similar pipette, into each of the four flasks. ISTote the exact time of this addition of the solution of potash permanganate, and place the four flasks in a dark cupboard. If the pink colour produced in the water under examination disappears within the prescribed time of 1 hour or 3 hours, which rarely happens, a second, and if needful, a third or even fourth dose yf 20 septems should be added, until the colour is permanent. The change on adding perman- ganate of potash may be thus represented : — Mii208S:2 + 3H2SO^ = 2MnS04 + K2S0^ + 3H2O + 50. The oxygen consumed by the constituents of the water is to be estimated at the end of 1 hour in one of the flasks containing the water under examination, and in one of the distilled water flasks ; and at the end of 3 30 THE DETEEMIXATION OF THE AMOUNT AXD IIOIV liours in the other flask containing the water under amination, and the other distilled water flask. At the expiration of the hour, it is first necessary, sequence of the changes to whicli the solution of t sodic hyposulphite is subject, tiQ. ascertain its exact valu by means of a blank experiment with. rthe contents of the " distilled water flask (1 hour)." It is thus effected : — Add 2 drops of the potassic iodide solution to the " distilled water (1 hour)," when the colour of a very weak solution of iodine is produced, which sub- stance is in fact hberated frcfei the potassic iodide, the quantity set free teing Ae^endent on the amount of potash permanganate remaining in the water undecom])osed — MNgOsKg^OKI + 8H,S0^ = 2MnS0^ + 6K,S0^ + SH^O + 51,. The quantity of iodine liberated is thus determined. The sodic hyposulphite solution is placed in a burette graduated into 100 septems. Eun it septem by septem into the flask labelled " distilled water ^1 hour)," until the yellow colour of the iodine very nearly disappears. Then add a few drops of the starch solution, when a beautiful blue colour is produced from the formation of the iodide of starch, and resume the dropping of the hyposulphite solution into the flask i^ntil the exact spot is reached, when the blue colour disappears. 1'hat the exact mark has not been overshot must be proved by the addition of a drop of the solutiofl of the per- manganate of potash, which immediately restores the blue colour. A similar return of colour is observed after the flask has been ai^pding exposed' to the air for a few minutes. Eead offmei-amount of hyposulphite used. Eeaction of the hyposulphite solution on the free iodine — SS.XaoOg + lo = 2NaI + NagS^Og. NATURE OF THE OEGANIC MATTER ol Immediately refill the burette with the sodic hypo- sulphite solution thus standardized and examine the _. ^ contents of flask labelled " Water under examination (17^^ hour)," in precisely the same manner noting the amount of sodic hyposulphite solution employed. At the end of 3 hours the contents of flasks labelled " Distilled water (3 hours) " and "^Water under examination (3 hours)," should be examined in the same way.^ Experiment. — Suppose the usual amount of 2 septems of solution permanganate potash has been added in each case. At the end of 1 hour. Sej^tems of sodic liyposulpliite solution required to com- bine witli tlie free I in the distilled water . .50 Septems of sodic hj-posulpliite solution requii-ed to com- bine with, the free I in the water under examina- tion 40 . ' At the end of 3 hours. Septems of sodic hyposulphite solution rec^uired to com- bine with the free I in the distilled water . .50 SejDtems of sodic hyposulphite solution recj^uired to com- bine with the free I in water under examination . 30 In each case 50 septems of the sodic hyposulphite solution were employed in the blank experiment with ^ Prof. Mallet of the Uuirersity of Yirginia has suggested in his Report ou the Results of a Supplementary Investigation, made by the dnection of the National Board of Health, the three following improve- ments in this process : — "(1) The time daring which the permanganate of potash is allowed to act should be increased to at least 12, better 24 hours, severed determinations (on different samples set aside at the same time) being made at such intermediate intervals as 1, 3, 6, 9, and 12 hours, in order to trace the progi'ess of the oxidation ; (2) Instead of using a fixed amount of permanganate of potash at first, and adding a second or third 3harge only when the former has been completely reduced, there should be present a constant excess all through the process ; (3) It is desirable hat the process be carried on at a pretty nearly fixed temperature of, say 3S° F." (For experiments on the varying extent of action of permanganate '.pon organic matter in water at diflerent temperatures, vide Bcriclit VDeutscli, Chem. Gcscllsch., 14, 1015.) 32 THE DETERMINATION OF THE AMOUNT AND distilled water, and this amount is equivalent to '01 of ^^^oxygen. ^ At the end of 1 hour, ^ . .^ 40 septems of the sodic hyposulphite solution being used in •'iMj the water under examination, the quantity of oxygen con- sumed may be thus found : — Septems of Sodic Hypo. Septems of Sodic Hypo. Sol. required by dis- Sol. required by water tilled water. under examination. Oxygen. (A) 50 : 40 ; : "Ol •01 50 ) -400 ( -008 400 Oxygen equivalent Oxygen equivalent to 50 septems. to 40 septems. (B) -01 - -008 = -002 the quantity of oxygen required to oxidize the organic and other matters in 500 septems of water. (C) '002 X 20 = '04 oxygen required to oxidize organic matters, etc., in 10,000 septems or 1 gallon of water. In exactly the same manner the oxj^gen consumed after 3 hours may be calculated. The calculation may be simplified thus : — Let X = number of septems of the solution sodic hyposulphite used in the distilled water. Let Y = number of septems used in water examined. If 20 septems of the solution of potash permanganate have been employed — X-Yx-20 ^ . , .,. :rp — Oxygen required to oxidize organic matter in 1 X gallon of water. If 40 septems have been necessary — Xx2-Yx-20 ■ Ai. . ^^ = = Oxygen required by 1 gallon. If 60 septems have been added — Xx3-Yx-20^ .. — = Oxygen required. NATURE OF THE ORGANIC MATTER Drs. Frankland and Tidy have suggested'^ the following Scale of Classification : — Rules. Upland Surface Water. Water other than Upland Surface. Class 1. Great organic purity. Water absorbing from permangan- ate of potash not more than "07 grain of oxygen per gallon. Not more than "035 grain per gallon. Class 2. Medium iiurity. From '07 to •21 grain per gallon. From '035 to "1 grain per gallon. Class 3. Doubtful purity. Absorbing from '21 to '28 grain per gallon. From "1 to 'IS grain per gallon. Class 4. Imjmre. Absorbing more than -28 grain per gallon. More than '15 grain per gallon. Dr. Tidy evidently leans to the opinion that the putrescent easily oxidized animal organic matters are oxi- dized within the first hour, whilst the oxidation of vegetable organic matter does not begin until after the second hour. Prof. Mallet and his assistants, however, found that the proportionate consumption of oxygen within the first liour is rather greater for those waters containing vegetable than for those containing animal matter. My own experience shows that those matters which are in an actively putre- scent condition, be they vegetable {e.g. decomposing starch), or be they animal, are more rapidly acted on by the per- manganate of potash than those which are in a com- paratively fresh state. Brs. Woods' and F. de Chaumont's Permanganate of Potash Process. 1. Introduce into a flask 250 c. c. of the water to be Estimation examined, and add to it about 5 c. c. of dilute sulphuric °^*°*^^\jjg ^ Dr. Frankland on Water Analysis for Sanitary Fxhrposes. D matter. 34 THE DETERMINATION OF THE AMOUNT AND acid (1 part of the strong pure acid to 10 parts of dis- tilled water). Drop into the acidified water a solution of the permanganate of potash ("395 gramme of the salt dissolved in one litre of distilled water : 1 c. c. yields •! of a milligramme of oxygen in presence of acid) sufficient to make the water pink ; then warm this pink mixture up to 140° Y., taking care to add more permanganate of potash solution should the colour disappear during heating. When this temperature is reached, take away the lamp, and continue adding the permanganate of potash solution, until a pink colour is established that is per- manent for ten minutes. Note the number of cub. cents. of permanganate of potash solution employed, and record them as required for total oxidizable matter. ff^oxitoa°bie ^- Take another 250 c. c. of the same water, and add organic to it 5 c. c, of dilutc sulphuric acid. Boil the acidified 'water for twenty minutes. Allow it to cool down to 140° F., and then test with permanganate of potash solution as before. Record the amount used as required for oxidizable organic matter only. 3. The difference between the amount of perman- acid. ganate of potash solution needed in the first and second operations represents the quantity required for nitrous acid only. Examples. Total Oxidizahle Matter. 250 c. c. or ^ litre of sample of water employed. No, 1. — 4"2 c. c. of permanganate of potash solution required: — 4'2 x 4= 16'8 c. c. per litre. 16-8 X -0001 (co-efficient for oxygen) = -00168 or 1-68 milligramme of oxygen for total oxidizahle matter. Oxidizable Organic Matter. 250 c. c. or ^ litre of sample of water employed. Estimation 3f nitrous NATURE OF THE OEGANIC MATTER • 35 'No. 2. — 3 "6 c. c. of permanganate of potash solution required : — 3-6 x 4 = 14'4 c. c. per litre. 14-4 X -0001 (co-efficient for oxygen) = '00144 or 1-44 milligramme of oxygen for the oxidizdble organic matter. Nitrous Acid. No. 3. — The difference between the amount of total oxidizable matter (1*68 milligramme per litre) and that of the organic oxygen (1*44 milligramme per litre) is "24 milligramme per litre of oxygen. •24 X 2 '8 7 5 (co-efficient to convert oxygen into nitrous acid) = "6 9 milligramme of nitrous acid per litre. Total Oxygen. | Organic Oxygen. | Nitrous Acid Milligramme per Litre. 1-68. I 1-44. I -69. The permanent pink colour established by adding the ]3ermanganate of potash solution to the sample of water must be the lightest tint distinctly visible. As about •6 c. c. of the solution will give a red or pink colour to a litre of pure water, a correction for colour must be made when great accuracy is required. This correction would amount to "06 of a milligramme of oxygen in both the total and the organic oxygen. Dr. "Woods' investiga- tions, on which this process is based, may be found in the Journal of the Chemical Society for 1861. In 1868-69, Dr. F. de Chaumont made other observa- tions which improved this process, by showing : — (1) that when water polluted with sewage was boiled with acid, no change in its behaviour with permanganate of potash was produced ; (2) that if the organic matter in it was mingled with nitrites, all of the nitrous acid contained in them could be boiled away in twenty minutes without material loss in the operation ; and (3) that the reaction 36 • THE DETERMIXATIOX OF THE AMOUNT AND of the mixture equalled the sum of the reactions of the two estimated separately. It has been found that the action of permanganate of potash is slow and imperfect in the cold, when each equivalent only gives off three instead of five atoms of oxygen, but that the organic matter is acted on rapidly when the temperature is raised. Dr. E. de Chaumont, unhke Drs. Letheby and Tidy, does not give any opinion respecting the amount of organic matter in a water. He neither declares that it is eight or nine (as Dr. Tidy asserts) nor twenty times (as Dr. Woods stated) the amount of oxygen of which the permanganate of potash is robbed, as the proportion is no doubt variable ; for the organic matter may be of different kinds originally, or in different stages of oxidation. He simply and solely furnishes the amount of oxygen used up by the organic matter. The correction necessary in consequence of the action of permanganate of potash on iron is but seldom made in practice, on account of the infrequent (?) occur- ence of this metal in drinking water. Allien, however, this correction is made, the iron is separated by careful concentration, and the employment of the colorimetric test with ferrocyanide of potassium. Hydrogen sulphide, which affects the permanganate of potash, can easily be detected by smelling the water after violent agitation of it. This gas should be ex- pelled by gently warming the water before the analysis is commenced. The pure artesian waters derived from the Thanet and Woolwich sandbeds, which contain a large excess of free ammonia {vide page 92), yield a great amount of total oxidizable matter when examined by this process, and but little organic oxygen. The difference cannot be ascribed to nitrous acid, for these waters are almost destitute of such. This acid may, however, be produced NATUKE OF THE OKGANIC MATTER 37 as the result of the reducing action of ammonia on the permanganate of potash. Rides. — 1, A good water contains of organic oxygen Rules for less than 1"0 milligramme per litre ( = "07 gr. per gallon). °"' ^^^^' 2. A usable water contains of organic oxygen more than I'O milligramme per litre, and less than 1"5 milli- gramme per litre ( ='^1 gr. per gallon). 3. A susjjicious water contains of organic oxygen more than 1"5 and less than 2-0 milligrammes per litre ( = "14 gr. per gallon). 4. A had water contains of organic oxygen more than 2"0 milligrammes per litre ( = '14 gr. per gallon). 5. Nitrites ought to be absent from good and usable waters ; their presence makes waters suspicious, and if in marked quantity a water should be pronounced to be bad. Tlie Objections to the Oxygen or Forchamnier Permangancde of Fotasli Test. Applied quantitatively, by either of the two last methods, may be thus summarized : — 1. Permanganate of potash readily oxidizes salts of objections, iron-, nitrites, and hydrogen sulphide, which are not uncommonly found in drinking water. If there is any suspicion afforded by the taste, or by a rusty deposit, of the presence of iron, the water should be subjected to one of the methods for its detection described on page 157. The detection and estimation of nitrites or nitrous acid is a very easy matter {vide page 106). If the presence of sulphuretted hydrogen is recognized by the sense of smell {vide page 1 4, on the odour of waters) this gas can be alto- gether expelled by warming the water before it is analyzed. 2. It affects but slightly urea, kreatin, sugar, and gelatine, and does not act on fatty matters. Nor does it furnish the total amount of oxidizable matter present in a water. Notwithstanding these defects the perman- 38 THE DETEKMINATION OF THE AMOUNT AND ganate of potash test employed quantitatively is a useful auxiliary to the other methods of water analysis. An iTnproved Quantitative Oxygen or ForcTiammer Permanganate of Potash Process. Dr. Dupre and the Society of Analysts have recom- mended (1) that stoppered bottles be employed instead of flasks, otherwise the test becomes useless in a water containing appreciable quantities of clilorides. Dr. Dupre has pointed out ^ that " the test fails in an open vessel on account of the mutual action of permanganate of potash and hydrochloric acid, whereby the former becomes reduced and the latter oxidized into water and chlorine, part of which escapes. When, however, the experiment is carried on in a closed vessel, tlie chlorine is retained in solution, and when at the end of the experiment iodide of potassium is added, this free chlorine liberates exactly the same amount of iodine as would have been liberated by the perman- ganate from which it was produced, and the effect is the same as if no permanganate had been destroyed by the presence of chlorides." (2) That the water to be examined should be raised to a temperature of 80° P., by the immersion of the bottle in a water bath or suitable air bath, before the addition of the sulphuric solution and standard potash permanganate. As more oxygen is absorbed at that temperature than at lower temperatures in all but the purest waters, the water should be main- tained at that temperature for 4 hours. If, in the course of the 4 hours, the pink colour of the water in the bottle is either discharged or even materially reduced, another dose of standard permanganate must be added, as the water must be always kept strongly tinted. The bottle should be in the dark during the period 1 Analyst, July 1885, p. 118. NATUEE OF THE ORGANIC MATTER 39 when the water is under the influence of the permanganate of potash. The 1 hour observation practised by Dr. Tidy, and the ^ hour observation by the Society of Analysts, are not of much value, for the information afforded by these brief exposures which is arrived at in other and better ways, does not compensate the operator for the additional labour. 7. The Wanklyn, Chapman, and Smith Process, consists in the estimation, by means of ISTessler's test, of the amount of ammonia present in a water before and after it is distilled with a solution of permanganate of potash and a large excess of caustic potash — a mixture which possesses the property of converting organic matter into ammonia. ISTessler's test, named after its discoverer, is an alkaline solution of the iodide of mercury {vide recipe on page 216), and is capable of detecting 1 part of ammonia in 20,000,000 parts of water. The addition of ISTessler test to the distillate of a water containing ammonia is attended by the production of a yellowish brown or amber tint, similar to that of sherry, due to the formation of the iodide of tetramercurammonium, the depth of which is measured, as it varies according to the amount of ammonia present. Some consider that it is only sufficient to add a small quantity of the ISTessler test to the water to be examined for organic matter, and that the depth of the brownish tint produced exhibits the amount of organic impurity. The ISTessler test is simply a test for ammonia, and is not a test for organic matter until that organic matter has been converted into ammonia, by boiling it with permanganate of potash and a large excess of caustic potash. Distillation of the water to be examined for ammonia adds to the delicacy of the process, for ammonia admits of concentration, and minute quantities are more visible in a small quantity of water than in double the amount. 40 THE DETERMINATION OF THE AMOUNT AND Distillation, moreover, by the separation of the salts in a water, such as magnesium chloride, etc., prevents the milkiness often created on the addition of the Nessler re-agent, which interferes materially with, if it does not altogether prevent, a correct estimation of the quantity of ammonia contained in a water. I cannot too strenu- ously urge on analysts the importance of the relation between the free ammonia in a water and that developed by the caustic and permanganate of potash solution, for on it is mainly based the indication as to the Mncl of organic matter contained in a water. The manner in which the ammonia distils over is a matter also of im- portance. Both of these subjects will more properly be discussed in the chapter entitled, " The Formation of an Opinion, and Preparation of Eeport," page 188. Before describing this process it will be useful to direct attention to the apparatus, chemicals, and solutions required {vide pages 43, 216, and 548). It is very important that the greatest cleanliness should be secured in the following chemical operations. The distilled water employed for the final washings of the glass vessels, and for all other purposes, should give no coloration with Nessler test, otherwise it should be redistilled. The process consists of two distinct stages — the estimation of the free ammonia and the calculation of the amount of albuminoid ammonia, alias the organic matter. JEstimation of the Amount of Free Ammonia, called hy some the Actual or the Saline Ammonia. Distil a little distilled water through the apparatus in order to thoroughly cleanse it. If we know it to be clean, it will be sufficient to wash out, by means of the Gmelin's wash bottle, the glass tube of the Liebig con- NATURE OF THE ORGANIC MATTER 41 denser with a little distilled water. Fit the tube of the retort carefully to the tube of the condenser either through the medium of an adapter {vide fig. 3), or by means of a packing of paper. The best plan, perhaps, is to select a retort which possesses a small tubular portion, around which a strip of clean writing-paper is rolled, sufficient to make it screw, not too firmly, other- wise there will be a fracture, into the condenser tube. It is very important to make this junction secure, so as to prevent the loss of steam. Place a half litre = 500 c. c. of the water to be examined in the retort by the aid of a perfectly clean funnel to prevent spilling. If the operator can introduce the sample into the retort without losing a single drop it is best to dispense with the funnel, for it is an additional article to keep clean. To facilitate the expulsion of the ammonia, it was formerly the practice to drop into the retort 1 gramme of freshly ignited carbonate of soda. Before returning the stopper to the retort throw a jet of distilled water on it with the wash bottle. The passage of a very slow stream of cold water through the Liebig's condenser should be maintained during the whole period of the distillation. The distillation should be conducted slowly, otherwise there may be a loss of ammonia in consequence of im- perfect condensation. Distil over into a ISTessler glass 5 c. c. Add to the distillate by means of a bulb pipette 2 c. c. of Nessler test. If it contains ammonia a yellowish brown or amber colour is produced ; the deeper the colour the greater is the quantity of ammonia present in it. If the amount of ammonia be very small, the tint will be that of straw. Dr. Charles Smart has pointed out -^ that the presence in a water of vegetable matter in a state of fermentative change is indicated by the development of a yellow colour in the water on the addition of carbonate 1 Sanitary Water Analysis, 1886. 42 NATURE OF THE ORGANIC MATTER of soda, and by a green coloration (accompanied by a haziness) of the Nesslerized distillates, of an olive or citron tint, which masks the characteristic amber brown colour produced by ISTessler test in a solution of ammonia. Imitate the depth of tint by mixing in a Nessler glass with 50 c. c. of distilled water more or less of the dilute standard solution of ammonia contained in the burette and add 2 c. c. of Nessler test. Wait always about three minutes for the colour to be developed. Nessler re-agent, which takes a longer time to produce its maximum tint, is not sufficiently sensitive. (To make ISTessler test " quick " add a little cold saturated solution of corrosive sublimate to it.) If the tint of the prepared standard of ammonia be too light, add to the prepared standard so much of the standard ammonia solution contained in the burette as is deemed to be sufficient to match the tint of the Nesslerized distillate. If the colour of the prepared standard be too dark, make up a fresh standard containing less ammonia. In conducting these colour test com- parisons it is always desirable that the waters contrasted should be about the same temperature. It is the practice of some analysts to throw away the second, third, and fourth distillates of 50 c. c. that distil over, as the first distillate generally contains f ths of the total quantity of ammonia. They simply add to it ^d in order to arrive at the sum total, e.g. — If the first distillate contains '09 milligramme in ^ litre Add 1 . . -03 Total quantity in the \ litre '12 milligramme = *24 milligramme per litre or part per million. It is sometimes necessary to Nesslerize the fourth or last distillate to assure oneself that all of the ammonia has passed off, for in some cases, as e.g. when urea is present, the ammonia may come off in the three ^ 3 03 03 l> a S rt t. H g i^ E a, S -2 5s ;:3 M rt a m -2 s ^ o -3 w Iz; ^ 5 d K " w J s a s CLl ft c •3 en' H^ § Bath an e Fig. 1 Stands ft ft r75 =3 'S tf H^ fq ^ « (3= 44 THE DETEEMINATION OF THE AMOUNT AND last 50 c. c. in increasing instead of diminishing quan- tities. Again, if the water under examination possesses much saline matter, or is very hard, as is shown by the furring of the sides of the retort during distillation, or by " bumping " of the water, the second or third distillate of 50 c. c. should be examined for ammonia by add- ing 2 c. c. of Nessler re-agent. If it exhibits no colour whatsoever, showing that all the ammonia has come off, the distillation is to be stopped. It is not wise to still further concentrate the water by removing a third or fourth distillate of 50 c. c, unless absolutely necessary, for the " bumping " may become so great during the second stage of the process as to fracture the apparatus. Estimation of the Amount of " Albuminoid Ammonia" alias Organic Matter, called also Organic Ammonia. The second stage in the process commences by measur- ing out in a Nessler glass (kept solely for this purpose) 50 c. c. of the caustic potash and permanganate of potash solution, and by adding it to the hot water in the retort. Eeplace the stopper and the Bunsen's burner. The flame of the burner should not be large, otherwise some of the colour of the permanganate of potash may be communicated to the distillate. Give the contents of the retort a wavy motion, or, better still, a rotatory motion, by gently moving the retort on its stand, so as to prevent " bumping," and again distil. Sometimes highly saline waters "bump" so exceedingly as to threaten an accident. ISTever let the mixture assume the appearance of a calm, for it portends a storm, in the shape of a sudden bursting into bubbles and boiling upwards of the contents. Keep the fluid always in motion, and see that the stopper of NATURE OF THE OEGANIC MATTER 45 the retort is securely fixed. Some persons, in dealing with such waters, drop into the retort scraps of tobacco- ]Dipe, or bits of recently ignited pumice-stone, to lessen this " bumping." The objection to this practice is, that we may inadvertently introduce sources of error, for these substances may contain organic impurities. It is a good plan in some cases to incline the neck of the retort upward, so that the liquid spirted up may fall back into that from which it is ejected. It is very needful to prevent this "bumping," apart from the danger of fracture ; for, if the colouring-matter of the permanganate of potash be carried over into the distil- late, the colour usually produced by the ISTessler re-agent is somewhat altered, and it then becomes difficult, if not impossible, to measure its depth of tint. Distil slowly in order to allow the caustic potash permanganate sufficient time to act on the organic matter, and in order to avoid imperfect condensation of the ammonia. Three distillates, each of 50 c. c, must be taken off, and each must be carefully Nesslerized. The colour of each distillate must be matched exactly in the manner above laid down when describing the mode of estimat- ing the amount of free ammonia, by adding a certain known quantity of the dilute standard solution of am- monia contained in the burette, to 50 c. c. of distilled water in a Nessler glass. The comparison between the colour of the standard and the distillate is made by placing the Nessler glasses on the white porcelain tile, and by looking down through the columns of fluid on to the tile. The amount of the dilute standard solution of ammonia employed to match the tint of the distillate represents the amount of ammonia in the distillate. For example, if the amount of dilute standard solution of ammonia required to match the tint of the 46 THE DETERMINATION OF THE AMOUNT AND 1st distillate be 5 c. c. 2d ,, „ 3 c. c. 3d „ ,, 1 c. c. we arrive at these figures — Alb. Ammonia . . . . '05 „ „ .... -03 „ „ .... -01 Total . -09 ■reparation Beginners find it troublesome at first to matcli the f standards, ^^j^^^^^ witliout making up several standards containing different proportions of the standard dilute solution of ammonia. It has been suggested by some that strips of glass, and by others discs, should be manufactured of the various depths of the sherry or amber colour, corresponding to the different tints developed by the Nessler re-agent with definite quantities of the dilute standard solution of ammonia. If such could be prepared so as to indicate accurately the various shades, a great saving of time might be effected. At one time I employed a dozen stoppered standard comparison bottles, of a capacity of about 50 c. c. Each bottle was provided with known and different quantities of the dilute standard solution of ammonia, and immediately filled up with twice distilled water. One c. c, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, and 23 c. c. were the amounts of the standard ammonia selected. To the contents of each bottle 2 c. c. of E"essler test were added. The weakest standard contained 1 c. c, and the strongest 23 c. c, of the dilute standard solution of ammonia. In making an analysis, the contents of the bottle or bottles that are considered likely to match the tint of the distillate are poured into a Nessler glass, and at its conclusion are replaced. These solutions slowly absorb ammonia, and get slightly darker in time, or they decompose, losing their colour and precipitating red iodide of mercury. Sometimes they become turbid, and sediments are depos- NATURE OF THE ORGANIC MATTER 47 ited. Dr. Mills' portable colorimeter^ has been employed for estimating the tints of the distillates, as well as for that of degrees of turbidity, but is, I find, of little help. Although one of these instruments stands in my labora- tory, it is never used. These supposed helps waste much time, and are not so accurate as the old plan of preparing a fresh standard solution when wanted. Practice very soon enables the water analyst to guess very closely the amount of the standard solution of ammonia which he will require to match any given tint, so that he does not often find the necessity of making up a second standard. I would recommend the Medical Officer of Health to make himself, by practice, skilful in matching tints, rather than rely on instruments as aids. The tapped graduated Nessler glasses, introduced by Mr. Hehner, are useful to the novice, or when rough calculations are alone requisite. Some analysts, instead of distilling over the four dis- tillates, each of 50 c. c, separately, mix them together and thus Nesslerize them. In so doing they lose valuable information, for it is important to note the proportions in which the ammonia distils over in each distillate. ( Vide the opinion of Prof. Mallet on page 208.) Sometimes a water yields nearly equal instead of decreasing quantities of ammonia, so that it is almost impossible to extract all the ammonia from a water before the distillation is at an end. This experience may occur in the examina- tion of waters polluted with urine, or dirty from the presence of soot (vide page 207). In such cases it is good policy, as has been pointed out by Mr. Sidney Eich,^ to Nesslerize the first 50 c. c, and to return into the retort the succeeding 150 c. c. that are distilled over, of course Nesslerizing the distillate or distillates ^ Described in Proc. of Glasgoiv Philosoph. Socy., March 12, 1877. The instrument is made by Cetti & Co., of Brooke Street, Holborn, London. ^ Chemical News, June 9, 1876. 48 THE DETEEMINATION OF THE AMOUNT AND procured by this redistillation. It is of no practical utility, in making sanitary analyses of water, to estimate the amount of ammonia derived from organic matter that is in excess of "50 milligramme per ^ litre =1 milli- gramme per litre, as that quantity is so much more than is sufficient to condemn. If it is desirable to measure the exact amount of the large quantity of ammonia evolved, a funnel tube with a glass stopcock should be adjusted by the help of a perforated cork in the retort through the stoppered opening, so that ammonia-free distilled water may be introduced in order to maintain the volume of the liquid in the retort constant. The process is now at an end. Allow the retort to remain uncleansed until another analysis is to be made, when the fur should be removed by strong hydrocliloric acid and an abundance of water. As half a litre has been taken for analysis, multiply the results by 2, in order to make them give the proportion for the litre. In the foregoing analysis, then, the results are the following : — Free ammonia, "24 milligramme per litre = part per million. Albuminoid ammonia, '18 do. do. I should like to indelibly print on the minds of all water analysts the following truth : — If you rely solely on the indications of this process, you will sometimes come to a correct conclusion as to the quality of a water, but very often a mistake will be made. Couple the evidence afforded by it with other evidence of a chemical and microscopical character, and an error will never be committed. I regard this process as a most valuable aid to the formation of an ox3inion by the Medical Officer of Health as to the nature of a water, as indispensable indeed as is auscultation to the physician in the diagnosis of lung and heart diseases. The e^ddence afforded by the stetho- scope is brought by him in juxtaposition to other evidence NATUEE OF THE ORGANIC MATTEE 49 bearing on the same point, and an opinion is formed from the sum total of all the evidence which is forthcoming. No physician dreams of relying solely on the character of the sounds heard from the lung by his ear, and of shutting himself away from all other sources of information. It appears that a member of the Society of Public Analysts, who holds two public analytical appointments, believes that the determination of the free and albuminoid ammonia is all that is necessary for forming an opinion on the quality of a drinking water, and he pronounces a verdict solely on the evidence afforded by these two estimations. Mr. Allen points out,^ as I have on several occasions, the absurdity of such a proceeding, for the rain water of country places would certainly be con- demned as polluted with filth by such an analyst. Elites. The following are the most recent rules which have Rules, been laid down by Mr. Wanklyn for the guidance of those who work this process : — He writes,^ "If a water yield '00 parts of albu- minoid ammonia per million, it may be passed as organi- cally pure, despite of much free ammonia and chlorides ; and if, indeed, the albuminoid ammonia amounts to "02, or to less than "05 parts per million, the water belongs to the class of very pure water. When the albuminoid ammonia amounts to '05, then the proportion of free ammonia becomes an element in the calculation ; and I should be inclined to regard with some suspicion a water yielding a considerable quantity of free ammonia, along with more than "05 parts of albuminoid ammonia per million. Free ammonia, however, being absent, or very ^ "On some Points in the Analysis of "Water, and the Interpretation of the Results ;" by A. H. Allen. The Anahjst, July 1877, p. 61. ^ Water Analysis. Fourth Edition, p. 53. E 50 THE DETEKMIXATION OF THE AMOUNT AND small, a water should not Le condemned unless the albummoid ammonia reaches somethmg like "10 per million. Albuminoid ammonia above '10 per million begins to be a very suspicious sign; and over '15 ought to condemn a water absolutely." Objections. Several objections have been urged against this process, the principal of which are : — 1. Taking a series of nitrogenized bodies, the propor- tion of nitrogen procured in the form of ammonia is not obtained in definite and simple fractions, but varies widely. The value of the process is not impaired because piperine yields the whole of its nitrogen as ammonia, because morphia yields one half, or theine yields one quarter, whilst albumen yields two-thu-ds ; for piperine, morphia, theine, and shnilar bodies are not usual constituents of well water. It has been remarked by Dr. Tidy that the importance of the Hct that organic bodies yield their nitrogen as albuminoid- ammonia in different proportions is much overrated, if the yield of albuminoid ammonia is found to keep pace with the purity or impurity (as the case may be) of waters. Messrs. Wanklyn, Chapman, and Smith, have distinctly affirmed that their process is designed for estimating the relative quality of drinking water, and is not one for the quantitative determination of nitrogen. 2. That the amount , of ammonia obtainable from albumen by the action of alkahne permanganate is in- fluenced by the degree of concentration of the solution and the rate of distillation. Mr. Wanklyn has stated most positively that the yield of ammonia is not affected by these circumstances, and in proof of this assertion re- fers to a set of experiments published by himself in 1867. 3. "If 20 grains of urea were present in a gallon of NATURE OF THE OEGANIC MATTER 51 water," wrote the late Mr. Wigner/ " the sample would be passed hj the AVanklyn, Chapman, and Smith's process as absolutely pure." It is stated by Mr. Wanklyn that fresh urea is not decomposed into ammonia by distilling with or without the mixture of caustic potash and potassium permanganate. It has been pointed out by Prof Mallet that it is erroneous to assert that urea is not convertible into ammonia, and evidence is given by him to the contrary.^ In the experiments conducted by Dr. Cory at the instance of the Local Government Board ^ it was found that the statement that urea yields no ammonia "is substantially correct," if it is dissolved in distilled water, but yet not quite accurate. He writes, " the impurities of a water will occasion a much greater proportion of ammonia to be formed from urea." Urea in a drinking water can hardly ever occur in a fresh condition. The ready fermentation of urea into carbonate of ammonia is a peculiarity of urea. The rapidity with which this change takes place is such that, in the examination of drinking waters which are polluted with urine, we may be pretty confident that sufficient of the urea has been decomposed before the water reaches our distilling appa- ratus to give a large excess of ammonia. 4. The inability of some eyes to arrange and classify tints, renders it possible that there may be several errors of observation in the comparison of so many distillates. If the analyst has any defect of vision approaching to a condition of colour blindness, it is desirable to receive all the ammonia distillates together (unless the amount distilled over after the first distillate is calculated by dividing by 3) and all the albuminoid ammonia distillates together, thus minimizing this source of error, although ^ Analyst, March 1878. - Op. idt. ^ Vide Eleventh Annual Eeport of the Local Government Board 1881-82, containing Medical Officer's Supplement for 1881, p. 127. 52 THE DETEEMINATION OF THE AMOUNT AND by SO doing valuable information is lost. (Vide pages 47 and 208). 5. " Peaty waters yield a flood of albuminoid ammonia." The absence of any excess of nitrates and nitrites, as in- dicated by their respective tests, shows that the organic matter is not animal but vegetable. 6. In the determination of both " free " and " albumi- noid" ammonia there is a loss resulting from imperfect condensation of the ammonia during distillation, and this loss is less marked in the estimation of small quantities of organic matter in a water than when it is in larger amount. This difficulty may be overcome by conducting the distillation very slowly, or by connecting to the end of the condenser tube a Nessler glass to which a U tube containing 25 c. c. of ammonia -free distilled water is fitted, such as is employed in the estimation of the nitrates and nitrites, page 115, so as to catch any ammonia that may be otherwise lost. 7. In some cases the albuminoid ammonia ol^tained as ammonia is actually less than the ammonia known to be present in the caustic and permanganate of potash solution. I do not remember ever to have encountered such an anomaly, which at all events could only occur in a water of great purity. In some cases nitrogenous organic matter is volatilized during the distillation for free ammonia, which if it had been retained would have yielded up its nitrogen as albuminoid ammonia, such nitrogenous matter escaping detection under either head. These are the weak points of the process which teach us that we should not rely on its indications to the exclusion of other information. The practical question answered by this process is not, however, as to how much nitrogen is contained in a water, but whether a water is wholesome or not. nature of the organic ^matter oc) 8. The Frankland and Armstrong Process. This process, wliich is based upon the principle, that when the residue on evaporation of the water is burned with oxide of copper, nitrogen and carbonic acid are eliminated from the organic matter, consists in the determination of the amount of organic nitrogen and organic carbon by a measurement of the respective volumes of these gases. The late Prof. Parkes, in his text-book on Practical Hygiene, writes respecting it: — "This plan requires so much apparatus, time, and skill, as to be quite beyond the reach of medical officers, and it would also appear that in the, hands of even very ahle chemists it gives contradictory results;^ the quantities are in fact so small, and the chances of error so repeated that, in its present form, this really beautiful plan seems not adapted for hygienic water analysis. It is also difficult to know what construction should be put on the results ; a water containing much non-nitrogenous organic matter may give a very much larger amount of ' organic carbon ' than a water containing a much smaller amount of nitrogenous matter, and yet be much less hurtful." The Elvers Pollution Commissioners (Sixth Ee'port, page 5), confess that "this process is both troublesome and tedious." It is generally admitted to be attended with a high experimental error, and is considered by some as yielding illusory results. As it is quite unadapted to the wants of the health officer, I shall not here describe the process, but must refer my readers to Sutton's Volumetric Ancdysis, or Dr. T. E. Thorpe's Quantitative Chemical Analysis, page 299. Some idea may be formed of the cumbrous and complicated nature of the process by glancing at the engravings in these works of two of the principal pieces of apparatus employed. The smaller is a Sprengel's Pump, which is ^ The italics are mine. 54 THE DETERMINATION OF THE AMOUNT AND attaclied to the combustion tube in which the solid residue is burnt with oxide of copper in a furnace. Tlie larger is the apparatus employed for the analysis of the gases thus obtained. Any one who is practically ac- quainted with modern quantitative analysis can learn this process in about a month. The large majority of medical men wdio are not provided with this foundation would require a six months' course in chemistry to prepare them for learning this process of water analysis. Again, the cost of the apparatus is a considerable, although of course not an insuperable oljstacle to its employment, being as much as thirteen guineas. Prof. M'Leod's ap- paratus for gas analysis, which is considered to be an improvement on Dr. Frankland's, is still more complex, and twice as costly, being £26 : 5s., whilst the price of Thomas' improved modification is £30. Prof. Mallet thus writes, " Prom the hands of a person without proper laboratory training its results are utterly valueless. It is but a method of approximation, involving sundry errors, and in part a balance of errors." The certificate of an analysis made by Dr. Prankland's elaborate process is about as incomprehensible as the process itself to all who are not chemical experts or analysts. Members of Sanitary Authorities and their medical officers often find these certificates perfectly unintelligible, although they are accompanied by ex- planatory notes for their interpretation. Can anything be more confusing to the public than the contents of the column headed " Previous Sewage or Animal Contamina- tion " ? I recently saw one of his certificates of an analy- sis of an excellent spring water, which contained in this column the numbers 1710, which was accompanied by the following remark : — " As this is spring water the evidence of previous sewage contamination which it exhibits may be safely disregarded." The expression " Previous Sewage NATURE OF THE ORGANIC MATTER 5 5 or Animal Contamination " is a very unfortunate one, for it has given rise to an endless amount of misconception. Animal matters in passing through the pores of clean soil become oxidized and converted into ammonia, nitrates, and nitrites, which are harmless. This oxidation, in other words this beneficial cleansing power of earth, does not continue for an indefinite period. Soil is liable to be in time overdone with filth, and is then unable to carry on this purifying action, so that the animal matters pass through it unchanged. Its particles require rest and free exposure to the air, before it recovers its expended power. Earth becomes relieved of the products of this dressing with filth by means of vegetation, which greedily incorporates them into its substance. "Previous Sewage " Previous or Animal Contamination" then, is the record of the pastf^^,]^fjf^'^^j^™' history of the water, being the sum total of the products of animal matter that have been oxidized, namely, the ammonia, the nitrates, and nitrites. This total, after the removal of the average amount of ammonia in rain, is re- presented as the mineral residue of the previous animal contamination of the water, in terms of average London sewage, 100,000 parts of which are roughly estimated to contain 10 parts of these three nitrogenous matters. Here is an example of the manner in which the figures in this column are obtained : — Nitrogen as nitrates and nitrites Ammonia ...... Deduct for nitrogen as nitrates, nitrites, and ammonia in rain ..... "5-881 Add and remove decimal point, and the figures 58810 are arrived at, which represent the "previous sewage or animal contamination." Or it may be calcu- lated by multiplying the sum of the quantities of nitrogen 5-911 •002 5-913 •032 56 THE DETERMINATION OF THE AMOUNT AND present as nitrates, nitrites, and ammonia, by 10,000, and by subtracting 320 from the result. Some of Dr. Frankland's disciples, perceiving doubtless the extreme liability to the misunderstandmg of this expression, have omitted or altered it ; for example, Dr. C. Brown's certi- ficates do not contain this column, whilst Mr. W. Thorp has substituted the term " total inorganic nitrogen," which corresponds with Dr. Frankland's " previous sewage con- tamination," minus the deduction for the ammonia in rain. The " total combined nitrogen " of these chemists, is the sum of (1) the organic nitrogen; (2) the nitrogen as nitrates and nitrites ; and (3) the ammonia. FmUs. It is useful for medical officers of health and other sanitarians to remember the following rules,-"- which guide those who employ this ]Drocess, in order that they may be able to interpret the results : — Quantity of Organic Carlion and Organic Nitrogen. — " The weight of the organic carbon found in different samples of water indicates the amount of organic matter with which the water is contaminated, but it does not reveal the source, animal or vegetable, whence that organic matter is derived." " Cceteris paribus, the smaller the proportion of organic carbon the better the quality of the water." " If the source of the organic matter be altogether vegetal a larger proportion of organic carbon than "2 part in 100,000 parts of water is undesirable, because it renders the water slightly bitter and unpalatable. A larger pro- portion of organic carbon if it be contained in animal matter does not interfere with the palatability of the water, but it exposes the consumer to the risk of infection." ^ Sixth Rejiort of the Eivers Pollution Commission, 1874, and W. Thorp's Article on "Water Analysis in Sutton's Volumetric Analysis. NATUEE OF THE OEGANIC MATTER 57 Vegetable organic matter is far from being destitute of nitrogen ; for instance, peat contains much of it. " Surface water and river water, which contains in 100,000 parts more than "2 part of organic carbon or ■03 part of organic nitrogen, is not desirable for domestic supply, and ought, whenever practicable, to be rejected. Spring and deep well water ought not to possess more than •! part of organic carbon or "03 part of organic nitrogen in 100,000 parts. If the organic nitrogen reaches "15 part in 100,000 parts, the water ought to be used only when a better supply is not obtainable."^ When the quantities of organic carbon and organic nitrogen exceed 2'0 and 0'5 parts, respectively, the sample may be considered as belonging to the class of sewages, the intermediate quantities indicating various degrees of pollution. Sewage usually contains about four parts of organic carbon and two parts of organic nitrogen. PmUo of Organic Carbon to Organic Nitrogen. — When Ratio, the organic matter is of vegetable origin the ratio is very high, and when of animal origin it is very low. As a qualification of this statement, it should be said that in the case of unoxidized peaty waters the ratio is diminished by oxidation ; and in the case of waters polluted by organic matter of animal origin a reverse action takes place, the ratio being increased by oxidation. In peaty waters the ratio may amount to as much as 20. In sewage it varies from 1 to 3. In unpolluted upland surface waters the ratio fluctuates from about 6 to 12, and in water from shallow wells from 2 to 8. The ratio in water for domestic supply may vary from 5 to 12, and that in polluted river water from 3 to 5. Frevious Sewage or Animal Contamination. — If the "Previous water be derived from a deep-seated spring or a deep ^^J^° ^ ^'^,j^_ well, and the previous sewage contamination does noti-aminatiou." exceed 10,000 parts in 100,000 parts of water, it is ^ Vide Water Analysis, liy Dr. Franklaml. 58 THE DETEKMINATION OF THE AMOUNT AND Table exhibiting Different Result of Analyses exjjressed Description. Total solid Impurity. Organic Carbon. Organic Nitrogen. Ammonia. Raix Water .... 2-95 •070 -015 •029 Upland Surface Water . 9-67 •322 •032 -002 Deep Well Water . 43-78 -061 •018 -012 Spring Water .... 28-20 •056 •013 ■001 UjJland Surface Water. The Teign above Old Wheal, Ex- mouth, Sept. 26, 1873 6-08 •582 •058 •004 Loch Katrine, the Water Supply of Glasgow, August 3, 1870 . 2-40 •185 -022 •001 Surface Water from Cultivated Land. The Thames at Thames Ditton, Jan. 31, 1873 .... 31 36 -325 -076 -003 Shallow Well Waters. Water from well at Alford, on the Don, Scotland, March 8, 1872 . 16-80 -048 •007 •000 Water from well in Well Close Square, London, June 5, 1872 . 396-50 -278 •087 •000 Churchyard Well, Leigh, Essex, ]Srov.'28, 1871 .... 112-12 -210 •065 -000 Deep Well Water, Water from Grays, South Essex Water Company, Feb. 15, 1873. 44-80 -064 •017 •001 Well at Waterworks, Colchester, April 2, 1873 .... 96-20 •174 -030 •021 Spring Waters. Eabate Fountain, Balmoi'al, March 9, 1872 1-40 -119 -014 -000 Spring supplying Town Well, Southam, Dec. 3, 1869 57-30 •282 -054 •Oil Beacon Hill Spring, Bath, Feb. 17, 1871 40-62 •253 •041 -000 Norwegian Block Ice . -47 •0^29 •005 •O05 Sea Water 3898-70 •278 •165 •006 Sewage 72-20 4-696 2^205 5-520 To convert parts per 100,000 into grains per gallon and the Hardness ^ Sixth Report of the Rivers Pollution Commission, NATURE OF THE OKGANIC MATTER Classes of Waters.^ in parts per 100,000. Nitrogen as Nitrates and Nitrites. Ratio. Organic Carbon . Previous sewage Contam- ination. Clilorine. Hardness. Total. Remarks. Nitrogen. •003 •009 •495 •383 4-7 10-1 3-4 4-3 42 10 4743 3559 •22 1-13 5-11 2-49 •3 5-4 25-0 18-5 ( Average Compo.sition of ( Unpolluted Waters. -000 •000 10^ 8^4 1-40 •85 2-6 •9 t A peaty water, which con- 1 tains more vegetable 1 matter than is admissi- ' ble for drinking. A very good water. •312 4-3 2820 1-75 23^9 ' Certain amount of animal pollution. Nitrates and nitrites present from use of manures. Most efK- ^ cient iiltration needful. •033 7-0 10 2-85 9^3 Good shallow well water. 25-840 5-047 3-2 3^2 258080 50150 34^60 13-75 19r 60- f Highly polluted shallow \ well water. / Polluted shallow well \ water. •929 2^582 4- 5-8 8980 25670 5-05 21 • 29-4 25-7 C Very pure, although con- -] taining much nitrates (^ from the chalk. Polluted deep well water. •000 8^5 •55 1-2 Exceedingly pure. •397 5-2 3740 2^00 33-5 1^205 •033 •003 6-0 5-8 1-7 2-1 11730 103 2^60 •05 1975-60 10-66 30^ 796 9 into degrees of Clark's Scale, respectively, multiply by -7. 1874, and Water Analysis, by Dr. Frankland. 60 THE DETERMINATIOX OF THE AMOUNT AXD reasonably safe, provided all contaminated surface water has been rigidly excluded from the well or spring. Eiver or flowing water which exliibits any proportion, however small, of contamination, and well or spring water containing fr-om 10,000 to 20,000 ^ar/fs of previous con- tamination in 100,000 parts of water, are considered susijicious or clouhtful. Waters more impure than those classed as suspicious must he regarded as dangerous. Objections. The principal are the following : — "Whilst professing to measure the organic bodies contained in a water, such substances are more or less decomposed and dissipated during the preliminary process of evaporation. The experimental error is often greater than the total quantity to be measured. There exists considerable doubt as to the accuracy of the results when a water contains some unstable form of organic matter in 'presence of a htrge excess of nitrates. There can be no question but that Dr. Frankland is sometimes inconsistent in his interpretation of the results of his analyses. Here is an example : — Parts per 100,000. Description. 5 - 5 & 5g o o < 111 P "5-3 5-feZ o o Opinion. Water from bore, 90 feet deep, Clayton AVest . . . •202 •051 3^9 •008 •000 2 •45 Good. Water from deep borinsf in Bourne, Lin- colnshire . . ■217 •047 4^6 •000 •000 2^10 Polluted. NATUKE OF THE ORGANIC MATTER 61 Prof. Mallet states that the extent of the disa Potash pro- results afforded by it, with any other process, for theycessand the are thoroughly misleading and unreliable. If the test isfncTArm-*^ employed quantitatively, in the most approved and most strong pro- recent fashion, it is most useful. The permanganate of potash process has clearly more to do with the estimation of the carbon than the nitrogen of a water, whilst the Wanklyn, Chapman, and Smith process is concerned more with the evolution of nitrogen as ammonia. Prof Mallet remarks, " It is not easy to admit the soundness of the logic with which Tidy points to the concordance of the results obtained by the permanganate of potash and combustion processes and the disagreement with both these of the results by the albuminoid ammonia process, hence apparently inferring that the two former are trustworthy and the last not so. He uses the sum of organic carhon and 7iitrogen to represent the results by the combustion process, and as the carbon forms generally much the larger part of this, he naturally arrives at an agreement with the results of the process, mainly depend- ing on the oxidation of carbon (the permanganate of potash process) and disagreement with those of the process (namely, the albuminoid ammonia) evolving nitrogen as ammonia." The permanganate of potash method cannot be cor- rectly described as a process, for it in reality forms only a part of one. The indications it gives should be con- sidered in conjunction with those afforded by an esti- 64 THE DETERMINATION OF THE AMOUNT AND mation of the amount of free and albuminoid ammonia, the nitrogen products resulting from the oxidation of organic . matter, and the quantity of clilorine, etc. Oc- cupying this subsidiary position, and controlled to a great extent by other evidence, it exhibits a remarkable agreement not only with the Frankland and Armstrong's process, but also with the Wanklyn, Chapman, and Smith process, when the latter is associated with a determination of the nitrates and nitrites. The agreement between the results afforded by the Frankland and Armstrong process, and the permanganate of potash method, is the more remarkable, because Dr. Frankland has publicly denounced the permanganate of potash test as perfectly useless and mischievous. The indications as to the quality of a water afforded by this salt are so corrected by those furnished by the other examinations of the same water, as to render it unlikely that any marked disagreement should occur between this permanganate of potash test, as carried out in the most approved manner, and the other two processes. The processes, which have assumed an antagonistic rivalry, and are credited with furnishing contradictory decisions, are the Frankland and Wanklyn methods. Prof Mallet finds "a good deal of similarity between the figures of albuminoid ammonia and those for organic nitrogen by the Frankland combustion process, but with frequent discrepancies of varying extent, such as prevent the one being taken as the accurate measure of the other." 1 Dr. Hill of Birmingham has made a comparison be- tween the two processes, by placing by the side of the organic nitrogen of Frankland's method the amount of nitrogen calculated from the albuminoid ammonia of Wanklyn's method, thus : — ^ Op. cit. NATUEE OF THE ORGANIC MATTER 65 Birmingham Fiihlic Water Sup;f hj. Date. Organic nitro- gen by Frank- land and Arm- Albd. Amm. = by the Wank- lyn, Chapman, and Smith process. N. Ratio of organic nitrogen to nitrogen by the 1875. strong process. two methods. January •097 '•016 013 7 : February •070 '•022 018 4 : March •099 •020 016 6 : April •064 •014 Oil 6 : May •048 •Oil 009 5 : June •049 •016 013 4 : July •090 •014 Oil 8 : August •120 •018 015 8 : September •072 •010 008 9 : October •070 •014 Oil 6 : November •124 •024 020 6 : December •080 •014 Oil 7 : He argues therefrom, that (1) as the amount of nitrogen yielded by the albuminoid ammonia of the Wanklyn process is very much less than that furnished by the Frankland process, which every one admits, and (2) as the ratio is not constant, the Wanklyn process is worthless. ISTow this mode of comparison appears to be unfair, because it proceeds on the assumption that Dr. Frankland's process of water analysis is a standard of accuracy, a pretension which is open to considerable doubt, although as one for the analysis of gases it may be most excellent. (Vide Prof. Mallet's opinion on page 61). Although, then, anything like a contrast of numbers is out of the question, a comparison of the opinions of a water formed according to the rules laid down by the inventors of the respective processes, from a consideration of the figures obtained, is a perfectly feasible project, and one likely to be attended by useful results. These opinions may not be strictly correct,^ but sufficiently so ^ It is an excellent rule, which unfortunately could not be followed here, to decline to give any decision respecting the nature of a water until F 66 THE DETEEMINATION OF THE AMOUNT AND to ascertain whether or not any distinct antagonism exists. The following is a copious abstract of a paper entitled, "A comparison between the Frankland and Armstrong, and the Wanklyn, Chapman, and Smith processes of water analysis," which was presented by me to the State Medicine Section of the British Medical Association, at its annual meeting held in 1877, in Manchester, and was accompanied by a table that contained 93 analyses of waters made by these two methods at or about the same time. Many analyses of waters performed by both the Frankland and the Wanklyn processes have been sent to me, notably those from Clayton West, near Hudders- field, which I have not inserted in the table of comparison, simply and solely because they were not made simul- taneously, but with an interval of weeks and months elapsing between the periods at which the water was submitted to the rival processes. Waters change much in the amount of organic matter which they may contain at different seasons. The waters of wells are greatly influenced by : — (1) height of the subsoil water, which is always varying; (2) by the amount of water that is passing through the subsoil of a country ; and (3) by heavy downfalls of rain or periods of drought. I have many times found a water pure at one time and impure at another, and this occasional pollution of a water is often due to the periodical washing of filth into a well by heavy rains. The disagreement in the opinions of able analysts respecting the purity of samples of water taken perhaps within a short interval of time from the same well is often due to these causes. furnished with the fullest information regarding its source, — as, for ex- ample, the geology of the district, depth of the well, character of the surroundings, etc. NATUEE OF THE ORGANIC MATTER 67 Dr. Asliby, Medical Officer of Health, made six analysesDr. Ashby's of different waters, employing the Wanklyn, Chapman,!^ '^^'y^®^- and Smith process, and reported certain of them to a sanitary authority as unfit for use. The agent of the property to which the wells belonged, immediately, and in a private manner, sent samples of the same waters to an analyst who used the Frankland and Armstrong process. The opinions formed by both analysts of all the waters examined by these two rival processes coincided in every instance. The figures are unfortunately not obtainable, so that they are not included in the table, but that the same general result was afforded in each case, and that similar conclusions were drawn about the quality of these six different waters, some pure and others impure, is an interesting fact. An examination of the complete table shows that in only one single instance is there a distinct contradiction of opinions, and here the conflict of views is readily accounted for. In every other case where the opinions are not identical, the adjectives used to denote the de- cisions respecting the character of the water are qualified by some adverb. For example, when an analysis of a water by one process indicates the sample to be " good,' or " bad," an analysis by the other process of the same water gives a verdict of " very good," or " highly sus- picious," etc. Before studying the following table, which is an abstract of the complete one, it should be clearly under- stood that this comparison is confined to the question of the quality of a water as regards the amount of animal and vegetable organic matter contained in it. Several of the waters in the table, as for example the last, viz. " Eaven's Well," would pass muster solely from the consideration of the amount of organic matter contained therein, but would be objected to for other reasons. The 68 THE DETERMINATION OF THE AMOUNT AND Analyses of Waters made at or about the same FranJdand and Armstrong jjrocess. Parts per 100,000. Descripiion of Sample. 5 Z 6 3 If 0-= 1 1.2 111 O _c3 C ^ ci K s s o Opinion. Deeply bored well . . . •229 •055 4^2 •299 297 Good.* Water used for the washing of milk cans at an Islington Daily . 1-820 •710 2-5 •120 •400 7-10 ( Horribly 1 polluted. AVest Middlesex Water Com- pan}^ January 1873 . . . •341 •034 10-0 •001 •266 1^9 Indifferent. Surface spring . •128 •027 4^7 •004 ■471 6-92 Suspicious.* Well water . . •177 •017 10-0 ■004 •184 2^72 Good.* Deeply bored well . . . •093 •009 11-4 •241 3^61 Good. Water from deep well . . . •110 •062 1-9 •002 •253 3^1 Good.* Well in Kowe's Square, Cardiff •181 •037 5^0 3 ■76 15^5 Bad.t Artesian Well of Maldou Water AVorks . . . •148 •029 5^1 •110 35 ■S Good.t "Raven's Well" (deep) . •261 •023 11-3 •001 ■007 9-9 Prett-y Good. NATUEE OF THE OEGANIC MATTER 69 time BY THE Feankland and Wanklyn Peocesses. WanMyn, Chapman, and Smith 2}rocess. MlLLIORASlME PER Litre. Grains per Gallon. 1-10 •04 •04 •04 •04 •08 •08 •12 •09 •06 •10 •1-2 .•13 •12 •04 •02 •11 •01 •08 •17 2^64 •67 7^40 Trace. •07 •06 2-0 5-1 1^4 4^8 1^9 2-1 10^81 10-81 11-80 25-7 25 •o 25 •o Opiniox. •00 7^3 Vei-y good. Horribly polluted. Not first rate. Suspicious. Pretty good. Good. / Moderately I good. Bad.7 Bad.S Bad. 77 Good.X Good.w Bad.x Good./3 Pretty good. Remarks. "■Opinion of the analyst, Dr. G. Brown. /'Analyses made by Dr. i Bartlett, who states that < 29 cases of typhoid fever I occurred amongst the \^ customers of the dairy. + Opinion of the analyst, Dr. Frankland. 7 Opinion of the analyst, Mr. Thomas. 3 Opinion of the analyst, Mr. Scott. 7) Opinion of the analyst, ilr. Wanklyn. X Opinion of the analyst, Dr. Tidy, w Opinion of the analyst. Dr. Whitmore. X Opinion of Messrs. Hassall andHehner, theanalj-sts. /3 Opinion of Dr. Cornelius Fox, the analyst. N.B. — The sample received by Has- sall and Hehner was jirobably obtained from a dirty cistern. 70 THE DETEEMINATION OF THE AMOUNT AND water was condemned because of its large amount of saline matter and its excessive hardness. A very careful study of the two processes, and the comparative results afforded by them, lead me to the following conclusions : — Conclusions. 1. In ouc iustancc only out of 99 analyses, details of 93 of which are in my possession, is there a distinct conflict of opinion, and in this exceptional instance the divergence in the results obtained is easily explained. 2. The opinions do not in a great many instances coincide exactly, but the adjectives denoting them are modified by some qualifying adverb. 3. When the results of analyses made by the two processes at or about the same time do not at all agree, the divergence is generally due to the neglect on the part of those who practise the Wanklyn, Chapman, and Smith process, to estimate the amount of nitrates and nitrites, and to be guided by the evidence thus afforded. 4. The results are not concordant unless the analyses are performed upon the same water at the same tune. 5. A really bad water would not be likely to escape detection by either process if the nitrates and nitrites are always estimated. 6. The danger of the delivery of contradictory opinions respecting any given sample of water, lies chiefly in the fact that Frankland's process gives higher results than Wanklyn's method, so that a water pro- nounced as just passable by the latter process might be condemned by the former. NATUEE OF THE ORGANIC MATTER 71 VALUE OF THE FEANKLAND AND ARMSTRONG, WANKLYN, CHAPMAN, AND SMITH, AND THE QUANTITATIVE FOR- CHAMMER PERMANGANATE OF POTASH PROCESSES IN THE DETECTION OF DANGEROUS POLLUTIONS. An investigation was carried out during the years 1880-81 by Dr. Cory, at the instance of the Medical Department of the Local Government Board, to determine whether chemistry was able to distinguish between water contaminated by common or specifically infected filth. The experiments lead to conclusions of rather a startling character which, unless faced and dealt with, may diminish the faith of water analysts in their powers of diagnosis. •■• "Waters were polluted with weighed portions of excrement from a case of typhoid fever and from a man in perfect health, and comparisons were instituted. On page 137 of the Eeport is a table and comment on the same, of which the followinff is an abstract. IiK^'ements indicated by- analysis to have been gained by additions of known quantities of material to a gallon of water. Polluted with "OS grni. of typhoid stool. Polluted Polluted with -05 with -1 grm. of grm. of healthy typhoid stool. stool. Polluted with •! grm. of healthy stool. Chemical Increments in grs. per gal. Volatile matters Ammonia Alb. ammonia 1-12 •0004 •0020 .•96 •0015 •0059 •12 •0006 •0048 1-e •0026 •0216 " The addition of the typhoid stool gave to water far less indication of pollution than was given by an equal quantity of healthy stool." (a) As regards this table, it is worthy of note that the 1 The inconclusive nature of this Report is described in detail in a paper entitled "Remarks on the Examination of Water for Sanitary Purposes," read before the Socy. of Med. Officers of Health on February 16, 1884, by C. E. Cassal and Dr. Whitelegge. 72 THE DETERMINATION OF THE AMOUNT AND healthy man was fed during four days previous to the experiiaent on a much larger amount of soluble nitrogen- ous organic matter than the patient with whom he was compared, hence the striking difference observable in the amount of volatile matters, which were nearly twice as much in the healthy as in the typhoid case. (b) The proportion of the highly carbonaceous matter of the biliary discharges to nitrogenous matter may have been greater in the one case than in the other. (c) The solubility of constituents of stools was not shown to be alike in both cases. Again we are confronted on page 142 with a table, of which the following is an abstract : — Umpol Lar Dupre,rr LUTED Sa «PLES. er. Vanklyn. Poll Lamlae in the pi of solub typhoid UTED Samples. ibetli wal th water polluted oportion of '21 gr. e solid matter of stool to each gall. ankland,^ Dupre,Frankland,Wanlclyn. Oxygen absorbed from Permanganate Ammonia .... Alb. Ammonia . . Organic Carbon . . Organic Nitrogen Grains per Gallon. Grains per Gallon. •2415 ■0011 •0090 •2114 •0371 •0014 •0056 •2512 •0016 •0100 •2205 •0399 ■0007 •007 The result is in accordance with our previous know- ledge as to the impossibility of distinguishing between healthy and specific contamination of drinking water. The three different processes supply general indica- tions, which require to be checked by other evidence. Whilst the albuminoid ammonia process furnishes us with ammonia evolved by a portion only of. the organic matter, and the oxygen process only records the oxygen used up by a part of the organic matter, the combustion process yields the carbon and nitrogen contained in the NATURE OF THE ORGANIC MATTER 73 residue of a water to the exclusion of that lost during the evaporation of the same. Duplicates of the samples of water polluted by typhoid and healthy excrements were examined microscopically, and each sample that was thus examined was found to contain "crowds of bacteria" — a fact of itself most damag- ing to the character of any drinking water. I do not remember ever to have seen a natural water containing " crowds of bacteria" in each field of the microscope that did not present other evidence, sufficient when combined to condemn it as a water supply. The inquiry affords a confirmation of the accuracy of the opinion expressed by me for the last eight or ten years, that a sole reliance on the results afforded by these processes for the detection of the carbon and nitrogen (apart from subsidiary analytical e^ddence, in which respect the Medical Officer of Health's method differs from all others) often leads to mistakes. It does not follow that, because chemical analysis might have failed to detect the accidental poisoning by a workman of a vast quantity of pure water by specifically infected matter, as at the Caterham and Eedhill outbreak of enteric fever (of which failure no proof was afforded^), therefore water analysis is useless. In ninety-nine cases out of one hundred (1) such specifically infected matter is introduced into a well in conjunction vnth other animal organic matter; (2) the presence of animal organic matter indicates an open door or channel for the chance entrance of specific poison ; and (3) as a matter of experience it may be confidently asserted that, as a rule, minute quantities of specifically infected matter do not alone gain admission into well water. If the " filth diseases " are propagated either through the instrumentality of living organisms with their ■^ The author possesses evidence ■which tends to show that a great change did take place in the amount of the minevcd constituents of the water. 74 THE DETERMINATION OF THE AMOUNT AND power of unlimited self-multiplication, or by animal poisons, associated each with its characteristic organism, it is probable that a large amount of organic matter in a water is more objectionable than a small amount, as furnishing more material and conditions suitable for the develop- ment of noxious as well as harmless organisms. So far as regards the bacillus anthracis, it has been shown ^ that this micro-organism does not flourish in pure water. Its food supply is used up within a few hours, and the water which has been infected with it soon loses, when applied to a suitable culture-medium, its infective property. The duration of infectivity in purposely infected water was found to vary with the proportion of nutrient animal matter contained therein. As Tiemann and Preusse have well pointed out,^ although an impure water is not neces- sarily pernicious, a polluted water is more likely to contain disease ferments than a pure one. 9. — Koch's Biological Method. The determination of the amount of organic and mineral matters contained in a water may be usefully supple- mented by an estimation as to the number and nature of the micro-organisms in it, which supplies us with informa- tion that a chemical examination does not afford. Bacteriological researches as to the nature and life- history of micro-organisms belong to laboratories devoted to biological investigations, but the power of ascertaining whether their number in a water is beyond the normal amount is within the reach of the health officer. The difficulties which attend the employment of the following adaptations of Koch's biological process to water examina- tion are involved in the necessity of the expenditure of a great deal of time, a close attention to details, the 1 Eeports on London Water Supply, for June and August, 1886, by Mr. W. Crookes and Drs. Odling and Tidy. ^ Chemical Neivs, January 16, 1880, pp. 30, 31. NATUEE OF THE ORGANIC MATTER 75 observance of scrupulous cleanliness, and the \vant of a tlioroughly satisfactory mode of numerically distinguishing waters of similar organic impurity one from another. The first to be described is a qualitative examination, Dr. Jiuter's which has given some very striking results in the hands ^^'^'^' of Dr. Muter.^ Obtain some good fresh gelatine^ in very thin lamince. Thoroughly dessicate it at the highest possible temperature, and enclose it in a carefully cleansed and dried bottle. Then 100 c. c. of redistilled water is well boiled in a clean flask, the mouth is closed by cotton wool, and the whole is allowed to cool to 90° r. Four grammes of the gelatine and two centi- grammes of sodium phosphate are now placed in the flask, and the mouth having been again closed, agitation is persisted in until entire solution takes place. A fresh egg is now broken, and a little of the white is added to the contents of the flask, which are then boiled and filtered through a paper sterilized by heat ; 2 5 c. c. of the filtered liquid are then mixed with an equal volume of the suspected water in a tube closed by cotton wool, and kept at a temperature of 60° to 70° F. A comparison tube is also set up with redistilled and previously boiled water. With really infected water, a cloudy layer of bacteria will form within a comparatively short space of time, and the gelatine will liquefy from the surface down- wards, and will disengage putrid-smelling inflammable gases. TJie late Dr. Angus Smith's adaptation of Koch's Method of Water Examination.^ A 5 per cent solution of the thin leaf gelatine, which Dr. a. solution melts at about 80° F., is clarified by filtration or adaptation. ^ Analyst, September 1885. ^ French gelatine, sold in thin transparent sheets, of the best quality, is preferred in biological experiments. ^ Second Keport under the River Pollution Prevention Act of 1876, to the Local Government Board, "On the Examination of Waters." 76 THE DETERMINATION OF THE AMOUNT AND by fresh albumen. Of tliis solution 2 5 c. c. are placed in a test tube and then mixed with 25 c. c. of the water to be examined, and kept for some minutes at that tempera- ture; but much smaller quantities are frequently sufficient. The tubes in which the experiments are made are about 8 inches long and 1 inch in diameter, with stoppers of cotton wool only. After the mixture cools it becomes solid around any organisms which may be present, transparent spheres forming which contain active and inactive bacteria. Distilled water, if examined, exliibits no change, but other waters display, according to their purity, a greater or less number of these spheres or colonies, which may be counted. A number of very minute white dots are sometimes "\dsible, and seem to indicate the number of points of vitality in the w^ater. Sugar and phosphate of soda were in some experiments, by Dr. A. Smith, added to the gelatine, both together and separately; but gelatine alone seemed to give clearer and simpler results. He writes, " Of all the forms of change in these tubes, that which seems to be connected with the most offensive waters is the liquefying of the surface. The number of points of activity one naturally considers a measure of impurity." Dr. Percy FranUancVs adaijtation of Koch's method of Water Examincdion} Dr. P. "Composition op Medium and M ODE OP Jr'REPARATION Frankland's Lean meat .... 1 lb. adaptation. Gelatine .... 150 grms. Peptone (solid) • 10 „ Common salt 1 „ Di'stilled water 1 litre. ^ "New aspects of Filtration and other methods of Water treatment : The gelatine process of "Water examination." A paper originally presented to the Socy. Chem. Industry, but since reprinted. ' Koch employs 100 grms., which has been found insufficient, as it liquefied at as low a temperature as 68° Y. NATUKE OF THE OEGANIC MATTER 77 The meat is finely minced and infused with a half litre of cold distilled water for 1 to 2 hours, the solid part being then strained off through linen. The gelatine is allowed to soak in the other half litre of water, and to this the extract of meat is added. The whole is now heated until the complete solution of the gelatine has taken place, the peptone and salt being then added and allowed to dissolve. This liquid exhibits a distinctly acid reaction, which must be carefully neutralized by means of carbonate of soda. The neutralized liquid is then clarified by beating into it the contents of two or three eggs, along with the broken shells, the whole being briskly boiled for a few minutes. The coagulated albumen rises to the surface and carries with it the other solid particles suspended in the liquid. On then strain- Filtration of ing through linen, a fairly clear liquid is obtained, which ™^g*'^^^^' is finally clarified by passing through filter-paper placed gelatine medium. Fig. 4. Glass funnel surrounded by Copper Jacket for iiltering Gelatinized Meat Infusion. in a funnel provided with a hot water jacket, the filtrate being rejected until it runs perfectly clear and limpid. 78 THE DETERMINATION OF THE AMOUNT AND The filtrate sets on cooling to a yellowisli brown trans- parent jelly. Whilst still liquid it is poured into clean test tubes, the quantity which I employ in each tube Sterilization being cxactly 7 c. c. The test tubes are tightly plugged with cotton w'ool and then at once sterilized by steaming them for half an hour on three consecutive days in a vessel made expressly for the purpose, and the con- struction of which is shown in the accompanying figure. by steam. ^^ ? Steaming Apparatus and Steamer to fit in ditto. t. Thermometer. =^ Tubes prepared and sterilized in this manner I have found to remain unchanged for an indefinite period of time." ^ 1 If it is desired to avoid the trouble of preparing sterilized meat peptone gelatine, it can be purchased from Dr. H. Rohrbeck of Berlin in test tubes or flasks. NATUKE OF THE OEGANIC MATTER ■9 Collection of Samjjles of Water. — Glass stoppered collection of bottles of about 70 c. c. capacity are cleansed, rinsed ^^™^'^^' with distilled water, dried and kept in an air bath at from 302° F. to 356° F. for at least 3 hours. In taking a sample the outside of the bottle should be rinsed in the water before removing the stopper, and exposure to the air be reduced so far as possible to a minimum. The mouth of the bottle should not be allowed to come into contact with the tap. In collect- ing samples from ponds or rivers, the stopper should not be removed until the bottle is completely immersed in the water, and should be replaced whilst still below the surface. Sterilization of A'pimratus. — It is necessary to steri- sterilization lize every article that is used in these experiments. ^^^°*^""" Fig. C. Hot air chamber for sterilizing Pipettes, Glass Plates in metal box, cotton wool, etc. t. Thermometer. Dr. Klein states^ that cotton wool should be exposed in a loose state in a hot air chamber to a temperature ^ Micro-onjanisms and Disease. 80 THE DETERMINATIOX OF THE AMOUNT AND as high as from 266° F, to 302° F., for several succes- sive hours, for several successive days, and that it ought to be just singed. Glass apparatus is sterilized by exposure in the hot air chamber for 3 hours to a tem- perature of from 302° F. to 356° F., and by washing in sterilized distilled water or a 2 per cent solution of corrosive sublimate. Tlie Examination of SamiJle, which should be performed as soon as possible after collection,^ must be violently shaken to ensure an even distribution of the organisms throughout the water. At this stage Koch determines ^ approximatively, by making a cover glass preparation {vide page 161), the number of micro-organisms present, in order to judge as to the quantity of the water under examination which should be used. " If on microscopic examination one bacillus be detected in each ' field,' one drop of the water will contain many hundreds, and less than 1 c. c. should be taken for mixing with the gelatine. On the other hand, should several ' fields ' have been examined without detecting a bacillus, then 1 c. c. of the water should be taken." It is better to take too little water than too much, because in the latter case the colonies are so crowded that it is almost impossible to count them. A tube of the sterilized gelatine peptone medium, melted by placing it in water not heated above 86° F., is opened after first singing the external portion of the cotton wool plug. Into it one or more drops ^ 1 In a receut number of the Chemical Keics, Dr. T. Leone is reported to have found that the pure spring -R-ater which supplies Munich enters it Avith 5 organisms in each 1 c. c, which on standing 24 hours increased to 100, in 2 days to 10,500, and on the 5th day to half a million, this multiplication occurring at a temperature of from 57 "2 to 64 '4° F. 2 The Biological Examination of "Water as carried out in the Reichs Gesundheits Amt. Berlin, vide paper by Professor Warden in Chemical News, July 31, 1885. 3 It is necessary .to ascertain how many drops, delivered by the pipette employed, form 1 c. c, as drops differ so much in size. NATUEE OF THE OEGANIC MATTER 81 (according to the quantity it has been predetermined to employ) of the water under examination is transferred by means of a graduated pipette (which has been pre- viously sterilized in .a tin box by heating it from 302° F. to 356° F.) and the water and gelatine are rapidly mixed (carefully avoiding the formation of bubbles) by agitation in the tube, which is held in a slanting position to prevent the entrance of dust. Arrangement for recejition of Glass Plate. — A soup Plate cuiti- plate, in which rests a very short -legged tripod, which ^ Ftg. 7. Apparatus employed for Plate Cultivations. (After Crookshank.) Tripod stand ; Glass dish, filled with cold or iced water ; Sheet of Plate-glass ; Spirit Level, and Glass Bell. supports a glass plate protected by a glass cover, having with its contents been rinsed with boiled redistilled water immediately before use, is by the help of a spirit level rendered perfectly horizontal, and a little of the same sterilized distilled water is poured into it so as to form a seal between the outer and inner air. Dr. Edgar Crookshank recommends ^ that the solidification of the liquid nutrient jelly should be hastened by placing the glass plate on a slab of glass covering a vessel full to the brim with cold water, which may be iced in warm weather. ^ Introduction to Practical Bacteriology. G 82 THE DETERMINATION OF THE AMOUNT AND Prof. Warden states that this arrangement may be improved by placing the water -receiver in an empty shallow vessel into which it fits loosely, and in which it is supported on three pieces of cork. This outer vessel which rests on the tripod serves to receive the overflow water and any moisture which may condense on the sides of the iced water -receiver. A sterilized glass plate is now withdrawn (the future upper surface being held Fig. S. Inculjator, with a gas regulator (a) in air chamber. (After TVoodhead and Hare.) downwards) from a metal box in which it has been sterilized, and is placed on the levelled plate, and the contents of the test tube are poured on to it. Koch and others ad^dse that the gelatine be evenly spread over the plate by the help of a sterilized glass rod so as to form a square. As soon as the gelatine has set on the plate it is at once removed in its dish into an incubator, main- tained at a temperature of from 68° F. to 77° F. Koch NATURE OF THE ORGANIC MATTER 83 recommends that the glass plate after solidification of the gelatine should, instead of being placed in an incubator, be transferred to the glass bench of the " damp chamber," where in the course of a day or two, according to the temperature of the room which should be from 60° F. to 65° E., the colonies will develop. The "damp chamber " Damp consists of a shallow glass dish, a covering bell, and glass *^ ""'" rack, all of which have been thoroughly cleansed and washed with a solution of corrosive sublimate (1 part to 1000 of water). The bottom of the glass dish is covered with two or more layers of filter -paper cut to the Damp Chamber for Plate Cultivations. (After Crookshank.) It contains a glass rack on which rest gelatine glass plates. size, taking care that it does not project beyond the edge of the covering bell. The vertical portion of the glass cover is lined internally by some with a circular strip of blotting- paper to prevent any drops of condensed moisture from falling on the plates. All of the blotting or filter-paper is moistened with the corrosive sublimate solution. Dr. P. Frankland writes, " The period of incubation generally varies from 3 to 5 days, but sometimes it is continued for a longer period of time, to make sure that all the organisms present have had a due opportunity of develop- ment." The gelatine plates are daily inspected during the period of incubation, without removing the glass cover, so that the progress of the colonies derived from the in- dividual organisms may be watched ; when these have 84 THE DETEEMINATION OF THE AMOUNT AND reached such dimensions that they are distinctly visible to the naked eye, and before the contours of different colonies have begun to coalesce, the plates are withdrawn for examination. The colonies are counted with the aid of a strong hand -lens, the more doubtful ones being further examined by means of a simple microscope. In Enumera- Order to arrive at an accurate conclusion with respect to the number of colonies, it is necessary that they should all be counted individually ; but, in cases in which the tion of colonies, Fig. 10. Apparatus for estimating the Number of Colonies in a Plate Cultivation. (After Grookshank.) The ruled plate di^aded into centimetre squares, some of which are suh-divided into ninths, is so arranged as to cover the gelatine plate without touching it. colonies are very numerous, an estimate of the total number may be formed by placing the gelatine plate on or beneath a second glass plate ruled in squares, the arrangement resting upon a black ground. The colonies present in a few of these squares are counted and then multiplied accordingly. A substitute for this appliance is made by ruling with a white lead-pencil, on a piece of dull black paper pasted on cardboard, a square divided by horizontal and vertical lines into 100 centi- metre squares, several of which may be sub-divided by two horizontal and vertical lines into nine smaller squares. Dr. P. Frankland found that if boiled distilled water is examined, the gelatine plates almost invariably remain NATURE OF THE ORGANIC MATTER 85 unchanged. Koch considers that 3 colonies is the average obtained with distilled water. The following observations on the Metropolitan Waters are interesting as an earnest of what this method is capable : — Micro-organisms in 1 Cub. Cent, of Metropolitan Waters, 1885. Jan. Feb. Mar. May. June. Se'pt. Oct. Nov. Dec. River Thames at — Hampton^ . . Chelsea . . . West Middlesex Southwark . . Grand Junction Lambeth . . River Lea at — Chingord MilP New River . . East London Deep Wells. Kent — (Well at Deptford) . . Supply . . . "s 2 13 382 10 "7 25 16 23 16 26 57 5 '7 39 41 10 7 246 28 69 95 17 "'9 14 3 24 3 30 "3 121 20 155 22 21 6 26 81 26 47 18 38 27 22 1644 13 2 18 43 103 "3 29 'i"4 714 34 2 24 40 26 2 53 6 18 18662 3 5 32 40 26 9542 n 14 8 "9 15 73 134 124 18 317 5 7 Micro- organisms in London waters. The water of the Kent Company leaves the well, as is seen, almost wholly destitute of organic life, and the few organisms which it does contain are almost certainly im- ported into it en route to its supply. I would recommend the adoption of Dr. Angus Smith's method to those who have but little time to expend in such examinations. To those who have had some experience in the observation of micro-organisms I would commend Dr. P. Frankland's method, with the modifications of others, which is undoubtedly the best that has been devised. ^ These iigures represent results obtained by the examination of the waters above the intakes of the Water Companies, and show the efiect of the storage and filtration of the waters which they supplj'. 2 Heavy floods during November. 86 the determination of the amount and 10. The Estimation of Dissolved Oxygen IN Watee. The old custom of judging of the purity of a water by the amount of its dissolved oxygen has recently been revived. The question, however, as to whether the quantity of oxygen bears any constant ratio to the organic impurities is an open one, and requires elucidation. As water becomes more and more contaminated with putrescent organic substances, the quantity of dissolved oxygen in it rapidly diminishes. Dr. Odling has shown that at a temperature of 59° F. three volumes of oxygen are dissolved in 100 volumes of water, and that an increase of solubility is obtained by a reduction of tem- perature. At the summer temperature of 70° F. water contains 1"8 cub. in., and at the winter temperature of 45° F. 2" 2 cub. in. of oxygen per gallon. The processes for the determination of the dissolved oxygen are all, with one exception, beyond the reach of the Medical Officer of Health, requiring complex apparatus and consuming more time than he can afford. The method described in A. Proust's TraiU cV Hygiene, p. 427, is the only one which can be suggested as at all suitable for him, if he desires to launch out into the unknown on this new branch of water analysis. A copy of a trans- lation of the manuscript notes of M. Gerardin, who with Schiitzenberger invented this process, have been kindly sent to me by Mr. J. W. Slater. A solution of the hydrosulphite of soda is made thus : — Place some zinc turnings in a 100 gramme flask, and fill it three parts full with water. Add 10 c. c. of a solution of bisulphite of soda, of a specific gravity of 1*16 (which should have been saturated with sulphurous acid by passing a current of this gas through NATURE OF THE ORGANIC MATTER 87 it for several hours).^ Insert a caoutchouc stopper and agitate several times. In half an hour the re-agent is ready. The liydrosulphite of soda differs from the bi- sulphite only by an atom of oxygen. In presence of free oxygen it instantly absorbs this body and is converted into the bisulphite SaOaNaOHO -f- O2 = S^O^NaOHO There are colouring matters, such as " Coupler's soluble aniline blue," which are instantaneously decolourized by the liydrosulphite of soda, though they resist the action of the bisulphite. For instance, if to a litre of water well freed from air by boiling, and coloured faintly with Coupler's blue, we add dilute liydrosulphite of soda, avoiding access of air, we shall observe that a few drops are sufficient to destroy the colouration. If, on the contrary, the water is aerated, the decolouration is not produced until enough liydrosulphite has been added to absorb all the. dissolved oxygen. If the solution of liydrosulphite of soda were capable of being preserved, it would be merely requisite to determine once for all the volume of oxygen which a known volume of the liquid can absorb ; but, in consequence of its great instability it is necessary to standardize the solution every time before its employment. This is easily effected by the decolouration which the liydrosulphite of soda produces in a solution of the ammoniacal sulphate of copper, as it reduces cupric oxide to cuprous oxide. Bisulphites and sulphites are without action on the solution of copper, as long as there remains an excess of ammonia. We prepare then a strongly ammoniacal solution of sulphate of copper containing 4-471 grammes of the crystallized salt per litre, 10 c. c. ^ Sulphurous acid gas is prepared by allowing pure sulphuric acid to act on clean copper cuttings, and must be washed by passing it through a small quantity of water. Vide any book on chemistry. 88 THE DETERMINATION OF THE AMOUNT AND of which solution having the same action upon the hydro - sulphite of soda as 1 c. c, of oxygen. Suppose that we take 20 c. c. of this ammoniacal copper solution, and find that 17 '5 c. c. of the solution of the hydrosulphite of soda are needful to bring the blue solution to a colourless state. We know that the 20 c. c. correspond to 2 c. c. of oxygen. If a litre of the water to be examined, slightly tinted with Coupier's blue requires 36-4 c. c. of the solution of the hydrosulphite of soda to be decolourized, we have — x = 36-4x2 ^ ,.,,,. ^ = 4'16 c. c. of oxygen dissolved per litre oi water. 17-5 There remains a small correction to be applied for the quantity of hydrosulphite of soda needful to decolourize the Coupier's blue employed, which may be determined once for all. This process is marvellously sensitive. If two portions of the same water are taken, and one is poured boldly into a beaker whilst the other is allowed to flow quietly down the side of a beaker, the two will show a decided difference. The testing should be per- formed in a vessel which exposes as little surface to the air as possible, stirring must be minimized, and a little light petroleum oil or pure mineral naphtha may be poured on to the surface to exchide oxygen. Dr. Tidy has made a few observations on Thames water ^ which show that the oxygen in solution during the winter months (November to April) is very nearly double the amount held in solution during the summer months (May to October), being 2-19 in the former case and 1'19 cub. in. per gallon in the latter, the least oxygen being thus present during the months of the greatest organic purity. ^ " River "Water," Joiornal of Chemical Society, vol. xxxvii. 18S0. NATUKE OF THE ORGANIC MATTER 89 Dr. Dupr^ has also made similar observations^ on the Dr. Dupre's Thames water at various points from Eichmond towards tiojjg' the sea. Permanganate of Potash Test. Teddington Weir matter. filter. CHANGES IN ANIMAL ORGANIC MATTER 93 3. To some salt of ammonia existing in the strata through which the water rises ; or, 4. To the decomposition of nitrates in the pipes of the well. Mr. H. Slater suggests that the agent concerned in this reduction may, in the case of the deep well waters, be the sulphide of iron which is found in the clay. Ammonia may be converted into nitrates and nitrites by a process of oxidation, or be obtained from these salts by one of reduction. We conclude, then, that the presence of free ammonia in such comparatively large quantities in these deep well waters is due to the reduction of nitrates and nitrites by sulphide of iron, or some kinds of organic matter, or some other agent, such oxidized nitrogen salts having been produced in past ages by the oxidation of organic matter. In the case of deep artesian wells, the borings of which pass through the London clay into the chalk beneath, the nitrates that, by reduction, furnish the waters of these wells with free ammonia, doubtless come from the chalk itself. Sometimes a pure deep well water containing a minute quantity of free ammonia may be found within a few yards of another deep well water equally pure, which exhibits a large excess, the difference between the two wells being only one of depth and strata perforated : — Water. Grs. FEB Gall. Paets per Million. Haedness. Solids. Chlorine. Free Amm. Alb. Amm. Well 175 feet deep ,, 50 „ ,, 106-4 98-0 37-7 36-6 •01 •63 •0-2 •01 9^5 4-5 Mr. AVanklyn formerly regarded with suspicion a water yielding a large quantity of free ammonia, along with •OS part per million of albuminoid ammonia. The above analyses of deep weU waters, which are 9-i DETEEMIXATIOX OF MIXEEAL PRODUCTS FEOM renowned for purity throughout all the country in which they form centres, prove that he was wrong. In the fourth edition of his Water Analysis he shows that he has discovered his mistake, but he altogether omits to make any allusion to his error, or to the indi- vidual who not only privately but publicly pointed it out to him.^ He thus signalizes his conversion on page 131 : — " Well 230 feet clee^j at Blaclfriars. Date. Grains per Gallon. Milligramme per Litre. Solids. Chlorine. Free Ammonia. Alb. Ammonia. July 20, 1876. 57- 10-2 •80 ■05 This water exhibits what is occasionally found, namely, a large quantity of free ammonia in pure deep spring water of the first class." Mr. Allen of Sheffield has fallen into a similar error. He writes,^ " It is not unusual to find a very large proportion of ammonia in the water of very deep wells. In the great majority of instances it is associated with an excessive proportion of chlorides — a fact which points to sewage or urine as the original source of the con- tamination." Both statements are correct, but the con- clusion arrived at by him is altogether wrong. Mr. Wanklyn has accordingly altered his standard of rules by changing the wording of one of his sentences. In the previous editions we read, " I should be inclined to regard with some suspicion a water yielding a con- siderable quantity of free ammonia, along uith '05 part of albuminoid ammonia per million." In the fourth edition he 1 Yide Water Analysis for the Medical edition, p. 18. 2 Public Health, February 9, 1877. xcer of Health, first CHANGES m ANIMAL ORGANIC MATTER 95 writes, " I sliould be inclined to regard with some suspicion a water yielding a considerable quantity of free ammonia, along with more than "05 part of albuminoid ammonia per million," — a very material difference. The mode of estimating the quantity of free ammonia in a water is described on page 40. 2. XlTROGEN AS NiTRATES AND ISTlTRITES. The controversy between Dr. Frankland and Mr. mtrates Wanklyn concerning their respective modes of water ^"'^^.^^ analysis has waged very much around the question as to the value of an estimation of the amount of these salts in a water. Whilst the former appears to give a pre- ponderating weight to the indications afforded by the past history of a water, and seems to consider that the determination of the mineral products of the animal pollution of a water affords the key to the whole situa- tion ; the latter denounces, in the strongest terms, all reliance on the presence, in any quantity, or absence, of these products of the oxidation of tilth. Mr Wanklyn says,^ " It cannot be too strongly insisted upon that the nitrates afford no data of any value in judging of the organic quality of a water ; " and again, " The pro- gress of investigation has completely discredited the nitrates as criteria of unwholesomeness."^ The pupils of these analysts follow very closely in the paths of their respective teachers. Dr. Hill of Birmingham, in his Eeport for 1876, which contains a sheet of the analyses of waters from 114 different private wells, shows that he forms an opinion of each water solely from the amount of the products of oxidation, such as nitrates and nitrites, coupled with the proportion of chlorides, without ^ Oj}. cit. Fourth edition, p. 84. - Hart's Manual of Public Health, p. 309. 96 DETERMINATION OF MUSTERAL PRODUCTS FROM ever attempting to estimate the quantity of organic nitroo'en, and oro;anic carbon contained in each. Mr. Thomas, public analyst of Cardiff, also states that if he found nitrates and chlorides in excess, and knew that this excess could not be ascribed to the peculiar character of the strata from which the water was derived, he should not determine the organic carbon and nitrogen unless required to do so, but would immediately condemn the water. This exclusive reliance on the evidence vouch- safed by the chlorides and nitrates is to be found in Dr. Cameron's Manual of Hygiene. On page 71 he writes, " In a soft water, remote from the sea, the decided presence of chlorine and nitric acid should be considered as clear evidence of previous sewage pollution, and such water should be regarded as dangerous to health." G. W. Wigner, F.C.S., also writes thus,-"- " There are many cases where a sample of water must be condemned on the evidence of nitrates, nitrites, and the microscope only." Whilst one leader is at one extreme, the other is at the opposite. Looking at the matter judicially, apart from all preferences for either of these rival processes, and governed simply by the results of a large practical experience of all kinds of water, I should say that the truth lies midway, — " Media in res tutissimiis ibis." Dr. Erankland, although falling into the mistake, whilst judging a water, of making his decision almost entirely rest on the degree of previous sewage contami- nation, and the amount of nitrates and nitrites, makes the following statements,^ with which we must all agree. In the presence of oxygen the nitrogen of animal matters is transformed, in great part, into nitric and ^ Sanitary Itecord, October 19, 1877. ' Rivers Pollution Commission. — Sixth Report. CHANGES IN ANIMAL ORGANIC MATTER 97 nitrous acids ; and these, by combining with the basic substances always present in polluted water, are in their turn converted into nitrates and nitrites. The change is most rapid and complete when polluted water passes through aerated soil. Whilst the oxidation of animal matters in solution in water yields abundance of nitrates and nitrites, vegetable matters furnish under like circumstances mere traces, or none, of these compounds. The late Mr. Stoddart, Analyst for Bristol, directed Bristol attention in the Analyst of March 1878, page 212, first, 37pp[y_ to the abundance of diatoms in the Bristol water supply, secondly, to the production of ammonia by their de- composition, and thirdly, to the origin of nitrates from the ammonia thus formed. Notwithstanding the large quantity of diatoms, the amount of these products of their decay is insufficient to raise the insignificant pro- portions of the ammonia and nitrogen as nitrates when diluted with such immense volumes of water as are contained in the reservoirs. Upland waters, which have been in contact only with mineral matters, or with the vegetable matter of uncultivated soil, contain, if any, mere traces of these salts ; but as soon as the water comes into contact with cultivated land, or is polluted by the drainage from farm- yards or human habitations, nitrates in abundance make their appearance. The presence of nitrates and nitrites in sufficient quantity is therefore trustworthy evidence of the previous pollution of the water with animal matters. Nitric and nitrous acids are present in minute quantity in the air, out of which the rain washes them. In 71 samples of rain water collected at Eothamsted, near St. Albans, the proportion of nitrogen, as nitrates and nitrites, varied from nil up to '03 grain per gallon. The largest amount, which occurred only once, was exceedingly small. H 98 DETERMINATION OF MINERAL PRODUCTS FROM Waters which, it is well known, cannot be defiled by manure or by sewage, never contain nitrates in a pro- portion bringing them near to the "point of contamination." The average amounts of oxidized nitrogen found by the Elvers Pollution Commissioners ^ in the pure waters of the various geological strata are as follows : — Nitrogen as Nitrates and Nitrites. Eain Grain per Gallon. •002 Upland Surface Water. (From Non-calcareous Strata.) From Igneous Eocks ...... „ Metamorpliic, Cambrian, Silurian, and Devonian Rocks ..... „ Millstone Grits .... (From Calcareous Strata.) .From Mountain Limestone „ Lias, Trias, and Permian Rock „ the Oolites .... Deep Well Water. In the Coal Measures .... New Red Sandstone the Chalk ,, ,, below London Clay Devonian Rocks and Millstone Grit the Lias ..... ,, Oolites ..... ,, Hastings Sand, Greensands, and Weald Clay Spring Water. From Granite and Gneiss Rocks „ Devonian Rocks and Old Red Sandstone ,, New Red Sandstone ,, the Lias .... ,, ,, Hastings Sand and Greensand „ Silurian Rocks „ Mountain Limestone „ Millstone Grits and Coal Measures ,, the Oolites „ „ Chalk 1 Ojy. cit. •001 •004 •007 •008 •007 •03 •14 •5 •4 •05 •2 •3 •4 •1 •07 •5 •2 •3 •2 •12 •16 •24 •28 •27 CHANGES IN ANIMAL ORGANIC MATTER 99 The Ohjcdions of Mr. Wanklyn and those, who think with him, to the Determination of Nitrates and Nitrites, may he thus summarized : 1. Nitrates find their way into waters from the various oi^jections ,., 1-11 f> Tin*° ^^® s^^ti- geological strata which they traverse ; lor example, chalk mation of springs, which contain an infinitesimal amount of organic ^^!^|;^^*^®^^^'^*^ matter, are often highly charged with nitrates. 2. The processes of vegetation in rivers and lakes are calculated to withdraw nitrates from the water ; accord- ingly, an absence of nitrates may be due to a rife aquatic growth as well as to absence of sewage. 3. Eaw sewage is said to be free from nitrates. The examples adduced in support of these statements prove nothing. If we examine seriatim the objections themselves, we shall find that they amount to very little. 1. Nitrates are found in excess in certain pure waters Answers to from the chalk, but the largest amounts discovered do 1!^^ °^'^®'^' ' o tions. not generally exceed "7 grain per gallon, an amount which would simply throw suspicion on the water of a shallow well, or of a spring, if this result was confirmed by other evidence. Knowing this peculiarity in the waters of deep wells in the chalk, namely, that they possess an excess, and sometimes a large excess, of nitrates, the objection falls to the ground. 2. It is perfectly true that vegetable life assimilates these salts, and so removes them, especially in spring and summer. Accordingly, their amount will then show a slightly more favourable result than really exists during the quiescent months of the year. This optimist indica- tion in the growing season appears to be a very feeble objection, especially when it is remembered that the estimation of the nitrates and nitrites is only one of several data on which an opinion of a water should be based. 100 DETEEMINATIOX OF MINERAL PEODUCTS FROM 3. In undiluted sewage putrefaction rapidly occurs, during wliich process the nitrates are destroyed.'^ I cannot consider this as a valid objection. Utility of the Estimcdion of Oxidized Nitrogen Scdts. utility of the The presence of an excess of these salts in a water tionof^°^ affords no indication, taken by itself, that such water Nitrates and (Reserves Condemnation, nor does the complete absence of nitrates and nitrites warrant any one in pronouncing a water to be pure. Some of the purest waters, such, for example, as those from deep wells in the chalk, contain much nitrates, which have aptly been termed fossil organic matter, or the skeleton of sewage ; whilst waters so full of vegetable matter as to be injurious to health may not contain a vestige of them. The estima- tion of the amount of these salts not only teaches us, as to whether the soil from which the water is derived is clean or defiled with filth which it has oxidized,^ but, taken in conjunction with other e^ddence, it affords valu- able aid to us in the formation of an opinion. Although the water of a well far away from any chalk may be found to be organically pure, yet the presence of any large quantity of nitrates and nitrites, which are, so far as our knowledge extends, harmless in themselves, informs 1 Some believe tliat in sewage, nitrogenous organic matter is destroyed •without the formation of niti'ates, the nitrogen being evolved in the form of gas ; whilst others consider that when sewage is allowed to stand, a process of fermentation occurs, and as this subsides, oxidation commences with the formation of nitrates and nitrites at the expense of the organic matter and the ammonia. ^ The contrast displayed by samples recently sent to the author of the water of the River Jordan, which contains a mere trace of nitrogen as nitrates and nitrites, and that of the Pool of Siloam, which holds in solution more than 22 grains of nitric acid per gallon, whilst each water exhibited between 30 and 40 grains of chlorine per gallon, is very striking. CHANGES IN ANIMAL OEGANIC MATTER 101 US tliat the water is in imminent danger of pollution. This discovery tells us that the natural oxidizing process of cleansing and purification by the soil is proceeding. Experience teaches us that ■ a tune will come, and we know not how soon, when the soil will become overdone with filth, and will, at first imperfectly, and at length finally cease to, cleanse by filtration the polluted water, when the organic matters will themselves enter the well ; or the organic animal filth may be washed into the well at any moment by a sudden downfall of rain. The presence, then, of these salts, in considerable proportion, in shallow well waters, in non- chalky districts, is an ominous sign. A public analyst has recently written : — " Nitrates in a deep well water represent fossil excreta, but nitrates in a shallow well water represent recent excreta." The former part of the sentence is true enough, but the latter is misleading. I have known shallow well waters in chalky districts, that could not possibly have been defiled, exhibit an excess of nitrates. There exists a widely spread dread lest the poisons of diseases, be they soluble or in the form of micro-organisms or of infinitesimal insoluble particles, may survive the almost complete oxidation by earth of dead organic matter, and may co-exist with nitrates and nitrites in a water devoid of any excess of organic matter.^ Some, ^ This fear has recently been very forcibly expressed by Dr. Ashby and Mr. Hehner ("On So-called Previous Sewage Contamination," in Analyst, April 1883), with resxiect to waters from the surface wells, 7 or 8 to 20 or 25 feet in depth in Derby and Newark-on-Trent. These waters come from the variegated marl of the trias, the marlstone rock-bed of the middle lias, and the chalk. They seem as a class to be notorious for high solids, an excess of nitric acid, phosphoric acid, sulphuric acid, and chlorine associated with a comjmratively small amount of free ammonia and albuminoid ammonia. Some soils soon lose the power of oxidizing filth, especially if overdone with it; whilst others may be converted into a nitre bed, and still retain the property of carrying on this purify- ing change. 102 DETERMIlSrATION OF MINERAL PRODUCTS FROM indeed, believe that water from a well within a yard or two of a cesspool cannot possibly be pure. I have known several wells in clay soil, varying in distance from one to live yards from cesspools, which have supplied water of the greatest purity, their safety being due to the retentive properties of the clay, and the water-tight con- dition of the cesspools. I am acquainted with a family that has for years, without apparent ill effects, been drinking water from a well in porous gravelly soil, within two yards from an enormous cesspool, which is evidently not water-tight. The water is organically pure, but con- tains between 1 to 2 grains per gallon of nitrogen in the form of nitrates and nitrites. Highly dangerous of course it is to drink such water, for the well may be defiled, or the earth may cease to act as an efficient filter, at any instant. The curious spread of typhoid fever at Lausen, in Switzerland,^ by water that had passed through an immense thickness of earth, has excited the suspicion that the poison of enteric fever may possibly be a soluble Prof. Mai- rather than an insoluble particle. Under the supervision let's experi- £ p £ Mallet a numbcr of natural waters believed ments m tlie United to be good and wholesome, including the regular water states u o supply of some of the principal cities of the United States, were arranged together as class 1 ; and a number of natural waters, which there was fair ground for beliei-ing had actually caused disease on the part of those drinking them, were arranged as class 2. Both series of waters were examined by the Frankland Combustion process, by the Wanklyn, Chapman, and Smith process, and the Letheby and Tidy permanganate process, with this result — "No marked difference exists between the highest, loivcst, or average result obtained by any of the processes for the waters of class 1 and the corresponding ^ Beitriige zur Untstehimgsgcschichte cles Typhus und zur Trinhwasser- lehre. — Yon Dr. A. Hauler. CHANGES IN ANIMAL ORGANIC MATTER 103 result for those of class 2. No one could, with these figures to guide them, refer a water of unknown origin to one or other of the two classes on the evidence afforded by chemical analysis, using either or all of the processes in question." On examining these same waters for nitrates and nitrites " we find a very obvious connection between the results of chemical examination and the known sanitary character of the several waters, the salts of nitrous and nitric acid being either absent or present in but trifling amount in waters of class 1, believed to be wholesome ; whilst they were almost universally present, and in many cases in large quantity, in the pernicious waters of class 2." Griess has expressed ^ a strong opinion as to the unfitness of water for drinking purposes which contains nitrates and nitrites. Dr. Angus Smith writes,^ " the presence (of nitrates) shows that the most dangerous state of the organic matter is past. The water may, however, be still dangerous to use." Ekin states that^ " waters which have undoubtedly given rise to typhoid fever have been found by the writer over and over again not to contain more than '05 part of albuminoid ammonia in 1,000,000, and which, notwithstanding their containing a large excess of nitrates, have been passed by analysts of undoubted ability as being fit for drink- ing purposes." E. Haines of Philadelphia has pub- lished * cases which partially corroborate the opinions of Mr. Ekin. Here is an analysis of a well water kindly sent to me Examples, by Dr. Armistead, of the Cambridgeshire district, which would have been j)assed as pure if sole reliance had ^ Ann. d. Chem. u Pharni. cliv. 336. 2 C'/iemic(«? iVcics, September 3, 1869. ^ " Potable Water." ^ " Methods of judging of the wholesomeness of Drinking Water," from Journal of the Frankland Institute, February 1881. 104 DETERMINATION OF MINEKAL PKODUCTS FROM been placed on the indications afforded by the Wanklyn, Chapman, and Smith process : — Grains per Gallon. Milligramme per Litre. Clilorine. 4- Free Ammonia. •14 Album. Ammonia. •06 The amount of clilorine did not exceed the average for the neighbourhood. Suspicions were aroused when the well was found to be near a churchyard, and oxides of nitrogen were sought for. These filth products were found in abundance, and a considerable quantity of phosphates were also discovered. Here is another example of a water that would have been deemed, if trust had solely been placed on the amount of free and albuminoid ammonia, to be of indif- ferent quahty, but passable : — Free ammonia Albuminoid ammonia Milligrainme per Litre = Part per Millon. •005 •10 Chlorine in excess, but not above the average of the pure waters in the vicinity. Nitrogen, as nitrates and nitrites, 3*7 grains per gallon. This water came from a well which proved, on inquiry, to be situated in a highly dangerous place. Such a water, exhibitmg so large a proportion of nitrates and nitrites, deserved condemna- tion. Here is a third analysis, of the water from a well 25 feet deep, w^hich, as regards its organic contents, would be pronounced of the utmost purity : — Grains per Gallon. Milligramme per Litre. Solids. 23- Chlorine. 2-2 Free Ammonia. •01 Alb. Ammonia. •04 As there was an excessive brilliancy about the water, CHANGES IN ANIMAL OEGANIC Mx\.TTER 105 my suspicions were aroused ; so I examined the water for nitrogen in the form of nitrates and nitrites, of which I found I'll grains per gallon. My opinion, ex- pressed to the applicant, was that the water was pure at the time of analysis, but was in great danger of pollution ; that the soil cleansed the water at present, but would cease to do so after a certain period, when filth would enter the well. The applicant then informed me that there was a cesspool two or three yards from the well. How would the Wanklyn, Chapman, and Smith process, unaided by the estimation of the nitrates, have enabled me to see the danger ahead, and sound the note of warning ? The analyses made by the late G. W. Wigner of the water supply of Clactou on Sea,^ where the proportion of free ammonia and albuminoid ammonia was very low, whilst the amount of nitrates was high, and the micro- scope disclosed the presence of numerous particles of decomposed muscular fibre, etc., are of interest in con- nection with the subject under consideration. Many additional instances could be given, if space permitted, to show the value of an estunation of the nitrates, but such must surely be unnecessary. The omission to pay any regard to the amount of nitrates and nitrites in a water is practically to ignore the infiltration of filth into a water supply that is not very recent. It is not needful in every case to make a cpiantitative examination of the nitrogen as nitrates and nitrites. If any doubt exists after estimating the amount of free ammonia, albuminoid ammonia, and chlorine — if one's diagnosis is somewhat obscured by any curious results — if, indeed, there is the slightest haze or mist in connection with an analysis, it is wise to calculate the quantity of ^ Sanitary Record, August 31, 1877. 106 DETERMINATION OF MINERAL PRODUCTS FROM nitrates and nitrites. I should not think of making an estimate of these salts in the water of a spring, far removed from any filth, that is always running, or in an artesian well water, respecting both of which there existed no suspicion, and both of which showed infinitesimal amounts of free and albuminoid ammonia. In Dr. Armistead's analysis the numbers of these two kinds of ammonia afforded a suspicious indication; and in the analysis which immediately follows it, the quantity of albuminoid ammonia, coupled with the knowledge of the dangerous position of the well, would have led me to test for salts of nitrogen. Qualitative. A. QUALITATIVE EXAMINATION. The Horsiey The HoTsUy Test. — The directions given by the dis- "^*^^*' coverer of this test are as follows : — Take a large sized conical test glass holding about 1-|- or 2 oz. of the water to be examined, and dissolve in it, by the aid of a glass rod, about 1 grain of pyrogallic acid. Measure out 1-|^ or 2 fluid drachms of pure, strong sulphuric acid. The test glass containing the water and pyrogallic acid being held in the right hand and its edge depressed, carefully pour down the side of the vessel the sulphuric acid, which will lie as a layer underneath the water. Drop gradually into the water a pinch of salt. When the salt reaches the sulphuric acid, effervescence takes place which mingles the upper and lower layers, giving rise in the lower layer to a more or less purplish violet or black colour, according to the quantity of nitrates. Nitrites, if present, will show themselves in the upper layer by pro- ducing a yellowish or even brown tint indicative of nitrous acid in a gaseous state, which gradually disappears {vide fig. 11). Twice distilled water remains colourless when treated as above. CHANGES IN ANIMAL ORGANIC MATTER 107 Nttrites Nitrates Dr. Bond of Gloucester practises the following modi- fication, which is preferable: — 20 minims of pure sulphuric acid are placed in a very small test tube, to which 1 minims of the water to be examined are added. One drop of a solution of pyrogallic acid (10 grains to 1 ounce of distilled water acidulated with 2 drops of sulphuric acid) is then dropped into the mixture. The depth of the dark amethyst or vinous brown coloration is a measure of the amount of the salts present. It is wise to make one or two blank experiments with twice distilled water, when fresh chemicals are employed, so as to be assured of their purity. After allowing the colour to develop for a few minutes, the contents of the test glass should be shaken, so as to mix the sulphuric acid with the water, and no opinion should be formed as to the water under examination until a quarter of an hour has elapsed after such com- 108 DETERMINATION OF MIXEEAL PRODUCTS FEOM mingling has been effected. It will be found useful to keep some spring water, or other waters containing known quantities of nitrates or nitrites, ready at hand, with which to make comparisons.^ It is stated that if nitrates are alone present, the tints will be of an amethyst and dark brown hue, whilst the exclusive existence in a water of nitrites is shown by a preponderance of a reddish brown or vinous red colour. This Horsley test is found to convey very useful informa- tion to those who make a study of it, and is especially convenient in travelling, as it does not involve the conveyance of any cumbrous apparatus, A portable and safe arrangement may be made by fitting up a small box with the following articles : — Pure strong sulphuric acid in a capped stoppered tube bottle enclosed in a vulcanite tube case ; solution of pyrogallic acid in a capped dropping bottle ; stoppered test glasses, each marked by a file to indicate the height reached by 20 minims of sulphuric acid : and a minim measure. Nitric Acid or Nitrous Acid ? The occurrence of nitrites in springs and deep well waters, otherwise unobjectionable, is without significance ; for their presence indicates the result of a reduction by some mineral substances or ancient organic matter of nitrates into nitrites and ammonia. The determination 1 The Medical Officer of Health may find it convenieiit to prepare a few standard waters, made by mixing J gr. , ^ gr. , 1 gr. , 2 grs. , 3 grs. , and 4 grs. of nitrate of potash, each with a gallon of distilled water. Mr. Horsley makes standards by dissolving 1 grain of nitrate of ammonia in 100 drops of distilled water and adding the solution in different quantities to 16 ounces of distilled water thus : — 5 drops to 16 ounces of distilled water = ^ gr. per gallon. 10 „ „ „ =lgr. 20 „ ,, ,, =2 grs. CHANGES IN ANIMAL ORGANIC MATTER 109 of nitrites in river waters is of little value, for tliey often derive these salts from the manure applied to the arable land which they drain. It is sometimes desirable, in the case of shallow well waters that are threatened with pollution, to ascertain whether the oxidized nitrof^en is in the form of the higher oxide, viz. nitric acid, or the lower oxide, viz. nitrous acid. If all the combined nitrogen is in the form of nitrates, which contain an atom more of oxygen than nitrites, we know that a complete oxidation of the organic matter has occurred. If the nitrates are accompanied by nitrites, we learn that this oxidation is imperfect, and not thorough. Lastly, if the nitrites abound, we conclude that contamination is near at hand, that the soil is over- done with filth, and that it is only able very imperfectly to cleanse the water. These are the broad lessons learnt by making a discrimination between these two oxides of nitroo-en. Nitric Acid. Kitric Acid. Brucine Test. — Evaporate 2 c. c. of the water to be examined in a small Berlin dish, about the size of a watch glass, to dryness over a spirit lamp. Add one drop of strong pure sulphuric acid to the saline residue. Endeavour, as far as possible, to bring the drop in con- tact with all the saline residue by tilting up the dish. Allow the smallest crystal of brucine to fall on the drop. If nitric acid be present in even the minutest quantity the drop of sulphuric acid will become pink, and after- wards of a yellow colour. The late Prof. Parkes says,"^ " Half a grain of nitric acid per gallon gives a marked pink and yellow zone." "•01 grain per gallon can be easily detected." Prof. Sanders, who represents to some extent the ^ Manual of Practical Hygiene. Fifth Edition. 110 DETERMINATION OF MINERAL PRODUCTS FROM opinions of his German fellow-countrymen, considers^ that a water to be deemed pure should contain no appreciable amount of nitric acid. Nitrous Acid. Potassium Iodide and Starch Test. — Boil a little powdered starch in distilled water so as to form a thin solution. Place a little of the water to be examined in a test tube, and add about 5 minims of a solution of potassium iodide, free from iodate (5 grains to 1 ounce of distilled water), and a little of the cold starch solution. Pour into the mixture a few drops of pure sulphuric acid. If the water contains nitrous acid or nitrites, a blue colour will be produced, in depth of tint proportioned to the amount present. Permanganate of Potash, as described on pages 34 and 35. Meta-phcnylene Diamine is a more delicate test, since it is capable of detecting one part of nitrogen in ten million volumes of water. A solution of sulphuric acid should be prepared by mixing one volume of strong sulphuric acid with two volumes of distilled water. Half a gramme of meta-phenylene diamine should be dissolved in 100 c. c. of distilled water, decolourized if necessary by passing it through animal charcoal, and rendered acid with sulphuric acid. 1 c. c. of each of these solutions is added to about 100 c. c. of the water to be examined in a Nessler glass. If nitrous acid be present a yellow colour is produced, the depth of tint being proportioned to the amount present. The chief objection to this test is that the development of colour is slow, the final shade not being reached for twenty minutes. 1 Sandbiich der offentUchen Gesundheitspflege. Leipsig : Hirzel. 1877. CHANGES IN ANIMAL ORGANIC MATTER 111 A still more delicate test for nitrous acid exists, which enables one part of this acid to be detected in 1,000^000,000 parts of water, and which has been employed in air analysis {vide page 357). B. QUANTITATIVE EXAMINATION. Quantitative. Experience has shown me that it is of no practical service whatsoever for sanitary purposes — in fact a waste of time — to estimate to the third decimal point the amount of nitrates and nitrites ; for such extremely accurate results should not influence our opinion respecting a water in one way or the other. Dr. Erankland and his followers exaggerate the importance of the determina- tion of minute amounts of these salts. The majority of them subtract from the figures which they obtain •0224 grain per gallon, as an allowance for the amount of inorganic nitrogen in rain water. The average total amount of ammonia, nitrates, and nitrites in a pure upland surface water is "0077 grain per gallon, or practically nil. Dr. Erankland would then make a deduction of "0224 grain per gallon on account of the ammonia in rain ; or, in reality, more than the total quantity of inorganic nitrogen contained in this pure water. There is, as we all know, a strong tendency in nature to the establishment and maintenance of an equilibrium. Eoughly and generally, it may be said, that the excess of inorganic nitrogen that may find its way into the soil, and into streams and lakes, through the washing-out of the ammonia in the air by rain, is compensated for by the abstraction of the ammonia by vegetation on land, and the removal of the nitrates and nitrites by aquatic plant life. The quantitative processes for the estimation of the 112 DETERMINATION OF MINEEAL PRODUCTS FROM nitrogen products of the oxidation of organic matter are very numerous. The aluminium process of Schultze (modified by Chapman and Wanklyn) and Walter Crum's process with mercury (as modified by Frankland and others), and the indigo process, have been perhaps the most popular. The objection to the first is, that it is useless for waters containing large quantities of nitrates ; and the objection to the second is, that it necessitates the employment of large and costly apparatus for the measure- ment of gases, and an expensive mercurial bath. The third process is still employed, although grave doubts have been thrown on its accuracy. A number of sanitary analyses were some years ago published,-^ in which the estimation of the nitrates would seem to have been made by means of the indigo process. The experience of myself and some others with it has been most unsatisfactory, on account of the difficulty in obtaining concordant results. As some, however, entertain a belief in its value, it is perhaps desirable to refer to it somewhat in detail. Fischer,^ Boussingault, Marx, Trommsdorff, Goppelsrceder, and Bemmelen, have worked particularly at this indigo process in various ways, but the most recent mode of applpng it is that described by Sutton.^ An investigation has also been made at the Eothamsied Laboratory as to the value of the indigo process,^ which appears to have been of an exhaustive character, A few extracts from the papers referred to may advantageously be given, " The method of running indigo from a burette ^ "On the "Water Supply of Seaside Watering-Places," by tlie late G. W. Wigner, F.C.S., in Sanitary Record, commencing in jSTo. 165, August 24, 1877, and appearing in subsequent numbers. - Journ. Pract. Chemie. (2) vii. 57. ^ Volumetric Amdysis. ^ "On the Quantitative Determination of T^'itric Acid by Indigo," by Robt. Warington, in Chemical News, February 2 and 9, 1877, and in Journal of Chemical Society, 1879, vol. xxxv. p. 578. CHANGES IN ANIMAL OEGANIC MATTER 113 into a nitrate solution mixed witli a fixed quantity of sulphuric acid can never yield reliable results." " The tints obtained differ somewhat according to the proportion of sulphuric acid used, the mode in which it is added, and other circumstances : the presence of chlorides also affects the colour." After pointing out that nearly all the purest distilled oil of vitriol that is sold contains either nitrous acid or sulphurous acid and other reducing im- purities, and sometimes both of these acids, and that it is necessary for the operator to himself purify his oil of vitriol, the author writes : — " The various writers on the subject, from Marx to Sutton, all recommend the use of a double volume of oil of vitriol. We have seen that with this large proportion of sulphuric acid the errors caused, both by organic impurities and by impurities in the acid itself, are at their maximum. Evidence has also been adduced to show that with this proportion of acid the indigo scale has not the same value in every part. Chlorides tend to reduce the amount of indigo required." Notwithstanding these warnings of its fallacious indications published in 1878, it was employed in the Governmental inquiry conducted in 1880-81 by Dr. Cory, to the results of which is appended the following sentence : — " The presence of albumen in the water in- terferes with the indigo test and prevents it from indicating the true amount of nitric acid present." The proceedings of the Society of Public Analysts of February 16, 1881, informs us that Dr. Dupre spoke very strongly of " the failure of the indigo method in certain waters " and of the probability that it broke down in nearly every case. " It broke down entirely in the presence of urine in water and almost entirely with albumen in water." A study of the researches at Eothamsted cannot fail to render any one a convert to the conclusion of Mr. Warington and his fellow- workers respecting the indigo I V. Har- court and 114 DETEEMINATION OF MINERAL PEODUCTS FEOM process as it has been and is applied, namely, that "it can only be exact under very exceptional circum- stances." Vernon Harcourt's process for the estimation of nitrogen siewerfs in uitratcs, which has been modified by Siewert,-*^ of zinc- process. ^^^^ couplcs and caustic potash, is not adapted for sanitary work. The determination of nitric acid by means of its reaction with ferrous salts,^ and by means of the platinum magnesium couple,^ are two of the most recent methods. The copper-zinc couple process, and the sulphophenic acid process of MM. Grandval and Lajoux, to be presently described, are to be recommended in preference to all others. Modification of Thorji's Process for the Estimation of the Nitrogen as Nitrates and Nitrites. Modification Thorp's proccss for the estimation of these salts is process.^ ^ bascd ou the fact discovered by Dr. Gladstone and Mr. Tribe, that a thin plate of zinc, coated with copper, de- composes water, and that the hydrogen evolved is capable of reducing nitric acid in combination into nitrous acid and then into ammonia. NO3K + 4H2 = NH3 + HKO + 2H2O The apparatus, as depicted in the accompanying engraving (fig. 12) is first cleaned with tap and afterwards with distilled water. Five grammes of the thinnest zinc foil, which has been thoroughly cleansed from all grease, cut with a scissors into little squares about the size of a 5 -centi- gramme weight, are then placed on a piece of paper ready ^ Sutton's Volumetric Analysis. - R. "Warington (1882). Trans. Chem. Socy., xli. 345. 3 F. P. Perkins (1881). Analyst, April, p. 58. CHANGES IN ANIMAL OEGANIC MATTER 115 for use. Some strong^ solution of sulphate of copper (made by dissolving the pure salt in distilled water) is introduced into a flask of the capacity of ^ litre, or 1 deci-gallon, provided vfith a long neck and thick strong mouth for the insertion of an india-rubber cork. The quantity of the solution should be sufficient to cover the fragments of zinc foil when they are introduced. The solution should be gently warmed over a Bunsen's burner, Pig. 12. a. Flask. 6. Condenser — medium size. c. Receiver, whicli resembles a very large Nessler glass, provided with an india- rubber cork. d. U Tube containing 25 c. c. of distilled water. e. Bunsen burner with chimney. and the bits of zinc foil should then be passed into the flask. The zinc should not be allowed to float on the solution. A gentle swaying motion will suffice to cause them to sink. Let the copper solution act on the zinc for about ten minutes, when the scraps of zinc will have become perfectly black by the copper deposited on them. A copious firmly adherent coating of black copper is desirable. If the zinc has not entirely lost its metallic ^ The Society of Public Analysts recommends the employment of a three per cent solution. 116 DETEEMINATION OF MINEEAL PRODUCTS EKOM appearance, the solution of sulphate of copper has not acted on it sufficiently long. Spongy flocculent masses of copper, easily detached from the zinc by washing, will be noticed if the exposure of the zinc to the solution of copper has been too long. When the zinc is well coated with copper, pour off the copper solution as completely as possible. Fill up the flask with tap water three or four times, stopping for a moment on each occasion in order to allow floating particles to subside, and pouring the water away carefully so as not to lose any of the couple. Then half fill the flask with distilled water, and having poured that away also, add about 300 or 325 c. c. of distilled water. The flask will then be about three-parts full. It is not wise to shake the contents of the flask about more than is needful to wash them thoroughly, for violence tends to detach the spongy coating of copper from the zinc. Whilst these preparations are being made, 70 c. c. of the water to be examined should be undergoing evaporation to dryness on a water bath in a Berlin porcelain dish of the diameter of 4 inches. 25 c. c. of distilled water is to be added to the solid residue, together with a bit of recently burnt quickhme (preserved in a stoppered bottle) about the size of a hempseed, and the liquid is then boiled (to decompose any urea which may present) until about 4 or 5 c. c. remain. Care should be taken in boiling that none of the fluid be ejected from the dish. Pour these 4 or 5 c. c. into the flask, and thoroughly wash out the dish in which the water was evaporated with as little distilled water as possible, trans- ferring the washings, which generally amount to 15 or ■20 c. c, to the flask. If the presence of a large excess of nitrogen salts is probable, a U tube should be attached to the receiver, into which 25 c. c. of distilled water have been placed. Distil over 100 c. c, of which a half (50 c. c.) should be placed in a ISTessler glass and 2 c. c. of CHANGES IN ANIMAL ORGANIC MATTER 117 Nessler test be added. If the tint is deeper than can conveniently be measured, as for example that of "30 or •40 milligramme of ammonia, take 5 or 10 c. c. of the remaining 50 c. c, and having mixed them with 45 or 40 c. c. (so as to make 50 c. c.) of distilled water in a Nessler glass, add 2 c. c. of Nessler test. The depth of tint should be imitated by making up standards with the standard ammonia solution (1 c. c. = -01 milligramme of ammonia), as in the Wanklyn, Chapman, and Smith process. If the tint afforded by the 50 c. c. is not deeper than can be conveniently estimated, the amount of ammonia producing it is simply to be multiplied by 2 to yield the quantity for 100 c. c. If 5 c. c. or 10 c. c, however, be taken, the result should of course be multiplied by 20 or 10, as the case may be, in order to obtain the quantity contained in the 100 c. c. Whilst this calculation is proceeding a second 100 c. c. is distilling over, which should be treated like the first. During the examination of the second 100 c. c. a third distillate is passing into the receiver. Unless there is a large amount of nitrogen salts present the third distillate need only be 50 c. c, and this quantity will be found to be the last that it is necessary to remove in the majority of cases, as all the ammonia will have distilled over. If the U tube has been employed, the 25 c. c. of distilled water in it should be mixed with an equal bulk of distilled water in a Nessler glass and tested for ammonia with Nessler re -agent. If any colour is produced, which will be the case if the nitrates and nitrites be very abundant, the proportion should be measured by preparing a standard. Before this process is employed for the determination of the nitrogen as nitrates and nitrites, it is necessary to ascertain the amount of impurities in the chemicals used. Ammonia, like soda, is omnipresent. It is exceedingly 118 DETERMINATION OF MINERAL PRODUCTS FROM difficult to get anything perfectly free from either. Ac- cordingly, three or four blank experiments should be made, and an average of the amount of free ammonia yielded by the chemicals must be subtracted from the results arrived at by each analysis of a water. The above-mentioned quantities of my chemicals furnish about •06 of a milligramme, which I deduct from each water analysis, for example — 70 cub. cents, of the water analysed supplied. (1) Distillate of 100 c. c. . -85 (2) Distillate of 100 c. c. . '02 (3) Distillate of 50 c. c. . '01 Average of error ■06 •82 Milligrammes. ATiiinonia. Ammonia. Nitrogen. 171 '82 14 328 82 Nitrogen. 17)ll-48( -67 102 141 128 119 9 Ans. •GT milligramme of nitrogen in 70 c. c. of water under examination, which is equivalent to '67 grain per gallon. As 70 c. c. is what has been termed "a miniature gallon," the amount in milligrammes of nitrogen from nitrates and nitrites thus found represents the quantity of this element in grains per gallon. An expeditious modification of this process has been 1 The atomic or combining weights of ammonia and nitrogen. CHANGES IN ANIMAL ORGANIC MATTER 119 suggested ^ by M. W. Williams, and recommended by m. w. the Society of Public Analysts, which cannot, unfor- ^^^^^"^^^^3 tunately, be employed in the case of waters exhibiting mode of em- any tint in a ISTessler glass, nor with those containing^ °^™^" ' magnesia or other substances capable of being pre- cipitated by the Nessler re-agent. After washing the zinc and copper couple with distilled water, which should be displaced by washing with some of the sample of water,^ the wide-mouthed stoppered bottle containing the couple is filled up with about 3 or 4 oz. of the water under examination. The stopper is then inserted, and the contents of the bottle are allowed to digest in a warm place for a few hours, ^ or over night. If the water is soft, a little salt quite free from ammonia (1 part to 1000) should be added to hasten the reaction. As the nitrous acid formed by the reduction of the nitrates does not disappear until the reaction is finished, a small portion of the fluid contents of the bottle, acidified with sulphuric acid, should be tested with a solution of meta-phenylene diamine, which gives a yellow colour in a few minutes if nitrous acid is present (vide page 110). When no nitrous acid is found, the water is poured off the couple into a stoppered bottle, and, if turbid, allowed to settle. From 2 to 10 c. c. of the clear fluid are withdrawn in a graduated pipette and placed in Nessler glasses, where they are made up to 50 c. c. with distilled water, and titrated with Nessler re-agent in the ordinary way. 1 Analyst, Marcli 1881. ^ Dr. R. B. Lee always at this stage adds -5 gramme of oxalic acid (free from ammonia and nitric acid), in. order to precipitate the lime and to form an insoluble compound with the zinc. ^ If the bottle be maintained in a water bath at a temperature of from 55° F. to 60° F., the reduction will be rapid, and will be found to be com- pleted in from 1^ to 2 hours ; the employment of oxalic acid permitting the elevation of the temperature without loss of ammonia. 120 DETERMINATION OF MINERAL PRODUCTS FROM A deduction must of course be made for the ammonia pre-existing in tlie water under examination. MM. Grandval and Lajoux's Process for the Determination of Nitric Acicl.'^ Grandval Tliis proccss is bascd on the change of carbolic acid into Proc^sf'^^'^ P^^-"^^^ acid under the influence of nitric acid, and on the intensity of colour exhibited by the picrate of ammonia. A solution of sulphophenic acid, and a titrated solution of nitrate of potash are necessary. The sulphophenic re-agent is prepared by mixing Grammes. Carbolic acid, pure ... 3 Acid sulphuric . . . 37 40 The titrated solution of nitrate of potash is made by dissolving '9 3 6 gramme of this salt in 1 litre of dis- tilled water. 1 c. c. of this solution contains "0005 gramme of nitric acid or "0001 gramme of nitrogen. Method. — 10 c. c. of the water to be examined are evaporated to dryness in a porcelain dish over a water bath. The dish is allowed to cool, and an excess of sulphophenic acid is added. This re-agent should be led by the help of a glass rod around the sides of the dish, so that no particle of the residue may escape its in- fluence. A few cubic cents, of distilled water are poured into the dish, followed by an excess of ammonia. We should continue to add ammonia until the yellow colour produced does not disappear on stirring with the glass rod. This solution of picrate of ammonia is diluted with distilled water so as to bring it to a volume suitable for the colorimeter employed. "VVe operate in the same way on a certain quantity of ^ C'ovij^tes Rcndus, July 6, 1885. CHANGES IN ANIMAL ORGANIC MATTER 121 the titrated solution of nitrate of potash, taking care to bring the sokition of the picrate of ammonia obtained to the same volume as that of the water under examination. In the analysis of a drinking water, which a qualitative test, such as Horsley's P}Togallic acid test (vide page 106), has shown to be exceedingly pure, it is wise to employ only 1 c. c. of the titrated solution of the nitrate of potash. If the public water supply from one of our cities or towns is to be submitted to examination, in which a qualitative test points in the direction of purity, it is advisable not to employ more than 2 or 3 or 4 c. c. of the titrated solution which we evaporate to dry- ness, in either case bringing the volume operated on up to 10 c. c. by the addition of distilled water. It is some- times convenient, in order to be able to judge within certain limits of the amount of the titrated solution of nitrate of potash which should be operated upon, so as to arrive at a colour similar to that of the water under in- vestigation, to keep in store standard solutions of nitrate of potash of difierent strengths and depths of colour. I am in the habit of using as a colorimeter a pair of Hehner's tapped graduated Nessler glasses, and in cases where there is no need for great acccuracy they answer well. The details of this process may advantageously be inserted. Suspecting a water under treatment in my laboratory whilst writing these lines to be an impure one, as much as 10 c. c. of the titrated solution of nitrate of potash were evaporated to dryness. 10 c. c. of the water to be examined were also evaporated to dryness. The residue of each was treated as above directed. The solu- tion of picrate of ammonia in each dish was then diluted up to the 5 c. c. mark in the colorimeter. The 5 c. c. of titrated solution exhibiting the darker colour, as much as 30 c. c, were run off by the tap, and the remaining 20 c. c. exactly equalled in depth of tint that of the 5 c. c. 122 DETERMINATION OF MIXEEAL PRODUCTS FROM of tlie water under examination. It will be remembered that 10 CO. of titrated solution of nitrate of potash ('001 gramme of nitrogen) were contained in the 50 c. c. of titrated solution in the tapped Nessler glass. e.c. of titrated ^a4tt tofo^^l^ ^^f ^^r^e Gnunme ^°^- water under examination. "^ ^^- °^ '■^• 50 : 20 :: -QOl = '0004 The 50 c. c. of the water under analysis equal, therefore, 20 c. c. ("0004 gramme of nitrogen) of the 50 c. c. of the titrated solution of nitrate of potash. As only 10 c. c. of the water under examination were operated on, this "0004 gramme of nitrogen must be multiplied by 1 to ascertain the amount of nitrogen in a litre — •0004 X 100 ■0400 gramme per litre of nitrogen. X 70 2 "80 00 grains per gallon of nitrogen as nitric acid. I learn that this method, which is more rapid than that of the copper zinc couple, is highly approved of by American analysts. There are two objections to it : (1) that it entails the employment of ammonia, which should be rarely, if ever, used in a laboratory where processes for its detection and estimation in water and air are in frequent operation ; and (2) that the addition of sulphophenic acid to the residue of a water which contains a considerable amount of nitric acid is attended by the evolution of peroxide of nitrogen or nitrous acid, which is thus lost. Rules for Cruiclance. Spring waters contain on an average "2 grain per CHANGES IN ANIMAL ORGANIC MATTEE 123 gallon of nitrogen as nitrates and nitrites. The water supplied to London by the Thames "Water Companies possesses about "15 grain per gallon, whilst that which is furnished to the metropolis by the Kent Company from the chalk, holds in solution about '3 grain per gallon. Some wells that enter the chalk yield a larger amount, viz. : — "6 and •? grain per gallon, and sometimes much more of nitrogen as nitrates and nitrites, in other words, of fossil organic matter, and are, notwithstanding, per- fectly pure. When, however, from "3 to '7 grain per gallon is reached in waters that do not come from the chalk, the excess becomes an increasingly suspicious circumstance. A water exhibiting 1'5 grain per gallon is regarded as approaching that class of waters which would be considered dangerous for drinking purposes. Peaty waters and sewage contain none, or only a minute quantity. Examples. Sample of Water. NiTEOGEN AS Nitrates and Nitrites. Grains per Gal. Well, P.B.R Art. Well, O.P.S. . Art. Well, J.T. Well, R.H.S.AV. Spring, G.H.G.B. . Gray's Water, Brentwood. 1-11 ■09 8-47 2-55 •26 •67 CHAPTEE lY THE DETEEMINATION" OF THE AMOUNT OF SOLID EESIDUE, ITS APPEAEAXCE BEFORE, DURIXG, AXD AFTER IGXI- TIOX, AXD THE LOSS OF VOLATILE MATTERS THEREBY OCCASIOXED. A. The Amount of Solid Eesidue. B. The Appearance of the Sohd Eesidue Before, During, and After Ignition. C. The Amount of Volatile IMatters burnt off by Ignition. A. TJu Amount of Solid Residue or Scdine Matters. The mineral constituents conduce in conjunction with dissolved air and carbonic acid gas to render a water palatable. Eain water and distilled water, which are almost destitute of the same, are notoriously flat and insipid. The saline matters have been improperly called by some " soKd impurities." Dr. Frankland, who was the originator of this unfortunate expression, defends its use by stating that the solid matters in water are " quite useless." A medical man would not make such an assertion, un- supported as it is by any trustworthy evidence known to the profession. He adds, " A very large proportion of the potable water supplied to towns is employed for washing and manufacturing purposes, and here the presence of a large amount of solid matter giWng hard- ness to tlie water is undoubtedly injurious."^ This 1 Rivers Pollution Commission. — Sixth Sej.ioii, p. 5. LOSS OF VOLATILE MATTEES AFTEE IGNITION 12i sentence must not lead to the inference that waters characterised by an excess of salts are always hard. Strongly saline waters are often very soft, as for example the waters of many artesian wells. Highly saline and hard waters are admitted on all hands to be extremely undesirable as supplies to towns, and are especially objected to for washing and business purposes. The Fig. 13. A. Platinum Dish. B. Beaker containing Water. c. Tripod Stand. D. Bunsen's Burner. E. Coarse Wire Gauze, on which. a pipe triangle rests to support the beaker. F. Thick bit of paper between Dish and edge of Beaker, to permit of escape of steam. excess of salts in such cases may perhaps be termed impurities, but it is ridiculous to speak of the small quantities of saline matters in the purest (organically) spring waters as impurities ! To estimate the amount of solid residue at 212° F. proceed thus : — Weigh an empty platinum dish of 100 c. c. capacity, place it over a water bath, and pour into it 25 c. c. of the water to be examined. Evaporate to dryness. Wipe the outside of the dish quite dry. Again weigh the dish 126 AMOUNT OF SOLID EESIDUE, ITS APPEAEANCE, promptly to avoid the error from deliquescence of salts. For example : — Dish and residue . 26*240 grammes. Dish . . . 26-232 Weight of residue . '008 As 25 c. c. are a quarter of 100 c. c, multiply the result bj" 4, and then, to arrive at the number of grains per gallon, multiply by 700 thus : — ■008 4 •032 700 22-400 The water contains 22-4 grains per gallon. It was formerly the practice to evaporate 100 c. c. or 70 c. c. of the water to dryness. If 70 c. c. are selected, the result exactly represents the number of grains per gallon. Time is however saved in the analyses of several waters by employing a smaller quantity of water. The objection has been raised that the experimental error, inseparable from all analytical operations, would fall rather heavily on such a small quantity as 25 c. c. I have found, without taking any extra care, a variation of 1 grain per gallon in the results obtained by taking the large and the small amount, a difference of not the slightest practical importance. It is quite immaterial, from a sanitary point of \dew, whether our drinking water contains 22-4 or 23-4 grains of saline matters per gallon. Physicians well know that a water in which a mode- rate quantity of salts is dissolved (medicinal waters ad- ministered with a specific object, and for a limited period AND LOSS OF VOLATILE MATTERS AFTER IGNITIOX 127 only, are of course excluded from consideration) is better than one possessing an excess ; for the constant imbibi- saiine tion of fluids strongly impregnated with saline substances '"^^"g"^*^ tends to diminish the richness of the blood, and to render some people anaemic. Although the waters from the artesian wells in Essex contain, as a rule, a very minute proportion of organic matter, yet they hold in solution a large quantity of salts, derived from sand beds beneath, and sometimes alternating with, strata of the London clay. These waters, associated as they are with so large a quantity of saline matters, cannot be considered so whole- some as waters from artesian wells containing a moderate amount of salts, equally free from a deleterious amount of organic matter. I have often seen the ill effects of the continued employment of waters rich in saline matters. Some well waters have been found to contain an enormous proportion of salts. I once analyzed a water from an artesian well which held in solution 341 grains of solids in each gallon ; and have examined waters ex- hibiting the large amounts of 485 grains, and even 795 grains per gallon. Sea water is stated to have 2400 and 2700 grains per gallon of solids. Spring water of the best quality usually contains about 14, 17, 18, or 19 grains per gallon of solid residue. A water should not possess more than 30 or 40 grains per gallon of solids ; but waters holding a larger amount dissolved in them are in certain cases permissible, if the salts are quite harmless. It is gene- rally found, according to my experience, that when a water contains much more than 110 or 120 grains of saline matters per gallon, the public will complain of it as brackish or hard, and refrain from employing it con- tinuously, unless obliged so to do. 128 AMOUNT OF SOLID RESIDUE, ITS APPEAEANCE, B. T]u Appearance of the Solid Residue Before, During, and After Ignition. The eflfect of Miicli may be learnt as to the character of a water gni lou. -j^^ observing the solid residue obtained by the evapora- tion of a w^ater on a water bath to dryness before, during, and after its incineration at a dull red heat ; and very little knowledge is to be acquired by the estimation ot the loss on burning the same. After the calculation of the amount of solids, the appearance of the residue is carefully observed and noted. The platinum dish is then placed on the pipe triangle, which rests on the tripod stand. The smallest sized Bunsen's burner should be lighted, and held by its foot in the hand. The flame should be allowed to play gently to and fro around the bottom and sides of the dish, so as to raise all its contents in turn to a didl red heat. Heat may be conveniently applied in a manner equally gradual and gentle by holding the platinum dish with a pair of laboratory tongs or pincers over the flame. It will be found that — 1. In cases where a water is practically free from any organic matter, and the solids are principally lime salts, there will be no discoloration of the residue during igni- tion. The residue will become whiter, until at length it assumes a clean pearly-white appearance. 2. In cases where the organic matter is small in amount, there is a slight brownish discoloration, which is very fleeting, and passes like a smoky cloud away as the ignition proceeds, leaving the residue of a dirty white or neutral colour. If no charring is observed, and the loss on ignition is very small, that loss is due to the volatiliza- tion and decomposition of saline matters and not to organic matter. 3. When the organic matter is in still larger amount AND LOSS OF VOLATILE MATTEES AFTER IGNITION 129 (especially if it be vegetable) the residue blackens in patches or waves. The colour is more persistent ; and, to dissijDate it, the flame of the Bunsen's burner has to be steadily directed beneath the blackened places. 4. When the organic matter is excessive, the whole of the residue blackens rapidly, even in the upright sides of the dish, evolving a smell of burnt feathers when of animal origin. The colour is extremely persistent, and in some cases it is very difficult, if not impossible, to dispel it by the application of a dull red heat. In bad waters (especially when urine is present) the organic matter disappears from the bottom of the dish, but at the sides there is frequently a black residue which it is extremely difficult to burn off even by prolonged ignition. Dr. Ashby has noticed that, if nitrates are abundant in a water polluted with much organic matter, there will be very little blackening and perhaps not much darkening of the ignited residue. The residues of very bad waters will sometimes defla- grate. The tiny sparks visible are due to the presence of nitrates in excess. An iodized starch-paper, erroneously called an " ozone test," is held over the dish by some during the ignition to detect any nitrous acid that may be given off. Eed fumes are sometimes evolved when these oxidized compounds of nitrogen are large. The employment of the olfactory nerves may also aid us. The smell of burnt hair or horn produced by the destruction of the organic matter is often observed. The development of a strong empyreumatic odour is suggestive of a bad water. The smell of sulphurous acid is not uncommon, in- dicating the presence of sulphur compounds. The residue of a very bad water will sometimes emit an offensive smell on incineration. The observations of Dr. Shea of Eeading on water K 130 TABLE OF ANALYSES, WITIi | Name of Sample of Water. Grains Per Gaxlon. MiLLlGEAilME PER Litre = Part per Million. Degrees. Solids. Chlorine. Nitrogen as Nitrates and Nitrites. Free Anjinonia. Albu- minoid Ammonia. Total Hardness. Public Artesian well at S. 85 •36 •01 Shallow well at B.'s, Gay Bowers 52 9-2 •30 •44 Spring water from clay soil supplying G. H., Great Baddow . 23 2-6 ■26 •00 •03 13 or 14 Shallow well belonging to cottages near " King's Arms," B. 101 12-5 Above 1-0 •24 Peaty spring water 5 1-1 None. •03 •11 2or2i Shallow well of B. P. . 23 2-2 1-11 •01 •04 Artesian well of Mr. P. T. 210 31 8-47 •10 •35 37 Shallow well of Mr. A, E. of G. W. 103 16 Abund- ant. •69 ■28 New public shallow well at G. S. F.— Soil hlne clay and black sand . 89-6 8-2 Very little. •13 •02 32 132 AMOUNT OF SOLID RESIDUE, ITS APPEARANCE, residues agree closely with my own. The late Prof. Parkes has laid down the following rules for the guid- ance of the analyst, on which I could not place much reliance : — " Three grains per gallon of either vegetable or animal organic matter cause some blackening ; six grains per gallon, a good deal; and ten grains per gallon, a great amount. The preceding analyses are not selected for the pur- pose of confirming or verifying the accuracy of the foregoing attempt at rules for guidance, but are taken indiscriminately from my note-book. Instead of being illustrative and typical, they would seem to exhibit some variations. C. The Amount of Volatile matters burnt off ly Ignition. Volatile The amount of organic matter was formerly calculated Matters by burning the dried solids and noting the loss — a most fallacious mode of estimation, — for the water of crystal- lization is driven off, carbonates are decomposed, nitrates and nitrites disappear, and even chlorides ^ if the residue is strongly ignited. This " loss on ignition " has accord- ingly been spoken of as " substances driven off by heat." Speaking generally, impure waters may be said to lose much by incineration, but this statement cannot safely be regarded as an established rule, because the exceptions to it are so numerous. ]\ir. Allen has ex- pressed the opinion that in a good water the loss on ignition is rarely more than one-fifth of the total sohds in weight. Dr. Shea, who has had some experience with silica residues, states that such residues retain water very ■^ An intense yellow colour imparted- to the flame of the Bunsen's burner indicates the volatilization of chloride of sodium. AND LOSS OF VOLATILE MATTERS AFTER IGNITION 133 persistently, and only lose it on strong ignition ; and that an impure water of this class which he encountered lost 55 grains out of 129 grains of solids per gallon. I have known good chalk waters lose 12 and 14 grains per gallon on ignition of the solid residue. If the Medical Ofiicer of Health should decide to ascertain the amount of " substances driven off by heat," he should, when he takes the solid residue, evaporate 70 c. c. instead of 2 5 c. c. of the water to dryness, unless Fig. 14.— a Copper Water Bath. A, Hole for Berlin evaporating dish. B, Hole for platinum dish. C, Tripod stand. D, Aperture of safety tube. N.B. — The insertion of a small piece of paper between one of the dishes and the edge of the aperture on which it rests, suffices to permit of the escape of steam. he possesses a first-rate balance, otherwise small dif- ferences cannot be measured. If the health officer thinks it requisite to estimate quantitatively the amount of nitrogen as nitrates and nitrites, the proportion of solid residue, the quantity of volatile substances, and to note the appearances of the residue before, during, and after the application of a dull red heat, it will be found most convenient to employ a water bath, similar to that used for evaporating milk to dryness, but provided with larger holes, one to hold the 134 AMOUNT OF SOLID RESIDUE Berlin evaporating dish, and the smaller to support the platinum dish. Dr. F. de Chaumont makes the following entry in his hygienic classification of waters : — ^ 1. Pure and Whole- some. Under 1 grain per gallon. Solids on incin- eration should scarcely blacken. 2. Usahle. Under 3 grains per gallon. Solids may blacken a little, but no fumes should be given off. 3. Suspicious. 3 to 5 grains per gallon. Much blackening on incineration, or nitrous fumes given off. 4. Impure. Above 5 grains per gallon. Much blackening and nitrous fumes given off, or smell of burnt horn. Remarl:s. In peat waters tho incinerated solids may blacken con- siderably. The ignited residue in the platinum dish should at the conclusion of the determination of the volatile matters be reserved for the application of the test for phosphoric acid. 1 Parkes' Hygiene, Fiftli Edition. CHAPTER V THE DETERMINATIOX OF THE AMOUNT OF CHLOPJNE The estimation of the amount of chlorine in a water observation is in some circumstances worth little in itself, unless we^^'^°f'^°™'^ I _ _ of chlorine know the amount of organic matter contained in itofiittie The determination of the amount of chlorine in the^^^^p^™^''" water of a district, where an excess of chlorine does not^^ycaieuia- . ,. . , . T :^ tionofquan- occur m all waters, is an mdirect guide as to whether tity of am- or not the water is contaminated with sewage, xjrine™™'^.^"'^ ° organic and sewage possess a large amount of chlorides. The matter. presence of 5 or 10 grains of chlorine per gallon in a water is a suspicious circumstance in such localities. Good natural waters contain, on an average, from '7 to 1"2 grains per gallon. Waters from the greensand formation, and from the London clay, have generally an excess of chlorine, derived from the chloride of sodium and other salts of chlorine in the sand. The waters of Essex, which come some geoio- from layers of sea-sand and clay enclosing marine fossils, ^^^^^JjJ'^** possess as a rule a great deal of chlorine. One artesian waters con- ,.,-r ., ji'.i- , taining an water, which I examined recently m this county, con- excess of tained as much as 103'6 grains per gallon. chiorme. In the neighbourhood of the sea, which is always con- tributing its spray in greater or less quantity to the land, and wherever there are natural deposits of salt, an excess of chlorides is apt to be found. A Medical Officer of Health, whose work is situated in 136 DETERMINATION OF THE AMOUNT OF CHLOKINE a district where waters exhibit an excess, should ascertain, by making a number of examinations for chlorine, the average amount of it in waters from wells of different depths. Some years ago a tube well was sunk at Deal, where most of the wells are brackish. At 25 feet the water was too salt for use, but at 45 feet fresh water was obtained free from brackishness, whilst at 1 1 7 feet it was as salt as brine. If a sample of water holds in solution an amount of chlorine below the average in the district, the probability is that there is no sewage contamination. If, on the other hand, an excess of chlorine is accompanied by an excess of albuminoid ammonia and ammonia, pollution with sewage is almost certain. If sulphates were found to be in very small quantities, the excess of chlorine would be shown to be not due to a pollution by urine, for tliis excretion contains a large amount of sulphur salts. The amount of chlorine is also a guide as to the quantity of the salts of sodium, potassium, and magnesium in a water. It should always be remembered, then, that in all cases the estimation of the amount of chlorine and of ammonia must, to possess any value as a guide to the pollution or otherwise of a water, be taken in con- junction with the quantity of organic matter, and in doubtful cases, with the amount of the nitrates and nitrites. To estimate the proportion of chlorine in a water, we must proceed thus : — Place 70 c. c. of water to be ex- amined in an evaporating dish, and add a minute morsel of neutral chromate of potash (free from chlorine). Then, by means of a pipette gTaduated to ^th of a c. c, and filled with 5 c. c. of the solution of nitrate of silver (vide recipe on page 218), this standard should be allowed to drop into it until the red colour produced ceases to disappear. Directly the red tint becomes permanent, DETEEMINATIOX OF THE AMOUNT OF CHLORINE 137 note the amount of nitrate of silver solution necessary to attain this point. Eun a little more nitrate of silver into the water, to be sure that the water is not acid, for chromate of silver is soluble in acids. I believe the existence of a free acid (non-gaseous) in a water to be rare, for only on one occasion have I found the chlorine test interfered with in this way. In this solitary instance a minute quantity of potash was intro- duced to neutralize the acid, and the fresh sample of 70 c. c. thus treated was operated on. The number of c. c. of the nitrate of silver solution employed will represent the number of grains of chlorine per gallon. A very interesting case has been recorded ^ by Dr. F. de Chaumont, showing the value of the chlorine test in cases where a water has been vitiated by sewage gases. The water of a house in London where typhoid fever had Pollution by , nil. . • 1 psewer gas, appeared was found to contam a large excess oiandfoui " albuminoid ammonia," and but a small amount of P^®°"® ' faacalemana- chlorine. A sample from the reservoir of the company tions. that supplied this house was analyzed, and found to possess an almost identical quantity of chlorine, but an extremely small proportion of "albuminoid ammonia." It was ascertained that the water used in the house was derived from a cistern, and that it was vitiated by the poisonous gases ascending through its overflow pipe from the sewer. On disconnecting the overflow pipe the amount of " albuminoid ammonia " gradually diminished. Dr. Eobert King describes ^ an outbreak of enteric fever in his own family, where the following change took place in the water supply of liis house, in consequence of the contamination of one of his cisterns by sewer gas through its overflow pipe which was in direci communication with a drain. ^ Lectures on State Mcdiciiie, p. 77. " Medical Times and Gazette, August 2, 1879. 138 DETEKMINATIOX OF THE AMOUi\^T OF CHLOFJNE Part per 1 [ILLIOS. Free Alb. Ammonia. Ammonia. Water Supply of House . •010 •060 „ of Cistern . •025 •240 A very clear and brilliant water was recently sent to me by a medical man in attendance on an isolated case of enteric fever in a rural district of Xorth Devon, which, whilst possessing an unpleasant odour, and a large excess of organic matter, contained only 1|- grain of chlorine per gallon, and no nitrogen as nitrates and nitrites. A micro- scopic examination exhibited an abundance of bacteria and micrococci. The water had come from a well, the overflow pipe of which passed into the contents of a garden closet at a lower level, with the evident object of cleansing the same. The water was contaminated by the foul gaseous emanations proceeding from the decomposing faecal matter.^ The discovery of an excess of organic matter, accom- panied by a small amount of chlorine and nitrogen as nitrates and nitrites, coupled with the presence of bacteria and micrococci, would tend to the conclusion, if vegetable contamination is out of the question, that sewage in the solid or liquid form has not been the cause, but that the source of impurity is probably gaseous. ^ Yide Disease Prevention, p. 45. J. and A. Churcliill. CHAPTEE YI THE DETEEMINATION OF THE HAEDXESS The degree of hardness is a matter to be considered in pronouncing on the wholesomeness of a water. The average total hardness of good waters is between 3 and 14 degrees. Some deep artesian wells made in the London clay, extending to the sandbeds lying underneath, and occasionally to the chalk below, furnish water that is excessively soft, from the presence of bicarbonate of soda that replaces the bicarbonate of lime derived from the chalk. The deepest clay strata have doubtless a softening effect on the waters of these deep wells by virtue of the precipitating action of the alumina of the clay on the salts held in solution. Pipeclay mixed with sea water is well known by marines to soften it and increase its cleansing properties. An error has been made by some in judging of the hardness of a water solely by the amount of solid residue contained in it. Mr Wynter Blyth writes,-^ " It is obvious that the soft waters have a small solid residue ; the hard a large. A water with 8 or 10 grains of solid residue is a moderately soft water ; the lake waters, with from 2 to 3 grains of residue, are extremely soft ; whilst those with 50, 60, 70, and 80 grains of saline residue must be hard ; so that any other test, except taking the ^ Did. of Hyrjienc and Public Health. 140 DETERMINATION OF THE HAEDNESS solid residue, is really superfluous." It is j)erfectly true that a hard water will have a large solid residue, but it is quite an error to state that a water possessing a large solid residue will always be hard. Here are examples of organically pure and soft waters exhibiting a large excess of solids : — Wells Solids— Grains per Gallon. Total Hardness— Degrees. Clark's Scale. A. Steeple. B. Do. C. Maldon. D. Tilliiigham. 98 103 84 236 44 5 4 4 70 c. c. of the water to be examined for hardness should be placed in a stoppered bottle, holding about 250 c. c. The standard soap solution is dropped slowly, by means of a pipette graduated to ^^ths of a c. c, into the bottle, which is frequently shaken violently to note the amount of soap solution necessary to create a persistent lather. The stopper of the bottle should after each shaking be removed for an instant to allow of the escape of the car- bonic acid gas which is evolved. If a water is so hard that the addition of 16 c. c. of soap solution does not produce a lather, add 70 c. c. of distilled water, and mix. Then continue the addition of the soap solution. If the dropping of soap solution be proceeded with until a second 1 6 c. c. be consumed, without the formation of a perman- ent lather, a second 70 c. c. of distilled water must be added. Suppose, for example, 19 c. c. of soap solution are necessary : — 19 Deduct for liardness of each. 70 c. c. of distilled water employed ...... 1 Degrees of liardness . . . . . .18 DETERMINATION OF THE HAEDNESS 141 Wlien a water is very hard it is desirable to decant the contents of the bottle into a larger one of the capacity of about 500 c. c. To know the quantity of carbonate of lime, or other hardening and soap-destroying ingredi- ents contained in the water, subtract 1 degi'ee. The water just cited possesses 17 grains of carbonate of lime, or salts equivalent, per gallon. If a water is found to be exceedingly hard, 35 c. c. of it should be placed in the 70 c. c. flask, and the measure filled up to the 70 c. c. mark with distilled water. The quantity of soap solution required to form a lather with this mixture must necessarily be doubled in recording the result. A rough and ready method of determining the hardness of very hard waters consists in measuring 10 c. c. of the water into a 70 c. c. measure, in filling up the same with distilled water, and multiplying the result obtained with the soap test by 7. It is necessary to chstinguish between the false lather, or scum produced by magnesian salts present in the water, and the true persistent lather. Boil a sample of the water for about a quarter of an Permanent, hour (some boil for half an hour), and when cold replace what is lost as steam with distilled water. Allow any floating particles that may be present to subside, and examine it with the soap test. In this manner the permanent hardness is obtained. The difference between the 'permanent and the total Temporary, hardness is termed the temporary hardness. The carbonate of lime waters, such as are employed by large populations in the chalk districts on the south coast of England, lose most of their hardness by boiling. When the hardness of a water is mainly due to the presence of the sulphates of lime and magnesia and chloride of calcium, boiling makes but little difference. There are some grounds for thinking that, whilst the former class of 142 DETEEMINATION OF THE HAEDNESS Influence on wateis are not deleterious to health, and in certain cases possess remedial properties/ the latter class should be objected to if the hardness is excessive. Whilst revising these lines I have been engaged in the examination of a spring water employed by villagers living on the new red sandstone, which possesses a total hardness of 84° and a permanent hardness of 35°! A hard water will sometimes produce for a time diarrhoea, and at others constipation. Dyspeptic symptoms are often complained of by those who have been accustomed to drink soft water on coming into a hard water district. Lumbago and suppression of urine have also been ascribed to the use of such waters. Dr. Murray of Newcastle - on - Tyne gives ^ a terrifying description of the evils resulting in the limestone district in which he lives, from the supply of very hard waters. There is a strong feeling in the medical profession of this, and especially of Continental countries, that there is a connection between the development of certain calculous disorders, goitre, and certain forms of dyspepsia, and the employment of hard waters, but no e^^.dence exists of a very demonstrative character on which this belief rests. Certain it is (1) that soft waters are superior to hard for domestic and manufacturing purposes ; (2) that moderately hard waters are more palatable than very soft waters ; and (3) that of hard waters those which lose much are preferable to those which lose little of their hardness by boiling. Independent of the hygienic aspect of the question, the waste of money and labour is not to be overlooked in the case of town supplies. Each degree of hardness ^ To the hardness of the water supply of Clifton is attributed its beneficial effects in patients suffering from chronic diarrhoea. ^ " On the Influence of Lime and Magnesia in Drinking Water in the Production of Disease." Brit. Med. Journal, September 28, 1872. DETEKMINATION OF THE HARDNESS 143 signifies the destruction of 12 lbs. of the best hard soap by every 10,000 gallons of water. If soap is not employed to soften a hard water, fuel and carbonate of soda are expensive substitutes. CHAPTEE VII THE DETEEMIXATION OF THE A]MOUXT OF ilAGXESIA, SULPHATES, AND PHOSPHATES A. Magnesia — Sulphate, Carl3onate, and Mtrate. B. Sulphates of Lime, Magnesia, and Soda as Anhydrous Sulphuric Acid. C. Phosphates. Salts of magnesia and sulphates are objectionable in waters if in excess. A good water does not possess more than traces of these ingTcdients. Their estimation is sometimes required when the question is raised as to the wholesomeness of a suggested new water supply, or as to the comparative merits of several waters from which it is proposed to select the purest. It cannot be otherwise than a matter of astonishment that so little attention has been paid in the past to the influence on health of the earthy constituents of waters that do not come under the designation of mineral waters. Parisian physicians, although li^dng in a basin of sulphate of lime, appear to be totally ignorant of the effects of this substance on health. A noticeable feature in Dr. Frank - land's sanitary analyses is the complete absence of all re- ference to the amount of sulphates in a water. And yet we know that the presence of an excess of sulphates in a drinking water is often found to be associated with obscure forms of dyspepsia, with obstinate diarrhoea, MAGNESIA, SULPHATES, AND PHOSPHATES 145 alternating with constipation, etc. Selenitic waters in- jurionsly ' affect strangers more than those who are habituated to their use. Some wells furnish water so purgative as to preclude Purgative the possibility of employing them as a regular water supply. I have met with many waters of this kind in Essex. They yield sulphate or carbonate of magnesia. I look upon them in this county, — which contains ague, such a large amount of liver disorders, hsemorrhoidal, and other malarial affections, — as mineral waters of some value. Holding in solution, as they do, not only a pur- gative salt, but a large proportion of other saline matters, they are not wholesome waters for general and constant use. In localities where these mineral waters exist, the people are, for the most part, compelled to drink pond water. Malarial affections are often traceable to the employment of pond water for drinking purposes. These aperient waters may be regarded as in some sense the remedy to counteract the effects of the poison, for they are, in all probability, of great service in congestion of the liver and in hsemorrhoids, by relaxing the j)ortal system of vessels. A. Magnesia — Sulphate, Garhonate, and Nitrate. There are two or three modes of making approximative Magnesia. calculations as to the amount of magnesia in a water, all being similar in principle, for they consist in precipitating the lime with oxalate of ammonia, and then estimating the remaining hardness with the soap test. Boutron and Boudet take 200 c. c. of the sample of water for examination, and add to it the smallest quantity of a clear concentrated solution of oxalate of ammonia, that is sufficient to throw down all the lime, and then they allow the mixture to stand for 24 hours. The water is then boiled for half an hour, and filtered, the loss being re- L 146 DETEEMIK'ATION OF AMOUNT OF MAGNESIA, placed by distilled water. When cool the hardness is determined hj the soap test, and the number of degrees are multiplied by "14, to bring them into grains per gallon. Wanklyn adopts the following plan,-^ which is more rapid, and on that account is preferable, if equally accurate. "Powdered oxalate of ammonia is added to the w^ater in the proportion of one gramme of the oxalate to one litre of the water. The mixture is shaken for a minute, and filtered. Having convinced oneself of the absence of any free acid in the filtrate, and having tested it with a little oxalate to make sure of the removal of the lime, 70 c. c. of the filtrate are triturated with the soap test to ascertain its hardness. If there be any degree of hardness beyond the one degree required by pure water, magnesia is present. Its amount may be calculated by multiplying the remainder, after the deduction of the one degree, by the fraction ^^, which will give the quantity of carbonate of magnesia per gallon of water." It should never be forgotten, in employing the soap test, that a certain lapse of time is required for the pro- duction of the lather when the hardness is due to magnesia, whilst in that occasioned by lime the lather is immediately observable. As examples of the amount of magnesia in potable waters, the following analyses, which have been published by Wanklyn and Playfair, may be cited : — Name of Waters. Grains per Gallon. Total Magnesia in terms of Carbonate of Magnesia. Croydon Water Sunderland Water Thames New River Company Kent Company Buxton Water }J 1-4 9-46 1-10 •76 1-56 4-5 1 02^. eii. SULPHATES, AND PHOSPHATES 147 B. Anhi/drous Sulphuric Acid {SO ■^) from Sulphates. The amount of these salts may be roughly estimated suiph thus : — Acidulate a large test tube full of the water to be examined with two or three drops of hydrochloric acid, and then add a small quantity of a solution of chloride of barium. If there is a precipitate, the amount of sulphuric acid exceeds one grain per gallon. If there is a precipitate after standing, there is at least 1-|- grain per gallon. 3 and 4 grains per gallon give immediately a turbidity differing in degree according to the presence of the lesser or the greater amount. Practice with waters to which known quantities of sulphates have been added will soon enable the Medical Officer of Health to form rough estimates. When it is desirable to calculate the exact amount of sulphuric acid as sulphates, it is conveni- ently done in either of the following ways : — The method which I practise is the following : — About 10 c. c. of a strong solution of chloride of barium are placed in a beaker, and then acidified with a few drops of pure hydrochloric acid. 70 c. c. of the water to be examined are added, and the contents of the beaker are boiled, the precipitate being allowed to settle for two hours. Then the supernatant liquid, and finally the turbid liquid below, are filtered off. The very best Swedish filter -paper is required, otherwise the filter will not remove entirely the sulphate of baryta. The pre- cipitate may be thoroughly detached from the sides of the beaker by the aid of the feather of a quill pen. Wash out the beaker with hot distilled water. The washings are to be passed through the filter until the fluid that drops from the funnel leaves no residue when evaporated on a platinum spatula or foil. Allow the filter to drain, and dry it gently by suspending the funnel on a retort ring at some distance above a lighted spirit lamp. Ignite 148 DETEEMIXATIOX OF AMOUA^T OF MAG^'ESIA, the filter in a platinum crucible and weigh. The differ- ence between the weight of the empty crucible, and the weight of the crucible and its contents minus the weight of the ash of filter/ furnishes a number of milligrammes that represent grains per gallon of sulphate of baryta, which should be recorded in terms of anhydrous sulphuric acid, e.g. — BaS04 Araouut of SO3 ' — , — ' BaS04 found. ' — , — ' 233 : -004 :: 80 80 Crucible and its contents 17-776 Crucible . 17-770 •006 Deduct weight of ash of filter . -002 233Y3200/-001; /233 \ 870 -004 699 171 Besult. — Eather more than 1 milKgramme, or 1'3 gr. of anhydrous sulphuric acid per gallon. Houzeau's method ^ is a very simple and perhaps a more rapid one. Prepare a solution of barium chloride 30-5 grammes in a litre of distilled water. Obtain a dropping tube which furnishes 25 drops for each c. c. To 10 c. c. of the water to be examined after acidifying with one drop of acetic acid, add 2, 4, 6, 8 or 10 drops of the barium chloride solution by means of the dropping tube. "Wait for 3 minutes and if a deposit is formed, filter the liquid. The filtrate is to be treated with one or more drops of the barium chloride solution. If a deposit ^ The average weiglit of ten filter -paj^ers should be estimated and marked on the packet. The labour of weighing each filter-paper when employed is thus avoided. The ash is about \ per cent the weight of the filter. If, for example, the filter weighs 400 milligi'ammes, the weight of the ash will be 2 milligrammes. ^ Com2}tes Rcndus, Ixxxvii. 109. SULPHATES, AND PHOSPHATES 149 is noticed after an interval of 3 minutes, the liquid is again poured on tlie filter. The addition of diminishing quantities of the barium chloride solution is repeated, until the filtrate ceases to exhibit the faintest cloud after an interval of 3 minutes. Water employed 10 c. c. + 1 drop of acetic acid. Solution of Cliloride of Barium. First Addition 16 drops. Second 5) 2 „ . Third 5) 1 „ . Fourth 5) 1 „ . Fifth •>■> Total drops 21 (Abundant deposit.) (Notable turbidity.) (Feeble turbidity.) (Very feeble turbidity.) (No cloud at the end of 3 minutes.) Total drops used 20 Deduct i drop from fourth addition "5 19 '5 drops. As 1 drop = "485 milligramme of anhydrous sulphuric acid, 19 '5 drops x '485 = 9"46 milligrammes. Hence a litre of water contains "946 grammes or 6 6 '2 grains per gallon of anhydrous sulphuric acid. The following list (page 151) will afford some idea of the remarkable differences exhibited by various kinds of water in respect to the amount of this mineral ingredient. The water of the well in Hutton is avoided by the occupants of the cottages to which it belongs, on account of its purgative properties ; whilst that from the well at ]\Iountnessing is occasionally used after boiling. Both of these wells are shallow, and are situated in the London clay formation. 150 DETEEMINATION OF AMOUNT OF MAGNESIA, Of the Metropolitan waters, that of the Kent Com- pany is objected to hj some on the gromid of the excess of sulphates. As much as from 20 to 70 grains of sulphates per gallon have been found in some drinking waters in Dublin by Dr. Cameron. A water may exhibit a large amount of magnesia and but a very small quantity of sulphates, that alkaline earth being in the form of carbonate, as for example, in the waters of the dolomite formation. I have examined well waters, pure as to organic matter, containing 4-|- grains per gallon of sulphuric acid in the form of sulphate of lime, but have not felt warranted in publicly expressing disapproval of the use of such waters for drinking purposes. If samples of water were brought to me in order that I might select the best, I should certainly at the outset place a water containing this amount of sulphates out of competition. We have very little reliable information as to the effects of these salts in drinking water on the health, but that they must have a very decided influence admits of no doubt. Can it be a matter of no moment from a public health point of view whether people are drinking water containing 100 grains per gallon, as at IMount- nessing, or "5 of a grain per gallon, as at Croydon, of anhydrous sulphuric acid from sulphates ? I have never yet seen a person who habitually employs a drinking water containing a large amount of sulphates that could be regarded in any sense by a medical eye as " a picture of health." C. Fhosjjhatcs. hosijiiates. When we remember the important role played in the human organism by phosphates, and in how many SULPHATES, AND PHOSPHATES 151 Names of Waters. Sulphuric Acid (SO3) from Sulphates. Grs. per Gal. Spiring in Admiral's Park, near Chelmsford Essex ..... Spring in Trinity Lane, Springfield, Essex Spring supplying Grove House, Great Baddow Essex . iManchester water Sunderland water Croydon water . The Rhine at Bonn Clareen well, Carrick-on-Suir Do. river do. Public pump, Waterford Pump at University Club, St. Stephen's Green Dublin Flooded stream, Holmfirth, Yorkshire Moors Carlisle Waterworks AVater of shallow well in Rose Valley, Brent wood .... Water of deep well, Stanwix, Carlisle Fountain water from High Town, near Halt whistle .... Water from pump in Rutherford's Court Stanwix, Carlisle Pump in yard. Prospect Place, Stanwix The water of the river Ouse, near York, on September 1, 1876 The .water of the river Ouse, near York, on September 6, 1876 . Water from shallow well of Jeffrey's Endowed School, Great Baddow, Essex Water from well at Brentwood Hall, Brent wood ..... Water from Maldon Waterworks Water from well at Little Burstead Water from well in IMountnessing Water from well in Hutton Water from well at Hutton Railway Bridge / Grand Junction Thames I ^^^^^^ Middlesex . Water < Southwark and Vauxhall . Companies. | Chelsea \ Lambeth . ( Kent Other J j^Tp^^, Ri^-er ^"™P^'"^^- I East London 1-.3 5-8 2-7 1-1 •93 •5 1-4 1-2 ■9 17-76 49-4 •87 1-5 4-54 3^79 •81 10^57 4-03 4-3 1-58 16^36 3-13 4^51 64^5 100-0 182-0 2-7 1-5 1-47 1-43 1-52 1-56 2-82 1-05 1-59 Pi'oposed as public supplies. f Closed, as I it caused -I diarrhoea I and V dyspepsia 152 DETEEMINATION OF AMOUNT OF MAGNESIA, different forms they occur in the various parts of the body, it is a matter of great interest to study the relation between the use of waters emanating from phosphatic strata, and the condition of health of those who employ them.^ The presence of an excess of phosphates when they cannot thus be accounted for is often due to sewage impregnation. Tiemann has noticed phosphates in large quantity in the water derived from marshy meadows. Mr. Wanklyn states,^ that " much nonsense has been talked about phosphates in drinking water." " Carbonate of lime and phosphates are incompatible in drink- ing water." Dr. Dupre has affirmed that he never examined a water in which he could not detect phos- phoric acid. In Prof Kubel's Treatise on Water Analysis, edited by Dr. Tiemann, is to be found the follow- ing description of the mode of testing for phosphoric acid : " Boil the water ; the precipitate contains the phosphates; dissolve this precipitate in hydrochloric acid ; evaporate to dryness, and heat for a short time a little over 212° F. Then dissolve in a little hydro- chloric acid and water, filter, and add filtrate to a slightly warm clear solution of ammonium molybdate and nitric acid, when a yellow colour and precipitate occur." The nitric acid employed should be of the greatest purity, and free from all colour. If the phosphates 1 Mons. Joly, in an interesting paper to one of tlie Parisian scientific societies, says that the importance of the phosphates in the animal economy may be measured by tlie fact that five diff'erent phosphates are found in the body : in the red blood corpuscles, phosphate of iron ; in the liquor sanguinis, phosphate of soda ; in the nervous system, phosphate of potash ; in the muscles, phosphate of magnesia ; and in the bones, phosphate of lime. In each case the phosphoric acid fulfils very difi"ereut functions, according to the bases with which it is united. 2 O}}- cit. SULPHATES, AND PHOSPHATES 153 are in very small proportion, the water should be concentrated by evaporation previous to the analysis. Dr. Diipre in the experiments undertaken by the Local Government Board in 1880-81, already referred to, em- ployed the following qualitative method: — The solution of the total dry residue obtained in the estimation of solids was "warmed in nitric acid, after filtration, with a strongly acidified solution of molybdate of ammonia." The Society of Pubhc Analysts thus describes the Method of plan which it recommends : " The imited total residue ^^'^L^^^i^^^ f o of Public is to be treated with a few drops of nitric acid, and the Analysts, silica rendered insoluble by evaporation to dryness.-^ The residue is then taken up with a few drops of dilute nitric acid, some water is added, and the solution is filtered through a filter previously washed with dilute nitric acid. The filtrate, which should measure 3 c. c, is mixed with 3 c. c. of molybdic solution ^ gently warmed, and set aside for 15 minutes at a temperature of 80° F." The amount of phosphoric acid in phosphates found is generally recorded either as "traces," "heavy traces," or " very heavy traces." ^ Dr. Asliby suggests the removal of the contents of the platinum dish to a porcelain one before evaporation to dryness, as this metal is dissolved in the presence of chlorides. ^ " One part pure molybdic acid is dissolved in 4 parts of ammonia (sp. gr. •960). This solution after filtration is poured with constant stir- ring into 15 parts of nitric acid of 1-20 sp. gr. It should be kept in the dark and carefully decanted from any precipitate Avhich may form." CHAPTEE VIII THE DETEKMINATIOI^ OF POISONOUS METALS The poisonous metals which water analysts are called upon to consider are lead and copper. The occurrence of arsenic, zinc, tin, and barium, etc., in drinking water, is so rare as to hardly merit the attention of the health officer. In the Afghanistan campaign of 1839 there was a large mortality amongst the British detachment stationed at Ali Musjid, which was ascribed to the strong impregnation of the water with antimony. Lead and copper are usually the poisonous metals, especially the former, with which waters are liable to be contaminated. A water sometimes contains iron, which is of course undesirable in all cases, except for medicinal purposes, and hurtful in some. Place 7 c. c. of water to be examined in a porcelain dish, and stir it with a glass rod moistened with sul- phuret of ammonium. Note whether or not there be any coloration. If so, it may be owing to a sulphuret of iron or lead, or of copper. If, on adding two or three drops of hydrochloric acid, the brown colour dis- appears or diminishes, iron is present, for the hydro- chloric acid dissolves the sulphuret of iron. If, on the other hand, the colour does not vanish or diminish on this addition, lead or copper is present. It matters not which, for both are equally injurious. "Wanklyn writes, DETERMINxVTION OF POISONOUS METALS 155 " If there be coloration," on introducing the sulphuret of ammonium, " it should only be ju.st visible, and on adding two or three drops of hydrochloric acid, it ought to vanish absolutely." AVater which answers to this test in a satisfactory manner is registered as sufficiently free from poisonous metals, and water which does not, is to be condemned as contaminated with metallic impurity. If the quantity of either of these metals in a water be required, it is necessary to employ standard solutions, containing one milligramme of each metal in each cub. cent, of its solution (made by dissolving 1'66, 3 "9 3, and 4' 9 6 grammes of crystallized acetate of lead, or sulphate of copper or proto-sulphate of iron in a litre of distilled water); and, if we desire to ascertain whether lead or copper be present, it is needful to operate on a larger quantity of water, and to work according to the directions in that distinguished chemist's exhaustive treatise on water analysis. The above simple mode of testing for poisonous metals -is sufiicient for the Medical Officer of Health, for it enables him to say that a water contains less than jljth grain of lead or copper per gallon, an amount which should condemn a drinking water. Water is considered to be admissible for domestic purposes if containing "I" grain of iron per gallon, but the presence of one grain of this metal per gallon is deemed to be sufficient to justify its rejection. The French chemists consider that the amount of iron should not exceed '2 1 grain per gallon in a potable water. Medical literature teems with instances of poisoning by lead and copper. It is curious to note the timidity with which Cornish miners look upon waters issuing from strata known to contain metals, and how they altogether ignore the risk of drinking water contaminated with filth of the filthiest description. 156 DETEEMIXATIOX OF POISONOUS METALS Lead. LccLcl. — The actlon of different kinds of water on lead forms a very large subject, -whicli cannot here be even briefly adverted to. Lead poisoning sometimes occurs when the water of a well is verj soft and free from saline ingredients, in consequence of its action on the leaden pipe that descends into it from the pump, and through which it is raised. This danger does not exist in the case of highly saline waters, for the salts so encrust the leaden pipe as to prevent the solution of the lead by the water. Lead pipes should never be employed in wells. It has been pointed out to me by Dr. Ashby that waters from the oolitic-limestone district in which he lives do not act on lead, owing to the protective action of the traces of phos- phoric acid contained in them. Several of the Yorkshire cities, such as Sheffield, Huddersfield, Eochdale, and Keighley, are reported to suffer fi'om impregnation of their water supjDly with more Sheffield or Icss lead. A very excellent report on that of Sheffield siiMi^y has recently been issued by Dr. Sinclair A^Tiite, the Medical Officer of Health, who found that a portion of it furnished by certain springs supplied to a particular section of the city was acid and contained an amount of lead varying from "07 to '7 grain per gallon, from which the water supply of the remainder of the city (derived from another source) was free. He attril:)utes the acidity either to ulmic and humic acids from the decomposition of peat, or to sulphuric acid produced by the oxidation of the iron pyrites contained in the shale underlying the moorland peat, from which the former or " high level " supply proceeds. He suggests that a protective property be imparted to the water by passing it for fifteen minutes over small fragments of limestone. An approximation to the proportion of lead present in a water may be arrived at by means of ]Mr. Wynter DETERMINATIOISr OF POISONOUS METALS 157 Blytli's cocliineal colour test/ but the exact quantity is calculated by the author in the following simple manner. Take two Nessler glasses graduated into c. c. and pre- cisely alike. Place 70 c. c. of the water under examina- tion in one, and 50 or 60 c. c. of distilled water into the other. Let them rest on a wdiite slab. Introduce a glass rod dipped in ammonium sulphide into each. If any lead is present in the water, a brown colour is developed. ]\Iatch its depth by adding to the distilled water, by the help of a burette graduated into cub. cents., a standard solution of acetate of lead (1'66 grammes of crystallized acetate of lead to 1 litre of distilled water of which 1 c. c. = 1 milligramme of lead) in sufficient quantity to exactly match the tint. Bring the volume of the diluted standard up to the 70 c. c. mark, and then make a final comparison. The number of cub. cents, of the standard lead solution employed represent the number of grs. of lead in a gallon of water. Iron. — The plan recommended by Dr. Tidy^ for the iron, detection of iron and for ascertaining the form in which it is present is as follows : — Fill 3 tubes (each 2 ft. long) cr. Tidy's with the suspected water ; into one («) place a drop or jxe^hof'^ ' two of a solution of ammonic sulphocyanide, which gives a blood-red colour with ferric salts ; to the second (&) add first of all a few drops of nitric acid (to oxidize ferrous salts if present) and then a few drops of the ammonic sulphocyanide solution. Compare the tint depths of these tubes with one another, and of both with the pure water tube {c). If no red tint is observable in {a) tube, but is developed in (h) tube, iron is present in the form of ferrous salts. Dr. Franklin Parsons suggests the following method of rapidly estimating small quantities of iron : — " Take the residue of 70 c. c. used in the determination of the 1 AscUpiad, January 1SS4, p. 91. " Op. cit. 158 DETERMIXATIOX OF POISOXOCS METALS Dr. F. solids, ignite it gently (a strong beat renders the ferric Parson's gxide insoluble) dissolve it in a little warm nitric acid Quantitatu'e ' Method (wliicli oxidizes the iron to the ferric state) dilute to about 25 c. c. with water, and add a single drop of a solution of ferrocyanide of potassium. The blue colour resulting is gauged by comparison with that of a standard solution in the same way as ammonia is estimated colorimetrically. The standard solution is easily made by dissolving one decigramme of iron wire in dilute sulphuric acid, adding a few drops of nitric acid and boiling ; when cold it is to be diluted to 1 c. c. Each c. c. contains a milligramme of ii'on. This solution is kept in stock. A-N^ien required 1 c. c. of this solution is run into a 100 c. c. test mixer, diluted, a drop of ferrocyanide solution added, and the test mixer filled up to 100 c. c. Two cylinder glasses of equal diameter are then taken and placed on a sheet of white paper ; in one the dissolved water residue is placed and treated with ferrocyanide solution ; into the other is poured as much of the standard blue solution from the test mixer as will produce, when looked down through, an equal shade of colour. The amount is known by reading the graduations on the test mixer, each c. c. corre- sponding to "01 grain of iron per gallon: "05 gTain pev gallon may in this way be estimated in the residue of 70 c. c. of water. Prussian blue in solutions so dilute precipi- tates very slowly, so that the same standard solution will serve for several determinations. The solution of ferro- cyanide need not be of any definite strength, but had better be somewhat dilute : enough must of course be added to combine with all the iron present, but, on the other hand, care must be taken not to add a large excess, as it gives a yellow tinge to the solution which interferes with the correct estimation of the blue." The question, of course, arises as to the practical utility of making such minute determinations of iron in a sanitary analysis. DETERMINATION OF POISONOUS METxVLS 159 If we have occasion to ascertain whether or not a water defiled by mines or manufactories contains arsenic, -|- litre of such water, being rendered slightly alkaline by hydrate of soda or potash free from arsenic, should be evaporated to dryness. The residue having been digested in strong hydrochloric acid should be poured into the ap- paratus described on page 346 and depicted in Fig. 40, and examined by Marsh's test or by Davy's method, page 347. Co]3])eT. — The amount of this metal in a water is copper. usually determined by a colorimetric method, which is conducted in a manner precisely sunilar to those em- ployed in the other volumetric processes already described. The depth of brown or chocolate colour produced by a 4 per cent aqueous solution of ferrocyanide of potassium in a water containing copper, is imitated by that dis- played in an equal volume of distilled water to which different quantities of a standard solution of sulphate of cojDper (3-93 grammes in 1 litre of distilled water, of which 1 c. c. = 1 milligramme of copper) have been added. The amount of standard solution of sulphate of copper consumed of course furnishes the datum on which rests the simple calculation as to the amount of copper present in the sample of water. Mr. Wynter Blytli suggests the addition of a solution of nitrate of ammonia, which renders the reaction much more delicate. Zinc. — A case has been reported^ by the Medical zinc. Officer of Health of Llanelly of the impregnation of the public water supply to the village of Cwmfelin with zinc derived from the galvanized iron water pipes. The total solids being 18-9 grains per gallon, 6-41 grains of them consisted of zinc carbonate. It seems that pure zinc is easily dissolved l;)y water through which a current of oxy- gen and carbonic acid gas is ]3assed. This metal may be detected by evaporating to dryness a little of the water on ^^Lancct, March 1, 1884, p. 403. IGO DETEKMINATION OF POISONOUS METALS Should ■nater stored in leaden cisterns be used for drinking purposes? a piece of platinum foil ; when the volatile matter is burnt away the residue will be found to be yellow when hot, and white when cold. This residue, transferred to a piece of charcoal and treated with a solution of nitrate of cobalt, yields a green colour when heated in the outer flame of the blow-pipe. My experience teaches me the wisdom and expediency of recommending a strict avoidance for drinking purposes of all water that has been stored in leaden cisterns, or has otherwise rested for some time in contact with lead, until we 'possess data of a less contradictory and more definite description than at present as to the influence of various kinds of water under different circumstances on tills metal. CHAPTEE IX MICROSCOPIC EXAMINATION OF A WATER. A. Tlie Examination of a Water free from Deposit. — The approximative estimate of the number of micro-organisms and the diagnosis of tlie kind, whether bacteria, bacilli, micrococci, vibrios, spirillse, etc. may be accomplished by the aid of a microscope by making {a) a cover glass pre- paration and (b) a " drop culture." (a) Cover glass preparations. — The author finds it cover glass . prepara- useful to examine a water in the manner practised bytions. Xoch as described by Prof. Warden.^ With a glass rod sterilized by passing it several times through a flame of a Bun sen's burner, a drop of the water to be examined is placed on a clean cover glass, which is allowed to dry under a bell glass. " When the water has evaporated, the edge of the cover glass being held by a pair of pincers, and the side containing the residuum being upwards, the cover glass is rapidly drawn three times with a downward motion through the colourless flame of a Bunsen's burner or through a large spirit flame." The cover glass still held by the pincers is then flooded with methyl blue solution,^ 1 Op. cit. ^ Mode of Preparation. — Methyl blue, 2 grammes rubbed in a mortar with 10 c. c. of absolute alcohol to which 90 c. c. of distilled water is gradu- ally added. The mixture is filtered into a bottle provided with a perfor- ated cork carrying a pipette, by means of which a small quantity can be removed as required. A small fragment of camphor should be placed in the filtered solution. M cultures. 162 MICEOSCOPIC EXAMINATION OF A WATER which is allowed to act for about 3 minutes. The dye is then washed off by a gentle stream of water. The cover glass should be allowed to dry under a bell glass and finally mounted in Canada balsam when it is ready for the microscope. The easiest plan, perhaps, is to kill and precipitate the microbes by adding to the water a 1^ per cent solution of osmic acid, in the proportion of 1 c. c. of the latter to 30 or 40 c. c. of the former. Drop (b) " Drop cultures " have been recommended by Dr. E. Crookshank^ as suitable for the study of the life history of the micro-organisms in water. He gives the following directions for their management : — " Clean an excavated microscope slide and sterilize it by holding it cupped side downwards in the flame of the Bunsen's burner. A ring of vaseline is painted around the excavation. A clean cover glass is sterilized in the same manner. With a platinum needle bent at its extremity into a minute loop or ring (which has been sterilized by holding it in the flame) transfer a drop of sterile bouillon ^ to the cover glass and this drop is inoculated by touching it with another sterilized platinum needle charged with the water under examination." The slide is then inverted and placed over the cover glass, so that the drop will come exactly in the centre of the excavation, and is gently pressed down. On turning the slide over again the cover glass adheres, and an additional layer of vaseline is painted around the edge of the cover glass itself The slide must if necessary be placed in the incubator {vide fig. 8, page 82). In this manner the gradual growth of a micro-organism can be watched. B. Examination of Deposit. — The best and most simple ^ Introduction to Practical Bacteriology. 2 Made in the same manner as Koch's nutrient jelly {vide p. 76) with the omission of the gelatine and salt. The use of the hot water jacket is not needful during its filtration. MICROSCOPIC EXAMINATION OF A WATER 163 mode of examining the deposit from any sample of water is, first, to allow suspended matters to subside in the sample bottle ; and secondly, to decant the greater part of the water, and pour that at the bottom of the bottle containing the sediment into a conical glass. After subsidence a drop of the water containing the de- posit may be removed by means of a pipette to the cell of a microscope slide and be allowed to evaporate, or the drop may be immediately covered with a thin glass, the Fig. 15. Conical Glass and Pipette. excess being removed with blotting-paper, and examined. If a water possesses much turbidity this transfer to a conical glass is of course unnecessary. If the amount of sediment procured in this way is practically nil, the greater part of the water in the conical glass should be poured away, and that remaining in the angle of the cone should be transferred to a burette similar to, bvit of much larger diameter than, that depicted in Fig. 3. After subsidence the solid bodies may easily be removed in single drops of fluid on to microscope slides. In the microscopic exam- 164 MICROSCOPIC EXAMINATION OF A WATER ination of waters we require a 5-incli object glass, a Powell and Lealand or Zeiss' oil immersion -J^-tli-inch object glass, and an Abbe's condenser. A polariscope is a useful addition for the diagnosis of starch granules. The deposit of every water is treated by the French with the following reagents : a solution of iodine for the detection of starch ; a solution of carmine in glycerine and alcohol, which imparts to the nuclei of cells a red stain ; and methyl violet for bacteria. The tremulous molecular or Brownian movement of inorganic particles, in which there is no change of position, must not be confounded with the motions of micro-organisms. Liquor potassae and strong acetic acid, which either alter or remove fatty and albuminous granules, do not affect micro-organisms such as micrococci, etc. Inorganic The microscopic examination of the floating particles particles, gometimcs seen in water, will often afford valuable infor- mation concerning it where there is any doubt as to its quality. Mineral gritty matters,^ silt of clay, and sandy particles, may be the cause of persistent and unaccount- able diarrhcea, which medicines will only temporarily re- lieve. New comers to a place where such water is used often suffer. Those who drink such waters long become generally unaffected by these intestinal irritants. Chalky particles are dissipated by the addition of a little mineral acid, whilst the other inorganic matters apt to occur in drinking waters are unaffected thereby. The existence of animal life in a water affords good evidence in itself of the presence of a tangible amount of organic matter, alias filth, whether it be the micro- organism seen in the fairly pure waters supplied by the majority of the London companies, with an average of ^ The mountain dysentery prevalent in certain districts in India has been shown to be due to the employment of drinking water containing in suspension minute pai'ticles of mica. MICEOSCOPIC EXAMINATION OF A WATEE 165 about "08 milligramme of albuminoid ammonia per litre, or the various humble animal organisms of pond water, with its "38 milligramme of albuminoid ammonia per litre. These little creatures feed and flourish on what we call or- ganic matter, and in perfectly pure water they cannot live. Pasteur has shown that there are certain waters coming from deep-seated springs that are destitute of organic life, and are sterile ; but 9 9 out of every 100 waters contain a greater or less number of micro-organisms, and the great ma- jority of these 9 9 waters exhibit organisms of much larger dimensions than those which are known as micro-organisms. The kind of animal and vegetable life seen in water Description gives a certain clue to the description of water we are^^^'^^^g^. examining. Speaking generally, the infusoriee, the con- tawe life fervse, and vorticellse, are the inhabitants of the least pure ascertained of spring waters; then come the diatoms-^ and desmids ; entomostraca or water fleas ^ are seen in spring ponds, lochs, and impounded waters ; euplota and fungoid growths, etc., abound in pond and ditch waters, and in well water polluted with filth ; whilst bacteria and paramecia and spirilla are prominent in sewage-polluted water. There is no evidence to show that those low forms of life, commonly known as the fungi, are in themselves hurtful if taken into the system, although their appearance is an unfavourable symptom. It is highly probable, however, that the poisons of several of the zymotic diseases are ^ Some erroneously believe that the presence of diatoms is an indication of evil omen. The Bristol water, which is a fairly good one {vide p. 97), contains a quantity of diatoms of different kinds of which I have made drawings. Sometimes when very abundant they present the appear- ance of an exceedingly faint milky cloud settling doT\Ti to the bottom of the vessel which holds the water. ^ To the presence of vast numbers of dead entomostraca the fishy odour noticed by passengers in the steamboats on the Lake of Geneva has been attributed. These minute crustaceans secrete an oily substance under their carapaces, to which certain bad tastes of public water supplies have been ascribed ( Water Siqyply — Chemical and Sanitary, by Prof. Nichols). 166 MICKOSCOPIC EXAMINATION OF A WATER either identical with, or are products of, certain micro- organisms (which can be distinguished by their appearance or behaviour from one another) or find a congenial soil amongst such organisms, which act as carriers, to which they attach themselves, and amongst which they multiply. Dr. Frankland and his followers regard the presence of anything like a moving organism in a water as a danger- signal, for the reason that, if the poisons of such diseases as cholera and typhoid fever attach themselves to particles of organic matter, and can operate in inconceivably minute quantities, as is generally believed, there is a possibility of the disease ferment or germ of such maladies accom- panying elementary forms of life. Dr. Mills of Glasgow, following Dr. Frankland's example as to the metropolitan waters, frequently refers in his public reports to the presence of living organisms in the water of Loch Katrine as detracting from its purity. DESCRIPTION OF PLATES OF MICROSCOPIC OBJECTS FOUND m DRINKING AVATER.i 1. Actinophrys Sol. Order — Radiolaria. 22. Tabellaria floccosa. Family — Diato- 2. Algaj, with bacteria and diatoms. macece. 3. Bacillus. ) ^ ., ^ ^ . 23. Chsetophora Elegans. , „ , . [-Family — Bacteriacece. n^ -n i ■ ^i t ^ 4. Bacteria. ) 24. Euglenia. Class— Infusoria. 5. Amoeba. Class— Rhizopoda. 25. Anguillula. Order — Nematoda. 6. VorticellK. Class — Infusoria. 26. Rotifera. 7. Ova of Entozoa. 27. Cyclops Quadricornis. Order — Cope- 8. Euplotes Vannus. Class — Infusoria. poda. Sub-class — Entomostraca. 9. Paramecium. Class — Infusoria. 28. Cosmarium Margaritiferum. Family 10. Young Filaria, or thread worm.s. — Desmidiacece. 11. Confervte. 29. Diatoma Vulgare. 12. Muscular fibre. .SO. Diatom. 13. Spirillum. Family — Bacteriacece. 31. Fungi. 14. Hair (human). 32. Vegetable cellular tissue. 15. Linen fibre. 33. Scenedesmus. Family — Desmidiacece. 10. Cotton fibre. 34. Daphnia pulex. Order — Cladocera. 17. Mineral particles. Sub-class — Entomostraca. 18. Fragment of deal wood. 35. Micrococcus. Family — Bacteriacece. 19. Stomata of leaf. 36. Infusoria. 20. Epithelial scales. 37. Ova of Nais. Class — Annelida. 21. Closteriura moniliformis. Family — 38. Vegetable debris. Desmidiaf.ece. ■^ The objects are depicted as magnified by means of glasses of dif- ferent powers, but this is unimportant. My sole desire is to fix on MICROSCOPIC OBJECTS Y <\l \ lo folloyi (', TO IN DRmKING WATER MICROSCOPIC EXAMINATION OF A WATER 1G7 The public water supply of Llandudno was condemned some years ago by the late Mr. Wigner, the analyst, on the ground of its unfavourable appearance when examined by the microscope, for the results of his chemical study of it would not certainly warrant a censure. Free Ammonia . -068 ] ,^.,1. t^ .,, . . „„ > Milligramme per litre. Alb. Ammonia . -06 j ° '- Nitrogen as Nitrates and Nitrites . . "24 gr. per gallon. Another class of scientific men regard insects in water as scavengers that assist, like plants, in its purification, and place the greatest reliance on those great natural purifying processes of oxidation and dilution, the existence of which we are all too prone to forget. They urge that there is no reason for supposing that an animal poison will attach itself to an infusorian animalcule, but rather to organic matter in a state of putrefactive change, and that there exist good grounds for thinking that an animal poison when enormously diluted with water, becomes harmless, as An animal it does when very freely mingled with the other medium, ^°|,^j.^^^^j^° air. Personally I feel a greater sympathy with the latter diluted with than with the former class, although there can be no doubt becomes in-' but that when Dr. Frankland sees, by the aid of his micro- ^°'^"°'^^- scope, fragments of partially-digested muscular fibre which has been excreted by some carnivorous biped, in the water of the Thames, as furnished to a portion of the inhabitants of London, he is perfectly justified in making the fact public, and in urging the need for some amendment in the condition of the metropolitan water supply. Sufficient attention has not hitherto been directed to the kind of moving organisms found in drinking water, the attention the forms and apjjcarances of the various animal and vege- table bodies visible in waters, and of the extraneous substances with which they are most liable to be mingled, in order that a recognition of their difterences may prove of diagnostic value. 168 MICROSCOPIC EXAMINATION OF A WATER and the lessons taught by these differences. Mr. Ivison Macadam has expressed the opinion ^ that the presence of the Daphnia pulex and Cyclops quadricornis in a water is a proof of its purity, because these water-ileas are not found in bad waters, in which it appears they cannot live. He finds them in all our good impounded waters, such, for example, as that of Edinburgh, Eothesay, etc. A perfectly pure water contains no suspended matter, nor any animal or vegetable life ; but such is very rarely found. The ova of the entozoa, such as those of the round and the thread worms, the eggs and joints of the tape- worm, and small leeches, which may give rise to grave disorders, should not be forgotten in making microscopic examinations of drinking waters. The endemic hsematuria of Egypt and the South of Africa has been shown to be due to a htematozoon named bilharzia hsematobia, wliich is disseminated by water containing its ova. The germs of the parasitic disease named rishta, which is so prevalent in Bokhara, are considered by Jenkinson, Klopatoff, Fedchenko, and others to be diffused through the medium of water. The excellent illustrations in Dr. Macdonald's Gruicle to the Microscojnccd Examination of Drinhing Water, will be very helpful to students of this branch of water analysis. As scientific litera- ture is possessed of this valuable guide, I shall only add the following extract from the Hygienic Clas- sification of Waters contained in Parkes' Hygiene (5 th edit.) : — 1. Pure and IVhole- 2. UsaUe. 3. Suspicioits. 4. Impure. sonie. Same as Vegetable and animal Bacteria of any kind ; Mineral matter ; vege- No. 1. forms more or less fungi ; numerous vege- table forms with pale and colour- table and animal forms endochrome ; large less ; organic de- of low types ; epithelia animal forms ; no bris ; fibres of or other animal struc- organic debris. clothing or other tures ; e\-idences of sew- evidence of. house age ; ova of parasites, refuse. etc. ^ Paper entitled "Animal Life in Fresh Water Reservoirs." — Aberdeen Meeting of Social Science Congress, 1877. MICROSCOPIC EXAMINATION OF A WATEE 169 Those who are conversant with the use of the micro- scope will recognize vegetable tissue, starch, epithelial scales, human hair, the hair of cats and other animals, wool, bits of deal, fibres of silk and linen, cotton filaments, scales and legs of insects, and feathers, and will not be puzzled by such apparitions in the field of the microscope. Those who are not familiar with the appearances presented by these objects when magnified, should make themselves as soon as possible acquainted with them under low and high powers. Medical Officers of Health who are thus well grounded will find the microscopic contents of water an exceedingly interesting and instructive subject of study. Label. CHAPTEE X THE COLLECTION OF SAMPLES OF WATER FOR ANALYSIS. Every water analyst should have his samples of water collected in strong stoppered glass bottles, supplied by himself, which have been thoroughly cleansed with a strong acid before leaving his laboratory. Stoneware bottles should not be used, for that material is liable to introduce calcic sulphate, silicates, and common salt into the water. It is wise to have an ample supply of the water to be examined, so as to have a reserve in case of such accidents as the bursting of a retort, etc. A stoppered Winchester quart bottle holds a convenient amount. By avoiding waste, I find that about one litre of water is, as a general rule, sufficient for analysis, unless it is wished to make any special examination, as, for example, an estimate of the amount of magnesia in a water, when a stoppered " Winchester Quart " is employed. -Sanitary District. SAMPLE FOR ANALYSIS. Date of Collection- Source Spring, Pump or Draw Well- Depth of Well Nature of Soil and Subsoil- Distance of nearest Filth or Drain — Distance of nearest Cultivated Land- Reason for Analysis About twioe the above size vnll be found the most convenient. COLLECTION OF SAMPLES OF WATER FOR ANALYSIS 1 7 1 Before taking a sample, the bottle should be well rinsed three times with the water to be collected. The stopper should be firmly tied down by twine or tape, and a printed label, with gummed back, of the accompanying description, should be filled up and affixed to the bottle. It is a good plan to tie down over the mouth and stopper of the bottle a bit of guttapercha sheeting, to exclude the dust. These bottles are advantageously protected in their frequent transits about the country by enclosing them in a strong box, similar to that which is herewith sketched. Hay and straw, which are generally very dusty packing materials, are thus avoided. a a. Elastic pads that press on stoppers of bottles when box is closed. b b. Padlock and fastener. CHAPTEE XI TIME OCCUPIED IN PERFORMING AN ANALYSIS. Having estimated the amount of free ammonia, of albumi- noid ammonia, of oxygen absorbed, of solid residue, of chlorine, of nitrates and nitrites, the degree of hardness, and having noticed the appearance of the solid residue before, during, and after incineration, and having made a microscopic examination of any sediment that may be present, and having tested the water for poisonous metals, and examined it for magnesia and sulphates, we are in a position to answer the question as to whether the water submitted to us is good in every respect for a public water supply. It will be urged, with reason, that such an analysis as this, however desirable it may be, cannot be undertaken by the Medical Officer of Health, for so much time would be consumed in water examinations as to leave but little for other work. It is but rarely that I make a complete analysis of this kind, because it is seldom requisite. A head centre on all matters relating to public health should be able to conduct such an investigation, in order that when a question arises as to which of several waters would be the best in every respect for the public water supply of a town or village, he may be able to give an answer based on quantitative determinations of the several ingredients that affect the wholesomeness of a water. TIME OCCUPIED IN PERFORMING AN ANALYSIS 173 If the estimation of the free and albuminoid ammonia, the oxygen absorbed, and the chlorine, and the qualitative test for nitrates, does not show conclusively the character of a water, then it is advisable to add other tests, such as a quantitative determination of the nitrates and nitrites, the incineration of the solid residue, the calculation of the amount of saline matters, and the degree of hardness. If the question, " Is this water wholesome and good ?" Mode of be addressed to me, I immediately ask whether any illness extenTof or disease has been attributed to the employment of it. analysis. If there is a suspicion lest the water has interfered with the health of any person or persons, inquiries are made of the applicant as to whether there is any reason for suspecting the presence of organic matter or metallic poisons, or whether the water is found to be too hard for domestic purposes, or whether it is brackish or purgative. In fact, I ask what reason there is for complaining of the water. In this way the extent of the analysis is limited, and the applicant obtains the information required. In the majority of cases that present themselves, the question arises as to the amount of organic matter, whether within or beyond the permissible limit. Now, what amount of time is occupied in answering this last question with absolute certainty ? Thirty minutes. If it is needful, as is often the case, to estimate the exact amount of organic matter present in a water, forty minutes are consumed. If a more complete analysis is required, it is best to commence by starting the per- manganate of potash process for the absorption of oxygen, and whilst it is proceeding to determine the amount of chlorine, and the quantity of nitrates and nitrites in, and the hardness of, the water, whilst the distillation is going on. The evaporation of the 25 c. c. of water to procure the solid residue, and the weighing of the dish both before and after this operation, of course proceed simultaneously 174 TIME OCCUPIED IN PEKFORMING AN ANALYSIS with the distillation. If any special determination of the sulphates or other mineral ingredients is demanded, extra time is required. Unlike the Frankland and Armstrong process, which consumes two and oftener three days, the Wanklyn, Chapman, and Smith process is very rapid, as it can be completed within an hour by the most inexperienced. The Medical Officer of Health process described in this work, which is a modification of the latter, is generally rather more lengthy, its duration being dependent on the greater or less rapidity with which we arrive at conclusive evid- ence as to the character of a water. The Wanklyn, Chapman, and Smith method may be expedited by submitting for examination a 1 litre instead of a -|- litre of water, and multiplying the results by 4 instead of by 2. This rapid modification of the process is suitable only for the Medical Officer of Health who has had some experience in water analysis, to whom I would recommend it. Messrs. Townson and Mercer have made for me Nessler glasses of a size adapted for the examination of half the usual quantity of distillate, namely, 2 5 c. c. CHAPTEE XII ENTKY OF ANALYSIS IN NOTE AND EECORD BOOKS. The entry of an analysis may be conveniently made in the note-book thus : — Well at Woodhouse Farm. Date of Collection. — April 4/77. Source. — Well, witli pump, 25 ft. deep. ,, Analysis. — April 5/77. Soil. — Sand and gravel. Distance of nearest Filth. — 7 yards. Reason for Analysis. — Diarrlioea suspected from use. For Chlorine, 70 c. c. taken. Required of sol. nitrat. silver 20 c. c. .•.20 grains per gallon. For Solids 25 c. c. taken. — Dish and Residue . 26*251 Dish . . . 26-230 .•. 58-8 grains per gallon. •06 •03 •01 •021 4 •084 700 Free ammonia '02 Alb. ammonia „ -007 58-800 55 >5 ^^""^ •lO In litre free ammonia "054, and alb. ammonia ^20 milligram. Nitrogen as nitrates and nitrites l^^ grain per gallon. Total hardness 19 degrees. Oxygen absorbed in 4 hours at 80° F. '2 grain per gallon. Opinion. — Water condemned as unfit for drinking purposes. 176 EXTEY OF ANALYSIS IN NOTE AND EECORD BOOKS It is useful to keep a record book of all analyses for each sanitary district alphabetically arranged in parishes, the pages being ruled in a manner similar to the lines on the certificate of an analysis {vide page 213). Some make entries of the free ammonia and the albuminoid ammonia in terms of nitrogen, and, combining the nitrogen obtained from the nitrates and nitrites, add together the nitrogen from all sources. The amount of ammonia, be it free or directly derived from organic matter, may easily be represented as nitrogen by multi- plying by 14 and dividing the result by 17. In the foregoing analysis the two ammonias thus expressed would be registered as follows : — Milligi-amrae per litre. Free Ammonia '054 = Nitrogen as Free Ammonia "044 Alb. „ "20 = Nitrogen as Alb. „ "170 Total amount of Nitrogen -214 CHAPTEE XIII MISTAKES OF WATER ANALYSTS, AND HOW TO AVOID THEM To avoid errors in analytical work it is important to be very cleanly, orderly, and methodical. Many mistakes arise from a want of cleanliness and care in the collection of samples. Dirty bottles and corks should not be em- ployed. It is desirable never to rely on the memory, but to be business-like and exact in everything. All the details of an analysis should be written in a book kept for the purpose, at the time of its performance. A water should always be examined in a fresh state ;^"aiysis of for, by keeping, some of the free ammonia leaves the a fresh and water, and other changes take place. On April 1 3 stale concu- the water of an artesian well yielded free ammonia "36, and albuminoid ammonia '015 milligramme per litre. On April 16 another portion of the water, withdrawn from the same stoppered bottle as the first sample, was tested, and this second analysis gave of free ammonia •125, and of albuminoid ammonia "015 milligramme per litre. The water had lost "235 milligramme of free ammonia per litre in three days. This water was a very pure one. If, however, it had contained an excess of albuminoid ammonia as well as of free ammonia, con- fervoid growths would have formed in it (very rapidly in warm weather), and have fed on the free ammonia. 178 MISTAKES OF WATER ANALYSTS Want of clieniieo- eeolOEfical With a decrease of free ammonia there would have been a decided increase in the amount of albuminoid ammonia. "Waters should be examined, if possible, within thirty-six hours, in suijimer, after their removal from their source, and in the interim they should be kept in a cool dark place in stoppered bottles. A mistake on the part of an analyst may arise from a want of chemico- geological knowledge. Here are knowledge, examplcs. An analyst received a sample of water which did not prove on analysis to be perfectly clean, but, nevertheless, could not be condemned on the score of an excess of organic matter. Bearing then a some- what indifferent character for cleanliness, he tested it for chlorides, and found a large excess, which led him to condemn the water. He was not acquainted with the fact that this water came from the greensand, and that the purest waters from this formation contain an excess of chlorine. A water from a deep well in Essex was sent to an analyst who obtained the following data on which to form an opmion : — Grains per Gallon. MiLLIGRAMMME PER LlTRE= Part per Million. Degrees. Solids. 97-4 Chlorine. 37 Free Ammonia. •73 Alb. Ammonia. •04 Hardness. 6i He saw first that the solids were in excess. The lar»e amount of chlorine made him look with the strongest suspicion on the water. Then, on finding such an enormous quantity of free ammonia he con- cluded — overlooking the fact that the albuminoid ammonia was exceedingly small — that this well was polluted with urine. This water, however, is quite pure. He did not know — (1) That the water came AND HOW TO AVOID THEM 179 from beds of sand lying underneath the London clay, at a distance of about 250 feet from the surface; and (2) That these sandbeds furnish, in certain situations, water of great purity, which possesses an excess of chlorides and free ammonia. The following case occurred some time since in one of the south-western counties, which has utterly shaken the confidence of the local public in their opinion of their health officer. Two waters from neighbouring pumps, a pure water 1 . 1 . . . . -, , and an im- which were open to some suspicion, were examined by pure water him. The wat^r from one pump was pronounced to***^®^^'"^ be pure, and the water from the other was declared to the same be impure and quite unfit for drinking purposes. It^^'^^^ was ultimately discovered that both pumps derived their water from one and the same well. Such a lamentable mistake could hardly have occurred had not some utterly fallacious mode of examination been prac- tised. In justice, however, to this gentleman, it should be stated that a most extraordinary case has recently been published by Sir Charles Cameron, the well-known health officer and analyst of Dublin, where good and bad water would seem to have been present in a deep well at the same time, the pure lying in a layer at the bottom of the well, and the impure forming a stratum on the surface. Sample. Geains per Gallon. Qualitative. Part per MlLLION= Milligramme PER Litre. Solids. Chlorine. Nitrous Acid. Nitric Acid. Free Amm. Alb. Amm. No. 1 No. 2 29 47-4 2-1 1-7 Large amount None. Small amount Trace. •14 •00 •35 •08 No, 1 water was taken from the well by dipping it out from the surface, whilst No. 2 was withdrawn from a 180 MISTAKES OF WATER ANALYSTS tap, the pipe of which descended to within two inches of the bottom of the well. Sir Charles Cameron comes to the following conclusion : — " The water which enters the lower part of the well through its side and bottom is derived from springs, or at any rate it is water which had percolated throughout a considerable quantity of clay, and had thereby been deprived of any organic matter which it might originally have contained. On the other hand, the drainage of the surface of the sur- rounding soil must have in part made its way into the well through the sides, but near its mouth. As this drainage would undergo but little filtration, it would probably be contaminated with organic matter, as sur- face drainage so generally is." The writer has noticed a similar difference in quality of the water drawn at different depths from four other wells ; in one case, the solids per gallon amounting to 6 6 "2 3 grains in the bottom water, and to only 3 grains in the top water. I on one occasion analyzed samples of water taken from two dijSerent pumps connected with one and the same well (depth 18 feet), both samples proving exceedingly filthy. The pipe of the pump that drew water from the bottom of the well furnished a water which was more impure than that from the pump that obtained its supply at a higher elevation. The lesson taught by these facts is, that it behoves the collector of well waters for analysis to take precautions to secure samples representing the average composition of the whole contents of a well. Omission to The mistakcs of water analysts may arise from sins of metafs! omission as well as from those of commission. Two or three samples of a spring water were some time since submitted by a Eural Sanitary Authority to a distin- guished analyst with the object of discovering whether or not it was adapted for the public supply of a neighbouring town wliich was destitute of clean water. Foolscap AND HOW TO AVOID THEM 181 papers of formidable appearance, containing details quite incomprehensible to all but experts, were received after a delay of two or three months, which contained the assurance that the water was a very excellent one, and in all respects adapted for dietetic and all domestic purposes. No mention, however, was made as to the presence or absence of metals. I maintain that no one is justified in giving such an opinion as the above, unless he has made an examination for lead, copper, and iron in a water. Eesting on the opinion of the analyst, expensive water- works have been constructed, and the water has been " laid on " to the town. The water contains so much iron as to be very unpopular, the public preferring for drinking purposes the water of their polluted surface wells. The water from a well about 2 5 feet in depth was sent to a London analyst, who pronounced on the following data the opinion that the water was " polluted with sew- age," and " cannot be drunk without danger to health.'* Grains Per Gallon. Part per Million= Milligramme per Litre. Chlorine. 3-2 Nitrogen as Nitrates and Nitrites. •4 Volatile Matters. 5-6 Free Ammonia. •070 Albuminoid Ammonia. •058 The analyst adds, " The quantity of chlorine is so large as to be strongly suggestive of the source of pol- lution." Here, in this instance, two mistakes were committed. The above results would not warrant any one in affirming that the water was polluted with sewage, for it manifestly is not. They indicate that the water is a doubtful one, and should have led to further investigation. I analyzed the water of this same well on two distinct 182 MISTAKES OF WATER ANALYSTS occasions, separated by an interval of several montlis. My figures did not materially differ from the above, except that the proportion of free ammonia was slightly less, e.g.— Part per Million = Milligramme per Litre. Free Ammonia. Albuminoid Ammonia. First Analysis Second Analysis . •02 •02 •06 •05 A microscopic examination of the sediment showed the presence of an abundance of confervoid filaments on both occasions. The amount of chlorine is rather below the average of the surrounding district, all the purest waters of which furnish an abundance of chlorides derived from sandy strata. It is perfectly evident that the water con- tains vegetable impurities to some slight extent, and is accordingly not of the best quality. Here was a very serious error made by an analyst of note, who evidently relied on the indications afforded by the test for chlorine and the loss by incineration, to the exclusion of that obtained by microscopic examination, which is always analyses of dcsirablc in doubtful water. waiter vTeid- "^^^ apparent disagreement between the results obtained ing diflferentin Water analysis by different analysts was brought forward by a gentleman in the Chemical News of November 19, 1875. He publishes five analyses with opinions by five chemists of repute, of the water from the same well, and appends Ms conclusion — AND HOW TO A^,0ID THEM 183 Deqeees. Grains per Gallon. Part per Million = Milli- gramme per Litre. 3i +2 . g s si 3 02 1 o 3 o O 9 •5 s < A. B. C. D. E. 23-0 31-0 lS-6 22-3 7-0 9-0 5-8 4-4 16-0 22-0 12-8 17-9 27-5 22-8 27-0 24-1 26-6 2-500 3-500 0-587 1-852 6-5 0-5 4-3 0-78 0-78 1-25 0-91 ]-27 15-8 17-0 18-6 16-9 0-6 0-7 •01 •00 -10 -01 A. 's verdict is — That the water is of gootl quality. B.'s ,, It is surface water and is bad. C.'s ,, So much organic matter as to be unfit for drinking. D.'s ,, A perfectly pure water, and quite fit for all domestic purposes. E. 's , , The water is unusually pure. After such verdicts, surely it is necessary we should have some reforms in our practice of analytical chemistry. The prominence given in these analyses to the mineral constituents of this water, to the exclusion, in three out of the five, of the more valuable information as to the amount of filth, is noticeable. The only analyses on which it would be safe to offer an opinion, namely, those labelled C and E, show the water to be one of a variable, and for this reason of a doubtful, or suspicious character. When one meets with such a water, it is wise to make two or three analyses at intervals of two or three months, remembering the fact that many wells are liable to periodical pollution, dependent on the height of the sub- terranean and ground or subsoil water, and other causes. I have heard of as many as nine samples of an intermittent public water supply having been taken at different times of the day (24 hours) by an analyst who felt convinced 184 MISTAKES OF WATER ANALYSTS that some occasional pollution did occur. Eight samples proved on analysis to be pure. On making the ninth analysis he obtained proof of considerable organic con- tamination of the water. There is no evidence afforded that the samples of water, the analyses of which form the foregoing table, were all taken at the same time in per- fectly clean vessels, as was very properly pointed out by the public analyst of Cornwall CHAPTEE XIV USEFUL MEMOEANDA FOR MEDICAL OFFICERS OF HEALTH WHEN PERFORMING WATER ANALYSIS 1. Thoroughly wipe away all dust from the mouth of Memoranda, the sample bottle and stopper with a clean glass-cloth before commencing an analysis. 2. The hole at the upper extremity of the standard ammonia solution burette, for admitting air when the liquid is drawn off by the tap, should be closed by turning around the glass stopper, before leaving the laboratory for the day, otherwise evaporation will take place, and the remaining standard solution will become stronger than it should be when next employed. For the same reason it is undesirable to place more standard ammonia solution in the burette at a time than will be probably required. If, at the conclusion of one's work in the laboratory, a little solution only remains, it is as well to throw it away, and replace it by fresh from the stock bottle when next wanted. 3. On adding the caustic potash and permanganate of potash solution in the estimation of the albuminoid am- monia, it will be often noticed that on reapplying heat the steam that first passes off is not condensed, but escapes as such into the ISTessler glass. It is wise to hold up the Nessler glass so that the steam issuing from the condenser tube may impinge on its cold base, and be thus condensed. 186 MEMOEANDA FOR MEDICAL OFFICEES OF HEALTH 4. Sample bottles are exceedingly apt to fur, especially in warm weather, if waters are long kept in them, and difficulty is often experienced in cleansing them. "Waters containing much free ammonia are especially liable to the growth of confervse. It is desirable to wash out a sample bottle directly an analysis is completed. Bottles that have the slightest fur about them should be cleaned with strong impure hydrochloric acid and fragments of filter-paper. If this acid in a cold state fails to remove the fur, boiling acid must be employed. A most thorough washing with water is of course indispensable after the use of the acid. 5. Look narrowly for insect life in each sample of water submitted for examination. If a well water con- tains animal life of such a size as to be perceptible to the unaided eye, it is almost useless to analyze the water for organic matter, of which there is sure to be an excess. Animals will not exist in a fluid that does not possess organic matter on which they can feed. The presence of a distinct brown tinge in the water is often confirmatory in such a case of the presence of filth. Sometimes speci- mens of entomostraca may be seen along the edges of lakes and large reservoirs that supply towns with water. In such cases the volumes of water with which they are as- sociated are so enormous that an analysis does not show any excess of organic matter in consequence of their presence. 6. Some of the ammonia found in rain water that falls near dwellings is derived from the soot, for ammonia is a product of combustion. 7. In the estimation of the solid residue it is advisable to examine the under surface of the platinum dish, after the evaporation to dryness, before the dish is weighed, and to carefully remove any saline matter derived from the water of the water bath. It is always best to employ distilled water in the bath. WHEN PERFOEMING WATER ANALYSIS 187 8. The greater or less rapidity with which the solid residue increases in weight during weighing is an indica- tion as to the amount of the deliquescent salts common to water residues, such as the chlorides of calcium and mag- nesium, the nitrite of potash, etc., which are present. 9. After the analysis of a very impure water, it is wise to distil a little distilled water through the retort and condenser tube, in order to be sure that the apparatus is perfectly free from any traces of ammonia. 10. Loosen the connection between the retort and the adapter or condenser tube after an analysis, to prevent a fracture, which will sometimes occur on cooling if this precaution is not taken. 11. The health officer should be prepared to deal with frauds with which the public occasionally amuses itself. Analysts have received, for example, samples of pure water into which a little soup or beef tea or mutton broth has been introduced ; also samples of distilled water as obtained from druggists, and samples of rain water. 12. Nessler glasses are sometimes made of such thick glass, especially at their bases, as to give a distinct tinge of colour to colourless water. It is accordingly wise to select colourless and thin glasses, which should be all of exactly the same diameter. 13. Time is economized and accuracy is promoted if a separate graduated pipette be kept for each standard solution. A pipette should be filled by suction with the standard solution to which it is assigned, so as to moisten its interior before the solution is employed. CHAPTEE XV FOEMATION OF OPINIOX AXD PEEPAEATION OF EEPOET AS TO SAMPLE OF WATEE SUBMITTED TO ANALYSIS A FELLOW of the Chemical Society writes thus i^ — " The facts in connection with water analysis are not a subject of dispute, but the deductions to be derived from the facts ; and here we enter a region which is altogether outside the province of a chemist pure and simple, his usurpation to the contrary notwithstanding, and the question becomes one rather for the medical expert." Mr. Simon rightly insists upon a high standard of purity for drinking water. In his second annual report to the city of London, he observes that "we cannot expect to find the effect of impure water always sudden and violent. The results of the continued imbibition of pol- luted water are indeed often gradual, and may elude ordinary observation, yet be not the less real and appreci- able by close inquiry. In fact, it is only when striking and violent effects are produced that public attention is arrested ; the minor and more insidious, but not less certain evils, are borne with the indifference and apathy of custom." Although no sickness may be produced during the life of a man by the habitual use of an impure water, yet there can be no question but that impure water, like impure air, affects the physique of individuals, 1 " PotaLle "Water," by Charles Ekin. OPINION AS TO SAMPLE OF WATER 189 and tends to the degeneration of a race. Nearly every water contains some organic matter which, however, in exceedingly minute quantities is harmless, so far as our knowledge extends. Wlien its amount in a water exceeds a certain limit, it is unwise to drink the water. If it is present in still larger quantities, the drinking of such water is attended with risk, or even with danger. Some Delusions of may triumphantly observe that they have been endanger- ^^^p*^^"*^' ing their health during a great many years, and are not, to their own knowledge, at all the worse for the filth that they have taken with their water. They conclude, there- fore, that impure water, like tea against which the old woman of ninety was warned as a stealthy poison, must be exceedingly slow in its action. When will the public learn that what is apparently harmless to one is poison to another ; that some constitutions are sus- ceptible to a disease to which others are quite insus- ceptible ;^ that the susceptibility, when it exists, may only manifest itself at certain ages or periods in a life, or even times of the year ; that a person may at one time be susceptible to a disease, and at another time be insusceptible ? Wliat a mistake then is it for a man to argue that, because he has drunk filthy pond water all his life, and fancies that he has never suffered thereby, therefore such water is not injurious to health, when we physicians can prove that it will often produce fatal diarrhoea. Because pond water does not ahoays cause such disastrous results to all, such a man will argue that it can never do so to any. We know much, but we have yet much to learn as to the influence of impure water on the health of those in whom it does not produce disease. ^ Ample proof of the accuracy of this statement is obtainable. "Wit- ness, for example, the distressing symptoms produced in some people by the inhalation of the pollen of certain grasses, which form a complaint known by the name of hay fever, whilst the majority of persons are un- affected by the same. 190 OPINION AND PEEPARATION OF EEPOET AS TO The study of this sulDJect forms part of the greater one, as to the modus o'pcrandi of various climates on the health and character of men and animals. The question as to the suitability of peaty waters for the supply of individuals and communities often presents itself. The objections to such waters are twofold. (1) They are apt to produce diarrhoea in those unaccustomed to their use. Experiments made under the superintend- ence of Prof. Mallet showed that peaty waters, and waters containing an infusion of dead forest leaves, were distinctly injurious to rabbits. (2) Peaty waters are generally unpalatable and insufficiently aerated. Al- though they are soft and free from nitrogen as nitrates and nitrites, they are not properly oxygenated. They are accordingly unsuitable as public supplies where a non-peaty water can be procured. The French chemists consider that all potable waters should contain 33 per cent of dissolved oxygen. Should pond The miuds of health of&cers have often been exercised condemned as to the propriety of condemning pond water for domestic as unfit for ^gg^ j£ ^^ watcr bc storcd in clean vessels like the drinking purposes? drinking ponds in the chalk districts, and as the "mist ponds," situated in high uncultivated hills in the north of England, which are said never to become dry, being re- plenished by the fogs which they condense ; or if a pond is lined with cement, and so protected as to prevent the entrance of ditch water: — water will probably be furnished that is admissible. It will not, in fact, differ from the water of a lake or reservoir. Knowing, as we all do, that pond water as usually met with (1) is apt to create Its injurious diarrhoea in summer; (2) that those who drink it are generally troubled with intestinal worms ; (3) that these ponds are usually fed by ditches that drain fields which are often manured by town filth ; and (4) that there is a strong suspicion of the existence of a connection effects. SAMPLE OF WATER SUBMITTED TO ANALYSIS 191 between tlie emplojaiient of pond water and the pre- valence of malarial diseases :^ — we cannot, in the interests of the public health, approve of its adoption for drinking purposes. Families provided with this objectionable supply generally either strain the water through muslin, or boil the water, or pass it through a filter, or, if very turbid, a pinch of alum is added to clarify it. The father of a family drinks little else than beer, and the mother's beverage is tea. In summer and autumn, when there is a tendency to intestinal disorders, I have known entire families in rural districts, who have not taken the trouble thus to lessen the evil, thoroughly prostrate from severe diarrhoea ; and if the pond water has been fouled by the excreta of cattle, a form of continued fever, re- sembling closely enteric fever, has been induced. If the excreta are of human origin, the danger is, of course, the greater. This summer or autumn diarrhoea is doubtless at times produced by direct mechanical irritation, and at others by the absorption into the blood of septic matters. We have most of us in our memories instances of persons who have employed no other water than that from a pond in summer full of insect life, for all domestic purposes, and whose health has not, to the eye of a casual observer, suffered. I have known a man who died at the ripe age of between 80 and 90 years, and who boasted that he had drunk nothing but pond water for between 30 and 40 years. I have also known a man who reached the age of 90, and who consistently led for about 50 years a most drunken and dissolute life. Thames water collected below London Bridge, if allowed to stand in an open vessel for a few days in warm weather, ^ Case of an outbreak of ague at Tilbury Fort in 1872. Case of an outbreak of malarious disease recorded by Boudin amongst certain soldiers in one ship supplied with marsh water during their voyage from Algiers to Marseilles, whilst their comrades in another ship which was furnished with good water were all well. 192 OPIXIOX AND PEEPARATIOX OF EEPOET AS TO acquires a very offensive odour arising from the decom- Thames position of the animal and vegetable matter. This water water. ^.^^ formerly valued by sailors, and stored on board ship in wooden casks. When drunk, it was the custom to wipe away the solid matters that collected on the lips, after taking a draught, with the back of the hand. During the first week or fortnight of its storage in the hold, ship captains found that the water underwent a change described as a kind of fermentation, evohing a quantity of gas possessing a most offensive odour and depositing a copious brown sediment. The gases produced in the wooden casks were said to be slightly luminous in the dark and to be explosive. The coagulation of the albuminous constituents of the water by the tannic acid of the oaken casks probably occurred. The water gradually ceased to smell offensively, became bright and sparkling, and was said to keep fresh and sweet for an indefinite length of time, ha\Tiig lost the whole of its putrescent im- purities. Pond water has been known to undergo a similar change on board ships. In our war vessels, etc., iron tanks are used instead of casks for storing. It is said that in u-on tanks Thames water evolves no offensive gases, but becomes pure much quicker than when stored in wood, and deposits a more copious brown sediment which turns red on ex- posure to air. Iron possesses a wonderful power of causing the precipitation of the organic matter and some of the saline constituents of a water. Information j^ j^^s been Urged, as a serious objection to the as to source, _^ in-i surround- Wanklyu, Chapman, and bmith process, by those who mgs, etc., -bejjeye i^ the Frankland and Armstroncr process, that an of water, a o x ' sample of opuiion of the smallest value cannot be formed of a te^'aMiyzTd. ^^tcr examined by the former process without the fullest information as to soil, situation of source of water, dis- tance of possible centres of pollution depth of well, etc. Let any one read the printed instructions of Dr. Frank- SAMPLE OF WATER SUBMITTED TO AXALYSI3 193 land/ sent out by Mm to those who collect samples of water to be analyzed in liis laboratory, and it will be seen that be requires a similar amount of information for his own guidance. The reason of this is ob^ious. Every system of water analysis at present known has its weak points, some possessing more than others ; accordingly, the best methods hare to be fenced around with certain protections against error. It is a golden rule in water analysis never to give anGoMenmies opinion unless the analyst knows (1) the nature of the^^J^^^" source of a water — whether it comes from a spring, or well, or Tirev, or rain reservou^ etc. ; (2) the depth of the well, if it is withdrawn from one ; (3) the geology of the district from which it is derived, together with the char- acter of the soil and subsoil ; (4) the distance from the source of the water of the nearest filth or drain. Another golden rule is never to give an opinion as to the character of a water from an estimation of one ingredient only in the water. A very serious mistake has often been made by those who practise the ammonia process of water analysis, which has thrown great discredit on the chemistry of the subject. This mistake has been to deliver an opinion on the quality of a water which has been soldi/ formed from a determination of the amount of albuminoid ammonia contained in it. The practice of tabulating side by side with the total amount of albuminoid ammonia in a water, the fact of the appearance or otherwise of any pre- ^ "At the time the samples are forwarded for analysis, give the fol- lowing particulars : — (a) From what source — Wells, rivers, or streams ? if from wells, {h) describe the soil and subsoil, and also the water-bearing stratum into which the well is sunk ; (c) the diameter and depth of well ; (rf) the distance of the well from either cesspools or di-ains ; if from rivers and sti-eams, (c) the distance from the source to the point at which sample is collected ; (/) whether sewage or other animal polluting matter is known to gain access to river or stream above the point of collection ; if from springs, [g) describe the stratum from which the spring issues ; {h) state whether the sample is taken direct from spring or otherwise," etc. 194 OPINIOX AND PEEPAEATION OF REPORT AS TO ventable disease amongst those who had been in the habit of employing it, an example of which may be seen in Table VII. of Dr. de Chaumont's Lectures on State Medicine, is apt to be misleading. The arrangement of a table, in which the valuation or opinion of the analyst as to each water (as formed from the observance of certain rules for guidance) is placed in juxtaposition to the name of the disease, if any, apparently produced by it, would be ex- ceedingly interesting and of great practical value. Sanitary authorities will sometimes present to a Medical Officer of Health a sample of very dirty water, which is reported to come from a well, and will ask him whether, if the weU is cleaned out, the water will be good. This question can only be partially answered by an analysis. The hardness of the water can be rouglily ascertained, and the presence or absence of objectionable ingTcdients, such as purgative salts, metals, etc., can be determined. A muddy water has often been sent to me derived from a new well recently dug, with a wish that I should ascertain whether there is any excess of organic matter in it. Such an inquiry is equivalent to the following : — " I have placed filth (for mud contains organic matter) in the water. \ATien I cease to introduce filth. Turbid will the Water be free from any ?" Here are examples waters from gf turbid waters from new wells which have become pure recently dug . wells. after repeated removal of their contents by pumpmg : — SAMPLE OF WATER SUBMITTED TO ANALYSIS 195 Grains per Gallon. Part per Million = Milligramme PER Litre. Degrees. to o 111 c3 g'i 2 • c "S Well (25 ft.) in gravel g| . C Sept. 16 (fl.) . E| y Sept. 25 {b) . I.S "" ( Oct. 15 (c) . 51 21 7 2-1 2 None I ! )) •01 •56 •02 •02 ■175 •24 ■09 •04 13 The estimation of the nitrates and nitrites is valuable in such cases as the above, for it often gives information respecting the surroundings of the well. The Medical Officer of Health can frequently clear up any obscurity that may exist, by himself visiting the well and noting its situation, etc. A. Summary of Data on which to base an Opinion. 1. Odour. 2. Colour through tuhe. 3. Free Animo7iia — Its amount. ^ 4. Albuminoid Ammonia — Its amount I Smell of and manner of distilling j distillates? over, J 5. Oxygen ahsorled in 4 hours at 80° F. — Its amount. 6. Nitrogen as Nitrates and Nitrites. — Its amount. Nitrates or Nitrites ? 7. Solid Residue — Its amount. Behaviour with Hydrochloric Acid, Appearance Be- fore, During, and After incineration at a dull red heat. Amount of Volatile matters. Summary of data on which to form a judg- ment. 196 OPIXION AND PREPAEATIOX OF EEPOET AS TO 8. Chlorine — Its amount. 9. Hardness — Total, Temporary, Permanent. 10. Microscopic Ejcmnination of Sediment — Xature of objects observed, 11. Biological Examination. 12. Metcds. I oJpper \ ^^^^^^^^^ °^' non-existence. If J J ( present, tlie amount. 13. Mineral ^ ,^ • n i n n -r^ ,^ ( Magnesia, Salts oi j Present or ab- , . , . , , < Sulphates > sent. If present, obiectionaoie I -^^^ ^ . I -i .^ . f Phosphates. ) the amount. %j m excess. ^ ■' In the great majority of cases that present themselves to the Medical Officer of Health a complete analysis of this sort is not wanted. In nine cases out of ten the ques- tion to which an answer is required is, as to whether a water is or is not polluted with filth. To reply to this query it is simply necessary to ascertain the amount of free and of albuminoid ammonia. If the applicant wishes to know if the filth is of animal origin or decayed vege- table matter, we must estimate the quantity of chlorine and nitrogen in the form of nitrates and nitrites. If the interrogation is submitted to us as to whether or not a water devoid of filth is in other respects wholesome, a calculation of the amount of solid residue, of the hardness, etc., is needful. B. Valuation Tables and Disteict Standaeds. It would be a great convenience to the analyst if he were able to appraise each determination at its true value Mr.wigner'sin a definite manner, which can be represented in figures. tabie.*^°^ The late Mr. Wigner with this object in view, constructed SAMPLE OF WATER SUBMITTED TO ANALYSIS 197 a table ^ which gives the values in degrees of impurity of the several data on which an o]3inion is to be based. Appearance in two-foot tube. C. Blue . C. Pale yelloAv . C. Green C. Dark j'ellow . C. Dark oreen . Suspended matter to he added to the valuation of ajjpearance. For traces ,, heavy traces ,, turbidity S'inell when heated to 100° F. Vegetable matter .... 1 Strong peaty ..... 2 Offensive, of animal matter ... 4 Clilorine in Chlorides .... '50 gr, per gall. = Phosphoric acid as phosphates, traces = 2. h traces = 4. v h traces = Nitrogen in nitrates . . . . . "100 gr. per gaU. = Ammonia ...... '005 ,, = Alb. ammonia ...... "001 ,, = Oxygen absorbed in 15 min. at 80° F. . -002 gr. per gall. = „ „ 4 hours „ . . "010 ,, ; = Hardness before and after boiling added together each 5° = Total solid matter ..... 5 grs. per gall. = Heavy metals ....... s traces = Microscopical Results. Vegetable debris in small quantity .... „ ,, large „ . . . . Diatoms and bacteria in small „ . . . . large „ . . . . Hair and animal debris (according to quantity observed) = 12 6 . 12 10 to 20 Rules. A valuation at or below 15. ,, 60. = Exceptional purity. = First class Avater. = Second Analyst, July 1881. 198 OPINION AND PKEPAKATION OF REPORT AS TO The metropolitan companies furnish waters that show a value on this scale varying between 20 and 40. The foregoing table possesses three or four grave defects. 1. Some of the purest waters contain a large excess of free ammonia, and yet each '005 gr. per gall, is valued at 1. 2. Good artesian well waters often contain a large quantity of chlorine, and yet each "5 gr. per gall, is valued at 1. 3. Waters which cannot be condemned on account of the presence of peat absorb a large amount of oxygen, and yet each '01 is valued at 1. 4. Artesian waters organically pure, although not of the best quality, contain large amounts of solids, and yet every 5 grs. per gall, are valued at 1. Dr. Muter's j)x. Mutcr has suggcstcd ^ the following amendment of amended , i j • j_ i i valuation tlic abovc vaiuation table. table. Gr. Valuation per gall. number. Ammonia ..... each '0015 = 1 Alb. ammonia ... „ -0007 = 1 Oxygen consumed in 1 5 min. . „ -0040 = 1 „ „ 4 hrs. . „ -0100 = 1 He writes, " When any number exceeds 1 0, then all over 1 is to be doubled and added to the original number, and the total valuation is to be divided by 100 and noted as comparative degree of organic impurity.' Then S2cp2Josmg no other consideration intervenes to modify the analyst's opinion of the sample, I propose that the following limits should be observed : — First class water .... np to '25 degree. Second „ „ . . . . np to -40 degree. Undrinkable „ . . . . over -40 degree." ^ Analyst, June 1883. SAMPLE OF WATER SUBMITTED TO ANALYSIS 199 The divergence in views as to the relative values might be minimized by excluding from the late Mr. Wigner's valuation table any values for microscopical results, leaving them to individual opinion/ and by omitting and diminishing the values of free ammonia, chlorine, oxygen absorbed, and total solids under certain conditions. Some adjustment of the following kind might be Author's thought feasible. ^'^ig^es ions. Free, ammonia if in large excess is not to be valued, unless accompanied by an excess of albuminoid ammonia. Oxygen absorbed in 4 Jioicrs at 80° F., if in large excess is not to be valued beyond the value of the average of a water of medium purity, if an upland surface water, or water other than upland surface water, as the case may be {vide page 33), unless accompanied by an excess of nitrogen as nitrates and nitrites. Chlorine if in large excess is not to be valued unless accompanied by an excess of ammonia and albuminoid ammonia, nitrogen as nitrates and nitrites, and oxygen absorbed in 4 hours at 80° F. Total Solids if in large excess, as e.g. in artesian wells, are to be valued at 10 grains =1, unless there is an excess of albuminoid ammonia, when the late Mr. Wigner's value, 5 grains =1, may be employed. If some such qualified valuation were adopted, the total values in ^ My own views as to the relative values of the several microscopic objects with which one is familiar, would lead me to place them in the following order, commencing with those of least and concluding with those of most imjjoitance :— 1. Vegetable matters. 2. Diatoms and desmids {vide p. 165 footnote). 3. Animal life. 4. Animal debris such as epithelial scales, human hairs, partiall}' digested articles of food, fungi, etc. 5. Bacteria or bacilli so numei'ous as to be seen in each field of the microsco}ie. 200 OPINION AND PEEPAEATION OF EEPOET AS TO the rules as to the classij&cation of waters in accordance with their valuation would have to be altered. Any valua- tion table that could be framed would be necessarily a mere rough guide, in which every one might find some- thing to carp at. The history of a water, its surroundings, and the knowledge of the geological formation from which it is obtained, must be allowed to have a certain bearing on the judgment of the analyst. District The autlior is disposed to agree with the opinion standards, gxpresscd by Dr. Dupre and Mr. Hehner,-^ that the establishment of " district standards " is preferable to the adoption of a general standard. They consider that the fitness of any given sample of water for drinking purposes is best judged " by its conformity to, or divergence from, the general character of the waters of the district from which it comes (or the geological formation from which it springs), which from their surroundings may fairly be taken as unpolluted." The knowledge of the composition of the good well water of the locality from which the sample comes, which a Medical Officer of Health imperceptibly acquires after a time, often aids him in determining the nature of the water brought to him for analysis. C. Diagnosis and Formation of an Opinion. The difficulties in judging as to the sanitary condition of a water from an estimation of the number of colonies developed by the employment of either of the biological methods are in the present state of our knowledge in- superable. It is undoubtedly true that the biological is the most delicate of all known tests, and that the purer the water, cceteris paribus, the smaller the number of colonies present. It is equally true, howcA^er, that micro- 1 Analyst, April 1883. SAMPLE OF WATEE SUBMITTED TO ANALYSIS 201 organisms are to be found in nearly every water, and that length of storage, temperature, degree of aeration, etc. of a water, which have much to do with the number of colonies present, have, of course, no necessary connec- tion with pollution. Prof Bischof found : ^ (1) that New Eiver water kept for six days compared unfavourably, as to number of colonies, both with New Eiver water fresh from the mains, to which 1 per cent of sewage had been added, and with Thames water at London Bridge {vide page 213); (2) that the production of colonies is aided in a most marvellous way by increase of temperature from the freezing point where it is entirely stop|)ed, up to from 86° to 104° F. ; and (3) that a deficiency of oxygen in a water checked the development of microphytes. Until, there- fore, it becomes possible to eliminate the effects produced by such influences, we have still to rely very much on our chemical and microscopical methods in the formation of an opinion, availing ourselves of any corroborative evidence which biological methods may afford. 1. The amount of organic matter in the best spring P"i'est spring waters waters. Milligramme Milligramme per litre. per litre. Spring -water A. Free ammonia "OOS. Albuminoid ammonia "02. „ B. „ „ -000. „ „ -01. 2. A good water for drinking purposes should not^°°^^g contain more than Milligramme per litre. Free ammonia . . . . "01 or 'OS. Albuminoid ammonia . . • . '08 3. A water which possesses the following amounts of suspicions the two ammonias is classed amongst the suspicious waters. I have frequently noticed such waters as belonging to ^ Paper on " Dr. Kocli's Gelatine Peptone "Water Test," read, before the Socy. of Med. Ofiicers of Health on April 16, 1886. 202 OPINION AND PEEPARATION OF REPORT AS TO shallow wells surrounded by soil on which soapsuds, etc., are sometimes thrown. Milligramme per litre. Free ammonia . . . . "01 or -02. Albuminoid ammonia . . . •12. The suspicion of contamination is strengthened if the chlorides (in districts where these salts do not abound) and nitrates or nitrites (in non- chalky districts) are in excess. An excess or increase of the amount of saline residue is of unfavourable omen in the case of a doubt- ful water, for polluted waters generally contain a larger amount than pure waters coming from similar sources, although it cannot of course be said that a water which is higiily saline is for that sole reason to be suspected. 4. A water, with or even without an excess of free ammonia, which displays a larger amount of albuminoid deinnation. ammouia than '15 milligramme per litre, should always be condemned if there is an excess of nitrogen as nitrates and nitrites (in non-chalky districts), and an excess over the average of the district of chlorides. If the nitrates and nitrites should not be in excess, but the chlorides be considerably above the average of the district, the water should still be denounced as unfit for drinking. If, with the above-mentioned excess of organic matter, the nitrates, nitrites, and chlorides should be insignificant in quantity, we should not form so unfavourable an opinion of the water, but would suspect the organic matter to be of vegetable origin — a ^dew which would be strengthened or rebutted by other evidence, such as that derived from a microscopic examination of the deposit from the water, the colour of the water in a two-foot tube, etc. Waters de- serving con SAMPLE OF WATER SUBMITTED TO ANALYSIS 203 Grains per Gallon. MiLLIORAMME PER Litre. Water from spring pond situated in middle of a meadow. Water al- ways running from pond. Chlorine. N itrogen as Nitrates and Nitrites. Free Ammonia. Alb. Ammonia. 4-5 •1 •08 •18 Waters fouled by surface im- purities. The amount of chlorine does not exceed that found in the purest waters of the district. Entomostraca noticed in it. Sediment consists of confervse. Such a water cannot be condemned, but would simply be described as somewhat dirty. If the spring were enclosed by brick- work, so as to prevent the entrance of surface impurities, the water would be perfectly pure. Here is the analysis of a water from a draw-well situated close to a dusty highway road, in a district where the purest waters contain an excess of chlorine : — Grains per Gallon. Milligramme per Litre. B. Chlorine. 6-3 Nitrogen as Nitrates and Nitrites. •2 Free Ammonia. •01 Alb. Ammonia. •14 Such a water is simply fouled to some extent with surface impurities. If a pump were substituted for the bucket, etc., the water in all probability would be quite pure. 5. If a water exhibits an excess of free ammonia and^^j.^^.^ an excess of albuminoid ammonia, with an excess of polluted nitrates and nitrites, and with an amount of chlorine nVatte^r"!™^ above the average of neighbouring waters, that water is polluted with animal organic matter, e.g. — 204 OPIXIOX AND PKEPAEATION OF EEPORT AS TO Samples. Grains per Gallon. MiLLIGKAMME PER LiTRE =Part pee Million. Solids. Chlorine. Nitrogen as Nitrates and Nitrites. Free Ammonia. Alb. Ammonia. Waters from ^vells pol- luted by foul soil of ciLurchyard — A . . . B . . . Water of well polluted by manure of garden 94 11 ... Abundant Abundant 2-4 •12 •4 •12 •32 •52 •20 Waters con- 6. If a Water possesses a large excess of albuminoid with"ve'^e- ammonia, and but little or no excess of free ammonia, table or- and an insignificant amount of chlorides and nitrogen ° salts, there is strong presumptive evidence that the water is contaminated with vegdahle organic matter. Such a water may be offensive, even after filtration through the best of filters. E.g. Well Tvater fouled with rotten leaves ..... (A little rain water enters tlie well) Well waters rendered impure by the decayed roots of trees No excess of nitrogen as nitrates and nitrites in either of these three waters. Some peaty waters are an exception to this rule. Free ammonia, Milligramme per litre. •05 Alb. ammonia, •30 A. B. Free ammonia, •01 None. Alb. ?) •37 •25 E.g. Spring on Dartmoor, Devon (water very brown) Waaler from peaty well Milligramme per litre. Free ammonia, •OB Alb. „ -11 Free „ -06 Alb. „ •OS Peaty waters often yield equal, or nearly equal, amounts of free ammonia and albuminoid ammonia. When equal, or nearly equal, amounts of albuminoid ammonia pass off in each distillate, strong evidence is SAMPLE OF WATEK SUBMITTED TO ANALYSIS 205 afforded that the organic matter is of vegetable origin, although we must not conclude that when the albuminoid ammonia does not come over in that manner that the organic matter is not vegetable. Prof Wanklyn tells me that he found, on experimenting with the albumen of the egg and the gluten of wheat, this very important difference, as regards the manner in which the albuminoid ammonia often yields its ammonia. Milligramme per litre. Vegetable Organic Matter. Animal Organic Matter. •04 or -03 -06 or -07 •03 „ -03 -03 „ -025 •03 „ -03 ' -01 „ -005 Dr. Charles Smart thus discriminates^ between fresh and decomposing organic matter of animal or vegetable origin : — Okgaxic Matter. Eecent. Decomposing. Xitrogen as Alb. Amm. yielded slowly. Nitrogen as Alb. Amm. yielded more rapidly. Oxj'gen required by Drs. Letheby and Tidy's Permang. of Potash process. Animal. Vegetable. Animal. Vegetable. A small quantity. A large quantity. A small quantity. A large quantity. Colour interference. None. Yellow colour on addition of soda carb. to water, and a greenish colour with Nesslerized distillates {vide p. 41). Diagnosis of a Peaty Water. Colour. — Generally, but not always, a shade of nntty brown. Saline Matters. — Small in quantity. Chlorine. Do. Free Ammonia. — Very little ) or Equal, or nearly equal, in Alb. Ammonia. — Excess j amount. Hardness. — Very little. 1 Op. cit. Diagnosis of a peaty water. 206 OPINION AND PEEPAEATION OF REPORT AS TO Nitrogen as Nitrates and Nitrites. — Nil, or almost nil. Volatile Matters. — On burning solid residue, very little. Behaviour of Residue during Ignition. — It blackens in patches or waves, which colour is very persistent. Oxygen Absorbed. — Excess. N.B. — Water often contains some hydrogen sulphide. Analyst. ExAiiPLES OF Water. Grains per Gallon. Part per Million = Milligramme PER Litre. Solids. Volatile Matters. Chlorine. Kitrogen as Nitrates and Nitrites. Free Ainm. Alb. Amm. Dr. Shea Do. Author Dr. Shea 1. From peaty soil 2. From peat in sand 3. Peat spring ; hardness 2 or 2^ degi-ees i From peat ; soil contained car- bonate of iron, and consisted of a chalky marl. Water smelt strongly of hydrogen sulphide 10-85 6-05 5-00 29-35 •95 •85 1-40 1-57 1-85 1^4 1^1 1-2 •25 Kone. •02 -065 •04 •03 •08 -085 -06 •11 •06 Pollution by foul gases. The pollution of a "water by sewer gas or foul gaseous emanations from faecal matter may be diagnosed by the absence of an excess of chlorine and nitrogen as nitrates and nitrites, wliilst there is an excess of organic matter, and the microscope discloses an abundance of bacteria and micrococci. The knowledge of the source of the water will prevent the possibility of making a mistake between a water vitiated with vegetable organic matter and one poisoned by sewer gases. 7. If a water contains an enormous excess of free SAMPLE OF WATER SUBMITTED TO ANALYSIS 207 ammonia and an excess of albuminoid ammonia, the waters strongest evidence is afforded that a cesspool or urinal iSe°m,ement^ delivering its contents into the well. Urine very rapidly matters, decomposes, the micrococcus urete converting the urea into diagnosis, carbonate of ammonia, e.g. — Water from well polluted by urinal : — Milligramme per Litre. Free ammonia, above . . I'O Alb. „ „ . . -35 It is necessary to remember that rain water holds in solu- tion a large amount of free ammonia, derived from the air which it washes as it descends, and from the soot with which it is generally mingled ; and that, in consequence of the uncleanliness of the surfaces that collect it, which are often stained with the excreta of birds, it is apt to exhibit an excess of albuminoid ammonia. It is desirable not to confound the water of a well polluted with urine with water commingled with sooty rain water. The manner in which the free ammonia comes over, and the collateral evidence, almost render such an accident impossible. On distilling ^ litre of rain water collected on a slate roof in the country, which presented a slightly sooty appearance, I obtained the following result : — Free ammonia '35 •25 •12 •09 •09 •04 ■03 •97 I took off 7 distillates of 5 c. c. each, and did not come to the end of the free ammonia in this -l- litre of water. 208 OPIXIOX AXD PEEPAEATIOX OF EEPOET AS TO In the case of a water polluted with urine, the free am- monia passes over in a \Yholly different fashion, c/j. in \ litre. Free arumonia "38 •14 •065 •035 •620 In litre above I'O part per million = milligramme per litre. Rainwater There is One point of resemblance between the be- and well . c • n • water haviour of ram water and urine polluted water under polluted by (^jigtillation, which is, that in both cases the evolution of urme. ' ' ammonia cannot often be brought to an end. Prof. Mallet even insists that " the value of the Wanldyn, Chapman, and Smith process depends more upon watching the j/r ogress and rate of evolution of the ammonia than upon determining its total amount." " Tlie gradual evolution of albuminoid ammonia indicates the presence of organic matter, whether of vegetable or animal origin, in a fresh or comparatively fresh condition, whilst rapid evolution indicates that the organic matter is in a j)utrescent or decomposing state." The following differences between rain water and urine polluted water should also be borne in mind : — («) Particles of soot may generally be seen in rain by the naked eye, or by the aid of the microscope, which are absent in the latter. (b) The latter will probably contain an excess of nitrates unless actual sewage pollutes the water, whilst the former w^ill probably exhibit only a trivial amount, or none. (c) The latter will possess an excess of chlorine, whilst rain will not, unless it falls near the sea. {d) The latter will display a greater or less degree of hardness, whilst the former will be soft. SAMPLE OF WATER SUBMITTED TO ANALYSIS 209 Diagnosis of Pollution by Urine or by Slop and Sink Water. Free Ammonia. — Overwlieliiiing amount, from -50 to 2 milli- ^'^giiosis , . , of Pollution grammes per litre. ty siops^ Albuminoid Ammonia. — Excessive. Often about '3 or "4, or etc. even "6 milligramme per litre. Chlorine. — Generally in large excess. Nitrogen as Nitrates and Nitrites. — In either minute amount, or in large excess. Oxygen absorbed. — Excess. Analyst. Examples. Grains per Gallon. Milligramme PER Litre = Part per Million. Remarks. Solids. Volatile Matters. Chlor- ine. Alb. Amm. Free Amm. Dr. Shea Aiitlior Author Author "Water from well close to broken sink pipe Water from artesian well into which drain conveying urine from stable leaked Same after diver- sion of drain Water from a Shallow Well. Before "i Pollution by - f'.ontents of Drain. After J 50 75-6 103 2 Nitrogen as Nitrates and Nitrites. Xone Abundant 9 8-2 7-3 12-3 16 Very abund- ant •51 ■Oi •01 •69 •35 •31 •08 •07 •28 The com- paratively small pro- portion of free am- monia was due to the admixture of the urine with a vast quantity of water in this deep well. Persistent uncontroll- able diar- rhoea pro- duced. 210 OPINION AND PEEPAEATION OF EEPOKT AS TO Dr. Shea has kindly sent me particulars of an interest- ing case where a new cesspool was constructed about thirty yards from a well, to receive slop water. Fourteen days after its completion the water of the well was noticed to taste unpleasantly. On analysis it proved to contain neither free nor albuminoid ammonia in excess, for the intervening earth acted as a filter. No less than 17 "5 grains per gallon of chlorine were found in it, whilst neighbouring unpolluted wells possessed only 1*5 to 2'3 grains of chlorine per gallon. Diagnosis of Pollution by Contents of Cesspools and Sewers. Diagnosis A glaiicc at the following examples of waters polluted h ^ewagT ^y ^ cesspool and drain, and by soil containing a large excess of decomposing animal matters, reveals immediately the difference in the results obtained. Samples. Grains per Gallon. Milligramme PER JjITRE = Part per Million. Remarks. Solids. Chloi-iue Nitrogen as Nitrates and Nitrites. Free Amm. Alb. Amni. Water from shallow well near K. H. B. Water from shallow well at A. L. B. 101 50-4 12-5 6-9 excess none Above 1-0 Above 1-0 •24 •50 Polluted by leaky cesspool. Tj'phoid fever and diph- theria amongst the owners. Accidental overflow into well of cess- pool contents which, having been the ' reci- pient of the spe- cific poison of typhoid, spread the disease. SAMPLE OF "WATER SUBMITTED TO AXALYSIS 211 Free Ammonia. — In large excess. Albuminoid Ammonia. — In excess. Chlorine somewhat in excess, but not so marked as when slop water is the polluting agent. Nitrogen as Nitrates and Nitrites. — If sewage passes directly into a well — none. If sewage travels through some intermediate earth — generally an excess. Oxygen absorbed. — Large excess. 8. "Waters of shallow wells or springs in towns (the unsafe soil of which is, for the most part, more or less filthj) or^^*^^" near chiu'chvards, if found to contain an excess of solid residue, in the form of nitrates and nitrites, chlorides, sulphates, and phosphates, should be pronounced as unsafe ; although the amount of free and albuminoid ammonia may be insignificant, for we can never tell when the earth may cease to act as a filter by oxidizing the filth. In forming an opinion as to the condition of a water, we should, in weighing the e^ddence afforded, adhere strictly to the standard of pure drinking water of the district from which the sample is collected. "We should be extra-exacting as to purity in judging of a river water that has been polluted at some points of its course with the manure of fields and indescribable filth, for these river waters contain every now and then undigested por- tions of food excreted from the human intestinal canal, in addition to living organisms visible by the aid of the microscope, as well as the accompaniments of all life in water — namely, dissolved and suspended organic matter on which these same organisms feed. Septic poisons, or the poisons of the zymotic diseases, attach themselves to organic filth undergoing putrefactive decomposition, in which they find an appropriate nidus for development. It is questionable whether such rivers should ever be employed as public supphes, for, if the sewage of towns and villages on their banks be diverted and utilized on the land, the washings of manured fields cannot during 212 OPINION AND rKEPARATION OF REPORT AS TO periods of flood be altogether excluded. If such rivers are used for drinking purposes, an extra degree of purity should be demanded of the water companies that supply them. D. Preparation of Eepoet, Report of Ths opiniou of a water having been formed on a sound opinion. ij^gj^g^ j^g delivery is a very simple matter. In conse- quence of the severity of the criticisms that have been made as to the reliability of the several processes of water analysis, and as to the diagnosis with certainty between a small amount of vegetable and animal impurity in a water, certain analysts are very guarded in the choice of the language employed in the delivery of an opinion and express themselves thus : — " This appears to be a pure sample " and " slioivs no evidence of contamination from organic matter of animal origin " ; " the polluting material is of a highly nitrogenous character," etc. The modes of statement of the results of water analysis are so various that they produce, even amongst medical men, endless confusion, " Chlorine calculated as chloride of sodium," " Loss on ignition after deducting combined carbonic acid," are samples of the most recent eccentricities. Wliy all chlorides in drinking water should be entered as common salt, and why combined carbonic acid should be alone excluded from the loss on incineration, are peculiarities for which it is quite impossible to find any valid reason. Some analysts express themselves in parts per 100, a few in 10,000, others in 70,000 or in 100,000, or in parts per million, whilst others make an estimate in grains per gallon or milligrammes per litre. Oxidized compounds of nitrogen are entered by some as nitric acid, by others as nitrates, and by the majority as nitrogen in the forms of nitrates and nitrites. ^ In order to prevent such differences in the modes ^ Vide ' ' Rules for Interchange of Different Expressions of Results of Analysis," in Appendix. SAMPLE OF WATER SUBMITTED TO ANALYSTS 213 of expression of the results of an analysis which occasion so much annoyance amongst the public, one uniform plan of drawing up reports should be universally adopted. A form, of the accompanying description, is convenient for conveying a report to the sanitary authority or other applicant : — Sanitary Authority. 1S8 Analytical Report. NAME AND DBSCEIPTION of THE SAMPLE OF Water. Grains per Gallon. Parts per Million.l Hard- ness. Depnsit luader Mior +3 go 13 'S a 60 '0 a Analyst's Signature,. Late of Reports It may be remarked throughout this work thatjat times grains per gallon are referred to, sometimes septems and deci-gallons, whilst at others the metrical system is employed. The object in view is to render the Medical Officer of Health perfectly au fait in the interchange of one into the other, as it is necessary for him to be conversant with all the methods of calcula- tion in use. CHAPTEE XVI CONCLUDING REMAEKS ON SECTION I Eeadees of the foregoing pages will have perceived that concluding I do not recommend the complicated and tedious process of Frankland and Armstrong, and that I cannot advise the sole unaided adoption of the beautiful process of Wanklyn, Chapman, and Smith, nor exclusive reliance on the quantitative Forchammer permanganate of potash pro- cess, which is often misleading. Whilst agreeing with the inventors of the first process as to the necessity of regard- ing the amount of nitrogen as nitrates and nitrites in a water, I totally disagree with Mr. "Wanklyn in relying solely on the indications of the ISTessler test, to the exclu- sion of an estimation of these products of oxidation and other valuable data on which an opinion should be based. Fallacies, undoubtedly, attend Dr. Frankland's lengthy method, and Mr. Wanklyn's rapid method ; and errors are associated with the quantitative permanganate of potash processes, whatever those who are disciples of these several methods may think to the contrary. I am myself indebted to each process, more especially to Mr. Wanklyn's, in my studies of water analysis. The methods which I practise and recommend, and which I have in the foregoing pages attempted briefly to describe, are, it will be perceived, modified forms of the Wanklyn, Chapman, and Smith process and of the quantitative Forchammer or oxygen process. I am not conscious of ever having made a mis- 216 ■ CONCLUDING EEMAEKS take in water analysis. This success is not attributable to any exceptional skill, but to the excellence of the pro- cess, which I designate the " Medical Officer of Health Method," because it is particularly suited to his wants. Eecipes of Standard Solutions, etc. Nesshr Reagent. Dissolve, by heating and stirring, 35 grammes of iodide of potassium and 13 grammes of corrosive sub- limate in about 800 c. c. of distilled water. Add gradually a cold aqueous saturated solution of corrosive sublimate, until the red colour produced just begins to be permanent. Add 160 grammes of solid caustic potash to the mixture, which is then to be diluted with sufficient water to bring the whole to a litre. To render the test sensitive add a little more cold saturated solution of corrosive sublimate and allow it to settle. This reasjent is a rather troublesome one for the Medical Officer of Health to make, and that prepared by different persons varies somewhat. It is desirable that every one should obtain his ISTessler test from one and the same source, but this arrangement seems very difficult of attainment. Very good is to be procured direct from Messrs. Sutton of ISTorwich, or indirectly through Messrs. Townson and Mercer of Bishopsgate Street, London. Standard Soai^ Solution. 10 grammes of Castile soap are dissolved in a litre of weak alcohol (35 per cent). If 35 per cent alcohol is not readily procurable, it may easily be prepared by mixing 29 ounces and 15 minims of distilled water with 17 ounces and 30 minims of rectified spuit (generally 84 per cent), which is everywhere obtainable. CONCLUDING REMARKS 21 7 One c. c. precipitates one milligramme of carbonate of lime. This standard solution will not remain unchanged for an indefinite time. It loses strength. It is wise to make a small quantity of fresh solution every three or four months. One and the same water was recently examined by me for hardness with different standard soap solutions of various ages, and the following results were obtained : — (a) 19 1 degrees. (b) 17 „ (c) 16 „ (d) 18 „ (e) 17 „ It is useful sometimes to verify the strength of a soap standard solution by the help of a solution of pure fused cliloride of calcium, I'll gramme in a litre of water. One c. c. of the standard soap solution should precipitate 1 milligramme of carbonate of lime, which is the exact amount present in 1 c. c. of the cliloride of calcium verifying solution. Dilute Standard Solution of Ammonia. Keep two solutions — a strong and a dilute. To pre- pare the strong solution dissolve 3 "15 grammes of crystallized sal. ammoniac in 1 litre of distilled water. To prepare the dilute solution place 5 c. c. of the strong solution in a half-litre flask, and fill it up with distilled water. Mingle very thoroughly by pouring the mixture several times from the flask into the bottle, and from the bottle back again into the flask. The dilute solution contains ywu niilligramme in each cub. cent. These solutions should be perfectly limpid. They will not remain unaltered for an indefinite time. If any 21"8 CONCLUDING KEMARKS white filaments are visible in them, fresh solutions should be prepared. Permanganate of Potash and Caustic Potash Solution, Permanganate of potash crystallized, 8 grammes ; solid caustic potash in sticks, 200 grammes ; distilled water, 1 litre. Boil the above, so as to thoroughly dis- solve the chemicals in the water, and until about ^ of the solution has passed off" as steam to dissipate all ammonia. Eeplace the water lost in boiling, as steam, by adding sufficient distilled water to bring it back to the litre. This solution, notwithstanding the greatest precautions in its manufacture, invariably contains more or less ammonia. 50 c. c. of it should accordingly be distilled in -|- litre of twice distilled water, and the ammonia that is estimated must be abstracted from the results of each analysis of a water. It is desirable to write the correc- tion on the label of the bottle. Standard Solution of Nitrate of Silver. Dissolve 4"79 grammes of crystallized nitrate of silver in 1 litre of distilled water. One c. c. precipitates 1 millioframme of chlorine. SECTION II SANITAKY EXAMINATION OF A I Pi. CHAPTEE XVII THE PUKITY OF AIR The exammation of air for sanitary purposes by tlie Medical Officer of Healtli may be deemed by some as work that is needless, and which can be turned to no practical advantage. If preventive medicine and sanitation is ever to become an exact science, we must, as those who are laying its foundations, be able to state in precise language the boundary lines between wholesome air, air to which it is undesirable to be frequently exposed, and air which is so impure as to be quite unfit for breathing ; and, again, between the latter and that which is poisonous. It is as desirable to know the composition of the air we breathe as of the water we drink. Indeed, it is more important to attend to the cleanliness of a medium in which we are always bathed, and which is continually passing into and out of our bodies, than of that which is only occasionally, and by some rarely, introduced into an organ which contains a fluid possessing a certain anti- septic and destructive power over substances injurious to health. The insidious and indistinctly recognizable deleterious effects on the health of a continued exposure of the human frame is often more marked in the case of impure air than of impure water. The train of evils is so slowly but surely laid as to even escape the observa- tion often of an experienced medical man, who sees in a 222 THE PUEITY OF AIR case of blood deterioration by impure air one of imperfect or defective assimilation, anaemia, dyspepsia, hysteria, disordered biliary functions, or one of those indefinite and chronic ailments which lead the way to the development of some visceral disease. What a contrast is afforded by placing a representative of the rebreathed and otherwise vitiated air trades, who perhaps rarely sees the sun, by the side of one whose daily occupations are such as to give him the fullest benefit of the purest air and the freest exposure to solar light ! Bookbinders, or factory girls, or miners, from one of our towns and colliery districts, neither of whom are exposed to any distinctly poisonous influences, may, for example, be compared with sailors. The former are pallid, jaded, sallow, afraid of fresh air, with uncertain and capricious appetites, the normal functions of the body liable to continual disturb- ance, excitable, generally affected with a craving for stimulants — alcohol in the male, tea in the female — to temporarily alleviate their sensations of depression, whose lives are brief, their average duration being known by all insurance companies with mathematical precision ; whilst the latter — namely the jack tars — present a tout cnseivMe indicative of the highest degree of health and buoyancy of spirits, which is so well known as not to need descrip- tion. The sailor likes his occasional drinking bout when he goes on shore to enjoy freedom, after the confinement and tedium of a voyage, but is no " soaker." The moral condition of a class is intimately associated with its physical state, but a consideration of this connection would lead us too far away from the scope of these pages. The late Kegistrar- General, Dr. Farr, drew the atten- tion of the public some years ago to the recognized statistical law that the mean duration of life decreased as the proximity of one individual to another increased. THE PUPJTY OF AIR 223 Proximity. Mean Duration of Life 147 yards 51 years. 139 „ 45 97 „ 40 46 „ 35 28 „ 32 17 „ . 29 7 „ (Liverpool) 26 He stated that in 23 towns of this country tliere are 3 8 persons to an acre, and he suggested tliat the municipal bodies and local boards of our cities and towns should establish a bye-law, prohibiting the future building of houses which would render the density of population in excess of tliis limit. Medical Officers of Health should be in a position to state accurately, when required, if any given air is or is not deleterious to the health of the body continually or frequently exposed to its influence. Provided that they could positively lay down the limit beyond which the organic matter and carbonic acid of our rooms, in which the majority of us spend the greater portion of our lives, should not pass, then architects and inventors would soon find out- some simple, efficient, and economical mode of ventilating our houses and public buildings, which are nearly all afflicted with filthy air ; and our mortality from diseases which we know now to be indirectly preventible, or capable of considerable reduction, such as consumption, bronchitis, and other pulmonary affections, would be materially lessened. Pure air contains the followina; bodies : — 224 THE PURITY OF AIR Composition of Air. Composition Oxygen (Ozone, an active form of Oxygen, . ^ of pure Air. which varies in amount). . 209-6 (^§ Nitrogen . . . . . . 790- Carbonic Acid ..... "4 Moisture varying with temperature. Peroxide of Hydroqen 1 . i ,-r.^ 7 Tvr-^ • ^ • 7 r occasional components. JSitrous and JSitric Acids j Organic Matter ) • , . . . >■ very mmute traces. Ammonia j '' The purest air is to be found on mountains, moors, or far away from contaminating and polluting agencies, such as aggregations of men and annuals, manufactories, etc. There is an ample provision in nature for destroying the impurities of the air produced by man, especially the organic substances, some kinds of which become, when they decompose, injurious and often dangerous to him. Ozone, peroxide of hydrogen, and nitrous acid, are the three great purifying agents contained in the air, the first named being nearly always present in greater or less quantity, the two latter being the special productions of what the G-ermans call the " nieder-schlage," or the great cleansing operations of nature, such as the precipitation of the air - washer rain, storms, hail, dew, falls of snow, etc. Oxygen. Oxygcn. — The following results of analyses made by M. Eeynault and Dr. A. Smith show the deviation from a state of purity of air, as respects its life-supporting constituent, oxygen gas, in different situations and under different circumstances : — THE PUEITY OF AIR 225 Oxygen in Air — Summary of Averages. By Mons. Eeynault. Specimens. 100 from Paris ..... 9 ,, Lyons and around . 30 ,, Berlin 10 „ Madrid .... 23 ,, Geneva and Switzerland . 15 ,, Toulon and Mediterranean 5 ,, Atlantic Ocean 1 ,, Ecuador .... 2 „ Pichincha, higher than Mont Blanc .... Mean of all foregoing „ the Paris specimens Yolume per cent, from 20-913 to 20-999 „ 20-918 to 20-966 „ 20-908 to 20-998 „ 20-916 to 20-982 „ 20-909 to 20-993 „ 20-912 to 20-982 „ 20-918 to 20-965 „ 20-960 „ 20-949 to 20-981 20-949 to 20-988 20-96 20 By Dr. Angus Smith. N.E., seashore and open heath (Scotland) Atlantic, lat. 43° 5', long. W. 17° 12' Top of hills (Scotland) .... In a suburb of Manchester in wet weather . Do. do. do. In the outer circle of Manchester, not raining Low parts of Perth ..... Swampy places, favourable weather In fog and frost in Manchester . In a sitting-room which felt close, but not excessively so . Best ventilated wards in three London hospitals- Day Midnight ...... Morning ...... In a small room with petroleum lamp Ditto, after six hours .... Pit of theatre, 11.30 p.m Gallery, 10.30 p.m About backs of houses and closets In large cavities in metalliferous mines (average of In a schoolroom ..... Court of Queen's Bench, February 2, 1866 . Q Volume per cent. . 20-999 . 20-99 . 20-98 . 20-98 . 20-96 . 20-947 . 20-935 922 to 20-95 . 20-91 . 20-89 20-92 20-886 20-884 20-84 20-83 20-74 20-86 20-70 20-77 20-64 20-65 many) 226 THE PURITY OF AIR Volume per cent. . 20-49 ny) 20-424 20-14 18-5 18-27 17-2 . 20-92 20 86 . 20 77 20 85 20 78 . 20 75 . 20 79 . 20 81 Court of Queen's Bench, at Lantern Under shafts in metalliferous mines (average of many) In sumps or depressions in do. . "When candles go out .... The worst specimen yet examined in a mine . Very difficult to remain in for many minutes By Various Scientific Chemists. Heidelberg (mean of 28 analyses) Bunsen Paris. Dumas and Boussingault ^ Faulhorn. Do. Brussels. M. Stas Geneva. M. Marignac Bern. M. Brunner , Groningen. Verver . Copenhagen Herr Von Jolly concludes from liis experiments in the neiglibourliood of Munich, that the variations in the amount of oxygen contained in pure air are influenced by the direc- tion of the wind. He found the highest proportion of oxygen with a steady polar current and the lowest with currents from the equatorial regions where processes of oxidation preponderate. The remarks that accompany Dr. A. Smith's analyses, dealing as they do with a point that I have long wished to press on the attention of the sanitary public, are worthy of weighty consideration. Some people will probably inquire why we should give so much attention to such minute quantities^ — between 20-980 and 20-999 — thinking these small differences can in no way influence us. A little more or less oxygen might not affect us ; but supposing its place occupied by hurtful matter, we must not look on the amount as too smaU. Subtracting 0-980 from 0-999, we have a differ- ence of 190 in a million. In a gallon of water there are 70,000 grains ; let us put into it an impurity at the rate ^ Annalcs de Chimie 1841. THE PUKITY OF AIR 227 of 190 in 1,000,000 ; it amounts to 13"3 grains in a gallon, or 0'19 gramme in a litre. This amount would be considered enormous if it consisted of putrefying matter, or any organic matter usually found in waters. But we drink only a comparatively small quantity of water, and the whole 13 grains would not be swallowed in a day, whereas we take into our lungs from 1000 to 2000 gallons of air daily. If, by inhalation, we took up at the rate of 13 grains of unwholesome matter per day — half a grain per hour — we need not be surprised if it hurt us. Such an amount is an enormous dose of some poisons, and yet this is not above one two-thousandth part of a grain at every inhalation. It is marvellous what small amounts may affect us, even when, by repeated action, they do not cumulate as certain poisons do. We commenced by assuming very small shades of difference — namely, 1 9 in a million ; but if we examine the table we shall find much greater quantities. Take, for example, the pit of a theatre; we have, by subtracting 20*74 from 20 '9 9 9, a difference o'f 2590 in a million, or 14 times more. And so on we may descend to the lowest in the series, where we have 17 "2, which, taken from 20-999, leaves 3-799, or 37,990 in a million, or 200 times more than the first example. Carbonic Acid. — The amount- of carbonic acid in the carbonic air varies according to Boussingault^ Farsky, Henneberg, ^"'^' Pettenkofer, and Cleasson, in different parts of the world from -279 to '060 per cent. It has been experimentally shown that its quantity in the air : (1) is greater in the night than by day on land, due doubtless to the large amount evolved by vegetation during the hours of dark- ness; (2) is slightly increased towards noon and after rain ; (3) is greater in the air collected above the ocean by day (•05 per cent) than by night (-03 per cent). M, Mene^ ^ Comptes Rendus, Ivii. 155. 228 THE PUEITY OF AIE has found that the proportion of carlDonic acid in the air varies at different seasons, being constant in December and January, increasing in February, ]\Iarch, April, and May, and decreasing from June to August, increasing again from September to November, and attaining its maximum for the whole year in October. Saussure dis- covered that the carbonic acid of mountain air is in larger amount than in that of plains. The remarkable uniformity and constancy in the amount of carbonic acid contained in the air of our parks and fields in the neighbourhood of cities, notwithstanding the universal pollution of the air rhat is unceasingly proceeding, shows the existence of tecuperative forces in nature of the greatest magnitude. The observations made by M. Marie-Davy at the Montsouris ObserA^atory, which is situated at the junction of Paris with the country, seem to furnish, as a rule, much lower results than were obtained by Mr. Dixon in, and in the \acinity of, Glasgow. "Whilst the percentage ranges between '02 and '03 at the former station,^ it somewhat ■^ In order to render the differences in the amount of carbonic acid in the air more apparent, he registers it as litres in 100 cubic metres of air, which can be easily changed into percentages by placiug tlie figure before the iirst figure and removing the decimal point to a position in front of that 0, e.g. Monthly mean 29 '7 = "0297 per cent. rarh of Montsouris. Average of nine years observations involving more than 3000 analyses. Annucd. . 28-6 . 29-0 . 29-6 . 29-3 1877 . . 28-4 1882 . 1878 . . 34-5 1S83 . 1879 . . 32-9 1884 . 1880 . . 27-0 1885 . 1881 . . 27-7 Annual mean, 29 '6. Monthly. January . 30-4 July . February . 29-7 August March . . 29-6 September April . . 29-8 October May . . 29-9 November Juna . 30-3 December Monthly mean, 29 '7. THE PUEITY OF AIR 229 exceeds "03 at the latter stations. Nor is this divergence wholly due to differences in the quality of the air around Paris and around Glasgow. There is a very strong pro- bability, ahnost amounting to certainty, that it is partly owing to the greater speed at which the air is passed through the chemical reagent at Montsouris than at Glasgow. JVI. Marie-Davy transmitted air through his aspirator at the rate of about 10 cubic feet per hour, whilst Mr. Dixon sent 1 cubic foot of air through his absorbing solution in the same space of time. Chemical action consumes a certain definite time, and if we hurry air through a chemical solution, intended to withdraw from it any body wliich it contains, too rapidly, the air is not thorouglily deprived of the same. Eecent experimenters have found a larger amount of carbonic acid on the summits of high mountains than on their sides at a lower elevation. ( Vide following Table.) The observations made by M. G. Tissandier in his late ascent in the balloon named the " Zenith," are confirmatory of their results, for he found at an altitude of from 800 to 890 metres that the amount of carbonic acid in the air was '024 per cent, and at 1000 metres "03 per cent.^ Although many explanations of what must, I suppose, be admitted as a fact have been attempted, not one has as yet been offered which is altogether satisfactory. As in the case of the amount of oxygen, so in that of the quantity of carbonic acid, in pure or moderately pure air, there is a remarkable absence of discrepancy in the analyses, made by different chemists by dissimilar processes, of air taken under similar conditions in various parts of the world. ^ Gomptcs Rcnclus, April 12, 1875. 230 THE PURITY OF AIR Mean of 18 analyses on Lake Geneva, by Sanssure^ Air of Madrid outside tile walls. Mean of 12 analyses by Luna^ ...... Air of Madrid inside tbe walls. Mean of 12 analyses by Luna ...... Air of Municb, by Pettenkofer ^ . Air of summit of Mont Blanc, by Frankland * Air over Irish Sea, July and August (Dr. Thorpe) Air in Brazil (April and May) Hills above 3000 feet ." . (A. Smith) „ between 2000 and 3000 feet „ „ „ 1000 and 2000 feet „ „ below 1000 feet . . „ . At the bottom of the same hills . On hills in Scotland from 1000 to 4406 feet In the streets of London (summer) In the London parks and open places . On the Thames at London .... In the streets of Glasgow (E. M. Dixon). Mean of results for May and June 1877 Air of S.W. suburbs of Leicester (Weaver) Per cent. •0439 •045 •051 •050 •060 •030 •032 •0336 •0332 •0334 •0337 ■0341 •0332 •0380 •0301 •0343 •0304 •0460 1 Ann. de Chem. ct de Phys., vol. xliv. 1830. 2 Estudios quimicos sobre et aire atmosferico de Madrid, 1860. ^ HandworterMich der Chemie — Yentilation. " Ou the Air of Mont Blanc ; " Jounuil of Chemical Society, 1861. ^ Journal of Chemical Society, 1867. PAET I DIFFERENT KINDS OF IMPUPJTIES The air is deteriorated in quality and defiled by — Different 1. Eespiration ^ and Transpiration. whereby air 2. Combustion. isdeterio- rated in 3. Putrefactive processes, sewage emanations, and excre- quality and mental filth. 4. Gases, vapours, and suspended metallic, mineral, and vegetable matters given off by trades and manu- factories. 5. Poisons of unknown nature evolved by damp and filthy soil. ^ The changes that are found to have taken place in pure air that has been respired are roughly the following : — (1) 100 parts of air contain only 13, instead of about 21, parts of oxy- gen, the missing 8 parts having been withdrawn by the blood corpuscles in the lungs. (2) The "03 or -04 part per cent of carbonic acid is increased to between 4 and 5 per cent. • (3) An increase of watery vapour is noted, which is loaded with organic matter. CHAPTEE XVIII ORGANIC MATTEE Organic matter. Animal. All air contains some organic matter, which may be of different kinds. It has been divided into («) the whole- some, (h) the neutral, (c) the putrid, and (d) the organized = dangerous form. I apprehend that, in designating any particular kind of organic matter as wholesome, it is not intended to con- vey the idea that the presence in air of this variety is conducive to health, but rather that it does not influence health in one way or the other. It would be as well perhaps to combine the " wholesome " and " neutral " into one class, thus making only three varieties. It may be said at the outset that it is quite impossible by chemical means to distinguish one variety of organic matter from another. Organic matter may be of an animal or of a vegetable nature, but the sum and substance of all the most recent observations on air is, that the bodies, the presence of which creates the difference between good or healthful air and bad or deleterious air, are mainly of a nitrogenous organic character. Animal organic matter is thrown off from the lungs in respiration, and from the skin by transpiration, in a state of invisible vapour and of epithelial dust. In 1870 Dr. Eansome read a paper -^ " On the Organic Matter of ^ Proc, of Manchester Philosph. Socy., February 22, 1870. ORGANIC MATTER n o o Human Breath in Health and Disease," in which he stated that the vapour of human breath in adults in a state of health, if condensed in a large glass flask, surrounded by ice and salt, and examined by the Wanklyn, Chapman, and Smith process, yielded about 3 grains of organic matter in 10 ounces of the condensed fluid, a quantity sufficient to make the fluid highly decomposable, and ready to foster the growth of those lowly organisms that we believe to be the intimate companions of the morbific ferments. This animal organic matter decomposes and gives off various volatile nitrogenous compounds, which, although they may not themselves produce disease, undoubtedly lessen the power of the body to resist its attack. More- over, putrefying animal matter is a favourite pasture for the development and dissemination of the animal poisons. It would seem to exert a distinctly poisonous action on one at least of the lower animals, if we are to accept the experience of Dr. Hammond, who placed a mouse under a bell glass, taking care to supply it with plenty of oxygen, and removing all carbonic acid and watery vapour, per- mitting the organic matter to remain. The mouse died in 45 minutes. Excremental filth, in a condition of impalpable powder, is often present in the air, and is the most disgusting of all the impurities to which man is exposed. As many diseases pro^mgate themselves by eliminating their poisons through the medium of the exhalations and excretions of the body, air thus polluted is often the bearer of the or- ganic poisons by which maladies are disseminated. Medical men and district visitors, who enter the dwell- ings of the poor in crowded courts and alleys, are perfectly familiar with the foetid emanations that abound in such unwholesome styes. The peculiar sickening odour of or- ganic matter is especially noticed in crowds of the great 234 ORGANIC MATTER unwashed, and creates often, in those unaccustomed to such smells, a feeling of faintness, languor, and debility. VegetahU organic matter, if excessive in the air, is associated with a poison productive of ague and other malarial affections.^ Whether or not there exists any causative relation between the micro-organism named the bacillus malarias and these diseases, is still a moot point. The quantity of the nitrogenous material (ammonia and albuminoid ammonia) found in air varies, of course, and is a measure of its impurity, be it furnished by animal and vegetable decomposition, or by soot and im- perfectly consumed organic impurities proceeding from manufactories. Dr. Angus Smith discovered "066 milli- gramme of ammonia, and '190 milligramme of albuminoid ammonia, in each cubic metre of air in a bedroom at 9 P.M., and "095 milligramme of the former, and '334 milli- gramme of the latter, per cubic metre, in the same room on the following morning at 7 A.M." Mr. Moss ^ whilst finding as a mean of eight observations "093 milligramme of ammonia and '088, or roughly "09 milligramme of albuminoid ammonia, in each cubic metre of the air of Portsmouth, estimated the proportions present at the same time in the Portsmouth Hospital, in the officers' quarters, etc. ( Vide Table.) Ammonia generally occurs in the air as a salt, such as the carbonate, chloride, nitrate or nitrite, derived from decomposing animal matters, such as manure, sewage, effete matters from the lungs and skins of men and other animals, from soot and manufacturing products. Some express the amount of the ammonia, and the * The answer of Dr. C. F. Oldham to the query which forms the title of his work, What is Malaria ? namely that " Malaria is chill," and that ague and other malarial diseases are not produced by a specific poison, is not accepted by the medical profession. ^ " Air and Eain." ^ Lancet, 'Novemhev 2, 1872. ORGANIC MATTER 235 ammonia derived from albuminoid ammonia, which they detect in air, in terms of nitrogen, by multiplying by 14, and dividing the result by 17. The nitrogen from both kinds of ammonia being added together, is recorded as the total nitrogenous matter in the sample. The old methods of estimating ammonia, in vogue before the discovery of the Nessler test, yielded most con- tradictory evidence. The invention of this re-agent, which can be worked with marvellous delicacy and precision, has inaugurated a new era in air and water analysis. The following observations have all been made by its assistance in different ways, which will be described, in connection with the names of the analysts, in the chapter on " The Chemical Examination of Air," page 310 ; — 236 ORGANIC MATTER Air-Washings. By Dr. Angus Smith, Mr. W. A. Moss, and Dr. C. B. Fox. Milligramme in One Sample of Air. Time and Weather. Cubic Metre of Air. Ammonia. Albuminoid Ammonia. In Manchester, Laboratory Office, 10 a.m. .... •106 •266 ,, ,, 4 P.M. •133 •293 Gas-room, 10 a.m, •130 •213 ,, ,, 4 p.m. •190 •427 Yard behind laboratory Fine," Oct. 28, 1869 . Freezing, snow on the •095 •095 ground, Dec. 28 . •106 •356 )j J » )? Damp, Jan. 13, 1870 •059 •213 Fine, Jan 25, 1870 . •190 •316 5 ) J5 : J Foggy, Jan. 26, 1870 •142 •221 Street, open Raining, and strong Average Bedroom — Average of . wind, Dec, •071 •261 ■122 ■266 •101 •238 Midden — Average of •336 •415 In London. Average •061 •150 Air of the Underground Nov. 11 and 12 (morn- Railway (Metropoli- ing) •109 •457 tan), 1869 Chelsea (three places) Nov. 4, windy . •045 ■110 Brompton ,, ,, Nov. 4, windy, and a shower of rain •047 ■128 In Glasgow, Average . •078 •304 Shore, Innellan, Firth of March s", N.N.K Clyde wind •052 •137 ORGANIC MATTER 237 Air-Washings — Continued. Milligramme in O^e Sample of Air. Remarks. Cubic Metre of Air. Ammonia. Albuminoid Ammonia. In Portsmouth. Mean of eight observa- Air obtained at eleva- tions at different times tion of 20 feet •093 •088 in open air Rooms (Officers' Quar- •436 •462 ters) No. 5 Ward of Hospital •428 1-307 >j J) • •855 1-018 No. 7. „ •520 -753 Variola Ward Rubeola Ward (cliil- - dren . . . Both were freely ven- \ tilated,andinboth < disinfectants were I •309 •226 -416 -197 freely used . ) Respired air in health- •218 •545 )J 5) . •122 •169 3) ) ) •112 •099 )J )) •144 •177 In Essex. Air on banks of Thames Wind flowing from after passing over river to shore •03 •10 marshes Air of sitting-room Occupied by one per- son for several hours. Good fire. Venti- lation by draughts underneath door and windows, which open to ground •066 •265 Air of bedroom, after No ventilation of any being occupied by three kind •264 1-367 persons for nine hours, at 7 A.M. Pure air of meadow . •066 ■044 By Mr. W. A. Moss. By C. B. Fox, M.D. 1 The amount of impurity found in the air of this ward gives, I should imagine, a fair example of the state of a fully occupied ward under ordinary conditions. — AV. A. M. 2 These analyses show a considerable variation in purity, even in the same individual. It appears probable that a far larger amount of organic matter passes into the air from the skin than from the lungs. 238 OEGANIC MATTEK Theobserva- The observatioiis tliat were conducted some years ago Glasgow, on the air of several parts of the city of Glasgow by E. M. Dixon, B.Sc, and W. J. Dunnachie, show, as regards its organic impurities, two maxima — one towards the end of August, due to increased temperature which is the principal factor concerned in late summer in the greater activity of all putrefactive changes in nitrogenized material, and the other in winter. The winter maximum simply indicated the amount of tangible floating soot in the air, for no measures were taken for excluding from the absorbing solutions the particles of soot which in the air of such a smoky city as Glasgow are particularly abundant in the foggy days of winter when there is an extra con- sumption of coals. If a small particle of soot is shaken violently with some ammonia-free distilled water, and the mixture is analyzed by the Wanklyn, Chapman, and Smith process of water analysis, it will be found very difficult to extract all the ammonia. Particles of soot contain, in addition to a great deal of ammonia, imperfectly consumed organic matter derived from fires and manu- factories, which, when decomposed by boiling with caustic soda and permanganate of potassium, yield ammonia freely. The proportion of organic matter in air is also estimated by making examinations of the amount contained in that Eain. great air-washer, rain. Eain dissipates the deleterious gases which accumulate and float over towns and cities. It brings down from the higher regions of the atmosphere a more salubrious air, and by the flushing of drains and cleansing of the surface of the country, aids in the preven- tion of the contamination of the air by the exhalations of animals, and by the decomposition of animal and vegetable matter which is incessantly proceeding. The following analyses, made by Dr. Angus Smith, evince very important differences : — ORGANIC MATTER 239 Eain Waters collected during 1869. Albuminoid Ammonia. Part per Million =JHilligr. per Litre. Darmstadt, February . . . . . . "30 Do. during a thunderstorm, May 26 . . "075 Zwingenburg, near Heidelberg, July . . . '15 Heidelberg, June 15 -087 Tyree, Mayi '30 Kelly, Wemyss Bay, south-west wind, June 2 to 15 . "075 St. Helens, west wind, February 18 to March 11 . "15 Do. April 23 -20 Manchester, during a thunderstorm. Rain had fallen heavily just before. Collected about 2 feet from the ground, September 10 . "079 Do. 2 feet from the ground, behind the Literary and Philosophical Society, September . '25 The close agreement in chemical composition as re- gards the amount of organic matter of pure air, and of rain that falls through country air far away from animal and vegetable vitiating agencies, and of well water of aver- age cleanliness, cannot but attract the attention of the analytical student of nature. About "08 of one part per million appears to be the mean amount of albuminoid ammonia contained in air, in rain, and well water that has not received any extra impurities from organic life. The study of the compensatory forces of nature, as manifested in that universal tendency to a restoration to a state of equilibrium of everything that has to some extent departed from it, may well occupy the minds of those whose pursuits lead them to the contemplation of the laws by which this world is governed in special relation to the life and health of its inhabitants. ^ A large kelp work exists on the island. CHAPTEE XIX OXIDES OF CAEBON Carbonic A. Ccirhonic Acid. — The discomfort wliich we experience in badly ventilated rooms was formerly considered to be occasioned by the production of carbonic acid. We now know that it is caused mainly by organic matter, and that an excess of carbonic acid can be borne without ill effects, if the air be free from deleterious gases and an excess of organic impurity. Still the amount of carbonic acid is, as a rule, a measure of other accompanying im- purities in the air, for it is almost always found in bad company, A confidence in our powers of measuring very accurately the minutest quantities of carbonic acid is established by the harmony that has been already shown to exist on page 230, between the results ob- tained by analysts on air of varying degrees of purity, which is still further increased by our study of such an interesting series of observations of air, of various degrees of impurity, as are collected together in the follow - insc Table : — OXIDES OF CARBON" 241 Carbonic Acid in Public and Private Buildings in Leicester, by E. Weaver, C.E., F.C.S> Nature of Workroom or Building. Carbonic acid per 100 of air. 1. Boot and shoe finisher 2. Framework knitter . 3. Ditto ditto 4. Boot and shoe finisher 5. Needlemaker 6. Tailor's workshop 7. Boot and shoe finislier 8. Tailor's workshop 9. Elastic web manufacturer 10. Fancy hosier . 11. Boot and shoe riveter 12. Riveting-room of boot manufacturer 13. National school : Science class-room 14. Ditto Boys' day-room 15. Ditto Girls' day-room 16. Ditto Boys' day-room 17. Ditto Girls' day-room 18. Police Court: The Mayors' parlour 19. Ditto The Town Hall 20. Private house : sitting-room 21. Worsted spinner's preparing-room 22. Ditto doubling-room 23. Town Hall during Quarter Sessions 24. Prisoners' cell in police station 25. Police station : Sergeant's office 26. Prisoners' cell at Town Hall 27. Spring Assizes : Crown Court ; body of hall 28. Ditto Ditto gallery 29. Ditto ISTisi Prius Court ; body of hall 30. Ditto Ditto gallery 31. Newspaper office ; Compositors' room 32. Ditto Machine room 33. Ditto Compositors' room 34. Private house : One foot from floor of bedroom 35. Ditto One foot from ceiling of same room 36. Ditto One foot from floor of bedroom 37. Ditto One foot from ceiling of same room 38. National school : Infants' room 39. Ditto Girls' Room 40. Private school . . . . 41. Ditto ..... 42. Elastic web manufactory : The lower or braid room 43. Ditto The upper or weaving room 44. Public library : Reading-room •528 •532 •408 •460 •287 •306 •259 •217 •211 •493 •172 ■328 •241 •116 •164 ■309 •204 •120 ■098 •304 •106 •174 •153 •103 •203 •081 •196 •290 •134 •169 ■111 ■123 •149 •102 •150 •116 •164 •154 •139 •120 •121 •178 •328 ■206 1 Lancet, July 6, August 3 aud 17, 1872. E. 242 OXIDES OF CAEBON Mr. Weaver points out that the condition of the air in the sitting-room of a private house, No. 20, ilhistrates that of a great number of unventilated dweUings occupied by mechanics and clerks, where gas is burning.^ The higher percentage of carbonic acid in the galleries, as shown by the observations I^os. 27 to 30, testifies to the fact of its ascension with the aerial currents, and that there is no tendency towards accumulation in the lower strata of air from greater specific gravity, as has been sometimes stated. Carbonic Acid in London, Manchester, New York, Cornwall, Portsmouth, and elsewhere. By Drs. Smith, and Bernays, F. de Chaiimont, and others. Percentage by volume. Chancery Court, closed doors, 7 feet from ground March 3 Same, 3 feet from ground Strand Theatre, gallery, 10 p.m. Surrey Theatre, boxes, March 7, 1.03 p.m „ „ ,, March 7, 12 p.ii. . Olympic, 11.30 p.m. .... „ 11.55 P.M Victoria Theatre, boxes, March 24, 10 p.m. Haymarket Theatre, dress circle, March 18, 11.30 p.m Queen's Ward, St. Thomas' Hospital, 3.25 p.m. Edwards' „ „ „ 3.30 p.m. . ■193 •203 •101 •111 •218 •0817 •1014 •126 •0757 •040 •052 ^ All gas shareholders should welcome the advent of the electric light for domestic purposes when they consider the deteriorating effect on the air we breathe of our present illuminating agents. Carbonic acid. Argand eras burner ...... ^46 Petroleum lamp Colza Paraffin candle Tallow . Electric lisrht . •95 1-00 1^22 1-45 OXIDES OF CARBON 243 Percentage by volume. Pavilion, 10.11 P.M., Apriig '152 City of London Theatre, pit, 11.15 p.m., April 16 . -252 Standard Theatre, pit, 11 p.m., April 16. . . -320 Stable for horses : lEcole Militaire . . . . -700 Crowded girls' schoolroom, seventy girls (Pettenkofer) '72.3 Mean amount in a dwelling-house, during the day . "068 In a bedroom at night with closed windows . . -230 „ „ ,, partly open . , . -082 Sleeping cabin of Dublin Canal boat (Cameron) . -95 Unventilated barracks in London (Roscoe) . . -124 Tombs Prison (male department), New York (H. Endemann) . . . . . . . "147 Fulton Market, New York (H. Endemann) . , -084 Manchester streets, ordinary weather . , . •0403 Where fields begin -0369 About middens . . . . . . . '07 74 In workshops ....... -3000 In theatres, worst part, as much as. . . . -3200 In mines, largest amount found in Cornwall . . 2'5000 In mines, average of 339 specimens , . , "7850 Dr. F. de Chaumont's estimations of the amount of carbonic acid in the air of barracks, hospitals, and prisons are interesting : — Barracks. j^LVi 1 ivvroo. Per cent Gosport New Barracks ..... •06 Anglesea Barracks .... •14 Aldershot ..... •049 Chelsea ..... •07 Tower of London .... •13 Fort ELson (Casemate) . •12 Fort Brockhurst (Casemate) •08 Military and Civil Hospitals. Portsmouth Garrison Hospital •097 ,, Civil Infirmary .... •092 Herbert Hospital ...... •047 Hilsea ,, ■057 244 OXIDES OF CAKBON Military and Civil Prisons. AlclersLot Military Prison — Cells . Gosport „ _ „ „ . . . Chatham Convict ,, „ . . . Pentonville Prison — Cells (Jebb's system) Per cent. •165 •13 •169 •09 Dr. Endemann obtained seventeen samples of air from the public schools of America, and found carbonic acid varying in amounts from '09 to "35 parts in 100 ; or, in other words, from more than twice to nearly nine times the normal quantity. He gives the following tabular results, obtained from some of the public schools in New York :— Schools. Per cent Elm Street •146 Roosevelt Street ..... •195 Thirteenth Street, near Sixth Aveniie •281 Thirteenth Street, near Seventh Avenue . •213 Greenwich Street ..... •176 Vandewater Street .... •147 Madison Street, near Jackson . •242 Dr. Breiting made a series of fourteen experiments on the quantity of carbonic acid contained in the air of some schoolrooms, commencing at 7.45 A.M., and continued to 4 P.M. in a room of 251"61 cubic metres capacity, and containing 64 children. The amount of carbonic acid was said to vary from 2-21 to 9 '3 6 per cent (!). Herr E. Schulz found in a clubroom "37 per cent, and in a schoolroom an amount of carbonic acid varying from •14 to '35 per cent. Dr. Snow has concluded from his experiments on animals " that 5 or 6 per cent by volume of carbonic acid cannot exist in the air without danger of life, and that less than half this amount will soon be fatal, when it is formed at the expense of the oxygen of the air." OXIDES OF CAEBON 245 My own determinations of the amount of carbonic acid in air of different degrees of purity teacli no more than do the foregoing analyses, so that I will not trouble the reader at present with any more tabular matter. The purest air — namely, that resting on the sea, and on the sides of the highest mountains — is thus seen to possess rather more than "03 per cent of carbonic acid, which is often increased in the streets of cities to '04, an amount which may be doubled in foggy weather. Much discussion has taken place at various times as to whether carbonic acid is a positive poison or simply an asphyxiating gas. It has now been pretty clearly established that this gas is a distinct poison when diluted with air, but that, in a pure or unmixed state, as it is sometimes found in a beer vat or old well, it extinguishes life in a mechanical manner, by immediately suffocating any one who may be immersed in it. The presence or absence of injurious bodies in air (such as hydrogen sulphide, methyl hydride, hydrogen, organic matter, sulphurous acid, ammonia, ammonium sulphides), and the amount of oxygen it contains, must not be lost sight of in judging of the effects of carbonic acid on the human frame. It has been a subject of wonder that people have been but slightly inconvenienced by an exposure to the air of places where brewing is going on, or soda water is being manufactured, where, indeed, the air contains perhaps about '20 per cent of carbonic acid. In such cases the gas diluted with air is unmingled with unwholesome accessories as organic matter, sulphur compounds, etc. Such air in a closed chamber will give to any one who exposes himself to it a severe headache. We all, indeed, avoid an atmosphere containing "10 per cent of carbonic acid in crowded rooms. Animals can be kept alive for a long period in an atmosphere highly charged with it if oxygen be added. 246 OXIDES OF CAEBOX The body, when exposed to air containmg a large excess of carbonic acid ('30 ]Der cent), suffers a reduction in the heart's action and an acceleration of respiration. These effects have been found to be produced when the influence of the organic matter and other foreign bodies is eliminated. Continual Estimates of the enormous quantities of this gas that the air. ^re clailj and hourly poured forth by our cities would be alarming indeed were we not consoled by the knowledge of the rapid distribution of gases by diffusion/ which tends to maintain a state of equilibrium in the constitu- tion of the air. Dr. Smith assures us that 15,066 tons of carbonic acid are daily passed by the city of Manchester into the air that envelopes it,^ and Dr. F. de Chaumont ■^ The influence of condensed aqneous vapour in tlie air wliicli interferes with this diff'usion is well shown by the hourly experiments of Otto Hehner during a London fog. Percentage of Carbonic Acid by Volume. •10 •08 •09 •04 obtained during the mo- mentary lifting of the fog. •07 It has been declared by Dr. Frankland and others that if London is to be freed from suff"ocating fogs, the importation of bituminous coal into the metropolis must be foi'bidden, and smokeless coal and coke be substituted. If that sweeping measure should ever be carried out, it would be necessary to make it compulsory that every room should have a chimney, as the consumption of smokeless fuel in the shape of coke, etc. , in rooms without flues has produced so many fatal accidents. Smoke, however, is not the only cause of fog, for Prof. Dewar has shown that aqueous vapour has a tendency to condense into mist in the presence of a mere trace of sulphurous acid, which is an unavoidable j^roduct of the combustion of all kinds of coal and coke. ^ M'Dougal {Chemical News, ix. 30), under Roscoe's direction, deter- mined on two different days the amoant of carbonic acid in the air of I^lanchester. As a mean of 46 analyses, the air from the centre of Manchester was found to contain •OSQ per cent of carbonic acid (max. "056, min. •0"28), whilst the air four miles from the city exhibited as a mean of eight determinations '04 per cent. Hence Roscoe concludes that in open places the influence of combustion and respiration processes is completely neutralized by the movements of the air. OXIDES OF CARBON 247 states that 822,000,000 cubic feet of this gas are generated in London per day, or more than 9500 cubic feet every second. In consequence of the possession of most wonderful self-purifying properties, which are partly due to its powers of oxidation and partly to the physical changes that are unceasingly occurring in its condition, through the agency of currents, storms, rains, changes of temperature, etc., the vast aerial sea maintains a uniformity of composition so marvellous as to strike with awe the student of the mighty forces of nature. B. Carbonic Oxide, which is a most poisonous gas, iscartonic a product of combustion, and is to be found in the air of towns, where it is so diluted as to do but slight injury. Public buildings, churches, colleges, schools, barracks, etc., are very often heated by means of coke-burning iron stoves, some of which are provided with troughs and pans of water to counteract the aridity of the air which they are supposed to induce. In the United States anthracite (called in Ireland " Kilkenny coal " and in Scotland " blind coal "), which bears a gTeat resemblance to coke, and is equally objec- tionable as ordinarily consumed, is most extensively used. Dr Derby asserts ^ that " ninety-nine dwelHng houses out of a hundred in Boston are, in whole or in part, warmed by this fuel, burned in iron stoves, or in the iron fire-pot of a furnace, which is but a stove in another form." ]\Iany people of nervous and sanguine temperaments, especially the plethoric, most of those indeed who are sensitive to changes in atmospheric states and conditions, are affected injuriously if they remain for some time in a room or ofiice warmed by an iron stove in which coke is consumed. They experience a languor and oppression ; in fact, a sense of malaise, and sometunes a difficulty of breathing, slight dizziness, confusion of ideas, headache ^ Anthracite and Health. 248 OXIDES OF CAEBON accompanied by a feeling as if a tight band encircled tlie forehead and temples, in one word, tlie symptoms of narcotic poisoning, whicli are speedily dissipated on re- moval to the fresh air. Now, what poisonous gases are generated by the combustion of coke, coal, etc. ? Carbonic oxide, car- bonic acid, the carburetted hydrogen gases, and sulphurous acid. The last named, which is so abundant in the air of coal and gas burning towns ^ (where it serves a useful purpose, being a powerful disinfectant), hardly deserves to be placed in juxtaposition with such deadly agents as carbonic oxide and carbonic acid. The light and heavy carburetted hydrogen gases may be excluded from our consideration, for they pass off in comparatively minute quantities in an unconsumed state. As the carbonic acid, which is produced by the lower layer of burning matter forming the fire, rises through the heated mass above, it unites with more carbon and becomes changed into carbonic oxide. This latter gas may sometimes be seen burning on the surface, and yielding a pale blue flame. When it burns in contact with air, carbonic acid is reproduced. The presence of carbonic oxide is a sign of imperfect combustion. The loss of heating power when this gas escapes from a stove has been estimated at 67 per cent. Carbonic oxide is believed by all to be a most virulent poison, even m the smallest quantities. It is, if quite pure, so free from odour and creates so little inconvenience that, when present in the air, it is apt to be breathed uncon- sciously until the effects of it are felt. It is said to be evolved by the common puff ball when burnt, the fumes ^ One of the causes of the clifRculty -which is experienced in cultivating trees and shrubs in cities is to be found in the presence of this acid, Avhich is highly destructive to certain kinds of plants. OXIDES OF CARBOX 249 from which have been employed for centuries to narcotize bees, before taking the honey from the hive. As both carbonic acid and carbonic oxide gases are given off' in the combustion of coke, anthracite, and char- coal ; and as deleterious effects may be occasioned by either, and especially by the carbonic oxide, any escape of them into the air we breathe is to be carefully giiarded against. Claude Bernard and M. Guerard both assure us that a micdure of these gases is more hurtful than cither respired alone. "V\'Tien coke or anthracite, which do not contain the illuminating gases, and which burn without flame and smoke, are used in our fire-grates, we can generally perceive an odour of sulphurous acid on the addition of fresh fuel, by placing the face close to the mantel-shelf If this acid, w^hich is detected by its irritating fumes, escapes then into our rooms, it may be fairly presumed that the inodorous gases, carbonic oxide and carbonic acid, which are simultaneously developed, are associated with it. Some may inquire, " Is it then uuadvisable to burn coke as a coke in open fire-grates ?" I will answer this question ^'^'^^" by narrating an incident that once came under my notice. An extremely delicate child, afflicted with a pulmonary affection, was ordered, during the prevalence of the easterly winds, to be confined to a suite of rooms, all maintained at one temperature, during both day and night, by coal fires in open fire-grates. As coals were very expensive, the mother after a time adoj)ted the economical measure of burning coke. On entering the sitting-room, after the introduction of the coke, to "sisit the little patient, I experienced a sense of general oppression, of weight about the head, and a difficulty in lireathing aii" which seemed to have lost all freshness. The child was suffering from the symptoms of narcotic 250 OXIDES OF CARBOISr poisoning. She complained of great lassitude and of " a feeling as if a band was tightly bound around the fore- head." The rooms were not again warmed by this fuel. It is to be observed that those who are unaccustomed to remain in rooms warmed by iron coke-burning stoves are more liable to be unpleasantly affected than those who are frequently near them. There is a certain tolerance of the poison of carbonic oxide acquired in time by those who habitually breathe it in small amounts, such as is seen in the case of arsenic, opium, etc. With respect to the formation of carbonic oxide htemoglobulin in the blood — a substance possessing a characteristic spectrum — I must refer to my paper on Coke written some years ago."^ Americans apj)ear to be fully alive to the danger of the poisoning of the air they breathe with carbon mon- oxide, and now employ wrought -iron stoves, which are but slightly, if at all, permeable to gases. They are formed of plates riveted together as tightly as those of a steam boiler, so that the stove is practically of one piece. Stoves constructed of Eussian sheet -iron (rolled iron covered with a silicious glaze) have also been employed. The Germans appear to be only partially aware of the injury attendant on the use of porous stoves." As the majority of their earthenware stoves are covered with a silicious glaze, they suffer rather from the dryness of the air which they occasion than from the escape of poisonous gases. The English seem perfectly insensible at present to this danger to health, although it has been pointed out by myself^ and others for years, ^ "Coke as a Fuel, in Relation to Hj'giene," iu Disease Prevention. " Vide Haller's "Die Liiftimg und Envarmiiug der Kinderstube und des Kranken Zimmers." 3 Op. cit. OXIDES OF CARBON 251 The reader may imagine that, as stoves are furnished with flues, every provision is made for tlie removal of all the products of combustion into the outer air. Unfortunately these poisonous oxides of carbon do not all pass away by this outlet, but enter the rooms which the stove is designed to warm in three ways ; (a) through the iron ; (&) at the junctions of the separate pieces of which a stove is made ; and (c) in consequence of downward currents of air. The second and third modes of exit are readily intelligible, but the first requires some explanation. MM. St. Claire Deville and Troost have discovered that iron and several other metals permit, when heated, the passage through them of the gases of combustion. They write, " The porosity results from the dilatation induced by heat in the intermolecular spaces." The researches of Tyndall on the penetration of metals by gases, and of Graham on the absorption of carbonic oxide by iron, corroborate these experiments. M. Dumas has distinctly shown ^ that a portion of the carbonic acid evolved during combustion is changed by heated iron into carbonic oxide. It is by virtue of the absorptive power possessed by iron that this metal is converted into steel. We learn from Dr. Derby's little work, before alluded to, that so long ago as 1865 Velpeau communicated to the French Academy some observations of Dr. Garret, as to the unhappy influences on the health which attend the use of cast-iron stoves. General Morin interested himself in the matter, and asked INIM. St. Claire Deville and Troost to analyze the air encircling a heated stove. These chemists found : (1) that tubes of cast iron are incapable of maintaining a vacuum ;2 (2) that carbonic ^ Connotes Rcnclus, August 26, 1872. 2 The soil in which pipes containing illuminating gas are embedded has often a powerful odour of it, and is frequently much discoloured. This 252 OXIDES OF CARBON oxide, carbonic acid, and hydrogen gases pass through iron, and to a still greater degree through cast iron ; and (3) that carbonic oxide, absorbed in our stoves by the internal surface of the cast iron, diffuses itself from the external surface into the atmosphere, and that this process goes on continuously. They have besides determined the quantity of the oxides of carbon present in the air surrounding heated stoves, and the proportion of carbonic oxide which permeates through a given surface of a cast- iron stove, as well as that which the metal alDsorbs and retains.^ The passage of the comparatively harmless sul- phurous acid through the crystalline structure of cast-iron stoves is often recognized by its pungent and peculiar smell. Wolffhtigel and Prof Ira Eemsen have expressed doubts ^ as to the permeability of cast iron to carbonic oxide. The latter did not find in the air around heated cast-iron stoves more than "04 per cent of this gas. The Vogel-Hempel (which seems the most delicate known) method^ of testing for its presence does not enable the is, without doubt, partly occasioned by loss through the walls of the pipes ; to guard against which, so far as is practicable, gas companies test their pipes by submitting them to a powerful pressure, and lay them in a concrete, composed of lime, etc. , which adhering to them forms a pi'otectivc coating that lessens the escape. ^ The important experiments of these chemists are contained in Comx>tcs Eendus, T. 57, 1863, and T. 59, 1864. ^ " Carbonic Oxide as a source of Danger to Health in apartments heated by Cast-iron Furnaces or Stoves," in Ncdional Board of Health Bulletin, June 25, 1881. ^ The Professor prefers this method to that of S. von Fodor, in which the blood of an animal exposed to carbonic oxide is shaken -nith ammonium sulphide — a test that reddens the blood if the poison be present and renders it violet if not present. This Vogel-Hempel method consists in allowing a mouse to breathe the suspected air, in killing the animal, in removing a little of its blood and diluting it with water, and in examining it with a spectroscope. The two bands characteristic of pure blood are replaced, in poisoning by carbonic oxide, by a broad indistinct shadow, not to be j-emoved by ammonium sulphide, which causes the disappearance of the bands of pure blood. OXIDES OF CARBON 253 chemist to detect a smaller quantity. Carbonic oxide prob- ably exerts its action in the most minute doses. Whatever scientific chemists may or may not be able to discover, the fact remains that physicians occasionally encounter cases of poisoning from carbonic oxide when coke is burnt in open grates, and that cases with identical symptoms occur when cast-iron stoves are employed. ( Vide cases of poisoning by coke fumes in British Medical Journal, March 6, 1875, and in Lancet of February 14, 1883.) The most pleasant and grateful of all the artificial kinds of heat is obtained by the consumption of coal in open fireplaces, although as at present managed it is exceedingly wasteful. The quality of heat thus imparted is, according to my experience, more conducive to health than that supplied by any other fuel. Ventilation is also promoted by open fire-grates — an ordinary fire drawing about 150 cubic feet of air per minute. A brightly burning fire is an enlivening object, and tends much to render home attractive by its stimulating influ- ence on the spirits. These beneficial impressions on the nervous system are denied us by the cheerless stoves. Provided there is a powerful draught in a fireplace, coke may generally be burnt in it, mixed in small jjropor- tions toith coed, without causing a disturbance of nervous functions. The draught in a chimney can of course be easily increased, if it is insufficient, by either lengthening the flue or diminishing the size of it near the fire. CHAPTER XX PUTREFACTIVE PROCESSES, SEWAGE EMANATIONS, AND EXCREMENTAL FILTH Putrefactive The putrefactive changes that occur in organic matter are processes always associated with micro-organisms, and are generally accompanied by the production of gases and vapours. Warmth and moisture favour, and cold and dryness retard, these putrid decompositions. " The ferments, so far as we know them," writes Mr. Simon,^ " show no power of active diffusion in dry air ; diffusing in it only as they are passively wafted, and then probably, if the air be freely open, not carrying their vitality far ; but as moisture is their normal medium, currents of humid air (as from sewers and drains) can doubtless lift them in their full effectiveness, and if into houses or confined exterior spaces, then with their chief chances of remaining effective ; and ill- ventilated, low-lying localities, if unclean as regards the removal of their refuse, may especially be expected to have these ferments present in their common atmosphere, as well as, of course, teeming in their soil and ground water," Pysemia may probably be produced in the form of putrid infection or intoxication by a septic poison, which can be isolated by processes destructive of every living organism, and also by a septic poison which is the product of certain micro-organisms. ^ Filtli Diseases, in Report of Medical Officer of Privy Council and Local Government Board. New Series, No. II. 1874. PUTKEFACTIVE PEOCESSES 255 Sewer gas, which is one of the media for the convey- sewage ance of the poisons of the filth diseases, includhig*^""""" erysipelas,^ has been found on analysis to be somewhat variable in composition. The examinations of different analysts agree in noting a diminution of oxygen and increase of carbonic acid, with small proportions of hydrogen sulphide, carburetted hydrogen, and sulphide of ammonium. The characteristic foetid odour of sewer gas is due to some organic vapour of carbo-ammoniacal origin, the precise composition of which has not yet been determined. Sewage and cesspool effluvia are well known to be injurious to the health of animal and vegetable life, even when mixed in small quantities with the air. The only forms of life that thrive in air thus polluted are certain of the bacteria and fungi, and other of the scaveng- ing families of creation. As to the fouling of the air we breathe with excre-Excre- mental filth, generally dried and wafted about as dust, and its connection with the spread of such diseases as cholera and typhoid and other of those loathsome filth diseases, the subject is too disgusting to treat of. I would simply refer my readers to two sources for in- formation, if they require any : — first, to disclosures of Dr. Stevens as to the state of Over Darwen, when the terrible outbreak of fever occurred there in 1874, where the people were living with thousands of tons of ex- cremental filth stored amongst their dwellings, exposing a surface of many acres, continually poisoning the air they breathed, and which enveloped them ; secondly, to Mr. Simon's Eeport on Filth Diseases, in which he writes of enteric fever — " Of all the diseases which are attribut- able to filth, this, as an administrative scandal, may be proclaimed as the very type and quintessence ; that though sometimes by covert processes which I will 1 Sanitary Record, June 6, 1879. 256 PUTEEFACTIVE PROCESSES hereafter explain, yet far oftener in the most glaring way, it apparently has an invariable source in that which of filth is the filthiest ; that apparently its infection runs its course, as with successive inoculations from man to man, by instrumentality of the molecules of excrement, which man's filthiness lets mingle in his air and food and drink." CHAPTEE XXI POISONOUS GASES AND INJURIOUS VAPOUES Such as hydrochloric acid gas from alkali works, arsenical vapours from copper -smelting works, hydrofluoric acid from superphosphate manufactories, etc., injure animal and vegetable life, sometimes destroying all trace of the latter for miles around. Then the air is vitiated by bisulphide of carbon from indiarubber works ; ^ chlorine, sulphurous and sulphuric acids from bleaching works ; hydrogen sulphide from chemical works where ammonia is manufactured. It is poisoned also by carbonic acid, carbonic oxide, and hydrogen sulphide, from brickfields and cement works ; by organic vapours from glue refiners, bone burners, slaughter-houses, etc.,^ and by the fumes of oxide of zinc, producing " brassfounders' ague." ^ Paper on the injurious efifects of vaponr of bisulphide of carbon by M. Poincare in ComjJtes Rendus, December 2, 1878. 2 Vide Dr. Ballard's Report on Effluvium Nuisances in Sixth Annual Report of Local Government Board, containing the Supplement of the Medical Officer, 1876. CHAPTEE XXII SUSPEXDED AXIMAL, "\TEGETABLE, AXD METALLIC, AS \VELL AS MINEKAL IMPUKITIES Are the cause of an immense amount of suffering, the non- poisonous exciting lung disease by the irritation occasioned. After the age of thirty-five the metal miners of Cornwall and Yorkshire are liable to a large mortality from a disease commonly spoken of as " miners' rot." The lungs of colliers become black with coal dust. The evil is aggravated by the imperfect ventilation and the laborious ascent and descent by long ladders in some mines. To these causes nearly two-thirds of the total mortality amongst Cornish miners can be referred.^ It may be well to enumerate a few of the trades which suffer in this way :^ — Potters suffer from the dust, and have what is called " potters' asthma,"^ or a fibrosis of lung with consolidation. Knife-grinders are injured by the fine particles of steel, and suffer from what is called " knife -grinders' rot." Millers, sweeps, hairdressers, and snuff-grinders are liable to asthmatic affections. ^ Eeport of the Inspectors of Mines in tlie United Kingdom for 1885. ^ Vide Thacki-ah's work on tlie Effects of Arts, Trades, and Professions on Health mul Longevity. ^ It has been publicl}^ declared that not less than 60 per cent of ■working potters die from diseases of the lungs. SUSPENDED IMPURITIES 259 Buttonmakers ; pin-pointers; mother-of-pearl workers; cotton, wool, and silk spinners;^ workers in flax factories ;^ cotton weavers ;^ stone masons ; grinding and millstone makers*^ and glass makers ; makers of sandpaper and Portland cement. Apart from the very ob\'ious injury to health induced by inhaling dust of various kmds, the circumstances wliich attend the performance of this injuiious work are in. many cases higlily deleterious. The hot, stuffy, damp, rebreathed air in which large numbers of these artisans are bathed during their hours of labour is enough in itself to predispose strongly to the development of disease. Some of the metallic dust to which some workmen are exposed is poisonous. Lead miners, type-founders, glazed card manufacturers, and lacquerers, suffer from lead poisoning. Manufacturers of white lead inhale the dust of tJiis metallic compound. Plumbers and painters are very often poisoned by this metal in consequence generally of a want of sufiicient cleanliness. ^ Vide Dr. Greenliow's investigations in Reports of tlie Medical Officer of Privy Council for 1858-60 and 1861. Since the introduction of modern machinery the evils have been considerably reduced. ^ Dr. Purdon of Belfast writes : — " The Aveavers suffer gi-eatly from chest affections by inhaling the damp air, which has an average tempera- ture of 75° F. Many of them being under 18 years of age. and being obliged to stoop constantly at the looms, get contracted chests, and this, ■with other circumstances, makes the death-rate very high. The rooms in which the dressing of the flax is carried on require to be kept at a tempera- ture varying from 90° F. to 125° F. No one under IS j-ears old is employed in these rooms, and, as it is considered that their lives are shortened several years, they are paid very high wages." — Lancet, October 27, 1877. 2 Vide Eeport of Dr. Buchanan's Inquiry at Todmorden, in York- shire. * Vide French millstone-makers' phthisis, by Dr. T. B. Peacock, in £rit. Med. Journal, October 14, 1876. 260 SUSPENDED ANIMAL, VEGETABLE, METALLIC Workers in brass suffer from copper poisoning, and workers in mercury (such as silverers of mirrors, quick- silver miners), and furriers, from mercurial poisoning. Workmen and women, who make arsenical wall papers, pigments, and artificial flowers, suffer from inhaling the poisonous dust of some compound of arsenic.^ Many persons who do not gain a living by paper or flower Wall Papers, making, but who are unwise enough to adorn tlie walls of their rooms with papers of gorgeous hues, suffer also, and know not what ails them. Mr. Kerley found that a room, 16 feet square and 9 feet high, will have spread upon its walls, provided any of these arsenical papers are hung, from 52 grains to more than 8 ounces of poisonous green colouring matter. It is a popular mistake to imagine that all green papers are coloured by arsenic, or that papers which are not gTeen never contain arsenic, for yellow, blue, pink, mauve, red, brown, olive, sage green, drab, and white wall papers contain this metal. Cobalt blue is composed of 10 per cent of arsenic. Papers of the most brilliant green and otlier colours can be manufactured which are quite free from arsenic. This coloured powder being apt to be removed by trifling causes, is, of course, disseminated through the air, and well merits the epithet of " devil's dust." The researches of Fleck and Hamberg show that this metal is evolved as arseniuretted hydrogen, as these German chemists collected the gas. Lead papers and copper papers are not fanciful dangers. It seems that clothing and furnishing materials are also not exempted from the universal system of poisoning and adulteration Clothing, tliat prevails. The above-mentioned analyst estimated the presence of 5^ ounces of aceto-arsenite of copper or " Paris green " in a green tarletan dress of 16 yards. 1 Vide Report on the Manufacture and Applications of Arsenical Green, by Dr. Guy, in Fifth Eeport of Medical Officer of Privy Council, 1S6-2. AND MINEKAL IMPURITIES 261 Every sample of tarletan examined contained it ; the higher priced qualities of this material possessing more poison than the cheaper varieties. Some kinds of muslin are also coloured with this poisonous material. It has recently been discovered that the bright greens of certain furnishing materials, such as chintz curtains and linings, Furnishing consist of the poisonous compounds — arsenate of iron and chromium. Mr. Foster, of the Middlesex Hospital, who has drawn public attention to this matter,^ found in each square yard of bedroom chintz the metal arsenic, in the form of an arsenate, equal to 45j1q grains of white arsenic, and in each square yard of the chintz lining 20y^ grains of this deadly poison. On estimating the number of square yards of chintz and lining in the bedroom of a gentleman who had suffered for some time from nausea and nervous depression, it was proved that there was arsenicum present in his sleeping apartment equal in amount to 2 6 ounces of white arsenic. These poisonous furnishing materials have been sold to the public for the last twenty years. Children have been poisoned by white arsenic, with which " violet powder " has been found to be adulterated to the extent of 25 per cent, and by lead, from inhaling the dust that proceeds from inferior kinds of American cloth with which perambulators are lined. The public is exposed to danger : — From Arsenic in the employment of packs of cards, enamelled cooking utensils, green lamp shades, green carpets, green Venetian blinds, Berlin wools (green, blue, and rose), kindergarten toys, candles, water colour paints, gloves and stockings (aniline dyed), papers covering confectionery, glazed paper 1 Lancet, August 11, IS 77. 262 SUSPENDED ANIMAL, VEGETABLE, METALLIC collars, and starched linen, artificial flowers and grass, anti-dry rot preparations, etc. Arsenite of soda and arsenite of alumina are used in calico-printing and fixing the colours. From Lead in the use of soda-water, lemonade, beer, tinfoil around chocolate and other sweets, floor-cloths, snuff, tea, vermilion red flowers, wall paints, American imitation leather, and many other articles. Many contrivances have been devised for the protec- tion of the lungs of workmen who have to support " dear life " by engaging in the foregoing and other unhealthy callings ; but there is in this field a great opportunity for those with talents for invention to exercise them in be- half of these suffering thousands. In addition, the ventilation of workshops should be more attended to, for at present the admission of fresh, and the expulsion of foul, air is about the last thing thought of. Happily something has been done in this Knife- direction not only amongst the Sheffield knife-grinders,"^ grinders. |^^^^ ^^^ ^l^g miucs of Durham and ISTorthumberland, and the gi^eatly diminished death-rate of these poor mechanics ^ What distressing truths have been for years presented to the public by the late Dr. Hall, of Sheffield, respecting the average dirration of life amongst the steel-grinding trades of that city ! "What fearful waste of life is disclosed in Dr. Wynter's summary of Dr. Hall's observations ! — "Dry grinders of forks, 29 years : razors, 31 years ; scissors, 32 years ; edge tool and wool shears, 32 years ; spring knives, 35 years ; files, 35 years ; saws, 38 years ; sickles, 38 years." Some improvement has undoubtedly been effected of late years, as the report of the Medical Officer of Health, con- tained in Dr. Hall's last communication to the profession shows ("Remarks on the Effects of the Trades of Sheffield," Brit. Med. Journal, October 14, 1876), through the introduction of fans, but much still remains to be done. In 1874, 92 grinders died ; average age at death, 46 years. In 1875, 111 ,, „ „ ,, 42-5 ,, AND MINERAL IMPURITIES 263 and colliers from pulmonary disease proves the advantage of free ventilation. Sufficient evidence has been adduced to show the magnitude and enormous importance of the subject. Medical literature and the columns of the medical press have for years been teeming with instances of the whole- sale destruction of health and life by these terribly dangerous occupations. In brief, the mortality induced by impure air charged with poisonous and non-poisonous dusts is simply an ignorant waste of human life. The air that we breathe, we who are not enoao^ed in these unwholesome avocations, is full of dust — a hetero- geneous mixture of particles of organic and inorganic origin. From the amount of spores (250,000) in a single drop of fluid, Mr. Dancer calculated^ "that 37 J millions of these bodies, exclusive of other substances, were collected from 2495 litres = 88 cubic feet of the ' air of Manchester,' a quantity which would be respired in about ten hours by a man of ordinary size when actively employed." It may well be said, " Surely this dust that we all of us breathe must be hurtful. Is there no pro\dsion in nature for counteracting its baneful influence ?" There is no doubt but that the less of it we have the better for us. We are taught in every possible way, if we will but be guided by the teachings of nature, to be clean. If people will but admit an abundance of Nature's great disinfectant, pure fresh air, into their houses, and at the same time keep themselves and their houses clean, they will not be injuriously influenced by the dust of the air. ^ "Microscopic Examination of the Solid Particles of the Air of Man- chester." Proc. Lit. and PhUosopli. Socy. of Manchester, vol. iv. series 3, 1867-68. CHAPTEE XXIII EMANATIONS FKOM GEOUND HAVING DAMP AND FILTHY SUBSOIL SUBSOIL AIE, CHUKCHYARD AIE, MARSH AIE The air of towns, and also that of Louses, is often de- teriorated by emanations from wet and filthy subsoil. It has been distinctly proved both in this country and in America that the death-rate of consumption is diminished very considerably by drying the subsoil. Eheumatism, and heart-disease which is so frequent a concomitant of rheumatic affections, are lessened by the same beneficial measure. Emanations from filthy soil produce diarrhoea in that part of the year, namely autumn, when there is a predisposition to intestinal disorders. It is very unwise to allow the soil close to houses to be defiled by filth, for the fires of a house, creating a force of suction, draw into the house the air contained in the surrounding soil, as well as of that on which it is built. The popular impression that the atmosphere ends where the ground begins is a very widely spread delusion. Most soils are more or less porous. A house built on a gravelly soil stands on a foundation composed of a mixture of two parts of small stones, and one part of air. The air may give place to any gas or to water. The porosity of soils may be well illustrated by the following experi- ment devised by Pettenkofer.-^ ^ Cliolera : How to Prevent and Eesist it, by Dr. Max von Pettenkofer. Translated by Dr. Hime. EMANATIONS FEOM DAMP AND FILTHY SOIL 26i "If a person blows, as represented in the figure, on the surface of the gravel, the water in the U-shaped tube will be seen to alter its position, the level of the side next the person who is blowing becoming lowered, and the other proportionately elevated. The depression of the fluid is caused by the force of the air blown through the gravel. This air ascends from the bottom of the Fig. 17. A, a tall and large glass tube filled with fine gravel, in the axis of which stands a very small tube, B, open at both extremities, the upper being curved, and connected by a piece of indiarubber tubing, C, to a U-shaped tube, D, containing water. B, fine gravel. gravel through the small glass tube, passes through the indiarubber tube, and thus reaches the water." Eemembering the force with which the wind often strikes the surface of the ground, with a pressure during a hurricane, amounting, according to some, to 36, and to others, of 50 pounds on every square foot, it cannot be a matter of surprise, in the light of the above experiment, that foul and pestiferous air from the filthy earth beneath, and close to our habitations, should be introduced into them, aided, as this driving force is, by the suction power 266 EMANATIONS FROM DAMP AND FILTHY SOIL created by the fires and lamps, etc. I have encountered instances in which foul air from drains, cesspools, and from leaky gaspipes, has been drawn into houses great distances, and has caused ill-health and death from the continued poisonous condition of the air. Pettenkofer, of Munich, relates a case -^ where gas was found to have travelled a space of 20 feet from the street main into the house. Dr. F. de Chaumont refers ^ to a case that occurred to Dr. Fyffe, in which the foul air from a cesspool was sucked into a house a distance of 27 feet. It is impossible for any public health physician to speak in temperate language of the crime of erecting houses, and of allowing houses to be constructed, on filthy and sodden foundations. No one can possibly enjoy for any length of time good health in such buildings, and the diseases from which the inhabitants suffer are generally influenced so un- favourably by the insanitary conditions in which they exist, as to have a tendency to death rather than to recovery. I once visited a little town on the coast, swept by the purest of breezes — the sea breeze — where scarlet fever was prevalent. In one part of the town, where the cottages were kept in a cleanly and wholesome state, and were built on virgin soil, the disease showed itself in a mild form, and not a death occurred. In another part of the town nearly every family lost one or more children, killed almost immediately by the poison. I went into one of the cottages where all the children, five in number, were destroyed, and talked to the poor afflicted parents. The father, pointing to a loose plank of the floor, moved a portion of it aside. I pushed my walking stick down, and stirred up the soil over which this family had been living. It was fluid filth. The cottages in which these fatal cases occurred had been erected on ground made up ^ O}). cit, - Lectures an State Medicine. SUBSOIL AIR 267 of stinking fish, brickbats, eartli, and every kind of de- composing debris. Subsoil Air. — The chemical composition of the air subsoii air. contained in soils ^ has been investigated by many chemists, such as Boussingault and Lewy, Pettenkofer, Fleck of Dresden, Nichols of Massachusetts, and others. A large excess of carbonic acid, a little carburetted hydrogen, a trace of ammonia and hydrogen sulphide (when the ground water possesses sulphates), have been discovered. They all seem to be unanimous as to the much greater quantity of carbonic acid in ground air than in atmospheric Fig. 18. air, and as to its great variability in amount. The former fact is well demonstrated by an experiment and illustra- tion, contained in Mr. W. IST. Hartley's Air and its Relation to Life. A flask full of clear baryta water is connected by tubes to a vessel filled with earth, and again attached to this is another flask of baryta solution. By drawing air through the whole system of bottles the amount of in- soluble carbonate of baryta, formed in the flrst flask by the carbonic acid in the air, may be compared with that in the second flask, produced by the carbonic acid in the soil. ^ Vide Fodor's Hygienische Untersucliungcn ubcr Luft, Bodcn und Wasser, 2e Abtlieilung Boden und Wasser, p. 99, et seq. 268 CHUECHYARD AND MAESH AIR Pettenkofer discovered that the amount of carbonic acid in ground au' varies in different seasons of the year, that it reaches its minimum from January to May, and then rises steadily to its maximum from July to Novem- ber. The occurrence of the maximum in autumn, is . probably the result of high temperature and excess of decomposing organic matter. The exact period of the minimum has not been so clearly determined. The analyses of the air of soils of various kinds that rest on different formations, the degree of porosity of soils, and the connection, if any, of the same with such diseases as diarrhoea and certain forms of continued fever, is an extremely interesting field for research which has been but barely opened out. That there is a very decided relation between the state of the ground air and the continued prevalence in a given locality of diarrhoea at certain seasons is a matter of strong probability. It has been suggested that the amount of carbonic acid in ground air be taken as indicative of the degree oi impurity. As the animal poisons seem to attach them- selves always to minute particles of animal and vegetable organic matter in a state of decomposition, a study of the comparative amount of organic matter in the ground air of soils cannot well be omitted. Churchyard TJic Air of ChurcJiyarcls and Vaults is richer in car- bonic acid than gTOund air, and contains often a putrid organic vapour, hydrogen sulphide, carbonate of ammonia and sulphide of ammonium, and elementary forms of animal and vegetable life. Marsh air. TJie Air of Marshcs contains also a large excess of carbonic acid and organic matter. The experimental evidence which at present exists as to the presence of a bacillus malariffi (Klebs) in the air of marshes where ague abounds, and as to its existence in the blood of those suffering from this disease, is insufficient and uncon- CHURCHYARD AND MARSH AIR 2G9 vincing.-^ Great quantities of living organisms and organic debris, carried upward for a certain distance by the ascensional force afforded by the evaporation of water, are discernible on microscopic examination. Carburetted and phosphuretted hydrogen gases are evolved by marsh land, and sometimes hydrogen and ammonia. The time to be selected for making observations on the composition of marsh air is in the early morning or evening, when the density of the air and the deposition of dew prevents a free admixture of the impure with the higher strata of pure air, or during a hot, sultry noon when no breeze keeps the air in motion. I have made analyses of the air of marshes that are hotbeds of ague, taken on a fine day, whilst a gentle wind blew over them, and have found no more organic matter in such air than in pure air collected simultaneously on high hills. This fact is only another proof of the marvellous purifying properties of air, and the tendency throughout nature, not only in the air, but in the earth and in water, to self-purification, and to the restoration of an equilibrium. ^ Vide information on this subject in Dr. H. Gradle's Tvork on Bacteria and Tourmasi-Crudeli's illustrations, in Joicrnal d' Hygiene of March 31, 1881. CHAPTEE XXIV THE DELETERIOUS EFFECTS ON HEALTH OF THE AIE OF OUE HOUSES The air of ^o dilate Oil sucli a subject would be indeed needless to students of preventive medicine, if a general recognition existed of tbe fundamental principles on whicb the re- lations between a state of health and disease, and between a condition of health and the circumstances which tend to promote and deteriorate it, rest. The old notion that disease is a sort of maKgnant demon that takes possession of the body, and requires to be combated and exj)elled by some violent means, is still a very widespread one, even amongst some of the rural rank and file of the medical profession, and any modern ideas as to the relations of health to the conditions of those surroundings of life, namely, the air we breathe, the water we drink, and the food we eat, which so seriously influence it for good or evil, are often received with a smile of incredulity. The public surely ought not to require a skilful physician to teach them what common-sense inculcates, that perfect bodily and mental health cannot be enjoyed by those who are inattentive to the cleanliness of the body, and of that which enters it. There is, unhappily, an increasingly exaggerated importance attached at the present time, by great numbers of people, to the injurious effects of impure water. It is the fashion to ascribe almost every indis- THE AIR OF OUK HOUSES 27l position to the condition of the water supply. The ten- dency to run into extremes about most matters, and to ride hobbies, is but too frequently observed. On the other hand, there does not yet exist in the public mind an adequate conception of the extent of the danger to the health which is induced by a continual immersion of the body in impure air, notwithstanding the efforts that have been made in this direction for the enlightenment of the public mind. For a quarter of a century I have been preachiug on this subject, pretty much in the language of my First Annual Eeport as Medical Officer of Health for 1874, which contains the following passages: — Theteaching " It should not be necessary to point out the blessings o^g^g*'^ of pure air, and the e^dls resulting from the inhalation of a vitiated atmosphere. Excluding from consideration the effects of an exposure to the foetid gases of organic decomposition, which act like other poisonous chemical agents, it may be said that offensive smells, the products of putrefaction, are not only injurious in themselves, but serve as danger signals bidding men to beware. By acting as depressants, and as reducers of bodily Adgour, they tend to make the system more prone to be attacked by disease. As the smell of gas in a house warns men of the presence of a body dangerous when diffused through it, so an offensive smell is a signal of the possi- bility of the presence of the poison of a disease. A stench may or may not be associated with a disease poison, and no one knows when it is and when it is not thus accompanied. As a means of warning to those exposed, an offensive smell is useful, but we must re- member that agents which destroy the stink of filth may yet leave all its powers of disease-production undiminished. Disease poisons or ferments, although not alw^ays in the companionship of stinks, are often so, and it behoves every one to remove the cause of stinks, and prevent 272 THE DELETERIOUS EFFECTS ON HEALTH OF their recurrence. Disease fernients may fatally assail the human body in closes quite unappreciable to the most acute sense of smell. All unpleasant smells are to a certain extent deleterious, although infinitesimally so perhaps. Pleasant odours, if in excess, become injurious to some persons. Those who visit the farms devoted to the cultivation on a large scale of the rose and jessamine in France, for the manufacture of scents, experience, after being exposed to these perfumes for a little time, severe frontal headache and lassitude, symptoms which speedily pass away when they emerge from these odoriferous tracts of country. It should always be remembered, then, that smells which offend the senses, even when not accom- panied by disease poisons, act deleteriously on the health of those frequently exposed to them, by depressing the system, thereby lessening the resistance of the frame to the approach of disease, and by diminishing the bodily vigour, rendering the vis medicatrix naturae a less chance of success in preventing disease from destroying those attacked." The effect of all the exertions of that class who have been called sanitary reformers is, that large numbers of people tacitly acknowledge that the constant inhalation of air rendered impure to the senses of sight and smell is Result of. likely to injure. It seems very difficult for the public to amoiF^ttiiego a stcp further and cease to offer opposition to the public. behef which is rooted in the mind of every public health physician, that frequent exposure of the body to air that is deteriorated in quality either by having been rebreathed without purification, or devitalised, tends to a reduction of the vital powers, a state which is favourable to the development of a perversion of healthy action, the pre- cursor of disease. Dr. Eichardson has, in his attractive style, most candidly spoken out on this subject in his Diseases of THE AIR OF OUR HOUSES 273 Modem Life. " It is this devitalised air in our over- r»r. Richard- crowded towns and cities, where there is no vegetation of"he^uni-'^ ' to revivify it, which we distinguish as something so dif- ^'"^ai sys- ■^ ' ^. ^ temofair lerent from the fresh country air that streams over forest deteriora- and meadow. It is the breathing of this air that makes *'™" the child of the close town so pale and lax and feeble, as compared with the child of the country. It is this air that renders the atmosphere of the crowded hospital so deficient in sustaining power. It is this air that gives to many of our public institutions, in which large numbers of our poorer, ill-clad, uncleansed masses are herded together, that 'poor smell,' as it is called, which is so depressing both to the senses and to the animal power. " In many private houses, houses even of the well-to- do and wealthy, streams of devitalised air are nursed with the utmost care. There is the lumber-room of the house, in which all kinds of incongruous things are huddled away, and excluded from light and fresh air. There are dark understairs closets, in which cast-off clothes, charged with organic debris of the body, are let rest for days, or even weeks, together. There are bedrooms overstocked with furniture, the floors covered with heavy carpets, in which are collected pounds upon pounds of organic dust. There are dressing-rooms, in which are stowed away old shoes and well-packed drawers of well-worn clothing. There are dining-rooms, in which the odour of the latest meal is never absent, and from the cupboards of which the smell of decomposing fruit or cheese is always eman- ating. There are drawing-rooms, in which the scent of decayed roses, or of the varnish from the furniture, or of the dye from the table-covers, is always present. There are kitchens in which there is the odorous indication of perpetual cooking. There are sculleries where the process of ' washing up ' seems to be in permanent action, and where the products of change from stored bones, T 274 THE DELETERIOUS EFFECTS ON HEALTH OF potato parings, recent vegetable green food, and other similar refuse, are abiding. There are water-closets in which there is at every time of daj or night a persistent, faint ammoniacal organic odour. " The process of devitalisation of the air is again effected, locally, in human habitations, by the presence in it of the lower forms of life. When in the dwelling- house dogs, cats, tame mice, birds, squirrels, are kept in such numbers that the odours of the animals are percep- tible ; when flies cover the ceilings, and a mould collects on the walls, then the air teems with myriads of minute living forms, and with organic dust. Every particle of this matter induces deterioration of the air that feeds the lungs." Although many may smile on reading the foregoing extract, every one with any experience of life must admit the truthfulness and fidelity of the sketch. The prin- ciples that should be firmly implanted in our minds are involved in the consideration of such golden rules as the following : — w?th°wMch -'-• -^^® exposure of the body continually to a smell, be the public it a pleasant or an unpleasant one, is deleterious to mind should ■■ -•, ■■ be imbued. -Heaitn. 2. An odour that is at first pleasant, generally soon becomes objectionable. The little is grateful, but a constant excess of the perfume is hurtful. 3. An unpleasant odour may or may not be in the com- panionship of a disease ferment, and no one knows when it is or when it is not so accompanied. The putrid gases of decomposition will not in themselves give rise to the development of either of the zymotic diseases. 4. When an unpleasant odour is not associated with a poison of a disease, it is nevertheless deleterious to the health of those constantly subjected to its in- THE AIE OF OUK HOUSES 2 / 5 fluence. I know that this statement will be doubted by some. Several instances of its truth have oc- curred to me. For example, a man in good health took a house close to one of those public trade nuisances where the smell of melted tallow taints the air, and suffered in consequence severely from nausea and diarrhoea. Here no septic ferment could have existed, such, for example, as is supposed, with good reason, to be mingled with the odours of the dissecting-room. 5. The healthy human body often becomes inured, after long exposure, to un|)leasant odours, and at length hardly notices them, if always immersed in them. Those actively injurious effects of impure air, such as nausea, diarrhoea, etc., often gradually pass away. If a man is possessed of exceptional powers of vigour, which enable him to maintain a successful warfare with those depressing influences that surround him, he may live for a great many years in tolerable health, although defying the laws of nature. The large majority become affected in course of time, if not suddenly attacked by a passing epidemic (to which a person living under unhealthy conditions is especially prone), by the insidious progress of a chronic disease. 6. Air, which is not defiled by the offensive productions of decomposition, may contain organic matter in the form of dust or vaporous emanations, as carriers of the specific poisons. A cursory examination of these dicta may lead some one who is indisposed to remove a nuisance from his pre- mises to urge that the wdiole question as to whether an odour is or is not injurious to health, rests on the point as to whether it does or does not annoy the person con- 276 THE DELETERIOUS EFFECTS OX HEALTH OF tinually exposed to it. Anytliing wliicli persistently worries, disturbs, and irritates, is undoubtedly dele- terious to health, although the injury may be so in- finitesimal that it cannot perhaps be measured or demonstrated. It will probably scarcely incommode the resilient disposition of the young and healthy animal that is naturally cheerful, and disposed to look on everything with a couleur de rose hue. The human body by acclimatization can adapt itself to wondrously different circumstances, although a certain injury is received by so doing, but it never reaches the period of old age if continually bathed in impure air, although that air may have long ago ceased to offend the olfactory nerves. The comparative freedom of the sewer men of Paris from cholera and other z}Tnotic diseases, the absence of any marked injury to health during the year that the Thames was so odoriferous, and of any excess of zymotic disease in the neighbourhood of Moatfaucon, in Paris, where much of the filth of that city is stored jDreparatory to its conversion into manure for agricultural purposes — assertions which have encouraged the opinion that a constant exposure to morbific ferments or contagia diminishes the risk of being injured by them — will perhaps be urged as contradicting these views. It is a well - established rule, however, notwithstanding the existence of certain much-talked-of supposed exceptions, which is recognised by the whole of the medical pro- fession, that there is a gi-eater mortality amoiigst those who are exposed continually to impure air than with others who are not so circumstanced, and that the diseases from which the former suffer are of an asthenic type tending to death rather than to recovery. Air of the Tlic amount of oxygen in the air is diminished, and town!^and ^^^^^ °^ ^^® carbouic acid is increased by respiration, and cities is not combustiou and decay of organic matter, the former, to THE AIR OF OUR HOUSES 277 speak in popular language, being tlie lifegiving and so impure as purifying principle, and the latter its noxious substitute, generaii^ Thanks to the diffusive powers of gases, and the effects of thought, wind, and to the currents produced by the fires of large towns, and last, but not least, to the wonderful cleansing properties of fresh air, the air of the streets of our towns is not so impure as might be expected. The air of our An- of our i houses, on the other hand, is generally very impure, exwbitifthe because the continuous admission into them of pure air, presence of and expulsion of that which has been used up, is rarely amounts of thought of, or if so, is seldom efficiently managed. In deflimg respiration we deteriorate an enormous quantity of air (about a gallon a minute), and we are continually throwing off carbonic acid and organic matter. Every time we breathe, and we breathe about eighteen times per minute, we expel 30 cubic inches of air, which amount contains 1"29 cubic inch of carbonic acid, or 16"1 cubic feet in the 24 hours. In the 16 cubic feet of carbonic acid, there are about 7-2- ounces by weight of charcoal. Others say that the amount of charcoal is 160 gxains per hour = 8 ounces in 24 hours. Air which has been once breathed should never be breathed again until it has been mingled with fresh air, in order that the impurity which it has acquired may be removed from it, and that it may regain a wholesome amount of moisture. The overcrowding of schoolrooms is a subject respecting which much has been said in the way of protest for years. It has been shown by Eoscoe in his experiments on the air of schoolrooms that 10 cubic feet of air per minute per head is insufficient to remove completely the organic putrescent matter, and yet schoolrooms are to lie found where there is even less than 4 cubic feet for each child. Architects design houses, local boards pass the plans, builders erect places which are totally devoid of all provision for the admission of fresh air, and may be except in the crudest manner. 278 THE DELETEPJOUS EFFECTS O'N HEALTH OF likened to Holes of Calcutta on the small scale. As for arranging for a change of air by the passage through a room of warmed fresh air in winter, and cooled fresh air in summer of a healthful degree of humidity, such a proceeding is never dreamt of. The drowsiness which often oppresses our congregations may frequently be more Absence of correctly ascribed to the absence of any attempt at *"^ ^**.^"li' Ventilation than to the cause to which it is generally to ventilate ^ "^ buildings attributed. Who is there not acquainted with the un- wholesome atmosphere to be met with in nearly every public building ? whilst our drawing-rooms, dining-rooms, and bedrooms, even in the best houses, are too often in a most disagreeable state of what is termed " closeness." On once remonstrating with the verger of a church in a suburb of London with respect to the oppressive state of the air during the Sunday afternoon, and on suggesting to him the propriety of opening freely the windows duriuCT the interval between the first and second services, he expressed his disapproval of my proposition by in- forming me that if he followed my advice " the church would catch a chill." I have always maintained, and increased experience has only confirmed my previous conviction, that the impure condition of the air of our houses, be they factories, public buildings, or dwelling-houses, has much to do with the great prevalence of such diseases as phtliisis pulmonalis, bronchitis, and pneumonia, which together make up nearly one quarter of the total mor- tahty ; and if we could strike a telling blow at that great universal evil — namely, poisoning by impure air — we should do much to save life. Unventilated and overcrowded workshops and schools are, moreover, the nurseries of strumous diseases in general, which sap the strength of the community. During the decennial period 1865 to 1874, not less THE AIR OF OUR HOUSES 279 than half a million individuals died of phthisis, and three-quarters of a million of people were destroyed by other diseases of the lungs in England. The dependence of these diseases on vitiated air was maintained by Dr. AHson^ as long ago as 1824, by Baudelocque in 1834,^ and very likely long before those years. The facts that an increase of phthisis pulmonalis occurs Phthisis ■ J_^ • • J.^ 1 -J. r i pulmonalis. ^an passu with an mcrease m the density oi a popula- tion ; that in manufacturing centres, where the males are the chief workers at indoor employment, the male death-rate is the highest ; and in others, where females are principally required at indoor work, they suffer most ; that in agricultural districts, where the men spend nearly all their lives in the open air, and the women scarcely ever leave their cottages, the female death-rate from this disease is higher than the male : — all point to this inevitable conclusion. Dr. Parkes mentions a remarkable cuxumstance illustrative of this connection as having occurred in Vienna. In the badly-ventilated prison of Leopold- stadt, 51 "4 per 1000, whilst in the well -ventilated House of Correction of this city, 7 "9 per 1000 died of consumption. Dr. Guy's evidence before the Health of Towns Commission contained most striking statements as to the journeymen printers of London. He divided them mto three classes : — The 1st Class consisted of men who worked in rooms where they had less than 500 cubic feet of air per head. Of these 12-|- per cent had spat blood, and a like pro- portion had been subject to catarrh. The '2cl Class comprised men who had between 5 and 6 cubic feet of breathing space per ^ Edinhiorgh Meclico-CMrurgical Transactions, vol. i. - Etudes sur la maladie scrophulciisc. 280 THE DELETEEIOUS EFFECTS ON HEALTH OF individual, and amongst them intermediate effects were noticed. The 3d Class was composed of men who worked in sliops where they had more than 600 cubic feet per individual, and amongst these only 4 per cent had suffered from spitting blood, and only 2 per cent from catarrh. The published opinions of Dr. Farr, Dr. Marcet, Mr. Welch,-^ Dr. Eansome,^ Dr. Parkes, Dr. Austin Flint, and Sir James Clark, are all to the same effect. The continued employment of rebreathed air for respiratory purposes, and its bearing on the develop- ment of that terribly fatal strumous disease, pulmonary consumption, has been vigorously brought before the world by the late Dr. MacCormack, of Belfast,^ who, to show his enmity to used-up air, was said to sleep always, during winter and summer, as did also his family, with the windows of their bedrooms widely opened. The testimony of the most able physicians of this and other countries ; the results of inquiries as to the prevalence of this disease amongst the picked men of the armies and navies of the world ; the reports of hospitals for consumption, and of commissions and committees ap- pointed to make special investigations as to jails, work- houses, and schools : all, in various degrees, corroborate this opinion. There are one or two apparent exceptions to this rule in Iceland and the Hebrides, which are worthy of attentive consideration.* The beneficial effects ^ "On the Nature and Variations of Destructive Lung Disease, as seen amongst Soldiers, and the hj'gienic conditions under which they occur." ^ '' Foul Air and Lung Disease." ^ " Consumption, as engendered by rebreathed air." * Vide Dr. Morgan, on the " ISTon-prevalence of Phthisis in the Heb- rides and along the N.W. Coast of Scotland." — Brit, and Foreign Medico- Cliirurgical Review, 1860, vol. xxvi. p. 483. Vide controversy in Medical Periodicals, during 1S68 and 1869, between THE AIR OF OUR HOUSES 281 on tliis disease of sea air, the air of high latitudes and elevated regions, furnish an indication as to its cause. That impure air vitiated by respiration is the one great cause of pulmonary consumption, which may be trans- mitted from parents to children for generations, needs no proof, as it rests on such a mass of evidence. It is probable that foul air, by impairing the appetite and thus hindering nutrition, may render the body suscep- tible to the development of the virus peculiar to the disease. If it should ultimately be shown that the bacillus tuberculosis (vide page 3 6) is the agent contained therein, through which the poison of phthisis pulmonalis is com- municated from one individual to another, still further confirmation would be afforded as to its causation. Pathogenic micro-organisms, whilst influenced by tem- perature and other circumstances, flourish in media containing organic matter, accordingly a pure air is not so likely as an impure one, either to contain nourishment for any elementary forms of life productive of disease, or to be the carriers of the same. Dr. Fuller writes ^ " the more closely human beings are congregated together the more abundant will be that wonderful micro-organic life which goes on unseen, and often unheeded, around us and about us, exerting its baneful influence on the crowded millions packed away in our great cities in- sidiously eating away their lives with consumption." Some animals that are kept for a long time in con- finement are affected in a manner similar to man. The monkeys of our Zoological Gardens are well known to die in great numbers from this disease. Dairy cows that tlie late Dr. MacCormack, Dr. Leared, Dr. Hjalteliu, aud others, as to Avhether Phthisis is or is not indigenous in Iceland. ^ Soxiih Africa as a Health Ecsort. 282 THE DELETERIOUS EFFECTS ON HEALTH OF are kept immured in close, ill-ventilated slieds in cities and towns also suffer from a form of tuberculosis.^ strumous As regards the connection between the other strumous diseases and t -, t iij_ ly • j. i i} i overcrowd- discascs and overcrowding, abundant proof is to be found ^'is- if looked for. Scrofula once prevailed to such an extent in the Asylum of the house of Industry, Dublin (so Carmichael aflirms), that it was regarded as a contagious complaint. The air was so impure in consequence of the excessive overcrowding as to be unendurable when the wards were first opened in the morning, and to be " but little better " during the day time. The communicable eye disease, so common in asylums and schools for children, is another of the legacies of our overcrowding. The injurious effects of rebreathed air, and the want of any provision for ventilation, is not only seen in the public schools for the poor, but in private schools for middle classes. I once visited a " College for Young Ladies," which contained rooms 12 ft. X 9 ft. x 8 ft. high, in each of which slept six girls, between the ages of 10 and 17, in two beds. ISTot a fireplace or other means of ventilation existed. This school, which was a popular one, had, like a concertina, a wonderful power of expansion — those who could not be accommodated with beds being stowed away on floors and in day rooms. That young women, at the most delicate period of their lives, should be thus injured by thoughtless parents, who care more for the cheap purchase of a smattering of ac- complishments than a healthy frame, is a great evil. Every school should be under the supervision of the Health Authority of the district in which it is situated, so that a guarantee may be afforded to the State that the young be not subjected to the cruelty of slow poisoning by foul air. The relation between such lung diseases as bronchitis •^ Tide Annalcs d' Hygiene, voL ii. p. 447. THE AIR OF OUR HOUSES 283 and pneumonia, and the unwholesome condition of the Diseases of air of our dwellings, has not been sufficiently recognized hyJ,rlanTlnd the medical profession and the public. One of the most i^p^^e air. common causes of an attack of bronchitis is a sudden exposure of the bronchial mucous membrane to extreme meteorological conditions of air. A man who breathes for some hours the hot and dry vitiated air of an un- ventilated room is prone to be thus affected on passing out into cold damp night air. If debilitated from any cause, the inflammation may affect the substance of the lung, and the man will have pneumonia. Eapid alternations of temperature and moisture are apt to be attended with risk to health to those who have passed the period of youth during which the body quickly adapts itself to altered atmospheric conditions. The body, in the middle-aged and old, always experiences a difficulty in suddenly accommodating itself to extreme ranges of temperature. By substituting for the overheated and impure air of our houses and public buildings a pure wholesome air, of a temperature adapted to our sensations of comfort, by the establishment of an efficient system of ventilation, we shall avoid the danger of sudden and extreme changes which continually menaces those organs in which the blood and air meet. A Fellow of the Eoyal Society has recently publicly declared that there is not a perfectly healthy dwelling- house in the country. Although that at first sight seems an exaggerated view, yet it is not far short of the truth. I only know of one room in this country in which there *^"<^ ^^ii- ., . . , ^^ "^ o ^ ventilated IS any good ventilation, namely, the House oi Commons, room iutue All the patents that have ever yet been devised are ^°'^"^''^'" inefficient and faulty, although some very elaborate ventilating and warming arrangements for the comfort of guests have of late been established in some of the continental health resorts, notably at the large Kursaal on 284 THE DELETERIOUS EFFECTS OX HEALTH OF useiessness the Maloja plateau of the Upper Engadine. Amongst the dozens of contrivances that are described and figured in F. Edwards' book, entitled Ventilation and Heat, not one ful- fils the requirements of a good ventilator, namely, the con- stant passage into each room of pure air of a healthful degree of humidity — warmed in winter and cooled in summer — with an accompanying provision for the immediate removal of that which has been breathed, in such a manner that no draught is created. The most modern are Tobin's tubes, Fischer and Stiehl's tubes buried 9 or 10 feet in the gTound, whereby air is warmed 8° or 9° F. in winter and cooled 12° or 13° F. in summer. Motive power for the circulation of air has of late been obtained by gas jets, by a jet of water (Messrs. Verity's plan), and by exlioAisting cowls and other devices. To intercept the fuliginous particles of the air by gauze curtains ; to pass the inflowing air through an atmosphere of spray ; to artificially warm it in winter, and cool it in summer with ice : all this preparation of the air can be carried out in public buildings like the Houses of Parliament, but such arrangements are quite impossible in the case of the majority of private houses. As regards cottages, the mere hint at such a project is absurd in the extreme. An American architect has expressed the opinion-^ that a building cannot be supplied with cool air of a pleasant degree of humidity when the external air is hot and damp, for the cooling would be attended by the con- densation of the moisture and the formation of a mist. This change cannot, I admit, be produced without a preparation of the air in underground chambers adapted for the purpose, such as are available beneath public buildings or large houses. In the case of the majority of ^ "On tlie Relation of Moisture in Air to Health and Comfort,'-' by Eobert Briggs, C.E., in Quarterly Journal of Science, April 1S7S. THE AIR OF OUR HOUSES 285 houses, air, when hot aud moist, can be passed through a room with greater rapidity than usual, and the occupants will experience the cooling effects produced by the more frequent renewal of air. The establishment of a comfort- able uniform loss of heat by the body is the point to be arrived at in our efforts to determine the requisite speed for the passage of the air. Physicians are waiting for inventors to deal with this Eoie of difficult subject of providuig the habitations of the people, is to* excite poor as well as rich, with some efficient and simple *^^® demand ■*■ _ _ _ _ _ -^ tor efficient ventilating methods, remembering the above indispensable ventilating requisites. There is no difficulty as regards public a°,ce"^" buildings, such as churches, meeting halls, concert rooms, theatres, ball rooms, etc. They can all be ventilated and lighted in the same manner as the House of Commons. An exposure of the body, and especially of that part of it named the pulmonary surface, to sudden and extreme ranges of temperature, as in coming out into the cold air from a hot, ill-ventilated church or other public building, should be regarded as attended with a certain amount of risk to all, aud a positive danger to the aged and weakly. The role to be played by the Medical Officer of Health and other sanitarians in the public interest, is to urge Local Boards of Health to refuse to pass the plans of houses in which there is no efficient pro"\"ision for the removal of used-up air, as well as of other effete and noxious matters. When a great demand is in this way excited, a vigorous attempt will be made by those who devote their energies to the invention of contrivances for our health and comfort to supply that want. The standard of pure air for our dwellings and for all places of public resort, which we should endeavour to reach, may be considered to be thus constituted : — Active Oxyqcn, Ozone, and other ai?' purifiers, in recog- standard of pui'e air. nizable quantities. 286 THE DELETEPJOUS EFFECTS ON HEALTH OF Organic Matter, as Alhuminoicl Ammonia, as near '08 milligram, per cubic metre as possible. Carbonic Acid — Not more than "06 per cent. TcmperatiLre to be determined by the sensations of the majority as to comfort.-^ Moisture — Eelative humidity 70 to 75 per cent. A difference between the dry and wet bulbs of about 5 or 6 degrees. To approach this standard as closely as possible should be the aim of all who study the construction of healthy homes for the people. The practical question arises — How are we to make an attempt to arrive at any point on the road to this standard amongst the cottages of the poor ? The difficulties are enormous in many cases. In the rural districts, where the houses are surrounded generally by pure air we insist on every inmate (age not considered) having at least 200 cubic feet of air by night. In tramps' lodging- houses 300 cubic feet of air in a sleeping-room, and 400 cubic feet in a room used for sleeping and as a day room, are the minimum quantities sanctioned by the Local Government Board. In towns, where the air is more or less impure, a larger quantity of air per individual should be insisted on. We should gradually aim at obtaining not only the largest amount of breathing space that is practicable, but some efficient pro^asion for the change of air to the extent of from 2000 to 3000 cubic feet per hour, or about 10,000 gallons of air per head, per hour. ^ The temperature of comfort of air indoors has been variously stated : — 55° to 58° F. Hood's Treatise on Warming Buildings. 59° F. Peclet's TraiU de la Chaleur. 56° to 62° F. Tredgold's Princiiiles of Warming and Ventilation. 60° F. Dr. Richardson. 62° F. Box's Pra,ctieal Treatise on Heat. 65° F. Reed's Illustrations of the Theory and Practice of Ventilation. 48° to 60° F. Parkes' Manual of Hygiene. 59° F. Nurseries ; 66° F. Germrn Schools ; 61° to 64° F. Hospitals ; 66° to 68° F. Theatres and Assembly Halls. — Morin's Etudes sur la Ventilation. THE AIR OF OUE HOUSES 287 How is this to be accomplished ? HajDpilj, for the sake of ventilation, the majority of our cottages have an abundance of chinks and crevices that admit air from without. Fortunately, also, a considerable change of air is effected through the walls of our dwellings, if they are composed of brick, or mud, or tufacious limestone or wood. Professor Pettenkofer has, by experiments, shown ^ Pemeabii- that through a room made of brick walls, of the capacity of 2650 cubic feet, every crack and hole in which was thoroughly plugged up, 1060 cubic feet of fresh air passed per hour, by virtue of the difference of temperature (30° F.) between the outer (32° F.) and the inner (62° F.) air. He found that, with a difference of temperature of 9^° F. between the outside and the inside of a room, the spontaneous ventilation through each square yard of the free wall amounted to about 7 cubic feet, or 43 gallons per hour. Marker's and Schultze's experiments on the spontaneous ventilation of stables confirm these observations. They dis- covered that with a difference of temperature of 9^ F., the passage of air through each square yard of free wall was — ith walls of Sandstone . 4'7 cubic feet per j ,, „ Quarried Limestone 6-5 „ Brick ''J !) )) ,, „ Tufacious Limestone 10-1 „ Mud 14-4 All the ordinary building materials, such as plaster, wood, cement, etc., are more or less porous, and admit the passage of air through them in such a manner that we are not conscious of the movement. We are insensible to the passage of air if the velocity of the same is less than 19 inches per second. It will, perhaps, be considered by some that to change the air of a cottage at the rate of between 2000 to 3000 ^ The Air, in relation to Clothing, Dwelling, and Soil. 288 THE DELETERIOUS EFFECTS ON HEALTH OF cubic feet per hour per individual, at a velocity, to avoid draught, of less than 19 inches per second, is to supply an enormous and unnecessary amount of fresh air, and is, moreover, a thoroughly impracticable project. Our con- tinental neighbours do not consider this amount excessive, if we may judge from the following table, given by Petten- kofer and Morin, of their demands as to chano;e of air in their buildings per hour per person : — Hospitals for ordinary cases . 2120- -2470 cubic „ for wotinded . 3530 „ for epidemics 5300 Prisons .... 1766 "Workshops — ordinary . 2120 „ unhealthy 3530 Barracks — day 1060 night . 1410- -1765 Theatres .... 1410- ~ 53 J3 Large rooms for long meetings 2120 ,, for shorter ,, 1060 Scliools for adnlts 880- -1060 „ for children 424- - 530 „ Provided we keep our walls dry, for then we maintain them in a porous condition, as moisture renders them impermeable, so long we can draw a very large quantity of air through our walls, with but little difference of temperature between the inside and outside of the house. If this spontaneous ventilation is supplemented by some simple contrivance, such as a Tobin's tube, a Chowne's tube or Hinckes Bird arrangement, which cannot be interfered with, for admitting fresh air in so broken-up and divided a state as that its flow shall be unfelt by the occupants, all that can be done will have been accom- plished for the majority of our old isolated cottages in the country districts, the repairs of which often consume the whole of the yearly rental. Pettenkofer rightly says, " It is a waste of ventilation if it is directed against avoidable pollutions of the air . . . the proper domain of THE AIR OF OUE HOUSES 289 A'entilation begins when cleanliness lias done its best." We ought not, however, to let matters rest here as regards the rows of cottages in our towns and cities, which have but little free wall surface, and are often merely foul caves with no opening at the back to allow of the free passage of air. Thousands and thousands of these urban dwellings of the poor are caricatures of what cottage homes should be, namely, a healthful place for rest, re- freshment, and cheerful intercourse after toil, and would be more truthfully designated human piggeries. Who is there amongst medical men that is not familiar with the appalling infanticide that prevails amongst these districts which have been designated " Herodian," mainly due to the foul air (for young lives are the most sensitive tests of the existence of an infraction of sanitary laws), and partly, no doubt, to improper feeding and neglect. That noble appeal of Charles Dickens for legislation for the poor cannot but be remembered in thinking of this sad subject : " If those who rule the destinies of nations would but think how hard it is for the very poor to have engendered in their hearts that love of home from which all domestic virtues spring, when they live in dense and squalid masses, where social decency is lost, or rather never found, — if they would but turn aside from the wide thoroughfares, and great houses, and strive to im- prove the wretched dwellings in byeways, where only 230verty may walk — many low roofs would point more truly to the sky than the loftiest steeple that now rears proudly up from the midst of guilt and crime and horrible disease, to mock them by its contrast." What a picture was sketched of these dreadful places by Dr. Buchanan, when he was one of the travelling inspectors of the Local Government Board ! " In small closed courts, surrounded by high buildings, and approached by narrow and perhaps winding gangways, houses of the meanest sort stand, acre u 290 DELETERIOUS EFFECTS OF AIR after acre of them, witli but privies and dust bins to look upon. And surely such cannot be accounted fit for human habitation, while the standard of that humanity is low. Nothing short of a tornado can effectually ventilate these courts ; in still weather the atmosphere in them is un- changed and unchangeable. Can it be a matter of surprise that such regions should be the favourite pastures or hunting-grounds of filth diseases, and that moral as well as material deterioration should be invariable ac- companiments ? It may be truly said of many evil things, that ' like goes to like.' Happily the Artisans' Dwellings Bill, alias the Eookeries Bill, has been passed, which aims at the demolition of these nests of disease and crime ; and which will, it is to be hoped, gradually diminish the most depraved and unhealthy modes of life." PART II THE DETECTIOX AND ESTIMATION OF THE AMOUNT OF THE MOST IMPORTANT IMPUEITIES FOUND IN THE AIR T^YO methods of discovering the condition of the air, as to purity, a direct and an indirect one, have been in vogue : the direct vfhich is either (a) chemical, having for its object the detection and estimation of the quantity of impurities, such as the organic and other solid bodies, and the carbonic acid present in the air, or (h) biological, which is concerned in the estimation of the number of germs present in a known quantity of air ; and the indirect one being to ascertain its departure from a state of purity by the estimation of the amount of ozone and other purifying agents which have not been used up by the organic matter and by the various noxious gases with which the air is contaminated. DIRECT METHOD. CHAPTEE XXV MODES OF OBSEEVING SOLID BODIES IX THE AIE, AND OF SEPAEATIXG THEM FOE EXAMINATION Solid bodies As far back as 1830, Ehrenberg worked and published m the air. ^^ ^^^^^ subject. He showed the actual existence of an atmospheric kingdom of life, animal and vegetable. He was followed by M. Gaultier de Claubry, who passed air from various localities through water that had been exposed to a high temperature. During the cholera epidemic in England of 1849, the dust of air was much examined, in consequence of the supposed discovery of certain bodies termed cholera fungi in infected air. M. Quatrefages, Pouchet, Pasteur, N. Joly, and Charles Musset, Boussingault, Baudrimont, and Gigot, are foreigners who have all severally laboured at this subject from different points, the first five being especially interested in it in relation to the doctrine of spontaneous generation. Devergie examined the air in the vicinity of a case of hospital gangrene, and detected an enormous quantity of organic matter in it. Bits of wool, cotton, particles of hair, and epitheHal cells and starch, were most common. In the Army Medical Pieport for 1867, is an account of an experimental investigation made by Dr. F. de Chaumont into the ventilation of the new barracks at SOLID BODIES IN THE AIR 293 Chelsea. He passed 120 cubic feet of air tlirongli a freezing mixture, and 4*7 c. c. of fluid condensed from it contained epithelium in large amount, hair and various fibres, sand, soot, crystalline substances, and chloride of sodium, together with sporangia of fungi, and monads in considerable quantity. In the air of a back yard of a London Hospital he found considerable quantities of epithelium ; and in the " dirty linen area," where the foul linen was kept in crates until washed, pus globules and a quantity of fatty crystals apparently from dressings, bacteria both free and in the zoogiseal form. In the Accident Ward of St. Mary's Hospital, Paddington, he discovered pus cells in the air near some beds which had a bad reputation for erysipelas.-^ The Army Medical Eeport for 1868 contains similar observations by Dr. E. T. Wright on the air of the barrack-room, Eoyal Victoria Hospital, Netley. In 1861 MM. Eiselt and Bechi published the result of some experiments. In the same year an investigation was undertaken on behalf of the Lancet on the dust of town houses in dry weather. The result of this inquiry showed that it consisted of pulverized horse dung, and the grindings of shoe leather, and starch corpuscles. In 1862 Eeveil and Chalvet made some observations on the air of the surgical wards of the Hospital of St. Louis. Dr. Jefferies Wyinan and Dr. Salisbury were the earliest of American workers on atmospheric dust. Samuelson and Balbiani have also made experiments on. this subject. Dr. Salisbury's observations especially related to the air of the low marshy valleys of the Ohio and Mississippi in connection with the causation of intermittent and 1 "Three Reports on tlie Sanitary Condition of St. Mary's Hospital, 1875-76." 294 MODES OF OBSEKVING Professor Tyndall's experi- ments. remittent fevers ^ in wliicli he found palmelloid growths. M. Lemaire's researches, communicated to the French Academy in 1863, partly related to marsh air in the neighbourhood of Sologne, which was a highly malarious district. Selmi and Balestra have both made observa- tions on the air of swamps, and both describe the presence of myriads of spores of algge. The experiments of the latter were made on the air of the Pontine marshes. A great many examinations were made of the dust of the air during the cattle plague epidemic of 1866. It was collected in most cases by passing it through cotton wool. In 1867, M. Poulet reported that he found a number of bacteria in the condensed vapour of the breath in whooping cough. Tissandier found that atmospheric dust contains from 25 to 34 per cent of combustible, and from 66 to 75 per cent of incombustible matter. He passed a measured volume of air through distilled water which he evaporated, and then weighed the residue. In this manner, 1 c. c. of air yielded — In Paris Gramme. After heavy rain . •006 After 8 days of dry weather . •023 Under normal conditions •007 Under normal conditions •00025 After lengthened drouc;ht •003 In the country A rough-and-ready way of observing the dust of air is by admitting a ray of sunlight into a darkened room, when the " motes in the sunbeam," as the particles of dust have been popularly called, are visible to us. Professor Tyndall has employed the very powerful beam of the electric light for the purpose of rendering the dust of air more apparent, with which he associated the flame of a spirit lamp that created an appearance, when applied to the beam, of the ascent of dark wreaths of ^ American Journal of Medical Sciences, April 1866. SOLID BODIES IN THE AIR 295 intensely black smoke. A large hydrogen flame produced the same effect. The blackness proved to be due to the absence from the track of the beam of all matter capable of scattering its light, which had in fact been burnt. He said, in his lecture, delivered in the Eoyal Institution at the end of 1869 or commencement of 1870 : — " Nobody can without repugnance place his mouth at the illuminated focus of the electric beam, and inhale the dirt revealed there. Nor is the disgust abolished by the reflection, that, although we do not see the nastiness, we are churning it in our lungs every hour and minute of our lives. If, after inspiring a quantity of common air, a long expiration is made through a glass tube across the electric beam, the luminous track is at first uninterrupted. The breath impresses on the floating matter a transverse motion, but the dust from the lungs makes good the particles displaced. After a time, however, an obscure disc appears upon the beam, and at the end of expiration the beam is, as it were, pierced by an intensely black hole, in which no particles whatever can be discerned. The air in fact has lodged its dirt in the lungs. A handful of cotton wool placed over the nose and mouth during inspiration makes the dark hole in the beam of light appear from the beginning of expiration. A silk hand- kerchief ^ answers nearly as well." ^ The old-fashioned practice amongst the public, often witnessed by medical men, of holding a handkerchief to the mouth and nose on approaching the bedside of a person suffering from an infectious disease, may, in the light of recent investigations, have been a wise proceeding, and was doubtless intuitively arrived at and found by experience to be protective to the health. Sometimes scents were employed, not only in the handkerchief but in the sick-room [vide "Perfumes and Ozone," in Ozone and Antozone, pp. 121, 122). People very commonly apply a handkerchief also to the nose and mouth when they come into contact with a stench, to prevent the offensive odour from annoying them. The linen or cotton fabric no doubt acts as an imperfect filter, which strains off the solid particles floating in the air, with which that unjileasant odour is associated 296 MODES OF OBSEEVING Mr. C. Tichborne communicated to the British Association, in 1870, an account of his experiments on the air of Dublin. Street dust he said, was mainly composed of stable manure and triturated stones. The dust of New York has been examined by the New York Officers of Health by exposing glass plates to the air. The same substances were present in all of the specimens ; street dust, particles of sand and carbon, fibres of cotton, fragments of vegetable tissues, granules of starch, three different kinds of pollen grains, micro-organisms, and fungal elements. The latter were abundant, ranging in character from a micrococcus to mycelial filaments. When water was added to the specimens, bacteria and vibriones invariably made their appearance within a few hours. M. Miquel furnishes the following estimate of these micro-organisms, which, as will be seen, vary in number in the dust of different localities : — No. of Bacteria in 1 gramme of dust. Observatory of Montsouris near Paris . 750,000 Rue de Rennes, Paris . . . 1,300,000 Rue Monge, Paris .... 2,100,000 Mr. Blackley -^ has devoted his attention to that particular kind of air dust that produces hay fever, namely, the pollen of certain kinds of grasses.^ A good account of the great variety of particles of which atmospheric dust is composed is contained in Charles Eobin's TraiU du Microscope. The space at my disposal will not permit me to enter •^ Experimental Researches on the Causes and Nature of Catarrhus (Estivus, by C. H. Blackley, 1872. ^ He refers to one species, the pollen of which is so small that it would require 37 millions to make a grain ; whilst 6 millions are required of the Particles of pollen of the English meadow grasses. He considers that ■^760, or the 3427th part of a grain, is capable of producing the severest orni of hay fever. SOLID BODIES IN THE AIR 297 on that very large field as to the presence of those organic , substances in air which have in past times fallen in showers^ giving rise to the belief that blood and sulphur have descended from heaven. I must refer my readers to a little book, named Odd Showers, which is published by Kerby and Son, of Oxford Street, for much interesting information as to these records. The observations of Messrs. Tichborne, Blackley, and others, would lead one to think that the spores of fungi and other light bodies are to be detected in the air at very great heights, and that they are conveyed by aerial currents and storms from one part of the earth to another over vast tracts of country. The air dust, such as we breathe, may be conveniently collected, for either microscopical or chemical examination, in several ways : — 1. By means of Pouchet's aeroscope,-^ which consists Pouchefs of a glass tube hermetically closed at either extremity |jy^®^°®°°P®- a copper ferule. The upper ferule is fixed to the glass, and is connected with a tube of copper, terminating externally in a small funnel, and internally in the inside of the glass tube, in a very finely drawn point, not more than "5 m. m. in diameter. The other ferule is removable, and allows of the introduction of a circular glass plate into the interior of the instrument, which is placed at 1 m. m. from the point of the tube connected with the upper ferule. This plate is covered with adhesive matter ; and, if necessary, the point of the tube is made to terminate in a minute perforated diaphragm like the rose of a watering pot, so as to secure the disper- sion of the atmospheric particles over the surface of the plate. ^ Moyen de rassembler dans un espace infiniment petit tons les corpuscles normalement invisibles contenus dans uu volume d'air determine. — Comptes Ecndus, T. i. p. 748. 298 MODES OF OBSERVING Cunning- ham's apparatus. Dr. Mad- dox's Aero- scope Pump The apparatus employed by Dr. D. D. Cunningham,'^ in his numerous observations on atmospheric dust, consists of three thin brass tubes (A), two of which slip over the third central one, and come into contact with the opposite sides of a projecting rim on its circumference. This rim is formed by the margin of a diaphragm, which divides the centre tube into two chambers. It is of sufficient thickness to allow of a spindle passing up through it (B). Dr. Maddox's Aeroscope Pump ^ is an improvement on his aeroconiscope. It consists of two metallic chambers A and B screwed together, the chamber A being / Fig. 20. Aeroscope Pump. furnished with a perforated cone intended to project the dust of the air on a slip of glass covered with glycerine. This chamber is in direct communication with the chamber B, which contains an aspirator. The water passes drop by drop by the tube E into the tube D which is in- 1 Microscopic Examination of Air, by Dr. D. D. Cunningham, Surgeon, H. M. Indian Med. Service. Published by Government, 1874. 2 Journal Microscop. Socy., 2d series, vol. i. p. 338. SOLID BODIES IN THE AIR 299 clined at an angle of 45° with the axis of the instrument. The tube D is open at its upper end, and has a flute-like aperture laterally below the entrance of E. A litre of water is sufficient to pass 6 6 litres of air over the glass slip. The great objection to the three foregoing varieties of the same method is, that it is difficult to obtain glycerine perfectly free from foreign bodies. 2. A glass tube is heated to redness, and, when it has cooled, is surrounded by a freezing mixture. Air is then drawn by an aspirator through the tube. The great cold condenses the moisture of the air, and arrests its solid particles which is in both cases collected and exam- ined for nitrogenized compounds. 3. Dr. Watson employs fine glass threads soaked in glycerine or powdered glass, as traps for catching the solid substances which he afterwards washes with pure water. Perhaps the substance known as glass wool would prove a still more effectual air filter. 4. I use a mineral named asbestos, which is a fibrous and woolly substance, composed of a silicate and aluminate of magnesia and lime, for arresting the dust of the air. A U-shaped platinum tube about ^ inch in diameter, and 7 inches long, having been filled at the bend with this inorganic wool, and little caps of fine platinum gauze being inserted at each end of the asbestos to prevent the loss of any of its particles, a known volume of air is drawn through the tube by means of an aspirator. The tube loaded with asbestos is weighed in a delicate balance, both before and after the air is passed through it.^ The increase in weight, after the experiment, of course indicates the amount of solid particles contained in the quantity of air drawn through the tube by the aspirator. The plat- inum tube is then exposed to the flame of a Bunsen's burner, in which it soon becomes red hot. When all the volatile solid bodies, such as organic matter, nitrates, etc., 300 OBSERVING SOLID BODIES IN THE AIR have been burnt off, the tube ha^dng been again weighed is ready for a fresh experiment. 5. By taking the rain, which is the great air washer, and removing, by means of a pipette, the solid particles that subside in it after a few hours' rest. 6. M. Pasteur filtered a certain quantity of air through perfectly pure pyroxyline, which is soluble in a mixture of strong alcohol and ether. A tube containing a plug of tliis material was attached to a water aspirator, from the exit portion of which the amount of air drawn by the in- strument per minute, can be easily collected and measured. The cotton plug, on removal, was treated with its solvents, and the dust then allowed to subside. The complete removal of the pyroxyhne was effected by adding, and after a time remo^dng, fresh quantities of alcohol and ether. The dust is then transferred to the microscope slide for examination. 7. M. Marie-Davy of the Montsouris Observatory collected the dust of the air in a receiver which was con- nected with an aspirator such as is represented in Fig. 21. The receiver was composed of a bell glass, the roughened lower edge of the large opening of which rests on a piece of plate glass also rough- ened. The upper and small opening is closed by a cork, which is perforated by two glass tubes : one of them, marked c, is connected with the aspirator ; the other, h, terminates at one extremity in the air, and at the opposite, within ^P the bell glass, in a tapered point, a short dis- ^^°- ^■^" tance from a glass plate covered with glycerine or syrup. The arrangements carried out by ]\i. ]\iiquel in this Observatory for the collection of the schizomycetes, such as the micrococci, bacilli, bacteria, etc., are most elaborate and ingenious. The latest and most improved forms of apparatus will be referred to in the chapter on "The Biolooical Examination of Air." CHAPTEE XXVI MICEOSCOPICAL EXAMINATION OF THE DUST OF THE AIR The air contains sucli an immense variety of substances Dust de- in the form of dust, invisible to tlie naked eye, tliat their animai'^°"^ bare enumeration, without entering into any description vegetable, 11 -111 u/r- and mineial 01 tliem, would occupy a considerable space. Almute kingdoms, particles of anything and everything that exists on the earth, are liable to be mingled with the air that rests on it. Such minute organisms as micrococci, bacteria, and bacilli, are omnipresent except in the pure air of the highest mountains and far away at sea. As the air, in which we are always plunged, invariably contains more or less of these minute objects, our bodies ^ are naturally invaded by the same. These suspended matters are furnished by the animal, vegetable, and mineral kingdoms. Erom the animal kingdom is derived the debris of little creatures who have been born and have lived and died in the atmosphere, germs and small eggs. From the vegetable kingdom, spores of fungi, the pollen of plants and seeds of all kinds, particles of finely pulverized straw, minute fragments of rags, etc., are obtained. From the soil, dust of inorganic composition, such as sand, oxide of iron, lime, etc.; from volcanoes, sand and ^ M. Lemaire finds not only in the air that passes from the lungs, but also in the perspiratory fluid, abundant indications of animal and vegetable life. — CompUs Eendus, October 14, 1867. 302 MICEOSCOPICAL EXAMINATION OF mud, and small particles of carbon ; from the sea, chloride of sodium which is lifted by the spray and conveyed by the wind vast distances : — are contributed. It is in respect to the dust and impurities in the air, created by man and animals, and by vegetation, in which we are at present most interested, as they relate more especially to public health. Excluding, then, a considera- tion of the solid particles diffused through the air in manu- factories, and mines, to the injurious influence of which so many of our fellow-creatures are unhappily exposed, let us ask ourselves the question "Wliat appearances do the minute solid impurities contained in the air of our dwell- ings and public buildings, and of our streets, present under the microscope ?" Air dust has been divided into the light, which floats and is wafted about by currents, and the heavier particles that settle. The dust of our houses consists largely of light organic matter, either living or dead, whilst that of public buildings would appear to contain a larger proportion of the heavier kinds. Dr. Dust of the -pQYcj found that the dust on the walls of the British British "^ . Museum. Muscum cousistcd of 50 per cent of incombustible matter. The principal objects which we see in the dust of rooms and hospitals with high powers are little por- tions of (1) scaly epithelium (the dust of the skin), (2) particles of soot, (3) small round and oval cells, which, when multiplying, have an appearance like the number 8. These little bodies have been named " putrefaction cells," and by some microzymes, and have been described by Trautman, Lemaire, and Bechamp. Their growth is accele- rated by hydrogen sulphide and other vile-smelling gases, and is arrested by carbolic acid, which is one of our most valuable disinfectants. Lemaire found them in immense quantities in the air of dirty prison cells. They belong to that border land which is midway between the animal and vegetable kingdoms. We know not whether they are animals THE DUST OF THE AIR 303 or vegetables. They bear a strong reserablance to certain kinds of bacteria found in impure air and water. These organic impurities in air are favourite pastures for the growth and development of the animal poisons that pro- duce the zymotic diseases, such as typhoid fever, scarlet fever, etc. The poisons of these diseases rejoice and luxuriate iu filth of all kinds, especially in filthy air. The spores of tricophyton have been collected in the wards of hospitals devoted to skin diseases, and those of achorion schonleinii in wards containing cases of favus. The air of sick rooms and hospitals that are not ventilated efficiently, is loaded with organic impurities, which, in certain diseases, furnish different odours, — for example, a medical man usually recognizes the presence of small-pox or rheumatic fever in a house by their characteristic odours. The smell of a room occupied The organic by a person who is suffering from abscesses is almost ^p'^'?*'?, , , , furnished by distinctive of this class of malady. In smallpox wards different minute scales and dust of dried pustules, which, if intro- ^^^^^^'^^- ■ duced into the system of one unprotected by vaccination, would reproduce the disease, are found floating in the air. In hospitals devoted to skin diseases, that contain patients suffering from favus, ringworm, etc., which depend on the growth in the skin of little parasitic plants or fungi, the spores or seeds of these plants may be found suspended in the air. The air of the streets and gardens of our towns and cities contains soot, crystals of certain salts, starch granules, linen, cotton and wool fibres, bits of wood, and particles of food, the hairs of man and animals (dogs and cats). The character of the dust of the air that is found between the pure air of the country and the impure air of a large city has been well observed by M. Marie-Davy 304 MICEOSCOPICAL EXAMIXATIOX OF and liis associates at tlie Montsouris Observatory, in the neiglibourlioocl of Paris. Bodies collected on glycerine from December 30, 1875, to January 2, 1876, x 1000: — Fig. 22. 1 and 2, Pollen ; 3, Starcli ; 4, Three of these reddish black bodies were attracted by the magnet, and are gran- DESCRIPTIOX OF PLATE OF MICROSCOPIC OBJECTS FOUXD IN AIR. 1. Pollen. 2. Fungi. 3a. Starcli granules. 3b. starch granules polarized. 4. Protococcus pluvialis. 5. Epitlielium. 6. Vegetable spores. 7. Spores? 8. Fungi? 9. Particles of soot. 10. Crystals of chloride of sodium. 11. Crystals of chloride of ammonium ? 12. Crystals of sulphate of soda. 13. Mineral particles. 14. Desmids? SOLID E OD IE 3 IN AIR . Ic fdoe Mye 304- THE DUST OF THE AIR 305 ules of meteoric iron, which have been described by M. Tissandier. The fourth is a spore : it is uninfluenced by dilute sulphuric acid which dissolves starch granules. M. Pasteur suggests the institution of comparisons between the kind and quantity of organized corpuscles disseminated in the air at one place during the several seasons of the year before and after rain, etc., and at different places at the same time, with the object of increasing our knowledge of the zymotic diseases, especi- ally when epidemics are prevalent. He found in the winter months, during a period of very low temperature, ranging from 15*8° to 6'8°r., that a very small number of germs could be collected from the air. Of late years much attention has been devoted by Micro- Koch, Klein, Lister, Klebs, Sanderson, and a host of others, "'"^sa-msma. to those constituents of the dust of the air which have been denominated micro-organisms, and between one and two thousand publications have appeared in different languages on various branches of this subject. Into one comparatively so new, with a bibliography so imposing, and which is in a state of transition from month to month as new facts are elicited, it would be unprofitable in the interests of the health officer to plunge. It will be sufficient to give : (1) an idea of the appearance^ under the microscope of the more important of these bodies ; (2) some information as to the number present at different times in pure and impure air ; and (3) the reason for prosecuting researches into their life history and the conditions indispensable for the proof of the existence of a causative relation between some of them and certain communicable diseases. The most approved and recent classification of these ^ A good description of tliem is to be found in the Supplement of the Eleventh Annual Report of the Local Government Board for 18S1, from the pen of Dr. Victor Horsley. X 306 MICKOSCOPICAL EXAMINATION OF scliizomycetes or fission-fungi, named also microbes, microphytes, and micro-organisms, is that of Zopf ^ who arranges them in four groups. Group 1. CoccacejE — Genera. Micrococcus, Streptococcus (chain coccus), Sarcina (packet coccus) Merismopedia and Asco- coccus. Group 2. Bacteriace^ — Genera. Bacterium, Spirillum, Bacillus, Vibrio, Leuconostoc and Clostridium. Grou^J 3. LEPTOTRiCHEiE — Genera. Lej)totlirix, Beggiatoa, Crenothrix and Phragmidiotlirix. Group 4. Cladotriche^ — Genus. Cladothrix. The most interesting group is that entitled the Bacteri- aceje which contains the laro-est number of micro-orsfan- r/ 6 '•• e h \ \ I Fig. 23. a. Micrococci x 600. b. Streptococci x 600. c. Sareinffi (packet cocci) x 600. d. Bacterium tei-Dio. e. Bacterium termo, diagram of outline under higher power. /. Bacterium termo, x 4000 (Dallinger and Drysdale in Croolvsliank's Bacterio- logy) -with flagella. g. Bacillus anthracis with and without spores X 700. h. Yibrio serpens (after Cohn). i. Spirillum Obermeieri (of relapsing fever). fc. Comma-shaped bacilli 2 (after Crook- shank). I. Bacillus tuberculosis with spores x 700. ^ Dr. Crookshank's Bacteriology. - There are several varieties of comma-shaped bacilli, one kind being found in the mouth in connection with caries of the teeth and another in old cheese. The cholera comma-bacillus is stated to be distinguishable from other comma-shaped micro-organisms by its behaviour under culti- vation. THE DUST OF THE AIK 107 isms. Examples of the most important of its genera are here depicted. These micro-organisms multiply either by division or spore formation with marvellous rapidity. Cohn has pointed out that one bacterium placed in an organic medium suitable for its growth will in 24 hours have developed 16,777,216 bacteria and in three days 47 trillions, but, that as soon as they have exhausted the nourishment on which they live, they will soon cease to exist. Although spores are more resisting than the bacilli to extremes of cold and heat and chemical agents, it is reassuring to learn that patho- genic organisms are less resistant to perchloride of mercury (our chief microbe destroyer) than non-patho- genic ones. M. Miquel has found ^ that the number of bacteria varies much in the air at the different hours of the day, ■^ Averages in a cubic metre of air from observations during 6 years. Months. Park of Montsoui is. Rue de Rivoli, Paris. January- 225 1880 February . 155 2480 March 495 3710 April . 420 4905 May . 575 5750 June . 495 5535 July . 740 5205 August 6S5 4405 September . 605 4615 October 500 38-25 November . 335 2650 December . 225 2015 Annual Mean 455 3910 Seasons. Pt irk of Montsouris. Rue de Rivoli, Paris. Winter 290 .. . 2690 Spring 495 .. . 5395 Summer . 675 .. . 4705 Autumn 355 2830 308 MICEOSCOPICAL EXAMINATION OF months and seasons of the year, and in the air of different localities.^ He noticed at Montsouris, near Paris, two minima between 2 and 3 A.M. and between 2 and 3 p.m., and two maxima between 7 and 8 a.m. and between 7 and 8 p.m. They are present in the air in diminished numbers during those atmospheric states that accom- pany currents from the south and south-west, viz., low barometric pressure, an excess of moisture and purifying storms. Sea ail', Atlantic Ocean .... Air of high mountains .... ,, the saloons of ships Air at the summit of the Pantheon, Paris Air of the city of Berne ,, new houses in Paris ,, the sewers of Paris ,, the Laboratory of Montsouris ,, old Parisian houses ,, the new Hotel de Dieu, Paris ,, the Hopital de la Pitie No. of Bacteria per cub, metre. 6 60 200 580 4,500 6,000 7,420 36,000 40,000 79,000 Bacteria collected from 1 cubic metre of air. Rae de Rivoli 750 970 1,000 1,540 1,400 960 990 1,070 810 Although the number of bacteria in the air outside the hospital was nearly double as much in summer as in winter, the number in the wards was not more than half so numerous in the former as during the latter season, showing the influence of open windows and a fortiori the necessity of efficient ventilation without draughts iu the wards of an hospital at all seasons of the year. Hopital de la Piti6. A Ward Ward 1881. Miction Lisfranc (men) (women) March . 11,100 10,700 April . 10,000 10,200 May . 10,000 11,400 June 4,500 5,700 July . 5,800 7,000 August . 5,540 6,600 September 10,500 8,400 October 12,400 12,700 November 15,000 15,600 THE DUST OF THE AIR 309 Kocli of Berlin -^ and Klein of London are assiduous in the prosecution of researches having for their object the discovery as to whether a given micro-organism can be demonstrated to be the cause of a given disease in the bodies of man and animals. To obtain proof it is neces- sary to fulfil the following four conditions : (1) the micro- organism in question should be found in the blood or diseased tissues ; (2) successive cultivations of the micro- organism should be obtained in artificial media until its purity is undoubted ; (3) its reintroduction into the body of a healthy susceptible animal should result in the pro- duction of the same disease as that from which the original organism was primarily derived ; and (4) this same organ- ism should be found in the animal thus intentionally infected. As regards the diseases of man, each of these desiderata has been supplied in the case of anthrax, and accordingly ample proof has been afforded of the existence of an etiological relation between the bacillus anthracis and woolsorters' disease. 1 Die Milzbrand-impfung, 1883. CHAPTEE XXVII THE CHEMICAL EXAMINATION OF AIR The description of the modus ojijerancli in making sanitary estimates of the degree of impurity or purity of tlie air must necessarily be restricted to those bodies which are tlie principal and universally observed injurious agents, to the exclusion of others, such as sulphuric and hydro- chloric acids, arsenic, etc., that are the local and special products of certain manufacturing industries. Organic matter and carbonic acid stand prominently forward beyond all others as the bodies which require our attention : the former because it is, if in excess, the pabulum on wliich animal poisons feed, amongst which they increase, and through the medium of which they spread ; the latter because, whilst itself being noxious if in any large amount, it is nearly always in bad company. Dr. A. Carpenter, in his Lectures on Preventive Medicine and PvMic Hecdth, writes, " Wlierever you have excess of carbonic acid from the action of animal life, there you have also an excess of other debris, such as the organic matters which pass off from the respiratory organs ; septic matters given off from the pulmonary membrane, very manifest in some diseases to the sense of smell ; impure matters in the insensible perspiration ; ammoniacal com- pounds from retrocedent decompositions — all of which are the most injurious of such impurities." The presence of sulphurous acid from the combustion CHEMICAL EXAMINATION OF AIR 311 of coal in an overcrowded city, and free chlorine in the air of a manufacturing centre, may certainly tend to purify to some extent the atmosphere, which is so heavily laden with animal emanations. As the existence in air of an excess of organic matter keeps the oxygen, or its active form ozone, low — for it is always being used up in oxidizing it — so the presence of such intruders as sulphur or chlorine compounds, takes the place of this vitalizing gas. The purification of air by disinfectants after defile- ment reminds one of the purification by filtration of the water supply of a town that receives sewage — which is at the best an imperfect proceeding, and, moreover, a great waste of power. Far better and wiser is it to keep both these media pure, rather than, after permitting them to become impure, to then expend force (money) in endeavouring to restore them to a state of purity. Dr. Ballard and other eminent men have diligently collected information as to the fearful pollution of air that is unceasingly proceeding, and valuable materials have been accumulated by a Eoyal Commission, which, after devoting two years to its work, issued in 1878 its recommendations, in which were embodied suggestions for the extension of the Alkali Acts. Seven years have passed and matters are in statu quo as to air pollution, so that the future presents a gloomy outlook. The scientific chemist is at length in a position to represent on paper, in the form of figures, the differences in the degree of impurity of various kinds of polluted air. This first step towards the definite and precise having been gained, it then devolves on the health officer to clearly lay down, with exactitude, the connection that exists between these degrees of impurity and certain forms of disease or ill health. If the scientific chemist and Medical Officer of Health can push our knowledge so far as to be able to prove to demonstration that, if the human body is per- 312 CHEMICAL EXAMINATION OF AIE sistently exposed to air contaminated by a polluting agent to a degree represented by a certain figure, it will be, in tlie majority of instances, injuriously affected, then the Legislature will have some basis on which to work. A Government would, whether in accordance or not with its own wish, be compelled to act consistently with the principles of past sanitary legislation, the burden of which is that a man shall do nothing which is injurious to the health of his neighbour or to the public welfare. But the obstacles to advancement are twofold : first, an indis- position exists to place further restrictions on trade which is abeady depressed ; and, secondly, the legal mind seems quite unable to assimilate the fact that anything obnoxious is " a nuisance injurious to health " unless it creates a definite disease. Mr. Simon has tersely adverted to the point thus : — " To be free from bodily discomfort is a condition of health. If a man gets up with a headache, pro tcmto he is not in good health ; if a man gets up unable to eat his breakfast, p-o tanto he is not in good health. When a man is li\dng in an atmosphere which keeps him constantly below par, as many of these trade nuisances do, all that is an injury to health, though not a production of what at present could be called a definite disease." Those who govern cannot avoid deploring, as do the governed, that great manufactories that defile the air exist, which sustain in their vicinity hundreds and thousands of work-people, whose vital energies are lowered (thus rendering them a more ready prey to disease), and whose offspring are stunted and depraved by the medium which the industry that supports them is always and needlessly rendering unwholesome. A. Organic Matter. Organic matter which is given off from the skins and lungs of aU animals, and gives that peculiar, indescribable CHEMICAL EXAMINATION OF AIR 313 odour noticeable in ill-ventilated bedrooms occupied by many or by dirty people, is very easily detected in the air, but there has always been a considerable difficulty in estimating its amount, by reason of the interference of other substances contained in air, which is a mixture of so many different extraneous bodies. Of the chemical composition of organic emanations we know very little. Dr. Odling found that the vapours arising from sewage were of a carbo-ammoniacal nature, similar to such bodies as methylamine, or trimethylamine and ethylamine. Beyond this point there is nothing but a terra incognita as to this very interesting subject. One of the first processes adopted for the estimation Permangan- n ,-1 j_ o •jj_ j_ ^ !_• ate of Potash 01 the amount oi organic matter was to expose a solution j^g^-j^o^j^ of ]3ermanganate of potash to the air, as the oyxgen of the salt has a powerful oxidizing effect on organic matters. A burette was filled with a very weak solution, and an attempt was then made to ascertain how much of it was necessary to drop into a bottle of a certain capacity, before it arrived at the point when it was no longer ^gcolorized by the air of the bottle. The amount necessary to reach this point having been found, it was a matter of easy calculation to ascertain how much of the permanganate of potash salt was expended. Another plan was the following : — The test solution is placed in a bottle of known size, attached to an aspirator, and is violently shaken with the air in the bottle. This air having been washed, the bottle is re- filled by the aspirator, and a fresh quantity of air is washed, etc., the object being to discover how much of any given sample of air is necessary to c/^ccolorize the pink solution. It will be seen that in both modes of applying this permanganate of potash test the aim is the same, namely, to remove the pink colour of a solution of known strength by a known quantity of air shaken with 314 CHEMICAL EXAMINATION OF AIR it. It was ascertained, however, that the nitrous acid often present in the purest air ; that the sulphurous acid, which is very abundant, and the hydrogen sulphide gas, which is generally found in minute quantities, in town air ; and the chlorine compounds, which often exist in the air of our manufacturing cities : — also decolourize permanganate of potash. This process, therefore, never unquestionably proves the presence of any organic matter, but merely indicates the relative quantities of oxidizable matter contained in different samples of air. Better modes have since been de\T.sed, having for their object the conversion of the organic matter of air into ammonia, the amount of which can easily be calculated. Water is prepared of great purity by distilling it twice in perfectly clean ves- sels. A definite quantity, generally 50 c. c, is placed in a Winchester quart bottle, or any other of known capa- city. A little bellows,^ the capacity of which is ascer- tained, with a vulcanized indiarubber tube, is em- ployed for pumping fresh supplies of air into the tube attached. It possesses a valve at bottlc, Or for withdrawing one extremity, which admits air when ^-}^q ^ir Contained in the air is xjumped into a vessel. If it is j.i j_ r i wished to withdraw air from a vessel bottic, SO that irCSh air may this aperture is closed by a large cork, ^.^^gj^ -^^ and take itS pkcC B. A Winchester quart bottle. ■*- (fig. 24). The bottle and bellows are taken to the place, the air of which it is proposed to analyze, and the washing of ^ Mine was procured at a surgical instrument maker's, sucli as is em- ployed for inflating air-beds. Fig. 24. A. Small hand - bellows, with indiarubber CHEMICAL EXAMINATION OF AIR 315 the air is proceeded witli by blowing air thrice into, or sucking air three times out of, the bottle, replacing the stopper, and violently shaking the bottle. Tliis perform- ance has to be repeated 100 times, and is, as may be supposed, sufficiently laborious. In order to refill the bottle with air, an air-pump is sometimes used until the required point is obtained on a mercury gauge, this being found to indicate a known amount of air, which is then allowed to enter in order that it may be washed. Some few, such as Dr. Angus Smith, have gone through a series of these air-washings, and the results arrived at ha^'e been found satisfactory. The cumbrousness of the apparatus, and the labour involved, have been great obstacles to the general adoption of this process. Mr. A. Moss' experiments on the nitrogenous organic matter in air, referred to on page 237, were made by passing a certam quantity of air, by means of " an accurately graduated aspirator," through four wash bottles, each being of a capacity of 100 c. c, and each containing 50 c. c. of pure distilled water. In the first bottle of the series, 50 c. c. of pure hydrochloric acid were also poured. The air-washings are distilled with the caustic potash and permanganate of potash solution, and the distillates are treated with iSJ"essler reagent. Although all the or- ganic nitrogen of the air is not in this manner converted into ammonia, that which is most easily decomposed, such as is theoretically capable of producing disease, is secured. A fourth method, which has been suggested as appli- cable to the detection and estimation of atmospheric impurities, is to pass a known quantity of air by means of a swivel aspirator, graduated into cubic centimetres or cubic inches, through distilled water to catch the organic matter, and through standard solutions of nitrate of sil\^er and chloride of barium, to retain respectively the chlorine 316 CHEMICAL EXAMINATION OF AIR and sulphur compounds. This plan is perfectly useless, for the amounts of these bodies secured in this way are too small for estimation. If success is to be achieved in air analysis, it is absolutely essential that a very large quantity of air be washed in a very small quantity of water, so large indeed as to be able to obtain results which are altogether beyond the reach of being affected by the experimental errors that are inseparable from all delicate analytical operations. A fifth method, already mentioned as adopted for extracting the solid particles contained in air for micro- scopical examination, consists in drawing a measured quantity of air by means of an aspirator through a clean curved tube (which has been previously heated and cooled), surrounded by a freezing mixture. The moisture contained in the air is condensed, and with it much of the organic matter. The tube is then washed out with pure water and the washings are analyzed. The elaborate series of analytical observations on the impurity of air that have been in progress for some years at the Montsouris Observatory, near Paris, under the superintendence of M. Marie -Davy, and the valuable analytical work on the air of Glasgow, that was for a short period carried out by Mr. Dixon, B.Sc, and Mr. Wm. Dunnachie, with the co-operation of the Medical Officer of Health, are the most complete and perfect that have yet been attempted on a large scale. The arrangements of the latter gentlemen are in many respects precisely the same as those conducted by M. Marie -Da^y, with some improvements that they have, through the light of English methods of analysis, made. The apparatus which is used at the Montsouris Observatory, not only for the estimation of the amount of organic matter, but of that of carbonic acid, ozone, etc., consists essentially of two distinct parts, one being a CHEMICAL EXAMIXATIOX OF AIE 317 pump or aspirator, of a peculiar construction, which draws a known quantity of the air operated upon through a certain solution, and the other being an arrangement for holding the absorbing solution and exposing it fully to the in- fluence of the air. The aspirator is composed of a glass tube, about 2 centimetres in diameter, and 10 centimetres long. This tube is tapered at its lower extremity, which is connected with a vertical india- rubber or glass tube B, about 5 millimetres in diameter and 2 or 3 metres in length. The glass tube A is closed at its upper extremity by a cork, tlirough which two tubes D and C pass. The tube D com- municates with a water ser^-ice pipe ; a stopcock at the junction serves to regulate the flow of liquid which, running into A, descends through the ringed portion (h) of the tube B, carry- ing bubbles of air derived from the tube C, similar in appear- ance to the manner in which the mercury of a Sprengel's pump draws the au- (fig. 25). The water and air both enter the displacement gauge E, where they separate. The water flows away by the curved spout F, and the air escapes by the tube G, which terminates in an air meter that measures its volume. The " aspiration pipe," C, is attached to the set of Fig. 25. 318 CHEMICAL EXAMINATION OF AIR absorbents intended to remove the body to be collected from the air. Where, in other analytical experiments, a larger quantity of air is required, the observers at Montsouris combine together 8 of these twisted tubes, arranging them in a parallel manner {vide fig. 28). This more powerful aspirator delivers 80 litres of water and 200 litres of air per hour. A set of absorbers consists of two or more elements, each element being thus formed : A straight tube of platinum, 1 centimetre in diameter, and 14 or 15 centimetres in length, open at its upper end, is dilated at its lower extremity, where it is closed by an arrangement resembling the rose of a watering can, pierced in its centre by 5 or 6 holes of J millimetre in diameter, to facihtate the washing of the tube. At the upper part of the rose the enlarged portion of the tube is perforated with 2 holes of f of a millimetre in diameter, disposed in two circular rows. This tube is arranged in the axis of a deep cylindrical glass, about 4 centimetres in diameter, and 11 or 12 centimetres in depth, named a " barboteur." Here it is retained in position by a gutta-percha cork, which is also traversed by a bent glass tube of a diameter of 1 centimetre. If we place some water in the glass and draw air through the bent tube, air wdll enter the platinum, tube and escape through the liquid in the form of numerous fine bubbles {vide fig. 27). Wlien the amount of organic matter in the air is sought to be determined, M. Marie- Davy and his assistants pass 100 cubic metres = about 3531^ cubic feet of air, through distilled water, and examine it by the permanganate process. In Glasgow, which is well known to be a city of smoke and manvifactories, 6 or 7 stations were established in its various parts, and one was organized in pure air at Eaglesham, which is 1 2 miles distant ; at all of which the amount of ammonia and albuminoid ammonia, carbonic CHEMICAL EXAMINATION OF AIR 19 Fig. 26. acid, sulphuric acid, and chlorine, coupled with certain meteorological phenomena, such as rainfall, temperature, etc., were observed. Every station in the city was provided with (1) sets of "absorbers," each "set" or " series " being furnished with a distinct solu- tion containing glass beads, adapted to withdraw one of the above named substances from the current of air that passes through it; (2) a water injection aspirator (vide fig. 26); (3) a gas meter to measure the amount of air passing through the aspirator ; and (4) a water- gauge to keep the aspirators at all the stations as nearly as possible at one and the same speed. A set of absorbers for free ammonia and albuminoid ammonia {i.e. the ammonia which we obtain by decom- posing nitrogenous matter), which were estimated together as nitrogen, was thus prepared. The glasses hav- ing been thoroughly washed, about three ounces of glass beads {vicle fig. 27) and some twice distilled water were placed in each. They were allowed to remain in the water for a short time in order that any impuri- ties adhering to the beads might be removed by the water. The distilled water having been poured off, 1 c. c, of diluted sulphuric acid, and 70 c. c. of distilled water, free from monia, were introduced in the fol lowing proportions : — Dilute Sulphuric Acid. Distilled Water. Glass. 5 c. c. . . 30 c. c. in No. 1 3 c. c. . . 30 c. c. „ „ 2 2 c. c. . . 10 c. c. „ „ 3 (r^ A set of Absorbers Fig. 27. A Set of Absorbees. a a a. Tubes with roses at am- their extremities. 6 6 6. Absorbing solutions, c c. Indiarubber tube con- nections. 320 CHEMICAL EXAMINATION OF AIR The roses being inserted, the set of absorbers was attached to an aspirator for 48 hours, in which space of time about 200 cubic feet of air had passed through this dilute sulphuric acid. At the end of this time the contents of the glasses, beads included, were poured into a copper flask made out of a very large ball-cock, into which 15 c. c. of a solution of carbonate of potash (240 grammes in a litre of distilled water) had been previously poured. The washings with twice distilled water of the glasses and tubes were added, so as altogether to just exceed ^ htre. The copper flask was then attached to a condenser, and distillation was performed exactly as has been described on pages 40 to 48, in the analysis of water, the first ^ litre yielding the ammonia, and the remaining -} litre, after the addition of 50 c. c. of the caustic potash and permanganate of potash solution, furnishing the albuminoid ammonia ; the amount in each case being estimated by a standard ammonia solution precisely as has been there indicated. I am not aware that beads are employed at the Montsouris Obser- vatory for minutely subdividing the streams of air. This addition has been made, I believe, by Mr. Dixon (vide fig. 27). And to it is partly, in all probability, to be ascribed the higlier results which he obtains. At the station at Eagiesham he used an aspirator formed of a combina- tion of twisted tubes, the internal orifice of each having a slit {vide fig. 28). There are a great variety of as- pirators, and it is difdcult to decide as to which is the best form. Some are more adapted for certain purposes than for others. Descriptions and Fig. 28. CHEMICAL EXAMINATION OF AIR 121 sketches of many of the favourite kinds are to be found in Ozone and Antozone, pp. 250-259. The improvements effected by Mr, Dunnachie on the retirement of Mr. Dixon consisted in employing more " absorbers " in each " series," in substituting glass retorts for the copper flasks, and in abolishing the error attendant on the changes in the water pressure by adapting Borradaile's governors for street lamps to the meters. There would seem to be some divergence in the results as derived by the bellows pump and shaking (described on page 314) when compared with those procured by aspiration with rose-ended tubes.""- *> By Shaking. Aspiration, 3 bottles. Milligramme in 1 Cubic Metre of Air. Free Ammonia. Alb. Ammonia. Free Ammonia. Alb. Ammonia. Manchester, Dec. 2, 1876, dull, clamp morning . Ditto, Dec. 4, raining . •093 •160 •159 •070 •053 •124 Prof. Ira Eemsen has adopted" as a collector of the Prof, organic matter of air a modification of Chapman's ^^™®J^"^^ arrangement of a funnel filled with pumice stone. A tube of |-th inch internal diameter and from 5 to 7 inches long is drawn out at the lower end, so as to accommodate a small piece of rubber tubing. Having been carefully washed it is filled with ignited ]Dumice stone. A piece of platinum gauze having first been dropped into the tube, a layer of coarsely powdered pumice stone is introduced, and finally a layer of the finely powdered material is placed on the coarse layer. 10 litres of the air to be examined are drawn through this tube of pumice stone by an 1 Proc. of Rotjal Society, December 13, 1877. 2 " Organic matter in the Air," in National Board of Health Bulletin, January 31, 1880. 322 CHEMICAL EXAMINATION OF AIR Mr. A. H. Smee's Metliod. Pulveriza- tion of water Method. aspirator. The organic matter obtained is examined by the Wanklyn^ Chapman, and Smith process, and its amount is determined by means of the Nessler reagent. No ammonia is obtainable from absorbents placed be- tween the pumice stone tube and the aspirator. The pumice stone requires to be freshly ignited after each experiment. The organic matter has been obtained for examination from air, by collecting the moisture that is seen to attach itself to the walls and windows of crowded, ill- ventilated halls, which has been condensed by the cold air outside. Mr. A. H. Smee ^ employs a glass funnel drawn to a point, and filled with fragments of ice. The aqueous vapour in the air is deposited as a dew on the sides of the funnel, which runs down and is received in a vessel underneath. This air moisture, in whatever way procured, is examined for nitrogenous com- pounds. The process, which will now be described, is preferred by me to all that have yet been adverted to : — 1. Because it is the most rapid and reliable one that has been devised. 2. Because the air- washing apparatus required is portable, and can be readily carried in the hand by any one in a small box. It consists in bringing continually fresh quantities of air into intimate contact with a small quantity of very pure water, which is reduced to a minute state of sub- division by pulverization. The tools required are the following : — Fig. 29. ^ Soc. Science Transccctions, 1875, p. 486. CHEMICAL EXAMINATION OF AIR ?. 9 ?. 1. A glass cylinder about 7-^ or 8 inclies long and 2 inches in diameter, furnished with a large black india- rubber stopper, perforated with two holes, into one of which the air -pipe of a Bergson'e spray producer is fitted, the other being intended for the passage of a straight glass tube about 12 inches long and ^ inch in diameter. Fig. 30. A. Cylinder. E. Black indiarubher cork, thron^li , B B. Wash-bottles. which jiasses the air-pipe of a Bergson's 0. Black indiarubber ball pump. spray producer and a straight glass tube, D. Black indiarubber J oz. ball, to which one eud of which stoppers into a wash- a glass tube, tapered to a fine point, is bottle, attached. P. Level of fluid in cylinder. 2. Two stoppered Woulff' s wash-bottles, of a capacity of about 130 c. c. No corks should be employed for connections. The tubes are stoppered into the necks of the wash- bottles. 3. A stoppered flask, of the capacity of 100 c. c, with a mark at about 70 c. c. 4. A black -1- oz. indiarubber ball, to which a glass tube, drawn to a fine point at its extremity, is fitted. 324 CHEMICAL EXAMINATION OF AIR The point is protected bj a cap formed of an inch of the smallest black indiarubber tubing, sealed at one end. The steps of the process are as follows : — The several .parts of the apparatus having been thoroughly cleansed in the laboratory with twice-distilled water, which gives no colour whatever with ISTessler test, by the aid of the ball injection tube, the several parts are securely attached to one another. The cylinder with its spray producer, the wash-bottles, the ball pump, and flask filled up to the 70 c. c. mark with twice-distilled water, are packed in a small practically air-tight box, and conveyed to the place, be it a public building or a private dwelling-house, or some marsh land, where it is intended to make an air-washing. Pour a little of the 70 c. c. of the distilled water contained in the flask into the glass cylinder, so that when inverted its level may be just below the jets of the spray tubes. The remainder of the 70 c. c. is poured in about equal proportions into the two wash-bottles. Air should then be pumped into the glass cylinder so as to produce in its interior a fine spray or mist by means of the indiarubber pump, the capacity of which should have been previously ascertained by the help of an air or gas meter. The gTeater part of the spray returns to the water at the bottom of the cylinder to be reconverted into spray with fresh portions of air, but a small quantity passes downwards through the straight tube into the wash- bottle to which it is attached, and a still smaller portion reaches the other wash-bottle. At the exit tube of the latter no spray can be perceived. The indiarubber pump which I employ delivers 3 '2 cubic inches of air every time its sides are approximated by the pressure of the hand, so that if it is emptied 540 times, an operation which altogether consumes about a quarter of an hour, 1 cubic foot of air is injected into the glass cylinder. At the termina- CHEMICAL EXAMIXATIOX OF AIK 325 tion of the stage of air-wasliing, the distilled water in the cylinder and in the wash-bottles should be immediately poured back into the flask, and the apparatus having been restored to the box is returned to the laboratory ; where the interior of the cylinder, and wash-bottles, and glass tubes, should be at once washed out, by the aid of the ball injection tube, with twice distilled water. The great point to be aimed at is to wash the several parts of the apparatus most thoroughly with as little distilled water as possible, as if indeed this fluid was most costly. The washing of the apparatus can efficiently be accomplished with 30 c. c, which should be poured also into the flask, thus filling it up to its 100 c. c. mark. The mere washing of the apparatus with distilled water both before and after the operation is sufficient to heighten the experimental error, which is inseparable from all these delicate experiments. Accordingly, it is necessary to know the average amount of nitrogen, whether in the form of free ammonia or albuminoid ammonia {i.e. the ammonia which we obtain by decomposing nitrogenous matters), which is present in the air in which these cleansings are made. If we know the average experi- mental error which occurs when blank experiments are made in our laboratory, there is nothing easier than to make the necessary deduction from the results furnished by an au'-washing. The average experimental error of manipulation when the preliminary and terminal cleansings of the apparatus are made in my laboratory is about '006 of albuminoid ammonia for a cubic foot of air, a Cjuantity which is consequently always deducted by me from any result obtained from an air analysis. The contents of the flask, namely, the air- washings and the cleansings of the cylinder and wash-bottles, are analyzed for ammonia and albuminoid ammonia in a manner pre- cisely similar to the mode adopted in a water analysis. 326 CHEMICAL EXAMINATION OF AIR A small stoppered retort, of a capacity of 200 c. c. connected with a glass Liebig's condenser, about 18 inches long, is necessary. By means of a little copper basin, containing sand or oil, placed on a large ring of a retort stand, heat can be applied more gently than with a naked flame. I often, however, use the naked flame with the chimney, as figured on page 115. The retort, condenser, etc., should, after copious ablutions with tap water, be first thoroughly washed internally by distilling through the apparatus some twice-distilled water. The 100 c. c. of air- washings contained in the flask should then be introduced into the retort, and distillation begun. A dozen test glasses that will stand without support, about 4 inches long, and 4th inch in diameter, the bases of Fig. 31. which have no colour, should have been previously marked with a file at the height which is reached by 10 c. c. of fluid. 'No corks should be used. The retort and con- denser can be united by a packing made of a strip of common writing-paper. The first distillate of 10 c. c. that passes over should be Nesslerized by introducing into it -J- c. c. of Nessler reagent, and shaking the mixture. We should not blow into the pipette so as to mingle the contents of the ISTessler glass, as is not uncommon in water analysis. The second, third, and fourth distillates. CHEMICAL EXAMINATION OF AIR 327 each of 10 c. c, may be thrown away, and a thhd of the quantity of ammonia found in the first distillate be added as in water analysis, page 42. The contents of the retort are then to be allowed to cool. After it has become reduced to a state of tepidity, 10 c. c. of the solution of permanganate of potash and caustic potash are added, and the distillation again proceeded with. Each of the three distillates should be tested with ^ c. c. of Nessler reagent, and then the estimation of the coloration of the single ammonia distillate, and the three albuminoid ammonia distillates, should be made. A burette with the subdivisions of each cubic cen- timetre widely apart is necessary. Mine is 1 foot long and xoth inch in diameter, and with it y^ths of a c. c. can easily be read. The very dilute standard ammonia solution used is half the strength of that found most convenient in water analysis, and is prepared by mixing 5 c c. of the strong standard solution of ammonia (1 milligramme of ammonia in 1 c. c.) with 995 c. c. of twice-distilled water. Accordingly 1 c. c. of it contains "005 milligramme of ammonia. ic. c. „ -0025 ., „ „ ; j\c. c. „ -0015 xVc-c. „ -0005 It is necessary to make up standards exactly as in water analysis. The test glasses should be cleansed with twice-distilled water by the aid of the pipette before they are employed. If Gmelin's wash-bottle is used, organic impurities from the breath may be introduced. The test glasses containing the standards and the distillates, the colour of which it is necessary to imitate, are placed on a sheet of white paper. It is often very convenient to stand them in a common test tube rack. The differences between the tints of each -J^th of a c. c. .S28 CHEMICAL EXAI^IIXATION OF AIR of the very dilute standard ammonia solution are dis- tinguished with great precision by one who has had some practice with these delicate analytical operations. The great objection to the employment of so small a quantity of air as 1 cubic foot is, that the experimental error falls so heavily on the results. This difficulty can be overcome by practice and the gTcatest attention to cleanli- ness, and the minute details with which every practical scientific chemist is conversant. Blank experiments on pure air, or on the twice-distilled water with which the apparatus is washed, will give confidence to the operator in his tools, and by affording liun practice will help him to obtain reliable results from air of different degrees of impurity. Whichever of the foregoing plans be adopted for extracting the organic matter from the air, its washings are treated in the same way. These washings are examined by the AYanklyn, Chapman, and Smith process, in a manner precisely similar to the mode in which the organic matter contained in water is detected and estimated, which has already been described {vide page 39). B. Carljonic Acid. Carbonic As I bcforc statcd, carbouic acid is not the worst impurity in the air of our houses, for it stands second to the organic matter in its evil effects, yet an estimation of its amount is an index of the foulness of air of a very valuable kind. There are several modes of detecting its presence and calculating its amount in any given sample of air. Petten- The method known as Pettenkofer's is a good one, Method. hut requires the expenditure of much time and labour. It consists essentially in washing a certain measured quantity of air with a definite quantity of hme water or CHEMICAL EXAMINATION OF AIR 329 baryta water, and noting the loss of causticity that either of these waters has undergone ; in other words, the amount of hme or baryta that has united with tlie carbonic acid. The causticity of tlie lime water to be used in the experiment is first ascertained by mixing with a certain measured quantity of it a known amount of a solution of oxalic acid to neutralize it. The oxalic acid solution is made of such a strength, 2*25 grammes in 1 litre of water, that 1 c. c. will exactly neutralize 1 milligramme of hme. Turmeric paper is employed for noting the exact point of neutralization. The same quantity of lime water is placed in the bottle of air to be examined, is shaken with it, and is allowed to remain in it for not less than six or eight hours, at the end of which time the causticity of the lime water is again determined by means of the oxalic acid solution. The difference will furnish us with the amount of lime that has become imited with carbonic acid in the measured amount of air under examination. From this datum the pei]centage of carbonic acid is easily calculated. Correc- tions have to be made for temperature and barometric pressure. This process is fully described in Parkes' Hygiene (fifth edition). The determinations of the amount of carbonic acid in The the air are thus made at the Montsouris Observatory, observatory A set of absorbers, consisting of four elements or^^^tiiod. " barboteurs," each of course furnished with its platinum rose, is charged with a 20 per cent solution of potash, coloured blue with a few drops of litmus. The elements are connected with one another, all being in communication with the aspirator depicted in Eig. 25. The last element serves to show if all the carbonic acid has been extracted by the preceding ones. After the passage of 100 cubic metres of air the contents of each element is submitted to analysis. The platinum tube 330 CHEMICAL EXAMINATION OF AIR throngli which the air has entered is attached to a graduated burette containing hydrochloric acid. The glass tube through which the air has passed out is con- nected with a cylindrical displacement receiver full of water, covered with a layer of petroleum oil, to prevent the water from dissolving the gas, and furnished with an A. Graduated 'burette. B. An element or "barboteur. C. Indiarubber tube. D. Displacement vessel. E. Bent tube. F. Measure. exit tube. This exit tube E may be inclined on one side in such a manner that its upper end shall be on a level with the liquid in T>. A defiuite quantity of hydrochloric acid is allowed to flow into the solution of potash, sufficient, indeed, to convert the blue colour of the litmus to a red tint. The carbonic acid evolved displaces CHEMICAL EXAMINATION OF AIR 331 a volume of the water equal to itself. This water is received into a burette graduated into cubic centimetres. The method pursued at Glasgow by Mr. Dixon, con- sisted of the i^assage of 1 cubic foot of air per hour, for 48 hours, through solutions of caustic potash (320 grammes per litre) contained in three wash-bottles (a set of absorbers). On their removal to the laboratory, the carbonic acid was precipitated as carbonate of baryta, which was allowed to subside in well-stoppered bottles, and the amount of carbonic acid was estimated by the sp. gr. process. Dr. A. Smith has found ^ that three washing-bottles containing a solution of barium hydrate, were insufficient to absorb all of the carbonic acid from the air aspirated through them. Volumes, COo per million volumes ; of air. Exp. 5. Exp. 6. 1st bottle gave 80 115 2d 62 71 3cl 62 66 4th 53 62 5 th 18 62 6 th 45 62 Total . 320 438 in series of 6 bottles. Another good method, proposed by Wanklyn, based wankiyn-s on the same principle, is to make a standard by dis- solving 4'74 grammes of dried carbonate of soda in 1 litre of water — a solution which contains a cubic centimetre of carbonic acid (=rl-97 milligrammes of carbonic acid) in every cub. cent, of liquid. A bottle capable of holding 2000 cubic centimetres of air, or, failing one of exactly the right capacity, a stoppered Winchester quart bottle, having been washed clean, is rinsed with distilled water and allowed to drain. It is filled with the air to be tested by sucking 1 Proc. of Royal Society , December 13, 1877. 332 CHEMICAL EXAMINATION OF AIR out the air of the bottle with a glass tube, or with a bellows, like that in Fig. 24, when air from without immediately takes its place. 100 c. c. of baryta water are introduced, and the bottle is shaken for two or three minutes. The baryta water, on being poured out into a glass cylinder, is found to be more or less turbid, being slightly so if the air is good, and like milk if it is very impure. We then proceed to imitate the degree of turbidity in the following manner:- — The standard soda solu- tion is measured by drawing out the number of cub. cents, required from a burette graduated to deliver tenths of a cubic cent, of solution. We take 100 c. c. of baryta water and introduce into it 1 c. c. of soda solution. If the turbidity thus occasioned is about equal to the turbidity produced in the 100 c. c. of baryta water by the air under examination, we know that the air contains •05 vol. of carbonic acid per cent. If 2 c. c, or more than 2, are required to imitate the turbidity occasioned by the air, the air is bad and ventilation is defective. Dr. Notter advocates the trial of the delicate process of Capt. Abney, which is described in the Sanitary Record, September 9, 1876 : — To a Florence flask of known capacity is adapted a U-tube half filled with coloured spirit and to which is fitted a scale of half an inch. A small glass bulb is filled with a saturated solution of caustic potash and sealed by the flame of a gas jet. The bulb is broken by violently shaking the flask, and the caustic potash set free combines with the carbonic acid contained in the air of the flask. The production of a partial vacuum depresses the spirit in one of the limbs of the U-tube, the amount of which being measured furnishes the datum from which a cal- culation is made of the quantity of carbonic acid in the flask. Simpler, but somewhat less accurate, modes, called CHEMICAL EXAMINATION OF AIR the household and minimetric processes, which are sufficiently exact for all practical purposes, have been proposed by Dr. Angus Sniith.^ The outside air contains an amount of carbonic acid, H'^usehoid varying between "03 and "06 per cent, but is most frequently '04 per cent, which rises in crowded buildings and other close, ill -ventilated places to -25 per cent. Method. Fig. 33. The way to estimate the amount roughly is to wash different measured quantities of air with ^ oz. of lime water in such bottles as are here depicted. The lime water is prepared by slaking lime with water, stirring the slaked lime with the water, and then allowing the lime to subside. The clear fluid is, after 1 2 , or 24 hours, poured off, and is ready for use. A table has been prepared to facilitate the use of this plan : — 1 02). cit. CHEMICAL EXAMINATION OF AIR Size or Bottle. , Ounces. Lime Water. Point of observation is no jjrecipitate. Carbonic Acid in air per cent. 20-6 ..... -03 15-6 •04 12-5 •05 10-5 •06 9-1 •07 8-0 •08 7-2 •09 6-5 •10 6-0 •11 5-5 •12 5-1 •13 4-8 •14 4-5 •15 3-5 •20 2-9 •25 2-5 •30 2-0 •40 1-7 •50 1-5 •60 1-3 . •70 1-2 •80 The rule to remember is that the air around houses generally contains about "04 per cent of carbonic acid, and that our rooms should always be kept so that a 10-|- oz. bottle full of air, when shaken with ^ oz. of lime water, gives no precipitate. We then know that the air does not contain more than '06 per cent. It is often difficult to keep the air of a room below '07. If a precipitate is obserA^ed, we know that the air does contain more than •06 per cent, and we take a smaller bottle, say a 9 oz. bottle, the air of wdiich, when shaken with ^ oz. of lime water, gives, perhaps, no precipitate. We then say the air is worse than '06, and not worse than '07 ; accordingly, the amount must roughly be •07. If we wish to test the air as expe- ditiously as possible, and are not particular to ascertain CHEMICAL EXAMINATION OF AIR 335 the exact percentage, we may take a bottle of a size indicative of alternate liundredtlis. Instead of taking a 9 oz. bottle we may take an 8 oz., and treat 8 oz. of air in the same manner. If we obtain no precipitate we know that the air is not worse than "08 per cent. Having already ascertained that the air is worse than •06 we conclude that the air is contaminated with "07 or *08 per cent of carbonic acid. If no tnrbidity is occasioned on commencing with our 10|- oz. bottle, and we would like to know whether the air contains as much as "06 per cent, we must take a larger quantity of air, for example a 12|- oz. bottle. If, when this quantity of air is shaken with ^ oz. of lime water, no precipitate is procured, we know that the air does not possess more than '05 per cent, and if a precipitate is occasioned, we know that '06 per cent is the amount. The air to be examined is best introduced into the bottles by sucking out the air already contained in them with a glass tube. Fresh air enters to supply the void we create. The greatest care should be taken not to breathe into the bottle, for our breath is full of car- bonic acid. The bottles should be wide -mouthed, so that the sides can be wiped dry and clean. If the lime cannot be readily removed, they should be rinsed out with strong hydrochloric acid, followed by an abundance of water. There is great difficulty in ob- taining bottles of exactly the capacity required, but this could be overcome if there was any demand for such measures, by the special manufacture of bottles to hold accurately the quantities of air indicated. Ilimmetric Method. — This method is more accurate, ^i'"""^^"'° 1 • T • ^ r>i n -t 1-1 T Method. and involving the use oi but lew tools, which can be conveniently disposed of in one's pocket, is more handy. It consists essentially in ascertaining the smallest or 336 CHEMICAL EXAMINATION OF AIR minimum amount of air required to produce a precipitate of given density — lience tlie, name. Baryta water, which is very poisonous, is employed, because it is more sen- sitive than lime water. A standard precipitate is ob- tained by shaking -|- ounce of baryta water in a 23 oz. bottle in pure air, which generally contains -04 per cent of carbonic acid. The liquid is turbid and still translucent, but so that you cannot read through it. The endeavour is to ascertain the smallest amount of the air to be tested which is necessary to produce this standard degree of turbidity. We take a bottle which holds exactly 2^ oz., and place in it ^ oz. of baryta water, having first changed the air in the bottle by a few strokes of the finger-pump ; we then shake the 2 oz. of air contained in the bottle with the ^ oz. of baryta water, and count one (vide fig. 34). Fig. 34. We then pump 2 oz. of air through the liquid and again shake ^dolently and count two. When the tur- bidity is such that the words written on the slip of paper ^ afl&xed to the outside of the bottle become indistinguish- 1 The words written witli a lead-pencil on the label must be of such a depth of shade that the turbidity of the standard liquid just prevents them from beiue seen. CHEMICAL EXAMINATION OF AIR 337 able, we stop, and refer to a table that lias been prepared to economize the labour of calculation. Vol umes of Carbonic Acid in 100 of air. Number of ballfuls Wit h 2 oz. With 1 oz. of air. 1 )aU. ball. 1 44 2 22 3 14 4 11 5 088 6 074 7 063 8 055 9 049 10 044 17 11 040 16 12 037 14 13 034 13 14 032 12 15 029 116 16 11 17 10 18 098 19 093 20 088 21 084 22 08 23 077 24 ... •074 The J oz. ball enables us to estimate greater degrees of impurity than the 2 oz. one. "When the air of a place, wMch it is wished to test, feels close on first en- tering, I use the 2 oz. bottle, and if very close I employ the ^ oz. ball and bottle. As the silk valves are rather liable to get out of order, I dispense with them, and simply make a slit in the tube ^'<5- ^^- 338 CHEMICAL EXAMINATION OF AIR Store Bottle. connecting the ball and bottle, whicli allows of the expul- sion of air, but prevents its ingress {vide fig. 35). A weak solution of baryta ("1 to "5 per cent, the exact strength being unimportant) is employed, which is made by dissolving caustic baryta in distilled water. It must be stored in such a way that, on removing portions of it, air undeprived of carbonic acid shall not enter the store bottle. The arrangement here sketched, which was in constant use in the Board of Health Laboratory, Glas- ^ gow, and is to be found in Sutton's Volumetric Analysis, is a most con- venient one for withdrawing any quantities that are required of baryta water, or, indeed, of other standard solutions, in such a man- ner that air entering is freed from whatever body the contained solu- A. store bottle containing soiu tiou is designed to cxtract from it tion of caustic baryta. /^^^^ g ggx B. U tube fllled witli fragments ^ . It will be found very handy to have a dozen ^ oz. stoj^pered bottles with wide mouths, and to fill them from this store bottle. It is needful to carry a stoppered and capped bottle of hydrochloric acid to clean the little apparatus after each experiment, before it is washed thoroughly with water. In the air of a room which, at first pure, is gradually vitiated by the presence of persons, the smell of organic matter begins to be perceptible to one entering it from the fresh air when the carbonic acid reaches '06 or '07 per cent. When the carbonic acid amounts to '09 or '1 Fig. 36. of pumice stone moistened with caustic potash, through which air passes in order to enter the store bottle. C. Burette graduated in any manner that is required. D D. Shelves. E E E. Black indiarubber tubes. P. Clip. G. Rod for support of burette. CHEMICAL EXAMIXATION OF AIR 3 3 'J per cent, the air is termed " close " or " stuffy." The fcetid odour of organic matter becomes very disagreeahle when the carbonic acid exceeds "1 per cent. When the carbonic acid is as much as from '15 to '3 per cent, headache and vertigo are experienced, as the result of the vitiation of the air by this gas and its accompanying impurities. When people speak of good ventilation, they mean air with less than *07 per cent. A rough-and-ready mode of detecting the presence of Detection „f hydrogen sulphide in the air, wliich is a gas produced in suiphkie, the decay of organic matter — for example, in some ainmoDium / ® . -■- ' sulphide, marshes, in sewer gas, etc. — is bv means of acetate of lead and papers. " ''"™""'^- Ammonium sulphide, which, with hydrogen sulphide, is a constituent of sewer gas, is detected by nitro-prusside of sodium tests. Ammonia, a product of putrefaction and decomposition, is, if in large amount, observed by means of logwood papers. CHAPTEE XXVIII THE BIOLOGICAL EXAMINATION OF AIR The examination of air biologically resembles closely that of water. The difference consists in the arrangements Collectors for Collecting from the air the micro-organisms or germs organisms containccl in it. A glass jar about 6 inches high plugged with a stopper of cotton wool, containing at its bottom a shallow glass capsule, which can be easily removed by the help of a brass lifter and charged with sterile jelly, is opened to the access of the air under examination for a certain number of seconds or minutes. Cohn and Miflet employ Wolff's bottles (in which the sterile jelly is placed) and an aspirator or a Sprengel pump to draw a definite amount of air through the same. Hesse sub- stitutes a long horizontal fixed-glass cylinder for the Wolff's bottles, along the floor of which the liquefied nutrient jelly is allowed to solidify. Dr. Maddox's com- bined aeroscope and aspirator has been employed as a collector {vide page 298). A shallow watch glass filled with a nutrient jelly may be placed on the glass plate in the bell jar receiver depicted in Fig. 21 (page 300), in the mouth of which is an indiarubber cork perforated with two holes for entrance and exit glass tubes, the latter being connected with a Dancer's aspirator, by the help of which a known number of cubic inches of air can be transmitted over the sterile jelly. For the composition and mode of preparation of Koch's nutrient jeUy vide BIOLOGICAL EXAMINATION OF AIR 341 page 75. The nutrient jelly in whatever manner it is inoculated is placed in the " damp chamber " {vide fig. 9, page 83), or is maintained in the incubator at a tempe- rature of from 68° F. to 77° F., and daily inspected. The number of colonies or foci of growth which appear on the jelly can be counted or calculated approximatively as described on page 84. After the trial of many different kinds of collectors, the form of apparatus at length adopted by M. Pierre Miquel at the Montsouris Observa- tory and its mode of employment is thus described.^ It consists of a glass flask with a long neck, which ex- tends downwards into its in- terior and terminates in a minute aperture. The mouth of the flask is protected by a hood A furnished with a plug of sterilized cotton wool {vide fig. 37). The flask possesses two lateral tubes ; the one marked C being pro- vided with two plugs of cotton wool, and the other B being attached by a piece of rubber tube to a sealed up point of glass tube. Preparation for Experiment. — From 30 to 40 c. c. of distilled water are introduced into the flask, which is then heated for two hours at 230° F. in a steam bath. After cooling it is placed in the incubator ready for use. 2 or 3 little glass flasks, each containing beef broth, are then sterilized, so as to be fit for inoculation. Experiment. — A caoutchouc tube is fitted to C and an aspirator (after the removal of the hood) being attached, a certain known amount of air is drawn through ^ Annuaire de V Ohservatoire de Montsouris for 1886. Fig. 342 BIOLOGICAL EXAMINATION OF AIR the fluid. The hood having been strongly heated during its time of withdrawal is replaced. End of Experiment. — By alternate pressure and removal of pressure on the caoutchouc tube attached to 0, the liquid is raised up and down the tubular neck 10 or 12 times in order to wash its interior. After having broken oft' the sealed point B, we distribute the liquid in fractional proportions amongst the glass flasks containing sterilized beef broth. Finally 25 c. c. of this broth are introduced into the glass collector itself, and the internal plug of cotton wool in the tube C is projected into the flask by means of a platinum wire which has been heated. The amount of air passed by the aspirator should have been pre\'iously determined and proportioned, so that ^th or l^ths of the inoculated broths shall remain perfectly limpid. In this manner we are enabled to operate on a mixture of micro-organisms and water sufficiently dilute to admit of a calculation of their number. M. Miquel, by means of an aspirator attached to a clockwork apparatus, on wliich is exposed a nutritive paper ^ covered with a thick layer of freshly sterilized gelatine, also registers hourly the quantity of bacteria and germs contained in air by the enumeration of the number of colonies subsequently developed on it. He gives the accompanying records thus taken of pure and impure air. 1 Mode of preparation described in Annuccire de V Ohservatoire de 3Iontsoicris for 1886. r \^^ pure aif . impm'e air 9k lo &ee page 34-1 CHAPTEE XXIX METALLIC POISONS : AESENIC, COPPER, AND LEAD Arsenic, copper, and lead are sometimes found in the air in^genic, the neioiibourhood of smeltino; works, etc. The determina- copper, ar.ci lead. tion of the amount of these metals, which, when diffused through the air, exercise injurious effects on animal and vegetable life, fall rather within the scope of those legis- lative enactments that concern the contamination of the air by manufactories, such as the Alkali and Works Eegulation Act of 1881, under which scientific chemists are appointed as inspectors. The human system itself, when continually exposed to the poisonous influences of copper and lead, affords an excellent test of an exposure to an injurious amount in the case of those who work with these metals, such for instance as miners in copper mines, or painters. The effects on the body of these metals, even in the smallest doses, are so well known to every physician, that he requires but little chemical aid. It is different in the case of arsenic, for the effects of this metal give rise in minute doses to such obscure and incomprehensible symptoms of such great variety, that they often cannot be assigned to their rightful . cause without chemical assistance. A description of the several poisonous colours used to tint the cheeks, the hair, etc., to avert the appearance of old age and to dye articles of wearing apparel, will not fall within the province of this work, because they exert 344 METALLIC POISONS their poisonous effects by coming into contact with the skin. Arsenic, mercury, lead in the form of magenta, coraline,^ and other of the new dyes, are some of the most common poisons thus used {vide page 261). rsenicai Instances of the terrible suffering, misery, and even rail paper. ^^^^^^ |-|-^g^l- y^^lYQ occurrcd from the use of arsenical wall papers, from the preparation for sale of feathers, artijScial flowers, leaves, fruit, etc., swarm in medical publications. The poisonous greens, such as Scheele's, Schweinfurth's, Brunswick, Emerald, Paris, wliich are all confounded together by work-people, are used in enormous quantities, partly because they are very attractive in appearance and partly because they are cheap. Not less than 700 tons of these deadly greens are consumed in trade annually in this country. Many wall papers that are not green are loaded with arsenic, especially pale or white drawing- room papers, with an enamelled or opal white ground, which have yielded 15 to 25 grains of arsenic per square foot. The late Mr. Wigner, on examining samples some years ago of all the papers in a ten-roomed house, none of which were gTeen, discovered that five of them contained arsenic in such quantity as to be injurious to health. The Medical Officer of Health, in his inquiries after the causes of vague and obscure forms of illness, may often have occasion to examine the air of rooms poisoned by arsenic papers and furnishing materials. The public will not unfrequently bring him portions of wall paper w^ith which their rooms are adorned, in order that he may examine them and express an opinion thereon. It is as weU, therefore, for him to be acquainted with a simple means of testing for arsenic, not only to aid him in his own investigations, but to assist the public and their medical attendants. If it is wished to ascertain whether ^ Bulletin de I'Academie InqKriale de Medicine, February and Marcli 1869. METALLIC POISONS 345 a paper does or does not contain arsenic, the paper is scraped with a penknife, and the dust that is removed is tested. If we desire to find out whether particles of dust have detached themselves from the paper, and poisoned the air of the room, the dust that lies on the articles of furniture may be collected for examination. The dust of the paper, in whatever way oljtained, is mixed with an equal bulk of bicarbonate of soda (dried over a spirit lamp) and a little powdered charcoal. The mixture is placed in a dry test tube and heated. If arsenic is present, the characteristic odour of garlic is perceived, and a mirror of metallic arsenic is obtained as a ring on the sides of the tube. If the test tube is large, so as to allow of free access of air, octahedral crystals of arsenious acid, easily recognized by the microscope, will be found in- stead of the mirror. Eeinsch's test may be employed to show the presence of arsenite of copper in a paper. The paper having been soaked in a solu- tion of ammonia, which will dis- solve the arsenite of copper form- ing a blue liquid, is acidified with hydrochloric acid and then boiled in a test tube with one or two strips of brilliant untarnished-^ copper. If arsenic be present ^'^" "^' the polished metal acquires a steel-gray coating. The ^ Cojiper may be cleaned by heatiug it in a flame, by then applying a little nitric acid to it, and lastly ^vasbing it in water. !46 METALLIC POISONS copper is washed, dried on filter paper, and heated in a small test tube over a Bunsen's burner or spirit lamp, when arsenious acid in octahedral crystals, readily diagnosed by the microscope (vicle fig. 39), will be deposited in the cool part of the tube, if the paper con- tains arsenic. Or the green colouring matter may be scraped off the paper and dissolved in pure hydrochloric acid and water, and examined by Marsh's test. Granula- ted zinc, or zinc foil in fragments, is introduced into a flask with some water, and a little pure sulphuric acid is poured down the funnel. A few minutes should be allowed to elapse for the removal of all the ^ air from the flask. The gas evolved should then Fig. 40. — Maksh's Test. A. Flask containing dilute sulphuric acid and be collected in a test tube, and a lighted match zinc free from all traces of arsenic. '^6 appiiecl tO the tCSt B. Test tube for collecting small quantities of tube tO aSCCrtaiu whether the gas evolved. C. Tube of hard Bohemian glass that will not a miXturC of hydrOgCU fuse, drawn out to a point so as to form a jet. ^^^ atmOSphcric air is escaping, or whether hydrogen is alone given off. If air is still bemg expelled from the apparatus the gas in the test tube on being lighted will explode harmlessly. The gas escaping at the jet should on no account be ignited until two or three of these trials have been made. When the gas collected in the test tube does not explode, it is safe to light the jet. Having ascertained the purity of the chemicals employed, by depressing a piece of METALLIC POISONS 347 porcelain on the flame, the solution of the green colour- ing matter may be passed down the tube funnel and the flame again tested. If it consists of arsenic there will be a dark mirror of arsenic deposited on the porcelain. If there is any doubt as to the purity of the chemicals. Dr. E. Davy's sodium amalgam test, which finds so much favour in the United States, may be substituted, since sodium and mercury, of which the sodium amalgam is formed, are generally free from arsenic. This amalgam Dr. Davy's is prepared by adding 1 part of sodium to 8 or 10 of^^^J™^ mercury, and supplies us with a ready means of obtaining test, hydrogen free from arsenic. It evolves hydrogen gas when water is added to it. A fragment of sodium amalgam is dropped into a flask and the solution sup- posed to contain arsenic is introduced. A strip of paper moistened with an acidified solution of nitrate of silver ("25 gramme arg. nit., 5 grammes of water, and 2 drops of nitric acid) is blackened if held at the mouth of the flask. To verify the result, it is as well to treat the blackened paper with ammonium sulphide. The sulphide formed is insoluble in hydrochloric acid if arsenic be present, and is soluble in hydrochloric acid if antimony be present. If it is wished to ascertain the amount of arsenious acid (the common white arsenic of commerce) contained in a paper, a rough estimate may be easily formed. If the pattern of the paper consists of groups of green leaves, as is often the case, scrape off all the green arsenite from a single leaf and weigh it. The number of leaves in each square foot of surface of the paper having been counted, and the dimensions of the room having been taken, the number of leaves in the room is easily ascertained. If the green colouring matter is equally distributed over the surface of the paper a square inch of the paper should be operated on in place of a single leaf. A measurement of 34:8 METALLIC POISONS the room will readily give the number of square inches of surface. Two or three green leaves of a wall paper were recently sent to me with the request that I would ascertain whether the green pigment contained arsenic, and, if so, the quantity of the same. It had been estimated by the applicant that there were about 22,800 leaves in the room. All the green colour having been scraped off from a single leaf, by the help of a penknife, was found to weigh 16 milligTammes. Arsenite of Copper. Arsenious Acid. 2 Cu. 0., H 0., Asg O3 375 : 16 118S 198 Arsenious Acid. 375\3168/8 /3000V To convert the 8 milligrammes of arsenious acid into fractions of a grain, a weight that is more readily under- stood by the public, it is simply necessary to multiply by 15-5 and divide by 1000. Milligram. Milligram. Grs. in 1 gramme. 1000 : 8 : : 15-5 1000)124-0(-124 Ans. One leaf contains '124 of a grain, which is equivalent to 124 grains of white arsenic in every 1000 leaves, or nearly 6 ounces in the room. Some wall papers contain compounds of lead and copper (non- arsenical), but, although their employment is undesirable, we have but little evidence at present which would forbid their use. INDIRECT METHOD CHAPTEE XXX ESTIMATION OF OZONE AND OTHER AIR PURIFIERS The whole subject is so vast that it is extremely difficult to know how to concentrate it without omitting salient points of great interest. Ozone. — Ozone is condensed oxygen, or a very active, ozone lively, and energetic form of this life-giving gas. Its object in nature is to destroy, or, to speak more correctly, to render harmless by oxidation all offensive noxious products that, if permitted to accumulate, would produce disease and extinguish life. Take, for example, a little blood, and keep it in a warm place for months, until it putrefies. Wlien the odour is something horrible, sufficient indeed to create nausea, or sickness, send a stream of ozone over it, and its freshness, purity, and sweetness will be restored. Neither ozone nor the other air purifiers are to be found in the air of unventilated inhabited rooms or hospitals unless the windows are open, being speedily used up, and not replaced as they should be by the admission of fresh air, which nearly always contains them in greater or less quantity. Ozone can be prepared in a great variety of ways. It is perhaps most conveniently made by mixing three parts of sulphuric acid with two parts of permanganate 350 OZONOMETKY of potash.^ This mixture will continue to give off ozone for several months. It is associated in the air with other purifying agents, such as peroxide of hydrogen and acids of nitrogen. Peroxide of hydrogen, called also oxygenated water, is produced by a combination of the oxygen of the air with water. It is found sometimes in rain and snow. It also is a powerful oxidizing agent, for it very freely parts with its excess of oxygen. Its oxidiz- ing powers render it useful for bleaching, as it attacks vegetable colours vigorously. Young ladies used to purchase it for bleaching their hair, under the name of " auricomus," when it was the fashion for every one to exhibit flaxen locks. It so readily parts with its oxygen that a temperature of 68° E. is sufficient to disengage it, the warmth of the hand to the bottle which holds it being often dangerous when it is quite pure. Nitrous acid is produced whenever an electric spark passes through the air. It is one of the most valuable gaseous disinfectants and deodorizers known. It acts most energetically on organic impurities, removing the un- pleasant odours of the dead-house more readily (so it is said) than any other gas. This rapid action arises from the facility with which it gives up its oxygen. For deodorizing purposes, it is made by mixiag nitric acid and water with copper turnings. It is used more on the Continent than in this country. The amount of ozone, peroxide of hydrogen, and nitrous acid, which are all ^ Dr. Leeds states that wheu permanganate of potash is exposed to the action of sulphuric acid, chlorine is evolved in consequence of the presence of an impurity in the shape of a chlorate. Apart from the ease ^vith which chemistry enables us to distinguish ozone from chlorine, the smell of these two bodies is so difierent that there can be no difficulty in diagnosing the one from the other. Moreover on the fact that permanganate of potash emits oxygen when under the influence of sulphuric acid, rests the ex- cellent process for the estimation of peroxide of hydrogen in which the oxygen produced is measured. OZONOMETRY 351 powerful air purifiers, are measured by exposing to the air paper dipped in a solution of iodide of potassium. They all have the property of breaking up this salt and setting free the iodine, which gives the paper a reddish brown colour, of greater or less depth, according to the amount of these disinfectants present in the air during the time of its exposure. Sometimes, instead of all the iodine being set free, some of it goes to form an oxide of potassium, called the iodate which is a colourless salt. It is therefore always necessary to spray these tests after exposure with a solution of tartaric acid which sets free the iodine from the iodate, but does not interfere with the unacted upon iodide of potassium. We are then sure of obtaining all of the iodine set at liberty by the air purifiers. If we wish to ascertain the amount of ozone present in the air to the exclusion of the other air purifiers, we employ a paper which is alone acted upon by ozone, such as the iodized litmus paper. "With this test we do not take any notice of the amount of iodine set free, but we observe the amount of potash formed by the union of the ozone with the potassium. Potash, being an alkali, of course has the property of turning red litmus blue, whilst an acid turns blue litmus of a red colour. The greater or less conversion of the red litmus into blue, shows a greater or less quantity of ozone in the air. Scales have been prepared for estimating the depth of colour of the iodine papers in testing the amount of the three air purifiers, and of the iodized litmus papers for showing the amount of ozone. It was formerly the practice to employ starch tests, iodized which are composed of a mixture of iodide of potassium ^g^f^ and boiled starch, which became blue on exposure to the air from the formation of the blue iodide of starch. There are many different kinds, which may be looked upon now 352 OZONOMETEY as curiosities ; for example, Schonbein's, Lowe's, Jame de Sedan's, Lender's, Moffat's, etc. They are all more or less disposed to behave in an eccentric fashion ; now they colour, then they bleach ; sometimes they tint in a uni- form manner ; at other times they become marked with lines like a Scotch plaid, or with spots ; whilst they very frequently fade. Hence the records of observations ap- pear most contradictory, forming a mass of almost inex- tricable confusion. In support of this assertion, the opinions of a few who have made ozone a subject of study may be quoted : — " At the present time the modes of determining ozone, and the tests for ozone in the external air are very unsat- isfactory." — Dr. Richardson. " The greater part of the countless observations on the amount of ozone in the air are worthless." — Frof. Heaton. " The determinations which have hitherto been made are very vague and unsatisfactory." — Dr. Wetlurill. " Tests prepared from the same recipe, by different persons, give varied results." — Boehm. "If we expose the tests of Schonbein and Moffat together we do not get the same result, and even tests made by the same persons at two different times will not read alike." — Mr. Loive, of Nottingham. " All the methods employed are more or less defec- tive." — Dr. Scoresby-Jackson. " Until more certain means are discovered for estima- ting ozone, present observations must be received with great caution." — Davies. " The estimation of ozone is in a very unsatisfactory state. The great imperfection in the tests make it desir- able to avoid all conclusions at present." — Prof. ParJces. "No clear and consistent results have yet been obtained. Variations of light, wind, time, and paper, may OZOXOMETliY ooo cause clianges attribiited only to ozone, and there are no reliable means of checking them." — Admiral Fitzroy. " jSTo trustworthy observations on ozone are made in the United States of America." — Dr. Henry of the Smith- fiOJiian Institiition. These views refer to the antiquated practice of esti- mating atmospheric ozone with the iodized starch test, by suspension in a cage or box, and subsequent comparison with a scale containing gradations of colour. The exposure of any kind of test papers in cages is a most fallacious mode of observation, for they are measurers of the velocity of the wind, and may be called anemo- meters rather than ozonometers. The higher the wind the deeper the colours they assume, for the simple reason that more air passes over them. There is a special fallacy attendant on the employ- ment of starch tests in ozonometry, because there is every reason to believe that the iodide of starch is not a true chemical compound. ]\I. Duclaux declares that its forma- tion is purely physical, and results from the adhesion of the molecules of its constituents. It appears that JM. Personne and M. Guichard expressed the same opinion some years ago. The latter chemist, who examined the iodide of starch by the aid of the dialyser, writes — " The so-called iodide of starch is simply starch tinted with iodine." Watts considers that "the blue coloration is due to the formation of a loose combination of starch and iodine, or perhaps to the mere mechanical precipitation of the iodine upon the starch." The various circumstances which affect and modify the colour of the iodide of starch have been pointed out by Gmelin.^ Then, again, all of the iodine set free in tlie starch test does not sometimes combine with the starch. Some of the iodine set free occasionally forms a colourless iodate. 1 Handbook of Chemistry, xv. 97 (German edition). 2 A 354 OZONOMETRY It is, moreover, very difficult to obtain pure starch, and samples of the same kind of starch often vary much in strength. The errors associated with the employment of iodide of starch tests are indeed legion. Notwithstanding the existence of these irremediable defects inherent to the employment of iodide of starch in atmospheric ozonometry, which were brought by me before the scientific world in a prominent manner in 1873, the officials at the Montsouris Observatory have been throwing away their time and labour by employing cotton wool impregnated with iodide of potassium and starch. They have at length, it seems, discovered that what I told them years ago is but too true — namely, that the iodide of starch test is wholly unreliable. M. Marie-Davy writes : — " La difficulte de la methode con- siste en ce que I'iodure d'amidon manque de stabilite, qu'il se decolore a I'air, et qu'en presence de la potasse formee une partie de I'iode mis en liberte peut se trans- former en iodate. D'un autre cote, I'amidon s'altere au contact de I'air et des produits pyrogenes qu'on rencontre toujours dans I'atmosphere des grandes villes." They have now forsaken this untrustworthy iodide of starch reaction, and estimate the quantity of oxygen employed in the conversion of an arsenite into an arsenate,^ and efforts have been made to bolster up the belief in the starch tests of Schonbein, by making it appear that Schonbein's starch tests — plus certain corrections — agree in their indications with the results determined by the oxidation of an arsenite. Having had such an immense ^ The average amount of ozone furnished by this process for the eight years 1877-1884 shows a remarkable constancy in the composition of the air. Ozone in 100 cubic metres of air in the Park of Montsouris, near Paris. Milligrammes. 1877 1878 1879 1880 1881 1882 1883 1884 1-9 1-5 -8 -6 1- -7 11 1-7 OZONOMETKY 355 experience with starch tests, my intimate acquaintance with their comic behaviour would incline me to think that if there is any harmony between them and the pro- cess with the compound of arsenic, the latter must be worthless also. According to the most approved recent mode of observing ozone, and of estimating the amount of the air purifiers (ozone, peroxide of hydrogen, and nitrous acid), it is necessary to pass a known quantity of air over test papers of two different kinds at a knoion and unvarying velocity by means of aspirators, of which there is a great variety, such as Mitchell's aspirator, the tube aspirator, Dancer's aspii^ator, the injection aspirator, Andrews' as- pirator, the Montsouris aspirator, and the clockwork fan aspirator. The test papers are exposed in a box of a peculiar form, where they are protected from dust, light, and moisture. It would be impossible to give the reader in this handbook an adequate description of the mode in which ozone and the other air purifiers should be estimated. The fullest information as to how these bodies should be observed has already been published by me in my work on Ozone and Antozone, in which it occupies 136 pages. The errors associated with the old ozonometric method of Errors con- , T . . T , . -, nected with exposing starch tests may be here summarized. ow method. 1. Impurity of chemicals ) employed in the manufac- 2. „ „ paper j ture of the tests. 3. Formation of the iodate of potash. 4. Non-union with the starch of the whole of the liberated iodine. 5. Changes in the force of the wind. 6. Bleaching and fading of coloured tests from — A. Formation of the iodate of potash. B. Excess of moisture in the air. C. A high temperature of „ 356 OZOXOMETRY D. A great velocity of tlie air. E. A long exposure to „ F. Sulphurous acid in „ 7. Light. 8. Ozonometers ( = chromatic scales) faulty in construction. 9. Differences of aspect and ele-s-ation. I must refer to that work for the blue and red chro- matic scales, the ozone register and diagram, which in like manner cannot possibly be copied into this publi- cation. After a thoroughly accurate estimation of the amount of ozone present in the pure air of different climates, and daring the various atmospheric changes of each climate, we shall l;)e in a position to attempt an elucidation of the following and inany other questions which are of immense interest and importance to the human race : — 1. AVhat are all the sources of atmospheric ozone ? 2. How is it formed, and in what circumstances does it arise ? 3. What is its precise action on animals and plants ? 4. Has an excess or deficiency of ozone any effect on the public health ? 0. If so, what is the nature of that influence ? 6. "What is the effect of the presence of epidemics on its amount, as calculated by the improved ozonometric method ? 7. Does ozone oxidize one only, or all of the different kinds of organic matter found in the air ? The elucidation of that very interesting mystery respecting the supposed relationship betw^een an excess of atmospheric ozone and an epidemic of influenza is one which demands special attention, because of the fact that an excess of ozone artificially prepared will originate a catarrh. ozonometi;y 357 Peroxide of hydrogen. — The best method for the estima- pemxideof tion of this, apait from the other air-purifiers, involves ''^^^'■"8^"- much habour in its performance and cannot tlierefore Ije here described. Nitrous acid is recognised in so ready a manner when Nitrons present in the air, that a few lines must be devoted to a^*""" consideration of its mode of detection. Griess, who recommended the employment of meta- phenylene diamine as a delicate test for nitrous acid {vide page 110), has described a far more sensitive test for this air purifier. His later test, in which naphthylamine is used, renders it possible to distinguish 1 part of nitrogen in 1,0 0,0 0,0 parts of water. Mr. Eobert Warrington recommends ^ that this remarkably deUcate reaction be applied in the follow^ing manner : — To the water in a test tube suspected to contain nitrous acid are added, suc- cessively, one drop of dilute hydrochloric acid (1-4), one drop of a nearly saturated solution of sulphanilic acid, and one drop of a saturated solution of hydrochloride of naphthylamine. Xitrous acid forms with the sulphanilic acid a diazo-compound, which is further converted by the naphthylamine into a body of a rose or ruby colour. A mixture of freshly -distilled water and these reagents remains colourless when left in a half-filled stoppered Ijottle, but when exposed to the air in au open vessel may be observed to deepen in tint from day to day as the absorption of nitrous acid proceeds. Test papers are easily prepared by soaking small strips of Swedish filtering paper in a solution, made by dropping a drop of each of the reagents into about two fluid drachms of distilled water, and then drying them by suspending them in a cupboard. ^ " Xote on the appearance of nitrous aeiil during the eA'aporation of water." — Juurnnl Chemical Socictij, 1S81, p. 229. PAET III SKETCH OF RELATION BETWEEN CERTAIN METEOROLOGICAL VARIATIONS IN THE CONDITION OF THE AIR, AND STATES OF HEALTH AND DISEASE In the consideration of " all influences affecting, or threatening to affect, the public health within his district," the medical officer of health should not only note all sudden and great changes of barometric pressure and heavy falls of rain, which are important factors in the production of those atmospheric conditions on which movements of underground air and water depend, but should make observations on those climatic and topo- graphical peculiarities which are likely to exert any action on health. The value of his observations will be increased by a comparison with published readings taken simul- taneously over large neighbouring areas and by a study of the laws that govern the movements of the air. The variations in the temperature, humidity, pressure, and electric state of the atmosphere, as well as the effects of these changes on the moral and physical condition of nations and individuals, form a most extensive field of study, and one, moreover, of the highest possible interest. The influence of climate on the sanitary condition of all animals, and especially of the most highly organized being in the scale of creation, has occupied for more than 2000 years, and still engages, the attention of scientific men. METEOROLOGICAL VARIATIONS 359 The great subject of weather and disease has been worked at ever since the times of Pythagoras, whose doctrines were supported by Hippocrates/ the father of medicine. These distinguished philosophers divided nature into four qualities — viz. cold and warmth, dryness and moisture. They considered cold with moisture to be hurtful, and warmth with dryness to be beneficial qualities. The three following rules have been accepted by the few, and unrecognized by the many, for hundreds of years : — 1. A preternaturally dry air, with a high temperature, predisposes to the development of fevers and intestinal disorders. 2. A very moist atmosphere, accompanied by a low temperature, is apt to induce bronchial and rheumatic affections. 3. A very dry atmosphere, when associated with a low temperature, has a tendency to excite inflammations of the respiratory organs. The labour of the past has borne, however, some little fruit, for we are obtaining an increased knowledge of the influence of meteorological conditions on health. The bearings on health of the disturbances of the atmospheric sea above and around us, occasioned by the great cyclonic and anti-cyclonic changes throughout the world, are better understood, thanks to the telegrapliic system of reporting the approach, direction, and rate of progress of storms, and the elucidation of the laws that govern their motions. As to cyclones in which the winds circulate with great cycinnes. rapidity around and towards the centre or point of loioest barometric pressure, from which rises a vast ascending current, physicians with meteorological tastes cannot fail to have noticed that attacks of neuralgia in the form of ^ Vide " ire pi aepiov, vSaruv, tottwv." 360 METEOROLOGICAL YAPJATIOXS IX RELATION migraine aud other nervous maladies seem often to recur at the approach of a considerable fall of the barometer, especially when this culminates in rain. Dr. AVeir Mitchell gives the following result of his observations on this connection in the case of a Captain Catlin, U.S.A./ who suffered from attacks of neuralgia in a painful stump: — " It was rather the fact of a storm, or the disturbance of pressure, that induced, or at least accompanied pain, than its depth, duration, or extent." Dr. Mitchell adds, " Every storm as it sweex:)S across the continent . of America consists of a vast rain area, at the centre of w^hich is a moving space of greatest barometric depression, known as the storm centre, along which the storm moves like a bead on a thread. The rain usually precedes this by 550 to 600 miles, but before and around the rain lies a belt which may be called the neuralgic margin of the storm, which precedes the rain about 150 miles. This fact is very deceptive, because the sufferer may be on the far edge of the storm basin of barometric depression, aud seeing nothing of the rain, yet may have pain due to the storm. It is somewhat interesting to figure to oneself thus a moving area of rain girdled by a neuralgic belt 150 miles wide, within which, as it sweeps along in advance of the storm, there prevail in the hurt and maimed limbs of men and in tender nerves and rheumatic joints renewed torments called into existence by the stir and perturbation of the elements." Anti-cyclones, or periods of high barometric readings, in which the winds circulate very slowly around and out from the centre or point of Ixvjhcst pressure of the baro- meter, which is filled by a slowly descending current from the upper regions, last longer than cyclones, often continu- ing for many days. In summer they are characterized by hot sultry weather without a breeze, and in Avinter l)y cold ^ A/iierican Jounutl of (he Mcdiml Sciences, April 1S77, TO STATES OF HEALTH AND DISEASE oGl fogs. The former climatic condition is often accompanied by diarrhoea and cliolera, whilst the latter in winter is notorions for bronchial and catarrhal affections. To descend from the general to the particular, we know that, as regards the commencement of life, the offspring of man and the other animals born in the cold season of the year has a higher probability of life during the first year than if born in the hot season, although an exposure to excess of cold is highly destructive to infancy ; and as regards the close of life, that the mortality by cold due to age doubles every nine years from the age of twenty, so rapidly does the power of resistance to cold decline with age. It will be useful to consider : first, the effects of differences of temperature, solar radiation, moisture, and barometric pressure, direction of the wind, etc., on health ; and, secondlij, the meteorological conditions which appear to favour or retard the development of those diseases that seem to be influenced most bv climatic variations. The Tem- perature of the Air. CHAPTEE XXXI 1. THE INFLUENCE OF DIFFERENCES OF TEMPEEATURE, SOLAR RADIATION, MOISTURE, AND BAROMETRIC PRESSURE OF THE AIR, DIRECTION OF THE WIND, ETC., ON HEALTH A. The Tein])erature of the Air = A ir Warmth. The average mean temperature of the capitals of England, Scotland, and Ireland, deduced for long periods, which have been published by Messrs. Glaisher and Buchan, are valuable, and they give at a glance a general idea of the differences between the temperature of these countries. o g eg c >-5 < & S 1-5 < +2 o O > o j, vol. iii., Xew Series, Xo. 20, October 1876. 366 THE TEMPERATURE OF THE AIR AND HEALTH North of England " the borrowing days," as they are sup- posed to be lent by the colder month of March. Madler-^ examined the mean temperature of May in Berlin for eighty-six years, and found a retrogression of temperature amounting to 2 '2° F. from May 11 to 13. Cool rainy summers are generally periods of low mortality. Cold winters and hot summers, although agreeable to the strong and healthy, are fatal in their effects on the general population. Intestinal disorders kill in hot summers, whilst pulmonary affections destroy life in cold winters. Dr. Eichardson states:^ "that, (1) the phenomena of catarrhs or colds are confined witliin a range of temperature extending from a mean of 41° F. to the extreme cold of the Arctic chmate ; (2) yellow fever can only continue in parts of the earth where there is a mean temperature above 68° F.; (3) typhus fever flourishes only in regions having a range of temperature lying between 40° F. and 62° F.; and (4) the phenomena of phthisis pulmonalis are so limited by a given degree of cold that they cannot exist in the Hebrides, Faroe Isles, Iceland, and the Arctic Eegions." Some years ago a considerable discussion took place in the medical journals as to whether phthisis pulmonalis did or did not occur in Iceland, the result of which terminated in the production of evidence which showed that it is found there, and that the hilly tablelands of Mexico are the only parts of the civi- lized (?) world where the disease is unknown (-yic^c page 280). Is it not probable, in view of recent bacteriological researches, that isolation has much to do with the immunity enjoyed by the inhabitants of these islands and out-of-the-way places ? As regards the climate of this country it has been recommended : ^ — ^ Verhandlung cles Vcreins zur Beford des Garteiibanes, 1834. ^ Diseases of Modern Life. 3 " The effect of cold on children." — Brit. Med. Journal, Dec. 25, 1875. THE SOLAR RADIATION 367 1. That no child too young to walk or run should be taken out of doors when the external temperature is below 50° F.^ 2. That the rooms in which children live and sleep should never be below 58° F.; and 3. That the dayroom should be three or four degrees warmer than the bedroom. The relation between certain varieties of coup de soleil or heat apoplexy, as well as other ajffections, and the indications of solar and terrestrial radiation thermometers, is a subject that, if worked at, will probably yield valuable results. B. TJie Solar Badiation. The sun -warmth is a factor in the production ofsun- climate of considerable importance to health, and is^^^'°^ estimated by the means of a solar radiation thermometer {vide page 414). The space at my disposal will not permit me to dwell on its relation to the duration of sunshine, as registered by the several ingenious arrangements for its measurement, but will only allow me to direct attention en passant to the very suggestive influence on life and growth, shown by the relation between the amount of sunshine and the yield of hay and other vegetable crops, the abundance during years of little sunshine being compensated for by a deficiency in weight. Dr. Frankland has pointed out^ that the sun-warmth is influenced : (1) by the colour of the soil, and our other surroundings and their consequent absorbent power ; 1 The No. 1 recommendation is too stringent, and requires the addition of the words, ' ' unless carried in the arms of an adult, so as to derive warmth from an external source." On several occasions have young children come under my charge who have been exposed in perambulators to great cold, in whom a complete cessation of the flow of bile into the intestinal canal has occurred. 2 "The Climate of Town and Countrj^," in Nineteenth Century. July 1882, 368 HYGEOMETRIC STATE OF (2) By reflection from land (snowfields or chalk-pits) or water ; and (3) by the amount of watery "S'apour in the air. " The nearer the colour of the ground approaches to white, the greater will Ije the sun's warmth and the cooler the air ; whilst the darker the colour, the warmer will be the air, and the less will the heat of solar radiation be felt. The darker the colour of our houses the cooler the streets, and the hotter the rooms during sunshine. The lighter the colour of the houses, the hotter the streets and the cooler the rooms." The dark, distinguished from the luminous, heat rays are sifted out of tlie air by the watery Aapour in its low^er strata, hence the higher we ascend into the air the greater is the sun's warmth. He points out that the sun's warmth, unlike the air temperature, is greater in Norway than at the equator, because the air is colder, and therefore drier, in the Arctic than in the hot reo'ions of the world. o Vapour in a cubic foot of air. ; Grains. 1-8 15-2 Arctic voyagers have stated that, with the temperature in the shade far below freezing-point, the pitch will boil in the seams of the vessel where it is exposed to the sun. Dr. Frankland has drawn a strong contrast between the sensations experienced wdieii he was exposed to the following opposite climatic conditions : — Di-y liulb. Wet bulb 36 33 96 93 Bellaggio Summit of the Diavolezza Pass Sun Wanntli. Air Warnitli. Ktiiiarks. 72° 107° 83° 43° Heat most oppressive. Delicious sensation of coolness. 1 He omits all reference, however, to the influence of the hygrometric condition of the air, Avhicli was probably four or five tmies RTeater at the former than at the latter THE AIR AND HEALTH 369 station, and which has much to do with the sultry character of heat. C. The Hygrometric State of the Air. Whilst the air is never without some moisture, the The amount present in the air is largely due to its tempera- ™g^^^_''^° ture, the capacity for retaining moisture in an invisible gaseous form being greater when the temperature is high than when it is low. The aching of rheumatic joints and of corns, the extraordinary noises that sometimes proceed from chairs and tables, and the condition of certain epithelial struc- tures, such as the hair and skin, are often signs to the public of the approach of rain, all being the result of an excess of humidity in the air, due to the great alterations in size which fibrous, epithelial, and ligneous bodies undergo by the addition or subtraction of moisture. How cleverly did the great Jenner embody in a few lines of verse, " On the Signs of Eain," the effects of this atmospheric change — " Hark ! liow the chairs and tables crack, Old Betty's joints are on the rack." The decrease of the pressure of the air which generally accompanies an excessive hygrometric condition has doubt- less, however, much to do with the painful condition of that old lady's joints. "We know but little of the influences of varying degrees of humidity of the air on animal life. It is unquestionable that an excess or deficiency of the normal amount of moisture in the air exerts a very decided action on the state of the public health. People in health merely feel slightly depressed when the air is rather damp, and somewhat ii'ritable when it is unusually dry, but to invalids even a change of two or three per cent in the humidity is perceptible. An excess is the more prejudicial, because aqueous vapour 2 B 370 HYGEOMETEIC STATE OF possesses a powerful affinity for organic matter, and serves both to preserve and diffuse it. We all of us have fre- quently experienced the enervating effects of a fog, which has been termed " half an air and half a water," and the return of our usual mental and bodily vigour on its removal. When we remember that all depressing agents predispose to disease, the subject of humidity in relation to hygiene, connected as it is so intimately with that of climate, cannot be too diligently examined. Insular climates, in the temperate latitudes, are necessarily humid to a certain extent, especially if the temperature is low. Wlien there is in addition an excessive rainfall, a damp, foggy, and relaxing climate is produced, which often exercises an injurious influence on the health of those unacchmatized to it. The voice of Grassini was reduced nearly an octave by the relaxing effect of the air of this country. Her vocal organs were restored, however, to their normal condition on her return to the drier climate of Italy, Female The vicw has been expressed that the degree of ^^" ^' moisture of the air is intimately associated with the degree of beauty in the human female, and especially with its duration. The average hygrometric state of the air is but one of the many factors concerned, which, by their union, form the climate of a country, by which the female body is undoubtedly influenced to a consider- able extent in its development. Temperature indubitably exerts an effect which is perhaps scarcely if at all inferior. Warm moist climates, in the temperate regions of the earth, have been considered to produce more beautiful women, whose beauty endures longer than countries possessing different qualities of climate. As we leave the temperate climes for the sunny south, where develop- ment is more rapid, and the period of puberty earlier, we notice that female beauty is very evanescent, and is soon THE AIE AND HEALTH 371 on the wane. As the temperate latitudes are left for the northern, colder, and drier climates, there is a coarse- ness, and want of the softness and delicacy so charac- teristic of the women of the south. Modes of life, differences of race and character, as well as the kind of climate, have, of course, some considerable action on the grace and loveliness of the female. This sulj- ject is one of great magnitude, on which there will necessarily be a divergence of opinion, as the question of taste is very much involved. I only allude to it as one deserving of thought. An excess of aqueous vapour in the atmosphere has An excess, not only a depressing effect on the nervous system, but it interferes with the cutaneous and pulmonary exhala- tions. If the temperature is high (65° to 80° F.), saturated air is sultry and oppressive. If low {e.g., a Scotch mist of 36° F.), its chilling influence penetrates all clothing. At least one half of the patients who apply for relief during the winter months to the physicians of the metropolitan and provincial hospitals of this country are afflicted with colds, coughs, bronchial and rheumatic affections. The prevalence of these disorders at this season is, without a doubt, due partly to the coldness in association with the excessive moisture of our very change^ able climate. Above 80° R, air of excessive humidity becomes injurious ; and it has been doubted as to whether life can be prolonged in such air at a temperature between 90° F. and 100° F. A very dry air is considered by some as less deleterious a defici- to health than a very moist air. Assistant- Surgeons ^""^^^^ Lauderdale and Eoss, in a report relative to Fort Yuma, California, write : ^ — "With the thermometer at 105° F., the skin becomes dry and hard, and the hair crisp, and furniture falls to pieces. Newspapers, if roughly handled, ^ Quarterly Journal of Science, April 1878. 3 / 2 HYGROMETEIC STATE OF break. Egcjs that have been on hand for a few weeks lose their watery contents by evaporation, and the re- mainder is tough and hard. A temperature of 100° F. may exist for weeks in succession, and there will be no additional cases of sickness in consequence. We have none of the malarial diseases." Dr. Ballard's ^ inferences as to the effect of variations in atmospheric moisture, as represented by the readings of the hygrometer, and the estimation of the rainfall on the public health of a portion of London, are thus given by him : — " 1. That in the colder months of the year the mean temperature is, on the whole, more important as a con- dition determining the absolute quantity of sickness than the amount of accompanying atmospheric moisture. 2. That in the warmer months of the year, on the other hand, the amount of atmospheric moisture is more im- portant as a condition determining the absolute quantity of sickness than the mean temperature. 3. That, both in the colder and warmer seasons of the year, a compara- tively dry condition (for the season) of the atmosphere is more damaging to public health than a comparatively moist condition of the atmosphere. The amount of rainfall is more important at comparatively low than at comparatively high temperatures, in regulating the absolute quantity of sickness." Writers on cholera in India have pointed out the coincidence of maximal rainfall and minimal cholera. The artificial climates which we manufacture in our houses and public buildings are far more deleterious to health than any atmospheric vicissitudes as to moisture. The air of The air of our rooms has a tendency to be preternaturally dry, and when so is often oppressive and unwholesome. The degree of moisture of air is shown by the hygrometer, 1 Op. cit. our rooms. THE AIR AND HEALTH 373 wliicli consists of two thermometers, one the dry bulb, and the other (covered with muslin and attached by a lamp wick to a feeder of water) the wet bulb. The difference between these bulbs is about five or six degrees in a healthful atmosphere. In rooms warmed by radiant heat it reaches often eight degrees ; whilst in rooms heated by hot air a difference of fifteen to seventeen degrees is often noticed, which is unwholesome and un- pleasant. Although so many different kinds of stoves and other appliances, such as hot water pipes, etc., for heating rooms have been devised, that important point seems nearly always to have been overlooked, namely, the maintenance of a healthful amount of moisture in the air. I have seen pans of water placed on iron stoves to counteract the unpleasant effects caused by the dryness of the air, and have seen the water steaming, and even boiling. In such an apartment there was an excess of moisture in the air which made me feel very uncom- fortable, creating the disagreeable sensation which one experiences on entering the house of a laundress ; the hygrometer in such a case giving a difference of onlj one or two degrees, showing that the air was almost saturated with watery vapour in an invisible form. The air sometimes becomes almost saturated with the aqueous vapour that proceeds from the pulmonary and cutaneous surfaces in crowded halls or rooms. Prof. Sanders relates ^ an anecdote, narrated to him by a Eussian officer, of the production of a shower of snow that fell on the audience in a concert-room by the sudden opening, in very cold weather, of a window, for purposes of ventilation. Even now, when the study of health and the influ- ences which deteriorate and promote it, coupled with the prevention of disease, are the great subjects of the day, rivalling in interest the kindred one of the cure of disease, ^ Handhuch der offcntlichcn Gesundhcitspflcge. 374 THE PRESSURE OF THE AIR there seems a complete ignorance or apathy in regard to this subject amongst physicians and leading architects. The modern On visiting somc ycars ago the completed portion of holpTtai. ^^® New Edinburgh Eoyal Infirmary, which is fitted with all the most approved and recent appliances for heating, ventilation, etc., and which is considered to take the place, previously occupied in turn by St. Thomas' Hospital, London, and the Lariboisiere and Hopital de Menilmontant in Paris, of the modern pattern hospital, I was astonished to find that no provision whatever existed for supplying moisture to the air dried by the coils of hot water pipes that are seen in so many places. If gardeners were to treat their greenhouse plants thus, healthy life and growth would be impossible. Horticulturists always furnish their hot water pipes with long troughs, filled with water, that rest on the pipes, and thus maintain an artificial climate, closely resembling that to which the plants have been accustomed, in which air is enabled to lick up as much water as its temperature will permit. i). Tlie Pressure of the Air. Tiie There is a strong popular belief that old wounds, in- theAir. jurics, discascd bones, and rheumatic joints are the seat of discomfort, or even pain, on the approach of a storm, which, speaking generally, means in this country a sudden decrease of at least ^ inch of the mercurial column. Eichardson and others tell us that when the body is ex- posed to low barometric pressure there is a tendency to exudation of fluid from wounded surfaces, a feebleness in the healing of wounds, a susceptibility to disturbance in the body generally, and a proneness to the production of secondary fever by the absorption of discharges which have undergone some decomposition. The outcome of these facts has been the establishment of the law that no A\D A STATE OF HEALTH 375 important surgical operation should be performed when the barometer is low, or when it is steadily falling. The principal effect of diminished pressure of the atmosphere is distension of the capillaries. "We all recognize, as one of the exciting causes of apoplectic seizures, a rapid diminution of atmospheric pressure producing a sudden capillary engorgement. Dr. M. A. Veeder, of Lyons, New York, suggests that there is a difficulty in the adjustment of the volume and rate of the circulation of the blood to the varying atmospheric pressure upon the surface of the body, and consequent unusual strain on the weakened bloodvessels. Dr. Murray, of Forfar, is in the habit of advising his elderly patients who have weak hearts and degenerated arteries to observe the strictest moderation in eating, drinking, and in mental and physical exertion, when the barometer suddenly rises and falls. Mr. Wood, of King's College Hospital, introduced the question in the British Medical Journal in the spring of 1872, as to why cases of joint disease are invariably worse during the warm, moist days of winter ? It was curious that his attention should have just at that time been pai'ticularly called to the connection, for the pressure of the air in London had been less early in that year than had been noted for nearly thirty years. Indeed, it was stated, on the authority of the editor of the Meteorological Magazine, that only on two occasions during the present century had the barometer been so low as on January 24, 1872. An exacerbation of the symptoms in cases of joint disease may be due to low barometric pressure, acting in a manner which may be thus explained : — In the solid, inelastic articular expansions of the bones, which are sur- rounded by firm inextensile textures, forming the joints, the minute nerves, shown by Kolliker and others to per- meate the cancellous and compact structures in company with vessels, are pressed by these vessels, when enlarged. 376 THE PRESSURE OF THE AIR against the unyielding walls of th.e channels through which they pass. Although the nerves of bones do not generally afford healthy individuals any conscious sensa- tions, yet, in diseases of the joints, the bones, when congested or the seat of inflammation, become painful. Tissues, not supplied with rigid canals like bone, yield to pressure during any temporary increase in the size of the minute vessels. In such tissues, vascular distension, from a diminution of the pressure of the air, is unassociated with pain, because the nerves accompanying the vessels are uninterfered with. Low barometric pressure and an excess of humidity of the air offer conditions most unfav- ourable for the removal of heat by evaporation and radiation from a congested or an inflamed joint. Teeth, which have a nutrient system very similar to that pos- sessed by bone, become painful when the pressure of the air is suddenly lessened, for the same reason. The nerves of the tooth being in a morbid condition from caries, are temporarily irritated by the capillary enlargement. How is it that joints which are not diseased ache when the barometer is low ? I am not aware that this occurs in the young and healthy. Experience teaches us that old rheumatic people often complain of this s}Tuptom. Such persons, whose joints are not in a perfectly healthy state, are generally worse during damp weather, in consequence, I presume, of imperfect elimination by the skin, and of the lowering of the vitality of parts (whereby the action of a morbid condition is favoured), — changes undoubtedly induced by the meteorological conditions, the effects of which we have been considering. It has for a long time been held that increased atmospheric pressure artificially applied exercises an ancemiating and compressing action in the peripheric tissues ; that it diminishes the frequency of the pulse and the calibre of the small vessels generally, thus increasiner the obstacles which the vascular walls AND A STATE OF HEALTH 377 oppose to the current of blood from the heart. M. Vivenot states that this dmiinution iu the size of the vessels may- be seen on the conjunctiva, on the ear of the rabbit, and on the vessels of the retina, and that rarified air produces contrary effects {VircJiows Archiv. 1866). The hsemorr- liages and peripheric congestions observed in aeronauts, and in divers and miners, are in this mechanical manner accounted for. M. Bert^ and Forlanini^ have impugned the correctness of this view, and state that the calibre of the cap- illaries does not undergo change under the action of com- pressed air. The therapeutic employment of compressed air, which is given at a pressure of from 1 to 1 atmospheres, in bronchitis, asthma, and other affections, is now a recognized mode of treatment, as, for example, at Ben Ehydding, in Yorkshire, and at some establishments in France and Germany. The physiological effects are said to be the following : — 1. Augmentation in the amplitude of the inspirations ; 2. Diminution in the number of respirations in a given time ; 3. Prolongation of the expiratory act ; 4. Gradual augmentation of the capacity of the lungs ; 5. Superoxygenation of the blood, increased activity of the organic combustion, and elevation of temperature. The effects of diminished pressure of the air are an increase in frequency of the respiratory and circulatory acts, and a reduction of the activity of the nutritive pro- cesses, as shown by the amount of urea eliminated. The treatment of certain pulmonary diseases by com- pressed and rarified air as a substitute for change of climate has been introduced into the United States by Dr. H. E. Williams under the somewhat ponderous title of " Pneumatic Differentiation," as a new method.^ The subject of the effects on health of changes in 1 Comptes Rendus, August 19 and August 26, 1872. 2 Gazzetta Medica Italiana, Lonibardi, March 31, 1877. 3 Kcio York Medical Record, January 17, 1885. 378 DIEECTION OF WIND AND HEALTH atmospheric pressure ^ should be more clearly ascertained, and it offers a wide and encouraging field for exploration. ]\Ieteorological vicissitudes appear to exert an influence on nervous maladies. Persons whose stumps of amputated limbs are painful sometimes get into a morbid and hysterical state of mind ; and in their prospective study of their discomforts, this hyperaesthetic condition gives rise to fanciful imaginary ideas. It is the experience of those who have the care of the insane that a sudden and great decrease in atmospheric pressure is generally accompanied by an increased excita- bility, more apparent amongst some forms of mental disease than others. The late Dr. Day, of Geelong, connected " an epidemic of suicide which prevailed in Australia in 1872 with a period of low barometric pres- sure. Dr. Eansome has observed ^ that a high degree of atmospheric pressure is favourable to the production of neuralgias. E. The Direction of the Wind. The West and north-west winds are considered more the Wind, favourable to health than south and south-west winds, which are generally warm and soothing to invalids, and others with an irritated pulmonary surface. North and north-east are not considered unfavourable to health, and are generally enjoyed by those who are robust. The east winds of spring are proverbially deleterious, except to the strong and healthy, by reason of their coldness and dryness. The heat of the sun is greater when the air is dry ■^ Vide Effets Physiologiques et Ap2^lications TM^'ajxutiques de I'Air Comprime, by Dr. J. A. Fontaiue, 1877. ^ Australian Medical Journal, November 1872. ^ " On Atmosiaheric Pressure and the Direction of the Wind in relation to Disease," read before the Manchester Philosophical Society. DIRECTION OF WIND AND HEALTH 379 than when it is moist, for the humidity of the air acts as a screen to the sun's rays. A sudden exposure of the body to extremes of temperature, such as are experienced when passing out of the oppressively hot sunshine into the icy cold shade, is injurious to the weakly, for it is unable to accommodate itself readily to the rapid transition. The dry east winds are not complained of so much if they blow in February as in March or April, because we do not receive so much heat from the sun in the former as in the latter months, and are not therefore exposed to the same extremes of temperature. East winds have been especially connected with the production of neuralgic affections, and the moist warm relaxing winds from the south-west have to a less extent been blamed. Dr. W. Mitchell found that of 50 cases of amputation of limbs less than half felt unusual sensations upon the coming of or during an east wind. Of the rest, two-thirds insisted on their power to predict such a change of weather, but said they were unaffected by a thunderstorm or by rain coming from the south. Dr. Ballard's observations, to which allusion has already been made,^ lead him to believe that westerly, southerly, and south-westerly winds are associated with a larger amount of sickness than northerly and north-easterly winds. No. of Weeks. Sum of Sickness in new cases. Mean. W.S.S. 2 984 497 s.w. 103 48,550 471 w. 7 3273 467 N.W. 5 2312 462 N. 3 1382 460 Var. 47 21,660 460 N.E. 33 14,952 453 N.N.E. 4 1790 447 Op. cif. CHAPTEE XXXII 2. THE METEOEOLOGICAL CONDITIONS WHICH APPEAR TO FAVOUE OR RETARD THE DEVELOPMENT OF CERTAIN DISEASES The influence of season is recognized by physicians in the treatment of disease, and by surgeons in the repair of injuries. When aU animal and vegetable life exhibits evidence of growth in spring, the most intractable forms of disease will sometimes yield to treatment. This \is medicatrix nature is especially seen in the young, but is also frequently noticed in the aged. It will be useful to dwell briefly on the relative prevalence of certain diseases during the several months and seasons of the year, in order to ascertain the influence exerted on them by meteorological changes. 1. Surgical fever and shock after operations. 2. Smallpox. 3. Measles. 4. "VA^ooping cough. 5. Scarlet fever. 6. Fever. C Diarrhoea. 7. < Dysentery. ( Cholera. 8. Bronchitis, pneumonia, and asthma. SEASONAL METEOROLOGY AND DISEASE 381 9. Phthisis. 10. Diphtheria. 11. Hydropliobia. 12. Erysipelas and puerperal fever. 13. Insanity. 14. Eheumatism. 1. Surgical Fever after operations. — Dr. Richardson surgicai shows -^ that there are differences in the mortality of ^ ^^'^' ^" certain diseases which are attended by fever or increment of animal heat during the several seasons of the year. He found, from an analysis of 139,318 deaths from all diseases, during the years between 1838 and 1853, that the mortality from three of the diseases of this class, held the following proportions : — shock. First Quarter. Jan. Feb. March. Second Quarter. April, May, June. Third Quarter. Julj', Aug. Sept. Fourth Quarter. Oct. Nov. Dec. Scarlet Fever . 20-809 18-978 26-234 33-976 Erysipelas 25-144 23-444 22-337 29-174 Carbuncle 29-771 19-685 24-409 29-133 He points out that the last quarter is the central quarter of the year in which these diseases are most fatal, and that December is the centre of a period of seven months which commences in September, during which there is occurring in the animal organism a marked modification in the nutrition, as compared with the five remaining months from April to August. Admitting that whenever there is any considerable increase of the animal temperature, there is danger, unless there be established a compensation by radiation and specially by evaporation of water from the body, we find that the fourth quarter of the year is more distinguished than the other quarters for those meteorological conditions 1 "On Meteorological Eeadings in relation to Surgical Practice." — Medical Times and Gazette, January 29 and February 5, 1870. 382 METEOROLOGICAL CONDITIONS WHICH FAVOUE which are most unfavourable to equalization of heat by evaporation and radiation, namely, low barometric pressure, excess of humidity of air, and a temperature low, but not low enough to compensate for increase of heat by arrest of oxidation or by abstraction of heat. Dr. Eichardson has accordingly drawn up certain rules for the guidance of surgeons in the performance of opera- tions which will admit of delay, until natural conditions arise favourable to operative work, whereby surgical fever, which often creates such fatality, may be prevented. Tlie time is favourcible for o;perations — (ft) Wlien the barometer is steadily rising. (&) When the barometer is steadily high. (c) When the wet bulb thermometer shows a reading of five degrees lower than the dry bulb. (cl) When, with a high barometer, and a difference of five degrees in the two thermometers, there is a mean temperature at or above 55° F. (e) Wlien the wind is west or north-west. TJie time is unfavourable for operations — (a) When the barometer is steadily falling. (&) Wlien the barometer is steadily low. (c) When the wet bulb thermometer approaches the dry bulb within two or three degrees. {cT) Wlien, with a low barometrical pressure and approach to unity of reading of the two thermometers, there is a mean temperature above 45° and under 55° E. (e) "\'\^ien the wind is south or south-west. Dr. A Hewsoii has published ^ the results of the observations made in the Pennsylvanian Hospital by the surgeons, on the relation between certain meteorological ' Pennsylvanian Hospital RcTports, voL ii. 1869. OR RETAED CERTAIN DISEASES 383 conditions and the mortality after surgical operations. They agree in the main with the conclusions of Dr. Richardson, and elicit the additional fact that death from surgical " shock " is associated with a high barometrical pressure and a dry air, conditions opposite to those accompanying fatal pyaemia. Dr. Hewson writes, " We obtained a mortality, when the operation was performed with the barometer ascending, of 10 "7 per cent, of 20 '6 per cent with it stationary, and 28*4 per cent with it descending." French surgeons seem disinclined to operate during the hot and sultry days of summer, fearing secondary hsemorrhage and septicaemia. Eoux, who operated on a large number of cataracts, reserved the operations until spring. 2. Small2wx has been found by Dr. Ballard^ in London, smaiipox. and by Dr. Wistrand in Sweden (in which country there is a registration of disease), to prevail more from November to May than from May to November. The former physician noticed that it has assumed an epidemic form soon after the mean temperature of the air has persistently fallen below 50° for the winter season, and has begun to decline in May, when the mean temperature of the air be- gins to rise above this line, and gives place to higher temperatures. The curve for smallpox in London for a period of Smallpox — -for all Ages and both Sexes. +50 p. ct, lean Line, ^ Medical Times and Gazette, March 11 and 13, 1871. 384 METEOROLOGICAL CONDITIONS WHICH FAVOUR thirty years (1845 to 1874), represented in Mr. Alexander Buchan's and Dr, A. Mitchell's interesting research on The Influence of Weather on Mortality from Different Diseases and at Different Ages, endorses these views. The dotted line represents the mortality from which that of the abnormally high epidemic of 1870-72 has been withdrawn. This abstraction has simply reduced the sensitiveness of the curve. The straight black line in this and in the following figures containing curves, indicates the mean weekly death-rate on an average of 52 weeks. The curve, as it rises above and falls below the straight black line, represents the average death-rate of each week, calculated in percentages of the mean weekly death-rate for the whole year. Dr. Moore has confirmed these observations in Dublin, where a well-marked tendency to an epidemic was noticed in March 1871 ; but the disease appeared to be kept in check by the increasing temperature, notwithstanding the importation from England of many cases, until, with the advancing autumn it blazed into an epidemic. He has also noticed^ that abundant rainfalls seemed to be followed by remissions in the severity of the epidemic, and that the acme of the epidemic closely followed a period of comparatively dry weather and lower humidity. 3. Measles. — Sydenham, in his medical observations, states that cases of measles are generally most numerous towards the end of March, and that they then gradually decline in number and disappear by midsummer. The observations of Dr. Eansome and Mr. Gr. V. Vernon would indicate roughly that measles increases with a fall and diminishes with a rise of temperature ;^ that barometric pressure fluctuates more when it is prevalent than when 1 Manual of Puhlic Health for Ireland. 2 "On the Influence of Atmospheric Changes upon Disease." — Proc. Lit. Phil. Soc, Manchester, vol. i. Series 3, 1859 to 1860. OE EETARD CEETAIN DISEASES 385 it is not rife ; and that the period of its recurrence is about every five or six years.^ This disease, which prevails especially during the spring and summer quarters of the year, would seem, according to the observations of Drs. Moore,^ Ballard,^ and others, to be unfavourably influenced by a temperature of the air above 60° in summer, and to be checked by a fall of temperature during winter below 42°. Its mortality is governed by other influences than those of a meteorological nature. Cceteris paribus, measles would seem to be more destructive amongst those who live in total disregard of all hygienic rules than amongst those who obey the laws of health, and to be more fatal to native tribes amongst whom the disease has been previously unknown. The severe epidemic in the Fiji Islands, when the disease was introduced by Europeans, affords a fresh proof of the truth of this last- mentioned statement. The measles curve, representing the fatality in London from this disease, is remarkable, according to Mr. Buchan and Dr. A. Mitchell, in showing a double maximum and minimum during the year, a rapid fluctuation taking place from Christmas to the Measles — -for all Ages and hoth Sexes. Jan. Feb. p. ct. n I I 111 an Line. March April 1 I I I III p. ct. LI Fig. 4-2 ^ "Epidemic Cj'cles." — Brit. Med. Journal, September 1, 1877. ^ Op. cit. ^ Eleventh Eeport of the Medical Officer of the Privy Council, 1S6S, No. 3, pp. 54-62. 2 C 386 METEOROLOGICAL CONDITIONS WHICH FAVOUR Whooping- Cough. middle of February, when the weekly deaths fall frora 42 to 21. 4. WJioojnng - Cough. — Extreraes of heat and cold appear to affect not only the prevalence of this disease, but much more so its mortality. It generally seems to progress hand in hand with measles, increasing viith. a falling and diminishing with a rising temperature. During the hot weather of summer it is rarely heard of; and during the period when the cold, dry, east winds blow in spring, it is generally most fatal amongst the insufficiently clothed and ill-fed. We usually regard it as a winter and early spring disease. Dr. Moore thinks that intense cold checks the disease, whilst moderate cold favours its spread. The London curve for thirty years agrees pretty closely with these views. Whooping-Cough — for all Ages and loth Sexes. London. Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. + 50 p. ct. -40 p. ct Fig. 43. The investigation made by Mr. A. Buchan and Dr. A. Mitchell into the mortality of Xew York,^ conducted on ^ " The Influence of 'Weather on Mortality of Kew York from different diseases and at different ages." — -Journal Scottish Meteorological Society, Xew Series, vol. v., Xos. xlix-lxiii., p. 171, 1880. OR EETARD CERTAIN DISEASES 187 the same lines as that respecting London, shows that the chief maximum of the curve of New York is almost coincident with the minimum of London. 5. Scarlet Fever. — Sydenham considered that this disease seariet appears most frequently towards the end of summer. Fever. 1 ft > ■o c g g 1 o > F. u. F. u. Temperature. Humidity. Pressure. Authority. Moderately low. Above the aver- age. Excessive. Sudden fluc- tuatifins. Diminished pressure. Dr. Ransome. Between 56° and 60°. Fall of mean temperature below 53° tends to arrest disease. Not above S6, or much less tlian 74. Dr. Ballard. F. u. A temperature higher than 44-6. A temperature below 44'0. If humidity of air is less tlian usual. Dr. Tripe. F. u. When it rises much above 50°. A fall of mean temperature below 50° in autumn. Dr. Moore. F. Mortality greater in dry „„ ^ „* «■ than wet I^^. Longstaff. season. The Eegistrar-General of England has noted a tendency in the mortality from this disease to increase in London during the last six months of the year, attaining a maximum in December. Dr. Moore has observed it always to be most prevalent and fatal in Dublin during the last quarter of the year. Dr. Wistrand considers that this disease is most abundant in Sweden in Novem- ber, and least so in August. The habits of the people have much to do, doubtless, 388 METEOEOLOGICAL CONDITIONS WHICH FAYOUK . witli tlie particular time of the year when the maximum of the disease appears. My own experience teaches me that it increases with a rising temperature, spreading like wild- fire in very hot weather in agricultural villages, during the times when cliildren congregate together, as, for example, during hay-making, pea-picking, gleaning, hop-picking, and school fetes ; and that this highly infectious disease spreads in towns and cities in very cold weather amongst the poor, who with their scanty supplies of fuel, huddle together for mutual warmth, diligently closing every chink whereby fresh air might possibly enter their overcrowded dwellings. Scarlatina — for all Ages and hotJi Sexes. LONDOX. Jan. Fel). March April May June July Aug. Sept. +70 p. ct. pi I ' Ml MM Ml III I I I I 1 I I III II I I Mean Line. ■50p. ct. U I I Ml I II I Ml 111 II 1 I III ill Mil III III ill The curve of ]^ew York may be roughly described as the opposite of that of London : — New York. +40 p. ct. Mean Line, ■ 60 p. ct. -1 1 1 jj^ II 1 1 >W- ■^sLL 1 II 1 i 1 1 1 1 1 MM 1 11 1 1 1 mm: - ^-^^ - N ^ ^ — li i 1 1 i 1 MM 1 1 1 1 1 1 1 n i 11 Mi •^rrr 1 1 1 , 1 i M 1 il Fig . 44. The thirty years' curve for London would, according to Mr. A. Buchan and Dr. A. Mitchell, show the maximum death-rate to occur from the beginnino- of October to the end of November (when the mean tem- perature of the air of London is 48-2, and its relative humidity is 85), and the minimimi to be in March, April, OR RETARD CERTAIN DISEASES 389 and May (during which months tlie mean tempera- ture of the air of London is 4 7 '3, and its relative humidity is 77). The curves of whooping-cough and scarlet fever form striking contrasts in the case of London, the maximum for whooping-cough and the minimum for scarlet fever both occurring in spring ; whilst whooping-cough reaches its minimum in autumn, when scarlet fever is at its maximum. This conspicuous difference does not, however, obtain in the case of K'ew York. As to the cycle of scarlet fever, Dr. Eansome has noted ^ that a small wave has appeared about every five years, and a great wave every fifteen or twenty years. ( Typhus. 6. Fever. — < Enteric. ( Intermittent and continued. Typlius, according to most observers, is only indirectly TypJms influenced in its prevalence Ijy temperature. '^Vhen the weather is very cold cases are generally more numerous, Typhus — for all Ages and both Sexes. {Bloxam's Method, f Jan. Feb. Marcli April May June July Aug. Sept. +40 p. ct. n I 1 I 1 I I Mean Line. - 40 p. ct. ^ Op. cit. ^ This irethod of dealing with the percentages in laying down the curves is convenient in arriving at an approximately true average when a small number of years are available, as in the case of typhus and typhoid figures (for which diseases figures extending over six years only are obtain- able), or when few deaths occur from any particular disease, such as gout or ague. The method consists in assuming the average, for instance, of the second week of January, to be not the actual average of that week, but the average of the first, second, and third weeks ; the average of the third week is assumed to be the average of the second, third and fourth weeks, and so on. 390 METEOEOLOGICAL CONDITIONS WHICH FAVOUR because the overcrowding and the defective ventilation of the dwellings of the poor is worse than usual. The height of an epidemic has occurred in some instances during hot weather (as, for example, in Glasgow during July 1847). Mr. Buchan and Dr. A. Mitchell remark respecting the London curve, " It is probable that this curve has two maxima, the larger in the early months of the year, and the smaller in the height of summer." Enteric. — Autumn is generally considered the season par excellence for the development of this disease, hence it has been called in America " autumnal or fall fever." It would be more correct to call it a late autumn or winter- autumn fever, and diarrhoea a summer-autumn complaint. It has been noticed to be more prevalent after dry and hot summers than after those which are cool and wet. "Warm, damp weather, in autumn and winter, when there is much decomposition of vegetable matters, is favourable to an outbreak. Heavy rains, by cleansing the air and the drains, is unfavourable to its appearance, except when filth is washed by these downfalls into the wells. The London curve for typhoid fever resembles that Typhoid Fever — -for all Ages and hoth Sexes. Jan. +40 p. ct. ri I I Mean Line. Feb. I I I {Bloxam's Method. ) March April May June July Aug. Sept. Oct. I ■ 40 p. ct. for scarlet fever as to the period of its maximum death- rate, but the minima of these two diseases widely differ in character from one another. The curve of ISTew York closely resembles that of London, but rises two months earlier to its absolute maximum. OE RETARD CERTAIN DISEASES 391 Temperature— Degrees Fahr. July Aug. Sept. Oct. Nov. 1-8 8-7 10-7 12-9 New York 75-4 73-6 64-9 54-2 41-3 London (Greenwich) 63-8 63-0 59-2 51-9 42-6 •8 3-8 7-3 9-3 When the fall of temperature from one month to another is about 9 degrees in both cities, then we have the absolute maxima of " Fall Fever." Intermittent Fever = Ague. — The popular idea in aguish Ague. districts that outbursts of this disease generally occur when sudden changes of weather, from hot to cold or the reverse, take place, and especially during the prevalence of a dry east wind with a scorching hot sun, is interpreted by the knowledge that we at present possess, as to the tendency of such meteorological influences, to conduce to the congestion of the liver, the spleen, and other internal organs. ( Diarrhcea. 7. < Dysentery. ( Cholera. Diarrhcea} — Dr Eansome writes : — " A mean tempera- Diarrhaa. ture above 60 predisposes to diarrhcea when con- tinuous, causing a rapid increase in the number of cases. A temperature below 60 appears to be un- favourable to its progress." Dr. Moffat has expressed the opinion that, as regards simple diarrhoea, there is a decrease in the pressure of the ^ Great efforts have of late years been made to ascertain the mode of causation of the autumnal form of this disease, especially in children, amongst whom it produces such a large mortality, and much interest has been excited on this subject in Leicester, which seems to suffer in propor- tion to its population more than other towns in this country. Many different views prevail in the profession as to its origin. One of the most interesting is that propounded by Dr. John Shea in his Annual Report for Reading for 1880. He holds "that, when a hot and comparatively dry summer month follows a decidedly wet month, diarrhcea prevails, due to soil (telluric) and other exhalations, and that under such conditions these exhalations affect human beings, children chiefly, possibly by inducing 392 METEOROLOGICAL CONDITIONS WHICH FAVOUR air and an increase in the force of the wind on the days on which diarrhoea occurs, and to a less extent on the days after its occurrence. fermentive changes in the food and milk used by them, stored, as sucli foods and milk often are, in iinveutilated cupboards and exposed to foul eflluvia." In both 1875 and 1880, when there was much mortality from autumnal diarrhoea amongst children in and around Eeading, which could not be ascribed to the increased vegetable matter in and temperature of the Reading water supply, since it occurred partly in the rural districts outside its distribution, and which could not be due to hand feeding, which goes on much the same one year as another, there occurred the sequence above described. Dr. Shea adds, " The natural tendency that is created in hot weather and hot climates to throw an extra stress of elimination of bile on to the liver, and so induce bilious diarrhoea, must not be for- gotten." Dr. V. C. Vaughan, Professor of Physiological Chemistry to the University of Michigan, seems disposed to connect infantile diarrhoea with the production, by the growth of some micro-organism, of a poisonous alkaloid or ptomaine named tyrotoxicon, along the seam of the milk-pail, or in the rubber nipple, tube or nursing bottle. Drs. Guy and Harley say in their work on medicine : "The functions of the liver and lungs are, to a considerable extent, vicarious. The digestion and assimilation of animal diet is attended by the separation of a large quantity of hydrocarbon from the blood. If the respiratory function be sufficiently active, this is consumed in the lungs and excreted as carbonic acid and water ; but if, as in tropical climates, or in very hot weather, the respiratory function be insufficient, the hydrocarbon is separated hy the liver in the form of fatty acids of the bile. Now, in very hot weather the air per cubic foot contains necessarily less oxygen than at a lower tempera- ture, hence for each cubic foot breathed less carbon is burnt off from the lungs in hot weather than in a cooler atmosphere. Again, if with heat, the air is charged with moisture and is "steamy," the exhalation of watery vapour from both the lungs and skin is checked and thrown on to the kidneys and bowels. Both influences, excessive heat and moisture, therefore, favour diarrhoea, independently of other causes." There is a very strong popular belief in a connection between a state of weather termed ' ' thunder weather, " which is most common in autumn, and the presence of diarrhoea. The air being humid as well as hot, drains and cesspools unpleasantly obtrude themselves on the attention, because the moisture acts as a medium of convej'ance to the nerves of smell of the sewage emanations that are raised by the heat. Such weather is not only sultry and hot, but the clouds are at the same time laden with electricitj'. Absence of sunlight anol the presence of haze generally combine to form the kind of weather thus christened. The employment of fruit and vege- tables, even if fresh, during the prevalence of such weather is likely to OR RETARD CERTAIN DISEASES 393 The mortality from diarrhoea in New York is greater than in London, doubtless in consequence of its greater summer heat. The commencement of its increase is two months earlier in ISTew York, due to the increased tempera- ture of summer beginning sooner than in London. Of induce this complaint, although such a result does not usually follow a sudden invasion of a high temperature during other seasons of the }'ear. It is probable that such evidence will soon be forthcoming for the use of the profession as will conduce to a settlement of this question which has been so long suh jiidice. Dr. Ballard, in the inquiry with which he has been entnisted into the causes of autumnal diarrhoea, is engaged in investigating the temperature of the earth at 1 foot and at 4 feet in depth, and has, I learn, ascertained some curious facts with reference to the prevalence of the disease being coincident with the periods between the crossing of the readings of these earth thermometers, which I am not authorized to disclose, but which he will doubtless in due time publish. The fact, pointed out by Drs. Lewis and Cunningham ("Cholera in relation to certain Physical Phenomena ") with reference to cholera in India, that the great maximum of prevalence in April and the mini- mum in November both occur when the soil temperature at 6 feet from the surface is between 78° and 79° P., would seem to have a bearing on this question. Dr. Ballard will not, I trust, fall back upon the con- clusion that this disease is attributable to earth emanations, without a rigorous exclusion of the evidence showing the influence of temperature and alternations of temperature in its production under ceitain conditions of the human body and of climate. The compensatory interchanges between the skin and the mucous membrane of the intestinal tract are well known, but perhaps hardly sufBciently borne in mind. Sudden heat or sudden cold will p)roduce diarrhoea, and young children, amongst whom the mortality is greatest, are more influenced by such changes and are less able to withstand the impact of a severe drain on their resources of strength than adults and middle-aged individuals. "When the skin is acting freely during the hot summer months, when, as the public say, " the pores are open," any sudden chill or cessation of perspiration may, as every medical man knows, produce a determination of blood to the biliary organs (exciting an increased flow of bile) and to the intestinal tract, probably at the time irritated by decomposing milky food, or decomposing and half- digested fruit, such as plums, etc., and a flux results. On the other hand, a sudden check to the action of the skin by cold, unless followed by the glow of a reaction, may induce an attack of diarrhoea, and this flow is often welcomed as an easy way of getting rid of a catarrh. I have never, since the publication of Dr. C. F. Oldham's book, entitled What is Malaria. ? referred to on p. 234, been alloiccd by facts, that have every now and then come to my knowledge, to forget it. 394 METEOROLOGICAL CONDITIOXS WHICH FAVOUR Dijsentery, Diarrhcea, and CJiolera—for all Ages and both Sexes. Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. LM I I I I I I I I I III III I I I I III 111 1111 [ ] I 1,1 1,1 +500 p. ct + 400 +300 + 200 + 100 Mean Line. Dysentery. DiaiThcea. Cholera (2). Cholera (1). - 100 p. ct. Fig 47. all the deaths in New York from diarrhoeal affections, 69 per cent occur amongst infants under one year, 18 per cent between 1 and 2 years, and '06 per cent from 10 to 20 years. How strongly does this enormous fatality OR RETARD CERTAIN DISEASES 395 amongst infants point to the want of good milk, which should be the sole food of infancy. Dysentery. — "Dysentery," writes Dr. Eansome,-^ "seems Dysentery. to be increased by a high mean temperature and diminished by a low mean temperature, but to be influenced by varia- tions of temperature to a less extent than diarrhoea. High readings of the barometer are nearly always accom- panied by a diminished prevalence of dysentery." Cholera. — The history of past epidemics has generally choiera. taught us, with but two or three exceptions, that the mortality from this disease usually increases until September, when it reaches its maximum, after which it begins to decline. A sudden diminution in the extent of its ravages is often ushered in by some great natural cleansing process, such as a storm of wind, or heavy downfall of rain, or sudden descent of temperature diminishing decomposition of organic matters. The London curves for these diseases show the close relationship that the progress of mortality from them bears to temperature.^ The speed at which they suddenly increase during the hottest weeks of the year, and rapidly decline on the fall of the thermometer, is very striking. The dotted line. Cholera, No. 1, indicates the fatality from Asiatic Cholera. The line not dotted, Cholera, No. 2, represents simple or English cholera. The maximum and minunum of diarrhcea is seen to be a month earlier than the maximum and minimum of dysentery, Mr. Buchan and Dr. A. Mitchell point out that the four curves seem to group themselves in pairs — diarrhoea and English cholera on the one side, and dysentery and ^ 0}} cit. ^ It is stated in the Annuaire dc V Ohservatoire de Montsouris for 1886 that, during the last epidemic of cholera in Paris in 1884, the increase in the number of deaths was not accompanied by an increase of the tempera- ture ; but that the micro-organisms in the air of Paris and its neighbourhood 396 METEOROLOGICAL CONDITIONS WHICH FAVOUR Asiatic cholera wliich pass through their annual phases a month later, on the other. 8. Bronchitis, Pneumonia, and Asthma. — These diseases are greatly influenced by mean temperature. They increase in prevalence as the temperature falls, and diminish as it rises. The London curves strikingly exemplify this fact. The percentages of the mean weekly death-rate at different ages are — From Bronchitis. AGES. 1-5 I 5-20 I 20-40 I 40-60 | 60-80 Above 80 I Total. 38 61 17 34 6 From Pneumonia. 10 I 13 I 9 I 100 100 Bronchitis is thus seen to be most fatal to children under 5 years, and to the old ; whilst pneumonia, although specially fatal to children below this age, is of rare occurrence amongst the aged. The principal maximum of pneumonia in November- December, is chiefly determined by the large number of deaths amongst children under five years, whilst the secondary maximum occurs in March. Dr. "William Squire does not apparently recognize the existence of two maxima, but contends that the annual maximum were much more abundant than usual during the days when the deaths were most numerous. Dates. Bacteria pee Cub. Metre. Deatlis from Cholera. November 1884. Montsoiiris Park. Rue de Rivoli. From 1- 4 110 1200 2 „ 5- 8 190 1150 63 ,, 9-12 245 2120 349 ,, 13-16 340 1360 268 ,, 17-20 255 880 150 ,, 21-24 185 1120 76 .. 25-28 50 220 40 OR KETAED CERTAIN DISEASES 397 Bronchitis, Pneumonia, and Asthma — for all Ages and both Sexes. Jan. Feb. Marcli April May June July Aug. Sejjt. Oct. Nov. Dec. + 130 p. ct. + 1 on p. ct. Asthma. -SOp. Ct. LI I of pneumonia, unlike that of bronchitis, is always in spring. It is unwise to associate closely bronchitis and pneu- monia in their causative relations with temperature, or by so doing we become oblivious to the fact to which Dr. Longstaff has directed attention,^ that, whereas 1104 males die from bronchitis to every 1000 females, but as many as 1460 males die from pneumonia to every 1000 females, the cause of the two diseases is somewhat different. The catarrhal form of pneumonia should be distinguished from its specific form. Dr. Seibert^ has established a close relationship between the prevalence of catarrhal pneumonia and those meteorological conditions wliich favour catarrh, such as a concurrence of any two of the following factors — a low and falling temperature, an excessive and increasing humidity and high winds. The existence of an infectious form of pneumonia,^ named also " pneumonic fever," " sewer gas and pythogenic pneu- ^ " Phthisis, Bronchitis, and Pnenmonia : Are they Epidemic Diseases ?" — Contribution to Epidemiological Society of London. 2 Berl. Klin. JFochenschr., 18S6, No. 17. 3 Vide "Pythogenic Pneumonia," by Drs. Grimshaw and Moore, in Dublin Journal of Medical Science, May 1875, and Dictionary of Hygiene, p. 452. 398 METEOROLOGICAL CONDITIONS WHICH FAVOUR Phthisis Pulinonalis. monia," is now no longer a matter of doubt. Unlike ordinary pneumonia, it is an infectious disease with a period of incubation, occurring sometimes in an epidemic form, and prevalent in the warmer months of the year. 9. Phthisis Pidmonalis. — This disease destroys, on an average, 148 individuals in London every week, and its fatal assaults are directed against those in the prime of life, differing in this respect entirely from bronchitis. In New York it is the most fatal of all diseases, amounting to ^th of the total mortality. Phthisis — for all Ages and both Sexes. +30 p. ct. Mean Line. Jan. I' ' 1 Feb. 1 1 1 March 1 1 1 1 April M 1 May 1 1 1 June fill July 1 1 1 Aug. 1 1 1 Sept. 1 1 1 1 Oct. 1 1 1 Kov. 1 1 1 Dee. 1 11 r - 30 p. ct. J 1 1 1 1 i 1 1 1 1 1 1 i 1 1 1 II 11 1 1 1 1 1 1 II 11 1 1 1 i 1 1 M 1 il Diphtheria. \{) Di-phthevia. — There is a close correspondence be- tween the diphtheria curves of London and New York, and between both of these curves and the scarlatina curve of London. The influence of cold and the season of the year on diphtheria is recognized by medical practitioners. According to my experience, which extends back to 1856, the damp, cold days of November, and the dry, cold days of the early months of the year, have been most prolific in cases. Dr. Thursfield's "Table of Deaths," ^ from 1870 to 1877 inclusive, yields the following averages : — Quarter of the Year. Deaths. Jlean Temperature. Rainfall in inches. First . Second . Third . Fourth . 735 678 547 750 40-5 52-5 60-6 43-7 5 4-5 70 7-5 Lancet, August 3, 1878. OK RETARD CERTAIN DISEASES 399 The question which requires elucidation is, as to what influence (if any) is exerted by the amount of moisture in the air on the development of the diphtheritic micro-organism. The virus of this disease seems to be communicated from one to another, if not by actual con- tact (as by kissing and otherwise), through the medium of foul air, foul water, or foul milk. 11. Sydroplwlia. — The hot "dog days" of summer Hydro- are generally considered to be those during which this^^^°^'^" disease is most prevalent, and this ancient belief is justified to some extent by facts, although we must remember that it shows itself to be independent in its spread of a high temperature, as the following curve of the mortality in London during 30 years proves: — Hydrophobia — -fo^' all Ages and both Sexes. Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. 5 cases 4 „ 3 „ 2 „ 1 ,, 11 I I I [ I 1 1 1 1 I BH I I I I i I I I 1 r Fig. 50. The number of cases in December is there seen to be as numerous as those in August. More persons are doubtless bitten by dogs in hot weather, because dogs are more irritable during this season. We want an answer to the query as to the percentage of cases of hydrophobia in those who are bitten in each month of the year, before we can determine with certainty the influence of meteorological conditions on the disease. 12. Erysipelas and Puerperal Fever. — The curves of Erysipelas. mortality for 30 years in London from these two diseases wonderfully resemble each other, and are highly suggestive of a more intimate relationship between them than is generally conceded. 400 METEOROLOGICAL CONDITIONS WHICH FAVOUR Erysipelas — for all Ages and both Sexes. Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. ^^ - 40 p. ct Fig. 51. Puerperal Fever. Puerjjeral Fever or Metria — for all Ages. {Bloxam's Method. ) Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. +50 p. ct. n I - 50 p. ct. D I i J I I I 1 I I I 111 III II I I III 111 II 1 I III III Fig. 52. Insanity. 13. Insanity. — The London curves for diseases of the nervous system are interesting. Tliat of insanity may be taken as a sample of the others. Insanity — for all Ages and both Sexes. (Bloxctm's Method. ) Jan. Feb. March April May June July Aug. Sept. Oct. Nov. +40 p. ct. Ul I Mean Line. Dec. I I -40p. ct. D I I Ml III I III II Fig. 53. This curve shows three maxima, tlie largest being in December and January, the next in June, and the least marked in March and April. The New York curve for "All nervous diseases" exhibits a considerable maximum in July — the hottest month of the year — owing no doubt to fatal cases of sunstroke. OR RETARD CERTAIN DISEASES 401 14. Rheumatism. — Eheumatic fever was said byRiieum Sydenham to be most common during the autumn. The '^"' London curve does not confirm his view. Rheumatism — for all Ages and both Sexes. Jan. Feb. +40 p. ct. n Mean Line. - 40 p. ct. March I I I I Dec. Sub-acute rheumatic affections of joints would seem to be more uncomfortable to their possessors when the barometer is low, and the air is warm and moist, and chronic cold rheumatic affections of the aged, in whom the skin is inactive, are apparently benefited by this " muggy " condition of the air. Both kinds of rheumatic joints are incommoded by a sudden diminution of pressure and perhaps by a low atmospheric pressure (vide page 374). The curve of pericarditis is very similar to that ofpericai rheumatism, as every medical man would of course ^^*'^' conjecture. Dr. Longstaff and Messrs. Bnchan and Mitchell all state that the curve of pleurisy resembles more closely that of rheumatism than that of the re- spiratory diseases — a circumstance which strengthens my belief in the existence of an etiological relation between rheumatism and pleurisy. Before concluding this sketch of the influence of meteorological conditions on mortality, it would be in- structive to consider briefly: — (1) The influence of weather on the mortality at different ages ; and (2) The influence of weather on the mortality of the two sexes. " The broad fact which the following diagrams (fig. 5 5 Mortal and fig. 56) disclose is," as has been stated by Mr. Buchan 2 D at diffe ages. 402 METEOROLOGICAL CONDITIONS WHICH FAVOUE and Dr. A, Mitchell, "that the New York curve receives its leading characteristics from a great fatality there of diseases which have their maxima as causes of death in the hot months (diseases of the abdominal organs), and that the London curve receives its form from a compara- tively lower fatahty of such diseases, and a comparatively Mortality at different Ages, for loth Sexes and all Causes. London. Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. Ill iiiiMii Ml rii irii III iiiinirrin iTrriri! higher fatahty of the diseases wliich have their maxima as causes of death in the winter and spring months (diseases of the respiratory organs and of the nervous centres)." The deaths from respiratory diseases during the winter and spring months in London are shown, by the maintained excessive height of the respiratory diseases curve at those seasons, to be enormous in young children. The major part of this winter mortality arises from OR RETAED CERTAIN DISEASES 403 diseases of the respiratory organs. This excess in our insular climate over that of the much drier continental climate of New York must be ascribed to the greater dampness associated with the cold, and to the greater vicissitudes of weather which we islanders experience. In December and January, when the air is most humid. Mortality at different Ages, for both Sexes and all Causes. New Yoek. Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. JJ I III ) I I I 111 III 1111 111 111 I I I I III 111 I I I I Fig. 56. the relative humidity of New York is 79, and of London 87. The annual minimum of New York is 62, and of London 72. The mortality curve at the opposite end of life, in persons upwards of 80, appears to be a very simple one, having its maximum in cold and its minimum in warm weather. The curve indicative of summer mortality from diarrhoea is seen to be somewhat affected in adults in the hotter climate of New York. Mortality of each sex. 404 METEOEOLOGICAL CONDITIONS WHICH FAVOUR The period of the year when females have a higher death-rate than males is when diseases of the respiratory organs are most fatal, and the period when females have a lower death-rate than males is when diseases of the nervous system are most fatal. Death of each Sex from all Causes — 3iales being represented by the solid line, and Females by the dotted line. Nov. Dec. II I I II Fig. 57. The curve of the mortality of each sex consists of three distinct portions, o} a? the respiratory disease mor- tality, h h the nervous disease mortality, and c the intestinal disease mortality. The respiratory disease mortality during the commencement of the year, a^, is higher than that of the end of the year, even after an allowance is made for the support afforded by the two maxuna of the nervous disease mortality. Nearly the whole of the intestinal affection mortality is created by the death of infants under one year. If we could diminish the mortality to any considerable extent from these three kinds of disease, namely, the respiratory, the nervous, and the intestinal, the curve of mortality would become very much flattened and approach in appearance the curve of old age. Here the end gene- OR RETARD CERTAIN DISEASES 405 rally comes, it would seem, from some respiratory affec- tion (fig. 58). Old Age — -for both Sexes. om age. f 50 p. ct. lean Line. -50 p. ct. Jan. Feb. 1 1 1 March Mil April 1 1 1 May 1 1 1 June 1 1 1 1 July 1 1 1 Aug. 1 1 1 Sept. MM Oct. 1 1 1 Nov. 1 1 1 Dec. Mir J 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 i 1 M 1 1 1 1 1 1 1 1 i ll Fig. 58. No more space can be allotted for the consideration of the relations of atmospheric states and conditions of the air to disease, as it is necessary to describe the mode of observing meteorological variations according to the most recent and approved methods. 9 T^ 9 PAET IV MODE OF OBSERVING THE METEOROLOGICAL STATES AND VARIATIONS IN THE CONDITION OF THE AIR In commencifig a series of meteorological observations it is necessary to know the height above the sea of the place of observation. This is readily found by making a search for the nearest bench mark of the Ordnance Survey, and ascertaining by a rough estimation, or by the help of a surveyor and his sj^irit level, the difference between the level of that bench mark and the station where our Fig. 59. instruments are exposed. As the publi- cations of the Ordnance Survey are not readily accessible, it will afford me much pleasure to give any applicant the height of any bench mark. The hours of observation that are best, if two obser- vations are taken daily, are 9 a.m. and 9 p.m. CHAPTEE XXXIII 1. THE ATMOSPHERIC PRESSURE There are three principal classes of barometers — the sarometei* syphon, the aneroid, and the cistern. The wheel baro- meter, so common in the passages and halls of houses, is an example of the first class, and is useless for all scientific purposes. The aneroid is not a thoroughly reliable instrument, unless checked frequently by means of a good mercurial barometer. It varies very much in excellence according to the skill and delicacy of work- manship bestowed on it. Fortin's cistern barometer is the instrument for the scientific man. A long strip of white porcelain, fixed to the board at the back of the scale, facilitates accuracy of reading. There are three points to be remembered in making an observation with one of these instruments, and they should be attended to in the order in which they are mentioned — Firstly. The temperature of the attached thermo- meter should be noted and recorded. Secondly. The screw at the base of the cistern should be adjusted until the point of the ivory cone visible within it meets the reflection of the same that is seen on the surface of the mercury. A piece of looking-glass placed at the back of the 408 THE ATMOSPHEEIC PRESSURE cistern is a great aid to the observer in dull weather. c 1 5 I 1^ LEVEL OF MERCURY Fig. 60. a. Interior of cistern. b. Mercury. c. Tube containing mercury. d. Ivory point fixed to top of cistern. e. Reflection of same, seen on surface of mercury. /. Screw for elevating or lowering the level of the mercury in the cistern. Thirdly. The vernier should be adjusted so that its lower horizontal edge forms a tan- o mercurial column, and not an arc to that curve. There are corrections to be considered in making barometrical observations, namely, those for index error, capacity, and capil- larity, furnished by the certificate of verifi- cation from the Kew Observatory, which should accompany every good instrument ; the correction for height above mean sea level ; and the correction for temperature. Three simple arithmetical calculations have then to be applied to every reading — {a) Correction of Kew certificate. (b) Eeduction to mean sea-level. (c) Eeduction to 32° F. FiG.61. THE ATMOSPHERIC PEESSUKE 409 Tables are published by the help of which both of Application these reductions are accomplished easily and rapidly.-^ tjo^°"o°" For example : — readings. Observed reading . . . . .28*900 Kew correctiou . , . . . — "015 28-885 Deduct temp, correction for 50° F. (attached therm.) at 28-9 or about 29 inches . . . , - -056 Reading at 32° F. . . . . . 28*829 Correction for height (350 ft.), the air being 50° F. . + -380 Observed reading corrected and reduced to 32° F. at mean sea-level . . , . . 29*209 Adie's barometers are useful instruments, in which allowances are made for the capillarity and capacity errors in their construction. There are two kinds — one adapted for a house or observatory, and the other the marine variety, which will work efficiently when exposed to the motion of the ship. In making an observation with an Adie's barometer, it is simply necessary to read the height by the help of the vernier, and apply to the observed reading the necessary corrections for height and temperature. The exact height of the column of mercury is read Mode of thus :— '"^^<^'°^- In rig. 61 the zero of the vernier is on a level with the line indicating 29^, so we record the reading as 29-50. If the zero of the vernier and the scale occupy such relative positions as are sketched in Fig. 62, we read the barometer to 1000th of an inch in this way : ^ Mr. Glaisher's and Mr. Lowe's tables are employed and may be found at the end of either of Mr. Buchan's elementary books on meteorology, or may be obtained from Messrs. Negretti and Zambra, or Messrs. Casella and Co., the meteorological instrument makers. 410 THE ATMOSPHERIC PRESSURE 1. We see that the reading is somewhere between 29 and 30, so we write down 29. D 2. We perceive that the zero of the vernier is on a level with a part of the scale somewhere between 1 and 2 tenths, counting up- wards, and that it is more than 1^ or "15, so we write down 29-15. 3. We then glance down at the sub- divisions of tenths on the scale and on the vernier, in order to discover which subdi"vdsion of the scale lies in one and the same straight line with a subdivision * on the vernier. In the accom- panying example we perceive that this takes place at the line on the vernier just above figure 3, namely, at '034, which, when added to the scale reading 29*15, equals 29*184, which we call the observed reading. With a little practice barometer read- ings to the 1000th of an inch can be taken with the greatest ease and rapidity. ' stfe o'ftet™S It i« occasionaUy desirable to ascertain and A B is the sUding whether tlic spacc above the mercurial scale or vernier. t .,.,„. -n . i column IS devoid oi air. By gently inclining a barometer, so as to allow the column of mercury to strike against the top of the tube, a sharp metallic click should be heard. If such a sound is not audible, air is present where a vacuum should exist. If the air cannot be expelled by inverting the barometer, it should be taken to an instrument maker. 3 — - 30 •5 - — - -^ ' — - % — 29 • c Fig. 62. CHAPTEE XXXIV 2. THE TEMPEEATUEE OF THE AIE The thermometers required are the folio wing : — Tiiermo- 1. The dry bulb thermometer of Mason's hygrometer,™* "^"^^^ described on page 424, furnishes the temperature of the air in the shade. 2. A mercurial maximum self -registering thermometer, for indicating the highest temperature reached by the air in the shade. I prefer the pattern made by Negretti and Zambra, but those of other makers are very good. The maximum temperature of the twenty -four hours generally occurs about 3 p.m. 3. A self-registering minimum thermometer for recording the lowest temperature of the air in the shade. Many laborious attempts have been made to manu- facture if possible mercurial minionuTn thermometers because : — (a) in spirit minimum thermometers there is a tendency to the evaporation of the spirit, and a condensation of it at a distance from the column, and to the breaking up of the column into distinct por- tions ; (b) it is desirable to employ the same fluid mercury for registering minimum temperatures as that for recording maximum and other temperatures. Casella's mercurial self-registering minunum ther- mometers are most beautiful instruments, but cannot be recommended for general use, as they require the most delicate manipulation, and they cannot, it appears, be 412 THE TEMPEEATUEE OF THE AIE made so as to stand wear and tear. I have had one in use for many years, and it has never once been deranged in its action, but it was selected from amongst many. JSTegretti and Zambra have sold for years a mercurial minimum thermometer with a bulb of very large dimensions. This firm has, I believe, unproved upon it, and patented another provided with a needle. The extra-sensitive self-register- ing spirit minimum thermometer of Casella, with a forked bulb, is an excellent instrument. If the column of spirit should happen to separate, it can be reunited by taking the thermometer in the hand farthest from the bulb, and giving it one or two sharp swings. The thermometer should then be hung in a slanting position, so as to allow the rest of the spirit still adhering to the sides of the tube to drain down to the column. If this method of restoring union is unsuccessful, gentle heat should be applied very carefully to the end of the tube where the detached portion of the spirit is lodged, so as to drive it towards the column. The minimum temperature of the twenty-four hours generally occurs some time before the sun rises. The The mean mean temperature is calculated by taking the average of the tempera- niaximum and mmimum readings, which is so near the true ture. . mean as to be practically correct. It is almost as import- its daily ant, from a public health point of view, to note the daily range range. ^j, ^g^^^g^^^^^^.g g^g ^q obscrvc the cxtrcmcs to which the tem- perature occasionally reaches. The mean daily range of temperature is obtained by deducting the average dally minimum from the average daily maximum temperatures. Theimome- The tlicrmometers which have been adverted to being employed to indicate the temperature of the air in the shade, it is necessary, if we would obtain correct informa- tion, to protect them from the sunlight, wet, etc., whilst at the same time permitting the freest access of air. Accordingly, cases, called thermometer stands, of which ter stands. THE TEMPERATURE OF THE AIR 413 there is a great variety, are employed, in which the instru- ments are suspended. There are Lawson's,^ Glaisher's,^ Martin's,^ James',^ Morris',^ Stevenson's,^ Griffith's,^ Stow's,*' Welsh's Kew standard,'^ and Pastorelli's'^ stands. The stand below depicted resembles Stow's more than the other thermometer stands, but is superior. Fig. 63. {a a a a) The uprights. If by f inch, serve for the suspension of the maximum and minimum thermometers. Fig. 64. 1 Described in Met. Mag., October 1868, p. 127. 2 Described in Met. Mag., November 1868, p. 155. 3 Described in Met. Mag., December 1868, p. 169. ^ Described in Met. Mag., December 1868, p. 170. ^ Described in Met. Mag., January 1869, p. 187. 6 Described in Met. Mag., February 1869, pp. 1, 2, 3, and 4. 7 Described in Met. Mag., March 1869, pp. 17, 18, and 19. 414 THE TEMPEKATUEE OF THE AIR Solar Maxi- mum. Fig. 65. (b) Piece of thin board J inch thick, against which Mason's hygrometer is fixed. It stands in the centre of the interior at an equal distance from the front and back of the stand. I have three of these stands, and have but one fault to find with this form, which is apparently inseparable from every thermometer stand that has yet been devised. When the rain is blown against the front or back of the stand from the north or south, the thermome- ters are liable to receive a wetting. Thermometer stands should always be fixed in an open place, far away from buildings and trees, so as to face due north, and so that the bulbs of the thermometers shall be at a distance of exactly 4 feet above the ground. 4. Solar Maximum Eadiation TJieriiiomder, — Comparative ob- servations with solar radiation thermometers have been in the past distinguished for their dis- crepancy, due in part to imper- fect construction of the instru- ment, and partly to the want of uniformity in mounting and ob- serving it. The most modern and best thermometer of this class has its bulb and one inch of its stem of a dull black. Its jacket is provided at each extremity with a platinum wire to test by the aid of a Euhmkorff's coil the degree of rarefaction of the air. If the interior of the jacket be perfectly clean, free from moisture, and sufficiently exhausted, a pale white phos- FiG. 66. i THE TEMPEKATUEE OF THE AIR 415 phorescent light, with faint stratifications and an appear- ance of transverse bands, will be visible. Mr. Stow has drawn up the following suggestions for observers, which have been almost universally adopted : — 1. Adjust the instrument 4 feet above the ground in an open space, with its bulb directed to- wards the S.E. It is necessary that the globular part of the external glass should not be in contact with, or very near to any substance, but that the air should circulate round it freely. Thus placed, its readings will be affected only by direct sunshine, and by the temperature of the air. 2. One of the most convenient ways of fixing the instrument will be to allow its stem to fit into and rest upon two little wooden collars fastened across the ends of a narrow slip of board, which is nailed in its centre upon a post, steadied by lateral supports. 3. The difference between the maxima in sun and shade is a measure of the amount of solar radiation. It has been found that solar radiation attains its maximum in most parts of the country during May, and its minimum during December, and that it is greater on the western than on the eastern side of England.-^ Fig. 67. 6. Terrestrial Minimum Thermometer. — The spirit Terrestrial self-registering minimum with a bifurcated bulb, exactly 1 Vide "Solar Radiation, 1869-74," by Rev. F. W. Stow, in Quarterly Journal of Meteorological Society, October 1874. 416 THE TEMPEEATUEE OF THE AIE similar to the minimum thermometer for shade tempera- tures, with a substitution of a jacket for protection in place of a porcelain scale and hard wood back, is an excellent instrument. This thermometer is exposed on grass which is kept closely cut, and should be surrounded by some arrange- ment for protecting it from dogs and other animals. A circular wire-fence, similar to that depicted in Fig. 68, is the best with which I am acquainted. The obscurity produced by a condensation of moisture within the jacket, and the destruction of the material em- FiG. 68. ployed for rendering apparent the di'sdsions on the stem from the same cause, have sorely troubled observers in the past. As received from the instrument maker a terrestrial minimum thermometer is generally attached to its jacket by a stuf&ng of strips of indiarubber. Many remedies have been proposed. A packing of chloride of calcium, or of putty and sealing-wax, or a bored cork painted over on its exterior with two or three layers of asphalte, or an air-tight ground joint. Some have bored a hole at the closed end of the jacket, and others have discarded the jacket altogether. I would recommend that this last-named plan be adopted, or that a bored indiarubber cork be employed, THE TEMPERATURE OF THE AIR 417 painted externally with several coats of asplialte, or that the thermometer be fitted to the jacket like a stopper to a bottle. In either case the markings on the stem should be rendered indelible, in the manner described on page 420. Every thermometer should be numbered and graduated on the stem, and should be verified by comparison with standard instruments. A special department at the Kew Observatory occupies itself with the verification of meteorological instruments, charging a small fee for the labour. No one should buy a thermometer or barometer unless it is provided with a recent certificate of the verification of the same. Proof of the Necessity for the Verification of ^z,ermo- verification meters. — The inaccuracies in the readings of thermometers, meters. which render a verification of all a necessity, are due partly to the difference in the diameter of the bore throughout their entire length, which defect appears to be inseparable from their manufacture, and partly to the tendency which thermometers have to read higher from age. It is sometimes difficult indeed to find two thermo- meters, out of a large number, that read exactly alike. Here is a certificate of verification from the Kew Observatory, which belongs to a thermometer in my possession : — 32° . 0-0 42° . 0-0 52° . . +0-1 62° . . -0-1 72° . . +0-1 N.B. — "WT:ien the sign of the correction is -f- the quantity is to be added to the observed scale reading, and when — to be subtracted from it. They may in truth be likened to human faces, for scarcely two are to be found very closely resembling one 2 E 418 THE TEMPEEATUEE OF THE AIE another. A mercurial maximum thermometer was some time ago purchased by one of my friends of each of the most eminent meteorological instrument makers. They were compared together, and all found to differ from each other in their readings. Mr. Alexander Buchan states ^ that he once compared a number of first-class high-priced thermometers, every one of which was from 1'2° to 1'7° too high. Some thermometers have been offered to the public with the assurance that " every instrument is carefully verified by a Kew standard thermometer"; which simply means a well-made thermometer that has been verified at the Kew Observatory — one, in fact, whose errors are known. A thermometer which had been thus verified and declared free from error was sent by me to this ob- servatory. The certificate returned with it contained the following corrections : — At 90° -0-2 95' 100' 105' -0-2 -0-1 -0-0 Another thermometer sent out by a difierent maker is in my possession which was "guaranteed accurate in its indications, having been compared, degTce by degTee, with a standard thermometer verified at Kew." It is about •4 of a degree in one part of the scale, and '5 in another part, higher than is correct. Here is the certificate of a third thermometer, which was supposed to be perfectly accurate before returned trom tne Hew Ubservatory : — ■ At 85° . -0-3 „ 90° . -0-4 „ 95° . -0-5 „ 100° . . -0-4 „ 105° . . . . -0-4 ^ Randy Book of ihteorology. Blackwood. 1867. THE TEMPERATURE OF THE AIR 419 It is not by any means an easy matter to verify thermometers with precision. The verification can only be satisfactorily conducted by means of instruments specially adapted for the purpose, such as are to be found in the great observatories. It should be done, moreover, with the greatest care, by men who are accustomed to the work. The following memoranda for purchasers, which were published in a paper ^ read before the British Medical Association in 1869, may be advantageously repeated: — {a) Mercurial thermometers which are two or three years old are always to be preferred. (b) No instrument should be bought without a certificate from an observatory of its recent verification. Mercurial thermometers are liable to read higher than is correct through age ; and this change especially occurs during the year or two immediately succeeding their period of construction. The bulb, ha^dng been formed by the action of heat, undergoes contraction after its manu- facture, the fibres of the glass taking some little time to assume their permanent position. Hence it has been usual amongst some makers of meteorological instruments to lay down their thermometers, like their port, for im- provement with age, before engraving the scale on their stems. " By quite a recent discovery in the manufacture of these instruments," writes one who sells thermometers, " the glass bulb of the thermometer is reduced to its ultimate degree of contraction before the stem is divided, thus obviating the necessity of keeping the tubes fiUed for the space of one or two years before dividing them, and rendering it possible to make an absolutely accurate instrument in a week" With the object of ascertaining the truth of this statement, I made a careful examination ^ " Remarks on Clinical Thermometers." — Medical Times and Gazette, October 16, 1869. meters. 420 THE TEMPERATUEE OF THE AIR of one of these thermometers, and discovered that it was incorrect. Its readings were about two-fifths of a degi'ee too high. The verification of a two or three-year old mercurial thermometer at an observatory should not be relied on as a guarantee of its perpetual accuracy. The authorities of the Kew Observatory consequently append to their certi- ficates the following, amidst other notes : — " This instru- ment ought, at some future date, to be again tested at the melting-point of ice, and if its reading at that point be found different from that now given, an appropriate cor- rection ought to be applied to all the above points." Markings of The markings on the stem of thermometers, which thermo- indicate the degrees and parts of degTees, are exceedingly apt to crumble away and disappear after but a short exposure to the air, for the reason that instrument makers do not know of a durable composition with which to form them. The markings of the divisions may be replaced by the observer in either of the following modes : — The stem of the thermometer, having been thoroughly cleansed by scrubbing it with an old tooth-brush dipped in a mixture of strong aqueous caustic soda and methy- lated spu'it in equal proportions, is washed with water and dried. Silicate of soda is mixed with water sufficient to produce a syrupy solution. A little of this fluid is mingled with some lampblack, so as to form a j)aste, which is brushed over the divisions as a coating. The ther- mometer is rolled between a flat piece of wood and a strip of cardboard, so as to remove all of the black coating from the stem except that which fills the gTooved lines of the divisions. By means of another brush dipped in the clean syi'upy solution of silicate of soda, a coating of this artificial glass is rapidly spread over the whole of the stem of the thermometer, which is then allowed to dry. Some mix with the s}Tupy solution of sodic silicate THE TEMPEKATUEE OF THE AIE 421 some common precipitated manganic dioxide, to which a little lampblack has been added. Others smear over the scale of divisions on the stem some compound of lead, converted into a paste with a solution of silicate of soda. The paste which does not fill the lines is rapidly removed by rubbing the stem of the instrument between two smooth surfaces. Tlie divisions containing the paste are then brushed over with a little ammonium sulphide, which forms with the lead the black sulphide of lead. CHAPTEE XXXV 3. THE HYGEOMETEIC CONDITION OF THE AIE Moisture of The hygTometric state of tlie air is determined by by ndi?"'^'' — ^■^^> ^^ estimation, by the help of the rain-gange, of gauge, hy- the amount of water which readies the earth in the form and"spe"tro- of rain, hail, snow, and fog; 2d, a consideration of the scope. indications of the hygrometer, an instrument for deter- mining the amount of aqueous vapour present in the air, near the surface of the earth ; and Sd, a rough estimate of the degree of development of the atmospheric lines of the solar spectrum as shown by a spectroscope. The amount of moisture in the air cannot be deter- mined by either of these instruments separately, but is exhibited by the combined information afforded by them. A month's rainfall may simply imply the amount of rain which fell on one excessively wet day, the remaining days of the month being dry and fine. The air is frequently very moist, even when no rain falls. The rainfall of New York is nearly double that of London, yet the relative humidity of the air of New York is much less than that of London. Wliilst the number of aqueous - lines in the solar spectrum between D^ and D^ at New York, corresponding with the weight in grains of aqueous vapour in each cubic foot of air, is at its minimum in January, and at its maximum in August or September, Dr. D. Draper shows that the relative humidity of New York reaches its maximum of 96 in January, instead of in August or September. THE HYGROMETRIC CONDITION OF THE AIR 42; The degree of humidity of the air is affected by many circumstances — such as direction of the wind, temperature, season of the year, distance from masses of water, and confiejuration of the land over which it lies. A Bain Gauge, quite good enough for all practical Rain Gauge. purposes, can be purchased for about half a guinea, the glass measure, which is divided into Y^^ths of an inch, being included. It should be fixed, by means of four or more wooden stakes, firmly into the ground, so that its summit is 12 inches above the surface. The farther removed the site is from buildings and trees the better. It should always be as far from a neighbouring object as that object is high. Snow should be melted be- fore it is measured. Printed directions for mak- ing observations generally ac- company these instruments. Any information as to the estimation of the rain is ^ freely given by Mr. Symons, *^'' of Camden Square, London, Rain Gauge. Fia. 69. ^^j^^ -^ ^^ ^j^^ j^^^^ ^^ ^^ rainfall registration in this country. Forms for its regis- tration may be obtained from Mr. Stanford, Charing Cross, London. Dr. Trench, the late Medical Officer of Health for Liverpool, was strongly impressed with the belief. that there is an inverse ratio between the rainfall and the amount of mortality from infantile summer diarrhoea. If this ; disease is dispersed, or rendered less virulent by an excessive rainfall, it is often superseded by catarrhal and rheumatic affections, which, although less mortal, 424 THE HYGEOMETEIC CONDITION OF THE AIE Hygro- meters. are often exceedingly intractable, and sometimes lead to serious results. The Hygrometer. — The amount of aqueous vapour present in the air is determined by instruments called hygrometers, of which there is a great variety. Eey- nault's and Mason's hygrometers are generally preferred ; but, as the working of the former instrument with ether and an aspirator is troublesome, the latter has almost entirely supplanted it in everyday practice. It consists of two verified thermometers, fixed side by side ; the bulb of one being kept always damp by a covering of muslin connected with a little reservoir of distilled water by means of a lamp wick. Great mistakes are commonly made in the adjustment of the muslin, lamp wick, and water reservoir. I have seen a hygrometer in the observatory of a Philosophical Society with the w^et bulb arranged in the mistaken manner here depicted : Mason's hygro- meter. Fig. 70. The Improper Mode. The Proper Mode. Bulbs of Mason's Hygrometers. In the first sketch the wet bulb is smothered in wet muslin, to which is attached a piece of lamp wick as large as one's little finger, whilst close below the bulb is an open vessel fuU of water. Every provision would seem to be made here for producing an artificial local dampness of air around the bulb, and for rendering it simply impossible that the thermometer should really furnish us, by indicating the temperature of an evapor- THE HYGROMETKIC COXDITION OF THE AIR 425 ating surface, with the true hygrometric state of the air in the neighbourhood. The finest musHn, which generally contains starch, should be boiled in distilled water to extract it. Lamp wick should be boiled in distilled water and a little carbonate of soda to remove all grease. The smallest thread of lamp wick that will keep the muslin per- manently damp should be employed, and the little reservoir of water should be fixed away from the bulb, so as not to create a local artificial climate. The first drawing represents the ignorant and care- less use, and the second drawing the intelligent employ- ment, of the hygrometer. The hygrometer is fixed against a thin board that occu- pies the centre of the thermometer stand. Like the other shade thermometers it should face the north. If the air is saturated with moisture there is little, if any, difference between the readings of the dry and wet bulb thermometers. The readings of the wet bulb are, as a rule, lower than those of the dry bulb thermometer. The generally accepted statement that the greater the difference between the dry and wet bulbs the less is the amount of watery vapour present in the air, requires some qualification. An increase of temperature, by expanding the air, and thus separating the particles farther from each other, increases, whilst a fall of temperature, by drawing them closer together, diminishes the capacity of the air for moisture. Air of a temperature of 57*2 dry bulb, and 51 wet bulb, with a relative humidity of 64, may contain exactly the same amount of vapour in grains per cubic foot (3 '4) as air of a temperature of 70*5 dry bulb, and 56*8 wet bulb, with a relative humidity of 42. The semi-diurnal rise of temperature is more frequently ac- companied by an increased capacity of the air to absorb moisture than an actual increase in its amount. 426 THE HYGEOMETPJC CONDITIOX OF THE AIR The relative humidity of, or percentage of, moisture in the air is afforded by reference to a table to facilitate calculation. ^ One of the best, if not the best, hygrometer for popular use, as it requires no tables and calculations, is one that was designed by Mr. Lowe of Boston, U.S., and is employed in France. It is especially adapted ^ The fullest information as to the use of Mason's hygrometer, and the calculation of the dew point, etc., is to he found in James Glaisher's Hycjromctric Tables, adapted to the dry and wet bulb thermometers. Third edition. Taylor and Francis, Fleet Street, London. The tables prepared by William Bone, which are obtainable from Negretti and Zambra, are also useful. THE HYGEOMETPJC CONDITION OF THE AIR 42 7 for the sick room, as it can be easily managed by an intelligent nurse in accordance with the instructions of the physician (fig. 71). It consists of two thermometers precisely alike, the bulb of one being dry and the other kept always moist. On the inner side of the dry bulb scale is a third scale, on which two indices move up and down. In the central portion of the lower part of the hygrometer is a screw head with a pointer attached to it. By the help of the vertical, oblique, and horizontal lines the relative humidity, dew point, and elastic force of vapour of the air may be seen at any moment at a glance. The instructions as to the mode of working the instrument are thus given in the Meteorological Magazine of December 1877 : — "(1) Eead the dry bulb thermometer, and raise the Lowe's screw head in order to set the upper index on the extra j^^^' scale at the dry bulb temperature ; (2) read the wet bulb, and turn the screw head until the lower index is at the wet bulb temperature. The extremity of the long hand will then point to {a) the relative humidity ; (&) the dew point ; and (c) the elastic force of vapour, according as one reads the vertical, oblique, or horizontal lines." The only objection to this instrument is that very common one which has already been adverted to in referring to ]\Iason's hygrometer, as to the position of the reservoir of water, etc. This defect can, of course, be easily removed. Tlie Spectroscope. — Wliilst hygrometers indicate therheSpectr degree of moisture of the air around them, the spectroscope ^*^°^^" furnishes us with a means of roughly estimating that contained in the higher regions of the atmosphere. The water lines in the solar spectrum are very numerous, especially in the red j^ortion. The principal aggregation of them forms what is known as the atmospheric zone or " rain-band," on the red side of D. In Angstrom's atlas more than 50 lines may be easily counted in this zone. 428 THE HYGROMETEIC CONDITION OF THE AIR There is a minor rain-band between & and F, which he describes as " tres forte pendant les mois d'ete," and which has been named the " Maxwell Hall's Jamaica Eain-Band." Prof. J. P. Cooke of Cambridge, Massachusetts, U.S., confin- ing his attention -^ to the study, by means of a powerful spectroscope, respecting the relation between the number of interstitial lines in the otherwise empty space bisected by the solar Nickel line between D^ and D^ (for D discloses itself as a double line under a high power), and the weight of aqueous vapour per cubic foot of air, found an augmenta- tion of their number as the weight of water gas increased from "81 to 6 '5 7 grs. per cubic foot. Prof Piazzi Smyth has often counted 1 1 or more of these water lines in this space.^ Without diving deeply into this subject by the help of powerful instruments, we shall find that much information is afforded by a practical acquaintance with a small waist- coat-pocket spectroscope, which enables the observer to study the changes in the apparent thickness of the Fraunhofer line D in the solar spectrum, and compare its size and dis- tinctness with the unchangeable lines E, b, and P, on the less refrangible, or green and violet side of the spectrum. What has been described by Prof. Piazzi Smyth as "the rain- band" is the blurred appearance on the red side of D, which becomes more or less distinct in proportion to the amount of moisture in the air and to the probability of rain falling. The line D is seen by a small spectroscope to separate the red from the yellow, and F appears to be in a position where the green merges into the violet parts of the spectrum. The degree of visibility of the fine lines in the green part of the spectrum between D and E is also worth noting, as when rain is imminent they become less distinct. On the yellow side of D are often to be seen, especially when the sun is on the horizon, " low sun-bands " which should be dis- ^ American Journal of Science, ]S'ovem'ber 1865. - The Visual Solar Sj^edrum. THE HYGROMETPJC CONDITION OF THE AIR 429 regarded in rain prediction. The line D, with the attached " rain-band/' may be compared as to its thickness and dis- tinctness with the Fraunhofer lines E, 5/ and F, forming as Red l^llcw Green, Vtcleb Fig. 72. they do three grades, or standards of comparison, a thickness equal to F showing a large excess of moisture in the air.^ 1 6 is ill reality a double line, but is seen with difficulty as such if a spec- troscope of very moderate dispersion, like that recommended, be employed. ^ When the information afforded by the spectroscope is supplemented by that given by the thermometer, the probability or otherwise of the condensation of the moisture, in the form of rain, hail, or snow, at or around the place of observation may be estimated with some approach to precision. Dr. H. E.. Mill has offered to the public the following guide, which may be useful to weather prophets. It refers to appearances pre- sented by a small Hilger's spectroscope, and the rules for prediction are based on observations made at Edinburgh. Thickness and distinctness of line D. Temperature. Prediction. le. 5 No rain. ,, Below 40° F. Possibly rain. = h 40° F. Rain. h Between 40° & 45° Probably rain. b „ 45° & 50° Probably no rain. h Above 50° No rain. gr. h, le. F . (thin lines distinct) Below 45° Probably no rain. Above 45° No rain. ;> ) J (thin lines indistinct) Below 60° Probably rain. ,, ,, )) )) Above 60° Probably no rain. =r. Pain. gr. F. . Much rain. le. signifies less than. gr. signifies greater than. Those who have not worked at the spectroscope in connection with meteorology will find information on this subject in an article entitled "Rain-band Spectroscopj'," by Professor P. Smyth, in the Transactions Scottish Meteor. Socy., Nos. 51-54, and in The Eain-bancl (Hilger, 1883), by H. R. Mill, and also in A Flea for the Rain-hand, and the Rain-hand Vindicated, by J. R. Capron, published by Stanford of Charing-Cross, 1886. CHAPTER XXXVI 4. THE DIRECTION AND STRENGTH OF THE WIND The directio7i of the wind is easily ascertained by noting the movements of the lowest stratum of clouds. The upper strata of clouds are sometimes to be seen travelling in an opposite direction to that in which the lower are moving. The strength of the wind is estimated by its velocity Anemo- or prcssurc. Instruments named anemometers are em- pressure ployed to register its velocity, and pressure plates its plates. force. The belief of meteorologists in anemometers has suffered a rude shock by the investigation made by the Eev. Fenwick Stow, on a simultaneous comparison of the behaviour of different anemometers.^ He discovered that the results were discordant, and that the indications of the only instrument which comes within the reach of the purses of most of us, namely, Robinson's cup anemometer, are very fallacious. Pressure plates are open to several objections, and are generally costly contrivances, arranged with vanes, so as to keep the surface of the plate always at right angles to the flow of the wind. The cheapest and simplest which I have seen is one ^ "On Large and Small Anemometers." — Quarterly Journal of the Meteorological Society, April 1872. THE DIRECTION AND STRENGTH OF THE WIND 431 thcat has recently been introduced by Mr. Thomas Stevenson, which can be obtained for 24s.^ A is a wood box, f inch thick, attached to the top of a stake fixed in the ground, which turns with the wind on a vertical axis. Fig. 73. & is a small disc, fixed on a light brass tube, ^ mch in diameter, which rests on two brass rollers. B is a larger disc, fixed on a light brass tube, ^ inch in diameter, which rests on two brass rollers. When acted on by the wind the brass spring >S^ is lengthened, the maximum elongation being recorded by a fine thread attached to the rod, which is pulled through a small hole in a brass plate {t) fixed to the side of the box. The rods are graduated by weights, each division corresponding to the elongation of the spring, due to a weight of 1 ounce. " To ascertain the maximum elongation that has taken place in the observer's absence, press the thread against t, then push in the disc until the part of the thread which had been drawn through the hole in t is again drawn 'taut,' and read off the result from the graduated tube." ^ Scottish Meteorological Journal, July 1874-July 1875, p. 266. 432 THE DIEECTIOX AXD STEEXGTH OF THE WIND Pressure in lbs. per sq. ft. Remarks. July 3 2-54 4 7-50 Stormy winds vrith. sudden gusts. 5 3-44 7 1-05 8 •80 31 •62 Aug. 1 1-54 2 12-00 Weather described in news- paper as a heavy gale. "When the disc is 6 inches, the factor for reducing the diAdsions (due to pressure of 1 oz.), to the stand- ard of lbs. to the sq. ft. is . '318 Do. 3 do. do. . 1-273 Do. li do. do. . 5-09 This variety of pressure gauge has been constructed for storm stations with one disc of 3 inches diameter, and the other 1^ inch, but admittmg of a 6 -inch one being put on at any time when the winds are light. One great objection to these, as to ahnost all other wind-pressure plates, is, that they only move in a horizontal line. Supposing the wind to descend upon them, or ascend towards them, in sudden gusts, they do not feel and therefore cannot register its force. Table for I havc bccn in the habit of employing the accom- roughesti- panyincT table (extracted from Buchan's Metcoroloay) for mate of force •'^ ^^ o \ <^t// of wind. many years, and think it can hardly be improved upon as a guide to the formation of a rough estimate. The scale is to 6, representing a calm, and 6 a hurricane, — a violence of wind which i-s unknown in this country. THE DIEECTIOX AND STKENGTH OF THE WIXD 433 m i s o . id*^ B ^ ""* -^ .E 3 ;_ CQ m"^ ^ '-, -*J tn w 0-0 0-00 0-0 01 0-01 1-4 0-5 0-25 7-1 1-0 1-00 14-1 1-5 2-25 21-2 2-0 4-00 28-3 2-5 6-25 35-4 Popular Designation. Calm. Lightest breath of air. Very light air. Light air. Light breeze. • Fresh , , 3-0 3-5 4-0 4-5 5-0 5-5 6-0 9-00 12-25 16-00 20-25 25-00 30-25 86-00 42-4 49-5 56-6 63-6 70-7 77-8 Popular Desiguation. j-Very fresh. 1 Blowing J hard. Blowing a gale. Violent gale. Hurricane. 2 F CHAPTEE XXXVII 5. THE ELECTEICAL STATE OF THE AIR This subject may be discussed under two heads : — (1) As to the mode of collecting atmospheric electricity ; (2) As to the mode of determining its kind, whether positive or negative, and its tension. Mode of n^ Mode of collecting atmospheric electricity. Various collection. ; / ^ ^ ^ ^ ^ ^ ^ "^ . ^ , contrivances have been employed — such as an insulated metal point ; a kite ; a pole, with an insulated pointed wire, or bundle of copper wires, or conducting ball on its summit, connected by an insulated wire with an electro- meter ; a rod with a burning fuse or match ; a copper tube, with an oil lamp always burning attached to its extremity ; an insulated can of water, with a fine dis- charging tube, dropping minute quantities of water through the air ;^ balloons with wire coverings ;^ a spirit lamp on an insulated stand ; a gas jet, so constructed that it cannot be extinguished by the wind ; etc. etc. The insulated ca,n of water is, of course, useless in frosty weather, and troublesome wdien it is desired to make observations at different places ; otherwise the water dropper is a most convenient apparatus. ^ A description of this may be found in DesdmneVs Natural Philosophy, by Professor Everett, part iii. p. 604. ^ Noicveau ProcMi pour Etudier Villectricite AtmospMrique, by M. Monnet. Published by the Societe des Sciences Industrielles de Lyon. THE ELECTRICAL STATE OF THE AIR 435 Sir Wm. Thompson employs for travelling, in connection with his portable electrometer, blotting paper steeped in a solution of nitrate of lead, dried, and rolled into matches, which are attached to a brass rod projecting from the instrument. (2) Mode of determining its kind, whether positive Determma- ,• 1 -J. J. • tionofits or negative, and its tension. kind and The electrical condition of the air has been most tension, frequently determined in the past by the employment of an electrometer, which is figured in almost every meteoro- logical work and catalogue of instruments. It therefore needs no description, beyond stating that its essential parts are gold leaves and a brass rod 2 feet long, with a lighted fusee composed of nitrate of lead to collect the electricity. As a glass rod, when rubbed, produces positive, and a stick of sealing-wax, when thus treated, negative electricity, and as all bodies similarly electrified repel each other, whilst those oppositely electrified attract one another, the custom has been in employing this instrument to apply the excited sticks in turn, in order to ascertain the kind of electricity with which the gold leaves diverge. It will indicate the pres- ence of the electric fluid on almost any fine night, and will show by the aid of the rod of glass or wax the positive or negative character of it, but the intensity of the same is not referable to any accurate scale. It is now almost abandoned for investigations as to the electrical condition of the atmosphere. The only instruments with wliich I am acquainted that are of any service in these delicate investigations as to the nature and tension of atmospheric electricity are Sir William Thompson's portable electrometer,^ Messrs. Elliott and Co.'s modification of Thompson's quadrant electrometer, ^ Obtainable in tbis country from James White of Glasgow. 436 THE ELECTEICAL STATE OF THE AIR Peltier's electrometer,-^ Lament's electrometer, and Palmieri's electrometer. Thompson's portable electrometer is easily managed, but if it is once out of order, or has been neglected, is almost hopelessly ruined. Its price is £10 :10s. Elliott and Co.'s modification of Thompson's TJ2e~Wctter J) roppi7/ff Collector I I VC E Fig. 74. A. The needle with min'or. B. The Leyden jar. C. Electrode in commnnication ■with body to be tested. C Electrode in connection with the earth. D. Copper vessel containing water. E. Brass pipe, with tap, tapered to discharging orifice. P. Glass stem. G G. Pumice moistened with sulphuric acid. H H. Brass case lined with gutta-percha. 1 1. Section of wall. quadrant electrometer is not at all portable, but is cheaper, being £5 : 5s. It requires a collector which, if an insulated can of water, costs an extra three guineas. Some excellent drawings of the former or the portable instrument are to be found in Noad's Students' Text -Booh of Medricity, pages 466 and 467, and in DeschctneV s Natural Philosophy, by Professor Everett, part iii. page 593. The latter has nowhere, to my knowledge, in conjunction with the in- 1 Both, obtainable from Messrs. Elliott and Co., 112 St. Martin's Lane London. THE ELECTRICAL STATE OF THE AIR 437 sulatecl can of water collector, been delineated. Peltier's electrometer has been employed for more than thirty years at Brussels by M. Quetelet, and is described in the Annuaire Meieorologique de France, 1850, page 181. Palmieri's electrometer is hardly known in this country, but is valued in Italy, Austria, and France. M. Branly's modification of Thompson's electrometer is also employed by the French. The Medical Officer of Health who contemplates making a special study of this subject — and it affords in relation to health and disease a boundless field for research, which has up to the present time been scarcely cultivated — would do well to acquire a practical familiarity with the principal electroscopes, electrometers, and distinguishers that have been at various times in use. He will find the works of Saussure and Schiibler, of Quetelet,^ Lament,^ Duprez, Thompson's reprint of papers on electrostatics and magnetism, and the bulletins of the Observatories of Kew and Greenwich, of service. They contain records of the annual, seasonal, monthly, and diurnal changes in the electrical condition of the atmosphere of great value. A comparison between the monthly electrical observations at different observatories in relation to the development of atmospheric ozone is to be found in Ozone and Antozone, page 67, etc. M. Mascart's Traite de VElectricite is a book which will be also found useful by the student. The quality of the electricity present in the air is ascertained by observing the attraction or repulsion of the needle. If the jar is charged positively, the needle will be repelled when a positive charge is in the air, and 1 " Observations des Phenomenes Periodiques," extracted from M6moires de I'Academie Royal de Belgique, vol. xxix. "^ " Entnommen aus dem Jahresberichte der Miinchner Sternwartc, p. 72, iind aus dem vii. Bande der Annalen der K. Sternwarte zu Bogenliausen bei Miiuchen." 438 THE ELECTKICAL STATE OF THE AIE attracted hj a negative charge. It is not easy to charge the jar exactly to the same potential. To obtain accurate quantitative results from exami- nations of the electrical condition of the air requires some practice and skill. The insulated cans are constructed so as to run for twenty-four hours. It should be remembered that the proximity of houses, trees, etc., will influence the readings of the electrometer very much indeed. Medical officers of health might very fairly be excused from attempting to deal with a subject which is confessedly a very difficult one, seeing that the officials at the Kew Observatory are continually in trouble with their at- mospheric electrical apparatus, were it not that health officers are morally, if not legally, bound to neglect the study of no influence which is likely to affect the public health. Some one has said very truly that a man must be a brave one indeed who ventured in the present day to attribute any morbid or incomprehensible action to electrical influence, as the whole subject of electricity has suffered so much from the hands of the teachers of popular science. Just as the old-fashioned medical man ascribes all obscure affections to that much-abused viscus, the liver, so every phenomenon which could not be readily explained has in the past been attributed to electricity, and its first cousin, magnetism. The observations made at the Kew Observatory tend to show that the atmosphere always contains free electricity, which is positive in far the great majority of cases at a certain height above the gTOund (at 5 feet on flat ground). Out of 10,500 observations made during the years 1845-1847, only 364 showed the presence of negative electricity. In damp or rainy weather it is occasionally negative. The lowest stratum of air close to the earth's surface generally furnishes THE ELECTRICAL STATE OF THE AIR 439 negative electricity. Quetelet, who carried out a series of observations at the Observatory of Brussels from 1844 to 1848, only observed the electricity to be negative twenty-three times, and these exceptional indications either preceded or followed rain and storms. Beccaria recorded a negative state of the atmosphere only six times during a period of fifteen years. It has always been accepted as an article of belief that positive electricity, like ozone, is never to be found in a dweUing-house. We now know that both can be detected in rooms, although the latter is soon used up, unless the windows are open, or some efficient system of ventilation exists. Sir William Thompson, by means of his delicate instru- ments, has shown that either positive or negative electri- city may be carried even through narrow passages from one room to another by air. M. Palmieri, of the Vesuvian Observatory, has re- cently made some interesting experiments showing that when steam is condensed by cold, negative electricity is developed ; but that positive electricity is manifested vp'hen evaporation takes place. Registration of Meteorological Observations. There is a gi'eat variety of registers for recording Registratioi meteorological phenomena, but they do not teach the eye^^^j^g^ much, unless arranged in the form of curves. Perhaps the most useful is that represented at the end of Ozone and Antozone, or the meteorological diagram of observations made at the Kew Observatory, which appears in the Times once a w^eek. SECTION III SANITARY EXAMINATION FOOD CHAPTEE XXXVIII THE PIJEITY OF FOOD It will be observed that the 8tb Duty {vide page 4) whicli especially relates to the examination of food, simply imposes on the Medical Officer of Health the obligation, when required, of deKvering an opinion as to whether any given sample of either of the three great solid necessaries of life, namely, flour, meat, and vegetables, is or is not injurious to health. On the wholesomeness of these substances the health of the great mass of the public to a large extent depends. That teas are faced, to give them a bloom, with ferrocyanide of iron, considered by the majority of physicians to be deleterious to health ; that ales are salted to make customers more thirsty ; that nearly every sherry is plastered ; that fusel oil is a frequent accompaniment of raw spirits ; that sugar often contains iron and sand ; that preserved vegetables are frequently coloured with copper ; that lemonades, beer, and porter not uncommonly contain lead ; that tea is weighted with iron, and weakened with leaves of the thorn and other plants ; that butter is sometimes made without cream ; that coffee is adulterated with rotten figs, which have been roasted and ground to powder ;^ that ports are ^ One sample of coffee recently examined in the Paris Municipal Laboratory was reported to contain red earth, flour, cofi'ee grounds, 444 THE PURITY OF FOOD manufactured at chemical works : — are all facts which are now pretty well known to the public, who have the remedy in their own hands, in the shape of " The Sale of Food and Drugs Act" of 1875, and as amended in 1879. As none of these articles are necessaries of life, the detection of their fraudulent manipulation does not fall within the scope of the duties of the Medical Officer of Health as laid down by law, and will not therefore be dealt with in this work. It is as difficult to propound any exact definitions of wholesome and unwholesome food, as to draw a boundary line between the animal and vegetable kingdoms, for there is an almost insensible gradation of one into the other. Game, venison, and mutton which have been hung for a short time are more digestible than if eaten fresh. Cheese which is of a certain age is more palatable than when it is very new. Chinamen are said to swallow stale in preference to fresh eggs. The Esquimaux eat putrid blubber. Oysters acquire a flavour when stale, which renders them more appetizing to the gourmand than when fresh. But as a general rule, to which there are some few exceptions, it may be said that freshness is allied to wholesomeness, and staleness to unwholesome- ness in the matter of food. AUied to the great question as to the purity of food lies the extensive one : — (1) as to the proportion which the amount of flesh -forming, heat -giving, and saline ingredients bear to the health of individuals of different ages and circumstances of life ; (2) as to the amount necessary to maintain healthy life in our prisons, lunatic asylums, pauper schools, workhouses, and reformatories. caramel, talc, plumbago, vermicelli, semolina powder, bean dust, carrots, bread crusts, acorns, sawdust, red oclire, brick dust, ashes, mahogany shavings, vegetable earth, and sand. THE PUEITY OF FOOD 445 It appears that in some of tlie Cambridge Sanitary Science Examinations questions on these subjects have been introduced. As the Medical Officer of Health is inconsistently {vide 1st Duty, page 4) excluded from the medical supervision of Public Institutions, even from the Hospital for Infectious Diseases, this branch of the food question must be omitted from this handbook. CHAPTER XXXIX INSPECTION AND EXAMINATION OF ANY ANIMAL INTENDED FOR THE FOOD OF MAN Study of the The possession by the. Medical Officer of Health of some animals, knowledge of the diseases of animals is of great value to him, not only in guiding him in the formation of an opinion which may be required of him as to the whole- someness of their flesh for food, but as opening out to him a field wdiich has hitherto been barely worked, as to the relation between certain diseases of man and those of his humble associates. The writings of Gamgee, Fleming, and Wilhams will be found to be of great service to those who are engaged in the study of veterinary medicine. It is wise to take every oppor- tunity that offers of making oneself conversant with the diseases of animals, and of encouraging the performance of post-mortems in all doubtful cases. During my studies, cases of cattle plague, pleuro-pneumonia, typhoid fever in pigs, foot-and-mouth disease, splenic apoplexy and other forms of anthrax, glanders, fever of a puerperal description following parturition, ringworm, hydrophobia, distemper, etc. etc., have come under my notice. It is only for the Medical Officer of Health to look out for samples of these maladies, and many chances wHl present themselves in rural districts of making a practical ac- quaintance with them. The diseases of live stock in their relation to public EXAMINATION OF ANY ANIMAL INTENDED FOR FOOD 447 supplies of meat may be summarized in the following manner :^ — 1. Contagious Fevers. 2. Anthracic and Anthracoid Diseases. 3. Parasitic Diseases. 1. Contagious Fevees. (a) Epidemic pleuro- pneumonia, or lung fever, principally found in horned cattle. (h) Aphthous fever, or foot-and-mouth disease (murrain), which affects horned cattle, sheep, and swine. (c) Smallpox of sheep (Variola ovina). (d) Cattle plague (Einderpest, Typhus Con tagiosus). 2. Antheacic and Anthracoid Diseases = milz BEAND of German pathologists. They prevail as epidemic diseases localized in par- ticular sections of the country, and are known as — (a) Splenic fever, or apoplexy of horned cattle and sheep. (h) The braxy of sheep = splenic apoplexy. (c) The black quarter, or black leg, of horned cattle and sheep. (d) The gloss anthrax, or tongue carbuncle, of almost exclusively horned cattle. (e) The forms of anthrax which affect the mouth, pharynx, and neck in swine. (/) The apoplexy of swine and their so-called blue-sickness, or hog-cholera. (g) The parturition fever of cows, etc. ^ Vide Public Health Report of Medical Officer of Privy Council. No. 5. 1862. 448 EXAMINATION OF ANY ANIMAL INTENDED FOE FOOD 3. The Paeasitic Diseases, such as — " Measles " of the pig ; the various, chiefly visceral, diseases of stock which depend on larvae of the taenia marginata and taenia echinococcus ; the " rot " of sheep ; the lung disease in calves and lambs ; and the easily overlooked, but highly important, disease of swine, which consists of an in- festation of their muscular system by the minute immature forms of the " trichina." CHAPTEE XL INSPECTION AND EXAMINATION OF CAKCASES OF ANIMALS, MEAT AND FLESH EXPOSED FOR SALE, OR DEPOSITED FOR THE PURPOSE OF SALE, OR OF PREPARATION FOR SALE, AND INTENDED FOR THE FOOD OF MAN This section of the duties of the Medical Officer of Health as to food would seem to rank first in importance, and to comprehend a consideration of the suitability not only of the beef, mutton, lamb, veal, and pork that may be pre- pared for the food of the whole community, but the wholesomeness of those kinds of animal food which are employed by certain special classes of the people, such as game, poultry, and fish. Mr. John Gamgee expresses his belief that as much as one-fifth part of the common meat of the country — beef, veal, mutton, lamb, and pork — comes from animals which are considerably diseased. Mr. Simon, in the report already alluded to, gives the following digest of Mr. J. Gamgee's investigations, made at the request of the Government : — " Horned cattle affected with pleuro-pneumonia are much oftener than not slaughtered on account of the disease, and when slaughtered are commonly (except their lungs) eaten, and this even though the lung disease has made such progress as notably to taint the carcase ; that animals affected with foot-and-mouth disease are not often 2 G 450 INSPECTION AND EXAMINATION OF MEAT slaughtered on account of it, but, if slaughtered, are uniformly eaten ; that animals affected with anthracic and anthracoid diseases, especially swine and horned cattle, are (except their gangrenous parts) very extensively eaten ; that the presence of parasites in the flesh of an animal never influences the owner against selling it for food ; that carcases too obviously ill-conditioned for ex- posure in the butcher's shop are abundantly sent to the sausage-makers, or sometimes pickled and dried ; that specially diseased organs will often, perhaps commonly, be thrown aside, but that some sausage-makers will utilize even the most diseased organs which can be furnished them ; that the principal alternative, on a large scale, to the above - described human consumption of diseased carcases is that, in connection with some slaughtering establishments, swine (destined themselves presently to become human food) are habitually fed on the offal and scavenage of the shambles, and devour, often raw and with other abominable fllth, such diseased orsfans as are below the sausage-maker's standard of usefulness." Characters of Good and Bad Meat. The appearance and odour of good fresh meat is known to most people. The Medical Officer of Health, however, should possess a critical knowledge which may enable him to guide a sanitary authority in cases of doubt, where, from disease or otherwise, the ordinary characters of good meat are partially absent, or attended by some irregularity. The muscle of young animals is pale and moist, and that of old ones is dark-coloured. A deep purple tint is suggestive that the animal has not been slaughtered, or has been slaughtered in a dying state, or has suffered from some fever. The characters of good and bad meat are generally thus laid down. INTENDED FOR THE FOOD OF MAN 451 Good — Firm and elastic to toiicli ; marbled appear- Good. ance ; should scarcely moisten the finger ; no odour, beyond tliat pecuKar to fresh meat, which every one knows ; upon standing, a small quantity of a reddish juice oozes from it, and it becomes dry upon the surface ; marrow of bones is of a light red colour. Bad. — Wet ; sodden ; flabby ; purulent fluid in inter- Bad. muscular cellular tissue ; fat resembling jelly, or wet parchment, or exhibiting haemorrhagic spots ; sickly or putrefactive odour ; on standing it becomes wet ; marrow of bones of a brownish colour, sometimes with black spots. It should be remembered that meat may not reach the standard of good meat and yet be perfectly wholesome, so difficult is it to lay down rules to which there shall be no exceptions ; for example, a perfectly fresh leg of mutton is tough and by no means pleasant eating. If kept until it begins to lose some of the characters above enumerated as indicating good meat, which may be a long time if the weather be cold, and especially if the air be dry, it is tender and digestible. If an opinion cannot readily be formed, the lungs and their coverings, the liver, brain, and other viscera of the suspected animal should be carefully examined. Signs of inflammation are to be found in the lungs and pleura ; hydatids may be present in the brain and liver. The condition of the mouth, stomach, and intestines should be examined, if there is a probability of rinderpest, and that of the feet, teats, and mouth when there is a suspicion of aphthous fever. There never can be any doubt as to the propriety of condemning meat that has become putrid, for it produces violent gastro -intestinal disturbance, until the offending matter has been removed either by vomiting or purging. Numerous cases are to be found in medical records of fatal results following the ingestion of animal substances in a state of advanced putrefaction. Certain kinds of 452 INSPECTION AND EXAMINATION OF MEAT meat whicli will not " keep " well readily undergo some change which results in the formation of a poison that will produce violent gastro-intestinal disturbance. Veal in the form of a pie, if placed aside in a warm cupboard, will often when consumed produce such unpleasant effects. If, on cutting a cold veal pie, the jelly is found to be in a fluid state it is wise to avoid it. Certain damaged meat, such as mouldy veal, musty bacon, decaying mutton, sausages, bacon,^ pork pies, brawn,^ potted meats ^ in a state of incipient putrefaction, cheese, etc., have acted like irritant poisons, producing great nervous depression and collapse. It has been supposed that these defects are owing to the formation of a rancid fatty acid, or a poisonous organic alkaloid, or to the development of a fungus, termed Sarcina hotulina. The smell, appearance to the naked eye and under the microscope, will readily reveal the condition of meat in this state. The detection of decomposition in sausages is found to be more difficult. It has been recommended to mix the sausage with water, to boil and add freshly-prepared lime- water, when an offensive odour will be evolved if the sausages are unwholesome. The existence of an acid reaction to litmus j^aper, an unpleasant odour and a nauseous taste, are signs of their unfitness for human food. Acid, aika- Beactiou with Litmus Paper. — Good meat is acid, and neutral? therefore turns blue litmus paper to a red colour. Bad meat is alkaline or neutral, and accordingly changes red litmus paper to a blue colour, or neither the blue nor red litmus paper are altered by it. Degree of Resistance of various parts when pressed. — Degree of Resistance 1 Medical Times, March 7, 1845. • 2 British Medical Journal, May 10 and 17, 1873. ^ Medical Times and Gazette, August 5, 1854. INTENDED FOR THE FOOD OF MAN 453 Plunge a long clean knife into the flesh. In good meat the resistance is uniform ; in bad meat some parts are softer than others. Smell of Meat. — The knife after removal should besmeii. smelt. If the meat is chopped up into small portions and some hot water thrown on it, its odour can be readily determined. An unpleasant odour indicates disease, or incipient putrefactive changes. Meat which has a smell of physic is generally condemned. Loss of Weight in drying at 212° F. — Good meat, if Amount of dried for some hours on a water bath, will not lose more than 70 to 74 per cent of its weight. Bad meat will often lose 80 per cent. {Vide Pre- cautions to be adopted in estimating loss of moisture, on page 496). If there is any reason to think that an animal, the meat of which is siib Judice, has been drugged, although the appearance and smell of the meat are unobjectionable, it is sometimes necessary to cook and taste it, for the fat of a drugged animal, after cooking, has often a peculiar bitter taste. Such drugged meat sometimes creates illness. As to the meat of an animal respecting which there is any suspicion of poisoning by arsenic, antimony, or strychnine, a rough and ready test is the physiological one of giving a portion of the meat to a cat or dog, or to the butcher who is selling it, and to note if symptoms of poisoning are produced, and if so, the exact nature of the symptoms, for each of those poisons produces characteristic effects, which are fully laid down in all books on toxi- cology. Such cases of poisoning of meat are rare. Mr. Gamgee reports one^ in which an animal had been ex- cessively drugged with tartar emetic (about gij.) Of 321 persons who ate of the flesh, 107 suffered from violent 1 Fiftli Report of Medical Officer of Privy Council, 1862. 454 INSPECTION AND EXAMINATION OF MEAT gastro-intestinal disturbance, one case proving fatal. Antimony was chemically found, botli in the flesh of the ox and in the interior of the individual who died. Doses of the flesh, which were given experimentally to animals, produced signs of poisoning. The following analyses of Letheby and Eanke may prove interestmg : — Beef. Veal. Mutton. Fat Pork. Roast Meat. No dripping lost. Lean. Fat. Lean. Fat. Nitrogenous matter . 19-3 14-8 16-3 18-3 12-4 9-8 27-6 Fat . 3-6 29-8 15-8 4-9 31-1 48-9 15-45 Saline matter 5-1 4-4 4-7 4-8 3-5 2-3 2-95 Water 72-0 51-0 63-0 72-0 53-0 39-0 54-00 Tlie Prevalent Diseases of Stock in relation to the supply of Meat for Kuman Food. Theoretically, the meat of the healthiest animals that have been slaughtered is alone fit for the food of man. Practically, meat that has been obtained from sickly and even diseased animals has been eaten with impunity, and no proof has been afforded that such meat has always been injurious to health, although abundant evidence is on record which shows the occasional evil results of its consumption. To understand this fact, which has been deemed incomprehensible, it is necessary to make a distinction between the diseases from which our stock suffers, and between the meat furnished by animals at different stages of these diseases. Pleuro- pneumonia. 1. Contagious Fevers. Hie Epidemic Pleuro- Pneumonia of Cattle is an infectious disease, the poison of which is eliminated INTENDED FOR THE FOOD OF MAN 455 through the hmgs. The appearance of the lungs and pleura is similar to that presented in a post-mortem of pleuro-pneumonia in the human subject, with which every medical man is acquainted. The divergence of opinion that has prevailed in the medical profession as to what is and what is not wholesome meat, has expressed itself chiefly in connection with the flesh of pleuro-pneumonic cattle. Some would condemn meat that exhibited evidence of perverted nutrition far short indeed of actual disease, whilst others would allow unsound meat to be eaten unless it exhibited such signs of disease as to excite disgust in the consumer. These are the two extremes of opinion, and both parties have much to urge in support of their opposite views. These unfortunate differences have led to great variations in practice, meat in precisely the same condition being confiscated in one part of London, for example, wliich is permitted to be eaten in another part. They have led also cattle-dealers, farriers, and other interested individuals, to rebel against the opinion of scientific medical officers of health, of which we had an instance some years ago in Dublin. In September 1877 the Public Health Committee of the Corporation of this city addressed a circular letter, at the suggestion of the Medical Officer of Health, Dr. Cameron, to a great number of medical men in the United Kingdom, including medical officers of health, and to veterinarians, containing the following queries : — 1. Do you consider the flesh of oxen killed whilst suffering from contagious pleuro-pneumonia fit for food for man ? 2. If you consider that such flesh may be used under certain circumstances, please state whether or not it is fit for food in the second stage of the disease, in which the lungs are usually much increased in 456 INSPECTION AND EXAMINATION OF MEAT size, partially hepatized, and sometimes more or less infiltrated with pus ? 290 replied that under no circumstances should pleuro-pneumonic beef be used as food by man; 45 stated that it might be used in the early stage, but, with two exceptions, they believed it to be unwholesome in the advanced stages of the disease.^ It should be recorded that Loiset affirms^ that during nineteen years 18,000 oxen affected with pleuro-pneu- monia were killed and used as food by the 150,000 inhabitants of Lille, or nearly 1000 carcases every year, without any apparent injury to them. Other authorities have made similar observations as to its innocuous character.^ My own opinion is that, until it can be shown that the meat of animals in the congestive and inflammatory stages of the disease is deleterious to health, a Medical Officer of Health has no right to have it destroyed. I could not, however, sanction the employment of the meat of an animal that had reached the suppurative and advanced stages of the disease. Foot-and- Foot - cmd - Moivtli Diseccsc. — Although this specific Disease. cruptivc fcvcr, wliicli ruus a definite course and is accompanied by eruptions in the mouth, on the teats, and on the feet, is rarely fatal, it has created greater ravages, and has caused a more heavy loss than cattle plague. Mr. Vacher, who has made a special study of the diseases of animals, says of it:* "The eruption consists of blisters which leave, if they break, bare red spots like small ulcers. After they dry up, crusts form. Bound the feet the contents of the blisters burrow between the soft ^ ' ' Report on the Use of Flesh of Animals affected with Contagious Pleuro-Pueumonia as Food for Man," by Dr. C. A. Cameron. ^ Reynal's Trait6 de la Police Sanitaire. s "Report to Board of Trade," by Dr. Greenhow, 1857. * Sanitary Eecord, October 15, 1885. INTENDED FOR THE FOOD OF IIAN 457 parts and hoof wliicli is sometimes shed. Occasionally (especially in sheep) no regular blisters occur on the feet, but the skin becomes red and swollen, and exudes a thick, gummy fluid. The head, feet and udder should be seized. When the eruption has extended into the in- testines, as is not infrequent with calves suckled from a diseased udder, or when there is much inflammation and abscesses, the carcase should be condemned." The loss of milk, the abortion of cows in calf, the loss of time and produce, interferes greatly with the meat -producing powers of the country. One of the witnesses before the Select Committee of the House of Commons in 1 8 7 3 stated that in 1 8 7 2 the country lost £12,000,000 from foot-and-mouth disease alone. There is no evidence on record to show that the flesh of cattle and sheep affected with this disease has injured health, although it is generally pale, flabby, and unduly moist. It is an undoubted fact, however, that the milk of these animals has produced "sore" or "festered" mouths, especially amongst children {vide page 539). Smallpox of 81u&p. — Mr. Vacher states that the smaiipox of eruption at first resembles flea-bites which become solid pimples, containing a clear fluid which changes into pus, and that the wool comes off readily. The flesh of animals thus affected has an unpleasant smell, and does not possess some other of the characters of good meat, being soft, pale, and dropsical. It produces, if eaten, sickness, diarrhoea, and febrile symptoms. CattU Plaque (Einderpest). — The flesh does notcattie 1 .1 . Ill • 1 • T 1 Plague or exhibit any unhealthy appearances m this disease, unless Rinderpest, it is in an advanced stasje, when it is dark and crackles from the presence of air. In addition to indications of catarrh in the air passages, there are signs of inflamma- tion and ulceration in the intestinal canal. The patches of ulceration reminded me, in some post-mortems made under 458 INSPECTION AND EXAMINATION OF MEAT my superintendence, of the ulcers in enteric fever. Mr. Vacher refers to the existence of an eruption on the back, loins, and inside of the thighs, and in the cow on the udder. When this disease ravaged Italy in 1711 the Government of Venice consulted the Faculty of Padua as to whether such flesh was unwholesome. The decision arrived at was that it was unattended with danger. In 1714, when the disease prevailed, no evil consequences were observed. In 1775, when the plague raged in the southern provinces of France, the flesh of diseased animals was consumed by three-fourths of the inhabitants, and no instance of inconvenience was recorded (Fleming). This author also informs us that the same freedom from any injurious effects was noticed at Hong-Kong, in China, in 1860. During the invasion by rinderpest of this country, in 1865-67, there can be no question but that a vast quantity of animals suffering from this disease were consumed as food, and loe, as medical men, are unable to prove that any great injury resulted to the public. The meat thus employed was doubtless that of animals in the early stage of the disease. If such meat is consumed the greatest precautions should be taken as to thorough cooking. It is a matter of doubt whether the flesh of an animal in the advanced stages can be eaten with safety. 2. Anthracic and Anthracoid Diseases, etc. Splenic S^pUnic FevcT or Apoplexy. — The memoranda of Mr. Apoplexy. Vaclicr respecting this disease, which sometimes assumes the form of apoplexy, are : — " Meat dark, often dropsical ; whole carcase is bile stained; liver generally enlarged and softened ; lungs generally inflamed ; increase of weight of spleen, with rounded edges, in an ox from 3 lbs. to 7 lbs. or 10 lbs., and in sheep from 2 or 3 oz. to 5 or 6 oz." Great differences of opinion have prevailed as to whether animals thus diseased should be used as human food. INTENDED FOE THE FOOD OF MAN 459 Large quantities of this meat liave been eaten, and with apparently no injurious effects ; but so many disastrous occurrences have followed its employment as to warrant the Medical Officer of Health in condemning such meat. The poison of this diseased meat resembles some others in acting with greater virulency when inserted sub- cutaneously than when taken into the stomach. A butcher cuts his hand in dressing an animal that has suffered from this disease, and rapidly dies of septicsemia. A carrier was packing some of this diseased meat for the London market, and a splinter of bone entered his hand. Phlegmonous erysipelas, which ended speedily in blood-poisoning, terminated his life in a few hours. A man was engaged during a dark night in resur- rectionizing a diseased animal that had been buried. He hoisted some of the meat in a sack over his back, which was covered by his shirt alone. In some way or other the juices of the meat passed through the sack and shirt, and came into contact with the skin of the back, on which there was probably some abrasion. Erysipelatous inflammation of the skin, attended with intense depression of the vital powers, rapidly set in, and the man expired. The dust from the wool and hair of animals that have died of this disease is often inhaled by the sorters, packers, and cleaners of the same, and becomes the medium for the conveyance of the poison. " Woolsorters' disease" has been proved to be due to a specific organism, named the bacillus anthracis, which is abundant in the blood and tissues of the diseased. M. Pasteur has so attenuated by cultivation the virus of splenic fever as to have been able to produce a benign and mitigated kind, protective against the deadly form. He believes that these bacilli are conveyed by earthworms from a buried carcase to the surface, thus propagating it to animals who are grazing above. 460 INSPECTION AND EXAMINATION OF MEAT I cannot think that meat containing such a deadly poison should ever be sold to the public. Anthrax, Antkrax, Mack Quarter, Gloss Anthrax. — The literature Elack ^ ' Quarter, and of the past tceuis with cxamples of the poisonous nature 2 grains = weight of a cubic centimetre of water at 39-2° Fahr. 1 Mo^ramme = 15432 '348 grains = 1000 grammes = 2-2 lbs. (Av.) Capacity, 1 cubic centimetre = 15' 4:32 grains = 16-9 minims = "06103 cubic inch. 1 litre =15 4:32 '3 4:8 grains = 1 pint 15 ozs. 2 drs. and 11 minims = 61 "027 cubic inches = 1000 cubic centimetres = 35'3 ounces =-22 gallon = -035316 cubic foot = 1000 grammes = 1,000,000 milligrammes. 1 ounce = 28'35 cubic centimetres = 1 '733 cubic inch. 1 citbie inch= 16 "4 cubic centimetres. 1 ciibic foot = 28-31 litres = 1728 cubic inches. 1 cuhic meire = 1,000,000 cubic centimetres = 1,000,000 grammes = 1,000,000,000 milligrammes = 1000 litres = 35-3 cubic feet. 1 pmi = 34'59 cubic inches. English laches. Length. 1 millimetre = -03%. 1 centimetre = '3*^, \ decimetre = 3-% 4:. 1 me«re = 39-37 = 3-28 feet. 1 Momefre = 1000 metres = 1094 yards = -62 mile = 3280 feet and 10 inches. 552 APPENDIX. Area. 1 square millimetre = "0015 square inch. 1 square centimetre = '154: square inch. 1 square metre = 154:2 Bqiiaxe inches = 10*76 square feet. JV.B. — The Latin prefix indicates division, and the Greek prefix indicates multiplication. 1 Septem = 7 grains = " decimillen." 1 Pmmd (Ay.) = 7000 grains. 1 Gallon (Imp.) =70,000 grains. 1 Decern =10 grains. •| Deci-ffallou = 3500 grains. 1 minim weighs -91 grain. 1 fluid drachm weighs 54-68 grains. \ flidd ounce, weighs 437-5 grains. INDEX Aberdeen, outbreak at, and milk, 545. "Absorbers," or " barboteurs," 319. Aeroscope, Pouchet's, 297. pump, 298. Ages, mortality at different, 402, 403. Ague and seasonal meteorology, 391. Air analysis, 219. ,, pulverization of water, method of, 322 atmospheric pressure of, 407. biological examination of, 340. carbonic acid in, 227. carbonic oxide in, 247. chemical examination of, 310. churchyard, 268. composition of, 224. compressed, therapeutic employment of, 377. continual pollution of, 246. copper in the, 343. dust in atmospheric, 294. ,, collector of Dr. Cunningham, 298. electrical state of the, 434. hygrometric state of the, 422, „ „ and health, 369. impure and respiratory diseases, 283. impurities sus^^ended in, 258. lead in the, 343. marsh, 268. microscopic examination of, 301. nitrous acid in, 357. observations in Glasgow, 318. 554 INDEX Air of our houses, 270. ,, ,, its deterioration, 273. ,, rooms, 372. ,, streets, 277. organic matter in, 232, 312. oxj^gen in, 225. peroxide of hydrogen in, 357. pressure of the, 374. purity of, 221. solid bodies in, 292. standard of pure, 285. subsoil, 267. temperature of the, 411. ,, ,, and health, 362. Avashings, 236, 314. Ammonia, 91. albuminoid, estimation of, 44. excess of in pure waters, 92. free or saline, estimation of, 40. standard solution of, 217. Animal impurities in air, 258. Animals, diseases of, 447. Anthraeic diseases and meat, 458. ,, ,, and milk, 540. Anti-cyclones, 360. Aphthous fever, 536. Apparatus, chemical, requisite, 548. steaming, 78. Arsenic in the air, 343. in the articles of the household, 261, in wall papers, 260, 344. ,, Davy's sodium amalgam test for, 347. ,, Marsh's test for, 346. Asparagus, poisonous, 486. Aspirators, 317, 319, 320. Asthma and seasonal meteorology, 396. B Bacillus Anthracis, 306. Comma-shaped, 306 Tuberculosis, 306. Bacteria in air, 307. in water, 161. of a hospital, 308 IXDEX 555 Barley, testa of grain of, 501. Barometric pressure, its determination, 407. Baryta water, store bottle for, 338. Bath chemical for condemned flesh, 485. Bench marks, 406. Biological method. Air, 340. ,, ,, "Water — Frankland's, 76. Koch's, 74. ,, ,, ,, Smith's, 75. Braxy meat, 460. Bread, adulterations of, 509. alum in, 510, 516. examination of, 508. ,, chemical, 513. ,, microscopic, 509. foul and machine-made, 509. lime and magnesia compounds in, 511. sulphate of copper in, 512. Bronchitis and seasonal meteorology, 396. Brucine test for nitric acid, 109. " Bunt," in corn, 491. c Caeboxic acid in air, 240. estimation of. 328. Abney's method. 332. Household ,, 33.3. Minimetric ,, 335. Montsouris ,, Pettenkofer's ,, 329. 328. "Wanklyn's ,, 331. oxide in air, 247. test for, 252. Cattle plague and meat, 457. ,, ,, and milk, 535. Certificate of W. A. used by analysts, 214. ,, ,, ,, health officer, 213. Cesspool filth, diagnosis of, in water, 210. Chemicals requisite, 548. Chlorine, determination of the, 135. Cholera and seasonal meteorology, 395. Codfish, poisonous, 481. Coke as a fuel, 249. "Cold sp)ells," 365. Colonies, enumeration of, 84. 556 INDEX Colour test for water, 20. Copper in water, 159. Corn, examination of, 489. Cover glass preparations of water, 161. Cyclones, 359. D DAjrp Chamber, 83. Darnel gi-ass, testa of grain of, 506. Data on wliicli to form an opinion respecting a water, 195. Density of population and mortality, 223. Diarrhoea and dysenter}^, and seasonal meteorology, 391. autumnal, 392. Diphtheria and poultry, 479. and seasonal meteorology, 398. Distilled water, preparation of, 547. District standards, 196. "Drop cultures," 162. Dublin, temperature of, 362. Dust of the air, 301. Duties of medical officer of health, 4. Dysentery and seasonal meteorologj', 395. E "Eae Cockle" in corn, 490. EdinlDurgh, temperature of, 362. Electricity, atmospheric, 434. ,, ,, positive and negative, 439, ,, ,, water-dropping collector of, 436. Electrometer quadrant, 436. Enteric fever and milk, 520. ,, ,, and seasonal meteorology, 390. Ergot of rye, 490. Erysipelas and seasonal meteorologj^, 399. Excremental fdth in air, 255. FAPa>'AGEOUS foods, nutritive values of, 494. Fat of milk, estimation of, with Soxhlet's extractor, 530. Fever and seasonal meteorology, 389. surgical, 381. Fish, inspection of, 480. Fish-like odour of waters, 17. INDEX 557 Flesli, condemned, destruction of, 484. Flour, acarus farinse in, 500. alum in, 497. examination of, 493. ,, cliemical, 495. ,, microscopic, 499. ' metallic poisons in, 499. FMce in meat, 475. Food, the purity of, 443. Foot-and-mouth disease, and meat, 456. ,, ,, ,, and milk, 536. Forchammer process, an improved quantitative, 38. Franklaud and Armstrong process, 53. ,, ,, and Wanklyn processes compared, 63. Fruit and vegetables, inspection of, 486. Funnel, hot water for filtration, 77. Furnishing materials, poisonous, 261. G Game, inspection of, 478. Garget, 542. Gases, poisonous, defiling air, 257. Glasgow, observations on air in, 318. Grand val and Lajoux's process for nitric acid, 120. H Hadow-Hoesley's test for alum in bread, 517. Ham, poisonous, 477. Hardness, determination of the, 139. Hard waters, influence on health, 142. Health and extremes of temperature, 364. and low temperatures, 364. Height, corrections for, to barometric readings, 409. Heisch's test, 24. Horsley's test for nitrates and nitrites, 106. Hospitals, modern pattern, 374. Hydrophobia, and seasonal meteorology, 399. ' . Hygrometer, Lowe's, 426. Mason's, 424. Hygrometry, 422. iNCtTBATOE, 82. Indigo process for estimating nitrates, 112. 5 58 INDEX Insanity and seasonal meteorology, 400. Intermittent fever and seasonal meteorology, 391 Iron in water, 157. K "Keeping Powers " of a water, 19. Knife-grinders of Sheffield, 262. Koch's biological method for the examination of water 74. Kubel's permanganate of potash process, 27 Lamb, immature, 476. Lead in articles of the household, 262. Lead in water, 156. London, mortality of, 402, temperature of, 362. Magnesia, determination of the, 145. Measles and seasonal meteorology, 384. "Measly" meat, 468. Meat and accidents, 463. characters of good and bad, 450. diseased, arguments for and against its employment, 463, 464. ,, resurrection of, 484. Memoranda for water analysts, 185. Metallic impurities in air, 258, 343. Metals, poisonous, determination of, 154. Meteorological observations, registration of, 439. Meteorology and health, 358. seasonal and disease, 380. Metrical weights and measures, 551. Micro-organisms, 305. in London waters, 85. Microscopic examination of air, 301 . ,, ,, water, 161. Microzjmie test, 25. MUk, abnormal, 533. and aifections of mouth and throat, 544. and typhoid fever, 520. blue, 524. changes in taste and odoivr of, 525. containing tubercle bacilli, 542. INDEX 559 Milk, examination of, 520. chemical, 525. estimation of fat, 528. microscopic, 522. _ excretions and secretions of diseased animals, tainted with, o43. fever, 461. "fore," 533. of diseased animals, 535. organic impurities, contaminated with, 544. physical peculiarities of, 523. reddish, 524. scarlatina, 543. Society of Analysts, processes and standards, 52/. "whole," 533. yellow, 523. Mineral impurities in air, 258. Miners, Cornish, mortality of, 258. Mistakes of water analysts, 177. o-tTo^i Montsouris Observatory, apparatus employed at, 317, 341. observations on air at, 228, 304, 307. Mortality and density of population, 222. ,„^ ,,,0 Mortality at different ages and seasonal meteorology, 402, 403. of the sexes, > > " N Nessler reagent, 216. Neuralgia and meteorolog}^ 360. New York, mortality of, 403. Nitrates and Nitrites, qualitative examination for, 10b. „ quantitative ,, >> Hi- " ^ utility of the estimation of the, 100. Nitric acid, the Brucine test for, 109. _ the sulphophenic acid process for the estimation of, 120. Nitroo-en, as nitrates and nitrites, 95. ° ^^ ,, in different strata, 98. " " ^^ objections to estimation of, 99. " " rxiies for guidance in the estimation of, 122. Nitrous acid, the metaphenylene diamine test for, 110. the napthylaniine hydrochloride test for, 357. ", the potassium iodide and starch test for, 110. Oat, testa of grain of, 506. Odour, cucumber, of water, 18. fish-like, of water, 17. 6 INDEX Odour of different diseases, 303. Old age and seasonal meteorology, 405. Operations, time favourable and unfavourable for, 382. Opinion, formation of, as to a water, 188. Ordnance bencb marks, 406. Organic niti'ogen and carbon, 56. matter in air, 232. ,, Remsen's collector of, 321. ,, Smee's ,, 322. matter in water, 13. ,, recent or decomposing, 205. Overcrowding and disease, 282. Oxygen dissolved, estimation of, 86. process, 26. Ozone, estimation of, 349. test papers, fallacies of, 352. Ozonometry, errors of old method, 355. PaPuAFFix in drinking water, 1 7. Parturient apoplexy and meat, 461. Parturition or milk fever, and milk, 542. Peaty water, diagnosis of a, 205. ,, ,, objections to, 190. Pericarditis and seasonal meteorology, 401. Permanganate and caustic potash solution, 218. of potash process, qualitative, 26. ,, quantitative, 26. ,, ,, an improved, 38. „ , , Drs. Letheby's and Tidy's, 28. ,, „ Drs. Woods' and F. de Chaumont's, 33. Phosphates, determination of the, 150. Phthisis pulmonalis, 279, ,, ,, and seasonal meteoi'ology, 398. Plate cultivations, 81. PI euro-pneumonia and meat, 454. Pneumonia and seasonal meteorology, 396. Poisoned animals, meat of, 482. Poisonous gases, 257. Pond water, 190. Pork, poisonous, 477. Poultry, game, etc., inspection of, 478. Previous sewage contamination of water, 57. INDEX Processes of Avater analysis compared, 63. ,, ,, value of, 71. Provisions, tinned, 488. Pueri^eral fever and seasonal meteorology, 400. Putrefactive processes, defiling air, 254. Radiation, Solar, 367. Rain, albuminoid ammonia in, 239. -band, 428. guage, 423. water, 11, 207. Rainey's bodies in meat, 474. Record of analyses, 175. Eeport, preparation of, 212. Rheumatism and seasonal meteorology, 401. Rinderpest and meat, 457. and milk, 535. Rust in corn, 492. S Samples of water, collection of, 170. Sarcinte, 306. Sausages, poisonous, 477. Scarlatina and seasonal meteorology, 387. Scarlet fever and meat, 462. Sewage emanations, defiling air, 255. in water, 210. Sewer gas, pollution of water with, 137. Sexes, mortality of the, and seasonal meteorology, 404. Silver, nitrate of, standard solution of, 218. Smallpox and seasonal meteorology, 383. of sheep and meat, 457. Smell of a water, 14. "Smut" in corn, 491. Soap, standard solution of, 216. Soil, porosity of, 264. Solar radiation, 367. Solid bodies in air, 292. Solid residue, determination of, 124. ,, ,, ignition of, 128. Solutions, standard for water analysis, 216. Spectroscope in hygrometry, 427. 2 561 INDEX Splenic apoplexy and meat, 458. Standard of pure air, 224. ,, ,, water, 10. "Standards, district," 196. Starches, various kinds of, 500-505. Starch tests for nitrous acid, 110. Sterilizer, hot air, 79. steam, 78. Stoves, cast and wrought iron, 250. Sulphates, determination of the, 147. ,, ,, ,, Houzeau's process for the, 148. Surgical fever and meteorology, 381. Swine plague and meat, 462. Teeth, caries of the, 495. Temperature, corrections for, to barometric readings, 409. extremes of, 364, 379. its detei'mination, 411. management of children and, 367. Thermometer scales, conversion of, 551. solar max., 414. stands, 412. ' terrestrial min., 415. Thermometers, markings of degrees of, 420. verification of, 417. Thorp's process for estimation of nitrates, 114. ,, ,, expeditious modification of, 119. Time occupied in performing an analysis, 172. Tinned provisions, 488. Trichina spiralis and meat, 469. ,, ,, modes of detection of, 473. Tiichinosis and enteric fever, 471. Tubercular diseases and meat, 461. ,, ,, and milk, 540. Typhoid fever and meat, 462. ,, ,, and milk, 520. ,. ,, and seasonal meteorologj^, 390. Typhus fever and ,, ,, 389. u Urine in water, 209. INDEX 563 V Valuation tables, 196. Vapours, injurious, 257. Veal, immature, 476. Vegetable impurities in air, 258. Ventilation, 284, 288. absence of, 278. through walls, 287. Vibrio tritici in corn, 490. Volatile matters, amount of, in a water residue, 132. w Wall Papers, 260, 344. Wanklyn, Chapman, and Smith process, 39. Water analysis, 7. ,, comparison between processes of, 63. ,, value of processes of, 71. animal organic matter in, 203. colour of a, 20. good artesian well, 11. ,, rain, 11. ,, shallow well J 11. ,, spring, 10, 201. microscopic examination of a, 161. polluted by sewage, 210. ,, by sewer gas, 137, 206. ,, by urine, 209. suspicious, 201. vegetable organic matter in, 204. wholesomeness of a, 9. Waters, different classes of, 11, 58. Weevil in corn, 489. Wheat midge, 490. testa of grain of, 501. Whooping-cough and seasonal meteorology, 386. Wigner's, Mr., valuation table, 196. Wind, direction of the, and health, 378. ,, ,, and strength of the, 430. Woolsorters' disease, 309, 459. z Zinc in water, 159. Zymotic test, 25. Printed by R. & R. Clark, Edinhtrgh lJ^ COLUMBIA UNIVERSITY LIBRARIES This book is due on the date indicated below, or at the expiration of a definite period after the date of borrowing, as provided by the rules of the Library or by special arrange- ment with the Librarian in charge. DATE BORROWED DATE DUE DATE BORROWED DATE DUE - V^ 'A - ■-' \ *v** \ '^ " ^ '" i'-^* V » VVX rv\W^ >i '^ 1 C^ C28(i140miOO RA430 Fox A'^/J^ F83 1887 T^5 7 1