/f/4 CORNELL UNIVERSITY. ^5-/ THE THE GIFT OF ROSWELL P. FLOWER FOR THE USE OF THE N . Y. STATE VETERINARY COLLEGE 1897 Cornell University Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924001229768 WORKS OF ELLEN H. RICHARDS PUBLISHED BY JOHN WILEY & SONS 43-45 EAST I9TH ST., NEW YORK. The Cost of Living: as Modified by Sanitary Science. By Ellen H. Richards, Instructor in Sanitary Chemistry in the Massachusetts Institute of Tech- nology, I'jrao. 124 pages. Cloth. $1.00. Air, Water, and Food ; From a Sanitary Standpoint. By Kllen H. Richards, with the assistance of Alpheus G. Woodman, Instructors in Sanitary Chemistry in the Massachusetts Institute of Tech- nology. 8vo, 230 pages. Cloth. S^.oo. PUBLISHED BY HOME SCIENCE PUBLISHING CO., 485 TREMONT STREET, BOSTON, MASS. The Chemistry of Cooking and Cleaning;. By Ellen H. Richards and S. Maria Elliott. Cloth. 158 pages. Price $1.00. Pood Materials and their Adulterations. By Ellen H. Richards. Cloth. 183 pages. Price $1.00. Home Sanitation. Revised Edition. Edited by Ellen H. Richards* and Marion Talbot. Paper. 85 pages. Price 250 Plain Words about Food. Edited by Ellen H. Richards, The Rumford Leaf- lets. Illustrated. Cloth. 176 pages. Price $1.00, AIR, WATER, AND FOOD FROM A SANITARY STANDPOINT. BY ELLEN H. RICHARDS AND ALPHEUS G. WOODMAN, InsfructorT in Sanitary Chemistry, Massachusetts Institute of Technology. "These cannot be taken as sufficient ... in these times when every word spoken finds at once a ready doubter, if not an opponent. They are, however, specimens, and will serve to make comparisons in time to come." — Angus Smith, "The ideal scientific mind, therefore, must always be held in a state of balance which the slightest new evidence may change in one direction or another. It is in a constant state of skepticism, knowing full well that nothing is certain. ^^— Henry A. Rowland. FIRST EDITION. FIRST THOUSAND. NEW YORK: JOHN WILEY & SONS. London : CHAPMAN & HALL, Limited. 1901. WORKS OF ELLEN H. RICHARDS PUBLISHED BY JOHN WILEY & SONS 43-45 EAST I9TH ST., NEW YORK. The Cost of'Living as Modified by Sanitary Science. By Ellen H. Richards, Instrucior in Sanitary Chemistry in the Massachusetts Institute of Tech- nology, i-^iino. 124 pages. Cloth. $1.00. Air, Water, and Pood ; From a Sanitary Standpoint. By iiilen H. Richards, with the assistance of Alpheus G. Woodman, Instruciors in Sanitary Chemistry in the Massachusetts Institute of Tech- nology. 8vo. 230 pages. Cloth. $i.oo. PUBLISHED BY HOME SCIENCE PUBLISHING CO., 485 TREMONT STREET, BOSTON, MASS. The Chemistry of Cooking and Cleaning. By Ellen H. Richards and S. Maria Elliott. Cloth. 158 pages. Price $i.oo. Pood Materials and their Adulterations. By Ellen H. Richards. Clolh. 183 pages. Price $1.00. Home Sanitation. Revised Edition. Edited by Ellen H. Richards* and Marion Talbot. Paper. 85 pages. Price 250 Plain Words about Food. Edited by Ellen H. Richards. The Rumford Leaf- lets. Illustrated. Cloth. 176 pages. Price $i.od. AIR, WATER, AND FOOD FROM A SANITARY STANDPOINT. ELLEN H. RICHARDS AND ALPHEUS G. WOODMAN, Instructors in Sanitary Chemistry, Massachusetts Institute of Technology. "These cannot be taken as sufficient ... in these times when every word spoken finds at once a ready doubter, if not an opponent. They are, however, specimens, and will serve to make comparisons in time to come." — Angus Smith. "The ideal scientific mind, therefore, must always be held in a state of balance which the slightest new evidence may change in one direction or another. It is in a constant state of skepticism, knowing full well that nothing is certain."— Hknrv A. Rowland. FIRST EDITION. FIRST THOUSAND. NEW YORK: JOHN WILEY & SONS. London : CHAPMAN & HALL, Limited. 1901. -= ■' ■ . ' I) :> Copyright, 1900, BY ELLEN H. RICHARDS and ALPHEUS G. WOODMAN, R.S/ Vu 1 ROBERT DRUMMOND, PRINTER, NEW YORK. CONTENTS. CHAPTER PAGE I. Three Essentials of Human Existence i II. Air: Composition, Impurities, Relation to Human Life lo III. The Problem of Ventilation 19 IV. Methods of Examination 27 V. Water: Source, Properties, Solvent Power, as a Carrier. 43 VI. The Problem of Safe Water and Interpretation of Analy- ses 62 VII. Methods of Examination 82 VIII. Food in Relation to Human Life, Definition, Sources, Classes, Dietaries ' 121 IX. Adulteration AND Sophistication OF Food Materials 136 X. Methods of Food Analysis 146 Appendices, Tables, Reagents 195 b1bl10gp.aphy 213 AIR, WATER, AND FOOD. CHAPTER I. THREE ESSENTIALS OF HUMAN EXISTENCE. Air, water, and food are three essentials for healthful human life. Sanitary Chemistry deals with these three com- modities in their relation to the needs of daily existence: first, as to their normal composition; second, as to natural variations from the normal; third, as to artificial variations — those produced directly by human agency with benevolent intention, or resulting from carelessness or cupidity. A large portion of the problems of public health come under these heads, and a discussion of them in the broadest sense includes a consideration of engineering questions and of municipal finances. This, however, is beyond the scope of the present work. The following pages will deal chiefly with such portions of the subject of Sanitary Chemistry as come directly under individual control, or which require the education of indi- viduals in order to make up the mass of public opinion which shall support the city or state in carrying out sanitary measures. A notable interest in the subject of individual health as 2 AIR, WATER, AND FOOD. a means of securing the highest individual capacity both for work and for pleasure is being aroused as the application of the principles governing the evolutionary progress of other forms of living matter is seen to extend to mankind. Will power may guide human forces in most economi- cal ways, and may concentrate energy upon a focal point so- as to seem to accomplish superhuman feats, but it cannot create force out of nothing. There is a law of conservation of human energy. The human body, in order to carry on all its functions to the best advantage, especially those of the highest thought for the longest time, must be placed under the best conditions and must be supplied with clean air, safe water, and good food, and must be able to appropriate them to its use. The day is not far distant when a city will be held as responsible for the purity of the air in its school- houses, the cleanliness of the water in its reservoirs, and the rehability of the food sold in its markets as it now is for the condition of its streets and bridges. Nor will the years be many before educational institutions will be held as respon- sible for the condition of the bodies as of the minds of the pupils committed to their care; when a chair of Sanitary Science will be considered as important as a chair of Greek or Mathematics; when the competency of the food-purveyor will have as much weight with intelligent patrons as the scholarly reputation of any member of the Faculty. Within a still shorter time will catalogues call the attention of the interested public to the ventilation of college halls and dor- mitories, as well as to the exterior appearance and location. These results can be brought about only when the stu- dents themselves appreciate the possibilities of increased mental production under conditions of decreased friction, such as can be found only when the requirements of health are perfectly i^ulfilled. THREE ESSENTIALS OF HUMAN EXISTENCE. 3 Of the three essentials, air may well be considered first, although its office is to convert food already taken into heat and energy. Its exclusion only for a few minutes causes death, and in quantity used it far exceeds the other two. Again, so important is the action of air that the quality of food is of far less consequence when abundant oxygen is present, as in pure air, than when it is present in lessened quantity, as in air vitiated by foreign substances. Individual habit has much to do with the appreciation of good air, and as our knowledge of the value of an abun- dance of this substance in securing great efficiency in the human being increases, we shall be led to attach more im- portance to the sufficiency of the supply. In northern climates air is not free to all in the sense of costing nothing, for the coming of fresh air into the house means an accompaniment of cold which must be counter- acted by the consumption of fuel. A mistaken idea of econ- omy leads householders, school boards, and college trustees to limit the size of the air-ducts as well as of the rooms. It is therefore necessary to emphasize the facts which science has fully esta'blished, in order to secure the survival of the fittest of the race under the present pressure of economic conditions, which take so little account of the highest wel- fare of the human machine. Air, water, and soil are the common possessions of man- kind. It is impossible for man to use either selfishly without injury to his neighbor and without squandering his inheri- tance. Primitive man could leave a given spot when the soil became ofifensive, and neighbors were then too few to require consideration; but neither man nor beast could with impunity foul the stream for his neighbor who had rights below him. The soil is permanent; one knows where to look for it and its pollution. Air is abundant and is kept in con- 4 AIR, WATER, AND FOOD. stant motion by forces of nature beyond human control, so that, save in the neighborhood of an exceptionally offensive factory, man does not often foul the free air of heaven; it is only when he confines it within unwonted bounds that it becomes a menace. Water is the next precious commodity of the three. "Without it man dies in a few days; without it the soil is bar- ren; without it air in motion parches all vegetation and carries clouds of dust-particles; without it there is no life. As population increases it becomes necessary to collect as much of the rainfall as possible, to store it until needed, and to use it with discretion. After use it is often loaded with impurities and sent to deal death and destruction to those who require it later, and yet, in nature's plan, it is the carrier 'of the world, and rightly treated and carefully husbanded there is enough for the needs of all. Its presence or absence has been the controlling force in determining the habitations of men. In its office of carrier it not only brings nourishment in solution to the tissues of the human body, but also carries .away the refuse material. It is a cardinal principle in all sanitary reforms to get rid of that which is useless as soon as possible. Too little water allows accumulation of waste material and a clogging of the bodily drainage system. The average quantity needed daily by the human body is about three quarts. Of this a greater or less proportion fs taken in food, so that at times only from a pint to a quart need be taken in the form of water as such. Next in importance to quantity is the quality, dependent somewhat upon the uses to which it is to be put. As a rule, the moderately soft waters are the best for any purpose. For drinking purposes water must be free from dangers to health in the way of poisonous metals, decomposing matters, and disease-germs. For domestic use economy requires THREE ESSENTIALS OF HUMAN EXISTENCE. J that it should not decompose too much soap. Manufactur- ing interests require that it should not give too much scale to boilers; for agriculture there should not be too much, alkali. From the nature of things, no one family or city can have sole control of a given body of water. Those on the high- lands may have the first use of the water, which then perco- lates to a lower level and is used by the people on the slopes over and over before it reaches the sea to start again on its cycle of vapor, cloud and rain, brook and river. Al- though receiving impurities each time, there are many beneficent influences at work to overcome the evils resulting from this repeated use. That which is dissolved from one portion of earth may be deposited on another. As the plant is the scavenger of the air, withdrawing the carbon dioxide with which it would otherwise become loaded, so the water has also its plant life, purifying it and withdrawing that which would otherwise soon render it unfit for any use. Pure water is found only in the chemical laboratory; the most that can be hoped for is that human beings may secure for themselves water which is safe to drink, which will not impair the efficiency of the human machine. The importance of the third essential for human life, food, and the close interdependence of all three, may be clearly shown. Of little use is it to provide pure air and clean water if the substances eaten are noti" capable of com- bining with the oxygen of the air or of being dissolved in the water or the digestive juices; of less use still is it to par- take of substances which act as irritants and poisons on the tissues which they should nourish, and thus prevent healthful metabolism and respiratory exchange. And yet a large majority of those who have acquired some notion of the meaning and importance of pure air and 6 AIR, WATER, AND FOOD. are beginning to consider it wortli while to strive for clean water pay not the least attention to the sanitary quaHties of food; the palatable and aesthetic aspects only appeal to them. Steam-power is produced by the combustion of coal or oil. Human force is derived by releasing the stored energy of the food in the body. The delicately balanced mechanism of the human body suffers even more from friction than the most sensitive machine, and the greatest loss of potential human energy occurs through ignorance, carelessness, and reckless disregard of nature's laws in regard to food. It is necessary to know, first, what is the normal compo- sition of a given food-material. This is found by analyses of many typical samples. Second, is the sample under con- sideration normal? To answer this requires an analysis of it, and a comparison of the results with standards. If it is not normal, in what way does it depart from the standard both in healthfulness and in quality? Third, if a food-substance is normal, what are its valuable ingredients and in what pro- portions are they to be used in the daily diet? In regard to meat, milk, and fish, the sanitary aspect for the chemist resolves itself into two questions: Is the sub- stance so changed as to become a possible source of poison- ous products? Or has anything in the nature of a preserva- tive been added to it? If so, is it of a nature injurious to man? There is, however, a great range of quality in some of the most abundant foodstuffs, such as the cereals, especially in the nitrogen content. This is most important to the vege- tarian and to institutions where economy must be practised. The following variations in the composition of leading cereals will illustrate: THREE ESSENTIALS OF HUMAN EXISTENCE 7 WafBr Nitrogenous Crude CarbOr it:k,. i,h ^^^"- SubiTiance. fat. hydrates. ^'^"- -*=''• Oats, maximum 20.80 18.84 10.65 64.63 20.08 8.64 " minimum 6.21 6.00 2. 11 48.69 4.45 1.34 " American hulled. 12. ii 13.57 7.68 63.37 i-30 2.03 Corn, maximum 22.20 14.31 8.87 52.08 7.71 3.93 " minimum 4.68 5.55 1.73 72.75 0.99 0.82 One sample of wheat flour may contain 14 per cent, of nitro- genous substance, another may yield only 9. A day's ration, 500 grams, will give 70 grams of gluten, etc., in the one case and only 45' in the other. This difference of 25 grams would be a serious factor in the dietary of an institution where little additional proteid is given, and it alone might be the cause of dangerous under-nutrition. .The next step would naturally be to determine how definitely these varying percentages mean varying nutrition. To this end a study of vegetable nitrogenous products in their combination or contact with cellulose, starch, and min- eral matter is needed. Much work remains to be done before these questions can be even approximately answered. At the low cost of one cent a pound, common vegetables yield only about one-fifth as much nutriment as one cent's worth of flour, yet they contain essential elements and de- serve to be carefully studied. Dried fruits and nuts are much undervalued as articles of food, as are rice and lentils. (See table, page 130.) The discussion of food values will be found in Chapter VIII. Probably the widest field for the sanitary chemist to-day is the study of the so-called predigested foods, infant foods, " hygienic " preparations, two-minute cereals, and the count- less proprietary packages, which, designed to meet the de- mand for quick results, prove traps for the unwary. Therefore the sanitary aspect of food demands a study 8 AIR, WATER, AND FOOD. of normal food and food value even more than of adulterants or of poisonous food, ptomaines and toxines. The cultiva- tion of intelligent public opinion is most important, and each student should go out from a sanitary laboratory a mission- ary to his fellow men. That is, the ofSce of a laboratory of sanitary chemistry should be so to diffuse knowledge as to make it impossible for educated people to be deluded by the representations of unprincipled dealers. Freedom from superstition is just as important in this as in the domain of astronomy or physics. So long as chemists are employed by manufacturing concerns in making adulterated and fraudulent foodstuffs, so long must other chemists be em- ployed in protecting the people until the public in general becomes wiser. A part of the common knowledge of the race should be the essentials of healthful living, in order that the full measure of human progress may be enjoyed. There is needed a greater respect for food and its func- tions in the human body, a better knowledge of its effect on. the daily output of energy, its absolute relations to health and life, and the enjoyment of the same. The familiarity with these facts which is given by a few hours' work in the laboratory will make a lasting impression and will enable the- student' to benefit his whole life, even if he never uses it pro- fessionally. It is purely scientific knowledge, just as much as that derived from a study of the phases of the moon or the formulae of integration. The variety of operations in such work, calling for great diversity of apparatus and methods, is an educational factor not to be overlooked in laboratory training. For all detailed discussions and methods the reader ;s referred to such works as those of Wiley, Allen, Blythe, etc., but for the student who needs to study, as a part of general' education, only typical substances, and such methods as can. THREE ESSENTIALS OF HUMAN EXISTENCE. Q » be carried out within the limits of laboratory exercises in a college curriculum, the following pages are written. Not enough is given to frighten or discourage the student, but enough, it is hoped, to arouse an interest which will impel him at every subsequent opportunity to seek for more and wider knowledge. CHAPTER II. air: composition; impurities; relation to human LIFE. The average adult human being makes about eighteen involuntary respirations per minute. The tidal volume of air is from 300 to 500 cubic centimeters (30 cu. in.), about 2800 cubic centimeters (170 cu. in.) remaining in the lungs unless voluntarily expelled by deep breathing. The total volume expelled is often called the z'ital capacity, and is about 3400 cubic c'jntimeters for men and 2500 for women. Even when at rest a volume of 7000 to 12,000 liters (250 to 420 cu. ft.) of air passes through the lungs of each individual in twenty-four hours. Under conditions of exercise more or less prolonged or violent this volume may be doubled. The composition of the normal inspired air by volume is approxi- mately: nitrogen and argon 79 per cent., oxygen 20.9 per cent., other constituents o.i per cent. The air as it leaves the lungs contains nitrogen 79.5 per cent., oxygen 16.0 per cent., carbon dioxide 4.4 per cent., and is saturated with water-vapor. There has therefore taken place an inter- change of gases (called the respiratory exchange), by which oxygen has passed into the fluids of the body, and carbon dioxide into the air contained within the lung-cells. Only about one-fifth of the total oxygen is abstracted during each tide. If the composition of the inspired air varies from the air: relation to human life. II normal, this exchange is disturbed, owing to the difference in gaseous pressure and in rate of absorption which this variation causes. So dehcate is the balance of the active forces that serious disturbance of the functions of the living organism occurs if the percentage of oxygen is lessened by one or two tenths, or if the pressure is raised or lowered by a fraction of an atmosphere. It is true that, like a tree bending before the wind, the organism soon adapts itself to changed circumstances, provided the change is not too great nor too suddenly made; but, like the exposed tree, the living being is never quite so vigorous and symmetrical as it would have been without the effort to overcome disadvantageous conditions. That a permanent or habitual lowering of the oxygen in inspired air must be harmful will be readily seen from a con- sideration of the office of this gas in the body. To Lavoisier and Laplace we owe the knowledge that animal heat is de- rived from a process of combustion. Lavoisier held, how- ever, that the seat of this combustion was in the lungs, and it, is to Pfliiger and his pupils that we are indebted for the proofs that it is in the tissues themselves, while the lungs serve as a clearing-house or centre of exchange. By the union of the oxygen with the substances found in the tissues and brought to them by the circulating fluids of the body from the digested food, the heat necessary for the Hfe and work of the body is produced. This heat is needed to keep the tissues at the temperature at which they can best accomplish their work, to give mechanical power for the in- voluntary action of heart and lungs, for the processes of assimilation, and to furnish the energy for all voluntary work and thought. Thus both water and food are intimately con- cerned in the processes in which air is an essential factor. The statement made in the first sentence of Chapter I is 12 AIR, WATER, AND FOOD. therefore justified, namely, tfiat air, water, and food together are three essentials of human existence. A certain relation between the three means health, and any disturbance of this relation means unhealth, by which term may be designated a condition of less than perfect health not yet so serious as to be called sickness. Air being a mere mixture of the gases nitrogen and oxy- gen, in no definite atomic proportions, and carrying varying amounts of other substances, gaseous and suspended parti- cles, no definite composition can be given. The difference between the air over sea or forest plateau and that of city streets or of crowded tenements seems only slight if expressed in per cent. From 20.98 per cent, of oxygen in the first to 20.87 ^nd 20.60 in the last; from .022 per cent, of carbon dioxide in the purest air to .045 in cities and .33 in rooms, are the common variations ; and yet the effect of these apparently small differences on human beings subjected to them is very noticeable. It is customary to enhance these differences by expressing the results in parts per 10,000. That the carbon dioxide is of itself a disturbing factor is indicated by the observed fact that air which has had the per cent, of oxygen reduced by combustion to a point at which a candle will no longer burn may be made again a supporter of combustion by the removal of the carbon dioxide. A practical application of this principle is made in the devices used in diving and in entering mines filled with irre- spirable gases. There is a sensible effort in breathing, and a feeling of discomfort is usually experienced, if the carbon dioxide ac- cuinulates to ten times the normal amount, or 40 parts per 10,000 instead of 4. This is probably due to its solubility and to its interference with the respiratory exchange, since the interchange of gases is influenced by their " partial pres- AIR: RELATION TO HUMAN LIFE. 1 3 sures." Each gas forming part of a mechanical mixture exerts a partial pressure proportional to its percentage of the mixture. For example, if atmospheric air, containing 20.81 per cent, of oxygen, is at 760 millimeters barometric pres- 20.81 5ure, the partial pressure of the oxygen would be — X 760=158.15 millimeters. The following partial pressures of oxygen and carbon dioxide in inspired air and in the lung- cells show the extent of variation in different parts of the respiratory tract: Inspired Air. Lung-cells. Oxygen 158.15 mm. 122 mm. Carbon dioxide.... 0.30 mm. 38 mm. Gas will always tend to diffuse from ' the region of high- est to that of lowest pressure. Hence the reason for the great influence of pressure in causing the diffusion of oxygen from the inspired air into the lung-cells and for the converse movement of carbon dioxide. That variation in pressure has much to do with the discomfort is shown in the so-called mountain-sickness, experienced at high altitudes in rarefied air, and in the so-called caisson-disease, developed in men working in compressed air. If the passage from the caissons to the open air is made gradually, there is little trouble, but a quick change is often dangerous. A sort of mountain- sickness is experienced by many on entering a close room from the outside air. Usually this passes away in a measure as the organism accommodates itself to the new conditions. Even if the symptoms are not severe, there is a dulness or an irritability which is not conducive to the best apprehen- sion of a difficult subject or to the fullest enjoyment of an entertainment. This lessening of mental capacity is, especially to be de- 14 AIR, WATER, AND FOOD. plored in the case of school-children, who are at an age when respiration is most frequent and the need of pure air the greatest, and also when economy of efifort is most demanded. It has been said that from the study of the physiological effects of close air it seems to be indicated that the evil is due to the change in the respiratory quotient and to the con- sequent change in blood-pressure, which interferes with the circulation. The respiratory quotient is obtained by divid- ing the volume of carbon dioxide given off by that of the oxygen absorbed, and indicates how much of the oxygen has combined with carbon to form carbon dioxide, since one vol- ume of oxygen combines with cafbon to form one volume of carbon dioxide. The rate of exchange is influenced by questions of pressure, exposure, temperature, and water- vapor or moisture, muscular activity, and the like. Water-vapor is the most variable constituent, due to the changing capacity of air for moisture at different tempera- tures and to the character of the earth's surface. Whether over land or water, cultivated or forest region, air at o" C. contains only 4.87 grams of water per cubic meter, while air at 60° F. (15" C.) can take up 12.76 grams, and at 90° F. holds 33.92 grams. Since the human body is constantly giving ofif moisture from skin and lungs, and since this exhalation is an important factor in the bodily economy, the presence of ex- cessive moisture in the air exercises a decided effect. On clear, invigorating days the moisture in the air may be only 30 or 50 per cent, of that required for complete satu- ration at the given temperature, and although the ther- mometer reading may indicate 85° F. on a hot day, little discomfort follows; but let the humidity rise to 90 or 95 per cent, while the temperature remains the same, and oppres- sion, restlessness, or languor results. Much the same effects are seen in the case of close rooms and crowded halls. The air: relation to human life. 15 watery vapor given off (about 20 grams per person per hour) soon saturates the air, and the consequent drowsiness and headache usually attributed to carbon dioxide will be felt; while if this moisture is removed, the same proportion of carbon dioxide would hardly inconvenience the occupants. A relative humidity of 60 per cent, is said to be the most comfortable for house temperature. In normal man, exposure to cold .increases the respiratory exchange; but if he represses shivering and keeps still by force of will, it apparently does not. Politely sitting still in- creases the probability of taking cold. A high temperature lessens the production of carbon dioxide and therefore saves food. This may in part account for the oppressiveness felt by well-fed and warmly clothed persons in public places none too warm for those with a more restricted diet. Muscular activity increases respiratory exchange and causes a demand for food. A class of students passing across the campus, up several flights of stairs, into a lecture-room' vitiate the air for the first ten minutes at a rate higher by one part of carbon dioxide per 10,000 than half an hour later. The exchange is also stimulated by a meal. Not only the oxidation of the food itself, but the muscular activity of the alimentary canal and probably other accompanying activities call for an expenditure of energy which is supplied by in- creased heat production. Sodium sulphate is said to increase the various respira- tory activities, and some have held this fact to be one reason for the beneficial effects of certain mineral waters. The amount of carbon dioxide expired is estimated by Pettenkofer at .006 to .012 cubic foot per pound of body weight, according to the degree of exertion. Rubner con- siders that, in general, metabolic processes depend also upon the proportion of superficial area to the total volume of the 1 6 AIR, WATER, AND FOOD. body, hence the smaller the animal the greater the surface to the whole mass. Children give off in proportion to their body weight about twice as much carbon dioxide as adults. Another estimate gives the output of carbon dioxide as .0027 gram per hour per square centimeter of surface. Ammonia is also a constant component of the air of in- habited places and is washed out by rain and snow, as will be shown in Chapter VI. Of the occasional impurities, probably the most fatal is carbon monoxide arising from leaking gas-fixtures or de- fective furnaces. This gas has 250 times the affinity for haemoglobin and therefore forms with it a more stable compound than does oxygen, and hence its presence causes a deficiency of the latter gas in the blood, giving symp- toms like those observed in mountain-climbing or bal- loon ascensions. When the blood-corpuscles become about one-third saturated the effect becomes sensible; but if the quantity of gas is considerable, the symptoms are hardly noticeable before insensibility occurs. For this reason, glow- ing charcoal and open gas-jets are the favorite forms of cowardly self-destruction. In the neighborhood of factories, smelting-works, ore- heaps, and of cities btirning soft coal there is a noticeable amount of sulphurous and sulphuric acids, sometimes so con- siderable as to destroy vegetation. In places where gas is burned, oxides of nitrogen are formed in small quantity, the effect of which is known to be harmful. Minute quantities of hydrogen sulphide and of com- pounds of carbon and hydrogen and of other gases may be present, especially in houses with defective plumbing or in the neighborhood of barns, cesspools, and filthy back yards. These may reach dangerous proportions, but, like carbon AIR: RELATION TO HUMAN LIFE. 1/ monoxide, should not be permitted in or near any well-regu- lated household. Soot, being insoluble, accumulates in the lungs, as a post- ■mortem examination of persons who have lived for some time in a smoky city proves; nevertheless no definite ill effects have been as yet attributed to this cause. This again con- firms the inference that it is the gaseous constituents, and the varying temperature and pressure, which seriously affect the respiratory exchange The following results, obtained on the air of a large man- ufacturing city, will be of interest in this connection: * GRAMS PER 1,000,000 CUBIC METERS OF AIR.f Soot. H3SO4. Free NH3. Alb. NH3. HNO,. HNG^. 1000 to 40000 7000 to 63000' 100 to 1000 97 to 557 45 to 1063 o to 155 1 Partly HjSOs. It is probable that much of the danger ascribed to sewer- air arises from other causes. Since the atmosphere in sewer- pipes is always moist, the only probable source of organisms is the splashing of the water. Only about one-half as many organisms have been found in the air a'bove flowing sewage as in out-door air. Professor Carnelley and Dr. Haldane found only one-half as much carbon dioxide and one-third as much organic matter in such air as in that of the streets above. Beyond individual control, and in a measure beyond gen- eral control, there exists suspended matter in the air: fine volcanic dust, pollen, spores of moulds and algse, dried bac- teria, diatoms, small seeds of plants, soot and the finely pulverized earth from roads and cultivated and barren lands. To this portion of the air we owe beautiful sunsets and dis- agreeable fogs. To it manv affections of the throat and * Mabery: J. Am. Chem. Soc, 17 [iSgs). 105. t See also Bailey: " The Air of Large Towns," Science, Oct. 13, 1893. 1 8 AIR, WATER, AND FOOD. eyes are due, and by it disease may be transmitted. Some kinds of dust lodge in the air-cells and by irritation render the individual liable to disease, as statistics of the mortality in dust-producing trades show. In the air of houses this impurity increases a thousand-fold by means of the wear of furnishings and the accumulation on them of deposited par- ticles, by means of furnace-ashes and dried debris of all kinds. Only recently have the dangers of this part of the air we breathe been distinctly pointed out. Aitken* estimated that a cubic inch of air may carry 2000 dust-particles in the open country, 3,000,000 and more in cities, and 30,000,000 in inhabited rooms. Among these millions there may be found from ten to several hundred micro-organisms, moulds, and bacteria, and, under certain conditions, pathogenic germs. As methods of culture become more satisfactory and tests more universal, it may be demonstrated that many old or long-inhabited buildings furnish several varieties of patho- genic germs constantly to the air. According to some authorities, the most dangerous con- tamination of the air is the " crowd-poison," or organic matter given ofif with the carbon dioxide and moisture in the breath. References will be found in the 'bibliography to dis ■ cussions of the subject. No evidence has- ever been found in the course of investigations in this laboratory, covering a period of fifteen years, that the healthy human lung gives ofiE any toxic substance. * Nature, 31 (1S70), 265; 41 {iSSo), 394. CHAPTER III. THE PROBLEM OF VENTILATION. From the preceding chapter it will be seen how impor- tant is the purity of the air to human well-being, and how essential is the diffusion of the knowledge of the methods by which it can be secured. It is often said that artificial ventilation is a modern necessity. Remains of aqueducts and sewers have testified to the sanitary intelligence of his- toric peoples, but the ventilating fan does not seem to have been included, although natural ventilation by shafts and flues has been practised since man came out of cave-dwellings. It is true that customs have changed as to many items of daily life. In cities more people live on an acre of ground, thus fouling the air above and the ground beneath ; more factories are belching smoke; more coal is burned; houses are built with smaller rooms and less pervious walls; schools and lecture-halls are more crowded; people are better fed, con- sequently there is more garbage; streets are macadamized, allowing finely ground particles to fill the air with every pufif of wind; gas-pipes traverse the walls of every house and pass under every street; carpets, draperies, and much passing in and out cause an accumulation of dust unknown fifty years ago. Kerosene lamps require more oxygen than many candles. Besides, people are becoming less hardy and more sensitive physically, so that well-ventilated living-spaces are a modern necessity if human efficiency is to be maintained. 19 , 20 AIR, WATER, AND FOOD. As we have seen, the air of open spaces presents only- very slight variation at the same level or for several thousand feet above it. The movement of the air caused by the wind is usually so rapid, and the reservoir of air for many miles above the earth is so immense in comparison with the thin vitiated layer, that there are only to be considered enclosed spaces in which human beings remain for a period of time. To supply the 7000 to 12,000 liters (250 to 430 cubic feet) of tidal air per person in maximum purity, there must be brought to the person at rest some 1800 cubic feet of air per hour. If he were in an air-tight chamber 12 feet square and 8 feet high, a man would reach the limit of purity in 38 minutes; but no ordinary room is air-tight, and when the ■difference between inside and outside temperature is consid- erable, a rapid exchange is taking place even with doors and windows shut. To secure the passage of this large volume of air through a small space without causing a draft that will be objected to by the abnormally sensitive victim of modern luxurious habits is the problem of ventilation — one not yet satisfactorily solved. The sanitary engineer is expected to design the appara- tus and to aid the architect in so placing and proportioning flues, inlets, and outlets as to accomplish the desired results. Unfortunately it is too common, especially in the case of school and college buildings, to economize in the first cost by dispensing with the services of the expert and to leave to the builder and "practical" architect all such details. In any case, it often becomes necessary to call in the chemist to prove the need of reform, or to show by the composition of the air whether or not the ventilating plant is doing its work efficiently. The sanitary inspector, whose business it is to decide air: the problem of ventilation. 2r. upon the legal questions connected with tenements and fac- tories, must often rely upon chemical examinations of the air. The validity of these depends not only upon the per- fection and delicacy of apparatus and methods used, but also upon the judgment and intelligence with which the samples are taken. Many errors in the construction of buildings have been perpetrated because of an ignorance of the physical proper- ties of air and, consequently, a mistaken notion of the be- havior of a vitiated atmosphere. The lecturer on popular science who some forty years "ago enlightened (?) the com- munity on the chemistry of daily life was accustomed to use, as a striking illustration, a glass jar in which a small lighted candle was instantly extinguished on pouring into the jar a tumblerful of carbon dioxide which had been collected for the purpose. The inference was plain: carbon dioxide was heavier than air, therefore it falls to the floor and must be allowed to flow out as if it were a stream of water. Further confirmation of this inference was found in the frequently observed fact that a candle lowered into a well often went out just before the water was reached. Hence for many years the habits of thoughtful persons were formed on a belief in the heaviness of carbon dioxide or "bad. air," and in its tendency to go to the bottom of the room and into any holes it could find. This is only another instance of danger in half a truth. When do we find cold carbon dioxide generated in living-rooms? And how warm must the gas be in order to be lighter than the ordinary air? How quickly does dififusion take place? Until within a very few years the almost unanimous belief among the so-called educated classes was that the bad air could be let out by opening a window at the bottom, and, in spite of the lessons which might have been learned by any observant person in 22 AIR, WATER, AND FOOD. < hanging pictures or Christmas greens, the common practice in private houses, churches, and schools is to open the win- dows at the bottom. All ordinary vitiation of the air proceeds from^ a heated source. Human breath and warm air are lighter than cold air and rise even with their burden of carbon dioxide. It is only when they impinge on a very much colder surface, as on the window-pane on a very cold day, that they become suffi- ciently chilled to fall without mixing with the neighboring air. The freedom with which the gases of the air mix, as Well as the rapidity of the action, may be illustrated in a variety of ways. Open a bottle of any volatile and pungent substance, as ammonia or hydrogen sulphide, in one corner of a room, and almost instantly it may be perceived in the most distant part. In natural ventilation we have only to avail ourselves of these characteristic properties of gases; and whether we wish to get rid of the light gases escaping from furnace, stove, or gas-pipe, or of the specifically heavier carbon dioxide, or of the most dangerous dust, we must furnish an outlet at the place to which the fleeing enemy first arrives, lest it turn and rend us for our ignorance. It is usually sufficient to furnish this opportunity, the current caused by this willing escape drawing in sufficient fresh air to take its place except in very crowded rooms, and even these might be so ventilated provided the whole roof were one large ventilating flue. If, however, the air is to be drawn from the bottom of the room, its unwilling current must be pulled by a superior force, as by an open fire on the hearth, which heats the air above it so that, in rushing into the free air above, it draws after it all things movable within reach. Then, indeed, even the top of the room becomes quickly cleared and no corner can escape; but if the fire be air: the problem of ventilation. 23 long gone out and the chimney cold, the reverse takes place and cold, heavy air sinks to the floor, helping to confine the tad air at the top of the room. What the cold chimney cannot accomplish the mechani- cally driven fan can do, namely, by a slight compression force a draught even up a cold chimney. In this case the very unwillingness of the air to take the prescribed path helps in the result as water forced through a mill-wheel de- velops mechanical work. The warmed fresh air forced in near the top of the room loses its velocity as it mingles with that already present, and finds its way along the line of least resistance to the opening provided at the bottom of the Toom, into the flue, but only in case there is no easier way. Open doors or windows interfere with the prescribed course, and blindness to this fact on the part of the occupants of mechanically ventilated buildings has caused unjust com- plaints of the system. The necessity of regulating the con- sumption of fuel and admission of fresh air in accordance with variations of temperature, as well as the great care and trouble this involves, renders the " natural " system of ventila- tion practicable only in less crowded dwelling-houses where intelligence can control the varying factors. For schools, lecture-halls, or any enclosed spaces occupied by numbers of persons at one time, some form of mechanical ventilation offers the only hope of good air in cold climates. What form that shall take is for the engineer to decide. The chem- ist's part is to devise means of readily determining whether the persons in charge of the apparatus are using it to gain the results designed by the expert. As a test of how nearly practice approaches the theoreti- cal value, carbon dioxide is taken as the indicator, since it is present in a thousand times larger quantity than any other impurity and since it is easily determined. If the air has 24 AIR, WATER, AND FOOD. only the normal amount of carbon dioxide, it is but rarely that it contains enough of anything else to be harmful. The presence of hydrogen sulphide or of coal-gas is betrayed by the odor. Where the gas-supply is " water-gas," contain- ing 30 to 40 per cent, of carbon monoxide, there is greater danger; but if legal restrictions are complied with, the pres- ence of this can be detected in the same way, viz., by the odor. Danger may also arise from the presence of so-called " sewer-gas," which, however, is not a single gas, but a most complex and variable mixture of the more volatile products of decomposition. For the detection of " sewer-air " chemi- cal tests are of little value, since it contains no constituent in sufificient quantity and with sufhcient regularity to serve as an index of its presence. Ill-smelling gases are given off only when sewage is about eighteen hours old, hence dirty house-pipes are the chief cause of foul air. The delicate sense of smell is of value here. Indeed, an edu- cated nose is most essential in all examinations of house- air. " Crowd-poison," if it exists, keeps company with the increase of the products of respiration, and if the incoming air is strained or taken from a place free from dust, the par- ticles added to the air which is in the rooms will also be re- moved with the carbon dioxide. From nearly all points of view, carbon dioxide is an indi- cator of the efficiency of ventilation, especially if combined with observations of temperature and moisture. It is an in- dicator also readily understood and accepted by the public. The principles of ventilation may be readily illustrated to a class by means of simple apparatus. Such an apparatus, using candles and designed to illustrate the section of an ordinary room, is shown in Fig. i. In testing the efficiency of ventilation of any room or air: the problem of ventilation. 25 building, it is necessary to determine first the direction of the air-currents, for there can be no ventilation without currents. If the architect who designed the building, or the engineer who advised the architect, is responsible, then the chemist has only to follow directions in taking the samples; but fre- quently the chemist, as well as the sanitary engineer, is called Fig. I. — Apparatus to Illustrate tTie Principles of Ventilation. upon to make tests of rooms and buildings of which no plans are available. In the examination of such rooms, then, the position of flues or conduits, both inlets and outlets, which were intended to convey air or which serve without such intention, should first be located. Possible avenues of ingress and egress by means of loose windows, cracks around doors, etc., are to be considered. When there is great difference of temperature between outer and inner air, these allow of quite rapid change of air. Some means of rendering visible these currents is de- sirable, such as smouldering paper, magnesium powder, or fumes of ammonium chloride. 26 AIR, WATER, AND FOOD. When the direction and intensity of these air-currents have been determined, the places from which the air-samples are to be taken may be chosen. It will be evident in what part of the room stagnation occurs and where eddies are formed, also where the air escapes. In a room or building without artificial ventilation the air-currents are seen to be ascending until they become chilled, when they fall. An empty room will not show so decidedly the rise of air-currents as will an occupied one in which the vitiated air, being much warmer, rises more rap- idly and cools less quickly. In taking the samples all acci- dental means of contamination must be avoided and the occupants must be quiet, for the moving of persons causes disturbance in the air-current. There is room for great in- genuity in this part of the examination, as circumstances greatly modify the method of procedure. A fair sample, or a sufficient number of samples to give a fair average, must be taken. Having secured and analyzed the samples of air, the de- cision as to the efficiency of ventilation must be rendered. If the room examined is a study- or recitation-room, the stratum of air at the level of the students' heads should not contain over 8 or 9 parts per 10,000 of carbon dioxide, should not show a temperature of over 70° F., nor a humidity of over 35 or 50 per cent., and these conditions should be main- tained for hours at a time. For lecture-halls and spaces occupied for only one hour at a time, with ample time between occupation, it is admis- sible to allow 9 to II parts. If fan ventilation is used, the outlet should give the average degree of contamination. If no system is used, the air at the top of the room is first vitiated; only at the end of twenty minutes to half an hour do the lower layers begin to show it. CHAPTER IV. ANALYTICAL METHODS. DETERMINATION OF CARBON DIOXIDE. General Statements. — ^The methods of determination all rest upon the property which the " caustic alkaHes," the hydroxides of potassium, calcium, and barium, possess of uniting with carbon dioxide and forming stable compounds. Where it is necessary to absorb large quantities of the gas in a slight volume of solution, potassium or sodium hy- droxide is used. For nearly all of the " popular tests " cal- cium hydroxide, lime-water, is used because of its harmless nature and the ease with which it can be obtained from the corner drug-store, or from the quicklime procured from the mason's barrel. For vol- umetric methods barium hy- droxide is generally preferred, because of the less solubi.ity of the barium carbonate, it being only about two-thirds as soluble as the calcium salt. The very avidity with which these substances take up car- bon dioxide is a hindrance to the preparation of standard solutions in an atmosphere 27 i> Fig. 2. 28 AIR, WATER, AND FOOD. already rich in it. When once prepared the solution must be preserved with especial care, since contact with the hands or a whiff of the breath will reduce its strength and vitiate the results. All such solutions are best kept, in bottles well protected from the air by tubes filled with soda-lime and de- livered from a burette, as in Fig. 2. For some of the methods it will be found advantageous to have the solution measured for each test by means of an ^ automatic pipette, as shown in Fig. 3. This can be attached directly to a Hter bottle containing the stock solution, and, if placed in a suitable case to prevent in- jury, may be easily carried from one ^ place to another. This is especially con- venient for several of the " popular tests." Pettenkofer Method.— The method for the determination of carbon dioxide which has been found most satisfactory in accurate work is a modification of the Pettenkofer method.* ' Principle. — In principle this consists in absorbing the car- bon dioxide from a known volume of air in barium hydroxide solution and titrating the excess with standard sulphuric acid. It is essential for the complete absorption of the carbon dioxide that the barium hydroxide be largely in excess so that not more than one-fifth of it is neutralized; furthermore, the ab- sorbing solution must be shaken up with the air for a con- siderable time. Collecting the Samples. — The samples are collected in four- or eight-liter bottles, the volume of which is accurately * Pettenkofer: Annalen, 2, Supp. Band (1862), p. i. GiU: Analyst, if (i8g2), 184. Fig. 3. air: analytical methods. 29 Icnown, the bottles having been caHbrated by weighing them iiUed with water. These bottles are provided with a rubber stopper carrying a glass tube over which a rubber nipple is slipped. They are filled with the air to be tested by means of a pair of nine-inch blacksmith's bellows, fitted with valves so arranged as to draw the air out of the bottle. The bel- lows is connected with a three-quarter-inch brass tube reach- ing nearly to the bottom of the bottle; fifteen or twenty strokes should be sufficient to replace the air in a four-liter bottle. At the time of collecting the samples the following observations should be recorded: Room, date, time, weather, place in room, number of people present, number of gas-jets or lamps burning, condition of the doors, windows, and trdnsoms; in short, everything which would tend to affect the amount of carbon dioxide in the air, or to cause currents or eddies. The bottles should be distinctly labelled and their volumes re- corded. If the temperature at the point where the samples are collected should be essentially dififerent from that of the laboratory, the bottles should be allowed to stand in the laboratory for half an hour or until they have attained its temperature. Directions for Laboratory Work. — ^The solutions of barium hydroxide and sulphuric acid which are used are approxi- mately of equal strength;, but since it is impracticable to pre- pare exact solutions of barium hydroxide and to keep them without change, the exact value of the barium hydroxide so- lution must be found' by titration against the standard sulphuric acid, which is made of such a strength that i cubic centimeter is equivalent to exactly i milligram of CO2. This standardization, as well as the subsequent titration, is best made in a small flask to lessen the error from absorption of carbon dioxide from the air. It will be found most gen- erally satisfactory to measure into the fiask about 25 c.c. of 30 AIR, WATER, AND FOOD. the barium hydroxide, add a drop of phenolphthalein solu- tion, and titrate with the sulphuric acid to the disappearance of the pink color. In all cases the first end-point should be taken as the correct one, because the pink color will some- times return on standing. This is due to the presence of minute quantities of potassium or sodium hydroxide in, the solution. The alkali sulphates will react with any barium carbonate ' which may be suspended in the liquid with the formation of alkali carbonates which give a pink color with phenolphthalein. The standardization should be repeated until consecutive results are obtained which check within 0.2 per cent, of each other. Determination. — Remove the cap from the tube in the stop- per of the bottle, insert the tube-tip of the burette so that it projects into the bottle, and run in rapidly 50 c.c. of barium hydroxide from the burette. Replace the cap and spread the solution completely over the sides of the bottle while waiting three minutes for the burette to drain. In doing this take care that none of the solution gets into the cap. Note carefully the temperature and barometric pressure. Place the bottle on its side and roll or shake it at frequent intervals for forty- five minutes, taking care that the whole surface of the bottle is moistened with the solution each time. At the end of this time thoroughly shake the bottle to mix the solution, re- move the cap, and pour the solution into a stoppered bottle of hard glass of 40 c.c. capacity, taking care that the solution shall come in contact with the air as little as possible. Under these conditions a full, well-stoppered bottle may safely stand for days before titration. For the titration, measure out with a pipette 25 c.c. of the clear liquid into a 75-c.c. flask and titrate it with the sulphuric acid as in the standardization. The diflference between the number of cubic centimeters of standard acid required to neutralize the total barium hy- air: analytical methods. 31 droxide before and after abso"rption gives the number of milligrams of dry carbon dioxide in the sample tested. The results may be expressed in parts per 10,000, by volume, under standard conditions (0° and 760 mm.), saturated with moisture (Method i) or dry (Method 2). Tables for this purpose will be found in Appendix A.* Example. — Data: Standardization, i c.c. Ba (0H)2 = 1.020 c.c. H2SO4. volume of bottle = 8490 c.c; Ba(OH);j used = 49.9 c.c. ; HaSOi used = 21. i c.c. ; temperature and pressure = 21" and 766 mm. Before absorption 49.9 c.c. Ba(0H)2 = 49.9 X 1.020 = 50.90 c.c. HaSO*. After absorption 49.9 c.c. Ba(OH)a = ^^^ X 21.1 = 42.12 c.c. HaSO^. .•.(8490 — 49.9)= 8440.1 c.c. air contain 50.90—42.12 = 8.78 mg. CO2. Method I. — I c.c. CO2 saturated with moisture at 21" and 766 mm. weighs 1.79624 mg. (Table II, Appendix A). 8.78 .-. 8.78 mg. = , =4.887 c.c. CO3 saturated with moisture. Hence in 10,000 c.c. of air there are — — — X 10,000 = 8440. 1 5.79 parts CO2. Method 2. — In this method the volume of air is reduced to standard conditions of temperature and pressure, under which conditions the weight of a cubic centimeter of dry CO2 is a constant quantity. * Dietrich's Table, the one in general use, is not absolutely correct, the weight of a cubic centimeter of carbon dioxide at o° C. and 760 mm. being somewhat different from that given at present by the best authorities, but it is sufficiently close for any but the most exacting work. 32 AIR, WATER, AND FOOD. Thus v' = vli + o.oo366(^'-^°)]. i/ = 8440.1, t'=2i°, /° = 0° ; hence v = ^S^y.y c.c. Also, v:v"=H":H, or 7837.7 : ;ir=76o:. (766— 18.5). (18.5 = tension aqueous vapor at 21°.) Then v" = 7709 c.c. = volume of air at 0° and 760 mm. I c.c. CO3 at 0° and 760 mm. weighs 1.9643 mg. 8.78 ^ ^^ 4.469 4.469 c.c. CO3. -^—^^-^ X 10,000= 5.79 parts 1.9643 f-i- ^ • • • 7709 COj per 10,000. Two samples are to be taken, closely following the notes, and the results calculated by both methods before collecting more samples. Then some one room may be taken and the quality of the air determined for the different hours of the day, or a comparison of different rooms may be made, or a building may be tested as a whole. All data and results ob- tained should be arranged in tabular form on a separate page of the note-book. Notes. — This method of collecting the air in a large bottle possesses a decided advantage over the method of slowly drawing the air through barium hydroxide contained in a long tube, in that a sample represents the condition of the air at a given time and not its average condition for a period of an hour or so. In collecting samples, care must be taken to avoid cur- rents of air or the close proximity of people. Duplicate samples can be obtained only in empty or nearly empty rooms. Even two sides of the same room will probably show differences, but two samples taken carefully side by side ought to agree within 0.05 part per 10,000. The chief source of error lies in the contamination of the samples or of the solutions by air from the lungs, the exhaled breath containing on an average from 50 to 100 times as much carbon dioxide as the air under examination. It is AIR: ANALYTICAL METHODS. 33 hardly possible to exercise too much caution in collecting the samples and in carrying out the analytical procedure. All rubber stoppers which are used should first be boiled in dilute caustic soda, then in a dilute solution of potassium bichromate and sulphuric acid and thoroughly washed. Popular Tests — hi addition to the standard method for determining carbon dioxide just described, there are also cer- tain so-called " popular methods '■' which can often be used with advantage. These methods do not give so accurate re- sults as those obtained by the standard method, but on the other hand the apparatus required is much simpler and more ■compact, can be more easily carried from one place to an- other, and if used carefully and intelligently will give fairly .good results. Several of these simple tests will be described in detail. (i) Method of Cohen and Appleyard.* — Principle. — This method is based upon the fact that if a dilute solution of lime-water, slightly colored with phenolphthalein, is brought in contact with a sample of air containing more than ■enough carbon dioxide to combine with all the lime present, the solution will be gradually decolorized, the length of time required depending upon the amount of carbon dioxide present. That is, the quantity of lime-water and the volume of air remaining the same in each case, the rate of decoloriza- tion will vary inversely with the amount of carbon dioxide. The method is scientific in principle because it recognizes the fact that the absorption of carbon dioxide by dilute alkali solutions is a time-reaction. Directions. — ^Collect several samples of air in white, glass- stoppered bottles of one liter capacity, either by exhausting the air from the bottle with a pair of bellows or by com- pletely filling the bottle with water and then emptying it at. * Chem. News, 70 (i8g4), iii. ainuies to ;he Solution. COj per 10,000. 3i 7.0 4 5.3 4i 5-1 5 4.6 5i 4-4 6i 4.2 7h 3-5 34 AIR, WATER, AND FOOD. the point where the sample is to be taken. Run in quickly from the burette lo c.c. of the standard lime-water (see Re- agents, p. 204), replace the stopper and note the time. Shake the bottle vigorously with both hands until the pink color disappears. Note the time required, and ascertain the cor- responding amount of carbon dioxide from the following- table. TABLE. Time in Minutes to r^rt ^^ Time in Minutes to Decolorize the Solution. ^"» P" '°'°°°- Decok li 16.0 Ij 13.8 ij 12.8 2 12.0 2i II. 5 2| 8.6 3i 7-7 Modified Cohen Method. — If all the tests of air by this- method are to be made in the laboratory, it wiJl be found best to keep the standard solution in a bottle carefully protected from the air, and to draw it ofif from a burette a5 wanted for each test. In order to make the apparatus more portable and convenient for a number of tests at a distance from the laboratory, the following modification of the method is used, and has been found to give excellent results. The 10 c.c. portions of the standard lime-water are measured into thin glass vials which are tightly closed with rubber stop- pers. A number of these vials can be filled at once, since the solution will keep its strength for a long time if the vials are clean and the stoppers have been boiled with potash and bichromate as previously directed. In order to avoid get- ting traces of acid on the outside of the filled vials through handling, it is best to rinse them off thoroughly and keep them in a beaker under water until wanted for use. The samples are collected in the bottles as before, the glass stop- air: analytical methods. 35 per removed for a second, and the vial of lime-water quickly dropped in, stopper downward. The bottle is shaken once violently to break the vial, and is then shaken with a rotary motion until the solution is decolorized. If desired, a bottle of half the size, and smaller vials holding only five cubic centimeters of solution, may be used. Note. — Much of the difificulty experienced in the use of these simpler methods arises from the lack of definiteness in the composition of "a saturated solution of lime-water" which is genierally recommended for use in making up the test solu- tion. The amount of lime that water will take up varies considerably with the way in which the solution is made; for example, whether the water is simply shaken up with a cer- tain quantity of lime, or whether the solution, once saturated, is kept standing over an excess of lime. For this reason it is much better to have the strength of the lime solution definitely fixed by some method of titration. (2) Method of Dr. G. W. Fitz — Principle. — In this method the volume of air that must be brought in contact with a definite quantity of lime-water, in order to neutralize all of the lime, is taken as a measure of the amount of carbon dioxide in the air. The quantity of lime-water and the time of reaction remaining constant, the amount of carbon diox- ide will vary inversely as the volume of air required. In this laboratory the same solution is used for this method that is used in the Cohen method. The apparatus consists of a graduated tube or " shaker," of about thirty cubic centimeters capacity, and a number of homoeopathic vials, each conitaining ten cubic centimeters of standard " lime-water." Directions. — Be sure that the inner tube of the shaker slides easily within the outer one, then remove the inner tube and pour into the large tube the contents of one of the vials. Introduce the inner tube and press it to the bottom 36 AIR, WATER, AND FOOD. of the larger, then withdraw it to the " T " mark, the bottom of the inner tube serving as the index. Close the mouth of the small tube with the finger and shake the instrument vig- orously for thirty seconds. The volume of air thus brought in contact with the solution is 30 cubic centimeters, as there are 25 cubic centimeters of air above the solution when the inner tube is forced to the bottom of the larger. Then re- move the finger closing the small end, press the inner tube to the bottom of the larger and draw it up again to the 20-c.c. mark, thus admitting 20 cubic centimeters of fresh air. Shake the apparatus again for thirty seconds. The total volume of air now used is 30 -|- 20 c.c. = 50 c.c. Repeat the operation until the color of the solution is discharged. The first trial made will probably give the approximate amount of carbon dioxide, and subsequent tests with the other vials will aid in giving the correct result. After determining the volume of air which is required to decolorize the solution, reference is made to the table given below. TABLE. Air in c.c. used. CO, per 10,000. Air in c.c. used. CO, per 10,000. 30 28 91 9 Bad 36 22 103 8 46 18 Very bad 117 7 58 14 138 6 69 12 165 5 Good 82 10 207 4 Notes. — The stoppers and vials should be washed and dried after use and kept separate, and the parts of the shaker should be kept separate. In using' the shaker see that the fingers are clean, or close the mouth of the shaker with a rubber stopper instead of the finger; also take care to avoid loss of liquid upon the addition of fresh air. The same objection applies to this method as to the tube method of Pettenkofer, namely, that the air taken air: analytical methods. 37 is an average sample extending over some time and does not show its condition at any one time. New stoppers should be boiled in dilute caustic soda and then in bichromate solu- tion before teing used. (3) Wolpert's Method— PnMd/)fe.— When air contain- ing carbon dioxide is passed through lime-water the solution gradually becomes turbid from the formation of calcium car- bonate, and the richer the ,air is in carbon dioxide the less will be the volume of air required to produce a definite degree of turbidity. This is the principle on which this simple method is based. Directions. — A small test-tube provided with a black ref- erence-mark on the bottom is filled to a definite height with " saturated " lirne-water. The air is collected in a small rub- ber bulb and slowly forced through the solution, the operation being repeated until the reference-mark can no longer be seen through the turbid solution. The instrument is first calibrated by observing the volume of air required to produce turbidity out of doors or in some room where the percentage of carbon dioxide is known, after which it affords a ready means for comparative tests in cases where the air contains 20 parts or more. For testing modern systems of ventilation, where the amount is usually less than 8 parts, it does not give reliable results. The difficulties in the use of this method are the same as those noted under the Fitz meth- od, with the increased error due to the solubility of calcium carbonate in solutions of carbon dioxide. (4) Wolpert's "Luftprtifer" (Air-f ester). — This is an- other simple instrument for testing the purity of the air. Its action is based upon the well-known fact that the alkali carbonates give a pink color with phenolphthalein, while the bicarbonates do not. By means of a capillary siphon a one per cent, solution of sodium carbonate colored with phe- 38 AIR, WATER, AND FOOD. nolphthalein is allowed to drop at regular intervals upon a cord suspended vertically. As the solution flows down the string it absorbs carbon dioxide from the air, converting the sodium carbonate into the bicarbonate, so that the lower part of the cord will be white, while the upper part is pink. The height of the dividing line indicates on a scale the amount of carbon dioxide in the air. The chief value of this instru- ment lies in the fact that it acts continuously, one filling being enough to last for ten days, and can be consulted at any time to learn the condition of the air, just as a ther- mometer is used to indicate the temperature. In practice the usefulness of the apparatus has not been fully realized on account of the dryness of the air in ordinary rooms, which, interferes with the continuous flow of liquid down the cord. Carbon Monoxide. — The detection and estimation of carbon monoxide in the very minute quantities in which it is found in the air of ordinary rooms is a problem of consider- able difficulty. Detection. — Probably the most convenient test for detect- ing small quantities is the blood test. Dilute a large drop of human blood, freshly drawn by pricking the finger, to ID c.c. with water. Divide the solution into two equal portions, and shake one portion gently for ten minutes in a bottle con- taining about IOC c.c. of the air to be tested. Compare the tints of the two portions by holding them against a well- lighted white surface. The presence of carbon monoxide is indicated by the appearance of a pink tint in the blood which has been shaken with air. One part in 10,000 can be de- tected in this way.* The delicacy of the test can be increased by examining the blood, after shaking with the air, with a spectroscope. By collecting the sample in an 8-liter bottle 7 — — ■ * Clowes: " Detection and Estimation of Inflammable Gas and Vapor in the Air," p. 138. air: analytical methods. 39 and examining it in this way o.oi part in 10,000 may be de- tected. Determination.* — Principle. — Oxidation of the carbon monoxide to carbon dioxide by iodine pentoxide, iodine being liberated according to the following equation: I2O5 + 5CO = I2 + 5 CO,. ■. . . . N The iodine is titrated with sodium thiosulphate. 1000 ^ Directions. — Place 25 grams of iodine pentoxide, free from iodine, in a small U tube which is suspended in an oil-bath and connected with a small absorption-bulb containing 0.5 gram of potassium iodide dissolved in 5 c.c. of water. Heat the oil-bath to 150° C, and pass the air, previously drawn through U tubes, — one containing sulphuric acid and the ■other solid potassium hydroxide, — through the apparatus at the rate of a liter in two hours. Titrate the Hberated iodine N bv sodium thiosulphate and starch. -' 1000 ^ Notes. — The temperature and barometric pressure should be noted and all volumes reduced to 0° C. and 760 mm. pres- sure. Using 1000 c.c. of air, it is possible to determine in this way 0.25 part per 10,000, by volume, of carbon monoxide. The use of tubes containing sulphuric acid and potassium hydroxide is to free the air from unsaturated hydrocarbons, hydrogen sulphide, sulphur dioxide, and similar reducing gases. Nitrites. — The determination of the amount of nitrites or nitrous acid in the air can be readily made as follows: Collect a sample of the air in a calibrated eight-liter bottle, as in the determination of carbon dioxide. Add 100 c.c. of * Kinnicutt and Sanford: Jour. Am. Chem. Soc, 22 (igoo), 14, 40 AIR, WATER, AND FOOD. approximately — sodium hydroxide solution, (This should be free from nitrites and is best made by dissolving metallic sodium in redistilled water.) Shake the bottle occasionally and let it stand for about twenty-four hours. Take out 50 c.c. of the solution and determine the amount of nitrites as- directed on page 94. Micro-organisms. — For the quantitative determination of the number and distribution of the micro-organisms in air, the method employed by Tucker * in the examination of the- air of the Boston City Hospital answers very well. The apparatus used consists essentially of three parts: (i) a. special glass tube called the aerobioscope, in which is placed the filtering material; (2) a stout copper cylinder of about sixteen liters capacity, fitted with a vacuum-gauge; (3) an air-pump. The filtering medium which is used to retain the micro-organisms is a narrow column of sterilized granulated sugar about four inches long. In using the apparatus, the required amount of air is first drawn from the cylinder by means of the air-pump. A sterilized aerobioscope is then attached to the cylinder and the air is slowly drawn through it, leaving its germs in the sugar- filter. After the air has been drawn through, the aerobioscope- is taken to the culture-room and the sugar dissolved in melted sterilized nutrient gelatine. The gelatine is con- gealed in an even film on the inside of the tube, where, after four or five days, the colonies will develop, and can be counted by the aid of squares engraved upon the glass. This method possesses several peculiar advantages. The use of a vacuous cylinder allows a known volume of air to be readily aspirated, and the rate of flow through the filter is- easily controlled. Another great advantage is the use of a. * Report State Board of Health, Mass., i88g, i6i. air: analytical methods. 41 soluble filter (sterilized granulated sugar), since insoluble substances seriously interfere with the counting. Further- more, the removal or transference of the filter and its germs- is avoided. The apparatus is portable, and the method, a& compared with others, is exceedingly rapid of execution. Organic Matter. — In regard to the presence of organic matter in the air there is at present considerable variance of opinion. While some investigators have obtained results which indicate the presence of such organic matter, it has been found also that the amount which is obtained is very much less when the dust of the air is first removed by filtra- tion. The quantity of organic matter is therefore closely re- lated to the amount of dust, and there is strong evidence that this dust in the air is the source of the greater part, if not all, of the organic matter, unless there are present persons with decayed teeth, diseased lungs, etc. The methods of determination that are in general use may be divided into two groups. In the first group are those methods in which the organic matter is converted into ammonia 'and determined by Nessler's reagent. In the sec- ond group the organic matter is oxidized by boiling with dilute potassium permanganate, the excess being titrated with oxalic acid. No one method gives results which are wholly satisfactory, the chief difficulties being to secure an absorbing material which shall itself be free from organic matter, and to avoid the introduction of minute particles of organic matter or dust during the analytical process. Remsen * and Bergey f recommend the use of freshly ignited granular pumice-stone contained in a narrow glass absorption-tube. After aspirating a known volume of air, the pumice-stone is transferred to a flask, the ammonia dis- * National Bd. Health Bulletin, I, 233; II, 517. f Mis. Coll of Smithsonian Institution, No. 1037 {fSg6). 42 AIR, WATER, AND FOOD. tilled off from alkaline permanganate and estimated by Ness- ler's reagent. Experience with the method in this labora- tory has shown that it is practically impossible to prepare the pumice-stone so that it shall be absolutely free from organic matter, and that the mere act of transference of the a;bsorb- ing material resulted in a considerable error. Miss Talbot * found, furthermore, that all of the organic matter is not con- verted into ammonia by a single distillation, but that a second and third redistillation of the distillates uniformly gave higher results. She found it preferable to draw the air directly through the boiling permanganate, having the ap- paratus so arranged that the condensed steam was returned to the flask. In this way the particles of organic matter were returned again and again to be acted upon by the perman- ganate. Experience with all these methods is well summed up by Professor Remsen when he says: "It would be useless to have examinations of air made by any but the most careful workers. It would be time thrown away to have such an- alyses made by the average practical chemist." Dust and Soot — The dust in the air may be estimated by drawing a measured volume through tubes packed with cot- ton and noting the increase in weight. Soot may be deter- mined by drawing the air through combustion-tubing partly filled with ignited asbestos, and then determining the carbon by the ordinary methods of combustion. * Tech Quart., I (i88j), 29. CHAPTER V. TVATER : ITS SOURCE, PROPERTIES, AND RELATION TO LIFE AND HEALTH. (From the Householder' s Standpoint.') The metabolism which produces human energy is depen- dent upon the presence of water in the tissues. This water is derived in part from food which, as eaten, contains from 30 to 95 per cent.; in part from boiled water, as in tea and •coffee; or raw from well or city tap. The total daily supply per person for this purpose from, all sources is five or six pints. Water is also necessary to all forms of vegetable and animal life, even the lowest types, including those inimical to human health. Man has always used water as his beast of burden: to carry ships to the ocean, to turn mill-wheels, to generate electrical power. He has also forced it to be his scavenger, carrying the refuse of his activities out of his sight. Unless compelled by legal restrictions, he has given little thought to the effect on his neighbor of this treatment of their common property. In commion law, water is held to be a gift of nature to man for use by all, and therefore not to be diverted from its natural channels for the plet-sure or profit of any one to the exclusion of the rest. Neither has one the right to return to the channel water unfit for the use of his neighbor farther down the stream. That is, there is no private ownership in 43 44 AIR, WATER, AND FOOD. surface-waters flowing in natural channels. But this inter- pretation of eminent jurists has not always been strictly fol- lowed. Many cases have been decided, especially since the rapid growth of large cities, in direct contradiction to this- law. As population increases, cities need to go farther and farther into the country for their water-supply, and they often take from the few settlers found there the right to the water which passes their doors, for the benefit of far-away thousands. The law. in regard to that portion which never enters, or which escapes from visible channels, is less clear. It is usu- ally held that this water goes with the soil, and that rights to it may be bought and sold: that wells may be driven and drains dug, even if a neighbor's supply is cut off; but it is always maintained that no man has a right to place any sub- stances on or in the ground which shall render his neighbor's, well unfit for use. The changes in conditions of life have rendered impera- tive a careful study of the ways and means of practically com- plying with the law's demand without a serious restraint upon the progress of civilization. The daily quantity required for each person has increased from the two to four gallons drawn by bucket from the farm- house well to thirty or forty gallons taken from the town sup- ply by the turning of a faucet, and in cities where much is used for manufacturing purposes, for running elevators and motors, the daily amount may reach loo gallons per inhabi- tant. This constantly increasing use of water for other than cleansing purposes has enormously increased the difficulty of securing clean water for domestic use. Not only is a larger quantity of polluting material deposited in the water,, but it is carried farther from its source by the dilution. This fact, as well as the demand for higher standards of ■water: source, properties, and relation to life. 45 purity, has made the abandonment of private water-supplies a necessity, and has demanded from municipalities the best scientific knowledge and the most careful supervision of the •quality of the public supply. A city or town is under as strict obligation to furnish a 5afe supply of water as it is to provide safe roads. To this «nd, the proper construction and maintenance of reservoirs and a sufficient police surveillance of the watershed is as im- portant as abundance of supply. Education of the people at large is still necessary, not only that those who depend in whole or in part upon springs and wells may know how to protect themselves, but also that the necessary cost of the larger public (municipal) supply may be cheerfully paid for by the citizens. Leaving out of the present discussion such considerations as belong only to the engineer and specialist, the problem of potable water will be treated in this chapter from the point of view of the intelligent citizen and educated individual who cannot afford to remain ignorant of so important a factor in the general welfare. The reason why this education is needed lies in the fact that primitive habits of thought, influencing action in every-day life, survive long after the race has passed beyond the original conditions. In no respect is this more true than in regard to water. The ideal drinking-water of most persons is the clear, colorless, sparkling water of a spring, refreshing in its cool- ness and satisfying the aesthetic sense by its suggestion of purity. So strong a hold has this ideal that it is most diffir cult to convince the average person that any water which has these characteristics can be other than wholesome and, con- versely, that water lacking in any of these qualities is suitable for human consumption. Early man drank clear cool water 46 AIR, WATER, AND FOOD. wherever he found it. If there was not a spring at hand, he scooped out a hole in the sand. Pioneer settlers dug the well as near the kitchen door or the barnyard as they could find water, with a blind faith in the protecting power of mother earth, not wholly misplaced so long as the require- ments of the household did not exceed two or three gallons per person daily, and so long as the nearest neighbor was half a mile away. So persistent is this confidence in nature that in the light of this day a majority of intelligent people, even, will quaff at a roadside well or drink freely at a country hotel or go to live in a city without ever taking thought for the quality of the water. Water is water, and he who pauses with his glass half-way and asks whence comes the supply is scouted as a weak-minded crank. So, too, when town au- thorities have spared no pains or expense to secure a safe supply from a distant lake, and have guarded it by all means known to science, the primitive habit of thought requiring colorless water of an even coolness of temperature leads those who can afford it to purchase " spring "-water in jugs and bottles, with the blind faith of the savage that what comes out of the ground must be good. Fundamental race-habits are taken advantage of by the dealer in spring-waters as well as by the vendor of patent , medicines — the missionary has no chance against him. From the schools and colleges there should, however, be sent out a generation of more intelligent persons who, learning to weigh evidence, will not take chances and will help to develop a public opinion on sanitary matters, especially in regard to water-supplies. For not until there is an intelligent public can the present reckless use of water and ground be stopped. While not every man may be a chemist, he can have that modicum of knowledge which will enable him to understand the need of chemical tests of WATER: SOURCE, PROPERTIES, AND RELATION TO LIFE. 47 water and to distinguish between the work of the expert and the amateur. However safe this ideal of clear, colorless water may have been in early times, it must now be relegated, with the un- barred door and unwatched treasure, to the mountain fast- nesses. As the country becomes settled, appearance and taste are no longer sufficient guides; therefore scientific tests must be applied and the results interpreted by trained ob- servers to whom the individual subordinates his private judgment. The ideal water should be above suspicion, for if it has once been contaminated, who can tell how soon it will find bad company again? Not the analyst in his laboratory. In fact, the laboratory verdict is worth very little without a knowledge of outside conditions and without a keen detec- tive insight which scents out the most unlikely causes. Nevertheless the evidence given by analytical results is needed to procure conviction. Although " pure " water is found only in the laboratory, " safe " water, that which is reasonably free from objection- able substances, mineral and organic, may be obtained with sufficient care and knowledge. A clear understanding of the problem requires a close study of the circulation of water on the earth. Let us trace the course of water from sky to ocean, in view of its availa- bility for domestic use, and note the dangerous properties it may acquire, considering also the changes in condition which it may undergo in its course from mountain to sea. Water-vapor rising from sea and land is condensed in the upper air, then falls to the earth, absorbing, as it does so, ammonia, carbon dioxide, sulphur oxides, and other soluble gases, if present, and washing the air free from dust-particles, mineral and organic. 48 AIR, WATER, AND FOOD. This meteoric water (rain or snow), although nearly free from dissolved mineral substances, is therefore by no means pure. Furthermore, rain falling on insoluble rocks, bare or lichen-covered, or on loose, sandy soils, washes them also, giving up to the vegetation the ammonia and taking in re- turn carbon dioxide and dissolved albuminoid ammonia. Water thus enriched has increased solvent power on cer- tain rocks and soils. This rain-water soon forms rivulets which, passing down from the highlands into the forest, spread over the moss-covered area, soaking the leaves and peaty soil and extracting organic substances. Mountain brooks, as well as lowland streams, draining a region free from limestone, are thus colored brownish-yellow and furnish " meadow-tea," as Thoreau happily named it. As the stream flows on it re- ceives contributions of many kinds — the overflow of springs, the under-drainage from cultivated fields, the surface-wash from pasture and meadow. Scavengers are, however, con- stantly at work. Brought as dust by the ever-passing air- currents, seeds of tiny plants freely sprout in the water and grow rapidly whenever a quiet pool or lake gives oppor- tunity. The products of organic decay and the ammonia of the rain may be thus removed and the water pass on to the reservoir clear and soft and as nearly pure as nature furnishes. It is, however, becoming rare to find even a mountain stream or forest brook which has not been subjected to modification by human agencies. Three kinds of contamination may take place. First: A farmhouse high up on the hillside lays trib- ' ute for drinking purposes upon that water finding its way beneath the sand which appears in the form of a spring. The overflow is made into a duck-pond, or passes through the watering-trough by the roadside before it joins other water tumbling over the rocks as a rapid stream. The brook thus grown larger widens out a little below the farmhouse into a water: source, properties, and relation to life. 49 shallow pool, in which one or two cows frequently seek com- fort. The water has become rich in organic matter and sup- ports a thick growth of tiny plants; the stones, even, may be coated with green slime. This vegetation serves as a warning to the hunter and the woodsman, who wisely drink only of water from clear pools with bottom of shining sand. The heavy material stirred up by the cattle soon settles, leaving the water in the stream below clear, although probably a little yellow in color. It still tastes well and looks all right, and may be used by human beings with probable impunity. Second: The little stream 'next passes other farm build- ings, where the privy is put over it to save the trouble of cleaning, or, even if not so close, is placed in such a way as to -allow of a possible wash into it, especially in times of sudden rain. A case of typhoid fever develops at this farm. No pre- caution is taken to disinfect the discharges, and a portion of the dangerous material is carried into and along with the water. Some two or three miles below, another farmhouse, having no spring, uses this same little stream for its supply, perhaps damming it up into a little pond or pumping it into a tank. All unconscious of what has happened above, or ignorant of consequences, this water with a history is freely used, and perhaps the whole family come down with the dis- ease, perhaps only the delicate one may have it. It may be that they will all escape, owing to the fact that they were particularly robust, or that they drank no water raw, or that the conditions on the stream have been favorable to purifica- tion of the water by storage and consequent growth of the green plants, which are our friends in such cases; but if the water were pumped into a covered tank and used soon after, the chances are nine to one that some deleterious results followed. 50 AIR, WATER, AND FOOD. Third: A part of the water sinks through the sand, and by this filtration becomes freed from all suspended matter and consequently from the germs of disease, if present. In its course if it is intercepted and collected in a shallow well it may again be of great organic purity and free from danger, but it will surely bear the telltale marks of its progress in the increase of chlorine and solids which will have escaped all the agents of purification, and in the nitrates, the result of the process. It will be noticed that it is only after contamination with the " waste of human life " that danger comes to other human beings and that many circumstances modify that danger. The chances are about equal to those of fire; and as most householders think it worth while to insure against possible fire, so they should hold the chemist's certificate as a sort of water insurance; but since the fire policy does not protect from carelessness, the knowledge that the water-supply is once good does not absolve the householder or the citizen from the greatest care in protecting his premises. Duty to his neighbor should lead him to see that this coin of the world is passed on in as good condition as possible, and he should at least give notice of danger when he knows that it exists. But this general movement of water on and near the sur- face is not all the story. From 25 to 40 per cent, of the annual rainfall, in temperate regions, soaks at once into the ground, and passing downward through the soil to hard-pan, to clayey or impervious layers, or to rock surface, thence through crevices, broken joints, or glacial drift-deposits to- the water-table, flows along the slope for many miles, until it finds its way again to the surface, either from the bottom of a lake, the bed of a river, the side of a hill, supplying wells, or appearing as a spring free from all organic and suspended water: source, properties, and relation to life. 51 matter but often rich in gases. In any one of these courses it may be intercepted by man and caught or pumped for his use. Such water may never have been far from the surface; it may have been used and returned to the ground many times; it may have appeared as surface-water and again dis- appeared to great depths. It has been estimated that water moves in the ground at rates varying from 0.2 to 20 feet per day. This long contact with rocks will, of course, bring min- eral substances into solution which may be precipitated as new rocks are reached or other streams encountered, so that the same gallon of water may have had many stages in its course and may have -held many different substances in solu- tion. An example of how much can be so held is found in the waters of the alkali belt (page 199). It is no wonder that so active a solvent as water should take with it much substance whenever it remains long in con- tact with soil or rock, for it may be many months before that which has once sunk out of sight again appears. In fact, great rivers are supposed to flow into the sea from under the sur- face. Then, too, the acquisition of dissolved gases favors the solution of many substances; for instance, water carrying carbon dioxide dissolves limestone as well as lead and cop- per, and when at low temperature and containing ammo- nium carbonate water may dissolve ferric iron. Water carrying organic acids dissolves among other sub- stances iron compounds which may or may not be in the ferrous condition, and therefore may or may not be precipi- tated on coming to the surface. And as we have seen that the ground below a certain level is permeated with moving water, whatever is buried in the earth is likewise liable to enter the watercourses in one form or another. An understanding of this movement of water under- 52 AIR,- WATER, AND FOOD. ground, with the accompanying changes in its character, cannot be too strongly insisted upon, for the lack of com- prehension of it is at the root of most of the troubles from well-waters. For example, the leaching cesspool, the primi- tive " septic tank," delivers its more or less filtered water rich in nitrogen compounds into the general circulation at a depth below the most efficient action of the nitrifying or- ganisms, hence it may permit the passage of organisms of putrefaction into underground streams or into the well, when access is direct. Even when filtration is perfect, the products of decay are yet carried with it and so tell the story of the past. The difficulty is to determine the state of the filter which may be on a neighbor's land many hundred feet away, and to be sure that its action is uniform. Experience with artificial filters shows how difficult it is to maintain efficiency with rapid use; hence heavy rains or wet years may cause a state of danger not ordinarily 'existing. The relation of water to human health must be consid- ered chiefly in the light of the changes which go on in the substances held suspended or dissolved in it, and the effect of these changes on the wholesomeness of the water. The suspended matter may be either inert, as clay or sand; dead vegetable, as fragments of plants; living vegetable, as plants floating on the surface, diatoms, desmids, alg£e, etc.; dead or living animal, as infusoria, small crustaceans, etc. Wherever these occur there are found the lower orders of vegetable organisms, fungi, moulds, bacteria, ready to do the necessary work of decomposition preparatory to solu- tion. The mere presence of these forms of living matter does not of itself mean danger to those using the water, but among these may be found pathogenic organisms which are, at present, considered as liable to cause disease. Such mi- crobes do not find in water a congenial habitat, and, fortu- water: source, properties, and relation to life. 53 nately, do not thrive on the vegetable diet and in the cool tem- perature of natural waters, hence the other organisms soon overpower them; danger decreases not only in proportion to distance, time, and dilution, but also, probably, to the abun- dance of other vegetable life. Under favorable circum- stances the danger is, however, a very real one. The presence of certain living plants may, moreover, give rise to unpleasant, if not dangerous, tastes and odors, due to the presence of extremely pungent oils or other aromatic substances formed in the process of growth. When these plants are decaying putrefactive odors are also present, some- times rendering the water too offensive for use. These or- ganisms are described in Whipple's " Microscopy of Drink- ing-water," and in Chapter VII a short list of those which give characteristic odors will be found. The presence of much decaying vegetable matter in drinking-water is to be avoided, since it is not known what efifect it may have upon the general health of the individual, rendering him perhaps more susceptible to disease. Food-supply is a necessary condition for life, and there cannot be abundant growth in a water without a correspond- ingly large amount of dissolved substances furnishing the food for this living fauna and flora. As has been stated, water usually carries considerable mineral substance and is often supplied with organic and gaseous compounds, while nitro- gen is furnished from many sources, most abundantly from sewage, so that it is not strange that water-life is so abundant, but rather that it is not more so. Most of the difficulties in securing a satisfactory water-supply are connected with the cycle of nitrogen in its relation to organic life. This may be briefly stated as follows: Nitrogen is found as an essential constituent of all living matter. When thus combined, it is the so-called organic nitrogen, and is found 54 AIR, WATER, AND FOOD. in undecomposed vegetable or animal substances. As soon as dead, these substances may become food for micro-organisms and the nitrogen then appears in a form from which it can be obtained as ammonia; for instance, from decaying beans, from putrefying broth, and from fresh sewage. This process takes place with or without much air and may be accompanied by very bad odors. As soon, however, as the nitrogen has passed from the insoluble organic form into the soluble compounds from which ammonia is obtained, then, if oxygen is present, and only then, another set of micro-organisms take up the work and nitrites appear; when still another set have done their work the nitrogen is found only in combination as ni- trates, fully oxidized and mineralized, no longer organic or capable of sustaining the life of the lower forms of vegetation, but, on the other hand, the most valuable food for chlorophyll- bearing plants which convert nitrates again into organic nitrogen. This cycle may be arrested or broken at certain stages. If the soluble ammonia compounds are set free out of contact with air or below the layers of soil containing the nitrifying organisms, they may remain indefinitely un- changed. If nitrates have been carried below the reach of the roots of the chlorophyll-bearing plants, or if they are con- fined in a space deficient in oxygen, then an access -oi decom- posable organic matter with micro-organisms will cause a reduction of the nitrates to nitrites and free nitrogen, through the action of these lower plants which, in the absence of air, take the little oxygen they need from mineral com- pounds. These micro-organisms are not the only ones at work, however. In any sudden prominence of one factor others are apt to be overlooked; thus in the present case the in- finitely small has so powerfully affected men's minds that, partly because the micro-organisms are beyond their range WATER: SOURCE, PROPERTIES, AND RELATION TO LIFE. 55 of vision, such forms of life as are evident to the naked eye or with low powers of the microscope have been overlooked to an extent. As agents of putrefaction and of decay the micro-organ- isms have their work to do, but the final purification— the finishing up of the work — belongs to another order of life. The still minute but visible green plants— those which float free in water or attach themselves to larger growths — have now their part to play. The life-history of these forms has been Httle studied, and the work they do in the actual puri- fying of polluted water has been almost overlooked. The impression left on reading most books is that when foul mat- ter has been dissolved and converted into ammonia, carbon dioxide, and nitrates the work is done, but these compounds only furnish food for the next class, and these again for in- fusoria, tiny crustaceans, etc. In some cases these organisms succeed each other with great rapidity; in one case the fauna and fiora of a given pond varied each week of a season, certain rare forms being found only once. There is needed, almost more than anything else, a con- secutive study of the green plants found in water-supplies, since by their cultivation greater purity might be- attained and possibly a way might be found of exterminating the dis- agreeable ones. The most unexpected results may follow the long study of a single organism, such as has been given to Oscillaria prolvHca of Jamaica Pond for a period of eleven years. Weekly, sometimes daily, observations have been made for two or three years.* It is organisms of this class which give tastes and odors to water, and which, if enough were known concerning them, * Trans. A. A. A. 5'., 1898. S6 AIR, WATER, AND FOOD. would probably give perfectly trustworthy evidence as to the past history or source of contamination. The two classes of organisms work in opposite directions, and so long as food is present for either, life will increase with proportional rapidity. This connection of cause and effect should be made familiar to the intelligent citizen. When a. ground-water free from all organic matter but rich in nitrates is exposed in an open basin the rich growth of chlorophyll-bearing alg« follows as a matter of course; later,, decay sets in and products of decomposition abound, the air above being the source of a constant supply of spores of all kinds. When a house- or barn-drain empties into a small slug- gish stream, it soon becomes filled with green plants thriving on the ammonia, and it is often possible to trace the source of pollution of a large lake by the line of green anabasna. leading to the insignificant ditch. A curious blindness on the part of managers of water- works to the movements of water and its action in transport- ing material is seen not only in the almost universal proximity of cemeteries to reservoirs, but also in the common practice of dressing the sloping banks of turf vi^ith a heavy coating of manure. Even if this was derived from clean stables and was not liable to be contaminated with night-soil, the abun- dant food for plants which inevitably finds its way into the reservoir occasions as fruitful results in the water as on the banks, and is undoubtedly the cause of much of the trouble in storage basins. It is evident, therefore, that a once polluted water cannot be said to be purified so long as food for green plants re- mains, for the moment the temperature and other conditions become favorable growth will begin. The term "purifica- tion," taken in a chemical sense, should not be loosely used. water: source, properties, and relation to life. 57 Complete purification can take place only when all traces of former impurity, in any form, have been removed. Chemical precipitation of sewage leaves the soluble ammonia, and sand filtration leaves nitrates to serve for abundant life and sub- sequent decay in the streams into which the effluents flow. Such effluents are clarified and the organic matter may have been mineralized, but this is not purified water. Only when growing plants have removed this food and have themselves been removed can the water approach a purified condition. The effect of storage of water containing high nitrates in open tanks or reservoirs exposed to the collection of dust will be that spores of chlorophyll-bearing alg^, diatoms, desmids, etc., will soon develop and will increase as long^as the food (nitrates, mineral matter, etc.) lasts. Only by pro- tection from dust and light can such water be kept free from unpleasant accumulations of suspended organisms or from disagreeable tastes. Unpolluted surface-waters, on the other hand, improve on storage, as a general rule, if the basin is a clean one. The storage of polluted or clarified water is thus forbidden, since not infrequently the first indication of the pollution of a surface supply is given by the appearance of some member of that richly nitrogenous group of algse called cyanophycece, or " blue-greens," from the presence of blue or purple coloring matter along with the yellow-green chlorophyll. Since this group of plants contains from seven to eleven per cent, of nitrogen, while other groups contain only one or two, it is evident that, if it is to flourish, more nitrogenous food must be supplied. This may be derived from fertilized fields, from decay of other vegetable life, as well as from the richer source of direct sewage; but, in any case, the growth of these plants is a sign of abundant food- supply which must be cut off if they are to be starved out, as they must be unless they are removed while fresh by strain- $8 AIR, WATER, AND FOOD. ing or skimming, for the odor of their decay is so intolerable as to preclude the use of the water. In some cases the odor accompanying their growth renders the water quite objec- tionable, and neither natural nor artificial filtration is able to remove it. Either natural or artificial basins may have a collection of vegetable matter on the bottom which slowly decomposes in summer, and since the bottom water is colder, the resulting ammonia remains until the late fall overturn, when it is brought to the surface, where it favors the growth of diatoms and other cold-water plants. Certain diatoms, as asterio- nella, cause disagreeable odors. Such basins show the least ammonia in early October and the most in late November. In order to make any predictions as to the probable de- velopment of this flora and fauna of water, experience and at least a year's watching of any given supply are required until more is known of the life-history of these forms of life. Nothing is more needed to-day than work along these lines. When may disagreeable odors and tastes be expected? What precaution or measures may be taken in each case to prevent them? These are the questions the water-works superintendent, equally with the consumer, is asking, for the most part vainly as yet. As has been stated, surface-waters often carry stable or- ganic matter in connection with color, so that while the organic nitrogen shows high, no free ammonia or nitrates are formed on standing. These weak meadow-teas are now largely used for town supplies, and a word as to the source of the color may not be amiss. Many carbonaceous sub- stances, sugar, for exa r\T^ T^i IT* The amount of chlorine is espressed in parts per MAP Uh 1 HJi. 100,000. ^~» rr» « .-.^ •■-. .^ —^ .. . > ,~. ,— . -^ The lines represent normal chlorine. STATE OF MASSACHUSETTS '^^^ "^""■"^ "'°™ °'*^"'"' '='"°™'' ■""'^'^ ^™ * normal or nearly so. g ■{-£ O WI N G ^^® figures underlined represent chlorines of groimd- waters. NORMAL CHLORINE. water: source, properties, and relation to life. 6 1 ice in a pond -40 or 60 feet deep. In this case the impuri- ties have been excluded. This crystal ice is impermeable to air and therefore to what air carries, and of course to water and what it carries. An equally safe rule is to discard all " snow-ice " made from snow saturated with water. CHAPTER VI. THE PROBLEM OF SAFE AND ACCEPTABLE WATER AND THE INTERPRETATION OF ANALYSES. (From the Chemist's Standpoint.) From what has been said it will be evident that the prob- lem of safe water for domestic use is not so much concerned with the water itself as with its property as a carrier and its part in chemical changes. We have seen how a great variety of vegetable and ani- mal matter finds its way into the water of a settled region^ and as it is constantly being transformed from one form to another by the agency of multitudes of organisms, it is evi- dent that the exigencies of modern life render impossible the exclusive use of water of great organic purity. It is useless, therefore, to fight over again the battles of the past as to the source and kind of " organic matter " in water. We have also seen that it is not the mere presence of compounds of carbon, hydrogen, and nitrogen in drinking- water which gives the element of danger. It is not even the fact that these have taken part in animal life; fish and frogs continually die in ponds and streams, to say nothing of countless cyclops and mosquito larvae. Well authenti- cated cases are on record in which one drink of a polluted water has proved fatal; while, on the other hand, it is equally sure that highly contaminated water has been used with ap- parent impunity. 62 water: the problem of safe water. 65 When water has received excreta of diseased human beings, disease-germs are very likely to be conveyed by it to other human beings. In a city there are always cases of disease, therefore all city sewage is to be considered danger- ous. But besides the living germs there are other accom- paniments of decaying organic matter which, when in con- centrated form, sometimes show toxic properties. Certain facts and many conjectures lead to the conclusion that a water is " safe " only when free from decaying substances. Along with the millions of harmless micro-organisms engaged in the work of conversion there may be a few score inimical to the health of man, and for the education of the still skeptical public it is often advisable to speak somewhat strongly of the possible dangers from water-borne disease- germs. Nitrogen as the Essential Element in Living Matter. — All organisms from the lowest to the highest thrive only in the presence of food; therefore only that organic matter which serves to support life or which, as a product of life, may be deleterious to man is rightly to be held as dangerous. The element common to both kinds is nitrogen; therefore the water-analyst seeks evidence not only of its presence or ab- sence, but of the forms in which it is found and their relation to one another. It may be assumed that any water which shows no change in the relative amount of its nitrogenous compounds at the end of a week either does not contain the organisms necessary to effect this change or is wanting in the food upon which they can thrive. As, however, it is inconvenient to wait a week before deciding this point, other methods are used. The so-called albuminoid ammonia is supposed to indicate the amount of decomposable nitrogen- ous matter, but, as a matter of fact, taken by itself it gives little information of value. While its absence is conclusive^ 64 AIR, WATER, AND FOOD. its presence is not equally so; but a proof of its variability from day to day is really valuable. Whether used in the final interpretation or not, " organic nitrogen " (or that portion of it appearing as albuminoid ammonia) is always deter- mined, together with the other forms, as soon as the sample is received. A nitrogenous organic compound is dangerous from one of two causes: first, because it is already decaying and har- bors pathogenic germs or is giving off toxines; or, second, because it will furnish food for a further development of bac- terial life. As to its derivation from animal or from vegetable mat- ter, there need be little discussion, especially since the recog- nition of the high nitrogenous content of the blue-green algse and the nitrogenous character of " soil-humus " and the close approximation of animal and vegetable protoplasm. But it is most important to know if it is stable, since one of the best aphorisms ever contributed to the literature of water- analysis is given by Dr. Drown's statement, " A state of change is a state of danger." Results of the Decay of Nitrogenous Organic Matter. — The products of the first stage of decay of this class of organic matter are carbon dioxide and ammonia. It is to the latter that we turn for the proofs sought, by reason of the methods at hand for detecting such small amounts as one part in a billion parts of water, and because it is for the nitro- gen compound that we seek. The mere presence of free ammonia is not a sufficient in- dication of recent pollution from human sources. Rain-water, as shown in Table III, contains considerable quantities; decaying blue-green algag furnish it in still larger amounts, and moreover it offers acceptable food to plant-life and may therefore disappear in the form of combined nitrogen. \YATER: THE PROBLEM OF SAFE WATER. 65 Nevertheless, it is to be held as one of the chief witnesses, for it is found in sewage in a thousand times the quantity in which it occurs in ordinary potable water. While putrefac- tive decay takes place by stages, the lines of division are not sharply drawn, and nitrites, the result of the second stage, may be and usually are found in polluted waters together with ammonia. So frequently is this the case that it is considered circumstantial evidence sufficient to convict when both am- monia and nitrites are found together. (See Tables V and VI, p. 199.) The reason is not far to seek. Both are not only prod- ucts of decay, but both are in that unstable condition which indicates active processes, and which therefore means the presence of micro-organisms. Certain exceptions will be noted later. The fourth form of nitrogen, that found in nitrates, is no longer classed as organic; it is now become food for green plants and cannot nourish the class to which bacteria and pathogenic germs belong, hence it is fair to presume that for lack of food the latter have succumbed or have been other- wise removed. The value of this test is the proof it sometimes furnishes of previous sewage pollution, since the nitrogen present in excess of that brought down by rain must have been furnished either by fertilizers, by decaying matter, or by sewage. (See Tables V and VI, p. 199.) Organic Carbon. — Since by far the largest constituent of organic matter is carbon, some fifty per cent., it might seem as if this was the best indication of pollution. Indeed, it was formerly so considered, and many methods have been de- vised to show its presence quantitatively. As our knowledge of the slight differences between many forms of animal and vegetable substances grows, the probability of any conclusive evidence from this source, either as to past history or present 66 AIR, WATER, AND FOOD. condition, decreases. In short, although for many years water-analysts have been striving to perfect methods of de- tecting certain substances and certain organisms, it would seem as if they were no nearer a discovery of one simple de- cisive test, but, in most cases, were driven to a somewhat elaborate examination in which one test only furnishes one link in the chain of evidence. Sanitary Analysis. — The examination of a water to deter- mine its safety for domestic use is called a sanitary analysis, in distinction from that examination which determines its fitness for manufacturing purposes, for use in steam-boilers, or its medicinal value. Four points are to be determined: First, the amount, if any, of organic matter in a living or dead condition, sus- pended or dissolved in the water; second, the amount and character of the products of decomposition of organic mat- ter, and their relative proportions to one another; third, the stability of the undecomposed organic substances; fourth, the amount of certain mineral substances dissolved. From these results we draw conclusions as to the present condition and past history of the water. These conclusions are not in- fallible, but there are enough unavoidable risks in human life without taking unnecessary ones; and if pollution is proved, the cause should be removed or the supply aban- doned. Preliminary Inspection. — So long as the eye can re-enforce the other tests and the whole course of the water may be clearly traced, it is comparatively easy to judge of the charac- ter of a supply and of its safety for human use; but when a hole in the ground is the visible source, or the actual history of the water is hidden in unknown distances and depths, the diagnosis is more difificult. First, the geological horizon and superficial soil must be water: the problem of safe water. 6'J studied; the direction and flow of underground water, not the slope of the surface only; the possible sources of danger, occasional as well as constant, within at least a quarter of a mile radius. The composition of unpolluted water of the same region should always be at hand for consultation. Safe Water. — As has been said, we can no longer require pure water; the most that we can demand is that the supply shall be safe. To the uninitiated one sample of clear, color- less water seems very like any other. The safe, colored or muddy water of a stream or pond seems less desirable than the clear, cold water of a badly polluted well. A water may be normally safe and yet, from exceptional circumstances, be for a time a source of danger. In one case the mouth of a well at a factory was overflowed by a con- taminated brook raised above its usual level by a heavy shower for half an hour only. Some thirty cases of typhoid fever resulted, so close to one another and so suddenly ceas- ing as to leave no doubt of the fact that for only a few hours was the water unsafe. How, then, shall a chemist tell if at some past time a water may have been or at some future time may become a source of disease? Only by carefully weigh- ing all the testimony attainable — ocular, chemical, biological, bacteriological — in the light of past experience. The day of the vest-pocket sample, usually in a flavoring- extract bottle, cork and all, is nearly past, but that of the fruit-jar, with a sticky rubber ring and corroded zinc top, is still with us. That admiration for chemical knowledge and belief in chemical clairvoyance which expects the chemist tO' decide from a sample while you wait if a certain water caused the death of a person a month since in a distant town under unknown conditions is very trying to the man who knows his own limitations. The market value of an analysis cannot well be appre- 68 AIR, WATER, AND FOOD. ciated until a juster estimate of the professional training of the analyst is a part of common knowledge. Safe and Acceptable Water. — It is not enough that a supply shall be free to-day from disease-germs; it should re- main free from changes for a reasonable period of time. Therefore the advice desired by the towns seeking for sup- plies implies much more than mere analysis; it includes esti- mates of future changes, of variations due to possible further developments, and of the effect of these variations on accept- ability as well as safety. To be fully acceptable, a water should be free from color, odor, turbidity, sediment, and of a uniform temperature so low as to admit of use without ice. Only such water as has been earth-filtered and earth-cooled can meet this demand, but the supply of this class is becoming drawn upon to its limit; besides there are difficulties in the conveyance and storage of- ground-water which offset many of its advantages. From the foregoing paragraphs it will be seen not only that waters carry every possible degree of safety or danger according to the country they drain, the num'ber and habits of the people living on the watershed, and the presence or absence of factories, slaughter-houses, etc., but that many •elements enter into the judgment of a water-supply, and how different these elements are in different waters. Safe water is that which carries neither seeds of disease nor such sub- stances as are deleterious in any way to mankind in general. A brown water may yield 20 parts per million organic matter and show 10 parts oxygen consumed, and yet be a safe and wholesome water. A ground-water may show 5 parts nitrates, and yet for ten or twenty years prove a safe supply. Since, however, water is so universally made a carrier of xefuse, it is difficult to find a stream or well which fulfils the water: the problem of safe water. 69 above exacting requirements, and a compromise is made which sets certain arbitrary limits and so keeps the chances small. Such limits are very misleading of themselves, espe- cially if used over a wide extent of territory. The English standards, for instance, are not applicable to eastern North America. Only a study of all local conditions and a wise in- terpretation of all results can make standard figures of any significance. This is true, also, of bacterial results in surface- waters. In the natural condition of lakes and streams there are so many varieties of bacteria present and in such varying numbers, according to wind and rain and watershed, that taken alone the numerical count gives no more convincing proof than is found in chemical figures. While it is quite within the limits of possibility that a culture-tube of typhoid bacilli might be emptied into the middle of a river or be washed into a reservoir, and chemical analysis give no sign, yet no continuous natural means of contamination is known which is not accompanied by sub- stances readily detected by suitable chemical examination. In either case an epidemic may or may not result, dependent upon causes other than the mere presence or absence of the micro-organisms. If drainage from a house or barn is seen entering a stream, it does not need a dozen plate-cultures to prove that there is possible danger. Such tests may, however, when used with skill, serve to trace contamination back to its. source, and is another means at the service of the trained water-works superintendent whereby he can keep a close watch over the character of his supply. As a means of control of the efficiency of filter-plants the bacterial examination is invaluable, and as a knowledge of the forms which accompany pathogenic germs becomes more certain the value of these tests will increase, even if the 70 AIR, WATER, AND FOOD. classification and identification is not perfected to scientific accuracy. It is one of the penalties of living in a large city that the water-supply must of necessity be surface-water which has been caught and stored at a distance or that which has been filched from a stream, filtered and made passable. Conse- quently education must take the place of instinct, and custom must make that acceptable which circumstances render necessary. THE INTERPRETATION OF ANALYSES. Experience in cutting through glacial moraines for rail- ways or in driving levels for mining operations does not qualify a man for exploration of a Babylonian or prehistoric mound. Human occupations have left upon the sand and clay evidences which, although so slight as to be unnoticed by the casual observer, are like an open book to him who patiently acquires a knowledge of the meaning of the dis- placements, discolorations, and enclosed fragments. Flowing water, like sand and clay strata, bears evidences of its previous history no less intelligible to him who has the key to the cipher and who adds to the keen eye of the detective and ready wit of the interpreter the sound judgment of the engi- neer. Reasoning upon insufBcient premises will as often fail in the one case as in the other, while lucky guesses fre- quently encourage superficiality in both. After the analyst has entered on the blank (page 120) the six to ten records needed for a ground-water, or the fifteen to twenty for a surface-water; after the columns headed Bacteria, Diatoms, Alg^e, etc., have been filled in, there still remains the summing up of the case by the judge. The correct interpretation of results means a knowledge of the source, geological horizon, surroundings, probable water: the interpretation of analyses. 71 changes, and the significance of each item in this particular case.- Each class of water has its own characteristics. The presence, in quantity, of any given element is interpreted according to the kind of water under consideration. Spring- water is, of course, colorless; lake- water of equal safety is probably colored. Spring-water must be, as a rule, free from ammonia; lake-water may at times contain considerable amounts without detracting from its good character. Classification of Waters. — To facilitate examination, therefore, waters may be divided into three classes: first, cistern, brook, pond, and river water — so-called surface- water; second, spring and deep-well water; and third, shal- low wells and sewage effluents. Water of the last two classes has been for greater or less periods of time in contact with rock and filtered through sand, hence is designated as ground-water. A few examples taken from the different kinds of water showing the varying conditions to which they are subjected may serve to make the rules of interpretation clearer. Surface-Waters. — When rain-water falls on slated or shingled .roofs and is conducted into cisterns, it carries with it whatever deposits lave collected, the pollen of forest-trees •or disease-germs from city slums many miles away; from metal roofs it takes either the metal itself or the paint used to protect the surface. In all cases, lower forms of animal life, small insects, and soot from chimneys may be present. These foreign substances should be at once filtered out with- out allowing time for organic decay, unless there is an auto- matic device for wasting the first washings of the collecting surface. There are still substances in solution which would be better away; therefore the water is allowed to stand quietly in order that the changes may have time to take place — to ferment, as it is often technically expressed. After 72 AIR, WATER, AND FOOD. this season of purification the water is again faltered and stored ready for use. There is usually color and a little am- monia, but rarely nitrates. The soluble metals, if once pres- ent, still remain. It goes without saying that all such cisterns must be absolutely impervious to surface drainage. For lack of one or all of these precautions, cistern-water has- often been found to be contaminated from cesspools, from leaden or painted roofs, or from decaying organic matter. Brook-water. — The rain that falls on mountain slopes of granitic or other insoluble rocks washes from them whatever loose earth may have fallen there, and from the firmly fixed lichens the small insects and other animal forms which they harbor. These are transported in brooks to the lower lands where the organisms decay, the heavier earthy particles fall- ing out by the way. If the upland rocks and soil yield a portion of mineral salts to the water, it may come out clear and colorless even if it has not penetrated to an appreciable depth. The water from these forest brooks, after remaining im- pounded in a clean lake or reservoir, exposed to sunlight and air, often becomes the safest source of supply. As with cis- terns, so with reservoirs, filtration, natural or artificial, may take place previous or subsequent to storage, or both before and after. Lake or Mixed Water. — Lakes are fed by springs as well as by brooks, or by that portion of rainfall which passes a few inches below the surface, and is filtered before reaching the main body. If the banks are sandy and uninhabited, the water will show good efifects from this filtration; but if the seepage-water comes from a settled country, it will bring either ammonia or nitrates. The analysis will quickly show this if the water sample can be taken before it has mixed •with that bearing the spores of plants which are fed by water: the interpretation of analyses. 73 nitrates. Often the very presence of these plants furnishes the proof .sought. River-waters. — A large stream, like the Mississippi, may receive the drainage of half a dozen cities a hundred miles distant and yet not give conclusive evidence of dangerous contamination, while a small river, like the Potomac, may become unsafe from the presence of a few villages a dozen miles away. Northeastern America is so well supplied with uninhab- ited high lands for collecting-grounds, and with basins in the glacial drift for storage in natural or artificial lakes, that very few rivers need to be used after they have become polluted. The Merrimac and the Hudson are, however, so used. In other parts of the country the use of rivers is an increasing necessity. From every point of view organic matter should be kept as far as possible out of running streams which may at any- time be needed for public supphes, or the natural purifica- tion by algce should precede the final filtration and storage. It is quite probable that this double treatment may be more frequently required as unpolluted water becomes more scarce. What the method of filtration shall be depends upon the character of the water, whether clear or turbid with clay, whether certainly polluted or only with a remote possibility of contamination. Each problem must be studied by itself without prejudice in favor of any one method. It is the re- sult which must be kept in mind, namely, the furnishing of safe and acceptable water to the community. Effect of the Storage of Surface-water. — In interpreting" his results, the analyst should take into account the influence which the keeping of water in basins has upon its character. Storage of surface-water is of utmost importance in all cases- 74 AIR, WATER, AND FOOD. of doubt. Most disease-germs find such water an unfavor- able medium for prolonged life, since exposure to sunlight soon destroys the darkness-loving bacteria, and a certain sterilizing effect results from the growth of green algse, so that water considerably polluted becomes purified if given time for the various agents to do their work; but time is essential. Odors. — For surface-waters one of the links in the chain •of evidence is found in the odor, cold and hot, which to the trained and sensitive nose often gives convincing testimony. A musty odor, unmistakably different from a mouldy vege- table smell, betrays sewage contamination even when the chemical analysis might not be convincing. This odor is not always taken out by filtration, neither is that of certain or- ganisms growing in stored water, notably Anabcena and Synura. A study of these organisms is invaluable to the routine observer who watches the seasonal and annual changes in his reservoir. Turbidity and Sediment. — The determination of turbid- ity and sediment, added to the odor, tells much to the expert, but very little to the inexperienced student. Turbidity may be due to drainage contamination, to growth of bacteria, to clay, to iron, to swarms of micro-organisms. Sediment may be sand, zooglea, fragments of plants or animals, or ferric oxide. Filtration. — The subject of filtration has been so exten- sively treated elsewhere that the student is referred to the bibliography on page 213. There are cases in which it is preferable to run the risk of too much alum in the drinking- water, and too much sulphuric acid in boiler feed-water, rather than of too many micro-organisms with the accom- panying organic matter. It will have been noticed that the ideal natural water is water: the interpretation of analyses. 75 -that which has been earth-filtered, and thus all suspended matter, including microbes, has been removed. This sup- poses that sufficient time has elapsed so that all decomposing organic matter has been destroyed. Man tries to imitate nature's processes, but expects to accomplish it in moments instead of months. The era of house-filters, those admirable culture-grounds for bacteria, is happily nearly past. Taxpayers are becoming convinced that a good original water-supply in competent hands is worth paying for. Where straining only is needed, a flannel bag washed daily is as efficient as any faucet-filter. If the latter takes out color as well, it should be closely watched. Water should not be first boiled and then filtered, but first filtered and then boiled. Summary. — Surface-water. — In general it may be said that the waters of the first class found in New England are generally more or less colored, and contain more or less sus- pended organic life and its debris, which often impart a de- cided odor to the water. These waters, draining for the most part wooded and sparsely populated regions, are low in free ammonia, nitrates, and nitrites; low, also, in mineral salts, and with only a slight excess of chlorine over the normal. They are usually high in organic matter and albuminoid am- monia even when entirely free from pollution. In other parts of the United States surface-waters may be low in color, but with much suspended clay and silt, and may hold in solution notable quantities of mineral salts. The latter aid greatly in the clarification by artificial filtration, which is so often rendered necessary by the excessive turbid- ity even if not by sewage contamination. In Table IV, page 198, will be found examples showing at a glance how profoundly the character of a water is affected by the geological horizon, whether its sourf e is in the glacial 76 AIR, WATER, AND FOOD. drift of the Appalachian region, or in the limestone of the Hudson River Valley, or in the saline deposits of the sub- sided areas. Deep Wells and Springs. — The waters of the second class are derived from the depths of the earth, far below any pos- sible surface contamination, and have long been imprisoned in the dark and cold, and often subjected to great pressure. The influence of pressure on organisms has not been entirely worked out, but from what is known it is probably very un- favorable to the life of the lower organisms. The results of many bacterial examinations have been vitiated by the diffi- culty of securing a sample from great depths without con- tamination by surface exposure — pipes open to the air har- boring many forms of life. Deep wells, 700 feet and more, are not likely to be dan- gerous. They may often contain ammonia from prehistoric coal-fields or tertiary deposits, but rarely nitrates. This is accounted for by the fact that " the result of the changes of the nitrogenous organic substances which fall into the earth is, without doubt, frequently the formation of gaseous nitro- gen." Also, that " salts of nitric acid on penetrating into the depths of the earth give up their oxygen." * Owing to their long sojourn in the depths of the earth, these waters are higher in mineral substances than surface- waters. Since their origin is unknown, the chlorine cannot be correctly gauged, especially as there are saline waters deep down in rock cavities in all parts of the world. It is usually believed that these deep wells furnish a safe, palatable water when the kind and amount of mineral matter is not objectionable. Shallow Wells. — It is not to be wondered at that waters * MendeUeff: "Chemistry,'" p. 223. water: the interpretation of analyses. T7 of the third class — ground-water, taken from just beneath the surface layers of the soil — should contain many sub- stances foreign to the waters about them as well as to those at greater depths. The shallow wells, which are practically more or less diluted sewage efifluents, present the greatest variety. They may be clear and colorless and show as great organic purity as the best mountain spring. In other cases, the overworked filter permits the passage of organisms and undecomposed material. In either case there will be found those compounds which, being soluble and stable, are car- ried with the water as signs to be read by him who knows the language. A complete history of each specimen of this class of ground-water is desirable, and with sufficient patience and care it may be obtained with reasonable accuracy, if the principles governing the circulation of water and the changes of the organic matter it carries be kept well in mind. It is certain at once that absence of color, of organic mat- ter in any form, and of odor should be insisted upon, for ground-water is filtered water and the filter should be doing its work. A modicum of geological knowledge is essential, as the presence of shaly or slaty rock will permit the passage into underground water of surface drainage with less purification than will a granite or sandstone region. A clayey soil is a less efficient filter than a sandy loam and permits the pollution to travel farther. Nitrogen in Well-water — It may be taken as an axiom that the only form of nitrogen permissible in a good ground- water is that of nitrates, a fully oxidized or mineralized food for green plants. If nitrites are also present, a source of pollution is at hand, for, as has been said, nitrites indicate either a stage of oxidation not completed or one of reduction from nitrates in the presence of organic matter. If free am- 78 AIR, WATER, AND FOOD. monia be present, it is safe to say that the source is not only- near but in actual contact, since but a few hours' time is needed to oxidize the ammonia in any soil not waterlogged. It may also be pretty safe to assume that bacteria are present, since ammonia is the first stage of that decomposition which they accompany. It is the part of prudence, therefore, to avoid any water which contains both free ammonia and nitrites above .200 or .300 parts per million of the first, and .020 or .030 of the second. The absorption of nitrogen by plants is rarely complete, so that it usually appears in far larger quantities in contami- nated ground-waters than could be obtained from purified rain-water. The leaching cesspool discharges its liquid con- tents below the zone of green-plant life; fertilized soil also yields a portion of its food value to the lower layers. A small portion of the nitrogen of vegetable origin may appear as nitrates, but only as a derivative of soil rich in humus is it likely to play any considerable part. In eastern America nitrates above 0.5 parts per million would arouse suspicion, and above 5 parts would in most cases prove predous pollu- tion. It is evident that in the use of nitrogen as an indicator of the conditions of a water we are limited, by the changeful character of the compounds, to certain not-to-be-mistaken amounts, and that in the majority of cases the evidence given is not decisive. Chlorine in Well-water. — Fortunately there is another ele- ment not so eagerly sought for by plants and not liable to so many transformations. Thanks to the great solubility of its common compounds and to their stability, chlorine, once a constituent of a given body of water, is not extracted there- from and remains as a telltale to reveal the past history of a stream or spring. If a man is judged by the company he water: the interpretation of analyses. 79 keeps, much more a water-supply. From sewage all the nitrogen may be removed and the chlorine still remain. But in order to use this information with any degree of certainty the normal chlorine of the locality must be known. If a map showing isochlors has been made of the region or State, and if there are no geological deposits to interfere, this is easy; but if the chemist or engineer has an unknown coun- try to report upon, it will be necessary to examine the local conditions and to choose six, eight, or ten samples of prob- able freedom from contamination and to test them for com- parison. The sources of the excess of chlorine over the normal are usually the sink-drain with its burden of salted water from domestic operations; the house-drain, with its chlorine-containing excreta; and the stable-drain, with a slight chlorine content in comparison with the other two. Mineral Substances. — Since water Is a universal solvent, it is not surprising to find considerable amounts of mineral matter in the two columns " Total Solid Residue on Evapo- ration " and " Hardness." How much calcium sulphate or magnesium chloride or other soluble mineral is allowable in a potable water is for the physician rather than the chemist to say. As has been said, the human system possesses great adaptability, not only for dififerent foods, but for mineral sub- stances water-carried. Not so the steam-boiler or the laundry- tub, which reacts very sensitively and afifects the pockets of the consumers. In a region of soft water, high solids with chlorine and nitrates indicate sewage pollution. Silica is much more commonly present even in surface- waters than is often supposed. What its effect may be is unknown. Iron is not uncommonly found in combination with organic matter in either surface or imperfectly filtered waters in contact with soils poor in calcium salts. It is fre- quently accompanied by free ammonia, which causes an 8o AIR, WATER, AND FOOD. abundant growth of Crenothrix. It is also present in deep wells in the form of carbonate, which precipitates on exposure to warm air. In a considerable number of cases of public water-supply there is a mixture of surface and ground water which com- plicates the verdict, requiring a most delicate balancing of probabilities. The mineral contents often aid in this deci- sion. Well-waters, too, are often exposed to surface-wash because of poor protection at the mouth. Cyclops or other surface-water organisms often indicate this. Water-pipes. — After all, if the pipes conveying the water are of lead or brass, an additional danger appears. Gen- erally speaking, the purer the water the greater the risk. No common metal seems to withstand the action of -soft water; six to eight years being the average age of galvanized pipe, and eight to ten of iron pipe. It would seem as if cement-lined pipe must come into greater use until some kind of glass is invented which will withstand this corrosive action and yet admit of plumber's connections. Value of Tests. — It is often asked if some tests cannot be made by the ordinary person of average intelligence which will enable him to tell the quality of a water as well as the expert to whom he pays ten or twenty dollars for an opinion. A careful perusal of the preceding pages will have answered the question in the negative. There is no assay of water as there is of gold and silver. Not one but ten or twenty tests must be made. Not only must the tests be made with the utmost care and cleanliness of person, utensils, and room, but the results must be studied in the light of other experience and other knowledge, geological and biological, and after all this is done there is an array of circumstantial evidence which must be carefully weighed by one whose judgment and experience ena'ble him to read clearly where another might water: the interpretation of analyses. 8 1 see nothing. The value of a water-analysis is in direct pro- portion to the knowledge and experience of the one who interprets it. Clinical skill in addition to theoretical knowl- edge is required to interpret the figures obtained in the course of a water-analysis, as in the symptoms of a disease: and the analogy goes still further, for as some diseases are clearly defined, others are so complicated that only those who have had long experience can outline a safe course of treatment; so some waters bear the marks of their character so plainly as not to admit of mistake, while others require most careful study. For these reasons the value of water-analysis, should not be decried because the fears aroused by reports given by unskilled analysts prove groundless, any more than the prac- tice of medicine should be discarded because inexperienced men make mistakes. Is the water in any given case safe for drinking? To an- swer this question there is needed a knowledge wider than a chemist's of the relation of decaying organic matter and of the germ-carrying power of water to outbreaks of disease. There must be added the knowledge of the biologist, the en- gineer, and the sanitarian. CHAPTER VII. ANALYTICAL METHODS. General Statements. — Water-analysis cannot be carried on in an ordinary laboratory. In order to obtain satisfactory results it is necessary to have a room set apart for the pur- pose, and to exclude rigidly all operations which tend to the production of fumes or dust. Where such minute traces of substances are dealt with as in water-analysis, too much care cannot be taken to insure the absolute cleanliness of the ap paratus and the surroundings. It is desirable that the room be well lighted, and if possible the windows should face, toward the north. The methods for the examination of water which are de- scribed in this chapter by no means comprise all that are in use. The directions are given for the use of students in our own laboratory under the conditions obtaining, i.e., of large classes and of several courses of study, with especial reference to educational rather than purely technical needs, and in some- cases, no doubt, the traditions of thirty years may have unduly persisted. The methods have been so selected as to intro- duce a variety of apparatus and to illustrate principles. They have also been subjected to a thorough test in meeting the demands of practical work. Collection of Samples. — For the collection of water sam- ples, glass-stoppered bottles of about a gallon capacity are- best. Those used in this laboratory are of white glass, fifteen inches high to the top of the stopper, five and a half inches 82 water: analytical methods. 83 in diameter, and weigh about three pounds. They have flat, mushroom stoppers, on which is engraved a number to corre- spond with that on the bottle. The bottles, before being sent out, are thoroughly cleaned with potassium bichromate and sulphuric acid, washed with distilled water and dried. If glass-stoppered bottles are not at hand, new demijohns fitted with new corks may be used. A glass bottle or a demijohn is much to be preferred to an earthenware jug, because, if for no other reason, it is so much easier to be sure that the interior is clean. It should always be borne in mind that in water- analysis the question is one of very minute quantities of mate- rial, and that the methods to be employed are extremely delicate. Hence, in the case of many waters, careless hand- ling of the sample would contaminate the water to a sufficient extent to render valueless the results obtained in the labora- tory. In collecting samples, the following directions should be closely followed: * Directions for Collecting Samples AIR, WATER, AND FOOD. The reactions which take place consist first in the diazotiz- ing of the sulphanilic acid by the nitrite present in acid solu- tion, forming diazobenzenesulphonic anhydride. This reacts with the naphtylamine hydrochlorate, forming azo-a-amido- tiaphtylic parabenzol-sulphonic acid, which gives the pink color to the solution, the amount formed depending upon the amount of nitrite present. N N H I I I c c c /\ //\/ \ H— C C— H H— C C C— H II 'I I II I H— C C— H H— C C C— H \// \ /\ / c c c I I I - SO3H NH, H Determination of Nitrogen in the Form of Nitrates. — Directions.— Nitrogen in the fourth stage, that of nitrates, is next determined. In the case of ground-waters, measure two portions, one of 2 c.c. and one of 5 c.c, from the bottle, with a capillary pipette, into three-inch porcelain evaporating- •dishes; for surface-waters, always low in nitrates, take 10 c.c. from the portion already decolorized in the determination of the nitrites. Place the dishes on the top of the water-bath and let their contents evaporate gently until one or two drops are left; then set them away in a place free from dust, .that the remainder may evaporate spontaneously. Do not let them go quite to dryness on the bath. When the water is entirely evaporated, drop six drops of phenol-disulphonic acid directly upon the dry residue and rub it around with a glass rod to insure complete contact of the acid and the residue in the dish. Dilute the acid with 7 c.c. of distilled water and add 3 c.c. of the alkali solution. water: analytical methods. gj To prepare the standards, measure out the required amount of the standard nitrate solution (see Reagents, page 207) from the burette, add enough water to make the total volume 10 c.c, and two or three drops of the alkah. One cubic centimeter of the standard solution contains 0.000001 gram N as nitrate. The comparison is best made in the small porcelain dishes. For high colors the liquids are compared in tubes similar to the Nessler tubes, but shorter. Notes. — It will be found that if 10 c.c. of a colored water be evaporated directly, the color obtained with the reagents "will be much deeper as well as browner than that given by the standards; hence the necessity for first decolorizing. Chlorine interferes with the accuracy of the method, but not to any extent when present in less than 20 parts per million. If the amount of chlorine be more than this, the evaporation should be made in vacuo over sulphuric acid. Nitrites do not interfere with the test. The reaction is generally considered to consist in the formation of picric acid. While this is not quantitatively true, it offers the best explanation of the changes that occur. Trinitrophenol (picric acid) is formed by the action of the nitrates in the cold, dry residue upon the phenol-disulphonic acid with which it is moistened: OH OH I: i H— C C— SO3H NO,— C C— NO, II I +3HN0,= II I +2H,S0, H— C C— H H— C C— H \ / \ / + H,0 c c I I S0,H NO, Phenol-disulphonic acid. Picric acid. 98 AIR, WATER, AND FOOD. The addition of an excess of caustic alkali converts the picric acid to the alkali picrate, which imparts an intense yel- low color to the liquid. The best color is obtained by the use of ammonia. Large quantities of nitrates in colorless water may be de- termined by reduction to ammonia by sodium amalgam, or by any reaction which yields nitrogen, this being measured as gas. Determination of the Carbonaceous Matter or " Oxy- gen Consumed." Kubel's Hot Acid Method. Directions. — Measure loo c.c. of the water into a 250-c.c.. flat-bottomed flask; add 8 c.c. of sulphuric acid (1:3) and , N about 10 c.c. of approximately potassmm permanganate. Place the flask on wire gauze and heat it quickly to boiling. When the liquid begins to boil, introduce a small air-blast to- prevent bumping and to avoid too great a rise of tempera- ture. Boil the solution for exactly five minutes; remove it from the flame; let it cool one minute, and add 10 c.c. of N exactly — - oxalic acid. Titrate with the permanganate to a faint permanent pink color. In order to find the exact value of the permanganate solution a blank determination must be carried through in precisely the same way, using 100 c.c. of water free from carbonaceous matter. Example. — In the blank determination, 10 c.c. oxalic acid requires 10.35 c.c. permanganate. Since i c.c. of the oxalic acid equals 0.00008 gram of oxygen, i c.c. permanganate equals 0.00007729 gram. Suppose 100 c.c. water -\- 10 c.c. oxalic acid required 12.57 c.c. permanganate, then 12.57 — 10.35 = 2.22 c.c. per- manganate required by the water. 2.22 X .00007729 = WATER: ANALYTICAL METHODS. 99 .0001716 gram oxygen for 100 c.c. water = 1.716 parts per million. Notes. — For highly colored surface-waters 25 c.c. are taken and diluted to 100 c.c. with water free from organic matter; for sewages 10 c.c. are diluted in the same way. The oxygen given up by the permanganate combines with the carbon of the organic matter and perhaps to a cer- tain extent with the hydrogen, but not with the nitrogen. The amount of oxygen consumed bears some relation, there- fore, to the amount of organic carbon present in the water, but this relation certainly cannot be taken as a definite one in every case, the results varying even with the time of boiling. The method has its greatest value when it is used to compare waters of the same general character and having the same origin; for example, in making periodical tests of the purity of the effluent from a filter. Furthermore, in order that the results shall have this comparative value, it is absolutely necessary that the process shall always be carried out in exactly the same way, even to the minutest detail of quantity, time, and temperature. In some cases it may be found advantageous to heat the solution upon the water-bath for half an hour instead of boil- ing it for five minutes. Different kinds' of organic matter behave differently with various oxidizing agents, so that a comparison of the results obtained with different oxidizing agents may throw light upon the character of the organic matter, as well as its amount.* In waters from the watersheds of eastern North America the color and the oxygen consumed have a certain, though somewhat varying, relation. Determination of Chlorine. — The chlorine is deter- mined in natural waters by the method in general use; * Woodman: J. Am. Chem. Soc, 20 (iSgS), 497. 100 AIR, WATER, AND FOOD. namely, titration with a solution of silver nitrate, using potas- sium chromate as an indicator. Since the exact change of color which constitutes the end-point will vary with the sensitiveness of the eyes of different observers to red, each person should standardize the silver nitrate solution for him- self. To do this, measure into a six-inch porcelain dish 25 c.c. of distilled water; add 5 c.c. of sodium chloride solution (i c.c. = o.ooi gram CI) from the burette and three drops of potassium chromate solution. Titrate with the silver nitrate solution until the yellow color of the liquid assumes the faint- est tinge of reddish brown. Directions. — Waters which are high in chlorine, i.e., which contain 20 or more parts per million, are titrated directly, using 25 c.c. either with or without the addition of 5 c.c. of the salt solution. Waters which are low in chlorine are con- centrated before titration, 250 c.c. being evaporated to 25 c.c. on the water-bath. Brown surface-waters should be decol- orized as follows: Pour into a 750-c.c. flat-bottomed flask about 500 c.c. of the water. Add 3 c.c. of the milk of alumina; shake and heat the water quickly to boiling on an iron plate. When the liquid comes to a full boil, at once remove the flask from the plate to avoid loss by evaporation. Place it in an inclined position to allow the alumina to settle. Decant off 250 c.c. of the colorless water into a six-inch dish for concentration to 25 c.c, using a flask calibrated for both the hot and the cold solution. Before making the titration, rub down the sides of the dish above the liquid with a small quantity of distilled water free from chlorine, using a clean feather. Rinsing alone will not always dissolve the chlo- rides which adhere to the sides of the dish. Notes. — For titration by this method the solution must be as nearly neutral as possible. If the water is alkaline to ^ny extent, it should be neutralized with dilute sulphuric acid, water: analytical methods. lor using phenolphthalein as an indicator. The solution will then contain alkali only as bicarbonate, which does not interfere with the titration. Acid water must be made neu- tral by the addition of sodium carbonate. It is important that the process be carried out essentially as described, since it has been found that the results vary with the volume of solution in which the titration is made, the amount of chromate used, and the amount of precipitated silver chloride present.* A correction for volume can be made by means of the formula given by Hazen, but it is bet- ter to carry out the titration under similar conditions each time, and to use a volume of 25 c.c. rather than 100. Determination of the Residue on Evaporation and the Loss on Ignition. — Directions. — Ignite and weigh a platinum dish. Measure into it 100 c.c. of the water (200 c.c. in the case of surface-waters), and evaporate to dryness on the water-bath. When the water is all evaporated heat the dish in the oven at the temperature of boiling water for two hours, then let it remain in a desiccator over sulphuric acid for several hours and weigh.f The increase in weight gives the " total solids " or " residue on evaporation." If from a ground-water, save the residue for the determination of the iron. In the case of surface-waters the residue should be ignited and the loss on ignition noted. Heat the dish in a " radia- tor," which consists of another platinum dish enough larger to allow an air-space of about half an inch between the two dishes, the inner dish being supported by a triangle of plati- num wire. Over the inner dish is suspended a disk of platinum-foil to radiate back the heat into the dish. The larger platinum dish is heated to bright redness by a triple * Hazen: Am. Chem. Jour., il (i88g), 409. t In some laboratories it is the practice to dry at 110° or 130° C. I02 AIR, WATER, AND FOOD. gas-burner. Heat the dish in the radiator until the residue is white or nearly so. Note any blackening or charring of the residue and any peculiar " burnt odor " which may be given off. After the dish has cooled, sHghtly moisten the residue with a few drops of distilled water to secure weighing under the same conditions. Heat the residue in the oven for half an hour; cool in a desiccator and weigh. This gives the weight of " fixed solids," the difiference being the " loss on ignition." Notes. — Before the introduction of modern methods of water-analysis the determination of " loss on ignition " was the only method for the estimation of organic matter in water. In order, however, that the determination shall pos- sess any real value, it is necessary to regulate carefully the heat during the ignition, so as to destroy the organic matter with- out decomposing calcium carbonate or volatilizing the alkali chlorides. This is what the use of the radiator is intended to accom- plish, and in the case of surface-waters, with low mineral con- tent and considerable organic matter, the method gives gen- erally satisfactory results. But in the case of ground-waters having little or no organic matter and high mineral content the loss is often very great on account of the decomposition of nitrates and chlorides of the alkaline earths and the loss of water of crystallization. In waters of this class the determi- nation of " loss on ignition " is, therefore, generally meaning- less, although an approximation to the amount of organic matter can be obtained by the addition of sodium carbonate to the water before evaporating to dryness. By this means the alkaline earths are precipitated as carbonates, the chlorine and nitric acid are held by an alkaline base, and there is no water of crystallization in the residue. Even with this modi- fication the loss is considerable when magnesium salts are present, owing to the loss of carbonic acid. water: analytical methods. 103 The behavior on ignition is oftentimes significant. Swampy or peaty waters give a brownish residue on evapora- tion to dryness, which blackens or chars, and this black sub- stance burns off quite slowly. The odor of the charring is like that of charring wood or grain; sometimes sweetish, but not at all oflfensive. Waters much polluted by sewage blacken slightly; the black particles burn off quickly and the odor is disagreeable. Any observations on this point should be re- corded in the report (p. 120) under the heading " Change on Ignition." Determination of the Hardness. I. By Soap. — Clark's Method. Directions. — Measure 50 c.c. of water into a 200-c.c. clear glass-stoppered bottle and add the soap solution from the burette, two or three tenths of a cubic centimeter at a time, shaking well after each addition, until a lather is obtained which covers the entire surface of the liquid with the bottle lying on its side, and is permanent for five minutes. The number of parts of calcium carbonate corresponding to the volume of soap solution used is found in the table in Appen- dix A. This will give the total hardness. If it is desired to find the permanent hardness also, dilute 50 c.c. of the water to about 200 c.c. and boil down to 50 c.c. in a beaker, cool and determine the hardness as before. This will give the per- manent hardness, and the difference will be the temporary hardness. Notes. — When potassium or sodium soap is added to water containing calcium and magnesium salts, the soap is decomposed, and insoluble compounds with the fatty acids are formed. The importance of adding the soap in small quan- tities cannot be too strongly emphasized, especially in the presence of magnesium compounds. The presence of mag- 104 AIR, WATER, AND FOOD. nesium salts will be recognized by the peculiar curdy appear- ance of the precipitate formed and by the occurrence of a false end-point, the lather lasting about three minutes when the titration is about half done. If much carbonic acid be liberated, it is better to follow Dr. Clark's original directions and remove it by suction. By reference to the table it will be observed that values are not given for more than i6 c.c. of the soap solution. If in any case the water under examination requires more than ID c.c. of the standard soap solution, a smaller portion of 25 c.c, ID c.c. or even 2 c.c, as the case may require, is meas- ured out and made up to a volume of 50 c.c. with rec;ently distilled water. If the volume of soap used is always about 7 c.c, this will keep the results comparable with each other, although the element of dilution introduces an error. Potable waters, in the eastern United States, at least, are rarely so high in mineral matter as to require excessive dilution. In the case of extremely hard waters, however, the acid method is to be preferred. Distilled water itself, containing no calcium salt whatever, requires the use of a considerable quantity of soap to produce a permanent lather. The cause for this seems to exist in the dissociation of the greater part of the soap at the extreme dilution to which it is subjected,, and the slow accumulation of a sufficient quantity of undis- sociated soap to allow of the increase of surface tension to a point at which soap-bubbles will persist. By the temporary hardness of water is meant the hardness which is removed by boiling. It is due to the carbonates of calcium and magnesium held in solution by the carbonic acid in the water, probably in the form of bicarbonates. Perma- nent hardness is that which is not removed by boiling. It is caused by the presence of soluble salts of calcium and mag- nesium, not carbonates, but chlorides and sulphates princi- pally, held in solution by the solvent power of the water itself. water: analytical methods. 105 2. By Acid. — Hehner's Method. Directions. — For the determination of the temporary hard- ness or " alkaUnity," measure 100 c.c. of the water into a bottle such as is used for the soap test, and add 2.5 c.c. of the erythrosine indicator and 5 c.c. of chloroform. Mix well by N shaking and add — sulphuric acid from the burette in small quantities, shaking thoroughly after each addition. The pink color gradually grows lighter until the addition of a drop or two of the acid causes it to disappear entirely. Each tenth of a cubic centimeter of acid used represents one part of CaCOg in 1,000,000. Make a correction for the indicator by carrying out a blank determination with distilled water. For the permanent hardness measure out 100 c.c. of the N water and add to it more than enough — sodium carbonate SO solution to decompose the calcium and magnesium chlorides,, sulphates, and nitrates present. Generally 50 to 100 c.c. will be sufficient. Evaporate the mixture to dryness in a plati- num or nickel dish and dissolve the residue in a little recently boiled distilled water. Filter through a small filter and titrate N the filtrate and washings with — sulphuric acid, using ery- throsine as indicator. The difference between the number of cubic centimeters of sodium carbonate used and the acid re- quired for the residue will give the permanent hardness. Notes. — This method is especially useful for waters which require clarification by alumina and subsequent filtration. Lacmoid and phenacetolin can also be used in the determi- nation of the alkalinity, but they necessitate titration in a hot solution on account of their susceptibility to carbonic acid. The addition of chloroform when using erythrosine is to re- I06 AIR, WATER, AND FOOD. move the non-ionized iodeosine molecule as rapidly as it is formed by the addition of acid. When it is thus removed the neutralization of the alkali is at once apparent and hence a sharp end-point is obtained.* If a water contains sodium or potassium carbonate there will not be any permanent hardness and hence more acid will be required for the filtrate than corresponds to the amount of sodium carbonate added. From the excess, the amount of sodium carbonate in the water may be determined. Any alkali carbonate present would be calculated as temporary hardness by the direct titration; hence it should be calcu- lated to calcium carbonate and subtracted from the results found by the direct titration. Determination of Iron.f — Directions. — Evaporate loo ot 200 c.c. of the water to dryness in a platinum dish. (The weighed residue from the determination of total solids may be used if desired.) Treat the residue with 5 c.c. of hydro- chloric acid (1:1), being careful to carry the acid to the edge of the dish. In some cases it may be necessary to heat the dish gently on the water-bath in order to bring all the iron into solution. When all is dissolved with the exception of sihca, rinse the solution into a loo-c.c. tube and make it up to about 50 c.c. with distilled water. Add a solution of po- tassium permanganate drop by drop until the solution re- mains pink for ten minutes. Meanwhile prepare a blank standard with 50 c.c. of dis- tilled water and about a cubic centimeter of hydrochloric acid. Add 15 c.c. of potassium sulphocyanide solution to the waters and to the blank standard. Add the standard iron solution, in small quantities, .02 c.c. if necessary, from a capil- lary pipette, mixing thoroughly by pouring the solution back * Ellms: /. Am. Chem. Soc, 21 {iSgg), 359. f Thomson: /. Chem. Soc, 67 {iS8s), 493. WATER: ANALYTICAL METHODS. 107 and forth from one tube to another after each addition, until the color of the standard matches that of the water. One cubic centimeter of the standard iron solution is equal to 0.000 1 gram of Fe. Notes. — In the case of some river-waters it will be found necessary to add a few cubic centimeters of hydrochloric acid to the water while evaporating, in order to facilitate the solu- tion of the iron. This should be done on a separate portion from that used for the determination of total solids. The colors should be matched immediately after adding the sulphocyanide, since the color fades appreciably on stand- ing. The highest standard should not contain more than 3 c.c. of the iron solution, since the color then becomes too deep for accurate comparison. Determination of the Dissolved Oxygen. Method of L. W. Winkler* Collection of Samples. — The samples are collected in ■glass-stoppered bottles of known capacity, holding about 250 cubic centimeters. When water is taken from a faucet the bottle is filled by means of a tube which passes to the bottom of the bottle. A considerable amount of water is allowed to pass through the bottle and overflow at the top. It will be almost impossible to obtain duplicate samples unless the bot- tles are filled at the same time by means of a T tube, owing to variations in pressure in the pipes. In taking samples from a stream or pond, a stopper with two holes is used. A tube passing through one of these holes is sunk in the water to the desired depth, and the other is con- nected with a larger bottle of at least four times the capacity of the smaller one, and fitted in the same way. From the '~~ i * Birichte, 21 {18S8), 2843. I08 AIR, WATER, AND FOOD. larger bottle the air is exhausted by the lungs or by an air- pump until it is nearly filled with water. Unless the determi- nation is to be made at once, the rubber stopper of the smaller bottle is quickly replaced by the glass stopper so that no air is left in the bottle. The temperature of the water at the time of sampling should be noted. This can be conveniently done at the depth at which the sample is taken, by means of a thermometer fitted by a doubly perforated stopper to a bot- tle of about 500 c.c. capacity \i'hich has been filled with some of the water and then lowered to the desired depth. An in- strument capable of giving more accurate readings is the " thermophone " of Whipple and Warren.* The Determination. — Remove the stopper and add 2 c.c. of manganous sulphate solution with a pipette having a long capillary point reaching to the bottom of ihe bottle, and in the same way add 2 c.c. of a solution of sodium hydroxide and potassium iodide. Insert the glass stopper, leaving no bubbles of air, and mix the contents of the bottle. Allow the precipitate to settle and add 2 c.c. of strong hydrochloric acid with another pipette. When the precipitate is nearly all dissolved, rinse out the contents of the bottle into a flask and N titrate the liberated iodine with approximately sodium thiosulphate until the color becomes a faint yellow. Then add starch solution and titrate to the disappearance of the blue color. The first end-point should be taken, as the color will return on account of the reducing action of the organic matter present. Determine the exact normality of the thio- sulphate solution by standardizing it against a solution of potassium bichromate (i c.c. equals o.ooi gram iodine) as directed on page 176. * J. N. E. Water Works Assoc, 9 {/Sipj)', 203. water: analytical methods. 109 N Calculation of the Results. — i c.c. sodium thiosulphate 100 ^ = 0.055825 c.c. oxygen at o" and 760 mm. (This value would ordinarily be corrected for the barometric pressure, but the correction falls within the limits of experimental error.) Find the volume of oxygen by substitution in the following for- mula: n X 0.055825 X 1000 A = =c.c. oxygen m 1000 c.c. of water, N where n = number of c.c. of exact thiosulphate, and v = the volume of the bottle minus 4 c.c. (lost by addition of rea- gents). The results are reported in " per cent, of saturation," which is found by dividing A by the number of c.c. of oxygen taken up by 1000 c.c. of water when saturated at the given temperature. (See Winkler's table, Appendix A.) N , . , , For example, 30.4 c.c. 7^ thiosulphate were used to titrate the iodine liberated by the oxygen in 265.5 c.c. of the water. Temperature of sample was 9° C. Then 30.4 X 0.055825 X 1000 A 265.5-4 = 6.491 c.c. oxygen in 1000 c.c. of water. From the table, 1000 c.c. water at 9° C. dissolves 8.063 6.491 c.c. oxygen. Hence the ' per cent, of saturation " = ^ — ^ = 80.50 per cent. Notes. — This determination is a good illustration of an indirect volumetric process. A precipitate of manganous hydroxide is formed in the Taottle by the reaction of the manganous sulphate and the sodium hydroxide. This imme- diately combines with the oxygen in the water to form a cer- no AIR, WATER, AND FOOD. tain amount of manganic hydroxide. The hydrochloric acid which is added reacts with the manganic hydroxide to form chlorine, which in turn liberates iodine from the potassium iodide, the amount thus set free depending primarily upon, the quantity of oxygen dissolved in the water. The presence of considerable amounts of organic matter or of nitrites in- troduces an error. In such cases the method must be modified or a correction made. Details of the method used in such cases are given in the paper by Winkler previously cited. A correction is made for the volume of the reagents added, but if the precipitated hydroxides had settled before the acid was added, no allowance should be made for the amount of acid, since the water it displaces contains neither oxygen nor iodine. If water is collected in the ordinary way and transferred to the apparatus by pouring, there will inevitably be an ab- sorption of oxygen unless the water is already saturated. Thus a process which gives excellent results when the water is nearly or quite saturated may fail entirely to give accurate results when the dissolved oxygen is low or absent. The water may be supersaturated with oxygen, in which case the per cent, of saturation may be more than one hundred.* Determinations of dissolved oxygen in ponds and streams are best made on the spot. The very simple apparatus re- quired for the Winkler process can be packed in small space, and the entire determination requires only a few minutes. The absorption of the oxygen by the manganous hydroxide is complete almost at once, and it is unnecessary to allow it to settle for a long time before adding the acid. The titra- tion can be made with a small burette or pipette with accurate results. * Gill: TtcA. Quart., 5 {jSgs), 250. water: analytical methods. Ill Determination of Free Carbonic Acid. — Directions. — Measure lOO c.c. of water into a flask, add lo drops of N phenolphthalein solution and titrate with — sodium car- bonate solution until a faint permanent pink color is pro- duced. To obtain the exact value make a second titration, running in the sodium carbonate rapidly until near the end and then drop by drop until the exact point is reached. The pink color will disappear rather slowly near the end. One cubic centimeter of the sodium carbonate solution ^ 0.44 milligram of COg. Note. — The reaction consists in the formation of acid so- dium carbonate: Na,C03 + H,0 + CO, = 2NaHC03 The acid carbonate does not give a pink color with phenolph- thalein. Sodium hydroxide can also be used for the titration, but the sodium carbonate solution is preferable. Determination of the Color. — The amount of color is generally determined by direct comparison of the water with some definite standard of color. Various standards of color have been proposed, the objection to most of them being that they are not sufficiently general in their application, being adapted only for the color of some particular class of waters. Nesslerized Ammonia Standards. — The yellowish-brown tint of the surface-waters of the Atlantic watershed corre- sponds, except in the lowest grades, very closely to that of nesslerized ammonia, so that the standards for reading am- monia can be used also for the determination of the color. The comparison is made in the same kind of 50-c.c. tubes that are used for the ammonia determinations, but the tubes used for this purpose are kept separate from those used for the ammonia, since the least amount of alkali remaining in 112 AIR, WATER, AND FOOD. a tube (from imperfect washing, for instance) alters the color of the water. The scale used corresponds quite closely with the amount of the standard ammonium chloride solution in the standards. Thus a color of i.o is nearly the same as that produced by the nesslerization of i c.c. of the standard ammonia; o.i is about the color produced with o.i c.c. of the ammonia solution. In the higher grades of color, above I.o or 2.0, the tint varies considerably from that of the nes- slerized ammonia, and the degree of color is then better de- termined in wider tubes and in less depth. The degree of correspondence of the ammonia standards with the natural waters is dependant largely upon the. sensi- tiveness of the Nessler's reagent, a solution which is so sen- sitive as to precipitate in two hours, matching the colors more closely than one which will remain for twenty-four hours. This is perhaps due to the reddish tinge given to the solution by the incipient precipitation of the mercuric iodide. Natural Water Standards. — To avoid these variations in color, standards made from dark-colored water from swamps by various degrees of dilution, and verified by direct com- parison with suitably prepared nesslerized ammonia stand- ards, are used. They Iiave the same hue as the waters to be matched, as well as a degree of turbidity which corresponds well with that of surface-waters; once prepared, they will keep for a fairly long time if protected from the light and from the dust. These are the standards that are in use in this laboratory. Platinum Standards. — For ground-waters, which have only very little color and considerable hardness, and for fil- tered waters, the platinum color standards are convenient.* According to this scale, the color of a water is the amount of * Hazen: Am. Chem, J., \h(i8q2), 300. water: analytical methods. 113 platinum in parts per ten thousand, which, together with •enough cobalt to match the tint, must be dissolved to pro- duce an equal color in distilled water. In practice, a stand- ard having a color of 5.00 is prepared by dissolving 1.246 grams of potassium platinic chloride (equivalent to .5 gram platinum), i.ooo gram of cobalt chloride (equivalent to .25 ^ram cobalt), and 100 c.c. of strong hydrochloric acid in dis- tilled water and diluting to one liter. Dilute standards for use are made by diluting varying amounts of this standard to 50 c.c. with distilled water. Thus, by diluting i c.c, 2 c.c, and 3 c.c. to 50 c.c, colors of o.i, 0.2, and 0.3 are obtained. It is claimed that the platinum stand- ards are permanent if protected from the dust. Iodine Standards. — A standard for color which could be made up at the moment when wanted and without the use of costly apparatus would be a desideratum. Experiments made in this laboratory indicate that an aqueous solution containing a definite weight of iodine ofifers the best solution of the prob- lem. Owing, however, to the volatility of iodine even in dilute aqueous solution it is better to liberate it directly in the comparison-tube itself. For this the following solutions are required: Potassium iodide, o.i gram per liter; potas- sium bichromate, 0.09 gram per liter; picric acid, 0.2 gram per liter. For a color of 5.0, 50 c.c. each of the iodide and of the bichromate solutions are used; for lower colors proportional amounts are taken and diluted to 100 c.c. with distilled water. To each tube is added i c.c. of the picric acid solution, and just before the colors are to be matched add 2 c.c of strong sulphuric acid. The color develops, as in the case of nessler- ized ammonia, within ten minutes and can be relied upon ior about half an hour. A very slight milkiness aids in match- ing the color; a great hindrance to the use of metallic solu- I 14 AIR, WATER, AND FOOD. tions being their clearness or brightness as compared with natural waters. The comparison-tubes which give the most satisfactory results with colors from 5.0 to 0.5 on the natural water scale are ^^/jg inch wide and 9 V4 inches high to the loo-c.c. mark. For lower colors, narrower tubes, ^Vie inch diameter and the same depth, give closer readings. Determination of the Odor. — Cold. — Shake violently the sample in one of the large collecting-bottles when it is about half or two-thirds full, then remove the stopper and quickly put the nose to the mouth of the bottle. Note the character and degree of intensity of the odor, if any. An odor can often be detected in this way which would be en- tirely inappreciable if the water were poured into a tumbler. Hot. — Pour into a beaker about five inches high enough water to one-third fill it. Cover the beaker with a well-fitting watch-glass and place it on an iron plate which has been pre- viously heated, so that the water shall quickly come to a boil. When the air-bubbles have all been driven off and the water is about to boil, take the beaker from the plate and allow it to cool for about five minutes. Then shake it with a rotary movement, slip the watch-glass to one side and put the nose into the beaker. Note the odor as before. The odor may or may not be the same as that of the water when cold; it can be perceived, as a rule, for only an instant. Notes. — It is inevitable that a certain personal equation should influence this test. Each laboratory will have its own standards for routine work, but a certain familiarity with the more common odors will tend to allay public anxiety and to aid in a more watchful habit on the part of consumers. Good ground-waters do not give distinct odors unless they are de- rived from clayey soil, but the odor often betrays a contami- nated well more surely than any other test. Surface-waters water: analytical methods. 115 will nearly always yield a characteristic odor. This odor may be due to the organic matter contained in the water, or to the presence of minute plants or animal organisms. Among the odors which are frequently met are the "earthy," ".vegetable," "musty," "mouldy," "disagree- able," and " ofifensive." The " earthy " odor is that of freshly turned clayey soil. " Vegetable " is the odor of many normal colored surface-waters; it may be described as swampy or marshy, pond-like, and is often strengthened by heating. " Musty " can be likened to the odor of damp straw from stables; it is fairly characteristic of sewage con- tamination, and by the trained observer is distinctly distin- guishable from the mouldy odor. " Mouldy " is the odor of upturned garden or forest mould, or of a moist hot-house; it is somewhat allied to the earthy odor. " Disagreeable " is a term which is capable of wide variation among different observers. It may include certain characteristic odors which are peculiar to the growth or decay of certain organisms, as the " pigpen " odor of Anabcsna, the " fishy " or " cucum- ber " odor of Synura, etc. The term " offensive " is generally reserved for the sewages. These terms can be taken only as broad illustrations of the character of the particular odor, since the odor will very likely be described by different per- sons in different ways, and each laboratory will have its own characterization. The odor which often accompanies an abundant development of diatoms is a good illustration of this. It will be called by various inexperienced observers ofifensive, rotten, fishy, geranium-like, aromatic, in one and the same sample of water. The terms generally used to signify the degree of inten- sity of the odor are " very faint," " faint," " distinct," and " decided." The exact value to be placed on each of these terms will, as a matter of course, vary with the individual Il6 AIR, WATER, AND FOOD. analyst, but in a general way it may be said that the " very faint " odor is one that would not be detected except by the trained observer; the " faint " odor would be recognized by the ordinary consumer if his attention were- called to it; the " distinct " odor is one that would be readily noticed by the average consumer, but would not interfere with the use of the water; while the " decided " odor is one which would, in all probability, render the use of the water unpleasant. Biological Examination — The close relation of the odor to the living fauna and flora of the water makes it desirable that the chemist shall be able to recognize the more common forms of water plants and animals even if he makes no pre- tensions to a knowledge of cryptogamic botany or of zo- ology. Therefore a microscope and a concentration appara- tus should be in every water-laboratory. A full descriptio_n will be found in Whipple.* The bacteriological examination belongs to the expert rather than to the student, certainly in the present state of our knowledge of the lower organisms. It may be desirable for the student to be familiar with the simpler methods of plate and tube culture, and the water-works laboratory should, as in the above case, be provided with means for plain number counts, and directions for avoiding errors due to variations in temperature, time of culture, etc. A book to be recommended is Frankland's " Micro-organisms in Water." Deterniination of the Turbidity and Sediment. — The suspended matter remaining in the water after it has rested quietly in the collecting-bottle for twelve hours, or more, is called its turbidity, and that which has settled to the bottom of the bottle, its sediment. Good ground-waters are often entirely free from turbidity * " Microscopy of Drinking-water." N. Y., Wiley, iSog. water: analytical methods. 117 and sediment, the suspended matters having been filtered out during the subterranean passage of the water, but this is rarely true of surface-waters. The turbidity is various in character and amount, sometimes milky from clay or ferrous iron in solution; usually it consists of fine particles, generally living algae or infusoria. These often collect on the side toward or from the light, and a practised eye can, not infre- quently, recognize their forms. Some of the lower animal forms can also be seen by the naked eye, and the larger En- tomostraca are quite noticeable in many waters. The sediment may be earthy or flocculent; in the latter case it is generally debris of organic matter of various kinds. The ■ degree of turbidity is expressed by the terms " very sHght," " slight," " distinct," and " decided," and the degree of sediment by " very slight," " slight," " considerable," and " heavy." These determinations, again, are of value only to the routine worker, and for him there are various methods in use. The papers of Parmelee and Ellms * and of Whipple and Jackson f should be consulted for a description of these. Determination of Alum. — On account of the use of alum or aluminum sulphate as a coagulant in the filtration of water, a determination of alumina in the efHuent water is often nec- essary. This may be readily made by the logwood test. J Directions. — Dissolve about o.i gram pure hasmatoxylin in 25 c.c. water; this solution will keep for two weeks and works best after being made several hours. To 50 c.c. 'of the water, placed in a four-inch porcelain dish, add two drops of the hsematoxylin solution, allow the solution to stand for one or two minutes, then add a drop of 20 per cent, acetic acid. The standards are prepared at the same time, using 50 c.c. of distilled water and the required amount of a stand- * Tech. Quart., 12 {i8g<)'), 145. f Il'id., 283. X E. H. Richards: Tech. Quart., 4 {iSgi), 194. Il8 AIR, WATER, AND FOOD. ard alum solution. The comparison must be made imme- diately, since the color fades on standing. In this way the presence of one part of aluminum sulphate in five million can be determined directly in the water and with ease. Logwood itself can be used, but the test is not so delicate as with the hasmatoxylin. Boil 5 grams rasped logwood re- peatedly with 50 c.c. of water; reject the first four decoctions, saving the fifth for use. This solution is used in the same way as the hsematoxylin solution, but the fainter colors are not so easily seen, on account of the greater color of the log- wood solution itself. The logwood solution must be freshly prepared each time. It will work satisfactorily only for about two hours. Notes. — This test will show the presence of all soluble salts of aluminum which enter into combination with the coloring matter of the logwood to form a " lake." The alkalies and alkaline earths give a purplish color with logwood extract, hence the test for alum can be made only in acid solution. Determination of Lead. — Lead in the minute quantities in which it ordinarily occurs in water is best estimated by comparing the color of the sulphide with standards. Directions. — If the water is colorless, acidify the clear solu- tion, concentrated if need be, with two or three drops of acetic acid, and pass in hydrogen sulphide to saturation. If a color is produced, compare it in a loo-c.c. tube with the color given by varying quantities of a standard lead solution. If the water is too highly colored to estimate the lead di- rectly, evaporate three or four liters in a porcelain dish to about 25 c.c, add 10 c.c. of ammonium chloride solution and a considerable excess of strong ammonia. Then add hydro- sren sulphide water and allow the dish to stand some hours. Boil the contents of the dish for a few moments to expel the water: analytical methods. 119 excess of hydrogen sulphide, and filter. The precipitate con- tains all the lead, iron, and suspended organic matter, also copper and zinc if present, while the soluble color goes into the filtrate. Wash once with hot water, transfer the filter to the original dish, and dissolve the sulphides by boiling with dilute nitric acid (i part acid, sp. gr. 1.2, to 5 parts water). Filter and wash; evaporate to 10-15 c.c, cool, add 5 c.c. con- centrated sulphuric acid and evaporate until copious fumes are given ofif. Then, if the original water contained less than 0.25 part iron per million, add acetic acid and ammonia, boil, filter, and read the amount of lead in the alkaline filtrate, making the standards (page iii) also alkaline with ammonia. If the water contained over .25 part iron, wash the lead sulphate into a beaker with alcohol and water, and let it set- tle overnight. Filter, wash free from iron with 50 per cent, alcohol, dissolve the precipitate by boiling with ammonium acetate, filter, and determine the lead as above. Note. — If more than .25 part of iron is present, some of the lead will be held by the precipitated ferric hydroxide; and if 25 parts are present, all of the lead may be lost in this way; hence the modification of the method in the presence of con- siderable quantities of iron.* When copper is also present it is detected by the blue color given to the ammoniacal filtrate from the iron precipi- tation. Statement of Results — In reporting water analyses the results are best expressed in milligrams per liter, which for the majority of waters is equivalent to " parts per million." Occasionally it may be desirable to express the results in " grains per gallon." Parts per million may be converted into grains per U. S. gallon by multiplying by 0.058. For con- * Ann. Rep. State Bd. Health, Mass., 1898, 577. I20 AIR, WATER, AND FOOD. venience the results should be arranged in tabular form, such an arrangement being suggested below: SANITARY WATER-ANALYSIS. (Parts per 1,000,000.) Date. Physical. Residue on Evaporation. No. Color. Turb. Sed. Odor. Total. Loss. Fixed. Change Cold. Hot. Ignition, 121 3-9-'oo .50 0.0 0.0 Dec. None Cons. None None F. Veg. None 42-5 64.0 9740.0 I2-S 30.0 ( Slight i black 123 Nitrogen as No. Total Organic. Alb. Ammonia. Free Am. Nitrite. Nitrate. Ox. Cons. Total. Sc5i. Susp. Z2Z •598 .306 .014 .032 .170 .■36 .056 .000 .560 .003 .coo .003 .220 ..40 1. 14 4.83 .41 3.23 123 Hardness Chlorine. Iron. Biological (per c.c.) No. Bac. Plants. Diatoms. Cyano- phyceae. Algx. Animals. 20.0 23.0 560.0 1.8 6.3 X198.0 ' 1 229 .01 .46 123 No. 121 is from a pond; 132 from a spring; 123 from an artesian well. CHAPTER VIII. FOOD IN RELATION TO HUMAN LIFE: COMPOSITION, SOURCES,. DIETARIES. Paracelsus (1493-1541) taught that "the object of chemistry is not to make gold, but to prepare medicines." Van Helmont (1577) recognized water as a chief constituent of all living matter. Sylvius (1614) taught that combustion and respiration were precisely similar phenomena. The mod- em revival of chemistry has been largely due to efforts to preserve health. These efforts are turned more and more to the attainment of a high degree of daily efficiency instead of toward curing already established disease. Life itself is con- ditioned on the food-supply. Wholesome food is a necessity for productive life. Man can and does exist on very unsuit- able, even more or less poisonous, food, but it is merely ex- istence and not effective life. This is true not only of the wage-earner, but of the business-man, the professional man, the scholar. To be well, to be able to do a day's work, is man's birthright. Nevertheless a too large proportion of the American people sells this most valuable possession for a mess of pottage which pleases the palate for three minutes and weights the digestive organs for three hours. With no other known source of bodily energy, the student cannot afford to use up the capital in his bank lest he find the account overdrawn before middle age. With no hope of entirely ban- ishing evil microbes from the haunts of men, it behooves each one to so. nourish his body that the enemy can find no point of attack. 122 AIR, WATER, AND FOOD. The watchword of the State is prevention of disease; that of the individual is personal resistance. The economic and social conditions of daily Hfe have reached such a stage of development as to make a closer study of food-materials, for which half the cost of living is spent, not only desirable but imperative. With the products of the world exposed in our markets, the restraints of a restricted choice, as well as in- herited instincts or traditions, lose their force. The buyer, unless he has actual knowledge to guide him, is swayed by the caprices of the moment or the condition of his purse, and often fails to secure adequate return in nutritive value for the money paid. The fact that so much manipulated material is put upon the market renders this choice of food doubly difficult, since the appearance of the original article is often entirely lost, and to city-bred buyers even the natural product conveys little idea of its money value. It therefore seems necessary that an elementary knowledge of the proximate composition and food value of the more common edible substances should be recognized as an essential part of education. Chemistry is now found in the curricula of nearly all institutions devoted to higher education, so that it is possible, as it was not ten or twenty years since, to bring to students both the theoretical and the practical bearing of a study of food-materials in an instructive and practical manner. No branch of Sanitary Chemistry can yield more far-reaching results in the welfare of the community, since the more widely this knowledge of the composition of foodstuffs is disseminated the less danger to health and purse from the sophistications of unscrupulous dealers. True, the subject is not yet in that condition in which there is nothing more to learn. It cannot be taught in a dogmatic manner. No hard-and-fast rules can be given FOOD IN RELATION TO HUMAN LIFE. 1 23 ■either as to the quantity or the quality of the daily diet, but enough is known to enable us to make life of more value, to lessen the suffering due to disease, and, consequently, to lower the death-rate and increase the productive power of the community. Attention must be called to this relation of food to health if the delicacy of constitution due to civilized habits is to be overcome and the lives of useful citizens prolonged. Men •otherwise sane are most reckless where food is concerned. Even noted authorities on sanitation have succumbed to dis- ease because the proper balance of nutrition and exercise 'was neglected. The physician is to a great extent powerless, for if his advice displeases he is dismissed. It remains for the school to educate the young student, and as usual the higher education must begin the work and the college pro- fessor must set the example of a living plain enough to be consistent with clear thinking. There need be no apology, therefore, for the introduction of such a " practical " subject into any college curriculum. There is plenty of theory be- hind it and much educational value in both methods and rea- soning. Definition vf Food. — Food is that which builds up the body and furnishes energy for its activities: that which brings within reach of the living cells which form the tissues the ele- ments which they need for life and growth. Only such avail- able substances can be called food, no matter what their chemical composition may be. Soft coal contains carbon and hydrogen and is food for the furnace, but is not available for the animal body. If for any reason a portion of the digestive tract is dis- eased, substances which under normal conditions would be food may not be nutritious. The nutritive value of a food depends upon the quantity of 124 AIR, WATER, AND FOOD. its ingredients which under normal conditions may be useful to the human organism. The term is not confined to any- one class ol food principles, as is commonly the case in news- paper articles, in which it is often stated, for example, that white flour and rice have very little nutritive value. We determine what chemical elements enter into the composition of the body by an analysis of the various organs and tissues. We learn what combinations of these ele- ments serve as food by determining those present in mother's milk and in foodstuffs which experience has proved to fur- nish perfect nutrition. From these studies it is apparent that about fifteen chemical elements are constant constituents of the human body; that about a thousand natural products are known to have food value; that of these, one hundred are of world-wide importance (see table, page 130), and that ten of them form nine-tenths of the food of the world. Food Principles. — While the foodstuffs present great vari- ety, the food principles may be grouped under four headings;, viz., nitrogenous substances or proteids, fats, carbohydrates, and mineral salts. Each group contains many members with minor but often essential differences. To make these sub- stances available, there is needed an ample supply of air and of water, — of water for solution and circulation, of air for the oxygen needed to liberate the stored energy of the food in the place where it will accomplish its purpose. Nitrogenous Substances. — Since, in some way as yet un- known to us, nitrogen is essential to living matter, such sub- stances as contain this element in an available form are of the first importance. Some, as albumen, are so closely allied to human protoplasm that probably they need only to be dis- solved to be at once assimilated. Others, as gluten and sim- ilar vegetable products, undergo a greater change; while still others, as gelatine, have a less profound but marked effect in FOOD IN RELATION TO HUMAN LIFE. 12 5 protecting the tissues from waste. Still other nitrogenous .substances, as the alkaloids, seem to affect the w^rz/^-tissues for good or ill. The enzymes, " ferments," in part, of the older nomencla- ture, are also highly nitrogenous substances present in some form in nearly all foodstuffs of natural origin. The nearer the composition of the food approaches that of the protoplas- mic proteid, presumably the greater its food value, since each cleavage, each hydrolysis, each step in the breaking down of the highly complex molecule, consisting of hundreds of atoms, is supposed to liberate the stored energy. Therefore it is not a matter of indifference in what form this essential is taken. So little is known, however, with scientific accuracy that stu- dents will find a fruitful field of research along these lines of investigation. Also together with this element, nitrogen, go •others, in small quantity to be sure, but evidently of great value. Such are sulphur, iron, phosphorus. One difference "between the several groups of proteids is seen in this com- bination with the metallic elements which seems to carry with it certain effects. Until greater progress has been made in determining the' availability in the organism of the various known substances, we must be content with a wide margin in the calculated quantities necessary for the daily efffciency, except in the very few instances of nearly pure substances, as white of egg. It is evident also that the manner of prepara- tion and the kind of mixtures used in food will affect most profoundly so unstable and complex a class of substances, and that only very general conclusions can be drawn from the work done as yet. One thing is certain, that the body cannot take nitrogen from that which does not contain it. There- fore a certain quantity of highly nitrogenous food should form a portion of the daily supply. It is usually held that the body seems to be sufficiently nourished when the food contains 126 AIR, WATER, AND FOOD. an amount of digestible proteid equivalent to about lOO grams of dry albumen per day for the average adult, although recent work has shown that this figure is probably too high. An excess appears to have a stimulating effect and overloads the system with the waste, since the end-products are not purely mineralized substances, as are carbon dioxide and water from the carbohydrates, but are compounds of an or- ganic nature, as creatin, urea, and uric acid, which have deleterious effects when accumulated in the system. A de- ficiency of nitrogen is made good, to a limited extent, by the protective agency of the other foodstuffs which offer them- selves for all the offices except the final one of tissue-building. Fats. — For this protective action, as well as for many other purposes, the fats are most valuable, and if they occur in about the same proportion as do the nitrogenous elements, the needs of the organism seem to be well met. Thus, in mother's milk, in eggs, and in meat from active animals these two are in nearly equal proportions, while in the cereals the fat is less; in nuts and in meat from fattened animals, as a rule, it is higher than the nitrogen. Little is known as to the varying food value of these fats from different sources. Certain physical conditions of solidity, melting-point, etc., seem to have more influence than mere chemical composition. What- ever the source, it is certain that the stored-up energy which is to serve the organism in cases of loss of income from any cause is in the form of fat, a form which is not subject to the action of agents which so readily decompose proteids and carbohydrates and yet is readily converted into available food whenever called for. That it is not absolutely necessary that the food should contain fat as such seems to be proved by experiment, but from the fact that all nearly natural food- substances do contain it, and that it appears to be more economical of human energy to take it from these foods than FOOD IN RELATION TO HUMAN LIFE. 12/ to manufacture it from the proteids and carbohydrates, we may safely assume fat to be an essential of the human dietary. That the equality in amount of fat with nitrogenous com- pounds is not essential is proved by the fact that the strong draft animals, as horses and oxen, take food -in which the per cent, of fat is not more than half as much as of proteid; never- theless it is present in the food of all animals and doubtless, in its turn, is protected by an excess of the third class of foodstuffs, the carbohydrates, characteristic of the vegetable kingdom — a class which in the final decomposition yield clean volatile products, water and carbon dioxide, and which, there- fore, do not clog the system so readily as do urea and other wastes. Carbohydrates. — The number of more or less well-defined substances under this head is legion: starches from scores of plants, sugars from as many more, gums, pectins, and dextrins, all with a certain food value, dependent prob- ably upon the utilization of the various mixtures with which they are taken into the alimentary canal. These foodstuffs are very liable to " fermentation," that is, to an acid decomposition which prevents their absorption by the delicate lining of the walls of the intestines and which causes digestive disturbance. The sugars, which are very soluble, and therefore liable to be present in excess, are es- pecially subject to this change. This class of food-substances is found in the diet of civilized man, free to choose, in an amount about equal to the sum of the other two classes, with a tendency to less rather than more. It may be said that sugar and fat increase over starch in the diet of a people of unrestricted choice, but it is not certain that the qualities of body which make for hardihood and resistance to disease are correspondingly increased. There is, indeed, much evi- dence to show that power of digesting vegetable foods indi- cates a general well-being of body conducive to long life. A 12 8 AIR, WATER, AND FOOD. ready adaptation renders possible the changes of habitat re- quired by civilization. Unless one is to be confined to a nar- row range it is wise to cultivate a strength of digestion as well as a strength of muscle, and for the best brain power we believe it to be more essential. Mineral Salts. — The fourth class, mineral salts, comes into the food largely from the vegetable substances eaten, for in these the union is an organic one readily assimilated. As we have seen, certain elements go with the nitrogenous portion, as, for example, in gluten and its congeners are found sul- phur and phosphorus. Potassium, found in barley, is a con- stant constituent of protoplasm, while sodium is found in blood-serum. A lack of vegetable foods seems to impoverish the blood-corpuscles. For children, a deficiency in lime ■causes serious disease. Sugar, olive-oil, corn-starch, and other prepared food-substances cannot take the place of asparagus, cabbage, carrots, etc. Heat of Combustion. — Until a more definite knowledge of the processes of metabolism (the transformations of matter and energy in the animal organism) is obtained the potential energy of food is calculated in terms of mechanical work — expressed in heat-units or calories. One Calorie (looo calories) is that amount of heat which is required to raise the temperature of one kilogram of water one degree centigrade, and if expressed in terms of mechani- cal work would enable one ton to be lifted 1.53 feet. For •example: one gram of fat burned under a steam-boiler would yield, if the heat were completely utilized, 9.3 Calories, and raise one ton 14.2 feet; 100 grams would yield 930 Calories and raise one ton 1423 feet. One gram of proteid or of carbohydrate is usually reckoned as yielding only 4.1 Calories. 480 grams would yield 1968 Calories and raise one ton 301 1 feet. A day's ration is frequently estimated as 100 grams fat -(- 480 grams FOOD IN RELATION TO HUMAN LIFE. 129 of proteid and carbohydrates, and if completely converted into mechanical work would yield that amount of energy which would suffice to raise 156 pounds (taken as the weight of the average human body) 56,755 feet. But a portion of this energy is used up in chemical processes, a portion in physical changes, and a portion is undoubtedly wasted; a portion of the food may be of no use or even detrimental to the body, so that not more than one-third of this work can be counted as available. Hence 18,918 feet may be counted as a theoretical day's work in mountain-climbing. The fact remains, however, that all experiments yet made go to show that within practical limits we are safe in using the heat of combustion (expressed in Calories) of any food- substance as a controlling measure of food values. The re- quisite number of Calories must, however, be obtained by the utilization of such substances as contain all the elements needed by the body, and in such ratio as has been found avail- able for the balance of nutrition. In' carrying on its multi- farious activities the body loses about 20 grams of nitrogen per day, which must be replaced by the same element in the food taken. Thus while the requisite number of Calories may be furnished by fat or starch, these substances alone will not suffice for complete nutrition. The nutritive ratio, or the proportion of nitrogenous to non-nitrogenous food, must be maintained in the proportion of i to 3, or at least i to 5. The following table of one hundred common food-mate- rials is arranged in the order of calorific or energy-giving power, but in considering the food value of any one substance its nitrogen content must also be considered, and such com- binations made as will yield the requisite elements for a well- balanced ration. From even a cursory examination of the table it will be seen how widely some of the foodstuffs differ under dififering conditions of soil moisture, fertilization in the case of plants. I30 AIR, WATER, AND FOOD. COMPOSITION OF SOME COMMON FOOD-MATERIALS AS PURCHASED, I. Fuel Value 3000-4000 Calories per Pound. Food-material. Refuse. Water. Nitroge- nous Substances. Fat. Carbo- hydrates. Per cent. Per cent. 11. o Per cent. I.O Per cent. 85.0 icx>.oo 83.0 80.3 to 94.1 70.7 to 94.S 63.4 Per cent. 9-5 0.3 to 12.2 4.3 to 21.9 2.5 1.2 0.2 to 5.0 I.I to 7.5 16.6 Salt fat pork Walnuts (shelled) 16. 1 II. Fuel Value 2000-3000 Calories per Pound. Bacon Cheese (American pale). Chocolate Doughnuts Mutton flank (fat) Peanut butter Sausage (farmer) 8.7 18.4 31.6 1.5 to 10.3 II o to 25.8 28.9 2.1 22.2 9-5 28.8 12.5 to 13.4 5.1 to 7.6 10.7 29-3 27.9 59-4 35*9 47.1 to 50,2 16.4 to 25.7 59.8 46-5 40.4 0'3 s6.8 to 33.8 45.8 to 63.2- III. Fuel Value 1500-2000 Calories per Pound. Barley (pearled) Beans (dried) Cake average (except fruit).. Candy Cheese (Neuchatel) Corn-meal Corn-starch Crackers (average) Fat meats Gelatin Ham (smoked, medium fat). . Infants' and invalidsWoods.. Macaroni Oats Peanuts Peas (dried) Pop-corn. Rice Rye flour Sugar (granulated) Wheat (entire) flour Wheat flour (white bakers')., Wheat (shredded) Zwieback II. 7 4.5 to 28.4 g.8 to 12.9 9.6 to 15.5 19.9 4.0 42.7 to 57.2 8.8 to 17,9 10. o 6.8 38.3 13.6 27.3 to 42.5 2.4 to 12.3 7.0 to 12.3 7.8 6.9 6.9 to 15,0 4-3 9.1 to 14.0 II. 9 to 13.6 6.4 to 13,1 lO.I to 13.3 7.2 to 10.7 5.0 to 7.7 * Including fibre. 7.0 to 10. 1 19.9 to 26.6 6.3 15. 1 to 22.3 6.7 to II. 6 10.7 13.0 84.2 10.2 to 21.9 2,0 to 22.5 7.9 to 16.6 16.5 19-5 20.4 to 28.0 10.7 5.9 to 11.3 4.9 to 8.8 12.2 to 14,6 10.3 to 14.9 9.6 to II. 4 8.6 to II. 7 0.7 to 1.5 1.4 to 3.1 9.0 22.3 to 32. s 1.0 to 5.3 36.8 O.I 24.5 to 39.9 0.3 to jo.g 0.0 to 4.9 7-3 29.1 0.8 to 1.3 5° 0.1 to 0.7 0.2 to 1.3 77.3 to 78.1*^ 57.2 to 63.5* 633 96.0 0.2 to 2.9 68.4 to 80.6*" 90.0* 71.9* 1.5 to 2.1 1.9 to 2.0 1.3 to 1.6 8.1 to II. 3 66.9 to 89.4 67.2 to 78.4*" 66.5* 18.5 58.0 to 67.4* 78.7 75.4 to 8i.g* 77.6 to 80.2* 100 69.5 to 77.0* 70.3 to 75.5 75.0 to 79.7* 72.1 to 74.2 IV. Fuel Value 1000-1500 Calories per Pound. Apples (dried) Bread (white) Corn-bread Dates Figs Fresh pork (ribs and shoulder). Medium fat mutton and beef... Mince-meat (commercial)..,,,. Mince-meat (home-made) Pies Prunes (dried) Raisins Sandwiches Sardines (canned) Salt mackerel 15.9 to 20.3 14.4 to 27.8 15.0 10. o 5-0 22.9 8.6 to 47.4 35-3 28.4 to 48.0 13.8 II. 6 to 25.0 40.T to 43.6 38.0 to 44.9 27.7 54.4 44.9 19.0 131 44.9 53.6 32.5 FOOD IN RELATION TO HUMAN LIFE. 131 COMPOSITION OF SOME COMMON FOOD MATERIALS. — Continued, V. Fuel Value 500-1000 Calories per Pound. Food-material. Refuse. Water, Nitroge- nous Substances, Fat. Carbo- hydrates. Beef (round) Beef (sirloin steak). Chicken (fowls) — Cream -Eggs Herring (smoked) . . Meats (lean) Olives Salmon (fresh). .. . Salmon (canned)... Tapioca pudding. . . Tongue (beef) Turkey Veal (breast) Per cent. 8.5 12.8 x8.o to 42.7 II. 2 44.4 0,5 to I I. 3 19.0 23.8 to 35.:. II. 7 to 16. g 9.2 to 55.3 17,1 to 32.4 15.7 to 25.4 Per cent. 62.5 54.0 38.3 to 53-7 74.0 65-5 19.2 59.9 to 69.2 52-4 45.0 to 51.2 54.6 to 58.2 52.0 to 71,6 32.4 to 69.2 41. 1 to 44.7 -18.5 to 55.7 Per cent. 19.2 16.5 IX. 5 to 16.0 2-5 11.9 20.5 18. t to 21.4 1.4 12.6 to 15.0 z8.6 to 20.2 2.8 to 4.2 7.8 to 20.2 15.8 10 16.8 14.2 to 16.9 Per cent, 9.2 16.1 6.9 to 31.5 18.5 9-3 8.8 7.8 to 14.2 21.0 6.6 to 9.5 5.6 to 9.8 2.3 to 4.8 0.7 to 15.3 5.91025.5 9.4 to 12.8 Per cent. 4-5 3.5 21.9 1038.1 VI. Fuel Value 400-500 Calories per Pound. Beans (canned red kidney). Calf s-foot jelly Salt cod (boneless) Succotash (canned) Sweet potatoes 72.7 77.6 54-8 71.4 to 79.9 SS-2 7.0 4-3 27.7 2. 9 to 4.4 1-4 0.7 to 1.7 0.6 18.5 17.4 14.9 to 23.4 21.9 VII. Fuel Value 300-400 Calories per Pound. Bananas Butter beans. Fish (fresh) . Grapes Hash Milk Potatoes 35.0 50.0 25.2 to 46.0 25.0 48.9 29.4 46.1 to 49.1 58.0 80.3 87.0 62.6 0.8 4-7 II. 9 to 12.0 I.O 6.0 3-3 1.8 0.4 14-3 0.3 14.6 1.8 to 5.9 1.2 14.4 1-9 9-4 4.0 5-0 0.1 14.7 VIII. Fuel Value 200-300 Calories per Pound. Apples Chicken (broilers). Cranberries Onions..- Oysters (solid) Parsnips Pears 25.0 31.4 to S5.I 20.0 10. o 63-3 44.6 to 52.4 87.6 to 89.5 78.9 83.2 to 92.4 66.4 76.0 0-3 9.0 to 15.7 0.4 to 0.5 1.4 4.5 to 7.3 1.3 0.5 0-3 I.I to 1.8 0.4 to 0.9 0-3 0.5 to 1.8 0.4 0.4 10.8 IX. Fuel Value 100-200 Calories per Pound. Beets Cabbage Carrots Green corn Lemons Oranges Soups (canned) Spinach Squash Tomatoes (canned). 20.0 15.0 20.0 61.0 30.0 27.0 70.0 77-7 70.6 29.4 62.5 63-4 91.0 to 92.8 gz.6 to 92. 8 44-2 92.5 1097.9 1-3 1.4 0.9 1.2 0.7 0.6 2. 9 to 5.0 1.8 to 2.4 0.7 0.3 to 1.7 O.I 0.2 0.3 0.4 0-5 o.t 0.3 to 0.8 0.2 to o.s 0.2 O.I to 0.3 X. Fuel Value 10-100 Calories per Pound. Asparagus Bouillon (canned). Celery Cucumbers Watermelons 20.0 15.0 59-4 94.0 96.5 to 96.7 75.6 81. 1 37-5 1.7 to 2.6 0.9 0.7 0.2 0.2 0.0 to 0.2 O.I 0.2 O.I 9.3 to 10.9 8.9 1.5 to 6.3 10.8 12.7 7.7 4.8 7-4 7-7 5-9 8.5 0.6 to 5.7 3.1 to 3.4 4.5 1.4 to 8.1 3-3 0.1 to 0.3 3.6 2.6 2-7 132 AIR, WATER, AND FOOD. and of fatness or leanness in animals, of method of prepara- tion or of combination in cooked foods. Therefore examinations of materials are imperative if there is to be any basis of calculation. In an institution where, for instance, flour forms two-thirds of the daily ration, if it contains the lowest per cent, of nitrogen it may not furnish sufficient proteid for a well-balanced ration, or if the meat used is very lean there may not be fat enough for the best nu- trition. The great variation in the proportion of water leads to many surprises, and the amount of unedible material is to be considered. The uneducated provider buys oysters under the impression that he is furnishing food of high value, and does not digtinguish between potatoes and rice. In the present state of our knowledge, the best use to which we can put such tables and analyses is as a check against gross errors of diet, which are found with alarming frequency especially among children and students, those who can least afford to make them. References will be found in the Bibliography to works for further study along these lines. Dietaries. — A dietary is simply a known amount of food of known composition per person per day, week, or month. What is called a standard dietary is such a combination of food-materials as shall furnish the amounts held to be neces- sary. The following are examples of such standard dietaries: Approximate Amounts required daily by Nitrog-enous, grams. Fats, grams. Carbohydrates, grams. Calories. rViilH of 6-Q 62 78 100 100 125 45 45 75 90 125 200 281 380 450 500 1593 1890 2665 3092 3725 Adult at moderate work Adult at hard work. . . (In feeding experitnents from 10 to 20 per cent, more must be allowed for waste and indigestibility.) FOOD IN RELATION TO HUMAN LIFE. 1 33 From the table on p. 130 may be selected such food as will give the required quantities in variety enough to suit any taste. That which the table cannot give is the percent, of each which, under any given condition, will be utilized by the person fed. The strength of the digestive juices, exercise, fresh air, the cooking, the mixing of the foods, the habits of mind as to food, the customs of the family, all influence this utihzation, so that other means must be resorted to in order to gain an idea of what is practicable. This is done by taking account of the food of persons free to choose ; of those in different countries, in different circumstances, and using a great variety of materials. Since Voit made his standard dietary in 1870, many hundreds, at least, have been so gathered in the United States alone — more than two hundred since 1886. All the information thus gained goes to confirm the theoretical standard, and also to show how much depends upon suitable preparation and combination. These last two things help each other. As food is ordinarily prepared, about 10 per cent, must be deducted for indigestibility in a customary mixed diet, and about 10 per cent, more for the refuse or waste of food as purchased, so that of the total pounds of meat, vegetables, and groceries some 20 per cent, is of no final service in the body. It is immaterial whether this amount is subtracted from the final calculation or whether the higher figures be taken, that is, whether 125 grams of proteid as purchased or 100 grams final utility is used. There will be an unknown limit in either case. According to late experiments 100 grams of proteid is high. The waste of fats is less in propor- tion as the dietary is a restricted one. Knowledge of Food Values Necessary. — The most serious aspect of the food question is that the taking of it is volun- tary, not, like air, a necessity beyond control, and that the 134 AIR, WATER, AND FOOD. most fantastic ideas are allowed to rule. The day-laborer is in little danger, since his food demand is made strong by out- of-door exercise; but the student who shuts himself up in hot, close rooms, and who does not look upon food as his capital, but only as a disagreeable task or an amusement, is in great danger, as is he who, having heard that one can live on a few cents a day, proceeds to try it without knowledge, and suffers a loss of efficiency for years or for all his life. It is not nearly so difficult to acquire a working knowl- edge of food values as of whist or golf, so that on entering a restaurant a suitable menu may be made up within one's al- lowance. It is only necessary to correct prevailing impres- sions and reinforce one's experience. Figs, dates, raisins, and prunes are apt to be regarded as luxuries instead of as rich food-substances of a most di- gestible kind when freed from skin and seed. Nuts are a much neglected form of wholesome food, admirably suited to a winter table from their richness in fat, and also furnish- ing muscular energy, as is seen in the agile squirrel, and is proved by many human examples. With nuts, however, must be taken fruits or other bulky foods, to balance the con- centration. The somewhat compact and oily substance must be finely divided and freed from its astringent skin. In distinction from these rich foodstuffs, we find oranges, apples, etc.; the usual garden vegetables, asparagus, lettuce, etc., which, while they fill an important place in the dietary, add little directly to the energy of the body and need not be considered except as, by their flavor or aesthetic stimulus, they add to the efficiency of the rest. In looking over some housekeeping bills of a family not given to extravagance, but with a well-stocked market at hand and no especial check on the cook's orders, it was found that the ten staple articles cost 50 per cent, of the whole, the FOOD IN RELATION TO HUMAN LIFE. 1 35 really nutritious foods of higher price 20 per cent., and the mere accessories 30 per cent. These accessories are truly cheaper than doctors' bills, and a high rate of efficiency in human mechanics is worth attain- ing even at a considerable expense. The chief difficulty lies in a subject outside the scope of these pages, namely, waste of the expensive or less nutritive material, or substitution of these for others more nutritive. For instance, a meal of lettuce dressed with oil, eaten with bread and cheese, fulfils all the requirements of nutrition, and may cost five cents. The same food value from sweetbreads, grape-fruit, etc., might cost a dollar. CHAPTER IX. THE PROBLEM OF SAFE FOOD. ADULTERATION AND SOPHISTICATION. Where food-materials are abundant, of known value,, and without foreign admixture, there the general welfare of the people is satisfactory, barring sanitary errors in other directions. Where opportunity is given for the unscrupu- lous dealer to increase his gains at the expense of the health and lives of the people, children -especially, it is eagerly seized upon, and milk diluted with water, colored with coal- tar products, and preserved with borax or formaldehyde is furnished so long as the community is ignorant enough to- permit it. In frontier towns taking-powder containing alum is still sold, and in many places ginger containing 50 per cent, of turmeric, buckwheat, and redwood sawdust is on the market.. The average buyer is content to go by familiar appear- ance, and is quite satisfied if he sees a dead bee in his honey and the usual form and color in his coffee-bean. Scientific skepticism has not yet touched the purchaser of the essentials of life, and manufacturers are not slow to perceive and tO' take advantage of his credulity. It is not necessary to resort to poisonous material or to directly deleterious substances; it is only necessary to mix a cheaper but equally wholesome- material with a favorite article, or to substitute it altogether. To meet the craving for variety it is only necessary to make- 136 THE PROBLEM OF SAFE FOOD. 13;- slight changes in the outward appearance of common sub- stances and then to advertise widely the discovery of some new process by which the food value is increased tenfold. In order that the community may be supplied with safe food,, as well as with safe water, the education of the individual is important, even essential, since food is even more completely under individual control than is water. It is true that State and municipal regulations exist and should be enforced as to palpably noxious substances and those that are notoriously fraudulent. The relation of the citizen to these is the same as to the purity of the water-supply; it is his duty to uphold the hands of the authorities in the necessary expense of in- spection and prosecution. Adulteration and Sophistication. — To adulterate is defined as to debase, " to make impure by an admixture of baser materials, as in the case of coin, liquors," etc. As an explanation of sophistication, which is often used as synonymous with adulteration, this quotation is given: " These men have obscured and confounded the nature of things by their false principles and wretched sophistry." (South.) The sophists were educated and intelligent men, and per- suaded the people by specious reasoning. The modern " pure food " manufacturer is a sophist who, with great skill and by the aid of the well-paid expert, persuades the general public that he is their benefactor in that his chemists have penetrated nature's secrets, hidden from the ordinary man, and therefore that he is able to ofifer them long life and pros- perity at so many cents the pound. Although the words " adulteration " and " sophistica- tion " are in a degree synonymous, yet there is a distinction which seems borne out in legal practice. To adulterate the coin of the realm or the liquor of the bar with a baser metal 138 AIR, WATER, AND FOOD. or an imitation whisky is a heinous ofifence. So is the mix- ture of milk with the baser article, water, which thereby low- ers its food value. But the " wretched sophistry " which obscures the nature of things on a package of prepared food misleads more persons and inflicts more injury upon the com- munity than the other, yet goes unrebuked. The most barefaced assertions are printed in magazines, and " pure- food shows " only whet the appetite for something new. Predigested Foods. — This craving for something new to stimulate a jaded appetite already spoiled by endless variety and bad combinations has led to the manufacture of a cereal preparation for nearly every day in the year. No better com- mentary on the laziness or wilful ignorance of American pro- viders could be made than this. Little do the people know about wheat or cooking if they suppose that grain can be changed by manipulation in any kind of machine so as to give greater food value than was contained in the grain. While it is true that some of these preparations are far better than the half-cooked grains found on so many tables, the fact re- mains that it is the cook and not the substance which is poor. The false statements on food packages of all kinds are so absurd that they would defeat their own purpose were they viewed in the light of common sense. It is not always best to have food which is too easily digested. " The excessive fear of indigestible food which prevails among the wealthier classes may lead to universal debility of the intestinal muscular walls." * This fear and the lack of ■exercise is working mischief especially among students. Colleges do not educate along the fundamental lines of health. To be sure, gymnasiums are becoming common, and sometimes exercise does correct bad habits of eating, but * Bunge: " Physiological Chemistry" (trans.), 1890, 83. THE PROBLEM OF SAFE FOOD. 1 39 a knowledge of food principles should go along with it in order that the greatest efficiency may be obtained. A predigested food is quickly absorbed into the circula- tion, and hence a small quantity causes a sensation of fulness and satisfaction which, however, soon passes away and a faintness results. This is especially true of the sugars and dextrins. Frequent meals should go with these easily ab- sorbed foods. This rapid digestion is the cause of much pernicious eating of sweets between meals, which satisfies the appetite for the time being and prevents substantial quantities of other foods being taken at the time they are offered. A lack of responsibility for the energy which we owe to the world, an inconsiderateness for the suffering we bring upon others, leads us to walk upon the thin ice of mere whim- sical eating. Extent of Adulteration. — The proportion of food adul- terated in the sense of harmful additions has always been comparatiYcly small; probably in no community has it ever reached lo per cent, of the food sold. In States which have legal penalties it is undoubtedly below 5 per cent. Such statements as that 90 per cent, of the food offered in any market is adulterated can only mean, if true at all, that 90 per cent.- of all the names of materials sold in shops cover more or less fraudulent mixtures. For instance, flour is rarely adulterated; pepper, ginger, and mustard are nearly always heavily adulterated. For one pound of these substances sold, 1000 pounds, or more, of flour go out from the store. Looked at in this lieht the sub- ject assumes quite another aspect. A canvass of the State of Massachusetts in 1879,* before the passage of the law of * Ellen H. Richards: " The Adulterations of some Staple Groceries." Ann. Rep. Mass. State Bd. Health, 1879 (Supp.), 55. I40 AIR, WATER, AND FOOD. 1882 and subsequent restrict/ions, showed that the staple arti- cles were very httle adulterated; that then, as now, it was the condiments, of which only a small quantity is used at any one time, which showed the highest per cent. The influence of a stringent law fairly well enforced is seen in the decrease of the adulteration of cream of tartar in samples examined, which fell from 42 per cent, in 1879 to 5 per cent, in 1898. Of suspicious samples of foods, exclusive of milk, exam- ined in the latter year by the State of Massachusetts, only 13.4 per cent, were adulterated. Since only suspected arti- cles were taken by the inspectors, the actual per cent, must be far below this. Estimated on the total quantity sold, it is doubtful if more than one per cent, of food which can come under the law is adulterated in Massachusetts to-day. The records of localities without the legal protection of inspec- tion is not quite so good as those of the five States which have stringent laws, and yet it is doubtful if harmful adulteration is very prevalent. Trade Names. — Much of this so-called adulteration de- ceives only the ignorant buyer. " Strictly pure " is a well- understood trade term and means " with a certain per cent, of addition"; "pure" has a greater addition, as "pure" spices. Of patent and proprietary preparations, and those covered by a trade name, the sale is on the increase, so that the statement is justified that the frauds in foodstuffs are mainly commercial, and not harmful in a direct way. Among the most serious are those packages claiming to consist of gluten and to furnish a substitute for hearty food and those so largely used by students. " Gluten flour " is not what the uninstructed might think, that which is very rich in gluten, but is only a whole wheat, possibly a very little richer in nitrogen than ordinary flour. " What's in a name " is well THE PROBLEM OF SAFE FOOD. I4I tmderstood by sardine-can-ners, bread-makers, restaurant- keepers, and grocers. The dealer caters to the people and goes no farther than they readily follow him. Special Cases. — The use of canned goods brings certain dangers in the dissolved metals from the cans or from the solder, also from a careless habit of allowing food to stand in the opened tins. The liking for bright green pickles and peas leads to coloration by copper salts. The demand for cheap jellies has developed a new industry. The parings and cores of apples prepared for drying are cooked, strained, col- ored, and flavored to make to the eye a fair imitation of rasp- berry, currant, and grape jelly, sold for 7 to 10 cents a tumbler. Flavoring extracts offer a fertile field for chemical su'b- stitutes. The excessive use of preservatives is caused by the crav- ing for food out of season and out of place: for summer fruit in winter, for oysters a thousand miles inland, and by the urban demand for fresh milk, which must be brought at least one hundred miles and can be delivered but rarely under thirty-six hours from the farm. The difficulty even then of furnishing enough leads again to the dilution by water, either indirectly through the breed and feed of the cow or by direct addition. Again, the extensive demand for cream tends to encourage the topping of the milk. With this increase in quantity and in time of keeping fresh food comes also the danger of transmission of disease, which constitutes one of the worst dangers in food. It hap- pens with considerable frequency that thirty or forty cases of scarlet-fever are traced to a single farm; that typhoid-fever also is disseminated in the milk. Cream and butter are also subject to suspicion. During the years 1890 to 1899 nine 142 AIR, WATER, AND FOOD. experts reported on 339 samples of butter and found tubercle bacilli in 21 per cent, of them. The dangers in butter are largely increased by the prac- tice of " doubling " the yield by a treatment of milk with rennet and salt, " black pepsin," or other nostrums, which works a large proportion of curd into the butter, but also renders the mass much more liable to decomposition. Since the food value of curd is only half that of fat, and since it also carries more water, the fraud is serious on both sides. In many ways the bread-supply of a city needs looking after from a sanitary and economical point of view quite as. much as the milk-supply. It is not at all improbable that, first and last, as much disease is caused by bread from un- sanitary bakeries, by badly baked bread, and by unduly light bread which has not sufficient food value, as by any other cause. Summary. — The chief dangers in food are from wrong proportions of proteid, fat, and carbohydrates, from ferment- able and irritating decompositions, from bad methods of cooking and unsuitable combinations, from transmission of micro-organisms either by exposure to dust or by contact with filthy hands or vessels, to a favorable medium for the growth of pathogenic germs. From this hasty survey it will be seen how little danger to health is incurred if only reasonable care is taken and if the always doubtful articles are avoided. Take, for instance, that most commonly adulterated class, spices. Who will say that it may not be better to eat corn and buckwheat and ground peas than pure pepper? Rice is certainly a more wholesome food than ginger, and starch than soda. Glucose is even more easily absorbed than cane- sugar. These are cases of frauds on the pockets, but possible blessings in disguise for the stomachs. When any com- THE PROBLEM OF SAFE FOOD. 1 43 munity is so ignorant as to permit of such gross, out-of-date adulterations as alum in baking-powder, and gypsum in cream of tartar, they deserve to suffer. It is knowledge on the part of each intelligent citizen which will mend matters, even if it is only that kind of empirical knowledge that one is forced to learn in relation to electricity and steam in order to live in a modern house. The natural food-materials are so complex in composi- tion that one may well be led astray by outward appearances, and substances of the same proximate composition present themselves under so many guises that when the markets of our cities offer the food of all the nations of the earth, how shall the buyer know what he is getting? To outward seem- ing, the potato and the banana have little in common, but their food value is almost identical, with the advantage on the side of the banana. The general public is alarmed over newspaper reports not wholly disinterested, or is " instructed " by paid agents. People become accustomed to certain terms which are held up as scarecrows, and learn to look to the daily press rather than to the agricultural college for knowledge as to new or dangerous foods. The remedy lies in their own hands. Every high-school laboratory should contain a case of samples and charts of values, and it should be considered just as impor- tant for good citizenship that the child should have the tools of health put in his hands as that he should learn about bank- ing and interest. His bank account is his health. His in- terest is his daily efificiency. So rapidly do new substances come upon the market that it is of little use to put into a general text-book definite statements of the quality of many foods. A baking-powder or a spice which is honestly made to-day may next week pass 144 AIR, WATER, AND FOOD. into the hands of unscrupulous dealers who please the public and thereby salve their consciences. To furnish what the people think they want has been the rule from the days of an earlier generation of grocers, who divided a barrel of cooking-soda in halves and set one-half ■on one side of the store for " saleratus " and the other on the opposite side for soda, so that there should be no suspicion in the mind of the customer that the packages came from the same barrel, and yet each might satisfy his individual prefer- ence. We wish to dwell more strongly on the ethical and hy- gienic side of the question than on the financial. Evil-doers thrive only when reputable people countenance them. Adulterated food will be offered only so long as buyers eagerly take it. " Those that hide can find." If science is called upon to sophisticate food, science can find out how it is done. The chemist should be so grounded in' morals as to refuse to sell his knowledge for a manufacture which is dangerous to health. We have tried to show that it is not very frequently the case that the manufactured article is of itself directly injurious, only in its misuse. It may be a question which is the cheaper, to build a sub- way or to kill a few persons now and then 'by the surface cars. So in food, it is necessary either to put an elaborate machinery of inspectors and chemists and courts in motion, at great expense, or to educate the people at large so that each will be his own inspector. The latter is more in har- mony with American practice, but the economic conditions in other directions are pressing the food-supply into the same channels as clothing, furniture, and transportation; that is, away from individual control as to manufacture. This neces- sitates individual knowledge in purchasing if satisfactory re- sults are to follow. THE PROBLEM OF SAFE FOOD. 145 This knowledge is now easily obtained through the city, State and government laboratories, and their publications dre accessible to all who can read and write. There is, there- fore, no excuse for general ignorance and credulity as to trade preparations of foods, any more than for the degrading habit of purchasing patent medicines to remedy the ills caused by the misuse of food. Both together form the sad- dest commeptary on human weakness and lack of rational thought. CHAPTER X. ANALYTICAL METHODS. In the discussion of the methods employed for the ex- amination of food-materials, only a few typical substances have been considered, and the processes given are such as to bring into prominence the scientific a,spect rather than the technical detail of the subject; at the same time it is hoped that a sufficient variety of methods is given to enable the student to gain considerable experience in the necessarily short time which can be allotted to the subject. Both on account of its importance as a food-material and on account of its availability for the various tests, milk has been chosen as a type of animal food; moreover, it may be made to serve as an excellent example of the changes to which food-materials are liable through the growth of the micro-organisms. The analysis of milk includes determina- tions of specific gravity, water, or total solids, ash, fat, nitro- gen, and sugar, together with the separation of casein and albumin, the determination of the products of putrefaction and fermentation, namely, ammonia and acidity, also the de- tection of preservatives and coloring matters. Wheat is taken as a type of vegetable foods. The ex- amination which may be made of this class includes the de- termination of moisture, ash, fat, nitrogen and proteids, starch, cellulose, and the products of peptonization and saccharification. 146 FOOD: ANALYTICAL METHODS: MILK. I47 The nature and composition of the various fats and oils is briefly illustrated by the examination of butter and the de- termination of the principal constants of the butter-fat. The results of fermentation are illustrated by the deter- mination of alcohol in beer, wine, meat extracts, patent medi- cines and " temperance drinks," flavoring essences and the like. The determination of the acidity, of the " extract," and of nitrogen is also sometimes desirable. Condiments, spices, tea, and cofifee are generally exam- ined by means of microscopic tests, but adulterations of these, as of most common groceries, affect the health less than the pocket. Text-books on food adulteration furnish sufficient information on these points. (See Bibliography, P- 2I3-) MILK. General Statements. — Milk is an emulsion of fat-globules with casein and other nitrogenous bodies, mineral salts (probably in combination), sugar and water. The average percentage composition of the more important varieties of milk, as found by recent observers, is summarized in the fol- lowing table: Water. Sugar. Proteids. Fat. Ash. Cow 86.90 4.80 3.60 4.00 0.70 Human 88.75 6.00 1.50 3.45 0.30 Goat 85.70 4.4S 4.30 4.75 0.80 Ass 89.50 6.25 2.00 1.75 0.50 Mare 90.75 5.70 2.00 1.20 0.35 Sheep 80.80 4.90 6.55 6.85 0.90 In connection with this table should be noticed the high proportion of sugar and low proportion of casein and ash in human milk as compared with cow's milk. The former is not readily curdled, the casein never separating in a compact clot 148 AIR, WATER, AND FOOD. ■which settles to the bottom, a difference which is attributed to the lower proportion of fat to casein.* The average composition of 120,540 samples of cow's milk, extending over a period of eleven years, and the aver- age composition of 14,135 samples of cow's milk for the year 1898, analyzed directly on arrival of the milk from the farm, is given by Vieth and Richmond f as follows : Average, 1898. Average of eleven years. Specific gravity 1.0320 Total solids 12.73 12.90 Solids not fat 8.90 8.80 Fat 3.83 4.10 An examination of milk as regards its healthfulness usually consists in determining what changes, if any, have taken place in its constituents due to the growth of micro-organisms. Milk is a natural culture medium for the growth of micro- organisms and they increase in it with almost incredible rapidity. These changes which take place are called " fer- mentations." The two most common are the acid and the alkaline. Acid Fermentation. — Milk-sugar is converted wholly or in part into lactic acid under the influence of a class of organisms of which bacillus acidi lactici is the best known and is generally regarded as predominating. The extent to which this change has taken place is shown by the test for acidity. Alkaline Fermentation. — In the alkaline fermentation the albumin and casein are decomposed with the formation of ammonia and other intermediate nitrogenous products, some of them of a poisonous character, as is shown by the preval- ence of cholera infantum when such decomposed milk is used, * Lehmann and Hempel: Arch. Physiol., 56 {18^4), 558. f Analyst, 17 {i8g2), 84; 24 (i8gg), iq-j. food: analytical METHODS: MILK. 149 and by cases of poisoning by ice-cream, etc. This fermenta- tion generally occurs simultaneously with the acid fermen- tation, but at first is much less active; at a subsequent stage, however, the alkaline fermentation becomes more pro- nounced, and in certain cases may completely dominate the other fermentations. Other Fermentations. — Butyric acid fermentation may be a result of the action of one or several groups of bacteria upon the glyceride of butyric acid. This action sets free the butyric acid in part and the fat becomes in time " rancid," but this change takes place, as a rule, more slowly and is not so com- mon as the others. The production of koumiss is an instance of an artificially incited change. Various other fermentations occasionally occur which cause a slimy appearance or a bitter taste. Various colors may be imparted to the milk by the presence of chromogenic or color-producing micro-organisms. The student is referred to the various journals and to text-books on dairy bacteriology for accounts of these less important changes. Sampling. — In all manipulations with milk the importance of thorough and frequent mixing, not shaking, cannot be too strongly emphasized; this is best accomplished by pouring it from one vessel to another. This will be found necessary even when the milk has been standing for only a few minutes, on account of the rapid rise of the cream. The apparatus used to contain or to measure milk should be thoroughly washed out as soon as possible. PHYSICAL TESTS. Specific Gravity. — Take the specific gravity in the usual manner by means of a hydrometer or by the Westphal bal- ance, at 15" C. If the temperature of the milk varies from ISO AIR, WATER, AND FOOD. 15°, the reading may be corrected by means of Table IX, Ap- pendix A. Take a reading of the lactometer at the same time. In this instrument the minimum density for whole milk is fixed at 100, corresponding to a specific gravity of 1.029. Notes. — The specific gravity of milk is, in the main, a func- tion of two factors, namely, the percentage of solids not fat and of the fat. The former raises it; the latter lowers it. The determination of the specific gravity alone is not to be relied upon as an absolute index of the purity of the milk. The specific gravity varies in general from 1.029 to 1.034, and in most cases of normal and well-mixed milk from several cows the specific gravity will lie between 1.030 and 1.032. Opacity. — The white color and opacity of milk are largely due to the presence of the suspended fat-globules and of the casein in colloidal form. The influence of the latter is shown by the fact that the color of milk is not greatly changed after it has passed through a centrifugal separator which removes practically all of the fat. The degree of opacity and the percentage of fat may be determined by means of Feser's lactoscope, the modus operandi of which is given with that instrument. Another instrument of like prin- ciple is Heeren's pioscope,* which consists of an ebonite disk with a raised rim; a drop or two of milk is placed upon it, the painted glass cover placed over it, and the color of the milk matched with one of those on the cover. Cream. — Fill the creamometer, an elongated test-tube with graduations near the top, to the zero mark with the milk, add three drops of a solution of methyl violet, mix and put away in a cold place. After twenty-four hours read off the percentage of cream. Notes. — The rapidity with which the cream rises indicates * Repit. f. Anal. Chem., 1881, 247. food: analytical methods: milk. 151 whether sodium carbonate has been added, its action being to retard the rise of cream so that the milk is never blue. Should the cream separate very quickly and the milk be blue, the indication is that water has been added or that the milk is of poor quality. The method is only approximate and does not give the amount of fat. The methyl violet is added to render the reading sharper, as it does not dissolve appreciably in the cream. Cream contains most of the fat of milk with a small proportion of the other constituents. loio samples of- cream gave an average of 48.3 per cent. fat. CHEMICAL TESTS. Reaction., — Normal milk gives the amphoteric reaction, that is, it turns delicate litmus both red and blue. This is due to the presence of neutral and acid phosphates of the alkalies. The reaction of the milk soon becomes acid, however. Acidity. — Measure 5 c.c. of milk into a small beaker, N ■dilute with so c.c. of water, and titrate the acid with — -^ ID sodium hydroxide, using phenolphthalein as an indicator. Express the acidity in degrees, considering each tenth of a cubic centimeter of sodium hydroxide one degree. Notes. — The acidity of milk is due to the fermentation of milk-sugar and the production of lactic acid. Under favor- able circumstances this change may take place with consid- erable rapidity. For example, six hours after milking the acidity may be fourteen to twenty-five degrees; forty-eight hours after milking it may reach one hundred degrees. When the acidity reaches twenty-three degrees milk coagulates on boiling.* An example of the rate of change is given in the following table: f * Thorner: Analyst, l6 (i8gi), 200. t "Thesis," Ethel B. Blackwell, M.I.T., 1891. 152 AIR, WATER, AND FOOD. r.,„ Acidity, Sugar, "*y • c.c. Degrees of Rotation. 1 2.2 25.2 2 5-5 23-1 3 II. O 21.6 6 13.2 14-2 7 15-0 9-4 8 16.3 7.8 g 17.2 1.2 Alkalinity. — Directions. — Measure into a 750-c.c. round- bottomed flask 25 c.c. of the milk. Add 350 c.c. of ammonia- free water and 0.5 gram of sodium carbonate and distil over about 200 c.c. into a flask containing about 20 c.c. of dilute sulphuric acid (1:40). Neutralize the distillate with sodium carbonate and redistil it, receiving the distillate into 15 c.c. N (measured) of — hydrochloric acid. Titrate the excess of N acid with — sodium hydroxide, using methyl orange or cochineal as an indicator. Notes. — In the alkaline fermentation the proteids of milk are decomposed through the growth of micro-organisms. Ammonia, or some substance which yields ammonia on dis- tillation, is formed and tends to neutralize the lactic acid. On the other hand, abundant acid tends to check the growth of the alkaline ferments. It depends upon certain conditions of seeding and of temperature as to which gets the best start in the race. It is to the alkaline fermentation that most of the danger in using unsterilized milk is due. The second distillation which is made is for the purpose of converting into ammonia any amines which may have been formed during the first distillation. Total Solids. — The determination of total soHds is best carried out in a platinum dish having a flat bottom about 2^ inches in diameter. Small dishes of aluminum or blacking- box covers answer very well, but of course cannot be ignited to obtain the ash. Directions. — Weigh the platinum dish and add about 5.1 food: analytical methods: milk. 153 grams to the weights on the balance-pan. With the burette pipette deliver 5 c.c. of the well-mixed milk into the dish and weigh the whole as rapidly as possible to the nearest milli- gram. Evaporate the milk to dryness on the water-bath and then dry it in the oven at 100° to a constant weight. Some analysts recommend drying at 105" for three hours instead of to constant weight. Notes. — It is important that the milk should be in the form oi a thin layer, so that the evaporation of the water shall take place as quickly as possible. Under these conditions the resi- due obtained is nearly white; but if the process be prolonged, it may have a brownish color from the caramelization of the sugar. Various analysts have proposed modifications of the pro- cedure as described above, such as drying on sand or asbes- tos, coagulation of the milk by absolute alcohol before evapo- ration, and so forth, but simple evaporation in an open dish is generally regarded as the most advantageous. Ash. — Directions. — Ignite the platinum dish containing the residue from the preceding determination at a low red heat until the ash is white or nearly so. In order to avoid too great a heat it is best to finish the ignition in a " radia- tor," as in the determination of the fixed residue in water- analysis. After weighing the ash, test it for carbonates by adding two drops of dilute hydrochloric acid. Effervescence in the ash is quite perceptible when carbonates are present in as small amount as 0.05 per cent. If desired, the hydrochloric acid solution of the ash can be used to test for boric acid as described on page 168. Notes. — If the temperature is raised too much during ignition, the results will be low on account of the partial vola- tilization of the chlorides of the milk; hence the process should be carried out at as low a temperature as will admit of the oxidation of the carbonaceous matter. 154 AIR, WATER, AND FOOD. The percentage composition of the ash of milk is given by Fleischmann and Schrodt * as follows: Per cent. Potassium oxide, JCaO 25'42 Sodium " NajO iO-94 Calcium " CaO • ■ • 21.45 Magnesium " MgO 2.54 Ferric " FejOs o.il Sulpliuric acid, SO3 4-il Phosphoric" PjOe 24.H Chlorine, CI i4-6o 103.28 Less oxygen corresponding to chlorine f 3-28 1 00. 00 The aoh of genuine cow's milk is free from carbonates and borates, and the ash soluble in water is about 30 per cent, of the total. Fat. — Since the fat is so important a constituent of milk, an endless variety of methods and modifications for its deter- mination have been devised. The processes which are in most general use may be divided into three classes: 1. Estimation of the fat by simple extraction of the milk, best dried on some absorbent material. 2. Volumetric estimation of the fat liberated by chemical treatment from the milk and collected by centrifugal force. 3. Estimation of the fat by extraction from the milk itself after solution of the casein by acid. A typical method from each class will be described in de- tail. (i) Adams' Method. — Directions. — Roll a strip of fat- free blotting-paper, 22 inches long and 2^ inches wide, into * Baumeister: "Milch und Molkerei-Producte," S. i6. f This correction is necessary because the metals are all calculated as oxides, when, as a matter of fact, a certain proportion are present as chlorides. FOOD: ANALYTICAL METHODS: MILK. 155 a rather loose coil and fasten it by a bit of copper wire. Hold the coil in one hand and carefully run on to the upper end of it 5 c.c. of milk from a burette pipette. Place the coil, dry ■end downward, in the water-oven and dry it for an hour. When dry remove the wire and place the coil in the Soxhlet extractor. If preferred, the strip of paper may be held hori- zontally in a frame and the milk run on to it. When dry the paper is rolled into a coil and extracted. Weigh the extrac- tion-flask, place in it 75 to 100 c.c. of 86° gasolene (petroleum ether) and connect the extractor with the condenser. After the coil has been extracted for about two hours remove the extractor, connect the flask with the suction if it is at hand, and distil ofif the gasolene under reduced pressure. The in- crease in weight of the flask gives the fat. Oxidation of the iat by too long heating should be avoided. Notes. — Absorbent paper exercises a selective action on the constituents of milk so that the fat is left on the surface of the paper, mixed with only about one-third of the non-fatty solids, and hence it is more easily extracted; further, owing to the greatly increased surface exposed, the extraction of the iat is practically complete. Ether may be used instead of gasolene, but care should be taken that the ether is perfectly dry, otherwise other sub- stances than fat, principally milk-sugar, will be extracted. On the other hand, substituted glycerides may not be dissolved out by ether. For these reasons the gasolene is to be pre- ferred as a solvent, although its action is considerably slower than that of the ether. Owing to the inflammable nature of the solvents em- ployed, it is best not to use a flame as the source of heat, but to heat the flask by means of a steam- or water-bath. In this laboratory small electric heaters about 4 inches in diameter are used and have been found safe and convenient. The com- plete apparatus is shown in Fig. 7. 156 AIR, WATER, AND FOOD. Another form of apparatus, devised by W. R. Whitney, which has been used with satisfactory results is shown in Fig. 7. — Apparatus for Fat Extraction. XI, Fig-. 8. It consists of an ordinary test tube, the lower part of which is heated by a steam coil. A coil of small brass tubing, carrying a stream of cold water, hangs in the mouth of the test tube and serves as a conden- ser. The paper coil hanging from the condenser is extracted by the use of about 10 c.c. of gasolene or ether. (2) Babcock Method. — Directions. — Measure 17.6 c.c. of the milk from a pipette into the long-necked, gradu- ated whirling-bottle. Measure out 17.5 c.c. of sulphuric acid (sp. gr. 1.83), and add it gradually to the milk, mixing the two thoroughly after each addition. Take care that none of the liquid spurts into the neck — —PAPER COIL ---t -GASOLENE O O-I-STEAM COIU Fig. 8. food: analytical METHODS: MILK. 1 5/ of the bottle. After mixing the milk and acid, and while the bottles are still hot, place them in opposite pockets in the centrifugal machine, in even numbers, and whirl them for six minutes, the large wheel making ■eighty to ninety revolutions per minute. Then remove the bottles and add hot water until the fat rises to the 8 mark on the stem. Again place the bottles in the machine and whirl them at the same rate as before for one minute. Then measure the length of the column of fat by a pair of dividers, the points being placed at the extreme limits of the column, the fat being kept warm, if necessary, by standing the bottle in hot water. If now one point of the dividers is placed at the zero mark of the scale on the bottle used, the other will indicate the per cent, of fat in the milk. Notes. — When the acid and milk are mixed the. mixture becomes hot from the action of the acid on the water in the milk and turns dark-colored on account of the charring of the milk-sugar. The casein is first precipitated and then •dissolved. The fat is thus separated in a pure state from the other constituents of the milk. The fat obtained should be of a clear, golden-yellow color, and distinctly separated from the acid solution beneath it. If the fat is light-colored or whitish, it generally indicates that the acid is too weak, and a dark-colored fat with a stratum of black particles below it indicates that the acid is too strong. The best results will be obtained by the use of acid of the strength noted above. A violet color is sometimes produced when the first por- tions of the acid and milk are mixed. This frequently indi- cates the presence of formaldehyde. (See p. i68.) (3) Werner-Schmid Method. — Directions. — Measure 10 c.c. of milk into a long test-tube of 50 c.c. to 60 c.c. capacity and add 10 c.c. of hydrochloric acid (sp. gr, 1.20). Place 158 AIR, WATER, AND FOOD. the tube in boiling water and heat, with frequent shaking, until the hquid turns dark brown, which generally requires about ten minutes. Do not heat it so long that the liquid turns black. Cool the tube thoroughly under the tap, add 30 c.c. of washed ether or of a mixture of equal parts ether and petroleum ether, cork tightly and mix we!l by inverting the tube. Allow the tube to stand for a few minutes for ihe complete separation of the ethereal layer, then remove the cork and transfer the ether to a tared flask by means of the apparatus shown in Fig. 9. This consists of a cork carrying an ordinary glass T tube. Through the straight limb of the T tube slides a berit glass tube, which is turned up at the lower end. The tube is adjusted by sliding it through the rubber collar (C) so that the lower end rests just above the junction of the two layers. On then blowing gently in the side arm (S), the upper layer is forced out into the flask. Repeat the ex- traction three times after the first, using 10 c.c. of ether each time and blowing it ofif into the flask. Distil off the ether, dry the residual fat and weigh. Notes. — It is almost useless to try to ex- tract the fat from milk by shaking it directly with a solvent. An emulsion is formed with the other constituents of the milk, and it is impossible to get a good separation of the solvent even with the centrifugal machine. This is probably due to the action of the colloidal casein, because it is found that when a complete or partial solution of the casein is effected it is comparatively easy to extract and separate the fat by a solvent immiscible with water. The ether which is employed should be well washed to food: analytical methods: milk. 159 remove alcohol, and the heating with hydrochloric acid should not be continued too long on account of the liability of forming caramel products which dissolve in the ether. For that reason the process is not so well suited for use with condensed or highly sugared milks. Since lactic acid is slightly soluble in ether, it is better when working with sour milk to make the extraction with petroleum ether or a mix- ture of petroleum ether and ordinary ether. Relation between Specific Gravity, Fat, and Solids in Milk. — As has been stated already, the specific gravity of milk is, in the main, a function of two factors, namely, the percentage of solids not fat and that of the fat. The former raises it, the latter lowers it. Taken by itself it afifords very little indication of the composition, but if any other item be known, it should be possible to find, by calculation, the other quantities, provided the assumption is true. The solids not fat are made up of several fluctuating constituents, but " nor- mal milk " seems to contain them in such a constant ratio that a calculation serves at least to detect an abnormal sam- ple. For example, given the specific gravity and solids to calculate the fat : Specific gravity = Gr. The amount which each per cent, of solids not fat raises the specific gravity = s. The amount which each per cent, of fat lowers the specific gravity ^ f. Total solids = T. Solids not fat = 5". Fat = F. Gr = Ss — Ff; or, substituting for 5" its value T — F; Gr ^ (T — F} s — Ff. The uncertainty of the calculation lies in the val- ues of s and f, which have not been quite satisfactorily deter- mined. At different times various formulae have been proposed for this calculation, varying, as a matter of course, with the method of fat extraction employed. The one most exten- l6o AIR, WATER, AND FOOD. sively used is that of Hehner and Richmond,* which is based on extensive observation and perfected processes of fat ex- traction. This formula is generally stated as follows : F = o.?,i,gT — o.2i?,6G, where i^ represents the fat, Tthe total solids, and G looo X (specific gravity — i.ooo). The simple formula -F = Z — — answers within the limits of experimental error for normal milk, but not for skimmed or, watered milk. Example. — Data : Or = 1.0323 ; G = {Gr — i) X 1000 = 32.3; T= 12.90. 6 ^2 ^ -F= 12.90 — ^— ^. F— 4.02 calculated, 3.99 found. 5 4 A similar relation has been worked out for the proteids and su>gar, so that from three determinations the whole com- position may be calculated. Exampje as above: Ash — .70 = A. Formula: P= 2.8 7+2.5^ — 3.33F— .68^, Gr. or P= 36.12 + 1.75 — 13.32 — 21.28 = 3.27. Sugar = T-{A-i-P+F) = 12.90 -(.70 +3.27 + 4.02) = 4.91. Where a number of calculations are to be made, Rich- mond's milk-scale will be found convenient. This is an in- strument based on the principle of the slide-rule, havmg three scales, two of which, for the fat and the total solids, are marked on the body of the rule, while that for the specific gravity is marked on the sliding part. Extended tables are also used for the same purpose. * Analyst, 13 (1SS8), 26; 17 {iSgZj, 170. food: analytical METHODS: MILK. l6l Milk-sagar. — The methods for the determination of the sugar in milk may be divided into two general classes: (i) those depending on the reducing power of the sugar upon an alkahne copper solution; (2) those which are based upon ob- servations of the degree of rotation of the plane of polarized light. (i) Determination by Fehling's Solution. (a) Volumetrically. Directions. — The milk must first be clarified to remove substances other than sugar which would exert a reducing action on the Fehling's solution. To do this, measure 25 c.c. of milk from a pipette into a 250-c.c. bottle. Add 0.5 c.c. (measured) of 25 per cent, acetic acid, shake vigorously, and allow it to stand for five minutes. Add 75 c.c. boiling dis- tilled water, shake, and let it stand two or three minutes. Add 15 c.c. of milk of alumina (see determination of chlorine in water), shake, and allow the bottle to remain on its side for ten minutes. Decant carefully into a medium-sized beaker, and add hot water again to the residue in the bottle. Decant the liquid from the beaker on to a ribbed Swedish filter. Wash thus by successive decantations from the bottle to the beaker, and thence to the filter several times before bringing the precipitate on the filter. Make the filtrate up to 500 c.c. and mix thoroughly. The solution should be perfectly clear and almost without color. Titration. — Measure 5 c.c. of the copper solution from a burette into a 150-c.c. Erlenmeyer flask, add 5 c.c. of the alkaline tartrate solution and 40 c.c. of water. Heat to boil- ing and from a burette run in the sugar solution, as prepared above, as long as a blue color is seen in the liquid, which must be kept constantly boiling. When the end-point is ap- parently reached, test the solution for copper by filtering a l62 AIR, WATER, AND FOOD. few drops through a very small filter on to a porcelain plate containing a dilute solution of potassium ferrocyanide strongly acidulated with acetic acid, when, if copper be pres- ent, the characteristic rose coloration will appear. This will give approximately the number of cubic centimeters required to decolorize the copper solution. To find the exact number, add the quantity of sugar solu- tion used above to a fresh portion of 5 c.c. of each solution and 40 c.c. of water, boil exactly two minutes, and test the solution for copper as before. If copper be still present, re- peat the operation, using 0.2 c.c, more or less, of the sugar solution each time until the end-point is reached. If 10 c.c. of Fehling's solution of the strength given are reduced by 500 X .067 0.067 gram of milk-sugar, then -. — -. 7 = grams ' ° c.c. solution used ° of milk-sugar in 25 c.c. of the milk. The results are reported in per cent. From 27 to 34 c.c. of the milk-sugar solution are usually required to reduce 10 c.c. of Fehling's solution. Notes. — The general principle upon which all these methods depend is based on the fact that certain sugars,, among which is lactose, have the power of reducing an alka- line solution of copper to a lower state of oxidation in which copper is separated as cuprous oxide. The copper salt which is found to give the most delicate and reliable reaction is the tartrate. The two solutions which make up the Fehling's solution are best preserved separately, and mixed only when wanted for use, as otherwise the reducing power of the solu- tion is liable to change. The amount of reduction of the copper salt to the cuprous oxide is afifected by the rate at which the sugar solution is added, the time and degree of heating, and the strength of the sugar solution; hence the necessity for adopting a definite procedure. food: analytical METHODS: MILK. I&3 (b) Gravimetrically by weighing as Cupric Oxide.* Directions. — To 15 c.c. of the copper sulphate solution add 15 c.c. of the alkaline tartrate solution in a 150-c.c. Erlen- meyer flask. Add 50 c.c* of freshly boiled distiUed water and place the flask in a boiling-water bath for five minutes. Then from a calibrated flask quickly add 25 c.c. of the sugar solu- tion to the hot Fehling liquor, leave the 25-c.c. flask inverted in the mouth of the larger one, and keep the whole in the boiling-water bath for fifteen minutes. At the end of this time remove the flask and filter off the cuprous oxide as rapidly as possible through a thick layer of asbestos in a weighed porcelain Gooch crucible. Wash with boiling dis- tilled water until the wash-water no longer reacts alkaline. Place the crucible in a platinum or nickel crucible and heat it, gently at first, then to a red heat for about fifteen minutes. Cool and weigh quickly, as the cupric oxide is somewhat hygroscopic. Convert the weight of cupric oxide into lactose by multiplying by the factor 0.6254, which will be sufficiently close for all ordinary work. If more accurate results are de- sired, consult Defren's table in the article previously men- tioned. Notes. — The asbestos which is used should be previously boiled in nitric acid and then in dilute sodium hydroxide and thoroughly washed. The amount of cuprous oxide produced by the action of one gram of reducing carbohydrate on Fehling's solution, in the manner described, is not a constant for all dilutions. For this reason the amount of lactose cannot be calculated ex- actly from the weight of cupric oxide, but reference must be made to the specially constructed table. Moreover, each table, whether Allihn's, Wein's, or Defren's, can be used only * Defren: TecA. Quart., 10 {i8()7), 167. l64 AIR, WATER, AND FOOD. when the reduction is carried out under conditions similar to those employed in the determinations on wtiich the table was based. (2) Determination by the Saccharimeter. — For the optical determination of milk-sugar the method of double di- lution, as described by Wiley and Ewell,* will be found satis- factory. Directions. — Into each of two flasks, marked at 100 and 200 c.c, respectively, put 65.52 grams of milk, add 10 c.c. of .acid mercuric nitrate, fill to the mark, and mix by shaking. Filter through dry filters and polarize in a 400-millimeter tube, using the Schmidt and Haensch saccharimeter. Cal- culate the results as in the following example: Weight of milk used = 65.52 grams; Reading from loo-c.c. flask = 20°. 84; " " 200-c.c. flask = 10°. 15. Then 10. 15 X 2 =20.30; 20.84 — 20.30 = 0.54; 0.54 X 2 = 1.08; 20.84 — 1.08 = 19.76; , 19.76 H- 4 = 4-94. which is the per cent. of milk-sugar. Notes. — The object in using the method of double dilu- tion is to avoid the necessity of making corrections for the volume of the precipitate of casein and fat. The method is based on the fact that, within certain limits, the polarizations of two solutions of the same substance are inversely propor- tional to their volumes. The flasks should be filled at nearly the same temperature as that at which the polarizations are made, and the tem- * Analyst, 21 (iSg6), 182. food: analytical METHODS: MILK. l6S', perature of the room should be kept as nearly as possible at 20° to avoid errors arising from marked changes in tempera- ture. PROTEIDS OF MILK. Determination of Total Proteids. — Weigh 5 grams of milk into a 750-c.c. round-bottomed flask and determine the nitrogen by the Kjeldahl process as directed on page 183. Multiply the per cent, of nitrogen by the factor 6.25 to obtain the per cent, of proteids. Separation of Casein and Albumin.* — Directions. — To 5 grams of milk add 50 c.c. of a solution of magnesium sulphate (saturated at 40°-50°) and heat the mixture tO' about 45° until the precipitate settles out, leaving the super- natant Hquid clear. Filter and wash the precipitate several times with the solution of magnesium sulphate prepared as above, keeping the temperature at about 45". Determine the nitrogen in this precipitate and multiply by 6.38 for the casein. The difference between the total and casein nitrogen will be the amount corresponding to the albumin, together with the very small amount of globulin. Notes. — The principal proteid body present in milk is casein. Others present in much smaller quantity are albutain, peptone, and fibrin or globulin. Different observers at vari- ous times have claimed the presence of other nitrogenous bodies, but these have not been entirely substantiated. It is now generally held that the colloidal state in which the casein is held in milk is due to the combination with it of certain mineral compounds, chiefly those of calcium. The action of precipitants is on these mineral matters, breaking up the combination and releasing the insoluble casein. Sebelien: Ztschr. physiol. Chem., 13 (iSSg), 160. 1 66 AIR, WATER, AND FOOD. Most- authorities at present favor the factor 6.38 for cal- culating the casein, although the old factor 6.25 is still largely used. Adulterants. — The most common forms of adulteration of milk are the addition of water and the removal of cream. The former is detected by the decrease in the specific gravity, total solids and ash, and the latter by the increased specific gravity and greatly decreased amount of fat. Various sub- stances may also be added, such as salt, cane-sugar, or starch. Direct Determination of Added Water. — This is best done by determining the specific gravity of the milk-serum after coagulation and removal of the casein.* The casein is co- agulated by dilute acetic acid, filtered off on a dry filter, and the specific gravity of the filtrate taken at 15" C. by the West- phal balance. The specific gravity of the serum from normal milk is never below 1.027 ^^^ o'^ly rarely below 1.029. The addition of each ten per cent, of water lowers the specific gravity by o.ooio to 0.0035. Salt. — Detected by the high percentage of ash and deter- mined by titration with silver nitrate and potassium chromate either in the ash or in the milk itself after clarification with milk of alumina. Cane-sugar. — To detect the presence of cane-sugar boil about 10 c.c. of the milk with o.i gram of resorcin and i c.c. of hydrochloric acid for five minutes. The liquid will be col- ored rose-red if cane-sugar be present. The quantitative de- termination may be made by means of the polariscope. Starch. — Heat 10 c.c. of the milk to boiling in a test-tube, and when cold add a few drops of a solution of iodine in po- tassium iodide. The presence of even 0.2 per cent, of starch will be shown by the characteristic blue coloration. * Woodman: J. Am. Chem. Soc, 21 {i8gg), 503. food: analytical methods: milk. 167 Coloring-matters.* — The principal coloring-matters added to milk are annatto, caramel, and aniline dyes. In general, coloring-matters are added only to watered milk, but -occasionally samples which were of standard quality have been found to be colored. Directions. — Put about 100 c.c. of the milk into a small l3eaker, add 2 c.c. of 25 per cent, acetic acid and allow the beaker to stand quietly for about ten or fifteen minutes in a water-bath kept at 70° C, the casein being thus separated as a compact cake. Decant off the whey, squeezing the curd is free from it as possible by means of a spatula. Transfer the curd to a flask and let it remain covered with ether for an hour or more. Evaporate the ether extract which contains the annatto if present, take up the residue with water made faintly alka- line with sodium hydroxide and filter through a wet filter. If annatto is present, it will permeate the filter and give it an orange color when the fat is washed off and the filter dried. Treat the dried filter with stannous chloride. If annatto is present, a pink color will be produced. After pouring off the ether examine the milk-curd for caramel or aniline orange. If the curd is left white, neither of these colors is present. If caramel has been used, the curd will be of a pinkish-brown color; if the color is due to the -aniline dye, the curd Avill have a yellow or orange tint. To distinguish between the two colors shake a small jJortion of the curd in a test-tube with strong hydrochloric acid. The caramel-colored curd will act similarly to an uncolored curd, that is, it will gradually produce a deep blue color in the so- lution. On the other hand, the aniline color will immediately produce with the hydrochloric acid a pink color. * Ann. Rep. State Bd. Health, Mass., 1898, 697. l68 AIR. WATER, Ai\D FOOD. Preservatives. — The preservatives usually added to milk are salicylic acid, borax or boric acid, formaldehyde, and occasionally benzoic acid and potassium chromate. Car- bonate of soda is also added in some cases to disguise the acidity of sour milk. Salicylic Acid. — To 50 c.c. of the milk add 10 c.c. of the acid mercuric nitrate used in the optical determination of milk-sugar, shake and filter. Shake the filtrate violently in a separatory funnel with 30 c.c. of a mixture of equal parts of ether and petroleum ether. Evaporate the ethereal solu- tion to dryness and add a drop of neutral ferric chloride solution to the residue. If saHcylic acid is present, the char- acteristic violet color will be produced. Boric Acid. — Add 5 drops calcium hydroxide solution to- 10 (or 100) c.c. of milk and evaporate to dryness on a water- bath. Char the residue, add 2 c.c. water and a few drops of dilute hydrochloric acid, and filter into a porcelain dish. Test the filtrate in the usual way with turmeric-paper or by the alcohol-f^ame test. For the latter methyl alcohol is best. The tests for boric acid can also be apphed to the hydro- chloric acid solution of the ash. Formaldehyde. — This is generally used as a 40 per cent, aqueous solution, sold under the name of formalin. Several simple tests commonly used for the presence of formaldehyde will be described. (i) When the sulphuric acid is added to the milk in mak- ing the Babcock test for fat, a bluish- violet ring will be noticed at the junction of the two liquids when formaldehyde is present. One part of formaldehyde in 200,000 parts of milk can be detected by this test, but it fails when the for- maldehyde amounts to 0.5 per cent. The test is more delicate if the sulphuric acid contains a trace of ferric chlo- ride. food: analytical methods: butter. 169 (2) To 10 c.c. of milk add i c.c. of fuchsin sulphurous acid and allow it to stand five minutes; it takes on a pink color whether formaldehyde be present or not. Then add 2 c.c. of dilute hydrochloric acid and shake. Pure milk be- comes yellowish white, while milk containing formaldehyde gives a violet color. This test will detect i part of formalde- hyde in 20,000 parts of milk, and if applied to the distillate from the milk will show i part in 500,000. (3) To 10 c.c. of milk in a small porcelain dish add art equal volume of hydrochloric acid (1.12 sp. gr.). Add one drop of ferric chloride solution and heat the dish with a small flame, stirring vigorously, until the contents are nearly boil- ing. Remove the flame and continue the stirring for two or three minutes. The presence of formaldehyde will be shown by a violet color which appears in the particles of the precipitated casein, the depth of color depending on the amount of formaldehyde present. This test readily shows the presence of i part of formaldehyde in 500,000 parts of milk. Benzoic Acid. — Fres. Zeit., 21, 531; Jour. Anal. Chem., 2, 446. Sodium Carbonate. — Detected in the milk-ash, as on page 153. If effervescence occurs, test the original milk with rosolic acid as follows: Mix 10 c.c. of milk with an equal volume of alcohol, and add a few drops of a one per cent, solution of rosoHc acid. The presence of sodium carbonate is indicated by a more or less distinct pink coloration. A comparative test should be made at the same time with milk known to be pure. BUTTER. General Statements. — Butter consists of the fat of milk, to- gether with a small percentage of water, salt, and curd. I/O AIR, WATER, AND FOOD. The curd is made up principally of the casein of the milk. These various ingredients are present in about the following proportions: Fat 78.00-goo per cent. ; average, 82 per cent. Water 5.00-20.0 " " " 12 " Salt 0.40-15.0 " " •' 5 " " Curd o.ii- 5.3 " " " I " The fat consists of a mixture of the glycerides of the fatty acids. The characteristic feature of butter-fat is the extraor- dinarily high proportion of the glycerides of the soluble and volatile fatty acids when contrasted with other fats. Recent investigations * show the following to be the probable composition of normal butter-fat: Acid. Per cent. Acid, Per cent. Triglycerides. Dioxystearic i.oo 1.04 Oleic 32.50 33.95 Stearic 1.83 1,91 Palmitic 38.61 40.51 Myristic 9.89 10.44 Laurie 2.57 2.73 Capric 0.32 0.34 Caprylic 0.49 o. 53 Caproic 2.09 2.32 Butyric 5.45 6.23 Total 94. 75 100.00 According to this, the proportion of volatile acids in but- ter (butyric, caproic, caprylic, and capric acids) amounts to 8.35 per cent. The amount of volatile acid in lard, for ex- ample, is about o.i per cent. The usual examination of butter consists in the examina- tion of the butter-fat, in order to detect the presence of foreign fats. The determination of the amount of curd may be of -value also in some cases, more especially from a sanitary * Browne: /. Am. Chem. Soc, 21 (iSgg), 807. food: analytical METHODS: BUTTER. 171 Standpoint. The chief danger to health probably lies in the possible decomposition of the nitrogenous portion, for it is ■quite generally recognized that the substitution of oleo- margarine is not injurious to health. It is a not infrequent practice, however, as remarked in the previous chapter, to incorporate a large amount (sometimes as high as 33 per cent.) of curd and other nitrogenous matters in fresh butter. If this is kept for any length of time, a decomposition is liable to occur which may have serious effects. Other de- terminations' that are usually made are the water and salt. The " aroma " of butter seems to be connected with the decomposition produced by the action of bacteria on the casein and the small amount of milk-sugar that is present, and not with any change in the fats; there is no evidence, however, that any unwholesome effect is produced by the aroma-giving organisms. The rancidity of butter-fat is generally considered to be due to decomposition and oxidation of the fatty acids, espe- cially the unsaturated ones, the amount of change depending on conditions of light, heat, and exposure to air. Examination of the Fat. — The fat is first separated from the other constituents of the butter so that it may be weighed out for the various tests. Directions. — Melt a piece of butter, a'bout two cubic inches, in a small beaker placed on top of the water-bath so that the temperature shall not rise above 5o°-6o°. After about fifteen minutes the water, salt, and curd will have set- tled to the bottom. (A better separation may be secured by pouring the melted butter into a test-tube and whirling it for 3-4 minutes in a centrifugal machine.) Place a bit of absorbent cotton in a funnel, previously warmed, and decant off the clear fat through the cotton into a second beaker, taking care that none of the water or curd is brought upon 1/2 AIR, WATER, AND FOOD. the filter. When the filtered fat has cooled to about 40* place a small pipette in the beaker and weigh the whole. By means of the pipette the desired amount of fat is taken out, the pipette replaced in the beaker, and the whole again weighed. The difference in weight gives the exact amount of fat taken. It is a saving of time, however, if several por- tions are to be weighed out, to make the weights one after another, so that one weight will suffice for a determination^ Weigh out thus: Two portions of 5 grams each into 250-c.c. round-bottomed flasks for the Reichert-Meissl method, one portion of 2.5 to 3 grams into a 500-c.c. beaker for Hehner's- process, two portions of about i gram each into 300-c.c. glass-stoppered bottles fo. Hiibl's process. (i) Reichert-Meissl Number for Volatile Fatty Acids. — Directions. — To the fat in the 250-c.c. flasks add 2 c.c. of strong caustic potash (1:1) and 10 c.c. of 95 per cent, alcohol. Connect the flask with a return-flow condenser and heat on a water-bath so that the alcohol boils vigorously for 25 minutes. At the end of this time disconnect the flask and evaporate off the alcohol on a boiling-water bath. After the complete removal of the alcohol add 140 c.c. of re- cently boiled distilled water which has been cooled to about 50°. The water should be added slowly,- a few cubic centi- meters at a time. Warm the flask on the water-bath until a clear solution of the soap is obtained. Cool the solution to about 60° and add 8 c.c. of sulphuric acid (1:4) to set free the fatty acids. Drop two bits of pumice, about the size of a pea, into the flask, close it by a well-fitting cork, which is tied in with twine, and immerse it in boiling water until the fatty acids have melted to an oily layer floating on the top of the liquid. Cool the flask to about 60°, remove the cork, and immediately attach the flask to the condenser. Distil no c.c. into a graduated flask in as nearly thirty FOOD: ANALYTICAL METHODS: BUTTER. 173 minutes as possible. Thoroughly mix the distillate, pour the whole of it through a dry filter, and titrate 100 c.c. of the N mixed filtrate with — sodium hydroxide, using phenol- phthalein as an indicator. Increase the number of cubic centi- meters of alkali used by one-tenth, and correct the reading also for any weight of fat greater or less than 5 grams. For example, if 5.3 grams of butter-fat are used, and 100 N c.c. of the distillate require 27.4 c.c. of — NaOH, no c.c, would require 27.4 + 2.74^ 30.14 c.c. Then 5.3 : 30.14 ^ 5 : X. x=^ 28.4. X is the Reichert-Meissl number. Notes. — The Reichert-Meissl number for genuine butter varies from 24 to 34; the average usually taken is 28.8. Oleomargarine gives a number of about 1.5 to 2. When the fat is treated with potash it is decomposed, the glycerine being set free, and the potassium salts of the fatty acids, that is to say, the potassium soaps are formed. Hence the process is called saponification. For butyric acid the re- action is C3H5(C3H,COO)3 -f- 3KOH = sCaH^COOK + C3H,(OH)3. The alcohol is used to dissolve the fat. But at the moment the butyric acid is set free it tends to combine with the alcohol to form a volatile ether: CsH^COOH -f C2H5OH = C3H..COOC2H5 -f H2O. The object of the return-flow condenser is to prevent the escape of this volatile ether and to allow of its complete saponification. If the water used to dissolve the soap is added too rap- idly, the soap may be decomposed with the liberation of the fatty acids: C3H7 COOK -f- H^O = C3H, COOH + KOH. 174 AIR, WATER, AND FOOD. The fatty acids are set free at the proper time by means of sulphuric acid, and the volatile acids distilled off and titrated. The pumice is added to prevent explosive boiling. The whole of the volatile acids do not pass over into the distillate, but only a part, the amount depending upon the rate of distillation and the volume of the distillate. Hence, in order to get uniform results, it is necessary to follow the pre- scribed procedure with great care. (la) Method of Leffman and Beam. — In order to shorten the time required for the saponification and subse- quent removal of the alcohol, Leffman and Beam * have proposed the use of a solution of sodium hydroxide in glycer- ine as the saponifying agent. Directions. — To the fat, weighed out into a 250-c.c. flask, as in the Reichert-Meissl method, add 20 c.c. of the glycerine- soda solution and heat the flask over a lamp. Boil the mix- ture gently until all the water has been driven off and the liquid becomes perfectly clear, which will usually be the case in about five minutes. Care should be taken to avoid loss- from spattering. Allow the flask to cool somewhat, and dissolve the soap in 135 c.c. of boiled distilled water. Add the first portions of water drop by drop, shaking the flask each time to avoid foaming. When the soap is dissolved, add 5 c.c. of sulphuric acid (1:4), two pieces of pumice, and carry out the distillation without previous melting of the fatty acids. The distillation and titration are completed as in the Reichert-Meissl process. (2) Hehner's Method for Direct Determination of the Fixed Fatty Acids. — Directions. — To the portion of 2.5 grams weighed out into the 500-c.c. beaker add i e.c, o£ caustic potash and 20 c.c. of 95 per cent, alcohol. Cover * " Analysis of Milk and Milk Products" (Philadelphia, 1896), p. 78. food: analytical methods: butter. 175 the beaker with a watch-glass and heat it on the water-bath until the liquid is clear and homogeneous. As it is not essential to prevent the escape of the volatile acids, the use of a return-flow condenser is not necessary. Evaporate off the alcohol on the water-bath and dissolve the soap in about 400 c.c. of warm distilled water. When the soap is com- pletely dissolved add 10 c.c. of hydrochloric acid (sp. gr. 1. 12), and heat the beaker in the water-bath almost to boil- ing until the clear oil "floats. Meanwhile dry and weigh a thick filter in a small covered beaker. Allow the solution to cool until the fat forms a solid cake on top; filter the clear liquid and finally bring the solid fats upon the weighed filter. Wash the beaker and fat thoroughly with cold water, then wash out the fat adhering to the beaker with boiling water, which is poured through the filter, taking care that the filter is never more than two-thirds full. Cool the funnel by plunging it into cold water, remove the filter, place it in the weighing-beaker and dry it at 100° to constant weight. The fat should be heated about an hour at first, then for periods of about fifteen minutes, until the weight is constant within 2 mgs. Notes. — 87.5 per cent, is usually taken as the proportion of fixed fatty acids in butter-fat; 88 and 89 per cent, have been frequently found. All other fats yield from 95 to 96 per cent, of insoluble fatty acids. (3) Method of Baron Hiibl. — This method is based on the fact that certain of the fatty acids, notably the " unsatu- rated acids," as oleic acid, C17H33COOH, take up the halo gens with the formation of addition products. Directions. — Dissolve the butter-fat in the 300-c.c. bottles in 10 c.c. of dry chloroform. Add 30 c.c. — in the case of a doubtful butter 50 c.c. — of the iodo-mercuric solution from a pipette or glass-stoppered burette, and allow the bottles to 176 AIR, WATER, AND FOOD. stand, with frequent shaking, for three hours in a dark closet. A blank should be carried through at the same time and with the same amount of reagents, in order to determine the rela- tion between the thiosulphate and the iodo-mercuric solu- tion, the latter being liable to change. Now add 20 c.c. of potassium iodide (to prevent precipitation of mercuric iodide on dilution), then 100 c.c. of distilled water, and titrate the N excess of iodine with — sodium thiosulphate until the solu- tion is faintly yellow. Add a few drops of starch solution and titrate to the disappearance of the blue color. Calculate the result in grams of iodine absorbed by 100 grams of fat. This is called the Hiibl or Iodine absorption-number. Standardization of the Thiosidphate Solution. — As this is not permanent, its strength should be determined by means of the standard potassium bichromate solution, i c.c. of which is equivalent to 0.0 1 gram of iodine. The standardi- zation may be done while waiting for the absorption of the iodine. Measure 20 c.c. of the potassium bichromate from a pipette into an Erienmeyer flask. Add 10 c.c. of potassium iodide, 100 c.c. of water, and 5 c.c. of strong hydrochloric acid, and shake the flask for three minutes. Titrate the liberated iodine with the thiosulphate solution until the color has almost disappeared, then add starch solution and continue the titration until the blue color changes to a sea-green, due to the formation of chromium chloride. The iodine is liberated in accordance with the following equation: KaCroO^ + 14HCI + 6KI = 8KC1 -1- 2CrCl3 -f 7H2O + 61. Calculation of Results. — Example. — From the standardi- zation, food: analytical methods: butter. 177 17.2 c.c. thiosulphate = 21.5 c.c. bichromate = 0.215 gram I; I c.c. thiosulphate = 0.0125 gram I. Also, from blank, 31 c.c. iodine solution = 46.5 c.c. thiosulphate; I c.c. iodine solution = 1.5 c.c. thiosulphate. If 31 c.c. iodine solution have been added to 1.049 grams •of fat, then 31.0 X 1.5 = 46.5 c.c. is the equivalent amount •of thiosulphate solution; and if 19.4 c.c. thiosulphate were used to titrate excess of free iodine, 46.5 — 19.4 ^^ 27.1 c.c. is the amount of thiosulphate equivalent to the iodine combined with the fat. Then, since I c.c. thiosulphate is equivalent to t ■ 1- 27.1 X O.OI2S . . 0.0125 gram free lodme, — — X 100 = 32.29 grams ■of iodine combined with 100 grams fat. Notes. — It is assumed that 100 grams of pure butter-fat •absorb 30-40 grams iodine; artificial butter, 55 grams; oleo- margarine, 63-75 grams; olive-oil, 83 grams; and cottonseed- oil, 106 grams. The products formed by the action of iodine on the fats are mainly addition products with a slight proportion of sub- stituted bodies. Thus the unsaturated olein, (CiyH33COO)3 C3H5, takes up six atoms of iodine, forming an addition product, di-iodo-stearin, (Ci7H33l2COO)3C3H5. The exact amount of iodine absorbed depends on the ■strength and the amount of iodine solution used, and on the length of time it is allowed to act. The presence of mer- curic chloride shortens the time of reaction, probably by acting as a carrier of iodine. Physical Methods — Microscopic Examination. — Pure, fresh butter is not ordinarily crystalline in structure. Butter which has been melted, however, and fats which have been liquefied and allowed to cool slowly show a distinct crystal- line structure, especially by polarized light. If only fresh but- 178 AIR, WATER, AND FOOD. ter were sold, and all adulterants had been previously melted and slowly cooled, this method would be all that would be necessary for the detection of adulteration. As it is, how- ever, it is most useful in making comparative examina- tions of samples which have been subjected to the same conditions. From an examination of the accompanying plate,* which shows the appearance by polarized light of four samples of known origin which were melted and cooled slowly under exactly similar conditions, it will be seen that^ while the differences are noticeable, they are not sufficient in all cases to form a basis for absolute identification. For a further discussion of this point the student is re- ferred to Bulletin 13, U. S. Dept. Agr., Part I, pp. 29-40; Part IV, pp. 449-455- Specific Gravity. — This is most conveniently determined at 100" C. by means of the Westphal balance (see Allen, The Analyst, 11, 223; also Bull 13, Part IV, pp. 430-431). The pyknometer method is, however, the one adopted by the As- sociation of Official Agricultural Chemists, to whose report (Bulletin 46, Rev. Ed., 1899, p. 51) reference is made. Melting-point. — This is best determined according to the directions given in the Bulletin just mentioned (46), p. 52. Refractive Index. — The degree to which light is refracted differs with various fats, and these differences are often of considerable analytical value. See Bulletin 46, Rev. Ed., p. 49, for a description of the method employed in its determina- tion. Determination of Water. — Directions. — Weigh 2 grams of butter into a shallow platinum dish having a flat bottom two inches in diameter and containing a slender stir- ring-rod two and a half inches long. Heat the butter in the oven at 100° C. for thirty minutes, cool in a desiccator, and * From photomicrographs by A. G. Woodman and A. I. Kendall, igoo. yv"/.' ♦';';/: 1 -■■'-■' i ^P^^hH^H '''''^**^|:^|^ 1 ^ , . . A. Butter X 30. C. Oleomargarine X 30. B. Beef-fat X 30 D. Lard X 30. food: analytical METHODS: BUTTER. iSl weigh. Heat again for periods of fifteen minutes, until the weight remains constant. During the process of heating stir the butter frequently to hasten evaporation of the water. Note. — The loss in weight is calculated as water, although a portion of the volatile acids is also lost, the amount depend- ing upon the time of heating. Determination of Salt. — Directions. — Weigh lo grams of butter in a small beaker, add 30 c.c. of hot water, and when the fat is completely melted transfer the whole to a separatory funnel. Shake the mixture thoroughly, allow the fat to rise to the top, and draw off the water, taking care that none of the fat-globules pass the stopcock. Repeat the operation four times, using 30 c.c. of water each time. Make the washings up to 250 c.c, mix thoroughly, and titrate 25 N c.c. in a six-inch porcelain dish, using — silver nitrate with potassium chromate as an indicator. Complete Analysis of Butter in One Sample. — Direc- tions. — Weigh about 2 grams of butter into a platinum Gooch crucible, half-filled with ignited fibrous asbestos, and dry it at 100° C. to constant weight. The loss in weight is the amount of water. Then treat the crucible repeatedly with small portions of petroleum ether, using gentle suction, and again dry it to constant weight. The difference between this and the preceding weight will be the amount of fat. Now carefully heat the crucible over a small flame or in a muffle until a light grayish ash is obtained. The loss in weight is the amount of curd, and the residual increase in weight over that of the crucible and as'bestos is the ash. If de- sired, the salt may be washed out of the ash and determined by titration with silver nitrate. Detection of Coloring - matters. — The principal color- ing-matter used in butter is annatto; sometimes safifron is 1 83 AIR, WATER, AND FOOD. employed. These may be detected by the method proposed by Cornwall.* Directions. — Dissolve about 5 grams of the warm filtered fat in 50 c.c. of ether and shake in a separatory funnel for ten or fifteen seconds with 15 c.c. of a very dilute solution of caustic potash, only alkaline enough to give a distinct re- action with turmeric-paper. After an hour or two draw off the aqueous solution, colored more or less by the annatto, shake it once more with a fresh portion of ether, and evapo- rate to dryness. Treat the dry residue with a drop of con- centrated sulphuric acid. In the presence of annatto the yellow residue turns blue or violet, then quickly green, and finally brownish or somewhat violet. Safifron differs in not giving the green coloration. Blank tests should be made with the ether. FLOUR, PREPARED CEREALS, ETC. This class of foodstuffs is usually in a dry form and not liable to rapid change by micro-organisms, and the examina- tion consists in the determination of their " food value." This may require a simple analytical process, as in the case of the quantity of nitrogen in a sample of " gluten " sold for diabetic patients, or in the case of a brand of flour to be used in a hos- pital or State institution. It may also require an estimation of the available food-material, as in the case of two kinds of beans or corn. The actual determination of digestibility be- longs to physiological chemistry and need not be taken into consideration here. Moisture. — Directions. — Spread about 2 grams of the finely ground material in a- thin layer on a watch-glass and dry it in the oven at 100° C. for five hours. * CAem. News, SS {1S8T), 49. food; analytical methods: cereals. 183 Note. — With some substances drying in a current of hydrogen or some inert gas may be necessary, but for most cereals the method given will be found satisfactory. Ash. — Directions. — Weigh about 2 grams into a plati- num dish, such as is used for the determination of water in butter, and char it carefully. Ignite at a very low red heat until the ash is white, preferably in a muffle or radiator. Note. — If a white ash cannot be obtained in this manner, exhaust the charred mass with water, collect the insoluble residue on a filter, burn it, add this ash to the residue from the evaporation of the aqueous extract and heat the whole at a low red heat until the ash is White. Ether Extract : Fats and Oils. — Directions. — Place the residue from the determination of moisture, as described above, in an extraction-cone and extract it with pure anhy- drous ether for sixteen hours. Evaporate ofif the ether and dry the residual fat at a low temperature to constant weight. Total Proteids : Determination of Nitrogen by the Kjeldahl Process.* — Principle. — Oxidation of carbon and hydrogen, and conversion of organic nitrogen to ammonium sulphate by means of boiling sulphuric acid in presence of mercury, the latter acting as a carrier of oxygen, and being converted to mercuric sulphate. Precipitation of mercury by potassium sulphide to prevent the formation of mercur- ammonium compounds when the solution is made alkaline. Setting free of ammonia by neutralization of the acid by po- tassium hydroxide. Distillation of ammonia into a measured N quantity of — hydrochloric acid. Titration of excess of acid. Directions. — Transfer about 0.5 gram of the finely divided substance from a weighing-tube to a 750-c.c. round-bot- tomed flask, add 10 c.c. of concentrated sulphuric acid free * Ztschr. anal. Chem., 22 {1S83), 366. 1 84 AIR, WATER, AND FOOD. from nitrogen, and 0.2 gram of metallic mercury. Place a small funnel in the neck of the flask, which should be sup- ported in an inclined position on wire gauze and heated with a small flame until frothing has ceased and the liquid boils quietly. Then increase the heat and boil the solution for half an hour after it becomes colorless. Allow the flask to cool for a minute or two, and add a few crystals of potassium per- manganate until the liquid has acquired a slight green or purple color. Meanwhile free the distilling apparatus from ammonia by distillation with pure water until a slight color only is given to 50 c.c. of the distillate by Nessler's reagent. N Measure 25 c.c. of — hydrochloric acid from a burette into a 300-c.c. Erlenmeyer flask and place the condenser-tip beneath the surface of the liquid, adding a little water, if nec- essary, to seal it. Rinse down the neck of the digestion-flask with 100 c.c. of ammonia-free water, add 20 c.c. of potassium sulphide solution, and connect the flask with the condenser. Add 100 c.c. of caustic potash through the separatory funnel, and dis- til off the ammonia by steam.. When 200 c.c. have distilled over, remove the collecting-flask, after rinsing off the conden- ser-tip with distilled water, and titrate the excess of acid with N — sodium hydroxide, using methyl orange or cochineal as indicator. A blank determination is made with 0.5 gram of cane-sugar in order to reduce any nitrates present in the re- agents which might otherwise escape detection. Notes. — The temperature during the digestion must be maintained at or near the boiling-point of the acid, since at a lower temperature the formation of ammonia is incomplete. The process is considered by Dafert * to take place in four * Ztschr. anal. Chem., 24 {1885), 455. food: analytical methods: cereals. 185 steps: (i) the sulphuric acid takes the elements of water from the organic matter; (2) the sulphur dioxide produced by the action of the residual carbon on the sulphuric acid exercises a reducing action on the nitrogenous bodies; (3) the nitro- genous substances formed in this way are converted to am- monia by a process of oxidation; (4) the ammonia formed is iixed by the acid as ammonium sulphate. In some cases the potassium permanganate is necessary to insure the complete conversion of the nitrogenous bodies into ammonia, although it is probable that its use is unneces- sary in the majority of analyses. The Kjeldahl process in the form outlined above is not applicable to the determination of nitrogen in the form of nitrates. In order to render it of more general apphcation various modifications of the method have been proposed, the one generally used in this country being that suggested by Scovell.* In this method salicylic acid is used with the sul- phuric acid, being converted by the nitrate into nitro-phenol. By the use of sodium thiosulphate or zinc-dust this is reduced to amido-phenol. The amido-phenol is transformed into am- monium sulphate by the heating with sulphuric acid, the use of mercury being absolutely necessary in this case to secure the complete transformation. The per cent, of proteids may be found by multiplying the per cent, of nitrogen by an appropriate factor, the one in gen- eral use being 6.25. It is better to use a special factor for each cereal, however, using the factor 6.25 only when a special fac- tor is not given. The factors for the common cereals are: wheat 5.70, rye 5.62, oats 6.31, maize 6.39, and barley 5.82. Qualitative Tests for Proteids. — (a) Biuret Reaction. — To a small quantity of the solution add about i c.c. of di- * U. S. Dept. Agr., Bull. 16 (1SS7), 51. 1 86 ' AIR, WATER, AND FOOD. lute (4 per cent.) copper sulphate solution and then a consid- erable excess of strong caustic potash or soda. A violet color is produced. The test is generally known as the biuret reac- tion because the substance biuret, CaHgNjOa, left on heatings urea to 160° C, gives the color under the same conditions. If too much of the copper sulphate solution be used, its color may conceal that of the reaction. (b) Xanthoproteic Reaction. — Strong nitric acid produces a yellow coloration of proteid matter, which is intensified on warming. On treating the yellow mixture with ammonia in slight excess the color is changed to an orange or red tint. (c) Millon's Reaction. — When proteid matter is boiled with Millon's reagent (see page 211), a brick-red coloration is produced. A similar reaction is given by gelatin and allied bodies. (d) Liebermann's Test. — ^Heat the solid proteid with con- centrated hydrochloric acid. It will dissolve with the gradual formation of a blue coloration, changing to violet and brown. (e) Adamkiewicz Reaction. — If glacial acetic acid in excess and then strong sulphuric acid are added to a proteid, a vio- let color with faint fluorescence is produced. Note. — Since many other substances give a test with cer- tain of the reagents employed to test for proteids, it will be obvious that a proteid can be identified with certainty o^ly by employing a large number of its reactions. Separation of the Proteids of Wheat. — As an ex- ample of the principles involved in the separation of vegetable proteids may be taken the separation of the proteids of wheat. The principal proteids found in wheat are ghifcnin, gliadin, edestin, and leucosin. There is also present in wheat a certain amount of nitrogen in the form of amides, and a trace of lecithin, a nitrogenous body allied to the fats. The total proteid matter insoluble in cold water is ordinarily known as food: analytical METHODS: CEREALS. iS/' gluten. It is a mixture of the two proteids first named. The crude gluten is readily obtained from flour by kneading a quantity of it in a thin stream of cold water until the starch and soluble matter is removed. The methods of separation depend in general upon the relative solubility of the proteids in dilute salt solutions or in alcohol of different strengths.* Edestin and Leucosin. — These may be determined together by first extracting a definite weight of the finely ground ma- terial with a I per cent, sodium chloride solution. To an aliquot part of the clear salt solution is added sufficient strong alcohol to make the mixture 75 per cent, alcohol. After standing overnight the precipitate is filtered off and the nitro^ gen in it determined. If desired, the two proteids may be separated by coagulating the leucosin at 60° C. and precipi- tating the edestin by adding alcohol to the clear filtrate as before. The nitrogen in each precipitate is then determined. Amides. — Determined by precipitating all the proteids from the above salt solution by means of phospho-tungstic acid. After standing overnight the precipitated proteids are' filtered off and the nitrogen of the amides in the solution de- termined. Gliadin. — About a gram of the finely divided material is extracted with hot alcohol (sp. gr. 0.90). The filtrate and washings are evaporated to dryness in a Kjeldahl flask and the nitrogen determined in the residue. The per cent, of nitrogen found, less the per cent, of amide nitrogen, is the per cent, of gliadin nitrogen. Glutenin. — ^This is the difference between the per cent, of total nitrogen and the per cents, of the edestin, leucosin, gliadin, and amide nitrogen. * G. L. Teller: Ark. Agr. Expt. Sta., Bull. 42 (,i8g&), 81; see also Osborne's papers in Am. Chem. J., IS-IS- 1 88 AIR, WATER, AND FOOD., The per cents, of the various proteids may be found by multiplying the corresponding nitrogen by 5.70. Carbohydrates. — Total Carbohydrates. — Generally deter- mined by subtracting from 100 the sum of the per cents, of the other constituents, viz., water, ash, fats and oils, and nitro- genous matters. The total carbohydrates are made up princi- pally of sugars, starches, and crude fibre, the latter including pentosans and cellulose. Sugars. — The finely ground material, previously ex- tracted with petroleum ether if much oil is present, is ex- tracted for about three hours with 80 per cent, alcohol. The extracted matter is dried at a low temperature and weighed. Starch. — The methods for the determination of starch vary with the condition in which the starch is found. In the case of nearly pure starch it may be converted into dextrose by boiling with dilute acid, the dextrose being then deter- mined by Fehling's solution in the usual way. Hot acids, however, cannot be used to convert starch in the natural state, as it is found in cereals, because other carbohydrate bodies become soluble under these conditions. In such cases the starch is broug'ht into solution by treatment with diastase or by heating with water under pressure. For the rapid estimation of starch in cereals the following method has been found useful: * Principle. — Conversion of starch to dextrin and maltose, that is, solution of the starch by diastase in malt extract. Con- version of dextrin and maltose to dextrose by acid (hy- drolysis). Directions. — Place about a gram of the finely divided sam- ple, the residue from the extraction of sugar, for example, in a flask, add 50 c.c. of water, 3 c.c. of malt extract, and boil for * Hibbard: y. Am. Chem. Soc, 17 {i8gs), 64. FOOD: ANALYTICAL METHODS: CEREALS. 1 89 •one minute, with frequent shaking. Cool the solution to 60° C, add 3 c.c. of malt extract, and heat slowly so that fifteen minutes are required to reach the boiling-point. Test the solution for starch by placing a drop upon a porcelain tile and adding a drop of solution of iodine in potassium iodide. Should a blue color appear, add more malt extract and repeat the heating until all the starch has been converted. Cool the solution, make it up to 100 c.c, and filter it through fine linen or cotton cloth. To an aliquot part of the filtrate, 25 or 50 c.c, in a flask, add 5 c.c. of hydrochloric acid (sp. gr. 1.15), and enough water to make the volume 60 c.c Place a small funnel in the neck of the flask to retard evaporation and boil the solution gently for exactly half an hour. Cool the solu- tion, add sodium hydroxide until nearly neutralized, and de- termine the dextrose by Fehling's solution. A blank deter- mination should be carried throug'h under the same conditions and using the same quantities of reagents, in order to make a correction for the sugar in the malt extract. Malt Extract. — Treat coarsely pulverized dry malt for sev- €ral hours with sufficient 20 per cent, alcohol to cover it. The solution is then filtered and may be kept for two weeks with- out losing its diastatic power. If the malt itself is not readily procurable, certain forms of prepared diastase are on the market and may be found more convenient either for analytical use or for purposes of illus- tration. When possible, however, it is preferable to use the freshly prepared malt extract as the prepared diastase, made at different times and from separate portions of malt, may show great differences in hydrolytic power. Crude Fibre- — This may be determined by the method adopted by the Association of Official Agricultural Chemists.* * U. S. Dept. Agr., Div. of Chem., Bull. 46 [Rev. Ed.] {i8g8), 26. igo AIR, WATER, AND FOOD. EXAMINATION OF FERMENTED LIQUORS. WINE. Effervescing wines should, before analysis, be vigorously- shaken in a large flask, to remove carbon dioxide. Specific Gravity. — This is to be taken by means of the Westphal balance or Sprengel tube at 15.° 5 C. Alcohol by Weight. — Principle. — The alcohol is ob- tained freed from everything but water and its amount deter- mined by ascertaining the specific gravity of the mixture, and taking the per cent, from tables. Directions. — Weigh out about 50 c.c. of the wine in a small flask and transfer it with 100 c.c. of water to a 500-c.c. round- N bottomed distilling-flask. Neutralize free acid with — sodium hydroxide and add 0.5 gram of tannin, if necessary, to pre- vent frothing. Distil off about 100 c.c. into a 150-c.c. tared flask which should be provided with a cork, perforated to re- ceive the condenser-tip, and carrying a mercury-valve to pre- vent loss of alcohol. Weigh the distillate, mix it thoroughly, and take its specific gravity at IS.'^S C. with a pyknometer. The percentage of absolute alcohol by weight corresponding to the observed density will be found in Table X, page 203. Example. — If A is the percentage of absolute alcohol in the sample, a that in the distillate, W and w the weights of the sample and distillate respectively, then A = ™-. Notes. — If the specific gravity of the wine is known, weighing may be avoided by carefully measuring both sample and distillate at 15. "5 C. The corresponding percentage of alcohol by volume may be found by appropriate tables. (See Sadtler's Industrial Organic Chemistry.) In the case of distilled liquors about 30 grams are diluted lOOD: ANALYTICAL METHODS: FERMENTED LIQUORS. 19I to 150 c.c, 100 c.c. distilled, and the per cent, of alcohol by weight determined as above. The object of neutralizing the wine with sodium hydrox- ide is to prevent the distillation of volatile acids, principally acetic. A certain amount of volatile ethers may also pass over into the distillate, but in most cases it is so slight that its influence may be neglected. Extract. — Dry Wines. — Weigh out about 50 c.c. in a small flask, transfer to a platinum dish having a flat bottom, and evaporate on the water-bath to the consistency of syrup. Then heat the residue in the oven at 100° C. for two hours and a half, cool in a desiccator, and weigh. Sweet Wines. — ^Weigh out 10 c.c, dilute to 100 c.c, and evaporate 50 c.c. as directed above. Notes. — The extract is composed mainly of dextrins, sugars, organic acids, nitrogenous substances, and mineral matters. Of these the dextrins and sugars form the chief part, the proteids, however, amounting to about ten per cent, in the case of beer made from malt. Ash. — Ignite the extract at a very low red heat. Free Acids: Total Acidity Calculated as Tartaric N Acid. — Titrate 10 c.c. of the wine with — sodium hydroxide. The end-point is reached when a drop of the liquid placed upon faintly-red litmus paper produces a blue spot in the middle of the portion moistened. Calculate the results as N tartaric acid. One c.c. ■ — sodium hydroxide = 0.0075 gram of tartaric acid. Volatile Acids Calculated as Acetic Acid. — Measure 50 c.c. of wine into a 300-c.c. flask provided with a cork hav- ing two perforations. One is fitted with a tube 6 mm. in diameter and blown out to a bulb 40 mm. in diameter a short 192 AIR, WATER, AND FOOD. distance above the cork; this tube is connected with a con- denser. The other perforation carries a tube reaching nearly to the bottom of the flask and drawn out to a small, aperture at its lower end; this is connected with a 500-c.c. flask con- taining water. Heat both flasks to boiling; then lower the flame under that containing the wine and continue the distil- lation by means of steam until 200 c.c. have gone over. Tit- N rate the distillate with — sodium hydroxide, using phenolph- thalein as an indicator. Calculate the results as acetic acid. N One c.c. — sodium hydroxide = 0.0060 gram of acetic acid. Fixed Acids Calculated as Tartaric Acid. — These may be found by calculating the volatile acids as tartaric and subtracting the result from the total tartaric acid found by direct titration. Coloring Matters- — The various aniline colors are gen- erally used in artificially colored wines, the color most com- monly occurring being fuchsine. Cazeneuve Reaction. — Add 0.2 gram of precipitated mer- curic oxide to 10 c.c. of the wine, shake for one minute and filter. Pure wines give a filtrate which is colorless or light yellow, while the presence of a more or less red coloration in- dicates the presence of an aniline color. Detection of Fuchsine and Orseille. — To 20 c.c. of wine add 10 c.c. of basic lead acetate solution, heat slightly, and mix by shaking. Filter into a test-tube, add 2 c.c. of amyl alco- hol, and shake. If the amyl alcohol be colored red, separate it and divide it into two portions. To one add hydrochloric acid, to the other ammonia. If the color is due to fuchsine, the amyl alcohol will be decolorized in each case; if due to orseille, the ammonia will change the color of the amyl alco- hol to purplish violet. food: analytical METHODS: FERMENTED LIQUORS. 1 95 Detection of Salicylic Acid. — Spica's Method. — Acidify 100 c.c. of the wine with sulphuric acid and extract with ether. Evaporate the extract to dryness, warm the residue carefully with one drop of concentrated nitric acid and add two or three drops of ammonia. The presence of salicylic acid is in- dicated by the formation of a yellow color, due to ammonium picrate, and may be confirmed by immersing a thread of fat- free wool, which will be dyed a permanent yellow. Girard's Method. — Extract a portion of the acidified liquor with ether as in the preceding method, evaporate the extract to dryness spontaneously, and extract the residue with petro- leum ether. Evaporate the petroleum ether extract, dissolve the residue in water and add a few drops of a very dilute solu- tion of ferric chloride. A violet-red color indicates salicylic acid. Beer and Other Malt Liquors. — Before analysis the sample must be thoroughly 'shaken in a large flask, in order to remove carbon dioxide. Specific Gravity. — Taken with a pyknometer or Sprengel tubeat is.°5 C. Alcohol by Weight. — Determined as in the analysis of wine, using 100 c.c. of the sample and 50 c.c. of distilled water. Extract and Ash. — Determined as in the analysis of dry wines. Free Acids. — ^Titrated as in the analysis of wine. Fixed acids, consisting principally of lactic and succinic, are calcu- lated as lactic acid. Volatile acids are calculated as acetic N acid. One c.c. of — sodium hydroxide = 0.0090 gram of lactic acid. Nitrogen. — ^Weigh out about 20 c.c. of the sample, transfer it to a 750-c.c. round-bottomed flask, and evaporate almost to dryness on the water-bath. Determine the nitrogen in the residue as on page 92. APPENDIX A. Table I. TENSION OF AQUEOUS VAPOR IN MILLIMETERS OF MERCURY FROM 0° TO 30°.9 C, REDUCED TO 0° AND SEA-LEVEL. o'.o. o».i. 0*.2. o°.3- o°.4. o°-S. o'.e. o°-7- o°-8. o'.g. 0° 4-57 4.60 4.64 4.67 4.70 4-74 4-77 4.80 4-84 4.87 I 4.gi 4.94 4.98 5.02 5-05 5-09 5.12 5.16 5-20 5.23 2 5.27 5.31 5-35 5-39 5-42 5.46 5.50 5-54 5-58 5.62 3 5.66 5.70 5-74 5-78 5-82 5-86 5-90 5.94 5-99 6.03 4 6.07 6. II 6.15 6.20 6.24 6.28 6-33 6-37 6.42 6.46 5 6.51 6.55 6.60 6.64 6.69 6-74 6.78 6.83 6.88 6.g2 6 6.97 7.02 7.07 7-12 7-17 7.22 7.26 7.31 7-36 7-42 7 7.47 7.52 7-57 7.62 7-67 7.72 7-78 7.83 7.88 7-94 8 7-99 8.05 8.10 8.15 8.21 8.27 8.32 8.38 8.43 8-49 9 8.55 8.61 8.66 8.72 8.78 8.84 8. go 8.96 g.02 g.o8 10 9.14 g.2o 9.26 9-32 9-39 9-45 9.51 9-58 g.64 9.70 II 9.77 9.83 9.90 g.96 10.03 10-09 10.16 10.23 10.30 10.36 12 10.43 10.50 10.57 10.64 10.71 10.78 10.85 10.92 10.99 11.06 13 II. 14 II. 21 11.28 11.36 11.43 11.50 11.58 11.66 11-73 11-81 14 11.88 11.96 12.04 12.12 12. 19 12.27 12.35 12.43 12.51 12-59 15 12.67 12.76 12.84 12.92 13.00 13.09 13-17 13-25 13-34 13.42 i6 13-51 13.60 13.68 13-77 13-86 13-95 14-04 14-12 14.21 14.30 17 14.40 14.49 14.58 14.67 14.76 14.86 14-95 15-04 15-14 15-23 i8 15-33 15-43 15-52 15.62 15-72 15-82 15.92 16-02 16.12 16-22 19 16.32 16.42 16.52 16.63 16-73 16.83 16.94 17.04 17.15 17.26 20 17-36 17-47 17-58 17.69 17-80 17-91 18.02 18.13 18.24 18.35 21 18.47 18.58 18.69 18.81 18.92 ig.04 19.16 19-27 19-39 19-51 22 19.63 19-75 19.87 19.99 20.11 20.24 20.36 20.48 20-61 20.73 23 20.86 20. 98 21. II 21.24 21.37 21.50 21-63 21.76 21.89 22.02 24 22.15 22.29 22.42 22.55 22. 6g 22.83 22. g6 23.10 23-24 23-38 25 23.52 23.66 23.80 23-94 24.08 24.23 24-37 24.52 24.66 24.81 26 24.96 25.10 25.25 25.40 25-55 25-70 25.86 26.01 26.16 26.32 27 26.47 26.63 26.78 26.94 27.10 27.26 27.42 27.58 27-74 27. go 28 28.07 28.23 28.39 28.56 28.73 28-89 29.06 29.23 29.40 29.57 29 29.74 29.92 30.09 30.26 30-44 30.62 30-79 30. g7 31-15 31-33 30 31-51 31.69 31.87 32.06 32-24 32-43 32.61 32.80 32. gg 33-18 195 196 APPENDIX A. Q Z s kj D ^ t— 1 W >l 5 rv 00 fl" t-^ t^ li. H z VO ■* m t^ Z, S w H (>$ M . bi S M W h w a « >j X u P3 [1 « fi W ^ H fq p« < u H Pi U h « H H in H g Z td U W s P5 t> Bi U d. •^ 00 " H M 00 H CO -* cr. ■* M CT> CO 00 00 M "■ M in « s ? o> H 00 M 00 00 00 CO -■ M -- o^ xO xO ■* .K CO 0^ r» 1 CO 00 - M M M !<- © " M. 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Table VII. TABLE OF HARDNESS, SHOWING THE PARTS OF CALCIUM CAR- BONATE (CaCOj) IN 1,000,000 FOR EACH TENTH OF A CUBIC CENTIMETER OF SOAP SOLUTION USED. 0.0 0.1 0.2 0.3 0.4 o-S 0.6 0.7 0.8 • 0.9 cu. cm. cu. cm. cu. cm. cu. cm. cu. cm. cu. cm. cu. cm. cu. cm. cu. cm. cu. cm. 0.0 0.0 1.6 3.2 I.O 4.8 6.3 7-9 9-5 II. I 12.7 14-3 15.6 16.9 18.2 2.0 19.5 20.8 22.1 23.4 24.7 26.0 27-3 28.6 29.9 31.2 3-" 32.5 33-8 35-1 36.4 37-7 39-0 40-3 41.6 42.9 44-3 4.0 45-7 47-1 48.6 50.0 51-4 52-9 54-3 55-7 57.1 58.6 5.0 60.0 61.4 62.9 64-3 65-7 67.1- 68.6 70.0 71-4 72-9 6.0 74-3 75-7 77-1 78.6 80.0 81.4 82.9 84-3 85-7 87-1 7.0 88.6 90.0 91.4 92-9 94-3 95-7 97-1 98.6 100. 101.5 8.0 103.0 104.5 106.0 107-5 109.0 no. 5 112,0 "3-5 115-0 116. 5 9.0 118. 119. 5 121. 1 122.6 124. 1 125.6 127. 1 128.6 130. 1 131-6 10. 133- 1 134.6 136. 1 137-6 139- 1 140.6 142. 1 143-7 145-2 146.8 ri.o 148.4 150.0 151. 6 153-2 154-8 156-3 157-9 159-5 161-1 162.7 12.0 164.3 165.9 167-5 169.0 170.6 172.2 173-8 175-4 177.0 178.6 13.0 180.2 181. 7 183-3 184.9 186.5 I88.I 189.7 191-3 192.9 194.4 14.0 196.0 197.6 199.2 200.8 202.4 204.0 205.6 207.1 208-7 210.3 15.0 211. 9 213-5 215. 1 216.8 218.5 220.2 221.8 223.5 225.2 226.9 Table VIII. SHOWING THE NUMBER OF CUBIC CENTIMETERS OF OXYGEN DIS- SOLVED IN 1000 CUBIC CENTIMETERS OF WATER WHEN SATURATED AT DIFFERENT TEMPERATURES, AS CAL- CULATED BY WINKLER.* Deg. Cent. Cu. Cm. Deg. Cent. Cu. Cm. Deg. Cent. Cu. Cm. 10.187 II 7.692 21 6.233 I 9.910 12 7-518 22 6 114 2 9.643 13 7-352 23 5 999 3 9-387 14 7-192 24 5 886 4 9.142 15 7-03S 25 5 776 5 8.907 16 6.891 26 5 669 6 8.682 17 6.750 27 5 564 7 8.467 18 6.614 28 5 460 8 8.260 19 6.482 29 5 357 9 8.063 20 6.356 30 5 255 10 7-873 Berichte, 22 {i88g), 1772. APPENDIX A. 201 Table IX. TOR CORRECTING THE SPECIFIC GRAVITY OF MILK ACCORDING TO TEMPERATURE. ADAPTED FROM THE TABLE OF VIETH. (Temperature in Degrees Centigrade.) Specific Gravity. 10° 11° 12° 13° 14° 15° 16° 17° 18° 19° 20' 1.025 24.1 24.3 24.5 24.6 24.7 24.9 25.1 25-3 25.4 25.6 25.9 26 25.1 25.2 25.4 25-5 25.7 25.9 26.1 26.3 26.5 26.7 27.0 27 26.1 26.2 26.4 26.5 26.7 26.9 27.1 27.4 27-5 27.7 28.0 28 27.0 27.2 27.4 27-5 27.7 27.9 28.1 28.4 28.5 28.7 29.0 29 28.0 28.2 28.4 28.5 28.7 28.9 29. 1 29.4 29-5 29.8 30.1 30 29.0 29.1 29-3 29-5 29.7 29.9 30.1 30-4 30.5 30.8 3i-i 31 29.9 30.1 30.3 30.4 30.6 30.9 31-2 31-4 31-5 31.8 32.2 32 30.9 31. 1 31.3 31-4 31.6 31.9 32.2 32-4 32.6 32-9 33-2 33 31-8 32.0 32.3 32.4 32.6 32.9 33-2 33-4 33-6 33-9 34-2 34 32.7 33-0 33-2 33-4 33-6 33-9 34.2 34-4 34-6 34-9 35-2 35 33-6 33-9 34-1 34-4 34-6 34-9 35-2 35.4 35-6 35-9 36.2 Directions. — Find tlie observed gravity in the left-liand column. Then in the same line, and under the observed temperature, will be found the corrected reading. 202 APPENDIX A. Table X. PERCENTAGE OF ALCOHOL BY WEIGHT FROM THE SPECIFIC GRAVITY AT 15°. 5 C. (HEHNER.) Per cent. Per cent. Per cent. Per cent. Sp. Gr. Alcohol Sp. Gr. Alcohol Sp. Gr. Alcohol Sp. Gr. Alcohol iS°.S C. by 15°.5 C. by I5°.S C. by 15° .5 c. by Weight. Weight. Weight Weight. I. GOOD 0.00 7 2.44 4 5.00 I 7.87 0.9999 8 7 6 5 0.0s O.II 0.16 0.21 0.26 6 5 4 3 2 I 2.50 2.56 2.61 2.67 2.72 2.78 2.83 3 2 ,1 0.9909 5.06 5.12 5.19 5-25 S-3I 0.9869 8 7 6 7.93 8.00 8.07 8.14 8.21 4 0.32 Q 8 5-37 5 8.29 3 0.37 7 5.44 4 8.36 2 0.42 0.9949 2.89 6 5.50 3 8-43 I 0.47 8 2.94 5 5.56 2 8.50 0.53 7 3-00 4 5-62 I 8.57 0.9989 0.58 6 3.06 3 5-69 8.64 8 7 6 0.63 0.68 0.74 5 4 3 3. 12 3.18 3-24 2 I 5-75 5.81 5-87 0.9859 8 7 8.71 8.79 8.86 5 4 3 0.79 0.84 o.8g 2 I 3.29 3-35 3.41 0.9899 8 7 s'-94 6.00 6.07 6 5 4 8.93 9.00 9.07 2 0.95 0.9939 3-47 6 6.14 3 9.14 I 1. 00 8 3-53 5 6.21 2 9.21 1.06 7 3-59 4 6.28 I 9.29 0.9979 8 7 6 5 4 3 1. 12 1. 19 1.25 I-3I 1.37 1.44 1.50 6 5 4 3 2 I 3-65 3-71 3.76 3.82 3-88 3-94 4.00 3 2 I 0.9889 8 7 6.36 6-43 6.50 6.57 6.64 6.71 6.78 0.9849 8 7 6 5 4 9.36 9-43 9.50 9-57 9.64 9.71 9-79 2 1.56 0.9929 4.06 6 6.86 3 9.86 I 1.62 8 4.12 5 6.93 2 9-93 1.69 7 4.19 4 7.00 I 10.00 0.9969 8 7 6 5 I -75 1. 81 1.87 1.94 2.00 6 , 5 4 3 2 I 4.25 4.31 4-37 4.44 4-50 4-56 4.62 3 2 I 0.9879 7.07 7.13 7.20 7.27 7-33 0.9839 8 7 6 10.08 10.15 10.23 10.31 10.38 4 2.06 8 7.40 5 10.46 3 2. II 7 7.47 4 10.54 2 2.17 0.9919 4.69 6 7-53 3 10.62 I 2.22 8 4-75 5 7.60 2 10.69 2.28 7 4.81 4 7.67 I 10.77 0-9959 8 2.33 2-39 1 6 5 4.87 4.94 3 2 7.73 7.80 0.9829 10.85 10.92 APPENDIX A. 203 Table X. — Continued. PERCENTAGE OF ALCOHOL BY WEIGHT. Per cent. Per cent. Per cent. Per cent. Sp. Gr. Alcohol Sp. Gr. Alcohol Sp. Gr. Alcohol Sp. Gr. Alcohol ■5°.5 C. by i5°.5 C. by 15°.5 C. by ^i'-S c. by Weight. Weight. - Weight. Weight. 0.9829 10.92 4 14-45 0.9739 18.IS 4 21.77 8 11.00 3 14-55 8 18.23 3 21.85 7 11.08 2 14.64 7 18.31 2 21.92 6 II. 15 I 14-73 6 18.38 I 22.00 5 11.23 14.82 5 18.46 22.08 4 3 2 I 11.31 11.38 11.46 11.54 11.62 0.9779 8 7 6 14.90 15.00 15.08 15-17 4 3 2 I 18.54 18.62 18.69 18.77 18.85 0.9689 8 7 6 22.15 22.23 22.31 22.38 5 15-25 5 22.46 0.9819 11.69 4 15-33 0.9729 18.92 4 22.54 8 11.77 3 15.42 8 19.00 3 22.62 7 11.85 2 15-50 7 19.08 2 22.69 6 11.92 I 15-58 6 19.17 I 22.77 5 12.00 15.67 5 19-25 22.85 4 3 2 I 12.08 12.15 12.23 12.31 12.38 0.9769 8 7 6 5 15-75 15-83 15.92 16.00 16.08 4 3 2 I 19-33 19.42 19.50 19.58 19.67 0.9679 8 7 6 5 22.92 23.00 23.08 23-15 23.23 0.9809 12.46 4 16.15 0.9719 19-75 4 23-31 8 12.54 3 16.23 8 19.83 3 23-38 7 12.62 2 16.31 7 19.92 2 23.46 6 12.69 I 16.38 6 20.00 I 23-54 5 12.77 16.46 5 20.08 ° 23.62 4 3 12.85 12.92 0-97S9 8 16.54 16.62 4 3 20.17 20.25 0,9669 8 23.69 23.77 2 I 13.00 13-08 13-15 7 6 5 16.69 16.77 16.85 2 I 20.33 20.42 20.50 7 6 5 23-85 23.92 24 . 00- 0.9799 13-23 4 16.92 0.9709 20.58 4 24.08 8 13-31 3 17.00 8 20.67 3 24.15 7 13-38 2 17.08 7 20.75 2 24.23 6 13.46 I 17-17 6 20.83 I 24.31 5 13-54 17-25 5 20.92 24.38 4 3 2 I 13.62 13.69 13-77 13-85 13.92 0.9749 8 7 6 5 17-33 17-42 17-50 17-58 17.67 4 3 2 I 21.00 21.08 21.15 ■ 21.23 21.31 0,9659 8 7 6 5 24.46 24-54 24.62 24.69 24-77 0.9789 14.00 4 17-75 0.9699 21.38 4 24.85 8 14-09 3 17-83 8 21.46 3 24.92 7 14.18 2 17.92 7 21.54 2 25.00 6 14.27 I 18.00 6 21.62 5 ■ 14.36 18.08 5 21.69 APPENDIX B. REAGENTS. AIR ANALYSIS. Barium Hydroxide. — A solution containing about 4 grams of BaO to the liter, (i c.c. = i mg. CO2, approximately.) Sulphuric Acid. — Dilute 46.51 c.c. of normal sulphuric acid to one Hter. (i c.c. = i mg. CO2.) To standardize the solution measure 25 c.c. into a weighed platinum dish, add one drop of phenolphthalein solution and titrate with the barium hydroxide to a faint pink. Evaporate to dryness on the water-bath, ignite, and weigh as barium sulphate. Standard Llme-zvater. (For Popular Tests.) — Shake one part of freshly slaked lime with 20 parts of distilled water for twenty minutes and let the solution stand overnight or until perfectly clear. This solution should be very nearly equiva- lent to the above standard sulphuric acid. Now to a liter of distilled water add 5 c.c. of a solution of 0.7 gram of phenolphthalein in 100 c.c. of 50 per cent, alcohol and add lime-water drop by drop until a slight permanent pink color is produced. Add 12.6 c.c. of the above calcium hydroxide solution. The resulting solution is the standard lime-water tised for the tests. WATER ANALYSIS. For Ammonia. — Water Free from Ammonia. — ^The am- monia-free water used in this laboratory is made by redis- tilling distilled water from a solution of alkaline permangan- 204 APPENDIX B. 205 ate in a steam-heated copper still. The apparatus used is shown in Fig. 10. Only the middle portion of the distillate is collected. Oftentimes the distillate from a good spring- water may be used. Nessler's Reagent. — Dissolve 61.750 grams KI in 250 c.c. distilled water and add a cold solution of HgClj which has been saturated by boiling an excess of the salt and allowing it to crystallize out. Add the HgClg cautiously until a slight permanent red precipitate (Hglj) appears. Dissolve this Fig. 10. — Still for Ammonia-free Water. slight precipitate by adding 0.750 gram powdered KI. Then add 150 grams of KOH dissolved in 250 c.c. of water. Make up to the liter and allow it to stand overnight to settle. This solution should give the required color with ammonia within five minutes, and should not precipitate within two hours. Alkaline Permanganate. — Dissolve 233 grams of the best stick potash in 350 c.c. of distilled water. Filter this strong 206 APPENDIX B. solution, if necessary, through a layer of glass wool on a por- celain filter-plate. Dilute with 700 to 750 c.c. of distilled water to a sp. gr. of 1.125, add 8 grams of potassium per- manganate crystals, and boil down to one liter to free the solution from nitrogen. Each new lot of reagent must be tested before being used, but when the chemicals used are all good there should be no correction needed for ammonia in the solution. Standard Ammonia Solution. — Dissolve 3.8215 grams chemically pure NH4CI in a liter of water free from ammo- nia. This is the strong solution from which the standard solution is made by diluting 10 c.c. to a liter with water free from ammonia. One c.c. of the standard solution = o.ooooi gram nitrogen. This solution, like the nitrite standard and other dilute solutions, must be preserved in sterilized bottles protected from dust and organic matter. For Nitrites.— 5" toMc^ord Nitrite Solution.— The. pure sil- ver nitrite used in making this solution is prepared by the double decomposition of silver nitrate and potassium nitrite, and repeated crystallizations from water of the rather dififi- cultly soluble silver nitrite, i.i grams of this silver nitrite are dissolved in nitrite-free water, the silver completely pre- cipitated by the addition of the standard salt solution used in the determination of chlorine, and the solution made up to I liter. 100 c.c. of this strong solution are diluted to i liter, and ID c.c. of this last solution again diluted to i liter. The final solution is the one used in preparing standards, i c.c. = o.ooooooi gram nitrogen. Hydrochloric Acid. — i part of pure HCl (sp. gr. 1.20) is diluted with three parts water. Sidphanilic Acid. — Dissolve 8 grams (Kahlbaum's) in i liter of water. This is a saturated solution. Naphtylamine Hydrochlorate. — Dissolve 8 grams of a- APPENDIX B. 207 naphtylamine in 992 c.c. of water and add 8 c.c. of strong HQ. (Keep in the dark.) Ilosvay's Modification. — (a) Sulphanilic Acid: Dissolve 0.5 gram of sulphanilic acid in 150 c.c. of acetic acid, sp. gr. 1.04. {b) Naphtylamine Acetate: Boil o.i gi'am of a-naphtyla- mine in 20 c.c. of water, filter through a plug of washed ab- sorbent cotton, and add 180 c.c. of acetic acid, sp. gr. 1.04. For Nitrates. — Standard Nitrate Solution. — Dissolve 0.720 gram of pure recrystallized KNO3 in i liter of water. Evaporate 10 c.c. of this strong solution cautiously on the water-bath, moisten quickly and thoroughly with 2 c.c. of phenol-disulphonic acid, and dilute to i liter for the stand- ard solution. I c.c. ^ 0.00000 1 gram nitrogen. Phenol-disulphonic Acid. — Heat together 3 grams synthetic phenol with 37 grams pure, concentrated H2SO4 in a boil- ing-water bath for six hours. For Kjeldahl Process. — Sulphuric Acid. — Sp. gr. 1.84. This should be free from nitrogen. May be obtained from Baker and Adamson, Easton, Pa. Potassium Hydroxide. — Dissolve 350 grams of the best stick potash in 1.25 liters of water and boil down to some- thing less than a liter with 3 grams of permanganate crystals. When cold, dilute to a liter with water free from ammonia. For Chlorine. — Salt Solution. — Dissolve 16.48 grams of fused NaCl in a liter of distilled water. For the standard so- lution dilute 100 c.c. of this strong solution to i liter, i c.c. = o.ooi gram chlorine. Potassium Chromate. — Dissolve 50 grams neutral K2Cr04 in a little distilled water. Add enough AgNOg to produce a slight red precipitate. Filter and make the filtrate up to a liter with water free from chlorine. Milk of Alumina for Decolorization. — Dissolve 125 grams of potash or ammonia alum in a liter of distilled water. Pre- 208 APPENDIX B. cipitate the A1(0H)3 by the cautious addition of NH4OH. Wash the precipitate in a large jar by decantation until *free from chlorine, nitrites, and ammonia. For Hardness. — Standard Calcium Chloride Solution. — Dissolve 0.200 gram of pure Iceland spar in dilute HCl, tak- ing care to avoid loss by spattering, and evaporate to dryness several times, to remove the excess of acid. Dissolve the calcium chloride thus formed in i liter of water. Standard Soap Solution. — Dissolve 100 grams of the best white, dry castile soap In a liter of 80 per cent, alcohol. Of this strong solution dissolve 75-100 c.c. in a liter of 70 per cent, alcohol. This solution must have 70 per cent, alcohol added to it until 14.25 c.c. of it give the required lather with 50 c.c. of the above CaClj solution. Erythrosine Indicator. — Dissolve o.i gram of erythrosine in I liter of water. For Iron. — Standard Iron Solution. — Dissolve 0.86 gram of ferric ammonium alum, (NH4)2S04.Fe2(S04)3.24H20, or a corresponding amount of the potassium salt in 500 c.c. of water, add 5 c.c. HNO3 (1.20), and dilute to i liter, i c.c. ^ 0.000 1 gram Fe. Potassium Sulphocyanide. — 5 grams per liter. Hydrochloric Acid. — i part HCl (sp. gr. 1.20) to i part of water. Potassium Permanganate. — 5 grams KMnO^ in i liter of water. For Dissolved Oxygen. — (0) 48 grams of MnS04.4H20 in 100 c.c. of water. (b) 360 grams of NaOH and 100 grams of KI in i liter of water. (c) HCl, sp. gr. 1.20. Sodium Thiosulphate Solution. — Dissolve 25 grams of pure recrystallized sodium thiosulphate in i liter of water. Dilute APPENDIX B. 209 100 c.c. to I liter and standardize against a known KjCrjOy solution. For Lead- — Standard Lead Solution. — To a strong solu- tion of lead acetate add a slight excess of H2SO4, filter off and wash the precipitate. Dissolve it in ammonium acetate solution, made by neutralizing glacial acetic acid with strong ammonia. Make up to a known volume and determine thelead in an aliquot part by precipitating with KaCrjOy and weigh- ing the lead chromate. Dilute an aliquot part to make a con- venient standard, say about i c.c. = o.ooi gram of Pb. FOOD ANALYSIS. For Milk Analysis- — Gasolene (Petroleum Ether). — ^Gaso- lene, sp. gr. 86° B., which leaves no residue upon evaporation at 60° F. Fehling's Solution. — (a). Dissolve 69.28 grams of C.P. crystallized copper sulphate, carefully dried between blotting- paper, in I liter of water and add i c.c. of strong sulphuric acid. (b) Dissolve 346 grams of sodium potassium tartrate and 80 grams of sodium hydroxide in i liter of water. Potassium Ferrocyanide. — Dissolve i part in 50 parts of water. Acid Mercuric Nitrate.- — Dissolve mercury in double its weight of nitric acid (sp. gr. 1.42) and dilute the solution with five times its volume of water. Fuchsin Sulphurous Acid. — Dissolve i part of a rosaniline salt in 1000 parts of water and add enough strong sulphurous acid to destroy the red color on standing. For Butter Analysis. — Pumice. — Bits of ignited pumice, about the size of a pea, dropped while hot into water and bottled for use. 2IO APPENDIX B. Alcohol (for Reichert-Meissl method). — 95 per cent, alco- hol redistilled from potassium hydroxide. Potassium Hydroxide (for Reichert-Meissl method). — One part good quality caustic potash dissolved in one part of water. Glycerine-soda (for Leffman-Beam method). — Add 20 c.c. of a 50 per cent, solution of sodium hydroxide to 180 c.c. of pure concentrated glycerine. The soda must be as nearly free from carbonate as possible. lodo-mercuric Solution. — Dissolve 25 grams of iodine in 500 c.c. of 95 per cent, alcohol; dissolve also 30 grams of mercuric chloride in 500 c.c. of 95 per cent, alcohol. Mix the two solutions and filter after standing 24 hours. Potassium Iodide. — Dissolve 150 grams of potassium iodide in i liter of water. For Cereals. — Anhydrous Ether. — Wash ordinary ether several times with distilled water and add solid caustic potash until most of the water has been removed. Then add small pieces of clean metallic sodium until there is no further evolu- tion of hydrogen gas. The ether thus prepared should be kept over metallic sodium and the bottle should be only lightly stoppered, in order to allow of the escape of any accu- mulated gas. Potassium Sulphide. — Dissolve 40 grams of the crystal- lized salt in I liter of water and filter. Potassium Hydroxide (for Kjeldahl process). — Sp. gr. = 1.25. Dilute a liter of this solution to about 1.25 liters and boil down to something less than a liter with 3 grams of po- tassium permanganate. When cold dilute to a liter. Phospho-tungstic Acid. — Dissolve 50 grams of the crystal- lized acid in dilute hydrochloric acid, containing 25 grams of HCl to the liter. Basic Lead Acetate. — Boil for half an hour 440 grams of APPENDIX B. 211 lead acetate and 264 grams of litharge in 1500 c.c. of water. Cool and dilute to 2 liters. Allow to settle and siphon off the clear liquor. (Sp. gr. about 1.27, containing about 35 per cent, of the basic salt.) Millon's Reagent. — Dissolve mercury in twice its weight of nitric acid (sp. gr. i .42) and dilute the solution obtained with three times its volume of water. BIBLIOGRAPHY. The following list comprises some of the more important works bearing on the subjects treated in the preceding pages. A. bibliography of the chemistry of foods complete to 1882 may be found in the Second Annual Report of the New York State Board of Health, and more or less complete bibliographies are to be found in Sadtler's "Industrial Or- ganic Chemistry" and Blyth's "Composition and Analysis of Foods." AIR. Air and Rain. R. Angus Smith. Longmans, Green & Co. London. 1872. Air and Its Relations to Life. Walter N. Hartley. D. Appleton & Co. New York. 1875. Report on the Air of Glasgow. E. M. Dixon. Robert Anderson. Glas- gow. 1877. Recherches sur I'Air Confine. A. Brand. Bailliere et Fils. Paris. 1880. Air Analysis. J. A. Wanklyn and W. J. Cooper. Kegan Paul, Trench, Triibner & Co. London. 1890. Les Poisons de I'Air. N. Grehaut. Baillifere et Fils. Paris. i8go. Treatise on Hygiene and Public Health. Vol. I. Thomas Stevenson and S. F. Murphy. Blakiston, Son & Co. Phila. 1892. Air and Water. Vivian B. Lewes. Methuen & Co. London. 1892. Methods for the Determination of Organic Matter in Air. D. H. Bergey. Smithsonian Institution. Washington, D. C. 1896. The Detection and Measurement of Inflammable Gas and Vapor in the Air. Frank Clowes. Crosby, Lockwood & Son. London. 1896. VENTILATION. Heating and Ventilation of the New Building, Mass. Inst. Tech. S. H. Woodbridge. Tech. Quart., 2, 76. 1888. 213 214 BIBLIOGRAPHY. Heating and Ventilation. J. S. Billings. Sanitary Engineer. New York. 1893. Heating and Ventilating Buildings. Rolla C. Carpenter. John Wiley & Sons. New York. 1895. WATER. Report of the Royal Commission on Water Supply. Great Britain Par- liamentary Documents. London. 1869-70. Sixth Report of Rivers Pollution Commission, Great Britain. London. 1876. Potable Waters. C. Ekin. 1880. Water Supply (Considered mainly from a Chemical and Sanitary Stand- point). W. R. Nichols. John Wiley & Sons. New York. 1883. Water Analysis for Sanitary Purposes. E. Frankland. John Van Voorst. London. 1890. The Organic Analysis of Potable Waters. J. A. Blair. 1890. Drinking Water and Ice Supplies. T. Mitchell Prudden. G. P. Putnam & Sons. New York. 1891. Potable Water. Floyd Davis. Silver, Burdett & Co. New York. 1891. The Action of Water on Lead. John Henry Garrett. H. K. Lewis. London. 1891. Treatise on Hygiene and Public Health. Vol. I. Thomas Stevenson and S. F. Murphy. Blakiston, Son & Co. Phila. 1892. Examination of Water for Sanitary and Technical Purposes. Henry Leffman. Blakiston, Son & Co. Phila. 1895. Water Supply (Considered Principally from a Sanitary Standpoint). W. P. Mason. John Wiley & Sons. New York. 1896. Water Analysis. J. A. Wanklyn and E. T. Chapman. Tenth Ed. Kegan Paul, Trench, Trflbner & Co. London. 1896. Water and Water Supplies. John C. Thresh. Rebman Pub. Co. Lon- don. 1896. A Simple Method of Water Analysis. John C. Thresh. J. & A. Churchill. London. 1898. Examination of Water (Chemical and Bacteriological). William P. Mason. John Wiley & Sons. New York. 1899. The Microscopy of Drinking Water. Geo. C. Whipple. John Wiley & Sons. New York. 1899. Micro-Organisms in Water. Percy F. Frankland and Mrs. Percy F. Frank- land. London. 1894. Mikroskopische Wasseranalyse. Carl Mez. J. Springer, Berlin. 1898. Water Softening and Scientific Filtration. Walter George Atkins. E. & F. N. Spon. London. 1880. Sewage Disposal in the United States. Geo. W. Rafter and M. N. Baker. D. Van Nostrand & Co. New York. 1894. Les Eaux-d' Alimentation, £puration, Filtration, Sterilization. Edm. Guinochet. Baillifere et Fils. Paris. 1894. BIBLIOGRAPHY. 2 1 5 The Filtration of Public Water Supplies. Allen Hazen. John Wiley & Sons. New York. 1895. Sewage Disposal on the Farm and Protection of Drinking Water. Theo- bald Smith. U. S. Dept. Agr., Farmers' Bull. 43. 1896. Water and Its Purification. Samuel Rideal. London. 1897. Water Purification at Louisville, Ky. Geo. W. Fuller. D. Van Nostrand Co. New York. 1898. Report on Water Purification at Cincinnati, O. Geo. W. Fuller. Board of Trustees, Cincinnati. 1899. Report of Filtration Commission, Pittsburgh, Pa. 1899. National Board of Health Report for 1882. State Board of Health Reports for Massachusetts, Michigan, Illinois, Ohio. The Mass. Reports, for 1872-75 and 1890-1900, especially, contain many valuable papers, the following being some of the most important of them : Chemical Examination of Water and Interpretation of Analyses. Thomas M. Drown. Rep. Mass. State Board of Health, 1892, 319. Discussion of Special Topics Relating to the Quality of Public Water Sup- plies. F. P. Stearns and T. M. Drown. Rep. Mass. State Board of Health, 1890, 717. On the Amount of Dissolved Oxygen contained in Waters of Ponds and Reservoirs at Different Depths. Thomas M. Drown. Rep. Mass. St.ate Board of Health, 1891, 373. On the Amount of Dissolved Oxygen contained in Waters of Ponds and Reservoirs at Different Depths in Winter Under the Ice. Thomas M. Drown. Rep. Mass. State Board of Health, 1892, 333. On the Mineral Contents of Some Natural Waters in Mass. Thomas M. Drown. Rep. Mass. State Board of Health, 1892, 345. The Effect of the Aeration of Natural Waters. Thomas M. Drown. Rep. Mass. State Board of Health, 1891, 385. In addition to the above the following papers contain much information of value on special topics relating to vi^ater supply and water analysis : Chemical Examination of Drinking Water. Thomas M. Drown. Proc. Soc. Arts., M. I. T., 1887-8, 87. The Analysis of Water— Chemical, Microscopical, and Bacteriological. Thomas M. Drown. J. N. E. Water Works Assoc, 4 (1889), 79. On the Loss on Ignition in Water Analysis. Thomas M. Drown. Tech, Quart., 2(1888), 132. The Odor and Color of Surface Waters. Thomas M. Drown. Tech, Quart., I (1888), 250. Reduction of Nitrates by Bacteria. Ellen H. Richards and George W. Rolfe. Tech. Quart., 9 (1896), 40. The Purification of Water by Freezing. Thomas M. Drown. J. N. E. Water Works Assoc, 8 (1893), 46. 2l6 BIBLIOGRAPHY. The Filtration of Natural Waters. Thomas M. Drown. J. of the Assoc, of Eng. Soc, 9 (iSgo), 356. FOOD. The list given here is limited to books published since 1890. Trait§ G6n6ral d'Analyse des Beurres. A. J. Zune. H. Lamartin. Paris. 1892. Analyse des MatiSres Alimentaires et Recherche de Leur Falsifications. Ch. Girard et A. Dupr6. Vve. Ch. Dunod & P. Vicq. Paris. 1894. Animal and Vegetable Oils, Fats, Butters and Waxes. C. R. Alder Wright. Griffin & Co. London. 1894. A Handbook of Industrial Organic Chemistry. S. P. Sadtler. J. B. Lippincott Co. Phila. 1895. Chemistry of Wheat, Flour, and Bread. Wm. Jago. Simpkin Marshall. London. 1895. Foods : Their Composition and Analysis. Alexander W. Blyth. Griffin & Co. London. 1896. Analysis of Milk and Milk Products. Henry Leffman and William Beam. Blakiston, Son & Co. Phila. 1896. The Analysis of Food and Drugs. Part I : Milk and Milk Products. T. H. Pearmain and C. G. Moor. Bailliere, Tindall & Cox. London. 1897. Principles and Practice of Agricultural Analysis. Harvey W. Wiley. Chem. Pub. Co. Easton, Pa. 1897. Testing Milk and Its Products. E. H. Farrington and F. W. Woll. Men- dota Book Co, Madison, Wis. iSgB. Chemical Analysis of Oils, Fats, and Waxes. J. Lewkowitsch. Mac- millan & Co. London. 1898. Commercial Organic Analysis. A. H. Allen. Third Ed. Rev. by H. Leffman. Blakiston, Son & Co. Phila. 1898. Die Untersuchung landwirtschaftlich und gewerblich wichtiger Stoffe. J. Konig. Paul Parey. Berlin. 1898. Our Secret Friends and Foes. Percy Frankland. London. 1893. Die Menschlichen Nahrungs-u. Genussmittel. J. Konig. Julius Springer. Berlin. 1893. Foods and Dietaries. R. W. Burnet, M.D. P. Blakiston, Son & Co. Phila. 1893. Food and Its Functions. James Knight. Blackie & Son. London. 1895. The Food Products of the World. Dr. Mary E. Green. The Hotel World. Chicago. 1895. The Story of Germ Life. H. W. Conn. Appleton & Co. New York. 1897. The Relation of Food to Health. George H. Townshend. Witt Publish- ing Co. St. Louis. 1897. BIBLIOGRAPHY. 21/ Food Materials and Their Adulterations. Ellen H. Richards. Home Science Pub. Co. Boston. 1898. Plain Words About Food. The Rumford Kitchen Leaflets. Ellen H. Richards, Ed. Home Science Pub. Co. Boston. 1899. The following bulletins of the United States Department of Agriculture will also be found useful for study or reference on the general question of food: Office of Experiment Stations, Bulletins, No. 9. Fermentations of Milk. 1892. II. Analyses of American Feeding Stuffs. 1892. 21. Chemistry and Economy of Food. 1895. 25. Dairy Bacteriology. 1895. 28. (Rev. Ed.) Chemical Composition of American Food Materials. 1895. 29. Dietary Studies at the University of Tennessee. 1896. 31. " " " " " " Missouri. 1896. 32. " " " Purdue University. i8g6. 34. Carbohydrates of Wheat, Maize, Flour, and Bread. 1S96. 35. Food and Nutrition Investigations in New Jersey. 1896. 37. Dietary Studies at the Maine State College. 1897. 38. " " — Food of the Negro in Alabama. 1897. 40. " " in New Mexico. 1897. 43. Composition and Digestibility of Potatoes and Eggs. 1897. 44. Metabolism of Nitrogen and Carbon in the Human Organism. 1897. 45. A Digest of Metabolism Experiments. 1897. 46. Dietary Studies in New York City. 1898. 52. Nutrition Investigations in Pittsburgh, Pa. 1898. 53. " " at the University of Tennessee. 1898. 54. " " in New Mexico. 1898. 55. Dietary Studies in Chicago. t8g8. 63. Experiments on the Conservation of Energy in the Human Body. 1899. 66. Creatin and Creatinin. 1899. 67. Bread and Bread Making. 1899. 69. Experiments on the Metabolism of Matter and Energy in the Human Body. 1899. 71. Dietary Studies of Negroes. 1899. 75, " " " University Boat Crews. 1900. Division of Chemistry , Bulletins. No. 13. Foods and Food Adulteration — (Nine Parts). 1887-98. 45. Analyses of Cereals. 1895. 46. Official Methods of Analysis. 1895. 50. Composition of Maize. i8g8. 2 1 8 BIBLIOGRAPHY. Farmers' Bulletins. No. 23. Foods : Nutritive Value and Cost. 1894. 29. Souring of Milk. 1895. 34. Meats: Composition and Coolcing. i8g6, 74. Milk as Food. 1898. 85. Fish as Food. 1898. 93. Sugar as Food. 1899. 112. Bread and tlie Principles of Bread Making. 1900. INDEX. PAGE Acceptable water, requirements for 68 Acid, benzoic, in milk 16^ , boric, in milk, detection of 168 , carbonic, in water, estimation of i n , hydrochloric, reagent for iron determination 208 " " " nitrite test 206 mercuric nitrate, reagent 209 , phenol-disul phonic, reagent 207 , salicylic, in milk, detection of 168 "wine, " " 193 , sulphanilic, reagent for nitrite test 206, 207 , sulphuric, " " air analysis 204 " " " Kjeldahl process 207 Acidity of milk, determination of 151 Acids, in beer, " " 193 , in wine, " " igi Adamkievvicz reaction 186 Adams' method for fat in milk 154 Adulterants in milk 166 Adulteration, definition of 137 , extent of 139 , special cases of 141 Air, carbon monoxide in , 16 , dust in 18 , expired, composition of lo , importance of 3 , inspired, composition of 10 , organic matter in 41 , water- vapor in 14 Albumin, in milk, determination of 165 Albumipoid ammonia, determination of 86 , relation to organic nitrogen 94 2ig 2 20 INDEX. PAGE Alcohol, in liquors, determination of 190, 193 , reagent for butter analysis 210 , tables for calculating from specific gravity 202 Alkaline permanganate, reagent 205 Alkalinity of milk, determination of 152 water, " " 105 Alum, in water, estimation of 117 Amides, in wheat, determination of 187 Ammonia-free water, reagent 204 Ammonia, standard solution 206 Aniline colors, in milk, detection of 167 Annatto, in milk, detection of 167 Aqueous vapor, table of tension of 195 Ash, in liquors, determination of 191, ^93 of cereals, " " 1 83 milk, composition of „ . , 154 , determination of 1 53 Babcock method for fat in milk 156 Barium hydroxide, reagent for air analysis 204 Basic lead acetate, reagent 210 Beer, examination of , . . . 193 " Behavior on ignition " of water residues 103 Bibliography 213 Biological examination of water 116 Biuret reaction 185 Brook-water, characteristics of 72 Butter, "aroma" of 171 , complete analysis of 181 , composition of 169 Buttsr-fat, composition of 170 , examination of 1 71 , rancidity of 171 Calcium chloride, standard solution of 208 Cane-sugar, in milk, detection of 166 Caramel, in milk, detection of 167 Carbohydrates, food value of 127 in cereals, estimation of 1 83 Carbonaceous matter, in water, estimation of g8 Carbon dioxide a disturbing factor 12 in air, determination of , 27 in water, determination of m , essential property of 21 , weight of cubic centimetre of ig6 monoxide, in air, detection of 38 INDEX. 22 1 PAGE Carbon-monoxide, in air, determination of 3g , presence of , i6 Casein, in milk, determination of , 165 Cazeneuve reaction .1 102 Cereals, analysis of 182 , composition of , . . . . 130 Chlorine, in water, determination of gg in well-water 78 , source of normal 5g Clark's method for hardness of water 103 Cohen and Appleyard method for carbon dioxide 33 Collection of water samples , 82 Color of waters, estimation of in , source of 58 standards for water analysis iii Coloring-matters, in butter, detection of 181 , in milk, " " 167 , in wine, " " Ig2 Cream, in milk, estimation of 150 " Crowd-poison " i3 Cycle of nitrogen , 53 Defren's method for milk-sugar 163 Dietaries 132 Dissolved oxygen, in water, determination of 107 Dust, in air, estimation of 42 , presence of i3 Edestin, in wheat, determination of 187 Erythrosine, reagent for water analysis 208 Ether, anhydrous, reagent 210 Expired air, composition of 10 Extract, in liquors, determination of 191, 193 Extraction apparatus for fat in milk 156 Fat, in milk, methods for estimation of 154 Fats and oils, in cereals, estimation of i»3 , food value of ...• 126 Fehhng's solution, reagent for sugars 209 Fibre, crude, determination of 189 Filtration 74 Fitz's method for carbon dioxide 35 Fixed acids in butter, estimation of I74 Food, chief dangers in use of 142 , definition of r 123 , necessity for examination of 6 222 INDEX. PAGE Food, importance of 5 , methods of analysis of 146 principles 1 24. , sanitary aspect of 7 values, necessity for knowledge of 133 , variation in nitrogen content 7 Food-materials, one hundred common 13a Formaldehyde, in milk, detection of 168 Formulae for milk analysis 159 Free ammonia, in water, determination of 86 Fuchsine, in wine, detection of 192 Fuchsin-sulphurous acid, reagent 209 Gasolene, reagent 209 Gliadin, in wheat, determination of 187 Glutenin, in wheat, determination of .' 187 Glycerine-soda, reagent for butter analysis 210^ Ground-water, history of 50 Hardness of water, determination of 103 , table for 200 Heat of combustion 12& Hehner's method for butter analysis 174, hardness of water 105 Hiibl method for butter analysis lyg Ice, rules for use of 60 Ilosvay's method for nitrites in water gj Inspired air, composition of 10 Iodine value, in butter, determination of jyc lodo-mercuric solution, reagent 210 ] ron, in water, determination of lofr , standard solution for water analysis 208 Kjeldahl method for nitrogen 92, 183 , how modified for nitrates 185 , theory of 184 Kubel's method for " oxygen consumed " g8 Lake-water, characteristics of 72 Lead, in water, determination of 118 , standard solution for water analysis 209 Leff man-Beam method for butter analysis 174 Leucosin, in wheat, determination of 187 Liebermann's test l86- Lime-water, standard for air analysis 204. INDEX. 223 PAGE Xiquors, fermented, examination of igo "Loss on ignition" in water analysis loi " Luftprilfer," Wolpert's 2^ Malt extract, preparation of 189 Manganous sulphate, reag>;nt for oxygen 208 Mechanical ventilation, principles of 23 Melting-point of butter, determination of 178 Micro-organisms, in air, estimation of 40 Microscopic examination of butter 177 Milk, fermentations of 148 '" Milk of alumina," reagent for water analysis 207 , percentage composition of 147 , reaction of 1 5 1 Milk-scale, Richmond's 160 Milk-sugar, determination of 161 , optical determination of 164 Millon's reaction , l86 reagent, preparation of 211 Mineral salts, in food, importance of 128 , in water 59 , presence of, in potable water 79 Moisture, in cereals, determination of 1S2 Muscular activity and respiratory exchange 15 Naphtylamine acetate, reagent 207 hy drochlorate, reagent 206 Natural ventilation, principles of 22 Nessler's reagent, preparation of 205 Nitrate, standard solution for water analysis 207 Nitrates, in water, determination of 96 Nitrite, standard solution for water analysis 206 Nitrites, in air, determination of 39 , in water, determination of 94 Nitrogen essential to living matter 63 , cycle of 53 , in beer, determination of igi , in well-water 77 Nitrogenous compounds, why dangerous 64 matter, results of decay of 64 substances, importance of 125 NormaLwaters, table of '98 Nutritive ratio '29 Odor of water, analytical value of 74 , detection of "4 224 INDEX. O'AGE Opacity of milk, measurement of 15° Organic carbon in water. 65 matter, in air, determination of 41 nitrogen, in water, determination of 92 Organisms in water, work of 55 Orseille, in wine, detection of 192 " Oxygen consumed," determination of 98 Oxygen dissolved in water, determination of 107 , table of saturation 200 Pettenkofer method for carbon dioxide 2S Phospho-tungstic acid, reagent 2tO Physical methods of butter analysis 177 Polluted waters, examples of 199 Popular tests for carbon dioxide 33 Potassium chromate, reagent for water analysis 207 ferrocyanide, reagent for water analysis 209 hydroxide, reagent for butter analysis 210 , for Kjeldahl method 207, 210 iodide, reagent for butter analysis 210 dissolved oxygen 208 permanganate, reagent for iron 208 sulphide, reagent 210 sulphocyanide, reagent for iron 20S Predigested foods 138 Preservatives in milk l65 Pressure, influence on respiratory exchange 12 Problem of safe water 62 Proteids, in cereals, determination of total 183 milk, determination of total 165 , qualitative tests for ; 185 , separation of 186 Pumice for butter analysis 209 " Purified " water, definition of 57 " Radiator" for igniting water residues loi Reaction of milk 151 Refractive index of butter, determination of 178 Reichert-Meissl number", determination of 172 Relation of water to health 52 Residue, in water, determination of loi Respiratory exchange, explanation of 10 quotient 14 River-water, characteristics of 73 Salt, in butter, determination of 181 , in milk, determination of 166 Sanitary chemistry, scope of I INDEX. 225 PAGE Sanitary science, importance of 2 water analysis, principles involved in 66 Saponification of butter- fat 173 Sediment, in water, estimation of 11& Sewage, typical analyses of 199 Shallow wells, characteristics of water from 77 Soap, standard solution for water analysis 208 Sodium carbonate, in milk, detection of 169 chloride, standard solution for water analysis 207 Sodium hydroxide, reagent for dissolved oxygen ' 20& thiosulphate, reagent for dissolved oxygen 208 Soot, in air, estimation of; 42 Sophistication, meaning of 137 Specific gravity of butter, estimation of 178 of milk, estimation of 149 , table for correcting 201 Starch, in cereals, determination of 188 milk, detection of 16& Statement of results in water analysis 119 Storage of water, results of 57 Sucrose, in milk, detection of 16& Sugars, in cereals, determination of 18S Surface water, characteristics of 71 , summary of 75 Tension of aqueous vapor, table of 195 Total solids, in milk, determination of , 152 Trade names 140 Turbidity and sediment, cause of 74 Turbidity of water, estimation of 116 Ventilation, requirements of 26 , to test e£Sciency of 24 Vital capacity, definition of 10 Volatile acids, in butter, determination of 172 Water, added, determination of, in milk 166 Water analysis, blank form for 120 , limits of 69 , value of 80 , circulation of, on the earth 47 , illustration of contamination of 48 , daily quantity needed 4 free from ammonia, reagent 204 , general use of 5 in butter, determination of 17& , legal restrictions upon use of 43 226 INDEX. PACK Water, methods of analysis of 82 , mineral contents of 199 need of 4 , preliminary inspection of source of 66 , solvent power of 51 , table of average composition of 197 , the ideal drinking 45 classification of 71 "Water-pipes, danger from 80 Water-vapor in air 14 Well and spring waters, characteristics of 76 Werner-Schmid method for fat in milk 157 Wine, analysis of . . 190 , specific gravity of 190 Winkler's method for dissolved oxygen in water , 107 Wolpert's method for carbon dioxide 37 Xanthoproteic reaction 186 SHORT-TITLE CATALOGUE OP THE PUBLICATIONS OF JOHN WILEY & SONS, New York. London: CHAPMAN & HALL, Limited. AKEANGED UNDER SUBJECTS. Descriptive circulars sent on application. Books marked with an asterisk are sold at net prices only. All books are bound in cloth unless otherwise stated. AGRICTJITTJRE. Annsby's Manual of Oattle-feeding 12mo, $1 75 Downing's Fruits and Fruit-trees of America 8vo, 5 00 Qrotenfelt's Principles of Modern Dairy Practice. 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