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Air, Water, and Food 
 
 FROM A SANITARY STANDPOINT 
 
 BY 
 
 ALPHEUS G. WOODMAN and JOHN F. NORTON 
 
 A ssociate Professor of A ssistant Professor of 
 
 Food A nalysis ■ Chemistry of Sanitation 
 
 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, know- 
 ing full well that nothing is certain." — Henry A. Rowland. 
 
 FOURTH EDITION, REVISED AND REWRITTEN 
 TOTAL ISSUE FIVE THOUSAND 
 
 NEW YORK 
 
 JOHN WILEY & SONS, Inc. 
 
 London: CHAPMAN & HALL, Limited 
 
 1914 
 
rb° 
 
 ^ 
 
 
 Copyright, i960, 1904, 1909 
 
 BY 
 
 ELLEN H. RICHARDS and ALPHEUS G. WOODMAN 
 Copyright, 19 14 
 
 BY 
 
 ALPHEUS G. WOODMAN and JOHN F. NORTON 
 
 Stanbopc ipress 
 
 H.GILSON COMPANY 
 BOSTON. U.S.A. 
 
 LC Control Number 
 
 ""/"- llil 
 
 ©CU387556 
 
 +Lo 
 
 tmp96 028457 
 
PREFACE 
 
 Since the last edition (1909) of Air, Water, and Food was 
 published there have been distinct advances in analytical meth- 
 ods, and a changed point of view has brought about a somewhat 
 different interpretation of results. This is particularly true 
 with regard to the relation of air to health and comfort. At the 
 present time the subject is still in a somewhat transitory state. 
 In order that the book might remain useful it seemed necessary 
 to make a careful revision of the whole. 
 
 The death of one of the authors, Mrs. Ellen H. Richards, 
 made a change in authorship necessary. We are indebted to 
 Prof. R. H. Richards for permission to use any material from 
 the former edition. While realizing that the book was first 
 written from a " missionary" standpoint (Mrs. Richards' 
 strong point), it actually has been used mainly for college and 
 technical school teaching; consequently the character of part of 
 the general discussion has been considerably changed. 
 
 All of the discussion on air and water has been completely 
 
 rewritten, as has the section on milk, the older methods revised, 
 
 and numerous additions, to correspond with the latest practice, 
 
 made. As in previous editions, these discussions are intended 
 
 to be essentially elementary rather than exhaustive. 
 
 A. G. W. 
 
 J. F. N. 
 Boston, July, 1914. 
 
CONTENTS 
 
 Chapter ■ Page 
 
 I. Three Essentials of Human Existence i 
 
 II. Air and Health 9 
 
 III. Air: Analytical Methods 21 
 
 IV. Water: Its Relation to Health, Its Source and Properties.. 43 
 V. Safe Water and the Interpretation of Analyses 56 
 
 VI. Water: Analytical Methods 69 
 
 VII. Food in Relation to Human Life, Definition, Sources, Classes, 
 
 Dietaries in 
 
 Vin. Adulteration and Sophistication of Food Materials 124 
 
 IX. Analytical Methods 135 
 
 Appendices 208 
 
 Bibliography 228 
 
AIR, WATER, AND FOOD 
 
 CHAPTER I 
 
 THREE ESSENTIALS OF HUMAN EXISTENCE 
 
 Air, water, and food are three essentials for healthful human 
 life. Chemical Analysis deals with these three commodities 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 result- 
 ing from carelessness or cupidity. A large portion of the prob- 
 lems of public health come under these heads, and a discussion 
 of them in the broadest sense includes a consideration of engi- 
 neering 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 Chemistry of Sanitation as come directly under individual 
 control, or which require the education of individuals 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 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 economical 
 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 
 
2 AIR, WATER, AND FOOD 
 
 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 schoolhouses, the cleanliness of the water 
 in its reservoirs, and the reliability 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 responsible 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 inter- 
 ested public to the ventilation of college halls and dormitories, 
 as well as to the exterior appearance and location. 
 
 These results can be brought about only when the students 
 themselves appreciate the possibilities of increased mental produc- 
 tion under conditions of decreased friction, such as can be found 
 only when the requirements of health are perfectly fulfilled. 
 
 Of the three essentials, air may well be considered first, al- 
 though 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 im- 
 portant 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 abundance of 
 this substance in securing great efficiency in the human being 
 increases, we shall be led to attach more importance to the 
 sufficiency of the supply. 
 
THREE ESSENTIALS OF HUMAN EXISTENCE 3 
 
 In northern climates air is not free to all in the sense of cost- 
 ing nothing, for the coming of fresh air into the house means 
 an accompaniment of cold which must be counteracted by the 
 consumption of fuel. A mistaken idea of economy leads house- 
 holders, 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 established, 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 welfare 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 inheritance. 
 Primitive man could leave a given spot when the soil became 
 offensive, and neighbors were then too few to require con- 
 sideration; 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 pollu- 
 tion. Air is abundant and is kept in constant motion by forces 
 of nature beyond human control, so that, save in the neighbor- 
 hood 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. With- 
 out it man dies in a few days; without it the soil is barren; 
 without it air in motion parches all vegetation and carries 
 clouds of dust particles; without it there is no life. As popu- 
 lation 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 
 
4 AIR, WATER, AND FOOD 
 
 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 accumu- 
 lation 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 is 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 that it should not 
 decompose too much soap. Manufacturing 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 highlands 
 may have the first use of the water, which then percolates 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. Although 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, withdraw- 
 ing 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 them- 
 selves water which is safe to drink, which will not impair the 
 efficiency of the human machine. 
 
THREE ESSENTIALS OF HUMAN EXISTENCE 5 
 
 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 sub- 
 stances eaten are not capable of combining with the oxygen of 
 the air or of being dissolved in the water or the digestive juices; 
 of less use still is it to partake of substances which act as irri- 
 tants 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 are be- 
 ginning to consider it worth while to strive for clean water pay 
 not the least attention to the sanitary qualities 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 dis- 
 regard 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 consider- 
 ation 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 health- 
 fulness and in quality? Third, if a food-substance is normal, 
 what are its valuable ingredients and in what proportions 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 substance so 
 changed as to become a possible source of poisonous products? 
 Or has anything in the nature of a preservative 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 
 
AIR, WATER, AND FOOD 
 
 nitrogen content. This is most important to the vegetarian 
 and to institutions where economy must be practiced. The fol- 
 lowing variations in the composition of leading cereals will 
 illustrate : 
 
 Oats, maximum 
 
 Oats, minimum 
 
 Oats, American hulled . . 
 
 Corn, maximum 
 
 Corn, minimum 
 
 Water. 
 
 Nitro- 
 genous 
 substance. 
 
 Crude 
 fat. 
 
 Carbo- 
 hydrates. 
 
 Fibre. 
 
 20.80 
 
 18.84 
 
 IO.65 
 
 64.63 
 
 20.08 
 
 6. 21 
 
 6.00 
 
 2. 11 
 
 48.69 
 
 4-45 
 
 12. II 
 
 13-57 
 
 7.68 
 
 63-37 
 
 I.30 
 
 22. 20 
 
 1431 
 
 8.87 
 
 52.08 
 
 7.71 
 
 4.68 
 
 5-55 
 
 i-73 
 
 72.75 
 
 O.99 
 
 Ash. 
 
 8.64 
 
 i-34 
 2.03 
 
 3-93 
 
 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 ad- 
 ditional protein 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 mineral 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 deserve 
 to be carefully studied. 
 
 The sanitary aspect of food demands a study of normal food 
 and food value even more than of adulterants or of poisonous 
 food, ptomaines and toxines. The cultivation of intelligent 
 public opinion is most important, and each student should go 
 out from a sanitary laboratory a missionary to his fellow men. 
 That is, the office of a laboratory of sanitary chemistry should 
 be so to diffuse knowledge as to make it impossible for educated 
 
THREE ESSENTIALS OF HUMAN EXISTENCE 7 
 
 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 employed 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 functions 
 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 professionally. 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 is re- 
 ferred to such works as those of Wiley, Allen, Leach, etc., but 
 for the student who needs to study, as a part of general educa- 
 tion, only typical substances, and such methods as can be 
 carried out within the limits of laboratory exercises in a col- 
 lege 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. 
 
 Food is too generally regarded as a private, individual matter 
 rather than as a branch of social economy; it is, however, too 
 fundamental to the welfare of the race to be neglected. Society, 
 in order to protect itself, must take cognizance of the questions 
 relative to food and nutrition. 
 
 Formerly each race adapted itself to its environment and 
 
8 AIR, WATER, AND FOOD 
 
 trained its digestion in accordance with the available food 
 supply. In America to-day the question is not how to get 
 food enough, but how to choose from the bewildering variety 
 offered that which shall best promote the health and develop 
 the powers of the human being, and, what is of equal impor- 
 tance, how to avoid over-indulgence, which weakens the moral 
 fibre and lessens mental and physical efficiency. In spite of all 
 preaching, few really believe that plain living goes with high 
 thinking. Professor Patten says that the ideal of health is to 
 obtain complete nutrition. Over-nutrition as well as under- 
 nutrition weakens the body and subjects it to evils that make 
 it incapable of survival. 
 
 No other form of social service will give so full a return for 
 effort expended as the help given toward better diet for children 
 and students. Fortunately help is coming fast. The United 
 States Government is giving much study to food problems, and 
 by publications is making available the work of other countries. 
 The later bulletins listed in the bibliography at the end of this 
 volume are especially valuable. What is now needed is a gen- 
 eral recognition of the importance of the subject. 
 
CHAPTER II 
 
 AIR AND HEALTH 
 
 The air we breathe is a mixture of various gaseous substances 
 containing more or less finely divided solid particles. What 
 may be called "pure" air contains 20.938 per cent * by volume 
 of oxygen, 0.031 per cent of carbon dioxide, 78.09 per cent of 
 nitrogen, 0.94 per cent of argon and other rare gases belonging 
 to the argon group. 
 
 All the air with which we actually have to deal contains also 
 varying amounts of moisture, expressed in terms of "relative 
 humidity." Air at a low temperature can hold much less 
 moisture than at a high temperature. For example, one cubic 
 foot of air at 20 F. will hold 1.235 grains of water vapor, while 
 at 70 7.98 grains will be held. The relative humidity is the 
 ratio of the amount of moisture which the air actually contains 
 to the amount which it could hold at the same temperature if 
 completely saturated. As water vapor is lighter than dry air, 
 the higher the humidity the less will a given volume of air 
 weigh. This effect is familiar in the action of a barometer 
 which falls on the approach of a rain storm, — the reading 
 on such an instrument being dependent on the weight of air 
 above it. 
 
 Besides moisture, the air in cities may contain a variety of 
 substances such as ammonia, sulphur dioxide, sulphur trioxide, 
 etc., and almost always dust, bacteria, yeasts, and molds. 
 Samples of air f taken in the down town districts of New York 
 and Boston showed at the street level numbers of dust particles 
 per cubic foot of air varying from 170,000 to 500,000, the num- 
 
 * Benedict, Composition of the Atmosphere. Carnegie Institution, Publication 
 No. 166. 
 
 t G. C. Whipple and M. C. Whipple, Am. J. Pub. Health, 1913, 3, p. 1140. 
 
 9 
 
IO AIR, WATER, AND FOOD 
 
 ber gradually decreasing as the height above the street increased, 
 until only about 27,000 were found in the air taken from the 
 fifty-seventh floor of the Woolworth Building, 716 feet high. In 
 a house, school room or public building the numbers of dust 
 particles are equally variable, with a tendency to be somewhat 
 higher, depending on the location of the building, and whether 
 or not the air entering is purified. Thus in an investigation of 
 the air of school rooms,* few cases were found where the num- 
 bers were less than 200,000 per cubic foot, and they varied from 
 this to over 1,500,000, the greater proportion being between 
 200,000 and 600,000, much higher than is generally found in 
 outdoor air. The numbers of bacteria found in the air are small 
 compared to the dust particles, there being about 200" as many 
 in outdoor air, and even less in indoor air, in 85 per cent of the 
 samples taken in school rooms f the number of micro-organisms 
 being less than 150 per cubic foot. In country districts the 
 numbers of both dust particles and bacteria in the air are ex- 
 tremely small. 
 
 Under ordinary conditions the presence of dust and bacteria 
 has no particular significance. In fact it is the opinion of most 
 sanitarians that the danger of the spread of disease by the 
 carrying of bacteria through the air is small, the contact neces- 
 sary for this to happen being much closer than generally exists 
 in offices and schoolrooms. There are certain special cases 
 where dust particles may be harmful, — such as the dust con- 
 sisting of small particles of metal found in certain factories, 
 and the organic dust found in the air in certain rooms in textile 
 mills. Some of these dusts, such as white lead, are themselves 
 actually poisonous to the system, while others lodge in the 
 lungs and lower the vitality so that pneumonia and tuberculosis 
 are more liable to gain a footing. 
 
 Poisonous gases are occasionally found in air, — the most 
 important being carbon monoxide which comes from leaky gas 
 jets or pipes, or from a defective furnace. As this gas has al- 
 
 * Winslow, Am. J. Pub. Health, 1913, 3, p. 1158. 
 f Winslow, loc. cit. 
 
AIR AND HEALTH II 
 
 most no odor, insensibility may occur without the victim realiz- 
 ing what is taking place. For this reason it has been found 
 necessary, where this gas is used for lighting, to require the in- 
 troduction into it of some substances with strong odors. Car- 
 bon monoxide acts as a poison by combining with the haemo- 
 globin of the blood, and preventing the absorption of oxygen. 
 
 In the air of mines, methane, — or fire damp as it is called, — 
 is sometimes present. This forms an explosive mixture with 
 oxygen, and is frequently the cause of mine explosions. 
 
 Respiration. — External respiration consists of alternately 
 rilling and emptying the lungs. In the lungs, oxygen, breathed 
 in with the air, is exchanged for carbon dioxide brought to the 
 lungs by the blood. The blood leaving the lungs contains oxy- 
 gen which is carried to all parts of the body, and passes * from 
 the blood in the capillaries into the tissues where oxidation takes 
 place. The carbon dioxide formed passes back into the blood 
 and hence into the lungs. Expired air, therefore, contains less 
 oxygen and more carbon dioxide than inspired air. An average 
 composition would be, — oxygen, 16.03 P er cent; carbon di- 
 oxide, 4.38 per cent; nitrogen, etc., 79 per cent. 
 
 The process of exchange of oxygen and carbon dioxide in the 
 lungs is partly a physicalone, — that is, the vapor pressure of 
 oxygen is greater in the lungs than in the blood, and, therefore, 
 oxygen passes from the former to the latter. With carbon 
 dioxide the reverse is true. Therefore, if air high in carbon 
 dioxide is breathed into the lungs this will increase the vapor- 
 pressure of this substance, and hinder the ehmination of it from 
 the blood. But it appears to be impossible to account for the 
 interchange of gases on a purely physical basis, and, therefore, 
 it is thought that enzymes, which aid in the interchange, are at 
 work. 
 
 Comfort. — The first two theories that were advanced to 
 
 account for effects of discomfort when a room becomes " close" 
 
 were based on the supposition that the products of respiration 
 
 were poisonous w r hen taken back into the lungs. In one theory 
 
 * See Hammarsten-Mandel. "A Text-book of Physiological Chemistry." 
 
12 AIR, WATER, AND FOOD 
 
 this poisonous substance was supposed to be carbon dioxide. 
 That animals cannot live in an atmosphere composed of nitro- 
 gen and carbon dioxide, and that oxygen is necessary has long 
 been known, but it was thought that carbon dioxide had a 
 specific poisonous action and, therefore, should be present in any 
 air used for human beings, in only very small amounts. This 
 theory has been entirely disproved and carbon dioxide can no 
 longer be regarded as in itself poisonous. If too much of the 
 oxygen in the air becomes displaced by carbon dioxide it is im- 
 possible for animals to utilize the oxygen left, but this only 
 happens when the oxygen content decreases to about 12 per 
 cent. Practically such a low per cent is never found, as inter- 
 change of the air between a room and the outside is continually 
 going on around windows and through walls. If, however, the 
 oxygen is allowed to remain at about 21 per cent, very large 
 quantities of carbon dioxide may be present without any ill 
 effects. Experiments have shown conclusively * that carbon 
 dioxide cannot be blamed for discomfort in a crowded hall or 
 theatre. 
 
 The other theory, — known as the " crowd poison" theory 
 was based on some experiments which seemed to show that 
 organic poisons were given off during respiration, and that these 
 substances were the cause of the headaches and nausea some- 
 times experienced by sensitive persons in " close" rooms. At 
 the present time there are some adherents to this theory, but 
 there has been little real evidence produced in its support. The 
 first proofs of the non-poisonous character of exhalations were 
 obtained by Formanek in a long series of experiments f and 
 more recently Winslow J using the principles of anaphylaxis 
 failed to obtain any results which showed the presence of the 
 poisons (or toxins) in expired air. 
 
 At the present time it is quite generally believed that sen- 
 
 * See Crowder. "Ventilation of Sleeping Cars." Arch. Intern. Med., 191 1, 7, 
 
 PP. 85-133- 
 
 f Archiv fiir Hygiene, 1900, 38, p. 1. 
 { Loc. cit. 
 
AIR AND HEALTH 13 
 
 sations of comfort and discomfort are dependent upon the rate 
 of loss of heat from the body. If this is normal, then comfort 
 results, if either too high or too low, then discomfort, headaches 
 and nausea may follow. Just what this heat loss should be, 
 measured in any system of units, is not known, but certain of 
 the methods by which the loss takes place, and the factors 
 which influence the rate may be discussed. 
 
 There are three ways by which heat can be transferred from 
 the body to the surrounding atmosphere. (1) Evaporation. — 
 The change from the liquid to the gaseous state is accompanied 
 by an absorption of heat. Thus when water evaporates from 
 the surface of the body, heat is removed with it. (2) Trans- 
 mission (by conduction and convection). Heat passes from a 
 warm to a cold body when the two are in contact. For the 
 greater part of the year the animal body is warmer than the 
 atmosphere, and, therefore, the latter is continually receiving 
 heat from the body. Since warm air rises, convection currents 
 may be set up carrying away the heat already given up to the 
 air. (3) Radiation. — The first two methods depend directly 
 on the presence of matter. In radiation heat is transferred in 
 all directions by means of ether waves, and the medium through 
 which the radiation takes place does not necessarily become 
 heated. There is no data available on the loss of heat from the 
 body in this way, and we do not know what part it actually 
 plays in comfort. 
 
 These three methods by which heat may be given off from 
 the body may be acting simultaneously, — in fact they generally 
 are doing so, — and one or more may be negative in its action, — 
 that is may be supplying heat to the body. Further, while they 
 act entirely independently of each other, they are each in- 
 fluenced by the same conditions of the atmosphere, and it is 
 these physical conditions which are the ones capable of regu- 
 lation, and which determine good or bad ventilation. These 
 are, — temperature, humidity and motion. 
 
 Temperature. — Temperature affects evaporation, because the 
 higher the temperature of the air the more moisture is it capable 
 
14 AIR, WATER, AND FOOD 
 
 of taking up. It affects conduction, because the greater 
 the difference of temperature between two bodies the greater the 
 amount of heat passing from that at the higher to that at the 
 lower temperature. It affects convection, because convection 
 currents are started by warm air rising and cooler air taking its 
 place. 
 
 Humidity. — Heat loss by evaporation is more dependent on 
 humidity than on any other factor. Relative humidity is a 
 measure of the per cent saturation of the air by water vapor, 
 and it is obvious that the higher the humidity the less will be 
 the opportunity for the air to take up more moisture, and, 
 therefore, the less rapid the evaporation from the body. Trans- 
 mission of heat from the body is affected by the humidity, be- 
 cause moist air is a better conductor than dry air, and, therefore, 
 the higher the humidity the greater the rate of heat conduction. 
 (Relative humidity, as can be seen from a foregoing discussion, 
 is itself affected by the temperature.) 
 
 Motion. — The motion of the air influences evaporation by 
 carrying away from the body more or less rapidly the air which 
 has become completely saturated with moisture, and thus al- 
 lowing access to unsaturated air. If the air and the body are 
 perfectly quiet evaporation will be gradually retarded until it 
 is nearly zero. Convection currents are movements in the air 
 started by differences in temperature. These movements will 
 be greatly increased by any motion in the air, and, therefore, 
 the greater the motion the more rapid will be the transference 
 of heat in this way. 
 
 It is important to remember that these three factors, tem- 
 perature, humidity and motion, — are always acting simul- 
 taneously, and that there may be an increase in the rate of heat 
 loss above the normal by one or more of them at the same time 
 that the rest tend to decrease this rate. Furthermore, the same 
 factor, humidity for example, may tend to increase the heat loss 
 above the normal by one method, — perhaps by evaporation, — 
 while at the same time, the same degree of humidity may tend 
 to decrease below the normal the heat loss by another method, 
 
AIR AND HEALTH 15 
 
 perhaps by transmission. The degree of comfort felt under any 
 specified conditions is, therefore, the resultant of all effects, some 
 tending to increase and others to decrease the rate of heat loss 
 from the normal. 
 
 This can be readily illustrated. Suppose that the temper- 
 ature is 95 F., the humidity 90 per cent and there is but very 
 little motion in the air. The result is well known, — a feeling 
 of heaviness and considerable discomfort. Why? 
 
 (1) The high temperature allows the air to take up a con- 
 siderable amount of moisture, thus tending to increase the heat 
 loss by evaporation, with the consequent cooling effect on the 
 body. On the other hand, the heat loss by conduction, con- 
 vection and radiation are only very small as they depend on 
 the difference of temperature of the body and the air. 
 
 (2) The high humidity prevents the rapid evaporation of 
 moisture, and, therefore, tends to decrease the heat loss from the 
 body. This more than counteracts the increased capacity of 
 the air for moisture, due to the high temperature. On the 
 other hand, the high humidity makes the air a better conductor 
 of heat, and, therefore, tends to increase the heat loss by con- 
 duction. This, again, is counteracted by the high temperature, 
 temperature being the more important factor in this method of 
 loss. 
 
 (3) The very slight motion of the air tends to decrease the 
 heat loss by evaporation and convection. 
 
 The net result is that heat does not leave the body as rapidly 
 as it should, and we feel hot and uncomfortable. 
 
 Application of this theory of regulation of loss of heat is not 
 wholly adequate to explain all conditions. Another factor seems 
 to be involved, that of loss of moisture, apart from any loss of 
 heat which accompanies this. "Probably much of the harm 
 attributed to damp and to cold is due to diminished water cir- 
 culation, etc."* With this added factor it is possible to ex- 
 plain most of the uncomfortable conditions. The uncertainty 
 of the theory lies m the fact that we have been unable to test it 
 
 * Macfie, Air and Health. 
 
i6 
 
 AIR, WATER, AND FOOD 
 
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AIR AND HEALTH 1 7 
 
 experimentally and to determine the exact heat loss due to each 
 factor. 
 
 Hill * has plotted a series of curves which are intended to 
 represent the various conditions of comfort in terms of tem- 
 perature and humidity. Thus it is seen that a temperature of 
 55 F. and a humidity of 70 per cent gives comfort, and as the 
 temperature increases the humidity must be decreased. At 
 68° F., the temperature generally desired in the house, the 
 humidity must be around 50 per cent. 
 
 Ventilation. — In ventilating a public building or a house, it 
 is necessary to supply a sufficient quantity of air in the proper 
 condition. In most cases this condition is, that the air in the 
 room shall be at a temperature of 68° to 70 F., and with a 
 humidity of 50 to 70 per cent. As long as the humidity does 
 not go too high, it seems to be a secondary factor so far as health 
 is concerned. More discomfort is felt from overheating than 
 from any other cause. This is also true in many factories, but 
 there are some where high humidity must be considered, such 
 as is necessary to maintain in connection with certain textile 
 operations. It should be remembered that the higher the tem- 
 perature the more sensitive does one become to high humidity. 
 
 Another condition which must be met in ventilation practice 
 is that governed by the carbon dioxide content of the air. As 
 pointed out above, this substance is not itself poisonous, but it 
 is useful in serving as an index of the amount of unused air be- 
 ing supplied. The normal individual gives off from 0.6 to 0.8 
 cubic feet of carbon dioxide per hour, and this will gradually 
 accumulate in a room unless the air is continually being replaced. 
 The amount of carbon dioxide present in a room can, therefore, 
 be used to determine whether or not there is sufficient replace- 
 ment of used air by fresh air. The allowable amount of carbon 
 dioxide is about 10 parts per 10,000 of air. Amounts above this 
 may be allowed in certain special cases where the carbon dioxide 
 does not come from man or animals. If only 6 or 7 parts are 
 present, the ventilation may be considered excellent. In order 
 
 * Hill, Recent Advances in Physiology and Biochemistry. 
 
l8 AIR, WATER, AND FOOD 
 
 to accomplish this about 2000 cubic feet of fresh air per person 
 per hour must be supplied. The amounts actually recommended 
 depend somewhat on the use to which the room or building is 
 to be put, these amounts varying between 1000 cu. ft. for a 
 waiting room and 2500 for a hospital. Where it is difficult to 
 determine how many people will be present the calculations may 
 be based on the number of complete changes of air per hour, 
 these being from one to five in a residence, and from one to two 
 in an auditorium.* 
 
 It is also possible to calculate from analytical data the inter- 
 change of air going on under given conditions, and thus test the 
 efficiency of a ventilating system. If, after a room has been 
 occupied and the occupants removed, the air is analyzed for 
 carbon dioxide, the room allowed to remain a definite length of 
 time, and another analysis made, the interchange may be cal- 
 culated from a formula given by Barker: f 
 
 v =Wfc-:) 
 
 where C is the contents of the room in cubic feet, T the time in 
 hours between the original amount of carbon dioxide ki in one 
 cubic foot of air, and the final amount k 2 in one cubic foot of 
 air, a the proportion of carbon dioxide in one cubic foot of pure 
 atmospheric air, and V the interchange in cubic feet per hour. 
 
 Ventilation depends on the movement of air currents in such 
 a way as to continually supply fresh air and to remove used 
 air. This must be done so that no drafts will be felt at any 
 part of the room. The system actually used will depend on 
 the kind of building and room, — as well as on the kind of heat- 
 ing used. In the ordinary dwelling house ventilation is almost 
 always left to look after itself. Even in the best built houses 
 there is going on constantly an interchange of air around the 
 windows and doors. This is not sufficient on winter evenings 
 
 * Greene, "Elements of Heating and Ventilation," p. 23. 
 f Baker, "The Theory and Practice of Heating and Ventilation," p. 164. A 
 number of other useful ventilating formulae are also given. 
 
AIR AND HEALTH 
 
 19 
 
 when kerosene or gas lamps are burning, and most rooms soon 
 become stuffy. To aid this natural ventilation, windows, open 
 fire places and hot air furnaces are used. Excellent results may 
 be obtained from the careful use of the open window, but it re- 
 quires considerable time as well as care to operate them so that 
 no drafts will result. Where a hot air system of heating is used 
 a house may be well ventilated, — the air which is forced in 
 through registers going out after proper circulation, through ven- 
 tilators or around windows. Care should be taken to place 
 registers to get this circulation. 
 
 In a large building, — office, educational, or auditorium, — the 
 problem is somewhat different. Here it is useless to depend on 
 natural ventilation and some artificial means must be employed. 
 There are two general methods of air circulation in use, upward 
 and downward. Both have their advantages and disadvantages. 
 Upward ventilation would seem theoretically the best, as ex- 
 pired air, being warm, rises and creates an upward current, 
 which can be easily drawn into an outlet. This system can be 
 used, but it presents certain difficulties. The first is that un- 
 less air comes into the room through a very large number of 
 small holes in the floor, drafts of cold air around the feet are 
 certain to be felt. This would only be practical in an audi- 
 torium with stationary seats. Besides, objection is sometimes 
 made that odors from the clothing are made more noticeable by 
 being carried past the nose. The reverse system, downward ven- 
 tilation, seems to be more practical. Here the air is introduced 
 from the ceiling and is drawn out through ducts in or near the 
 floor. More often air is introduced from the walls of the room. 
 In this case it is necessary to so arrange the inlet and outlet 
 that air from the former will circulate around the room before 
 reaching the latter. To do this, the outlet is generally placed 
 a little below the inlet on the same wall, this being on the cold 
 side of the room. The air may be forced into the room under 
 pressure from a fan, called the plenum system, or may be drawn 
 out from the room by a fan in the outlet, called the vacuum 
 system. 
 
20 AIR, WATER, AND FOOD 
 
 In cities where there is necessarily much smoke and dirt, 
 it may be considered best to purify, in some way, the air 
 entering a building. The simplest method is to screen the in- 
 coming air through fine wire gauze or cheese cloth. A more 
 effective way is by means of air washers. All of these, and 
 there are a number of them on the market, depend on the pas- 
 sage of the air through a spray of water which removes dirt, 
 bacteria and soluble substances. Since these machines spray 
 water into the air they are also humidifiers, and may be used as 
 such, particularly in textile factories where it is necessary to 
 carry on certain operations in moist air. 
 
 It is also possible to take air out of a room, wash it, cool it 
 and send it back into the same room.* This would effect a 
 saving of coal if it were practical to operate. 
 
 Another method which has been in some use for purifying air 
 is by means of ozone. During the last year there has been much 
 discussion on this subject,! and very serious doubts have been 
 thrown on the real usefulness of this method. That ozone in 
 the presence of a large amount of moisture is a good disinfectant 
 cannot be denied, but under the dry conditions of the atmos- 
 phere its germicidal effect is small. However, in most cases it 
 is not bacteria which we need to kill, but odors. On this point 
 the evidence is not quite so clear. Most are agreed that the 
 odors disappear, but it is still a question whether the substances 
 producing them are actually destroyed, or whether the odors 
 are masked by those of ozone. From a standpoint of health, 
 this would also be immaterial if it could be proved that the 
 ozone itself was harmless to breathe. At the present time the 
 evidence seems to be the other way. 
 
 * See article on Recirculated Air. McCurdy, Am. Phys. Ed. Rev., Dec, 1913. 
 f Jordan and Carlson, /. Am. Med. Assn., 1913, 61, pp. 1007-1012; Norton, 
 Eng. Rec, 1913, 68, p. 732; Vosmaer, /. hid. Eng. Chem., 1914, 6, p. 229. 
 
CHAPTER III 
 air: analytical methods 
 
 In an investigation of the air of any room or public building 
 it is not enough to make one or two observations, as these might 
 be entirely misleading, but a sufficient number must be taken 
 to get a fair estimate of the conditions. Thus in a room, read- 
 ings of the physical instruments must be made and samples 
 for chemical analysis taken at a number of points, and these 
 repeated at intervals of five or 10 minutes until six or eight have 
 been taken. Slight changes constantly occur which are not of 
 any importance in practical work, but fortunately most of the 
 instruments and most of the methods used are not delicate 
 enough to be influenced by changes of this character. In short, 
 it is average conditions which are of importance, and which 
 should be recorded. 
 
 Physical Determinations. — Temperature. — The use of the 
 thermometer is too well known to need any detailed statement. 
 Mercurial thermometers are the most accurate for practical 
 work, but care should be taken that the bulb of the thermome- 
 ter is suspended in the air and not placed against a wooden 
 back, as in the latter case the reading lags behind the actual 
 changes in the temperature of the air. Where it is desired to 
 have a continuous record, recording thermometers are to be 
 recommended. These depend on the contraction and expan- 
 sion of a metal combination, with the changes of temperature, 
 the metal being connected with a pen which records the changes 
 on a paper disc moved by clockwork. 
 
 Pressure. — Air pressure is measured by barometers, of which 
 there are two types, — mercurial and anaeroid, both of which 
 are well known. Since the barometric reading depends on the 
 weight of the column of air above the instrument, the reading 
 
22 AIR, WATER, AND FOOD 
 
 will vary with the distance above sea level, and with the com- 
 position of the air. In the latter case the only important factor 
 is moisture. As water vapor is lighter than dry air, the larger 
 the moisture content the lighter the moist air and the less the 
 pressure. Thus a low barometric reading indicates the ap- 
 proach of a storm. 
 
 Humidity. — Relative humidity has already been described. 
 The most accurate method of measurement is by means of wet 
 and dry bulb thermometers. The rate of evaporation of water 
 into air at any one temperature depends on the amount of 
 moisture already present. Since evaporation is accompanied by 
 absorption of heat, the surface from which the water evaporates 
 will be cooled in proportion to the rate of evaporation. If the 
 bulb of a thermometer is surrounded by a film of moisture, 
 which can readily be done by means of a piece of cloth or wick 
 with one end dipped in a reservoir of water, this cooling can be 
 measured by the lowering of the temperature below that of a 
 thermometer whose bulb is surrounded by air alone, and the 
 lowering is proportional to the relative humidity. In the ap- 
 pendix will be found a table from which the relative humidity 
 can be obtained from the reading of the dry and wet bulb ther- 
 mometers. In order that the wet bulb thermometer may come 
 quickly to equilibrium an instrument called the psychrometer 
 has been devised for rapidly rotating the thermometers. 
 
 Another method of measuring the humidity is by means of 
 the hair hygrometer. In this instrument a number of horse 
 hairs are placed under tension by means of a small weight. 
 The distance to which the hairs will be stretched will depend on 
 the amount of moisture taken up from the air, — the higher 
 the moisture the greater the stretching. The weight can be 
 readily connected to an indicator which will record the rela- 
 tive humidity on a dial, or a pen can be attached, to make a 
 recording instrument, in a similar manner to that used with a 
 recording thermometer. 
 
 Motion. — Where the velocity of air is considerable, as in the 
 case of wind or in such places as ventilation ducts, measure- 
 
AIR: ANALYTICAL METHODS 23 
 
 ments can be made by the use of anemometers. However, in a 
 room, the movement of air is much too slow, and the direction 
 of currents too varied, for such an instrument to be of use. 
 The best method is by use of smoke from a joss stick or cigar.* 
 
 Dust. — The simplest method for determining dust in air is to 
 draw a measured quantity of air through a weighed tube con- 
 taining a cotton plug. For this it is necessary to have a suction 
 pump, — the variety which may be attached to a water faucet 
 is useful, — a meter, such as a gas meter, and a tube containing 
 a cotton plug. The tube with the plug should be dried in a 
 desiccator before each weighing as moisture may be absorbed 
 from the air passed through. Knowing the amount of air and 
 the increase of weight of the cotton filter, the amount of dust 
 per unit volume of air can be calculated. Where the amount of 
 dust is large, the cotton plug can be replaced by one of granulated 
 sugar. The amount of dust is then determined by dissolving 
 the sugar in water and then filtering through a weighed Gooch 
 crucible. 
 
 The most accurate determinations of dust particles can be 
 made by means of the "Dust Counter" or the "Koniscope." 
 Both of these instruments f are too expensive to be very generally 
 used. 
 
 An apparatus for taking dust samples of air has recently been 
 described by Baskerville,{ and would seem to be useful and 
 sufficiently accurate for practical purposes. 
 
 Chemical Determinations. — The first systematic study of 
 the atmosphere was made by Scheele, in 1779, shortly after the 
 discovery of oxygen. Since that time more and more accurate 
 methods have gradually been developed, culminating in that 
 used recently by Benedict. § 
 
 * Shaw, " Air Currents and the Laws of Ventilation." Cambridge, 1907. 
 
 t See "Standard Methods for the Bacterial Examination of Air," Am. Pub. 
 Health Assn., 1910, p. 38. 
 
 X J. Ind. Eng. Chem., 1914, 6, p. 238. 
 
 § For a detailed history of air analysis see Benedict, "The Composition of the 
 Atmosphere with Special Reference to its Oxygen Content," Carnegie Institution 
 of Washington, 191 2, Publication No. 166. 
 
24 AIR, WATER, AND FOOD 
 
 In practice the only chemical test made on air is that for 
 carbon dioxide. In cases of poisoning, tests may be made for 
 carbon monoxide or methane, and in experiments with respira- 
 tion, oxygen determinations together with those for carbon 
 dioxide are considered necessary. 
 
 The methods for the determination of carbon dioxide are all 
 based on absorption by alkalies, the amount of this absorption 
 being measured either by direct determination of the diminution 
 of a given volume of air, or by determination of the amount of 
 alkali used for the absorption. 
 
 Collection of Samples. — Methods for collecting samples of air 
 for chemical analysis will vary somewhat with the method and 
 apparatus used. In certain cases the sample is measured 
 directly into the analytical apparatus, while in others, — and 
 these are the more practical methods, — the sample is first col- 
 lected in a balloon or bottle. Where large amounts are needed, 
 as in the Pettenkofer method, the samples are collected in a 
 four- or six-liter bottle, the volume of which has been determined 
 by weighing both empty and filled with water. The bottle is 
 fitted with a two-hole rubber stopper with a short piece of glass 
 tubing to serve as an inlet in one hole and a long brass tube ex- 
 tending to the bottom of the bottle, in the other hole. This 
 brass tube is connected to a bellows with the valves arranged so 
 that air will be drawn out of the bottle. Pumping should be 
 continued until the air originally in the bottle has been entirely 
 replaced, which will take from 30 to 50 strokes of the bellows. 
 The stopper and tube are then removed, and the bottle closed 
 with a stopper as described on page 34. 
 
 For the Walker and the Cohen and Appleyard methods a 
 much smaller volume is all that is needed, — from 500 c.c. to 
 two liters. The simplest method is to fill the bottle with water 
 and pour it out. This has the disadvantage that expired air 
 from the collector may reach the bottle. 
 
 A better method is to fit two bottles each with a 2-hole 
 rubber stopper. In one hole of the stopper of bottle (A) (Fig. 1) 
 insert a short piece of glass tubing, and in the other a longer 
 
AIR: ANALYTICAL METHODS 
 
 25 
 
 piece of tubing extending nearly to the bottom of the bottle. 
 In the stopper of (B) insert a short piece of glass tubing just 
 reaching through the stopper, and a longer tube extending 
 nearly to the bottom, and 
 fitted with a piece of small 
 bore rubber tubing and a 
 pinch clamp. Connect the 
 short tube of bottle (B) with 
 the long tube of (A) by means 
 of a rubber tube and close 
 with a pinch clamp. Fill (B) 
 with recently boiled water, 
 open clamp (a), close clamp 
 (b) and insert stopper with 
 connections, into the bottle. 
 Then close (a). Invert (B) 
 at the point at which the sam- 
 ple is to be taken. Release 
 the pinch clamp (a) , and then 
 open the clamp (b) . The bot- . 
 tie filled with air (B) is then 
 closed with a solid rubber 
 stopper and is ready for 
 analysis. If bottle (A) is 
 larger than (B) it can be 
 used, together with the water, for taking a number of samples 
 of air. 
 
 Another method by which sampling is made easier, but which 
 does not give such accurate results, is the steam vacuum method. 
 The apparatus is set up as in Fig. 2. Steam is supplied from a 
 two-quart oil can nearly filled with water, or if preferred, from a 
 liter flask. A rubber tube and piece of glass tubing connects 
 the steam can with the inverted bottle, the size of which de- 
 pends on the method of analysis used, the tube extending to 
 within an inch of the bottom of the bottle. The bottles are 
 made for ground glass stoppers, but are fitted with rubber 
 
 Fig. i. 
 
26 
 
 AIR, WATER, AND FOOD 
 
 stoppers to which have been applied a thin coating of vaseline. 
 Too much vaseline should be avoided, as it prevents the stopper 
 staying in after the sample has been collected. The rubber 
 stoppers should be one size larger than would ordinarily be used. 
 To prepare the bottle, fill the can two-thirds full with water, 
 and boil for a few minutes to expel carbon dioxide and air. In- 
 
 FlG. 2. 
 
 vert the empty bottle over the end of the tube, and allow to 
 remain for three minutes. Keeping the bottle inverted, re- 
 move it from the, tube, and quickly insert the rubber stopper. 
 The stopper may be pushed in more securely by holding it 
 against the table with a slight pressure, and keeping it there 
 until the vacuum starts to form. When cool, the stopper should 
 
AIR: ANALYTICAL METHODS 27 
 
 project at least one-half an inch in order to be easily removed. 
 A number of bottles can be prepared in the laboratory, and quite 
 easily transported. 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 
 rinsed. 
 
 To collect the sample it is necessary only to remove the stopper, 
 taking care to hold the bottle away from the face in order to 
 prevent contamination from the carbon dioxide of the breath. 
 
 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, 
 number of doors, windows and transoms, methods of heating 
 and ventilation, and anything else which would tend to in- 
 fluence the amount of carbon dioxide present. 
 
 •In collecting samples, care must be taken to avoid currents of 
 air or the close proximity of people. Exact duplicate analyses 
 can be obtained only in empty or in 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. 
 
 Carbon Dioxide. — The most accurate analyses of air have 
 been those obtained by Benedict by means of an apparatus 
 especially designed by Dr. Klas Sonden* The analysis de- 
 pends upon the measurement of the decrease in volume of a 
 sample of air after contact with a caustic alkali solution. An- 
 other accurate apparatus on the same principle is that of Petter- 
 sen-Palmquist, f which has been modified by Rogers, { and 
 more recently by Anderson. § In all of these forms the manipu- 
 lation is rather delicate, the apparatus is bulky to transport, 
 and when obtained, the results are much more accurate than is 
 necessary for any practical work. 
 
 * A description of this will be found in Publication No. 166, Carnegie Insti- 
 tution of Washington, already referred to. 
 
 f For description see Rosenau, " Hygiene and Preventive Medicine." 
 t See catalogue of Eimer and Amend. 
 § /. Am. CJiem. Soc, 1913, 35, p. 162. 
 
28 AIR, WATER, AND FOOD 
 
 Walker Method. — The method to be most recommended for 
 practical analyses for carbon dioxide is that proposed by Walker* 
 It has been carefully studied in this laboratory t and slightly 
 modified. The results are accurate to tenths of a part per 10,000. 
 
 Principle. — To a definite volume of air, usually one to two 
 liters, is added a measured amount of standard barium hydrox- 
 ide, care being taken to avoid contact of the solution with the 
 air. After the absorption of the carbon dioxide, the solution is 
 filtered under reduced pressure through asbestos and the clear 
 barium hydroxide received into a known excess of standard 
 hydrochloric acid. The absorption bottle is rinsed out with 
 water free from carbon dioxide. The excess of acid is then 
 determined by titration with barium hydroxide. 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 absorbing solution must be 
 shaken with the air for a considerable time. 
 
 Reagents and Apparatus. — The standard solutions used are 
 N/50 hydrochloric acid, and barium hydroxide, approximately 
 N/100, its exact strength relative to the acid being found daily by 
 titration. It will be found advantageous- to use solutions of 
 this strength, somewhat more dilute than those recommended 
 by Walker, on account of the increased accuracy with air nearly 
 free from carbon dioxide. The decreased range of usefulness is 
 readily compensated by the employment of smaller samples of 
 the impure air. 
 
 The barium hydroxide is preserved with especial care. The 
 hard-glass bottle containing it, placed on a high shelf so that 
 the measuring apparatus can be rilled directly by gravity, is 
 heavily coated on the inside with barium carbonate. The bottle 
 is closed by a rubber stopper with two holes, one of which car- 
 ries the siphon tube dipping to the bottom of the bottle and 
 supplying the measuring burette, while the other carries a fairly 
 large glass T. (Fig. 3). 
 
 * /. Chem. Soc, 1900, 77, p. 11 10. 
 
 t Woodman, /. Am. Chem. Soc, 1903, 25, p. 150. 
 
AIR: ANALYTICAL METHODS 
 
 20 
 
 A 
 
 *; 
 
 From one-half the horizontal arm of this projects a glass tube 
 carrying the device for protecting the solution. This device is 
 shown drawn on a somewhat larger scale in the same sketch. 
 The horizontal tube enters the T tube 
 far enough to support the apparatus. 
 Connection is made by a closely-fitting 
 rubber tube. The longer tube, reach- 
 ing nearly to the bottom of the test- 
 tube, carries a fairly good-sized cal- 
 cium-chloride tube which contains T 
 soda-lime, enclosed in the usual man- 
 ner by plugs of cotton. The test-tube 
 contains five to 10 c.c. of dilute (about 
 N/50) caustic potash colored with phe- 
 nolphthalein, the whole serving to in- 
 dicate the efficiency of the soda-lime. 
 From the other end of the horizontal 
 arm of the T projects, in the same way, a long tube bent at 
 right angles fitting by a rubber stopper into the top of the 
 burette, thus making the whole a closed system, much after 
 the manner of Blochmann* Any air entering the bottle when 
 the solution is drawn from the burette or when the burette 
 is filled again must have come through the protecting appa- 
 ratus. This will be found efficient if care is taken in the selec- 
 tion or preparation of the soda-lime.f 
 
 The burette used for the barium hydroxide is a glass-stop- 
 pered one, differing somewhat from the ordinary form. The 
 portion below the graduations is narrowed and bent at a right 
 angle. This horizontal part is fitted with an ordinary glass 
 stop cock. This gives no trouble when kept well vaselined. 
 The tip of the burette is kept covered with a little rubber cap 
 when not in use, to prevent clogging from the formation of 
 carbonate. The apparatus could easily be arranged with a 
 
 Fig. 3. 
 
 * Ann. Chem., (Liebig), 1887, 2 37» P- 39- 
 
 t Directions for preparing a good quality of soda-lime are given by Benedict 
 and Tower, /. Am. Chem. Soc, 1899, 21, p. 396. 
 
So 
 
 AIR, WATER, AND FOOD 
 
 special pipette for the delivery of a definite charge of a baryta 
 solution. 
 
 The apparatus used for filtering off the barium .carbonate is 
 shown in Fig. 4. On the base of a ring stand is placed an ordi- 
 nary filter bottle of about 250 c.c. capacity closed by a rubber 
 stopper with one hole. The suction pump is connected with the 
 
 tube on the side of the bottle. A Gooch 
 filtering-funnel, the upper part of 
 which is cut off so that the remainder 
 above the constriction is about an 
 inch long, is put through the rubber 
 stopper. The tip projecting into the 
 bottle is bent so that the liquid shall 
 flow down the side and not spatter. 
 A rather close coil of stout platinum 
 wire placed above the narrow portion 
 serves as a support for an asbestos 
 filter. A two-cm. Gooch filter plate 
 serves as well as the platinum wire. 
 In the upper part of the tube is a 
 tightly-fitting rubber stopper, through 
 which passes a narrow glass tube 
 extending to within one-eighth inch 
 of the asbestos layer, and provided 
 above the stopper with a stop cock. 
 Connection is made with the short 
 FlG - 4- tube of the inverted bottle by means 
 
 of a rubber tube about 4 inches in length. 
 
 The inverted bottle is a carefully calibrated one of about 
 one liter capacity, and is used for collecting the sample, the 
 method preferably being by water displacement as described 
 on page 25. Record the temperature and barometric pressure 
 at the time the sample is taken. After collecting the sample the 
 bottle is closed by a solid rubber stopper. For filtering, this is 
 replaced by a rubber stopper through which pass two glass 
 tubes. The longer tube reaches nearly to the bottom of the 
 
AIR: ANALYTICAL METHODS 3 1 
 
 bottle, is bent as shown, and contains a glass stop cock. The 
 shorter tube ends internally just flush with the stopper, and out- 
 side is fitted with a stop cock and projects just far enough to 
 make connection with the rubber tubing. The glass stop cocks 
 may be replaced by rubber tubing and Mohr pinch clamps. 
 
 The filter is made of washed asbestos, free from acids, in the 
 manner usual for Gooch crucibles. The same filter will do for 
 a number of determinations. The asbestos layer should be 
 about one-eighth of an inch thick and should be washed with 
 distilled water. 
 
 Procedure. — Remove the stopper from the calibrated bottle 
 containing the sample of air, and run in rapidly from the burette 
 about 25 c.c. of the barium hydroxide solution, the exact amount 
 being determined from the burette readings. Immediately re- 
 place the rubber stopper, place the bottle on its side and shake 
 at very frequent intervals for 20 minutes, giving a sort of rotat- 
 ing motion so that the solution will spread over the bottle, and 
 thus expose a large surface for absorption of the carbon dioxide. 
 
 While the absorption is going on prepare the filter (although 
 it is better to prepare this, and to standardize the barium hydrox- 
 ide before starting the determination) and also make about 
 100 c.c. of wash water for each determination. This latter is 
 done by adding to distilled water one c.c. of a 10 per cent 
 barium chloride solution and three drops of phenolphthalein, 
 then titrating with the barium hydroxide to a faint permanent 
 pink. Keep in a stoppered flask until wanted. 
 
 Standardize the barium hydroxide against the hydrochloric 
 acid in the usual manner. Employ some wash water for 
 diluting in place of distilled water, which contains some carbon 
 dioxide. 
 
 Measure into the filter bottle from a burette about 13 c.c. (or 
 an amount slightly more than equivalent to the barium hydrox- 
 ide used) of N/50 hydrochloric acid, the exact amount being 
 obtained from the burette readings. 
 
 After the absorption is finished remove the rubber stopper 
 from the bottle, and wash the stopper with a little of the wash 
 
32 AIR, WATER, AND FOOD 
 
 water, letting the washings run into the bottle. Insert the two- 
 hole rubber stopper with connections for filtering and invert as 
 shown in the figure. 
 
 Open the upper stop cock and turn on the pump. Now slowly 
 open the filter stop cock and control the flow of liquid entirely 
 with this cock. The barium carbonate remains on the asbestos, 
 and the clear baryta solution which passes through is at once 
 neutralized by the hydrochloric acid. When all the liquid has 
 passed through allow the pump to act for a few minutes until 
 the bottle is partially exhausted, then close the filter cock. 
 
 Pour some of the wash water into a small beaker, dip the end 
 of the longer tube into it, and by opening the stop cock allow 
 about 20 c.c. to flow into the bottle before closing it. Un- 
 clamp the bottle and shake thoroughly while held horizontally 
 and still attached to the filter. Clamp it in place again, turn on 
 the pump, and draw the wash water through the filter. Repeat 
 this twice. Generally at the third washing the wash water no 
 longer turns pink, showing that the barium hydroxide has been 
 completely removed. If the pink color persists wash again. 
 
 Remove the filter bottle and titrate in the bottle, for the ex- 
 cess of acid, with barium hydroxide. The end point is a distinct 
 pink which is permanent for one minute. 
 
 To obtain the amount of carbon dioxide subtract the number 
 of cubic centimeters of N/50 acid used from the number of cubic 
 centimeters of acid equivalent to the barium hydroxide used. 
 This will give the amount of carbon dioxide in the sample in 
 terms of N/50 acid, from which the actual number of grams of 
 carbon dioxide can be obtained. From the table in the ap- 
 pendix * obtain the weight of one cubic centimeter of carbon 
 dioxide for the conditions of temperature and pressure observed 
 when the sample was taken. From this the volume of carbon 
 dioxide in the sample can be calculated, and knowing the vol- 
 ume of the bottle, and making allowance for the 25 c.c. of alkali 
 
 * 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. 
 
AIR: ANALYTICAL METHODS 33 
 
 added, the parts of carbon dioxide per 10,000 of air can be 
 calculated. 
 A sample calculation follows: 
 
 Standardization: — 1 c.c. Ba(OH) 2 = 0.48 c.c. N/50 HC1. . 
 Volume of bottle = 991 c.c. Temperature = 18 C. Ba- 
 rometer = 764 mm. 
 Total Ba(OH) 2 used 58.02. HC1 used = 26.08. 
 58.02 c.c. Ba(OH) 2 = 58.02 X 0.48 = 27.85 c.c. HC1. 
 '27.85 — 26.08 = 1.77 c.c. N/50 acid equivalent to the C0 2 
 
 present. 
 Since 1 c.c. N/50 acid = 0.44 mg. C0 2 , then there are 
 
 present in the sample 0.78 mg. C0 2 . 
 1 c.c. C0 2 at 18 and 764 mm. weighs 1.817 mg. .*. 991 — 
 25 = 966 c.c. of air contains .429 c.c. C0 2 or 4.4 pts. C0 2 
 per 10,000. 
 If the amount of carbon dioxide present exceeds 25 parts per 
 10,000, either a 500 c.c. bottle may be used for collecting the 
 samples, or double the quantities of barium hydroxide and hydro- 
 chloric acid should be added. Such a condition rarely exists 
 in practical work. 
 
 Pettenkof er Method. — The method which for many years 
 was generally employed for the estimation of carbon dioxide in 
 the air of rooms is a modification of that originally devised by 
 Pettenkofer.* While this method is convenient, and for a long 
 time has been the favorite, it is now quite generally recognized 
 that it contains inherent sources of error which can be obviated 
 only by the use of complicated apparatus and extreme skill in 
 manipulation. It should, therefore, be borne in mind that the 
 results obtained are generally too high even though agreeing 
 closely among themselves. 
 
 Principle. — The principle is essentially the same as that of 
 the Walker method, i.e., the absorption of carbon dioxide from 
 a known volume of air in barium hydroxide solution and the 
 titration of the excess with standard sulphuric acid. 
 
 * Pettenkofer, Annalen, 2, Supp. Band, 1862, p. 1; Gill, Analyst, 1892, 17, 
 p. 184. 
 
34 AIR, WATER, AND FOOD 
 
 The samples are collected in four- or six-liter bottles, as de- 
 scribed on page 24, each provided with a rubber stopper carry- 
 ing a glass tube over which a rubber nipple or cap is slipped. 
 Note particularly the temperature and barometric pressure. 
 
 Reagents and Apparatus. — The solutions used are sulphuric 
 acid of such a strength that one c.c. equals one milligram of 
 carbon dioxide (see appendix B), and barium hydroxide solu- 
 tion of approximately equal strength. Since it is impracticable 
 to prepare exact solutions of barium hydroxide, and to keep 
 them without change, the exact value of the barium hydroxide 
 solution must be found by titration against the standard sul- 
 phuric acid. 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 generally satisfactory to measure into the flask about 25 
 c.c. of the barium hydroxide, add a drop of phenolphthalein 
 solution, and titrate with the sulphuric acid to the disappear- 
 ance 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. 
 
 The apparatus consists of the collecting bottles, 50 c.c. bu- 
 rettes, a stoppered bottle of hard glass of 40 c.c. capacity, and 
 a 25 c.c. pipette. 
 
 Procedure. — Remove the cap from the tube in the stopper 
 of the bottle, insert the 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, place the bottle on its side and 
 roll or shake it at frequent intervals for 45 minutes, taking care 
 that the whole surface of the bottle is moistened with the solu- 
 tion each time. At the end of this time thoroughly shake the 
 bottle to mix the solution, remove the cap, and pour the solu- 
 tion 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 
 
AIR: ANALYTICAL METHODS 35 
 
 into a 75 c.c. flask and titrate it with the sulphuric acid as in 
 the standardization. 
 
 The calculation is similar to that given under the Walker 
 method except that it should be remembered that only one- 
 half of the barium hydroxide was used in the titration. 
 
 Rapid Methods. — In addition to the above methods for de- 
 termining carbon dioxide just described, there are general tests 
 which can often be used with advantage. If within the space 
 of a few hours some 50 or more tests are to be made, and com- 
 parative results rather than great accuracy are required, some 
 simpler form of apparatus is desirable. 
 
 Such an apparatus, to be satisfactory, should meet, so far as 
 possible, the following requirements: 
 
 (1) It should be sufficiently compact and portable to be car- 
 ried in the hand from place to place. 
 
 (2) It should be as simple in construction as possible, and its 
 use should not involve delicate measurements. 
 
 (3) If possible, the apparatus should be made entirely of glass, 
 avoiding prolonged contact of corks or of rubber connectors 
 with any dilute solution which may be used. 
 
 (4) It should be so constructed as to protect the solution at 
 all times from the carbon dioxide of the air, especially while the 
 determination is being made, because of necessity such an ap- 
 paratus must be used within the area of contamination. 
 
 (5) The complete apparatus should be sufficient for 50 or 
 more determinations. 
 
 (6) It must be capable of giving results of a reasonable de- 
 gree of accuracy, say within 0.5 part of carbon dioxide in 10,000 
 parts of air, in the hands of persons having little or no chemical 
 knowledge and minimum skill in manipulation. 
 
 (7) If a solution be used in the apparatus it should be one 
 which can be prepared easily from chemicals readily obtained; 
 the solution must maintain its efficiency for a reasonable length 
 of time, if protected from external influences; and the solution 
 should be one that is not at all dangerous or obnoxious to use. 
 
 Simplicity of apparatus is much to be desired, but it should 
 
36 
 
 AIR, WATER, AND FOOD 
 
 not be gained at too great sacrifice of accuracy. Even when no 
 greater precision is required than is necessary to meet the de- 
 mands of practical work, it is out of the question to measure the 
 test solution by means of an ordinary pipette or to preserve it 
 for any length of time in stoppered vials; the strength of the 
 solution is almost certain to be reduced by contamination with 
 the breath, or by contact with rubber or cork. 
 
 It must ever be borne in mind that extreme care is necessary 
 in the preparation and use of these very dilute solutions, the 
 strict observance of conditions which might well be neglected 
 in ordinary analytical procedures being here an essential factor 
 of success. 
 
 For the preservation and measuring of the test solution an 
 apparatus has been devised which appears to answer the above 
 requirements, and in actual practice has been found satisfactory.* 
 
 The essential feature of this 
 apparatus consists of an auto- 
 matic pipette for measuring 
 the test solution. This is a 
 modified form of the pipette 
 first proposed by G. P. Vanier 
 and in use in this laboratory 
 for a number of years. A 
 general idea of it may be had 
 from Fig. 5. The manner of 
 using it is extremely simple. 
 The test solution is preserved 
 in a one-liter bottle of hard 
 glass provided with a doubly 
 perforated rubber stopper. 
 Through one opening passes 
 the siphon tube of the pipette, which is sufficiently long to reach 
 to the bottom of the bottle; through the other passes a glass 
 tube ending just below the stopper and connected with a small 
 
 * "Air Testing for Engineers," A. G. Woodman and Ellen H. Richards, Tech. 
 Quar., 1901, 14, p. 94. 
 
AIR: ANALYTICAL METHODS 37 
 
 drying tube containing fresh soda-lime. By means of the three- 
 way cock the solution is allowed to flow into the small inside 
 pipette until it overflows. The stop cock is then turned, and 
 the solution allowed to flow out at the lowest point. The pipette 
 is made of such a size as to deliver exactly 10 c.c. The excess 
 of liquid which accumulates in the overflow reservoir may be 
 drawn off when desired. The bottle and pipette are contained 
 in a wooden case, about 20 by 8 by 7 inches, outside dimen- 
 sions, and with the solution, weigh about eight pounds. The 
 case is furnished with a handle at the top so that it may be 
 carried readily in the hand from place to place. The bottle 
 is fastened to the case, and the lower end of the pipette is 
 clamped to a wooden support to keep it from swinging. The 
 stopper should be firmly fastened to prevent loosening. 
 
 The bottle should be thoroughly cleaned and washed with 
 potassium bichromate and sulphuric acid, and it is best also to 
 steam it for half an hour or so. As a further measure of pre- 
 caution the rubber stopper is boiled with dilute caustic potash 
 and thoroughly washed, although the solution can come in con- 
 tact with it only through splashing while the case is being 
 carried. 
 
 This measuring apparatus may be used with a variety of 
 methods, and with various strengths of solution. 
 
 Cohen and Appleyard Method.* — Principle. — The method 
 of Cohen and Appleyard 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 re- 
 quired depending upon the amount of carbon dioxide present. 
 That is, the quantity of lime-water and the volume of air re- 
 maining the same in each case, the rate of decolorization will 
 vary inversely with the amount of carbon dioxide. 
 
 Reagents and Apparatus. — The solution used is a dilute so- 
 lution of lime-water colored with phenolphthalein. To freshly 
 
 * Chem. News, 1894, 70, p. in. 
 
38 AIR, WATER, AND FOOD 
 
 slaked lime add 20 times its weight of water in a bottle of such 
 size that it is not more than two-thirds full. Shake the mix- 
 ture continuously for 20 minutes, and then allow it to settle 
 over night or until perfectly clear. The resulting solution is the 
 stock lime solution, or " saturated lime-water." If made in the 
 manner indicated, each cubic centimeter of it ought to be very 
 nearly equivalent to one milligram of carbon dioxide. If, how- 
 ever, it is desired to know the strength of it more exactly, it 
 may be determined by standard acid. 
 
 To prepare the " test solution," pour into the one-liter bottle 
 of the testing apparatus one measured liter of distilled water, 
 and add 2.5 c.c. of a solution of phenolphthalein (made by dis- 
 solving 0.7 gram of phenolphthalein in 50 c.c. of alcohol and 
 adding an equal volume of water). Stand the bottle on a sheet 
 of white paper and add the " saturated lime-water " drop by 
 drop from a pipette, shaking the bottle thoroughly after each 
 addition until a- faint pink color is produced which is permanent 
 for one minute. Now add 6.3 c.c. of the " saturated lime-water," 
 shake, and immediately connect the bottle again to the apparatus. 
 
 For accuracy in air which is high in carbon dioxide, it is found 
 advantageous to use a solution which is twice as strong as the 
 above. This double solution is prepared in precisely the same 
 way, using 5.0 c.c. of the phenolphthalein solution and 12.6 c.c. 
 of the " saturated lime-water." 
 
 While this procedure does not give an exact volume of solu- 
 tion, it is believed to be the best for the preparation of this 
 dilute test solution, since it obviates the necessity for pouring 
 the prepared solution from the measuring flask into the bottle 
 in which it is kept; 12.6 c.c. of the stock lime solution is added 
 rather than 10 c.c, in order to keep the values obtained with 
 the resulting solution more nearly comparable with the older 
 values calculated on the supposition that 10 c.c. of the " satu- 
 rated lime-water " was equivalent to 12.6 mg. of carbon dioxide. 
 
 The apparatus used is that shown in Fig. 5. The samples are 
 collected in 500 c.c. bottles by either the water displacement or 
 steam vacuum method. 
 
AIR: ANALYTICAL METHOD 
 
 39 
 
 Procedure. — Remove the rubber stopper from the bottle con- 
 taining the sample of air; run in quickly by means of the auto- 
 matic pipette 10 c.c. of the standard test solution; note the 
 time; replace the stopper; shake continuously and vigorously 
 until the pink color disappears; and again note the time. The 
 disappearance of color can most easily be seen if the bottle is 
 held over a piece of white paper. From the time required for 
 the pink color to disappear, the amount of carbon dioxide may 
 be found from Table A. 
 
 TABLE A 
 
 Time, 
 minutes 
 
 and 
 seconds. 
 
 Standard 
 
 solution. 
 
 C0 2 in 
 
 10,000. 
 
 Double 
 
 solution. 
 C0 2 in 
 10,00c. 
 
 Time, 
 minutes 
 
 and 
 seconds. 
 
 Double 
 
 solution. 
 C0 2 in 
 10,000. 
 
 O.I5 
 O.30 
 
 0.45 
 I. OO 
 
 115 
 1.30 
 
 1-45 
 2.00 
 
 2.15 
 2.30 
 
 2-45 
 3.00 
 
 3-15 
 3-3o 
 3-45 
 4.00 
 
 4-i5 
 4-30 
 4-45 
 5.00 
 
 5-3o 
 
 12. I 
 9.9 
 8.4 
 7.2 
 
 6.3 
 55 
 
 4-9 
 
 4-4 
 4.0 
 3-8 
 3-7 
 3-6 
 
 
 5-45 
 6.00 
 
 6.15 
 6.30 
 
 6.45 
 7.00 
 
 7-i5 
 7 30 
 
 4.0 
 
 39 
 .„„.. 
 
 3-7 
 
 
 
 
 
 16 
 
 13 
 11 
 IO 
 
 9 
 8 
 
 7 
 7 
 6 
 6 
 5 
 5 
 5 
 4 
 4 
 4 
 4 
 4 
 4 
 
 
 
 1 
 
 4 
 
 1 • 
 1 
 
 3 
 6 
 
 
 5 
 
 1 
 
 7 
 4 
 
 1 
 
 9 
 
 7 
 5 
 3 
 2 
 
 1 
 
 Shaker Methods. — At least two forms of apparatus are on 
 the market for determining the percentage of carbon dioxide by 
 measuring the amount of air required to decolorize the stand- 
 ard solutions described on page 38. These are known as the 
 Fitz and the Wolpert Shakers (see Fig. 6) . The results obtained 
 are less accurate and more uncertain than by other methods, 
 but if great care is taken to keep the apparatus at some 
 
 
4° 
 
 AIR, WATER, AND FOOD 
 
 distance from the face of the worker, approximate results can 
 be obtained. As both shakers operate on the same principle 
 only the Fitz will be described. It consists of a tube of about 
 30 c.c. capacity, closed at one end, and graduated for a dis- 
 tance of 20 c.c. from the closed end. In this 
 tube, by means of a rubber collar, slides a smaller 
 tube which is contracted at the outer end so as 
 to be more readily closed by the ringer. 
 
 Procedure. — See that the inner tube of the 
 shaker slides readily in the outer one, moistening 
 the rubber collar slightly if necessary. Have 
 the inner tube pressed down to the bottom of 
 the larger one and measure into the apparatus 
 10 c.c. of the test solution from the automatic 
 pipette. Pull the inner tube up to the 5 c.c. 
 mark (the bottom of the inner tube serving as 
 the index) and close the end of the tube with 
 the finger. Hold the apparatus horizontally, 
 and shake it vigorously for exactly 30 seconds. 
 The amount of air that is thus brought in contact with the 
 solution is equivalent to approximately 30 c.c, as there are 
 25 c.c. of air above the liquid when the small tube is forced to 
 bottom of the larger. Remove the finger, press down the small 
 tube again to the bottom of the larger and draw it up to the 
 20 c.c. mark. Shake the apparatus again for 30 seconds. The 
 amount of air brought in contact with the solution is now 
 30 + 20 = 50 c.c. Repeat the shaking, using 20 c.c. of fresh 
 air each time, until the pink color is discharged. The amount 
 of carbon dioxide corresponding to the number of cubic centi- 
 meters of air used will be found in Table B. 
 
 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 considerable difficulty. 
 Detection. — Probably the most convenient test for detecting 
 small quantities is the blood test. Dilute a large drop of human 
 blood, freshly drawn by pricking the finger, to 10 c.c. with water. 
 
 Fig. 6. Fitz 
 Shaker 
 
AIR: ANALYTICAL METHODS 
 
 41 
 
 Divide the solution into two equal portions, and shake one 
 portion gently for 10 minutes in a bottle containing about 
 100 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 appear- 
 
 TABLE B 
 
 Cubic centimeters 
 of air. 
 
 50 
 
 70 
 
 90 
 
 IIO 
 
 130 
 
 I50 
 
 170 
 I90 
 2IO 
 230 
 250 
 270 
 290 
 3IO 
 330 
 3SO 
 370 
 390 
 4IO 
 4SO 
 49O 
 530 
 
 Standard test 
 
 solution. 
 C0 2 in 10,000. 
 
 Double 
 
 solution. 
 C0 2 in 10,000. 
 
 ance of a pink tint in the blood which has been shaken with air. 
 One part in 10,000 can be detected in this way.* The delicacy 
 of the test can be increased by examining the blood, after shak- 
 ing with air, with a spectroscope. By collecting the sample in a 
 eight-liter bottle and examining it in this way 0.01 part in 10,000 
 may be detected. 
 
 Determination. — Practically all the methods for the determi- 
 nation of carbon monoxide in small amounts depend on the 
 equation : 
 
 I2O5 + 5CO-+5CO2 + I2; 
 
 * Clowes, "Detection and Estimation of Inflammable Gas and Vapor in the 
 Air," p. 138. 
 
42 AIR, WATER, AND FOOD 
 
 then either the iodine * is titrated or the carbon dioxide deter- 
 mined. The method consists of passing the air through U-tubes 
 containing potassium hydroxide and sulphuric acid to remove 
 unsaturated hydrocarbons, hydrogen sulphide, etc., and then 
 through a U-tube containing iodine pentoxide, and heated to 
 150 C. The iodine liberated is absorbed in a solution of potas- 
 sium iodide, and may be titrated with N/1000 sodium thiosul- 
 phate, or the carbon dioxide passing through the potassium 
 iodide may be absorbed by barium hydroxide and determined.! 
 
 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 approxi- 
 mately N/50 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 24 hours. Take out 50 c.c. of the solution and 
 determine the amount of nitrites as directed in the determination 
 of nitrites in water. 
 
 Micro-organisms.f — The determination of bacteria in the 
 air is of importance only under special conditions which some- 
 times exist in dairies, factories, etc. In general the method used 
 is to filter a measured amount of air through sand, shake out 
 the bacteria with sterile water, and plate aliquot portions. 
 Counts are made after 5 days' incubation at 20 C. 
 
 * Kinnicutt and Sanford, /. Am. Chem. Soc, 1900, 22, p. 14. 
 Morgan and McWhorter, /. Am. Chem. Soc, 1907, 29, p. 1589. 
 Seidell, J. Ind. Eng. Chem., 1914, 6, p. 321. 
 Gautier, J. Gas Lighting, 121, p. 547. 
 f For details of the methods reference should be made to the above articles. 
 Recently a portable apparatus has been described by Goutal, Analyst, 1910, 35, 
 p. 130. 
 
 t See "Standard Methods for the Bacterial Examination of Air," Am. J. Pub. 
 Health, 1910, 6, No. 3, or reprint by the Am. Pub. Health Assn. 
 
CHAPTER IV 
 
 water: its relation to health, its sources and properties 
 
 Two-thirds of the animal organism consists of water; this 
 water is necessary * for practically all physiological processes, 
 either taking part in the reaction or acting as a solvent. It aids 
 in carrying nourishment to all parts of the body and in disposing 
 of the waste products formed. The evaporation of water from 
 the surface of the body serves as the most important method 
 of regulating the body temperature. Since water is lost by 
 these means as well as during respiration, it is evident that the 
 animal organism must be supplied with water from outside 
 sources. The daily amount needed for each person is five or 
 six pints. 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. 
 
 Water is also required for many other purposes, such as cook- 
 ing, washing, generation of power, and other manufacturing 
 uses. It has been estimated that 25 gallons per'person per day 
 is sufficient for household purposes. Then some must be al- 
 lowed for public use and a rather large amount for manufactur- 
 ing. For cities in this country amounts varying from 50 to 
 200 gallons are used, with an average of close to 100 gallons. 
 This is about three times as much as is used in European cities, 
 and undoubtedly a large amount represents unnecessary waste. 
 That this is true is shown by the fact that when the individuals 
 in a community are required to pay for the actual amount of 
 water consumed, which is done through the introduction of 
 meters, the consumption falls off to one-half or one-third of the 
 former quantity used. Waste of water represents a very serious 
 problem in large cities, where it is often necessary to go long 
 
 * See " Text-book of Physiological Chemistry," Abderhalden-Hall, John Wiley 
 & Sons, 1908, p. 354. 
 
 43 
 
44 AIR, WATER, AND FOOD 
 
 distances at great expense, to obtain a sufficiently large supply 
 suitable for drinking purposes. 
 
 The problem is made still more difficult by the use of large 
 bodies of water, both lakes and rivers, for the purposes of waste 
 disposal. Recent reports of experts * have raised the question 
 as to how much of the expense of purifying a sewage should be 
 borne by the community emptying its waste into a stream, and 
 how much should be borne by a community farther down the 
 stream where water is removed for domestic use. The only 
 certain condition which should be demanded is that wastes 
 should be in such a state and so diluted that no nuisance will 
 be created along the banks of the stream. It seems as if the 
 question of further purification would have to be decided for 
 each individual case as it arises. 
 
 That there is a close relation between drinking water and 
 disease has long been suspected, but it is only since the develop- 
 ment of the present ideas of the cause of disease that this 
 relationship has been satisfactorily demonstrated. Drinking 
 water may act as the carrier of the germs of at least two well 
 defined diseases, — Asiatic cholera and typhoid fever, — and 
 probably of those of other intestinal troubles. There is, be- 
 sides, some tendency to disturb the system when a change is 
 made from one kind of drinking water to another of radically 
 different composition, such, for example, as a change from a 
 hard Middle West water to a soft New England water. The 
 disturbance is generally only temporary, as the system becomes 
 rapidly accustomed to new conditions. 
 
 The first cholera epidemic to be traced definitely to drinking 
 water was that in London in 1854, which centered about the 
 Broad Street Pump, and the investigation of which was thor- 
 oughly carried out by an efficient health officer. Since then 
 numerous epidemics have been traced to the use of polluted 
 water, notably that of Hamburg in 1892-3.! 
 
 * See, for example, Eng. Rec, 191 2, 65, p. 209. 
 
 t For a description of epidemics of both cholera and typhoid fever see Sedg- 
 wick's "Sanitary Science and Public Health." 
 
WATER 45 
 
 In this country we have little to fear from cholera on account 
 of the efficient work of the Public Health Service at our ports, 
 but typhoid fever is still a scourge and a disgrace. As early as 
 1850 it was maintained by Budd in England that this fever was 
 spread by drinking water, but no sufficient evidence was pro- 
 duced until the Lausen, Switzerland, epidemic of 1872. The 
 first large epidemic in this country to be traced to water was that 
 of Plymouth, Pa., in 1885, in which about 1000 cases resulted 
 from the negligence of an attendant on one typhoid patient. 
 Since that time numerous small and large epidemics have been 
 traced with more or less certainty to the use of polluted water. 
 
 That the introduction of a good water supply in place of a 
 bad one results in a marked decrease in typhoid fever can be 
 readily seen by almost endless lists of statistics of cities and 
 towns which have either obtained a new supply or have intro- 
 duced niters, the deaths from typhoid being from one-half to 
 one-rlfth of the number formerly recorded in such places.* 
 
 Xot only does the introduction of unpolluted water mean a 
 decrease in typhoid fever, but there seems also to be a general 
 increase in the health of the community. This effect was 
 noticed at about the same time by Mills in this country and 
 Reincke in Germany, and is known as the Mills-Reincke phe- 
 nomenon. Hazen attempted to formulate a mathematical re- 
 lationship between the decrease in typhoid fever and that in all 
 other diseases, but the result is merely an approximation. This 
 increase in the general health may be due to increased vitality 
 by the elimination of one disease. It has been recently sug- 
 gested that since tuberculosis is liable to follow typhoid fever, 
 a decrease in the latter would account for a decrease in the 
 former. 
 
 Safe water, is, therefore, one of the necessary requirements of 
 any community, large or small. 
 
 Rain Water. — Let us trace the cycle through which water 
 passes, and point out the sources of supply, and the methods of 
 contamination. Water vapor rising from the sea and land con- 
 
 * See Am. J. Pub. Health, 1913, 3, p. 1327. 
 
46 AIR, WATER, AND FOOD 
 
 denses and falls to the earth as rain. As it does so, ammonia, 
 carbon dioxide, and other soluble gases are absorbed, and dust 
 and living organisms are collected. As soon as these sub- 
 stances are removed from the air, the rain water becomes a 
 very pure source of supply, and can be used for drinking pur- 
 poses if properly stored. There are several factors to be ob- 
 served in this. First, there should be no connection whatever 
 between the storage tank and any drain or sewer from a house 
 or barn. More than one case of typhoid fever has resulted 
 from the backing up of sewage through an overflow pipe into a 
 rain water tank. Second, no metal or other material which 
 is injurious to health should be used in building such a tank, 
 as rain water is soft and often slightly acid and, therefore, 
 has considerable solvent power for most metals. The best ma- 
 terials to use are cement, slate, or stoneware; lead should be 
 absolutely avoided, and zinc will not last any length of time. 
 Third, there should be some method of wasting the first rain 
 that falls, in order not to load the storage tank with dirt and 
 other material which may come from a roof or collecting shed, 
 and render the water unpalatable. Fourth, there should be 
 some easy means of cleaning the tank, and this should be done 
 at frequent intervals. Rain water is used for drinking practi- 
 cally only in tropical regions. 
 
 Surface Waters. — Approximately one-third of the rain evapo- 
 rates again from the surface where it falls; another third runs 
 off on the surface, forming streams, rivers, and lakes, finally 
 reaching the ocean; the other third sinks into the ground, per- 
 haps joining the surface waters underground, coming out as 
 springs or flowing wells, or remaining in the soil. The average 
 rainfall for the whole United States is about 36 inches, varying 
 in different parts of the country from almost nothing to 60 
 inches. Thus we find the amount of water with which we have 
 to deal is very variable, depending on the locality and the 
 season. Approximately one-half of the rainfall finds its way 
 finally into rivers, either running off on the surface, or entering 
 from underground. 
 
WATER 47 
 
 Surface waters form an exceedingly important source of 
 supplies, as most large cities find them necessary on account 
 of the large quantities of water required. Water from small 
 streams and brooks on a water shed may be collected and stored 
 in reservoirs. This method is considerably used, particularly in 
 hilly regions, and if proper care is taken to prevent any pollution 
 on the watershed, sufficient supplies of excellent quality may be 
 obtained. The reservoirs are generally uncovered, and should 
 be stripped of all plant life. Surface water, if unpolluted, 
 usually improves on storage. 
 
 Where it is not possible to obtain a supply in this manner, 
 large rivers or lakes are used. These are nearly all subject to 
 more or less pollution, and in general the water should not 
 be used unless filtered or sterilized. Some self-purification will 
 take place in such bodies of water.* The most important 
 factor in such purification is the removal of bacteria by means 
 of sedimentation, the larger particles in the water carrying 
 bacteria with them to the bottom of the stream where the patho- 
 genic varieties soon die out. Thus in a slow moving stream 
 harmful organisms are removed more quickly than in a rapidly 
 moving river. Another important factor is the exhaustion of 
 the food supply. Also, conditions of temperature are not favor- 
 able for the growth of many bacteria, and it is undoubtedly 
 true that even in a highly polluted water there is little multi- 
 plication, and much dying off of disease organisms. 
 
 On the other hand, it is not safe to rely on self-purification, 
 particularly when the health of a large number of people is at 
 stake. There are too many possibilities of accidental pollution. 
 Some artificial means must be used. These will be mentioned 
 later. 
 
 Odors sometimes develop in stored water as a result of growth 
 of various plants and animals.f Some of these odors are ex- 
 
 * See Jordan, "Natural-purification of Streams." Paper presented at the 26th 
 annual convention of the American Water Works Assn. 
 
 t See Whipple, "The Microscopy of Drinking Water," John Wiley & Sons, 
 1914. 
 
48 AIR, WATER, AND FOOD 
 
 ceedingly disagreeable and may render a water supply unfit to 
 deliver. The growths can generally be exterminated by the 
 proper use of copper sulphate in quantities which will kill the 
 small organisms but are not injurious to the human system (one 
 part to from one to 20 million parts of water). 
 
 Surface waters often have color, produced usually by solu- 
 tion, in colloidal form, of partly decomposed vegetable matter, 
 which is perfectly harmless, and such waters should not be con- 
 demned unless sewage is also present. They are, however, often 
 decolorized, before delivery, by means of alum. Surface waters 
 are generally softer than ground waters, have a slight, but not 
 disagreeable odor, may be more or less turbid, and in the sum- 
 mer time are liable to be warmer than is desirable. On the 
 whole, however, there is no more satisfactory supply for a large 
 city than a good surface water. 
 
 Ground Waters. — From 25 to 40 per cent of the annual rain- 
 fall in temperate regions soaks at once into the ground, and 
 passing downward through the soil to hardpan, 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 springs. 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 disappeared to great depths. It has been esti- 
 mated that water moves in the ground at rates varying from 
 0.2 to 20 feet per day. This movement is in the form of a sheet, 
 and its rapidity as well as the amount of water held in the 
 ground will depend on the geological formation. Thus a clay 
 will hold more water than loam or sand, while the permeability 
 is just the reverse, clay being nearly impermeable. Water also 
 passes through channels in rocks, either made by the water it- 
 self or consisting of cracks and fissures. These latter are often 
 
WATER 49 
 
 a source of danger, as no purification can take place if a pol- 
 luted water travels in this manner. 
 
 This long contact with rocks will, of course, bring mineral 
 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 solution. It is 
 no wonder that so active a solvent as water should take with it 
 much substance whenever it remains long in contact with soil 
 or rock, for it may be 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 surface. Then, too, the acquisi- 
 tion of dissolved gases favors the solution of many substances; 
 for instance, water carrying carbon dioxide dissolves limestone. 
 
 From a chemical standpoint ground waters may be divided 
 into two classes, — (i) springs and shallow wells (those 30 feet 
 or less in depth) and (2) deep and artesian wells. In general 
 springs and shallow wells yield softer water than deep wells of 
 the same region, but they are much more subject to pollution 
 than the latter, which, if built so as to exclude any surface 
 water, are usually a safe source of supply. Pollution does 
 sometimes enter a deep well, due to the passage of water 
 through fissures and crevices in the rocks. 
 
 The greatest source of danger is the shallow well. This should 
 never be used in a thickly populated region, and in country 
 districts only when it can be placed in such a position that there 
 can be no connection through the ground with a privy or cess- 
 pool. A well should be built in such a manner that no surface 
 water can enter it, and the walls should be tight to a depth of 
 five to 10 feet below the surface in order that any water which 
 sinks into the ground may be sufficiently filtered before enter- 
 ing the well. The area from which a well may draw varies 
 with the permeability of the soil, and may have a diameter of 
 20 or more times the depth of the well. The ground which is 
 influenced by a well is in the form of an inverted cone whose 
 apex is at the bottom of the well. 
 
50 AIR, WATER, AND FOOD 
 
 If a well is found upon examination to be polluted with sew- 
 age it is often desirable to find the source of trouble in order 
 to stop further pollution. There are several methods of doing 
 this.* A survey of the ground and the conditions surrounding 
 the well is often sufficient to indicate the probable sources, but 
 more definite evidence may be required. Some substance is 
 then added to the suspected source, washed into the ground 
 with a large amount of water, and the well examined for the ap- 
 pearance of the substance. For this purpose bacteria, such as 
 B. prodigiosus and B. violaceous, can be used. These organisms 
 are easily grown, are harmless and can readily be identified. 
 If these do not reach the well from the suspected source of 
 pollution it is fair to assume that no pathogenic organisms 
 will do so, but will be filtered out in passing through the 
 ground. The only uncertainty with this method is that while 
 the bacteria may be sufficiently removed at the time of the test, 
 the filter may sometime break down and allow sewage organ- 
 isms, and possibly disease germs, to enter the well. It is, there- 
 fore, better not to use a well water which receives sewage from 
 any nearby source, even though bacteria are being eliminated 
 in passing through the ground. 
 
 Other methods of tracing the source of pollution are by the 
 use of common salt, easily tested in the well water by an analysis 
 for chloride; lithium or strontium salts, recognized even in 
 minute amounts by means of the spectroscope; and fluorescent 
 dyes such as fluorescein, which are readily observed in a glass 
 of water. 
 
 One method of obtaining ground water in comparatively 
 large quantities is by means of the so-called " filter gallery." 
 This consists of a series of wells dug near the banks of a river. 
 It was originally thought that a suction would be created so as 
 to draw water from the river into the wells through a layer of 
 soil sufficient to remove harmful bacteria. As a matter of fact, 
 the filter gallery actually operates by intercepting ground water 
 
 * See Thresh, "Examination of Waters and Water Supplies," 2nd edition, pp. 
 25-34. 
 
WATER 51 
 
 on its way to the river, really a better method than had been 
 intended. In sparsely populated regions where the ground 
 water is unpolluted, good results have been and are being ob- 
 tained by the filter-gallery, but when a region becomes thickly 
 settled considerable danger results. Furthermore, in times of 
 drought water may be drawn from the river bed, and if this 
 reaches the gallery improperly filtered, a typhoid epidemic 
 may result.* 
 
 In general, good ground waters contain more mineral matter 
 than surface waters, have no color or odor, can be delivered at 
 a lower temperature, and are often more palatable than surface 
 waters. It is, however, more difficult to obtain large supplies 
 from the ground, and, therefore, only comparatively small com- 
 munities can avail themselves of such sources. 
 
 Water Purification. — Water in passing through the ground 
 may undergo a number of changes in its dissolved and suspended 
 constituents. If this water contains sewage it will carry, with 
 other suspended matter, a large number of bacteria, some of 
 which may be of pathogenic varieties. If the polluted water 
 passes through not too coarse soil, the bacteria will be held by 
 the soil, and thus dangerous disease germs will probably be re- 
 moved. Even if all the sewage bacteria are not removed there 
 will still be some protection against disease, because disease 
 organisms have, in general, less vitality to withstand unfavor- 
 able conditions as well as being present in smaller numbers than 
 less harmful varieties. However, there is still some chance of 
 these bacteria being present at times, and it is, therefore, not 
 advisable to use water in which sewage organisms are present. 
 
 In streams, as has already been noted, pathogenic bacteria 
 gradually settle to the bottom and die out. 
 
 Thus there is some natural protection against the spread of 
 disease by means of drinking water, but it is not safe to depend 
 on such protection, particularly where the health of a com- 
 munity of people is involved. If a water supply which is sub- 
 
 * See "Typhoid Fever in Des Moines, Iowa," /. Am. Med. Assn., 1911, 56, 
 p. 41. 
 
52 AIR, WATER, AND FOOD 
 
 ject to either continuous or intermittent pollution has to be 
 used, some method of artificial purification is required before it 
 can be safely used for drinking purposes.* 
 
 There are two general methods of filtering water on a large 
 scale. The first is known as slow sand filtration. In this 
 method the water is run through a layer of sand from two to 
 four feet thick, supported by gravel and properly underdrained. 
 The filter beds are generally built in units of one acre each, and 
 may be covered or not depending on the climatic conditions. 
 Previous to filtration the water may be screened and stored in 
 reservoirs to allow some removal of suspended matter, includ- 
 ing bacteria. As the water passes through the sand a layer of 
 slimy material gradually collects on the surface, which acts as 
 the real straining medium and holds the bacteria. As this 
 material collects the rate of filtration decreases until a point is 
 reached where it is uneconomical to continue. The water is 
 then allowed to drain out from the sand, the top layer scraped 
 off, and the filter again started. The sand removed is washed 
 and returned to the filter about once a year. A slow sand filter 
 operates at rates of from one and a half to three million gallons 
 per acre per day, and is probably the most efficient method of 
 removing bacteria on a large scale. It does not, however, com- 
 pletely remove color or odor. 
 
 The other method is that known as rapid filtration (also, un- 
 fortunately, termed mechanical filtration). Instead of allowing 
 the filtering layer to form from the matter in the water as in 
 slow sand filtration, a coagulant, generally alum, is added to 
 the water. The alkali, originally present, or added, precipi- 
 tates aluminum hydroxide which coagulates the suspended par- 
 ticles and removes the color. Part of the hydroxide is allowed 
 to settle out and the remainder is put on a filter built of sand, 
 where it collects on the surface and forms the filtering medium. 
 The filters are washed about every eight hours by reversing the 
 flow of water and agitating the sand by means of rakes or com- 
 pressed air. Filtration takes place much more rapidly by this 
 
 * See Hazen, "The Filtration of Public Water Supplies." 
 
WATER 53 
 
 method, being at rates from ioo to 150 million gallons per acre 
 per day. If there is insufficient alkali present naturally in the 
 water enough must be added, usually either as sodium carbon- 
 ate or as calcium carbonate, to completely precipitate the alum 
 and leave some alkali in excess. Alum, being acid, if allowed 
 to remain in the water renders it corrosive. The amounts of 
 alum used vary from one-tenth to three grains per gallon of 
 water. 
 
 Rapid filtration does not give quite as high a bacterial removal 
 as slow filtration, but it is much more efficient in removing 
 turbidity and particularly color. It requires a smaller invest- 
 ment and occupies less ground for the same amount of water 
 filtered. With either method expert control is necessary in 
 order to obtain satisfactory results. 
 
 A number of filters on the same principle as just described, 
 but built in small units, are on the market, intended to supply 
 hotels, manufacturing establishments, swimming pools, etc. 
 Many of them give reasonably good results when properly 
 operated, but they never should be considered to be automatic 
 in character. They all need careful attention. 
 
 Filters still smaller are sold for office and household uses. 
 These generally consist of artificial stone or porcelain through 
 which the water is forced, such as the Pasteur-Chamberlain or 
 the Berkefeld filter. If the stone, or candle as it is called, is in 
 good condition, sterile water may be drawn when the filter is 
 first put into use, but the bacteria lodging in the stone grad- 
 ually develop and may grow through the filter so that as water 
 passes through it will wash bacteria with it. It must be ad- 
 mitted that the chances are that pathogenic organisms will not 
 get through. If, however, there is a crack in the candle, often 
 too small a one to be visible, the filter will allow all kinds of 
 bacteria to pass. One of the great objections to the use of such 
 filters is the false feeling of safety which they may inspire in 
 the owners. The all too common small " filter" which screws 
 on the faucet is not only useless, but worse. 
 
 If unsafe drinking water must be used in a house, the only 
 
54 AIR, WATER, AND FOOD 
 
 sure method is to bring the water to a boil. This is sufficient to 
 kill any harmful intestinal organisms. Small stills which can 
 be placed on the back of the stove are of service in this con- 
 nection. The flat taste of boiled water may be removed by the 
 addition of a pinch of salt or by aeration. 
 
 Sterilization of Water. — Where a badly polluted supply is 
 used, or extreme caution is desirable, or where a good supply 
 suddenly becomes polluted and emergency measures deemed 
 wise, disinfection may be resorted to. The most practical 
 method is by the use of compounds of chlorine, — hypochlorite 
 of lime (chloride of lime or bleaching powder), sodium hypo- 
 chlorite (electrolytic bleach), or chlorine gas itself. Of these 
 the cheapest under ordinary conditions is chloride of lime. 
 This has the disadvantage of being disagreable to handle, and 
 of not dissolving completely in water. Amounts of from -^ to 
 t 3 q grains per gallon are generally sufficient. Sodium hypo- 
 chlorite can be used where there is cheap electricity, as it is 
 made by passing a current through a solution of common salt. 
 The use of chlorine gas is a recent development and appears to 
 be giving satisfactory results, although considerably more ex- 
 pensive than the other methods. 
 
 None of these substances, in the quantities used, are in any 
 way harmful. Where large doses are given complaints are 
 sometimes received that they can be tasted in the water, but, 
 even if true, this is not a necessary consequence of their use. 
 The disinfecting action is probably due to the chlorine itself. 
 
 Electrical methods of sterilization are also in somewhat 
 limited use. One of these is through the formation of ozone by 
 an electrical discharge through air, and treatment of the water 
 with the ozonized air. Ozone, in the presence of water, is a 
 reasonably good disinfectant, but its cost makes it prohibitive in 
 most places, and its application to the water presents some 
 engineering difficulty. The largest plant working is probably 
 that at St. Petersburg.* 
 
 A more recent development than ozone is the use of ultra- 
 
 * See Tillmans-Taylor, "Water Purification and Sewage Disposal." 
 
WATER 55 
 
 violet light, as obtained by the quartz-mercury- vapor lamp. 
 Ultraviolet light is a good disinfectant, but it is expensive to 
 produce in most places, and there are difficulties in applying it 
 to waters of all characters. The rays will not penetrate a turbid 
 or colored water to any extent, and, therefore, preliminary filtra- 
 tion and decolorization is often necessary. This, of course, adds 
 greatly to the expense. The method may, however, find use in 
 the future, if it is possible to produce it for a reasonable amount. 
 Ice. — Questions are often asked concerning the use of ice 
 in drinking water. In general, natural ice, particularly when 
 stored from four to eight months, is comparatively safe. In 
 freezing, suspended and dissolved matter is not removed from 
 the water with the ice, except a small amount mechanically 
 enclosed. Furthermore, it has been shown that over 90 per 
 cent of sewage bacteria die out on storage. Artificial ice, if 
 made from polluted water, is not safe, as in the method used all 
 suspended matter is frozen into the center of the cake. If the 
 artificial ice is made from unpolluted or from distilled water 
 as it should be, it is, of course, perfectly safe to use for all 
 purposes. 
 
CHAPTER V 
 
 SAFE WATER AND THE INTERPRETATION OF ANALYSES 
 
 Pure water, such as may be found in the laboratory, is neither 
 necessary nor probably desirable for drinking. There are, how- 
 ever, certain requirements which should be borne in mind in 
 looking for a supply. First, the water should be free from sew- 
 age and all other waste products. Second, it should not con- 
 tain an excessive amount of mineral matter. Third, it should 
 be free from color, odor, taste and suspended matter, and 
 should be delivered at a temperature not over 15 C. It is 
 obvious that all of these requirements cannot always be lived 
 up to, but it is essential that the first one should be, even at the 
 expense of the other two. A water free from sewage and other 
 waste products can be called a "safe" water. Unfortunately, 
 physical appearance is taken as the criterion of the safety of a 
 supply by too many people. The cool, clear, colorless water is 
 much to be preferred to the safe colored or muddy one; and it 
 is sometimes difficult to persuade the user of such a supply as 
 the former that he may be endangering his health by drink- 
 ing it when tests have shown the presence of sewage. Since 
 appearance is of such importance, it is necessary to take this 
 into account in any water examination. 
 
 Since, as already described, a water once in contact with 
 sewage may become purified and be rendered safe for drinking 
 purposes, and since water is so universally made a carrier of 
 refuse that it is difficult to find a stream or well which has never 
 been at any time in contact with waste, certain arbitrary stand- 
 ards have been chosen to determine when a water may be called 
 safe, on the basis of an analysis. Such limits are very mislead- 
 ing of themselves, especially if used over a wide extent of ter- 
 ritory. The English standards, for instance, are not applicable 
 
 *6 
 
SAFE WATER 57 
 
 to eastern North America. Only a study of all local conditions 
 and a wise interpretation of all results can make standard 
 figures of any significance. This is true, also, of bacterial re- 
 sults in surface waters. In lakes and streams there are so 
 many varieties of bacteria present and in such varying numbers, 
 according to wind and rain and water-shed, 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 cul- 
 ture-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 substances readily de- 
 tected by suitable chemical examination. 
 
 Sanitary Examination. — The examination of a water to de- 
 termine its safety for domestic use is called a sanitary analysis, 
 in distinction from that examination which determines its fit- 
 ness for manufacturing purposes, for use in steam boilers, or its 
 medicinal value. Such an examination may be either bacterio- 
 logical or chemical in character, but the object in either case is 
 the same, that is, to determine the absence of sewage or its 
 presence in quantities sufficient to render the water dangerous 
 to drink. In neither kind of examination are the harmful sub- 
 stances themselves sought for. Typhoid organisms have been 
 isolated from water during epidemics in only a few cases and 
 the process is a long and tedious one. Furthermore, such a 
 search would often be useless for an infected person does not 
 usually come down with the disease until 10 to 14 days after 
 infection, and the organisms might have died during this time. 
 Also, one does not care to wait until an epidemic starts before 
 examining the water supply, but desires to know in advance 
 whether or not there is any possibility of trouble. The presence 
 or absence of sewage determines this possibility. 
 
 In a bacteriological examination, the presence of sewage is 
 determined first, by counting the total number of bacteria per 
 cubic centimeter, and second, by looking for some type of dis- 
 
58 AIR, WATER, AND FOOD 
 
 tinctly sewage organism, such as B. coli. The total count has 
 little significance in a surface water, but in a well or filtered 
 water, should not be over ioo bacteria per cubic centimeter. 
 B. coli should not be present in numbers of one or more per 
 cubic centimeter. Considerable discussion surrounds the de- 
 termination of this organism, but it is quite impossible to see 
 what difference it makes whether the bacteria isolated show all 
 the typical reactions of B. coli communis or not. The members 
 of the colon group get into a water supply practically only with 
 sewage, and it should not make any difference in the interpre- 
 tation of results, as to what particular member of that group is 
 found. For the methods of making these determinations the 
 reader is referred to some book on bacteriology.* 
 
 Before proceeding with the laboratory test of a water, it is 
 essential to know something of the surroundings of the source 
 of supply. So long as the eye can re-enforce the other tests and 
 the whole course of the water may be clearly traced, it is com- 
 paratively easy to judge of the character 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 difficult. 
 
 The geological horizon and superficial soil must be 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. 
 
 An examination of the environment is often sufficient to con- 
 demn a water, but cannot usually give it a clear certificate. 
 Laboratory tests should follow. In the next paragraphs will 
 be found a discussion of the interpretation of sanitary chemical 
 analyses. 
 
 Expression of Results. — Results of a sanitary chemical 
 analysis should be expressed in parts of any particular substance 
 
 * Prescott and Winslow, " Elements of Water Bacteriology." John Wiley & 
 Sons, New York, 1913. 
 
SAFE WATER 59 
 
 per million of water. In most cases this is equivalent to milli- 
 grams per liter — the exceptions being where the water has an 
 appreciable specific gravity above i.o, such as sea water. 
 
 Accuracy of Methods. — In all water analyses very minute 
 quantities are sought after, and, therefore, all the tests applied 
 must be exceedingly delicate in character. The quantitative 
 results need not, however, be of great percentage accuracy. 
 For example, it makes no particular difference whether 0.050 
 or 0.055 parts of ammonia per million of water are found — an 
 error of 10 per cent. It might make a good deal of difference 
 if one found 0.2 of a part or 0.05 — a difference of 0.15 parts 
 per million, an amount which in most analytical work would be 
 entirely negligible. The American Public Health Association 
 has suggested that only a limited number of figures be used in 
 reporting an analysis, and thereby ehminate any impression of 
 false accuracy. 
 
 Above 10 parts per million. Use no decimals. 
 
 From 1 to 10 parts per million. Use 1 decimal. 
 From 0.1 to 1 part per million. Use 2 decimals. 
 
 In the determinations of ammonia and of nitrites 3 decimals 
 may be used. 
 
 The above discussion does not mean that the analyses should 
 be made in a careless or slipshod manner, in fact, quite the re- 
 verse is true, for there is no kind of chemical work which requires 
 greater care or cleanliness. 
 
 As little time as possible should elapse between the collection 
 and examination of samples of water. The more polluted the 
 water the more rapidly will changes take place, and, therefore, 
 all samples should be tested within 24 hours of their collection. 
 Samples for bacterial analysis should be examined immediately, 
 or if sent to a laboratory, should be packed in ice. Sewages and 
 sewage effluents should be analysed within six hours of collec- 
 tion, or if for chemical analysis should be chloroformed (5 c.c. 
 per liter) to prevent chemical changes taking place. 
 
 Chemical Examinations. — The chemical analyses generally 
 made in sanitary work are the following: nitrogen as free am- 
 
60 AIR, WATER, AND FOOD 
 
 monia, as albuminoid ammonia, as nitrates, and as nitrites; 
 chlorides in terms of chlorine; oxygen consumed; soap hard- 
 ness; total solids and loss on ignition; iron; and sometimes 
 oxygen dissolved. The interpretation of the results of each of 
 these will be discussed, and where possible, standard figures will 
 be given. 
 
 Nitrogen Cycle. — The most important determinations which 
 must be made in order to decide on the potability of the water 
 in question are those involving the nitrogen compounds and 
 chlorides. A clear understanding of the cycle of nitrogen in 
 nature is, therefore, necessary. 
 
 Nitrogen is present in living plants and animals mainly in 
 the form of organic compounds — the proteins and simpler 
 amino compounds. These substances, if boiled with alkaline 
 potassium permanganate, will give off part of the nitrogen in 
 the form of ammonia which can be collected and determined 
 quantitatively. This is called " albuminoid ammonia." When 
 the living plant or animal dies, the proteins are attacked by 
 bacteria and putrefy. In this process the nitrogen is converted 
 first into simpler amino bodies and finally into ammonium salts 
 or substances, such as urea, which readily yield ammonia. Thus, 
 the determinations of ammonia (called "free" ammonia) and 
 of albuminoid ammonia will indicate how far this putrefaction 
 has gone. A waste product, such as sewage, will give, when 
 fresh, both free and albuminoid ammonia in quantity, but on 
 standing, some of the organic nitrogen will change to ammonia, 
 so that the free ammonia will increase and the albuminoid am- 
 monia decrease. Thus, these analyses may be used to indicate 
 fresh or recent sewage pollution of a water supply. 
 
 When the organic nitrogen is largely converted to ammonium 
 compounds, and if oxygen is present, another kind of bacteria, 
 called the nitrosomonas, will act on the latter substances and 
 oxidize them to nitrites. This is the second stage in the nitrogen 
 cycle. Thus, the presence of nitrites in a water may indicate 
 less recent pollution than the presence of only free ammonia. 
 
 The nitrites, however, are not stable, and if sufficient oxygen 
 
SAFE WATER 6 1 
 
 is available, they are oxidized by still another set of micro- 
 organisms, the nitrobacter, giving nitrates. The nitrifying bac- 
 teria remained undiscovered for some time, owing to the fact 
 that they do not grow in the laboratory on any medium con- 
 taining large amounts of organic matter. Thus, the presence of 
 nitrates in a drinking water may indicate contact with sewage 
 at some past time, or as it is called, past pollution. 
 
 Nitrates are food for green plants, which in turn die or are 
 eaten by animals, the nitrogen being changed from the inor- 
 ganic back to the organic form, and the cycle thus completed. 
 
 But the cycle is not so simple as would appear. Nitrogen 
 may be lost from it in two ways. While ammonia is being oxi- 
 dized to nitrites, both may be present and interaction may 
 result with the formation of nitrogen gas. 
 
 NH 3 + HN0 2 -> N 2 + 2 H 2 0. 
 
 Or, nitrites may be reduced by micro-organisms with the liber- 
 ation of nitrogen. Nitrates may also be reduced to nitrites by 
 bacteria, iron, or possibly by organic matter. 
 
 Nitrogen may be added to the cycle as well as lost from it. 
 This takes place by means of the nitrogen-fixing bacteria which 
 occur largely in nodules on the roots of leguminous plants, such 
 as the clover, and also in some soils. These have the power of 
 removing nitrogen from the air and making it available for the 
 plant. 
 
 Practical use is made in the septic or ImhofT tanks of the 
 ability of micro-organisms to decompose organic matter and the 
 modern sewage filter is really a culture bed for the development 
 of nitrifying organisms which act on the sewage and render it 
 stable by oxidizing the nitrogen compounds to nitrates. 
 
 As will be seen from the above discussion, a sanitary chemical 
 analysis depends primarily upon the determination of the con- 
 dition of the nitrogen compounds in a sample of water. Each 
 of these will be discussed separately. 
 
 Albuminoid Ammonia. — This is the ammonia which is set 
 free by the action of boiling alkaline potassium permanganate 
 
62 AIR, WATER, AND FOOD 
 
 on nitrogenous organic matter. This may have entered the 
 water from perfectly harmless sources, such as dead vegetable 
 substances, or it may have come from waste material, such as 
 sewage. If from the former source, it is relatively stable and, if 
 present in any quantity, is accompanied by color in the water. 
 If from sewage, there may be little or no color, and the nitrog- 
 enous matter will be relatively unstable. The stability can be 
 determined by the action of the permanganate, stable substances 
 yielding ammonia only slowly and unstable substances losing it 
 rapidly. 
 
 The albuminoid ammonia gives no accurate measure of the 
 total nitrogenous organic matter present, as only about 50 per 
 cent is converted to ammonia, but it does give a good indica- 
 tion of whether or not the organic matter is easily decomposed, 
 and, therefore, whether or not it comes from sewage. A color- 
 less water should not contain over 0.15 parts per million of 
 nitrogen as albuminoid ammonia. The amounts found in good 
 ground waters are generally much lower than this figure. 
 Samples from storage reservoirs, in which there is plant life, may 
 contain larger amounts — up to 0.4 of a part. 
 
 The total organic nitrogen as determined by the Kjeldahl 
 method is sometimes used in place of the albuminoid ammonia, 
 but it gives no means of distinguishing between stable and un- 
 stable substances, and is not considered in this country to be as 
 good an index of pollution. 
 
 Free Ammonia. — This is the ammonia which comes off from 
 a water on direct distillation, the water being made alkaline if 
 necessary. The ammonia is probably present as ammonium 
 salts. Since this represents the first stage in the decomposition 
 of unstable nitrogenous organic matter, its presence in abnormal 
 quantities may be taken as an index of sewage pollution. The 
 amounts of ammonia present in good waters are generally very 
 small, and amounts over 0.15 to 0.2 parts expressed in terms of 
 nitrogen are sufficient to indicate pollution. In general, the free 
 ammonia is less than the albuminoid ammonia. If the reverse 
 is found it is an indication of trouble, unless both are very low. 
 
SAFE WATER 63 
 
 Cases sometimes arise where abnormally high free ammonia 
 does not indicate sewage, and the analyst should continually be 
 on the lookout for these exceptions. One may be found in wells 
 dug in glacial drift, where ammonia may have come from fossil 
 remains. Another occurs sometimes when a well is located in 
 close proximity to an ammonia refrigerating plant. 
 
 Nitrites. — Nitrites in a water are formed either from the oxi- 
 dation of ammonia or the reduction of nitrates. In either case, 
 they represent an unstable condition, usually accompanied by 
 large numbers of bacteria, and in most cases sewage pollution 
 or surface contamination. As has been said, "a state of change 
 is a state of danger," and the presence of nitrites reveals this 
 condition. As has been mentioned, nitrites may be formed 
 from nitrates by reduction due to iron or organic matter, but 
 such cases are not at all usual. 
 
 A good drinking water should be either entirely free from 
 nitrites or should contain them only in very minute quantities. 
 Amounts of 0.01 to 0.02 or more parts per million of nitrogen 
 are sufficient to condemn a water. But while the presence of 
 abnormal amounts of nitrites indicates danger, their absence is 
 no guarantee of the purity of a supply. 
 
 Nitrates. — As seen from the discussion of the nitrogen cycle, 
 nitrates are the final stage in the oxidation of nitrogen com- 
 pounds. Since they are food for plants, we would expect to 
 find only small amounts where there is any plant life. Thus, 
 surface waters are generally low in nitrates while ground waters 
 may be higher. It is probable that practically all nitrates in 
 waters have come originally from animal matter, as vegetable 
 nitrogen is not easily oxidized. In some cases, nitrates have 
 been known to come from chemical fertilizers used on fields. 
 
 High nitrates, combined with high chlorides, indicate past 
 pollution. "Past" is used either in the sense of time or dis- 
 tance. That is, fresh sewage may have found its way into a 
 well at some time past, and the nitrogen compounds may have 
 remained there, and been oxidized until, at the time of examina- 
 tion, nitrates predominated over the other forms. Or the sew- 
 
64 AIR, WATER, AND FOOD 
 
 age may have come from such a distance that oxidation has 
 taken place in the passage through the ground. 
 
 The presence of high nitrates is not generally accompanied 
 by sewage bacteria, and, therefore, immediate danger from the 
 supply does not exist. The objection to using such waters for 
 drinking is, first, that if pollution has once entered, it may enter 
 again, and, second, that the natural filter through which the 
 water is passing may, at some time, fail to work properly and 
 allow sewage bacteria, and with them possibly typhoid organ- 
 isms, to enter the water. In other words, past pollution indi- 
 cates a condition of possible future danger, and it is safest to 
 avoid this either by not drinking such water or by watching it 
 carefully by means of frequent examination. 
 
 Good surface waters are low in nitrates, over i part of nitrogen 
 as nitrate per million of water being a suspicious sign. Ground 
 waters often run much higher than this even when unpolluted, 
 but above 5.0 parts, is in most cases, sufficient to condemn the 
 water as unsafe for drinking. 
 
 Chlorides. — In interpreting the results of the analyses of the 
 various nitrogen compounds, it must be remembered that the 
 presence of any one of them in abnormal amounts is rarely 
 sufficient evidence upon which to declare a water unfit to drink. 
 The nitrogen compounds must be accompanied by an abnormal 
 amount of chlorides. Chlorides occur in waters principally as 
 the sodium salt, and as the results of analysis are. generally ex- 
 pressed in terms of chlorine, this latter term is the one in common 
 use. Human urine contains about 1 per cent sodium chloride, 
 and the amount of sewage entering a well or stream can be ap- 
 proximately determined by the rise in the chlorine content. 
 Furthermore, chlorine passes through no such cycle as that of 
 nitrogen, and common salt is not taken up by most plants, so 
 that once in a water there is no way by which the chlorine can 
 entirely disappear. If, then, abnormal amounts of chlorine 
 accompanied by abnormal amounts of one of the nitrogen com- 
 pounds are found in a water, it is a pretty sure indication that 
 sewage, in some state, is entering. 
 
STATE BOARD OF HEALTH 
 MAP OF THE 
 
 The lines represent normal chlorine. 
 
 STATE OF MASSACHUSETTS. Tto fleures show ob8e " ed ch,OTines which - 
 
 SHOWING 
 
 NORMAL CHLORINE. 
 
%&&■* x o w T 
 
 C o at 
 
 & JZ C 
 
 STATE BOARD OF \ 
 
 MAP OF THE 
 
 STATE OF MASSAC 
 
 SHOWING 
 
 NORMAL CHL 
 
SAFE WATER 65 
 
 The difficulty is to decide on what constitutes an abnormal 
 amount of chlorine, since salt occurs, to some extent, in most 
 soils and rocks, and in some places in very large quantities. 
 Some years ago, the Massachusetts State Board of Health at- 
 tempted to solve this problem by a careful study of a large 
 number of waters from all over the state. The chlorine was 
 determined in those which, from the surroundings and the other 
 constituents, could safely be regarded as free from pollution. 
 The figures obtained were placed on a map of the state at the 
 appropriate places and lines drawn through equal values. These 
 lines were termed "isochlors." This map is shown opposite. 
 (Note. The figures are given on the map in parts per 100,000.) 
 Since this map was made for Massachusetts, a number of other 
 states have made similar ones. The maps give with reasonable 
 accuracy the normal chlorine values for surface waters, but for 
 deep or artesian wells, the figures do not necessarily hold. Con- 
 sequently, in some states, for example in Illinois, it has been 
 found more satisfactory to give normal values according to the 
 source of the supply. 
 
 But the presence of chlorine in amounts above normal, alone, 
 is not sufficient to condemn a water. High chlorine and low 
 nitrogen are sometimes found together in a well water which 
 has been contaminated with wastes from a sink drain. The 
 ratio of nitrogen to chlorine can sometimes be used to distin- 
 guish between barn and human sewage, as the former contains 
 less chlorine than the latter for the same amount of nitrogen. 
 Excessively high nitrates with chlorine only slightly above 
 the normal sometimes indicates washings from a fertilized 
 field. 
 
 Mineral Matter. — Since water is a universal solvent, it is not 
 surprising to find considerable amounts of mineral matter under 
 the headings " total solids" and " hardness." How much cal- 
 cium sulphate or magnesium chloride or other soluble mineral 
 matter is allowable in a potable water is for the physician rather 
 than the chemist to say, but it seems to be the consensus of 
 opinion that, for the normal healthy person, the presence of 
 
66 AIR, WATER, AND FOOD 
 
 mineral matter, even in considerable quantities, is in no way 
 deleterious to the system. 
 
 As has been said, the human system possesses great adapta- 
 bility, not only for different foods, but for mineral substances 
 water-carried. Not so the steam-boiler or the laundry- tub, 
 which reacts very sensitively and affects the pockets of the 
 consumers. The determination of sulphates gives an indi- 
 cation as to how the hardness is divided, as permanent hard- 
 ness is caused principally by calcium sulphate. 
 
 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 
 frequently accompanied by free ammonia, which causes an 
 abundant growth of Crenothrix. It is also present in deep wells 
 in the form of bicarbonate, which precipitates on exposure to 
 warm air. 
 
 Organic Matter. — The amount of carbonaceous matter, de- 
 termined either by the oxygen-consumed test or by the loss on 
 igniting the solids, is of little use in interpreting a water analysis; 
 it is too difficult to get concordant results. The latter test may 
 sometimes be of service in a qualitative way, because the residue 
 from a recently polluted water often gives a distinctive disa- 
 greeable odor when ignited. In some laboratories, the quan- 
 titative determination is omitted entirely. 
 
 Dissolved Oxygen. — During the last few years, the determina- 
 tion of the oxygen dissolved in water has assumed considerable 
 importance, because of the use of the test as an indication of 
 the sanitary condition of a harbor or river. As long as sufficient 
 oxygen is present, the putrefactive changes which give off dis- 
 agreeable odors will not take place. There is some difference of 
 opinion as to how low the oxygen content may be allowed to fall 
 and still prevent these changes, but 40 per cent of saturation is 
 a safe figure to use. 
 
 
SAFE WATER 67 
 
 The test is also used to determine the putrescibility of a 
 sewage effluent as described later under that test. The object 
 is to determine the amount of oxygen absorbed by the organic 
 matter in the effluent. 
 
 Physical Tests. — These are of little importance as far as the 
 determination of pollution is concerned, but are generally in- 
 cluded in an examination in order to satisfy those who insist 
 that a water shall be attractive as well as safe. 
 
 Sewage Analysis. — Sewages may be tested to determine 
 their strength and constituents in order to help in deciding upon 
 the best method of treatment, and also as a basis for determin- 
 ing the amount of purification which any process gives. The 
 analysis of effluents is carried on also for this latter purpose, and 
 in order to determine their putrescibility. For an extended 
 discussion the reader is referred to another book.* 
 
 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 
 enable him to read clearly where another might see nothing. 
 The value of a water-analysis is in direct proportion to the 
 knowledge and experience of the one who interprets it. Clinical 
 skill in addition to theoretical knowledge is as much required 
 to interpret the figures obtained in the course of a water-analy- 
 sis, as in the diagnosis of a disease; and the analogy goes still 
 further, for just as some diseases are clearly defined, and others 
 
 * Fowler, " Sewage Works Analysis." 
 
68 AIR, WATER, AND FOOD 
 
 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 ground- 
 less, any more than the practice of medicine should be discarded 
 because inexperienced men make mistakes. 
 
 Is the water in any given case safe for drinking? To answer 
 this question there is needed a knowledge, wider than a chem- 
 ist'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 engineer, 
 and the sanitarian. 
 
CHAPTER VI 
 
 water: analytical methods * 
 
 Water-analysis cannot be carried on in an ordinary labora- 
 tory. In order to obtain satisfactory results, it is necessary to 
 have a room set apart for the purpose, 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 apparatus and the surroundings. It 
 is desirable that the room be well lighted, and, if possible, the 
 windows should face toward the north. 
 
 For the collection of water samples, glass-stoppered bottles of 
 about a gallon capacity are best. Those used in this laboratory 
 are of white glass, 15 inches high to the top of the stopper, five 
 and a half inches in diameter, and weigh about three pounds. 
 They have flat, mushroom stoppers, on each of which is engraved 
 a number to correspond 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 demi- 
 johns 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 
 material, and that the methods to be employed are extremely 
 delicate. Hence, in the case of many waters, careless handling 
 of the sample would contaminate the water to a sufficient ex- 
 tent to render valueless the results obtained in the laboratory. 
 
 * See "Standard Methods for the Examination of Water and Sewage," Ameri- 
 can Public Health Association, 1912. 
 
 69 
 
70 AIR, WATER, AND FOOD 
 
 In collecting samples, the following directions should be closely 
 followed:* 
 
 Directions for Collecting Samples for Analysis. — From a 
 Water-tap. — Let the water run freely from the tap for a few 
 minutes before collecting the sample. Then place the bottle 
 directly under the tap and rinse it out with the water three 
 times, pouring out the water completely each time. Place it 
 again under the tap; fill it to overflowing and pour out a small 
 quantity so that there shall be left an air-space under the stopper 
 of about an inch. Rinse off the stopper with flowing water; 
 put it into the bottle while still wet and secure it by tying over 
 it a clean piece of cotton cloth. Seal the ends of the string on 
 the top of the stopper. Under no circumstances touch the in- 
 side of the neck of the bottle or the stem of the stopper with 
 the hand, or wipe it with a cloth. 
 
 From a Stream, Pond, or Reserooir. — Rinse the bottle and 
 stopper with the water, if this can be done without stirring up 
 the sediment on the bottom. Then sink the bottle, with the 
 stopper in place, entirely beneath the surface of the water and 
 take out the stopper at a distance of twelve inches or more be- 
 low the surface. When the bottle is full replace the stopper, 
 below the surface if possible, and secure it as directed above. 
 It will be found convenient, in taking samples in this way, to 
 have the bottle weighted so that it will sink below the surface, 
 and to remove the stopper with a cord. It is important that the 
 sample should be obtained free from the sediment at the bottom 
 of a stream and from the scum on the surface. If a stream 
 should not be deep enough to admit of this method of taking a 
 sample, dip up the water with an absolutely clean vessel and 
 pour it into the bottle after the latter has been rinsed. 
 
 The sample of water should be collected immediately before 
 shipping by express, so that as little time as possible shall inter- 
 vene between the collection of the sample and its examination. 
 All possible information should be furnished concerning the 
 source of the water and of possible sources of contamination. 
 
 * Ann. Rept. Mass. State Board of Health, 1890, p. 520. 
 
WATER: ANALYTICAL METHODS 71 
 
 For example, in the case of a well, the proximity of dwellings, 
 cesspools, or drains should be recorded, and the character and 
 slope of the soil, whether toward or away from the well, should 
 be noted. In the case of a surface-water, mention any ab- 
 normal or unusual conditions; as, for instance, if the streams 
 or ponds are swollen by recent heavy rains, or are unusually low 
 in consequence of prolonged drought, or if there be a great deal 
 of vegetable growth in or on the surface of the water. Record, 
 in short, any circumstantial evidence which by any possibility 
 may aid in the final judgment. 
 
 The question of proper collection of samples is an important one, 
 and the chemist is perfectly justified in refusing to give an opinion 
 in regard to the purity of a water which he has not himself collected. 
 
 Preparation for Analysis. — Since changes in the composition 
 of a contaminated water are constantly going on, the analysis of 
 the sample should be begun without delay. The bottle is held 
 under the tap, and the neck and stopper are washed free from 
 adhering dust. The stopper is rinsed off with some of the water 
 from the bottle. 
 
 If the sample has stood for several hours, allowing suspended 
 matter to settle, the conditions of turbidity and sediment, as de- 
 scribed on page 108, may first be observed. The sample is then 
 thoroughly mixed and qualitative tests made for alkalinity, 
 ammonia and chlorides. Make the alkalinity test with methyl 
 orange indicator. If a sample is acid, it is necessary to make 
 alkaline, as described later, before starting the determinations 
 for free ammonia and chlorides. Make the test for ammonia 
 by adding two c.c. of Nessler reagent to 50 c.c. of the sample in 
 a Nessler tube. A reddish-brown color or precipitate means the 
 presence of large amounts of ammonia, and care should be taken 
 not to take too much of the sample for the quantitative deter- 
 mination (see page 74). A qualitative test for chlorides will 
 determine the amount of water to be taken for the analysis, — 
 a very slight opalescence meaning low chlorides, which will 
 necessitate the use of a 250-c.c. sample, while a distinct tur- 
 bidity or a precipitate will allow a 25-c.c. sample to be used. 
 
72 AIR ? WATER, AND FOOD 
 
 As the nitrogen compounds are more subject to important 
 changes than any others, it is desirable to make these determi- 
 nations first, the order of the remainder being immaterial. 
 
 It is essential that the sample of water be thoroughly mixed 
 each time any is withdrawn, as only in this way will the samples 
 removed be of constant composition. This is particularly im- 
 portant in dealing with sewages and sewage effluents, or where 
 there is a considerable amount of suspended matter. 
 
 The methods for preparing standard solutions and other 
 special reagents will be found in Appendix B. 
 
 Determinations of Free and Albuminoid Ammonia. — Am- 
 monia occurs in waters as ammonium salts, — carbonate, chlo- 
 ride, or nitrate. In sewages it may be partially present as the 
 hydroxide. On boiling an alkaline solution of these substances, 
 the salts are decomposed, as well as some unstable organic com- 
 pounds such as urea, and ammonia passes off and dissolves in 
 the condensed steam. The ammonia thus collected is called the 
 " free ammonia." If, now, alkaline potassium permanganate is 
 added to the water left after the free ammonia has been removed, 
 and the boiling continued, part of the nitrogenous organic mat- 
 ter will be decomposed with the liberation of ammonia. This 
 is termed " albuminoid ammonia." 
 
 The principles involved in the two determinations have been 
 described in the above definitions, that is, the water is first 
 boiled, and the steam condensed until all the free ammonia 
 has been removed. Then alkaline potassium permanganate is 
 added, and distillation continued until no more albuminoid 
 ammonia is evolved. The ammonia is determined in the dis- 
 tillates by means of Nessler reagent which gives a greenish 
 yellow with very small amounts of ammonia, and yellow to red- 
 dish brown with larger quantities. The exact amount of am- 
 monia is obtained by comparison of the colors obtained with 
 those from known amounts of ammonia. 
 
 Nessler reagent is a solution of potassium mercuric iodide 
 (K^Hglt) containing potassium hydroxide. The colored sub- 
 stance formed when this reacts with ammonia is dimercuram- 
 
 
WATER: ANALYTICAL METHODS 
 
 73 
 
 monium iodide (NHg 2 I • H 2 0), which is an ammonium iodide in 
 which the hydrogen atoms have been substituted by mercury. 
 This substance is slightly soluble in an excess of potassium iodide 
 and potassium hydroxide, giving a color proportional to the 
 amount of ammonia present. 
 
 Apparatus and Reagents. — The apparatus consists of a 
 750 c.c. round-bottomed flask, having square shoulders and a 
 narrow neck five inches long, and an ordinary Liebig con- 
 
 Fig. 8. 
 
 denser fitted with a block-tin inner tube T 3 g of an inch in diam- 
 eter which extends just through a cork stopper closing the 
 flask. The apparatus is set so that the distillate may be col- 
 lected directly in a 50 c.c. Nessler tube. The flasks are heated 
 either with the free flame of a Bunsen burner or with an electric 
 flask heater. These latter are somewhat slow in heating up 
 and in cooling, but give an even heat with just about the proper 
 rate of distillation and show little tendency to cause " bump- 
 ing." In place of the Liebig condenser, the tin tube may be 
 passed through a copper or galvanized iron tank (see Fig. 8), 
 
74 AIR, WATER, AND FOOD 
 
 fitted with proper inlets and outlets, and serving as a con- 
 denser for a number of flasks. New flasks are treated with 
 boiling dilute sulphuric acid and potassium bichromate before 
 they are used. New corks should be steamed out for one or 
 two hours. A good sound cork will last for several months 
 with daily use. 
 
 The Nessler tubes used should be of the same height up to 
 the 50 c.c. mark. 
 
 Reagents necessary are Nessler solution, alkaline potassium 
 permanganate, a standard ammonium chloride solution and 
 ammonia-free water (see Appendix B). 
 
 Procedure. — Free the apparatus from ammonia by placing 
 500 c.c. of ammonia-free water in the flask and distilling. Col- 
 lect the distillate in 50 c.c. Nessler tubes, and test each tube as 
 it is filled, by adding two c.c. of Nessler reagent and comparing 
 the color obtained after waiting five minutes with that obtained 
 by adding two c.c. of Nessler reagent to 50 c.c. of ammonia-free 
 water. This latter gives a zero standard. Continue until the 
 distillate is free from ammonia and then pour the water left in 
 the flask into the bottle marked " ammonia-free residues." 
 
 While this is going on make a qualitative test on the sample 
 of water to determine the amount which should be used for the 
 quantitative determination. To do this, add to 100 c.c. of the 
 water, removed from the bottle only after thorough mixing, 
 one c.c. of 10 per cent copper sulphate solution, and one c.c. of 
 50 per cent potassium hydroxide. Allow to settle and filter 
 through a dry paper into a 50 c.c. Nessler tube, discarding the 
 first 10 c.c. of filtrate. Add two c.c. of Nessler reagent, and 
 allow to stand for 10 minutes. Make a standard by placing 
 two c.c. of the standard ammonium chloride solution in a Nessler 
 tube, making up to 50 c.c. with ammonia-free water, mixing 
 thoroughly and adding two c.c. of Nessler reagent. If the color 
 obtained from the sample of water is less than this standard, 
 use a 500 c.c. sample of the water for the determination; if 
 equal to or greater than the standard, use a 100 c.c. sample; 
 if the color is so deep that a precipitate forms, use a 10-c.c. 
 
WATER: ANALYTICAL METHODS 75 
 
 sample. For sewages five or 10 c.c. are sufficient. In case less 
 than 500 c.c. are used, dilute the amount to this volume with 
 ammonia-free water. 
 
 Test some of the water with methyl orange for acidity. If 
 acid, 0.5 gram of pure sodium carbonate must be added before 
 starting the distillation. The great majority of drinking waters 
 are alkaline, but once in a while an acid water turns up, and it 
 is well to be on the lookout. Acid sewages and sewage filter 
 effluents are not uncommon. 
 
 When the apparatus has been freed from ammonia, shake 
 thoroughly the bottle containing the water sample, and measure 
 out in a calibrated flask 500 c.c, or a smaller amount, according 
 to the qualitative test described above, adding enough ammonia- 
 free water to make the total volume at least 500 c.c, and 
 pour into the distilling flask. If necessary, add sodium car- 
 bonate. Distill three portions of 50 c.c. each into well-rinsed 
 Nessler tubes. Regulate the height of the flame so that the 
 time of distilling 50 c.c. shall not be more than eight and not 
 less than five minutes. In most cases three portions are suffi- 
 cient to collect all the free ammonia, but it is well to test the 
 last portion with Nessler reagent, and compare it with a zero 
 ammonia standard, before proceeding further. Save these por- 
 tions for nesslerization, as they contain all the free ammonia. 
 
 After the free ammonia has been distilled off, allow the con- 
 tents of the flask to cool for to minutes; then add 40 c.c. of 
 alkaline permanganate through a funnel, taking care that none 
 of the alkaline solution touches the neck of the flask, and pro- 
 ceed with the distillation of the albuminoid ammonia. With 
 colored waters distill off five portions of 50 c.c. each; with 
 colorless waters, three or four portions will suffice. These 
 portions contain the albuminoid ammonia. 
 
 Unless permanent standards are used, prepare standards by 
 adding to Nessler tubes nearly filled with ammonia-free water 
 varying quantities of the standard ammonium chloride solution; 
 for instance, 0.1, 0.3, 0.5, 0.7, 1.0, 1.3, 1.5, 2.0, 2.5, 4.0, 6.0 c.c. 
 The standard ammonium chloride solution contains 0.0000 1 gram 
 
7 6 
 
 AIR, WATER, AND FOOD 
 
 N in one cubic centimeter. Mix the contents of the tubes by ro- 
 tating them between the palms of the hands or by pouring into 
 another Nessler tube and back again (never shake them like a 
 test-tube or stir them with a rod), allow them to stand for a few 
 minutes and add two cc. of Nessler reagent to each tube and 
 to each of the portions of distillate. At the end of 10 minutes 
 match the colors and record the amount of ammonia in terms 
 of cubic centimeters of the standard ammonium chloride solu- 
 tion. From the value of this solution calculate the amounts of 
 free and albuminoid ammonia as parts of nitrogen per million 
 of water. 
 
 As an example, the following results from distilling 500 cc. 
 may be given. 
 
 Free ammonia. 
 
 Albuminoid Ammonia. 
 
 ist 50 CC 
 2nd 50 CC 
 3d 50 CC, 
 
 0.7 CC 
 0.3 CC 
 0.0 CC 
 
 ist 50 cc, 4.5 CC 
 2nd 50 CC, 2.8 CC 
 3d 50 cc, 1.5 CC. 
 4th 50 cc, 1.0 cc 
 5th 50 cc, 0.5 cc 
 
 1.0 CC 
 
 10.3 cc 
 
 In this case, the free ammonia would be 0.020 and the albumi- 
 noid ammonia 0.206 parts per million. 
 
 In dealing with sewages or sewage effluents, which are very 
 high in free ammonia, if the ammonia were collected in three 
 portions, so much would distill over in the first portion that the 
 color given with the Nessler reagent would often be too deep to 
 read or a precipitate might form. To avoid this, the total dis- 
 tillate of 150 to 175 cc is collected in a 200-cc graduated flask, 
 made up to the mark, thoroughly mixed by pouring into a clean 
 dry beaker and back again, and then 50 cc of it taken for 
 nesslerization. In this way, the ammonia is distributed more 
 evenly in the distillate and the determination is not sacrificed. 
 
 If free ammonia only is desired in a sewage or sewage effluent, 
 a direct determination is to be preferred over distillation. For 
 
WATER: ANALYTICAL METHODS 77 
 
 this, proceed as directed in the qualitative test for ammonia, ex- 
 cept that a smaller amount of the filtrate should be used, two 
 or five c.c, and this made up to 50 ex. with ammonia-free water, 
 treated with Nessler reagent, and matched against standards 
 as just described. 
 
 Notes. — Where a large number of determinations are made 
 at frequent intervals, permanent Nessler standards are a great 
 convenience. These should be made according to directions 
 found in " Standard Methods,"* but should be adjusted by 
 comparison with nesslerized standards made from ammonium 
 chloride solution. 
 
 It is impossible to convert all of the organic nitrogen into 
 ammonia by boiling with alkaline permanganate. The amount 
 of ammonia which is thus obtained depends not only upon the 
 character of the substances, but also upon the concentration of 
 the solution and the rate of boiling. In order that the albu- 
 minoid ammonia in potable waters shall bear some definite 
 relation to the total organic nitrogen, it is necessary that 
 conditions shall be duplicated as nearly as possible in differ- 
 ent determinations; that is, the alkaline permanganate must Be 
 added to a definite volume of water, and the boiling must be 
 carried on at a definite rate. Some of the highly-colored surface- 
 waters give up their nitrogen very slowly by this treatment; 
 polluted waters, on the other hand, yield the ammonia more 
 rapidly, so that the observation of the relative amounts found 
 in the successive portions is of the utmost importance in form- 
 ing a judgment. 
 
 A depth of color given by six c.c. of the standard ammonium 
 chloride with the Nessler reagent is about the limit of satisfactory 
 comparison in the 11-inch 50 c.c. tubes. The color given by 
 10 or 12 c.c. of the standard may be matched in the 100 c.c. tubes 
 with a depth of five inches and a diameter of i\ inches. 
 
 For most cases, where great exactness is not essential, it is 
 possible to divide the 50 c.c. or the 100 c.c. portion into two 
 
 * "Standard Methods of Water Analysis," American Public Health Asso- 
 ciation, 1912, p. 17. 
 
78 AIR, WATER, AND FOOD 
 
 equal parts by pouring into a tube the exact counterpart of the 
 standard tube and matching the color. It is even possible to 
 approximate closely the correct result by the use of a foot rule. 
 The standard is, we will assume, five c.c. The height of the 
 liquid in the tube to be tested we will call nine inches. If the 
 height of the column left which matches five c.c. is three inches, 
 then the reading was 15 c.c. of the standard. 
 
 The limit of solubility of the mer cur-ammonium iodide is 
 reached at 25 or 30 c.c. of the standard in 50 c.c. The incipient 
 precipitate not only changes the color of the solution, but causes 
 a slight milkiness or turbidity which prevents a sharp reading 
 of the color. 
 
 The test is an excellent example of quantitative color work 
 when carried out under strictly comparable conditions. 
 
 It should, perhaps, be stated that in both the ammonium and 
 nitrate determinations, as also in that of iron, dilution of the 
 sample in which the color is already developed does not give a 
 correct result. Therefore dilution, if necessary, must be made 
 before the reagents are added. 
 
 In order to secure the most accurate results, it is important 
 that the temperature of the distillates to be nesslerized and of 
 the standards be the same, since the warmer solutions give a 
 more intense color with the Nessler reagent. 
 
 Total Organic Nitrogen, Kjeldahl Process. — The principles 
 involved in the method consist in the oxidation of the carbon 
 and hydrogen of the organic matter with boiling sulphuric acid, 
 the nitrogen being converted into ammonia and held by the acid 
 as ammonium sulphate. The ammonia is then liberated and 
 distilled off from an alkaline solution. 
 
 Apparatus and Reagents. — The apparatus used is that shown 
 in Fig. 9. This is an arrangement for distilling with steam. 
 The reagents needed are nitrogen-free sulphuric acid and potas- 
 sium hydroxide (see Appendix B) . 
 
 Procedure. — Measure 500 c.c. of the water into a round- 
 bottomed flask of 750 c.c. capacity and boil until about 200 c.c. 
 have been driven off. (The free ammonia which is thus ex^ 
 
WATER: ANALYTICAL METHODS 
 
 79 
 
 pelled may be determined, if desired, by connecting the flask 
 with a condenser.) Allow the water remaining in the flask to 
 cool, and add 10 ex. of pure concentrated sulphuric acid free 
 from nitrogen. Mix by shaking; 
 place the flask in an inclined posi- 
 tion on wire gauze under the hood 
 and boil cautiously until the water 
 is all driven off. Place a small 
 funnel in the neck of the flask to 
 prevent the escape of acid fumes, 
 and continue the heating for at 
 least half an hour after the sul- 
 phuric acid becomes white. Mean- 
 while, rinse out the distilling ap- 
 paratus and free it from ammonia 
 as usual. Then, after the acid in 
 the digestion flask has cooled, rinse 
 down the neck of the flask with 
 ioo c.c. of ammonia-free water and 
 attach the flask to the distillation 
 apparatus. Add ioo c.c. of potas- 
 sium hydroxide solution through 
 the separatory funnel and distill 
 off the ammonia with steam, re- 
 ceiving the distillate in a 250-c.c. graduated flask. Conduct 
 the distillation rather slowly until the first 50 c.c. have distilled 
 over, then distill more rapidly until about 175 c.c. have been 
 collected. Make the volume of the distillate up to 250 c.c. 
 with ammonia-free water, mix it thoroughly and take 50 c.c. 
 for nesslerization. 
 
 The use of mercury and of potassium permanganate to assist 
 in the oxidation has been found to be unnecessary, as the organic 
 matter in natural waters is much more easily oxidized than in 
 other substances, — flour, for instance. The presence of nitrates 
 and nitrites in waters has not been found to interfere with the 
 accurate determination of the organic nitrogen. The error, 
 
 Fig. 9. 
 
80 AIR, WATER, AND FOOD 
 
 which has been found by Kjeldahl and Warrington to be caused 
 by the presence of nitrates seems to disappear when the organic 
 material is diluted to the considerable extent that exists in 
 natural waters. The high chlorine found in some well-waters 
 does not interfere with the method to any extent, but this de- 
 termination does not possess much value in this class of waters, 
 which are low in organic nitrogen. 
 
 In carrying out the digestion with sulphuric acid, the greatest 
 care must be taken to prevent access of ammonia or dust from 
 any source. The acid solutions will absorb ammonia from the 
 air or from the dust of the laboratory if they are allowed to re- 
 main uncovered for any length of time. This source of error 
 may in some instances be sufficiently large to render a determi- 
 nation valueless, even in a room which is, to all appearances, free 
 from ammonia-fumes. Hence, the operation should, if possible, 
 be carried to completion within twenty-four hours, and for every 
 set of determinations a blank analysis should be made with am- 
 monia-free water in order to make a correction for the ammonia 
 in the reagents, and for that accidentally introduced during the 
 process. 
 
 As the result of many hundred comparative determinations 
 of the organic nitrogen and of the albuminoid ammonia in nat- 
 ural waters which take their origin in the glacial drift, it has 
 been found that the nitrogen given by the albuminoid-ammonia 
 process, as directed in the previous pages, is about one-half of the 
 total organic nitrogen as given by the Kjeldahl process; in the 
 case of sewages and polluted waters, it is very variable owing to 
 their irregular composition. 
 
 Determination of Nitrogen in the Form of Nitrites. — This de- 
 termination depends on the formation of a pink azo dye by the 
 interaction of sulphanilic acid, naphthylamine acetate, and nitrous 
 acid. If an excess of the first two reagents is used, the amount 
 of dye and, therefore, the depth of color will be proportional to 
 the amount of nitrite present in the water. The color is then 
 compared with a series of standards made from a sodium nitrite 
 solution of known strength and the nitrite computed in terms of 
 nitrogen. 
 
WATER: ANALYTICAL METHODS 8 1 
 
 The reactions which take place are, first, the diazotizing of the 
 sulphanilic acid by the nitrous acid present, and then the inter- 
 action of this diazo compound with naphthylamine to form the 
 colored substance, a-naphthylamine-para-azo-benzene-para-sul- 
 phonic acid. 
 
 /NH 2 
 CeH4 + Ci H 7 NH 2 + HN0 2 -> 
 
 X S0 3 H 
 
 / N = N \ 
 Ci H 6 C 6 H 4 + 2 H 2 0. 
 
 X NH 2 S0 3 H / 
 
 Apparatus and Reagents. — The only special apparatus needed 
 is a number of ioo c.c. Nessler tubes. The reagents used are a 
 standard sodium nitrite solution (i c.c. contains o.ooooooi 
 gram nitrogen), a solution of sulphanilic acid in acetic acid, a 
 solution of naphthylamine acetate, and a suspension of alumi- 
 num hydroxide (see Appendix B). 
 
 Procedure. — If the water is colorless, measure out ioo c.c. 
 into a ioo-c.c. Nessler tube. If the water possesses color which 
 cannot be removed by simple filtration, it should be decolorized 
 as follows: Thoroughly rinse with the water a 250-c.c. glass- 
 stoppered bottle; pour into it about 200 c.c. of the sample, 
 add about three c.c. of milk of alumina and shake the bottle vig- 
 orously. Let stand for 10 or 15 minutes and filter through a 
 small plaited filter which has been thoroughly washed with 
 water free from nitrites. To 100 c.c. of the filtered sample or of 
 the originally colorless water add 10 c.c. of the sulphanilic acid 
 in acetic acid and 10 c.c. of naphthylamine acetate solution. 
 A pink color shows the presence of nitrite. To determine the 
 amount* of nitrite present make up standards by placing 5 c.c, 
 10 c.c, 15 c.c, and 20 c.c each of the standard nitrite solution 
 in ioo-c.c Nessler tubes. Make up to 100 c.c. with nitrite-free 
 water, mix by pouring into a Nessler tube and back to the original 
 tube, and then add the reagents as before. Allow to stand 10 
 
 * Standard color papers and also acid solutions of fuchsine are used for nitrite 
 standards. Neither of these has been found very satisfactory in this laboratory. 
 
82 AIR, WATER, AND FOOD 
 
 minutes, and match with the color obtained from the water 
 sample. If this does not match any of the standard colors, 
 make up intermediate standards. Do not attempt to match 
 colors closer than to one c.c. of the nitrite solution. If the 
 color is deeper than that given by 20 c.c. of the standard nitrite 
 solution, start a new determination using a smaller quantity of 
 water and diluting to 100 c.c. with the ammonia-free water. 
 
 One c.c. of the standard nitrite solution equals 0.0000001 
 gram nitrogen. Determine the number of c.c. needed to match 
 the color obtained from the water sample and calculate the 
 results in parts of nitrogen per million of water. 
 
 Notes. — In case the color obtained is deeper than 20 c.c. of 
 the standard, an aliquot part may be measured, as described 
 under the ammonia determination. This will be sufficiently 
 accurate for most purposes. 
 
 When once obtained, the color will remain unchanged for one- 
 half to three-quarters of an hour. If left for a longer time, the 
 nitrites absorbed from the air will noticeably increase the color. 
 
 Determination of Nitrogen in the Form of Nitrates.* — This 
 determination depends on the action of nitric acid on phenol- 
 disulphonic to form nitrophenoldisulphonic acid, which gives 
 an intensely yellow color in alkaline solution. The reactions 
 involved can be expressed as follows: 
 
 / OH / en tt 
 
 C 6 H 3 - SO3H + HNO3 -> C 6 H 2 < ^ 3 £ + H 2 
 N S0 3 H 
 
 -OH 
 /SO3H 
 
 ^N0 2 
 /OK 
 
 CeH ^ SO3H+ 3 KOH -> C 6 H 2 < Sgj| + 3 H 2 
 
 N ° 2 \no 2 
 
 Reagents. — The reagents needed are a standard nitrate solu- 
 tion of which one c.c. contains 0.000001 gram nitrogen, and phe- 
 
 * Sprengel, Fogg, Ann., 1863, 121, p. 188; Grandval and Lajoux, Compt. rend., 
 1865, 101, p. 62; Gill, /. Am. Chem. Soc, 1894, 16, p. 122; Chamot & Pratt, /. 
 Am. Chem. Soc, 1909, 31, p. 922; 1910, 32, p. 630; Chamot, Pratt and Redfield, 
 /. Am. Chem. Soc, 191 1, 33, p. 366. 
 
WATER: ANALYTICAL METHODS 83 
 
 noldisulphonic acid (see Appendix B). Care should be taken 
 in making this latter reagent as the results are dependent upon 
 its composition. 
 
 Procedure. — For ground waters, measure with a pipette two 
 samples of the water, one of two c.c. and the other of five ex., 
 into three-inch porcelain evaporating dishes and evaporate just 
 to dryness on the steam bath or electric plate run at low heat. 
 For surface-waters use 10 c.c. If the water is colored, decolor- 
 ize with alumina as described under nitrites. Do not allow the 
 residue to remain on the steam bath after all the water has been 
 evaporated. Cool, add six drops of phenoldisulphonic acid and 
 rub with a glass rod to insure complete contact of the acid and 
 residue. Then add seven c.c. of distilled water and three c.c. of 
 30 per cent potassium hydroxide solution and mix thoroughly. A 
 yellow color shows the presence of nitrates. Place this solution 
 in a short Nessler tube* for comparison with a standard. This 
 standard is prepared as follows: Place one c.c. of potassium hy- 
 droxide solution in a short Nessler tube and add standard nitrate 
 solution from a burette until the color of the standard nearly 
 matches that of the water sample. Make the volumes of the 
 two solutions equal by diluting the standard and then add more 
 standard nitrate solution until the colors exactly match. Use 
 the sample of water for comparison which has the lighter color, 
 unless there is no yellow at all. In case the &ve c.c. sample 
 gives no color, repeat the determination, using 10 c.c. If this 
 gives no color nitrates are absent. If the two c.c. sample gives 
 a color which requires more than 10 c.c. of the standard, repeat 
 the determination, using smaller amounts of water. 
 
 The standard nitrate solution contains 0.000001 gram N per 
 c.c. From the amounts of standard nitrate solution and of 
 water used calculate the amount of nitrate present expressed as 
 nitrogen in parts per million of water. 
 
 Notes. — High chlorides seriously affect the accuracy of the 
 method. This is noticeable in dealing with sea water and deep 
 wells which contain large amounts of sodium chloride. In this 
 * An ordinary 50-c.c. Nessler tube cut off to a length of about five inches. 
 
84 AIR, WATER, AND FOOD 
 
 case, the reduction method with alkali and aluminum foil and 
 distillation of the ammonia formed, is to be recommended.* For 
 most drinking waters it is not necessary to use this method, 
 which requires a much longer time than that described above. 
 
 Determination of Chlorine. — Chlorine is present in waters 
 in the form of chlorides, and the term " chlorine" is used to 
 mean " chlorides " as the results of analysis are given in terms 
 of chlorine. 
 
 The determination is made by titration with silver nitrate in 
 a solution alkaline with bicarbonates, — the condition generally 
 existing in natural waters, — potassium chromate being used as 
 an indicator. 
 
 Reagents. — The solutions required are a standard sodium 
 chloride solution (i c.c. contains o.ooi gram CI), a solution of 
 silver nitrate about one-half as strong, and potassium chromate 
 indicator (see Appendix B). 
 
 Procedure. — Standardize the silver nitrate solution by ti- 
 trating against a standard sodium chloride solution. To do this 
 place 25 c.c. of distilled water in a 6-inch porcelain evaporating 
 dish, add three drops of potassium chromate indicator, and then 
 run in from a burette a measured amount of sodium chloride 
 solution, about five c.c. being sufficient. It is not necessary to 
 add exactly five c.c, but it is necessary to know the exact amount 
 added. Now add silver nitrate solution from a burette until 
 the yellow color of the solution has changed to a faint reddish 
 brown. The end point is best seen if 25 c.c. of distilled water 
 and three drops of indicator are placed in a 6-inch dish which 
 is set beside the dish in which the titration is being carried on. 
 This gives a standard color and the end point is reached when 
 the solution being titrated shows the slightest appearance of 
 red as compared with the standard. From the results of the 
 standardization calculate the value of silver nitrate solution in 
 terms of sodium chloride solution and in terms of CI per c.c. 
 
 Test the water to be analyzed with phenolphthalein and with 
 methyl orange. It should be acid to the former and alkaline 
 
 * See "Standard Methods," p. 25. 
 
WATER: ANALYTICAL METHODS 85 
 
 to the latter. If alkaline to phenolphthalein neutralize the 
 sample measured for titration with dilute sulphuric acid. If 
 acid to methyl orange neutralize with sodium bicarbonate. 
 
 Highly colored waters should be decolorized before titration 
 as the color interferes with the end point. To do this shake 
 some of the sample in an Erlenmeyer flask with milk of alu- 
 mina, one c.c. of the latter being used for each 100 c.c. of water. 
 Heat the mixture rapidly to boiling, allow to settle and decant 
 through a filter. 
 
 Make a qualitative test for chlorides on the sample of water. 
 If only a faint opalescence appears, a 250 c.c. sample must be 
 used for analysis; if a marked cloudiness or a precipitate is 
 formed, a 25 c.c. sample may be used. If the larger sample is 
 found to be necessary, evaporate to about 25 c.c. on a steam 
 bath or electric plate; avoid boiling. Cool before titrating. 
 
 To 25 c.c. of the water, measured with a pipette, or an evap- 
 orated 250 c.c. sample, in a 6-inch porcelain dish, add three drops 
 of indicator and about five c.c. of sodium chloride solution, the 
 exact amount being measured as in the standardization. Then 
 run in silver nitrate solution until the end point is reached, 
 using the standard color as before. 
 
 From the amounts of silver nitrate and sodium chloride solu- 
 tions used calculate the amount of chlorine present in parts per 
 million. 
 
 Notes. — With waters containing large amounts of chlorides, 
 the addition of sodium chloride in the titration may be omitted. 
 
 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 chloride pres- 
 ent.* 
 
 Determination of the Carbonaceous Matter or " Oxygen 
 Consumed." — This determination is supposed to give the 
 amount of oxygen absorbed by the organic matter present in 
 the water. Except in sewage analysis, the results are of little 
 
 * Hazen, Am. Chem. J., 1889, 11, p. 409. 
 
86 AIR, WATER, AND FOOD 
 
 importance, and the determination may be omitted without 
 appreciably affecting the interpretation of the results of the 
 whole analysis. 
 
 The oxygen consumed is determined by allowing an excess 
 of potassium permanganate in acid solution to act on the or- 
 ganic matter in the water under certain conditions, and then 
 titrating the excess of permanganate with ammonium oxalate. 
 
 Equations : 
 
 4 KMn0 4 + 6 H 2 S0 4 + 5 C -> 2 K 2 S0 4 + 4 MnS0 4 + 6 H 2 
 + 5 C0 2 . 
 
 2 KMn0 4 + 3 H 2 S0 4 + 5 C 2 H 2 4 - 2 H 2 -> K 2 S0 4 + 2 MnS0 4 
 + ioC0 2 + i8H 2 0. 
 
 Reagents. — The solutions required are a standard ammo- 
 nium oxalate solution (1 ex. equals 0.0001 gram oxygen), a 
 potassium permanganate solution of approximately the same 
 strength, and 1-3 sulphuric acid (see Appendix B). 
 
 Procedure. KubeVs Hot Acid Method. — Standardize the 
 potassium permanganate against the oxalate in the following 
 way: Measure 100 c.c. of distilled water into a 250-c.c. flat- 
 bottomed flask, add 10 c.c. of sulphuric acid (1-3) and then add 
 from a burette a measured quantity (about 10 c.c.) of standard- 
 ized potassium permanganate solution. Place the flask on a 
 wire gauze or electric stove and heat quickly to boiling. Boil 
 the solution gently for exactly five minutes, remove it from the 
 flame, cool for one minute, and add from a burette sufficient 
 ammonium oxalate to decolorize the solution. Titrate back 
 with the permanganate to a faint permanent pink color. Cal- 
 culate the value of the permanganate in terms of standard 
 ammonium oxalate and of oxygen. 
 
 For the analysis proceed just as in the standardization, re- 
 placing the distilled water by the sample to be tested. The 
 oxygen consumed value for the water under examination is 
 obtained from the number of c.c. of permanganate used in 
 excess of that required to react with the oxalate added in the 
 determination. Calculate the results in parts of oxygen per 
 million of water. 
 
WATER: ANALYTICAL METHODS 87 
 
 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. or less 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 certain extent, 
 with the hydrogen, but not with the nitrogen. The amount of 
 oxygen consumed bears some relation, therefore, to the amount 
 of organic carbon present in the water, but this relation cer- 
 tainly 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 compara- 
 tive 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 solu- 
 tion upon the water-bath for half an hour instead of boiling it 
 for five minutes. The results, however, will not be exactly 
 comparable with those obtained by boiling. 
 
 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 some- 
 what varying, relation. 
 
 Determination of the Residue on Evaporation and the Loss 
 on Ignition. — Procedure. — Carefully clean a large platinum 
 dish, ignite for a few minutes over a burner, cool in a desiccator 
 and weigh. 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 one hour, 
 
 * Woodman, /. Am. Chem. Soc, 1898, 20, p. 497. 
 
88 AIR, WATER, AND FOOD 
 
 cool in a desiccator over sulphuric acid, and weigh. The increase 
 in weight gives the "total solids" or "residue on evaporation." 
 
 The residue should be ignited and the loss on ignition noted. 
 Heat the dish in a "radiator," which consists of another plat- 
 inum 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 platinum wire. Over the inner dish is suspended 
 a disc of platinum-foil to radiate back the heat into the dish. 
 The larger platinum dish is heated to bright redness by a triple 
 gas-burner. An electric muffle may be used in place of the radi- 
 ator. This should be run at a temperature of about 500 C. 
 Heat the dish 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, 
 slightly moisten the residue with a few drops of distilled water. 
 Heat the residue in the oven for an hour; cool in a desiccator 
 and weigh. This gives the weight of "fixed solids," the differ- 
 ence being the "loss on ignition." Save the residue for the de- 
 termination of iron. 
 
 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 possess any real 
 value, it is necessary to regulate carefully the heat during the 
 ignition, so as to destroy the organic matter without decompos- 
 ing calcium carbonate or volatilizing the alkali chlorides. 
 
 This is what the use of the radiator or muffle is intended to 
 accomplish, and in the case of surface-waters with low mineral 
 content 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 determination of 
 "loss on ignition" is, therefore, generally meaningless, although 
 an approximation to the amount of organic matter can be ob- 
 
WATER: ANALYTICAL METHODS 89 
 
 tained 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 modification, the loss is consider- 
 able when magnesium salts are present, owing to the evolution of 
 carbonic acid. 
 
 It is the practice in some laboratories to ignite over a direct 
 flame, taking care that the dish does not reach a temperature 
 above a faint redness. 
 
 The behavior on ignition is oftentimes significant. Swampy 
 or peaty waters give a brownish residue on evaporation to dry- 
 ness, which blackens or chars, and this black substance burns 
 off quite slowly. The odor of the charring is like that of char- 
 ring wood or grain; sometimes sweetish, but not at all offensive. 
 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 recorded in the report. 
 
 Determination of Iron. — This depends on the color produced 
 by the action of potassium sulphocyanate on ferric chloride. 
 The color obtained is compared with standards. 
 
 Reagents. — The solutions needed are a 1-1 hydrochloric 
 acid, a potassium sulphocyanate solution, and a standard iron 
 solution made from ferrous ammonium sulphate, one c.c. of 
 this containing 0.0001 gram iron (see Appendix B). 
 
 Procedure. — Treat the residue from the loss on ignition, or 
 that obtained by the evaporation of 100 c.c. of the water, with 
 five c.c. of 1-1 hydrochloric acid, warming on the steam-bath 
 or hot plate so as to dissolve as much as possible of the mineral 
 matter. Wash the solution with distilled water into a 100-c.c. 
 Nessler tube, filtering if there is any insoluble matter. Make 
 up to about 50 c.c. with distilled water. Add potassium per- 
 manganate solution, a few drops at a time, until the solution 
 remains pink for 10 minutes. This is to oxidize any ferrous 
 chloride to the ferric condition. Then add 10 c.c. of potassium 
 sulphocyanate solution and make the volume up to the 100 c.c. 
 
90 AIR, WATER, AND FOOD 
 
 mark with distilled water. Iron gives a red color. If iron is 
 present prepare a blank standard by placing 75 c.c. of distilled 
 water, five c.c. of hydrochloric acid and 10 c.c. of potassium 
 sulphocyanate solution in a 100 c.c. Nessler tube. Now add 
 from a burette, standard iron solution until the color nearly 
 matches that obtained in the determination. Fill the tube with 
 distilled water to the 100 c.c. mark and continue adding the iron 
 solution until the color of the blank exactly matches that of the 
 determination. From the number of c.c. of standard iron solu- 
 tion used calculate the amount of iron in the water. 
 
 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 solution 
 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 
 sulphocyanate, since the color fades appreciably on standing. 
 If the color is greater than that given by 3.5 c.c. of the standard 
 solution an aliquot part should be used. In this case sufficient 
 hydrochloric acid and potassium sulphocyanate should be added 
 so that the same amounts of these are present as given in the 
 above directions. 
 
 Determination of Hardness. — Soap (Clark's) Method. 
 This method really gives the soap consuming power and not 
 the true total hardness, but it is in general use for sanitary pur- 
 poses, and where the water is to be used for household purposes 
 only, really gives what is most wanted. The determination 
 depends on the fact that soap forms an insoluble precipitate 
 with the calcium and magnesium salts in the water. As soon 
 as the precipitation of the latter is complete a permanent lather 
 is formed. This serves as the end point. The hardness is 
 expressed in terms of calcium carbonate per million. 
 
 Reagent. — A standard soap solution (see Appendix B) . 
 
 Procedure. — 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 
 
WATER: ANALYTICAL METHODS 91 
 
 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 Appendix A. 
 
 Notes. — The importance of adding the soap in small quan- 
 tities cannot be too strongly emphasized, especially in the pres- 
 ence of magnesium compounds. The presence of magnesium 
 salts will be recognized by the peculiar curdy appearance 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. 
 
 By reference to the table it will be observed that values are not 
 given for more than 16 c.c. of the soap solution. If in any case 
 the water under examination requires more than 10 c.c. of the 
 standard soap solution, a smaller portion of 25 c.c, 10 c.c. or 
 even two c.c, as the case may require, is measured out and made 
 up to a volume of 50 c.c with recently distilled water. If the 
 volume of soap used is always about seven 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 undissociated soap to allow of the increase of surface tension 
 to a point at which soap-bubbles will persist. 
 
 Hehner's Acid Method* — The temporary hardness of a water 
 is that part of the total hardness which can be removed by 
 boiling. It is due to the presence of the bicarbonates of calcium 
 
 * Hehner, Analyst, 1883, 8, p. 77; Draper, Chem. News, 1885, 51, p. 206; Ellms, 
 /. Am. Chem. Soc, 1899, 21, p. 239. 
 
92 AIR, WATER, AND FOOD 
 
 and magnesium. These give an alkaline reaction to indicators 
 such as methyl orange and erythrosine, and can be titrated 
 with standard acid. The results obtained will differ slightly 
 from the true temporary hardness, on account of the solubility 
 of calcium and magnesium carbonates which are formed when a 
 solution of the bicarbonates is boiled, but the results are close 
 enough for practical purposes. 
 
 Permanent hardness is that which is not removed by boiling, 
 and is due mainly to the presence of the sulphates and chlorides 
 of calcium and magnesium. After removing the temporary 
 hardness by boiling, the permanent hardness, i.e., the calcium 
 and magnesium remaining in solution, may be determined by 
 adding standard "soda reagent" (a mixture of equal parts of 
 sodium hydroxide and sodium carbonate), which precipitates 
 the magnesium as hydroxide and the calcium as carbonate. 
 The excess of soda reagent added is then determined by titration 
 with standard acid, — the amount consumed representing the 
 calcium and magnesium. 
 
 If the original water is neutralized with sulphuric acid all the 
 temporary hardness will be converted to permanent hardness. 
 If this latter is then determined, it will represent the total hard- 
 ness of the sample of water. 
 
 Reagents. — The solutions required for the hardness deter- 
 minations are N/20 and N/50 sulphuric acid, N/10 soda reagent, 
 methyl orange indicator and, for some purposes, erythrosine. 
 
 Procedure for Alkalinity. — Measure 200 c.c. of the sample, 
 filtered if necessary, into a porcelain evaporating dish, add two 
 drops of methyl orange indicator and titrate to a faint pink with 
 N/50 sulphuric acid. The end point can best be seen by placing 
 200 c.c. of distilled water in another dish and adding two drops 
 of indicator. This gives a standard color and the first change 
 of the sample being titrated, toward a pink color, can be readily 
 recognized. The number of c.c. of acid used multiplied by five 
 gives the alkalinity in parts of calcium carbonate per million. 
 Save the titrated sample for the determination of total hardness. 
 
 If the soap hardness is over 300, a 100 c.c. sample should be 
 
WATER: ANALYTICAL METHODS 93 
 
 used. In this case multiply the c.c. of acid by 10 to get the 
 alkalinity. 
 
 Notes. — If the water to be tested has been treated with alum, 
 erythrosine indicator must be used as methyl orange is not 
 sufficiently sensitive. For this, measure 100 c.c. of the water 
 into a clear bottle such as is used for the soap test, and add 2.5 
 c.c. of the erythrosine indicator (0.1 gram of the sodium salt in 
 one liter of distilled water), and five c.c. of chloroform neutral 
 to erythrosine. Mix well by shaking and add N/50 sulphuric 
 acid from a burette in small quantities, shaking thoroughly 
 after each addition. The pink color in the water gradually 
 grows lighter until the addition of a drop or two of the acid 
 causes it to disappear entirely. Make a correction for the indi- 
 cator by carrying out a blank determination with distilled water. 
 Multiply the c.c. of acid used by 10 to get the alkalinity in terms 
 of calcium carbonate. 
 
 Procedure for Permanent Hardness. — Measure 200 c.c. of 
 water into an Erlenmeyer flask, boil 10 minutes to expel carbon 
 dioxide, and add 25 c.c. of N/10 soda reagent. For waters 
 with a soap hardness over 300 use a 100 c.c. sample. Boil 
 down to a volume of about 100 c.c, cool to 20 C, rinse into a 
 200 c.c. calibrated flask with cooled, boiled distilled water, and 
 make up to 200 c.c. Mix thoroughly. Filter through a dry 
 filter paper, receiving the filtrate in a 100 c.c. calibrated flask. 
 Discard the first 30 or 40 c.c, and then collect 100 c.c. of the 
 filtrate. Pour into an Erlenmeyer flask, add one drop of methyl 
 orange indicator and titrate with N/20 sulphuric acid. 
 
 Make a blank determination with 200 c.c of distilled water 
 in place of the sample. 
 
 The difference between the amount of acid required by the 
 blank and that required in the determination represents the 
 amount of soda reagent used to precipitate the calcium and mag- 
 nesium. To get the permanent hardness multiply this differ- 
 ence by 25 when a 200 c.c. sample of water is used. 
 
 If a water contains sodium or potassium carbonate, there will 
 not be any permanent hardness, and hence more acid will be 
 
94 AIR, WATER, AND FOOD 
 
 required for the nitrate than corresponds to the amount of 
 soda reagent added. From this excess the amount of sodium 
 carbonate in the water may be determined. Any alkali carbon- 
 ate present would be calculated as temporary hardness by the 
 direct titration; hence it should be calculated to calcium car- 
 bonate and subtracted from the results found by the direct 
 titration. 
 
 Procedure for Total Hardness. — Boil down the neutralized 
 sample obtained at the end of the alkalinity determination to 
 about ioo c.c, add 25 c.c. soda reagent, again boil down to 100 
 c.c, and proceed as in the determination of permanent hardness. 
 The calculations are the same as described there. 
 
 Free Carbonic Acid. — This determination depends on the 
 reaction of sodium carbonate with carbon dioxide to form the 
 bicarbonate, 
 
 Na 2 C0 3 + H 2 + C0 2 -» 2 NaHC0 3 . 
 As soon as all the free carbonic acid has been used up, the next 
 drop of sodium carbonate will color phenolphthalein red. 
 
 Reagents. — These are an N/22 sodium carbonate solution, 
 and phenolphthalein indicator. 
 
 Procedure. — Measure 100 c.c. of the sample into a tall, narrow 
 vessel, preferably a 100 c.c. Nessler tube, add a few drops of 
 phenolphthalein and titrate rapidly with N/22 sodium carbonate 
 solution, stirring gently until a faint but permanent pink color 
 is produced. 
 
 The number of c.c. of N/22 sodium carbonate solution used 
 in titrating 100 c.c. of water, multiplied by 10, gives the parts per 
 million of free carbonic acid as C0 2 . 
 
 Note. — Owing to the ease with which free carbonic acid escapes 
 from water, particularly when present in considerable quantities, 
 it is highly desirable that a special sample should be collected for 
 this determination, which should preferably be made on the 
 ground. If this cannot be done, approximate results from 
 water not high in free carbonic acid may be obtained from 
 samples collected in bottles which are completely filled so as to 
 leave no air space under the stopper. 
 
WATER: ANALYTICAL METHODS 95 
 
 Determination of Sulphates.* — Sulphates can be determined 
 with an accuracy sufficient for most purposes by means of the 
 Jackson Candle Turbidimeter.! The results are determined by 
 the amount of turbidity produced by precipitated barium sul- 
 phate. 
 
 Procedure. — To about ioo c.c. of the water add sufficient 
 dilute hydrochloric acid (about one c.c.) to acidify and then 
 one-half a gram of barium chloride. Shake until dissolved. 
 Pour slowly into the graduated tube of a candle turbidimeter 
 until the image of the flame beneath just disappears. Read the 
 height of the liquid in the turbidimeter tube and obtain from 
 the table in Appendix A the parts per million of sulphates as S0 3 . 
 
 Notes. — Care should be taken to have the solution well 
 stirred before adding to the turbidimeter tube. The tube must 
 not be placed over the flame when empty. Waters containing 
 from 30 to 200 parts per million may be read directly; otherwise 
 the water should either be concentrated or diluted. 
 
 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 effluent water is often neces- 
 sary. This may be readily made by the logwood test.f 
 
 Procedure. — The logwood solution is made as follows : Take 
 two grams of logwood chips and boil one minute in a platinum 
 dish with 50 c.c. of distilled water. Decant the solution and 
 boil again for one minute with 50 c.c. of water. Decant this 
 and similarly boil a third time with 50 c.c. of water. Decant 
 this into a platinum receptacle for use. Take three drops for 
 each test. Kept in platinum, the solution will last for several 
 days at least. 
 
 Test the water as follows: Boil 50 c.c. of the water in a plat- 
 inum dish for a short time to expel carbon dioxide. Add three 
 
 * "Laboratory Notes on Industrial Water Analysis," Ellen H. Richards, 1910. 
 J. I. D. Hinds, /. Am. Chem. Soc, 18, 661 and 22, 269; D. D. Jackson, /. Am. 
 Chem. Soc, 1901, p. 799; Muer, /. Ind. Eng. Chem., 1911, 3, p. 553. 
 
 f For a description of this see references. 
 
 % E. H. Richards, Tech. Quart., 1891, 4, p. 194; A. H. Low, Tech. Quart., 1902, 
 15, P- 3Si. 
 
96 AIR, WATER, AND FOOD 
 
 drops of the logwood solution and continue boiling for a few 
 seconds to develop the color. Decant into a glass flask and 
 cool quickly under the tap (so as not to keep the hot solution 
 too long in the glass). Transfer to a No. 2 beaker and blow in 
 carbon dioxide from the breath by means of a glass tube until 
 there is no further decolorization. Pour the water into a Nessler 
 tube for comparison with standards similarly prepared from a 
 standard alum solution. Allow them to stand several hours 
 before taking the final reading. No wash-water is used at any 
 of the decantations. The test shows one part of aluminum 
 sulphate in 8,000,000 parts of water. 
 
 Notes. — A blank made with distilled water, if not completely 
 decolorized by the C0 2 , will show a tint perceptibly fainter than 
 that produced by one part in 8,000,000 of aluminum sulphate. 
 
 It should be noted that carbon dioxide must be kept absent 
 until the point prescribed. The solution is, therefore, transferred 
 to a beaker in order to keep the flask free from carbon dioxide for 
 the next test. 
 
 The main points are: 
 
 1. Any kind of logwood appears to answer. 
 
 2. The solution is good for several days, at least, if kept in 
 platinum. 
 
 3. The use of platinum instead of glass for boiling the test 
 solution. 
 
 4. The use of carbon dioxide instead of acetic acid. 
 
 Aluminum hydrate, as pointed out in 1893 by the late Profes- 
 sor A. R. Leeds, will produce a tint almost as strong as if it 
 were in solution, but of a distinctly differing tint. 
 
 Low's method of procedure is as follows: First, test the 
 water as above described. If no tint, or none exceeding that 
 of the blank, remains after standing several hours or over night, 
 that is sufficient. If, however, a tint persists, or a colored pre- 
 cipitate settles out, it is necessary to determine if this is due to 
 aluminum hydrate. Pour a sample of the water several times 
 through a double Swedish filter, and finally test the filtrate. If 
 the tint produced is weaker than that given by the unfiltered 
 
WATER: ANALYTICAL METHODS 97 
 
 water, repeat the operation on a fresh portion of the water, 
 using the same filter, and continue repeating with new portions 
 of the water and always using the same filter, until it is apparent 
 that no further diminution of the tint can be effected. 
 
 For a less delicate test in school laboratories where platinum 
 is not available, the following alternative method may be used: 
 
 Dissolve about 0.1 gram pure haematoxylin 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 haematoxylin 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 standard alum solution. The comparison must be 
 made immediately, since the color fades on standing. In this 
 way the presence of one part of aluminum sulphate in five mil- 
 lion can be determined directly in the water and with ease. 
 
 Logwood may be used instead of the haematoxylin, the solu- 
 tion being prepared as above. 
 
 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. 
 
 Procedure. — If the water is colorless, fill a 100 c.c. Nessler 
 tube to the mark, acidify with a few drops of acetic acid, and 
 add from a glass tube one drop of calcium sulphide solution. 
 A black tint to the precipitated sulphur shows the presence of 
 lead. A quantitative estimate may be made by comparison 
 with a series of standards made from a standard lead solution. 
 
 If the water is too highly colored to estimate the lead directly, 
 evaporate three or four liters in a porcelain dish to about 25 c.c, 
 
98 AIR, WATER, AND FOOD 
 
 add 10 ex. of ammonium chloride solution and a considerable 
 excess of strong ammonia. Then add hydrogen sulphide water 
 and allow the dish to stand some hours. Boil the contents of 
 the dish for a few moments to expel the excess of hydrogen 
 sulphide, and filter. The precipitate contains 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 (1 part acid, 
 sp. gr. 1.2, to 5 parts water). Filter and wash; evaporate to 
 10-15 ex., cool, add 5 ex. concentrated sulphuric acid and evap- 
 orate until copious fumes are given off. 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 also alkaline with 
 ammonia. 
 
 If the water contained over 0.25 part iron, wash the lead 
 sulphate into a beaker with alcohol and water, and let it settle 
 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 0.25 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 consider- 
 able quantities of iron.* 
 
 When copper is also present it is detected by the blue color 
 given to the ammoniacal filtrate from the iron precipitation. 
 
 Determination of Phosphates, f — Procedure, — Evaporate 50 
 ex. of the water and three ex. of nitric acid (sp. gr. 1.07) to 
 dryness in a three-inch porcelain dish on the water-bath. Heat 
 the residue in an oven for two hours at the temperature of boiling 
 water. Treat the dry residue with 50 ex. of cold distilled water, 
 
 * Ellms, J. Am. Chem. Soc, 1899, 21, p. 359. 
 
 f Lepierre, Bull. Soc. Chim., 1896, 15, p. 1213; Woodman and Cayvan, /. Am. 
 Chem. Soc, 1901, 23, p. 96; Woodman, ibid., 1902, 24, p. 735. 
 
WATER: ANALYTICAL METHODS 99 
 
 added in several portions and poured into the comparison-tube. 
 It is not necessary to filter the solution. Add four c.c. of ammo- 
 nium molybdate (50 grams per liter) and two c.c. of nitric acid, 
 mix the contents of the tube and compare the color, after three 
 minutes, with standards made by diluting varying quantities 
 of the standard phosphate solution (1 c.c. = 0.0001 gram P2O5) 
 to 50 c.c. with distilled water and adding the reagents as above. 
 Carry out a blank determination on the distilled water used for 
 dilution, especially if it has stood for any length of time in glass 
 vessels. 
 
 Notes. — The method as described will be sufficient for ordi- 
 nary work. If a more exact determination of the phosphate is 
 required, a slight correction should be made in each case. For 
 a table showing these corrections reference may be made to the 
 paper by Woodman and Cayvan previously cited. 
 
 The evaporation and heating with nitric acid is for the purpose 
 of removing silica, which gives with ammonium molybdate a 
 yellow color similar to that given by phosphates. 
 
 The determination of phosphates in a drinking-water is a 
 matter which has not received the attention from water analysts 
 that has been given to the estimation of various other con- 
 stituents. Any one who looks through the literature cannot 
 help noticing how few are the published results of quantitative 
 estimations of the phosphate content of natural waters, apart 
 from mineral waters. Yet this determination, by reason of the 
 conversion of organic phosphorus compounds into phosphates 
 through the process of decay, is one which might reasonably 
 be expected to throw considerable fight on the question of the 
 pollution of natural waters by objectionable material. 
 
 The reasons for this dearth of published data are not far to 
 seek. To be of value the amount of phosphate must be known 
 within rather narrow limits. Qualitative tests are not sufficient. 
 The mere presence of phosphates is by no means definite or 
 even confirmatory evidence of organic pollution. Rocks and 
 minerals containing phosphates are found nearly everywhere, 
 and traces, at times even considerable quantities, may be dis- 
 
IOO AIR, WATER, AND FOOD 
 
 solved, especially by waters rich in carbonic acid. This, how- ' 
 ever, does not constitute a serious objection to the utility of the 
 determination. The same is true of many, if not most, of 
 the constituents upon which reliance is placed in judging of the 
 quality of a water. Unpolluted waters often contain notable 
 amounts of nitrates and chlorides, and a true judgment can be 
 rendered only after comparison with samples from adjacent 
 but unpolluted sources. 
 
 The chief reason, however, has been the lack of an accurate 
 and simple method, sufficiently delicate, and of enough data 
 to work out a standard for comparison. 
 
 This reason can hardly hold true now, for enough work has been 
 done on the colorimetric method to indicate its value as another 
 link (of which we have none too many, anyway) in the chain of 
 circumstantial evidence by which we are often compelled to 
 judge the purity of a water. 
 
 The amount of phosphate and its variation seem to follow 
 the same general line as the other mineral constituents which 
 either accompany the polluting material or are produced by its 
 decay, especially the nitrates and chlorides. It is not, however, 
 so delicate an indicator as these. In general, it may be said 
 that the amount (expressed as P2O5) in an unpolluted water will 
 seldom be over 1.0 part per million. 
 
 Determination of Dissolved Oxygen. — Winkler Method* — 
 The method depends on the absorption of oxygen by man- 
 ganous hydroxide with the formation of manganese dioxide; 
 the liberation of iodine by this last in an acid solution contain- 
 ing potassium iodide; and the titration of the iodine with sodium 
 thiosulphate. The reactions involved can be expressed as 
 follows : 
 
 MnS0 4 + 2 NaOH -> Mn (OH) 2 + Na 2 S0 4 . 
 
 2 Mn(OH) 2 + 2 -> 2 Mn0 2 + 2 H 2 0. 
 
 Mn0 2 + 2 H 2 S0 4 + 2 KI -> MnS0 4 + I 2 + K 2 S0 4 + 2 H 2 0. 
 
 2 Na 2 S 2 3 + I 2 -> 2 Nal + Na 2 S 4 6 . 
 
 * Berichte, 1888, 21, p. 2843; a l so see "Standard Methods of Water Analysis." 
 
WATER: ANALYTICAL METHODS 
 
 IOI 
 
 The method has recently been modified by Hale and Melia* 
 by titrating the iodine in an acetic acid solution in order to 
 avoid difficulties due to the presence of nitrites and nitrates, 
 and this should be followed in testing for putrescibility. 
 
 Collection of Samples. — The samples are collected in glass- 
 stoppered bottles of known capacity, holding about 300 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 bottles are 
 filled at the same time by means of a T tube, owing to varia- 
 tions 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 connected with a larger 
 bottle of at least four times the capacity 
 of the smaller one, and fitted in the same 
 way. From the larger bottle the air is 
 exhausted by the lungs or by an air-pump 
 until it is nearly filled with water. Unless 
 the determination 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 tem- 
 perature of the water at the time of sam- 
 pling should be noted. 
 
 The apparatus which has been used in 
 connection with work in this laboratory 
 for collecting samples at various depths 
 down to 75 feet is shown in outline in 
 Fig. 10. A galvanized-iron can of such 
 size as to hold one of the gallon bottles is weighted with 
 lead and provided with ears at the top for suspending. The 
 
 * /. bid. Eng. Ckem., 1913, 5, p. 976. 
 
 Fig. 10. 
 
102 AIR, WATER, AND FOOD 
 
 bottle, which is securely wired in, is provided with a rubber 
 stopper carrying two brass tubes, one ending just below the 
 stopper and projecting for about 8 or 9 inches above it, the 
 other extending to the bottom of the bottle and connected by 
 heavy rubber tubing with the sample bottle. This is held by 
 brass brackets, which are fastened by means of a wooden cleat 
 to the side of the can. The neck of the bottle is put into the 
 slot in the upper bracket and then it is firmly clamped by the 
 thumb-screw of the lower one. The arrangement of tubes in 
 the sample bottle is obvious. In using the apparatus it is 
 quickly lowered to the desired depth by means of a rope marked 
 off in feet. The water enters the sample bottle and flows through 
 it into the other. When the bubbles cease to rise, indicating 
 that the larger bottle is full, thus replacing the water in the sam- 
 ple bottle a number of times, the apparatus is drawn to the 
 surface. The temperature is read from a thermometer fastened 
 to the tube inside the gallon bottle. 
 
 Reagents. — The reagents needed are solutions of man- 
 ganous sulphate, potassium iodide in sodium hydroxide, potas- 
 sium acetate, N/100 sodium thiosulphate, and starch indicator 
 (see Appendix B). 
 
 Procedure. — Remove the stopper from the 300-c.c. cali- 
 brated bottle, and add two c.c. of manganous sulphate solution 
 with a pipette having a long capillary point reaching to the 
 bottom of the bottle, and in the same way add two c.c. of the 
 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, remove the stopper 
 and add two c.c. of concentrated hydrochloric acid from a 
 pipette in the same manner as before. Replace the stopper, 
 driving out some of the liquid, and shake until the precipitate 
 is dissolved, and the liquid homogeneous. Remove 100 c.c. 
 with a pipette or graduated flask, and titrate with N/100 sodium 
 thiosulphate, using starch as an indicator. Add the starch 
 solution, about two c.c, only after the iodine solution has be- 
 come a light straw color. 
 
WATER: ANALYTICAL METHODS 
 
 103 
 
 To calculate the results proceed as follows: Let 7 equal the 
 volume of the bottle with the stopper inserted and N the number 
 of c.c. of thiosulphate used. One c.c. of N/100 sodium thio- 
 sulphate is equivalent to 0.00008 gram of oxygen. The actual 
 volume of water from which the oxygen was removed is equal 
 to the volume of the bottle minus the four c.c. displaced by the 
 first two reagents added. The liquid displaced by the acid does 
 not need to be allowed for, as it did not contain any oxygen or 
 iodine. The oxygen equivalent to the iodine titrated in the 
 100 c.c. of the solution removed is equal to N X 0.00008. 
 
 The oxygen equivalent to the total iodine liberated is equal to 
 
 N X 0.00008 X 7 
 100 
 
 This is the oxygen present in the original water, which has a 
 volume of (7 — 4), the four c.c. being the part displaced by the 
 solutions added. The oxygen in parts per million is, therefore, 
 equal to 
 
 N X 0.00008 X 7 X 1,000,000 = 0.8 iVT 
 100 X (7 - 4) 7 - 4 ' 
 
 If the sodium thiosulphate solution is not exactly N/100, the 
 correct oxygen equivalent should be substituted in place of the 
 
 value 0.00008. 
 
 QUANTITIES OF DISSOLVED OXYGEN IN PARTS PER MILLION 
 
 BY WEIGHT IN WATER SATURATED WITH AIR AT THE 
 
 TEMPERATURE GIVEN 
 
 Temp. 
 
 c. 
 
 Oxygen. 
 
 Temp. 
 
 c. 
 
 Oxygen. 
 
 Temp. 
 C. 
 
 Oxygen. 
 
 Temp. 
 
 c. 
 
 Oxygen. 
 
 O 
 
 14.70 
 
 8 
 
 11.86 
 
 16 
 
 9-94 
 
 24 
 
 8.51 
 
 I 
 
 14.28 
 
 9 
 
 11.58 
 
 17 
 
 9-75 
 
 25 
 
 8-35 
 
 2 
 
 13-88 
 
 10 
 
 II. 31 
 
 18 
 
 9-56 
 
 26 
 
 8.19 
 
 3 
 
 I3.50 
 
 11 
 
 II.05 
 
 19 
 
 9-37 
 
 27 
 
 8.03 
 
 4 
 
 13-14 
 
 12 
 
 IO.80 
 
 20 
 
 9.19 
 
 28 
 
 7.88 
 
 5 
 
 12.80 
 
 13 
 
 IO.57 
 
 21 
 
 9.01 
 
 29 
 
 7.74 
 
 6 
 
 12.47 
 
 14 
 
 10.35 
 
 22 
 
 8.84 
 
 30 
 
 7.60 
 
 7 
 
 12.16 
 
 15 
 
 10.14 
 
 23 
 
 8.67 
 
 
 
104 AIR, WATER, AND FOOD 
 
 The results of this determination are frequently expressed in 
 per cent of saturation, which is given by the ratio of the oxygen 
 found to that present if the water were completely saturated 
 at the same temperature. The latter figure is given by the 
 preceding table. 
 
 Procedure to be Followed in Putrescibility Tests or with Polluted 
 Waters* — Follow the directions as given above until after the 
 addition of the concentrated hydrochloric acid. Then replace 
 the stopper and shake until all the precipitate is dissolved. 
 Remove the stopper and add from a pipette two c.c. of potassium 
 acetate solution. Mix by pouring into a flask or beaker and 
 back into the bottle. Remove ioo c.c. as before and titrate 
 with N/ioo sodium thiosulphate. 
 
 The addition of the acetate increases the volume of the iodine 
 solution from V (the volume of the bottle) to (V + 2), and this 
 should be substituted in the formula given on p. 103. The oxygen 
 in parts per million will, therefore, be equal to 
 
 0.8 N (V + 2) 
 V-4 
 
 Notes. — If water is collected in the ordinary way and trans- 
 ferred to the apparatus by pouring, there will inevitably be 
 an absorption 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 ioo.f 
 
 Determinations of dissolved oxygen in ponds and streams are 
 best made on the spot, or, at least, the reagents should be added 
 until after the addition of the hydrochloric acid. The very 
 simple apparatus required for the Winkler process can be packed 
 in a small space, and the entire determination requires only a 
 few minutes. The absorption of the oxygen by the manganous 
 
 * See article by Hale and Melia, loc. cit. 
 t Gill, Tech. Quart., 1892, 5, p. 250. 
 
ongressional Reading Room 
 
 
 •2 f|p£ 
 
 r ;-tf**-t * 
 
raooH snibssfl IfinoieeaTgfK 
 
 "vT 
 
WATER: ANALYTICAL METHODS 105 
 
 hydroxide is complete almost at once, and it is unnecessary to 
 allow it to settle for a long time before adding the acid. The 
 titration can be made with a small burette or pipette with 
 accurate results. 
 
 Putrescibility Test.* — There is at the present time no really 
 satisfactory standard putrescibility test. One which seems to 
 have been worked out on logical principles and which has given 
 satisfaction in this laboratory is that proposed by the Royal 
 Sewage Commission. The putrescibility is measured by the 
 absorption of dissolved oxygen under given conditions. A 
 stream water or diluted sewage or effluent, — the water used 
 for dilution furnishing the necessary oxygen, — is tested for 
 dissolved oxygen. A sample is then incubated in a closed bottle 
 for five days at 20 C. and the dissolved oxygen again deter- 
 mined. The difference represents the oxygen absorbed, and 
 should not be greater than 20 parts per million. 
 
 Procedure. — If the water is from a stream or lake, fill com- 
 pletely two 300-c.c. calibrated glass-stoppered bottles. Insert 
 the stoppers, taking care that no air bubbles are enclosed. If a 
 sewage or effluent is being tested, make dilutions with tap water 
 as follows: 
 
 Raw sewage. Dilute 6 c.c. to 600 c.c. 
 Settling tank effluents. Dilute 12 c.c. to 600 c.c. 
 Filter effluents. Dilute 120 c.c. to 600 c.c. 
 Fill two calibrated bottles as just described. 
 
 Make a dissolved oxygen test on one bottle, following the 
 directions as given for putrescibility tests. Set the other bottle 
 in a 20 incubator and let stand for five days. Then determine 
 the dissolved oxygen again. Calculate the results in terms of 
 oxygen absorbed by the original sample of water, sewage or 
 effluent. 
 
 Determination of the Color. — The amount of color is gen- 
 erally determined by direct comparison of the water with some 
 definite standard of color. Various standards have been pro- 
 
 * Eng. Rec, 1913, 68, pp. 315 and 453; Am. J. Pub. Health, 1914, 4, p. 241. 
 
106 AIR, WATER, AND FOOD 
 
 posed, 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. 
 
 The standard in most general use is the platinum standard. 
 The comparisons of the water with the color standards are most 
 readily made in 50-c.c. Nessler tubes. According to this scale, 
 the color of a water is the amount of platinum in parts per 
 million, which, together with enough cobalt to match the tint, 
 must be dissolved in distilled water to produce an equal color. 
 In practice, a standard having a color of 500 is prepared by dis- 
 solving 1.246 grams of potassium platinic chloride (equivalent 
 to 0.5 gram platinum), 1.0 gram of cobalt chloride (equivalent 
 to 0.25 gram cobalt), and 100 c.c. of strong hydrochloric acid in 
 distilled 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 dilut- 
 ing one c.c, two c.c, and three c.c. each to 50 c.c, colors of 10, 
 20, and 30 are obtained. It is claimed that the platinum 
 standards are permanent if protected from the dust, but in this 
 laboratory it has been found necessary to replace them about 
 once a month. 
 
 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 be often 
 detected in this way which would be entirely inappreciable if 
 the water were poured into a tumbler. 
 
 Hot. — Pour into a plain 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. 
 
WATER: ANALYTICAL METHODS 107 
 
 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 derived 
 from clayey soil, but the odor often betrays a contaminated 
 well. Surface-waters 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 "earthy,'' 
 "vegetable," "musty," "mouldy," "disagreeable," and "offen- 
 sive." 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 contamination, and by the trained observer is dis- 
 tinctly distinguishable 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. "Disagree- 
 able " 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 Anabcena, the "fishy" or "cucumber" odor 
 of Synura, etc. The term "offensive" is generally reserved for 
 the sewages. These terms can be taken only as broad illustra- 
 tions of the character of the particular odor, since the odor will 
 very likely be described by different persons 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 
 
108 AIR, WATER, AND FOOD 
 
 inexperienced observers offensive, rotten, fishy, geranium-like, 
 aromatic, in one and the same sample of water. 
 
 The terms generally used to signify the degree of intensity 
 of the odor are "very faint," "faint," "distinct," and "decided." 
 The exact value to be placed upon each of these terms will, as a 
 matter of course, vary with the individual 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. 
 
 Determination of the Turbidity and Sediment. — The sus- 
 pended 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 
 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 solu- 
 tion; usually it consists of fine particles, generally living algae or 
 infusoria. These often collect on the side toward or from the 
 light, and a practiced eye can, not infrequently, recognize their 
 forms. Some of the lower animal forms can also be seen by the 
 naked eye, and the larger Entomostraca 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 slight," 
 "slight," "distinct," and "decided," and the degree of sedi- 
 ment by "very slight," "slight," "considerable," and "heavy." 
 These determinations, again, are of value only to the routine 
 
WATER: ANALYTICAL METHODS 109 
 
 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. 
 
 Sewage Analysis. J — The methods for the analysis of sew- 
 ages and sewage effluents are the same as those described for 
 water. The main difference is in the quantities used for the 
 various determinations. In most cases, this has been noted in 
 connection with the analysis. Great care should also be exer- 
 cised in taking samples from a bottle as the large amount of 
 suspended matter makes it more difficult to obtain a represent- 
 ative portion. Special attention is called to the putrescibility 
 test (p. 105) for effluents, as stability is the main desire in treat- 
 ing a large proportion of sewages. 
 
 Biological Examination. — Since a large number of, if not all, 
 diseases are caused by living organisms, it would seem most 
 desirable in examining a water supply if the specific organisms 
 causing water-borne diseases could be looked for, and, if present, 
 isolated. However, it is quite impossible to do this in the great 
 majority of cases, and so in bacteriological work, just as in 
 chemical analysis, certain indications of the presence of sewage 
 are sought for, and if these indications are positive, the water 
 is condemned. In a bacteriological examination, the most 
 important index of the presence of sewage is rinding B. coli in 
 quantities as great as one in each cubic centimeter. This 
 organism is a normal inhabitant of the intestines of man and 
 the higher animals and is present in large numbers in human 
 and animal excreta. Its presence, therefore, in water shows 
 the presence also of sewage. For a discussion of water bacteri- 
 ology and methods of analysis the reader is referred to another 
 book.§ 
 
 The close relation of the odor to the living flora and fauna of 
 
 * Tech. Quart., 12, 1899, p. 145. 
 t Ibid., p. 283. 
 
 X See Fowler "Sewage Works Analyses," John Wiley & Sons, 1902. 
 § Prescott and Winslow, "Elements of Water Bacteriology," 3rd edition, 
 John Wiley & Sons, 19 13. 
 
HO AIR, WATER, AND FOOD 
 
 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 make no pretensions to a knowledge of cryptogamic 
 botany or of zoology. Therefore, a microscope and a concen- 
 tration apparatus should be in every water-laboratory. A full 
 description will be found elsewhere.* 
 
 * Whipple, "The Microscopy of Drinking Water," 3rd edition, John Wiley 
 & Sons, 19 14. 
 
CHAPTER VII 
 
 FOOD IN RELATION TO HUMAN LIFE: COMPOSITION, 
 SOURCES, DIETARIES 
 
 Life itself is conditioned on the food-supply. Wholesome 
 food is a necessity for productive life. Man can and does exist 
 on very unsuitable, even more or less poisonous, food, but it is 
 merely existence 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 diges- 
 tive organs for three hours. With the products of the world ex- 
 posed in our markets, the restraints of a restricted choice, as well 
 as inherited 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 is now even more necessary that an elemen- 
 tary knowledge of the proximate composition and food value of 
 the more common edible substances should be recognized as an 
 essential part of education. 
 
 Food: Definition and Uses. — 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 elements 
 which they need for life and growth. Only such available sub- 
 stances can be called food, no matter what their chemical compo- 
 
112 AIR, WATER, AND FOOD 
 
 sition may be. Soft coal contains carbon and hydrogen and is 
 food for the furnace, but is not available for the animal body. 
 
 This food which is taken into the body is used in various ways. 
 It forms and builds up new tissues, besides repairing and making 
 good the waste of tissues due to bodily activity; it is stored up in 
 the body to meet a future demand; it supplies the needed heat 
 by the transformation of its stored up or potential energy into 
 the muscular energy required by the body; it may be used to 
 protect the tissues of the body from being themselves consumed 
 as food. 
 
 Composition of Food. — We determine what chemical elements 
 enter into the composition of the body by an analysis of the vari- 
 ous 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 furnish 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 118), and that ten of them form nine- tenths of 
 the food of the world. 
 
 The composition of food, as shown by chemical analysis, is 
 not, however, the only factor that must be known to determine its 
 value. The digestibility of the material must be taken into ac- 
 count as well. "We live not upon what we eat, but upon what 
 we digest." It is more important to know the amount of availa- 
 ble nutrients than the amount of total nutrients. 
 
 Food Principles. — While the foodstuffs present great variety, 
 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 substances 
 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. 
 
FOOD IN RELATION TO HUMAN LIFE 1 13 
 
 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 dissolved 
 to be at once assimilated. Others, as gluten and similar vege- 
 table products, undergo a greater change; while still others, 
 as gelatine, have a less profound but marked effect in protecting 
 the tissues from waste. 
 
 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 protoplasmic 
 proteid, presumably' the greater its food value, since each cleav- 
 age, 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 students 
 will find a fruitful field of research along these lines of inves- 
 tigation. 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 combination 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 quan- 
 tities necessary for the daily efficiency, except in the very few 
 instances of nearly pure substances, as white of egg. It is 
 evident, also, that the manner of preparation and the kind of 
 mixtures used in food will affect most profoundly so unstable 
 and complex a class of substances. One thing is certain, that 
 the body cannot take nitrogen from that which does not contain 
 it. Therefore, a certain quantity of highly nitrogenous food 
 should form a portion of the daily supply. It is usually held 
 
114 AIR, WATER, AND FOOD 
 
 that the body seems to be sufficiently nourished when the food 
 contains an amount of digestible proteid equivalent to about ioo 
 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 organic nature, 
 as creatin, urea, and uric acid, which have deleterious effects 
 when accumulated in the system. A deficiency of nitrogen is 
 made good, to a limited extent, by the protective agency of the 
 other foodstuffs which offer themselves 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. Whatever 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 
 nearly all natural food-substances do contain it, and that it 
 appears to be more economical of human energy to take it from 
 these foods than to manufacture it from the proteids and carbo- 
 hydrates, we may safely assume fat to be an essential of the 
 human dietary. 
 
FOOD IN RELATION TO HUMAN LIFE 115 
 
 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 food- 
 stuffs, the carbohydrates, characteristic of the vegetable king- 
 dom — a class which in the final decomposition, yields 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 probably 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 pre- 
 vents 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 especially 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 mere. 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 evidence 
 to show that power of digesting vegetable foods indicates a 
 general well-being of body conducive to long life. A ready 
 adaptation renders possible the changes of habitat required by 
 civilization. Unless one is to be confined to a narrow 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. 
 
Il6 AIR, WATER, AND FOOD 
 
 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 sulphur 
 and phosphorus. Potassium, found in barley, is a constant 
 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. 
 
 To sum up briefly, then, we may say that the protein or nitrog- 
 enous portion of the food forms tissue, such as muscle, sinew and 
 fat, and furnishes energy in the form of heat and muscular 
 strength; the fats build up fatty tissue, but not muscle, and 
 supply heat; the carbohydrates are changed into fat and supply 
 heat. Another important use of the nutrients is to protect 
 each other from being used in the body. The carbohydrates, 
 especially, in this way protect the protein, including muscle, 
 etc., from consumption. 
 
 Change in Composition Due to Cooking. — The composition of 
 cooked foods is in general not the same as the raw material on ac- 
 count principally of chemical and physical changes brought about 
 by the heat employed in the cooking process. The total nutri- 
 ents, calculated on a water-free basis, may be practically the 
 same, but the structure is often quite different. 
 
 Starch is hydrolyzed and rendered soluble by heating in the 
 presence of moisture, and at higher temperatures it may be 
 converted into the brown, soluble dextrin. The sugars are 
 changed, being, in the case of sucrose, partly converted into 
 other forms, such as invert sugar, by the heating, with the help 
 of the organic acids present in many foods. Some of the proteids 
 tend to become less soluble through heating and at higher tem- 
 peratures may be even partly decomposed with possible loss of 
 food value. 
 
FOOD IN RELATION TO HUMAN LIFE 1 17 
 
 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 is the amount of heat required to raise the tempera- 
 ture of one gram of water one degree centigrade. A gram of fat, 
 as actually digested and oxidized in the body, affords enough 
 heat to raise the temperature of about 9000 grams of water one 
 degree. In like manner a gram of protein has an energy-pro- 
 ducing power expressed in calories of about 4000, and for carbo- 
 hydrates the average value is also 4000. 
 
 Allowance is made in these figures for the fact that to digest 
 completely any part of our food results in a decrease of the 
 amount of energy to be derived from it, and this affects the 
 protein more than it does the other two. It is probably true 
 that under favorable conditions the fat and carbohydrates 
 can be completely utilized in the body and consequently their 
 energy-producing power can be correctly estimated from their 
 heat-producing power outside the body. In the case of pro- 
 tein, however, the digestion within the body is never so com- 
 plete as to furnish all the energy that would be obtained by a 
 complete combustion of these nitrogenous materials outside of 
 the body. 
 
 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. 
 
 Nutritive Ratio. — The requisite number of calories must, how- 
 ever, 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 available for the balance of nutrition. In carrying on its 
 multifarious 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 fur- 
 nished by fat or starch, these substances alone will not suffice for 
 
n8 
 
 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. 
 
 Butter 
 
 Per cent. 
 
 Per cent. 
 11. 
 
 Per cent. 
 
 1.0 
 
 Per cent. 
 
 85.0 
 
 100 . 00 
 
 83.0 
 
 80.3 to 94.1 
 
 70.7 to 94.5 
 
 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 
 
 1.1 to7-5 
 
 16.6 
 
 
 
 
 
 Suet 
 
 
 
 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) 
 
 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 invalids' foods. 
 
 Macaroni 
 
 Oats 
 
 Peanuts 
 
 Peas (dried) 
 
 Pop-corn 
 
 Rice 
 
 Rye flour 
 
 Sugar (granulated) 
 
 Wheat (entire) flour 
 
 Wheat flour (white bakers'). 
 
 Wheat (shredded) 
 
 Zwieback 
 
 18.4 
 
 316 
 
 1.5 to 10.3 
 
 11. o to 25.8 
 
 28.9 
 
 2.1 
 22.2 
 
 9-5 
 28.8 
 
 59.4 
 359 
 
 03 
 
 12.5 to 13.4 
 
 47- 1 to S0.2 
 
 26.8 to 33.8 
 
 S.i to 7-6 
 
 16.4 to 25.7 
 
 45.8 to 63.2 
 
 10.7 
 
 59-8 
 
 
 29-3 
 
 46.5 
 
 17. 1 
 
 27.9 
 
 40.4 
 
 
 III. Fuel Value 1500-2000 Calories per Pound 
 
 11. 7 
 
 4.5 to 28. 
 
 245 
 
 9.8 to 12.9 
 
 9.6to 15.5 
 
 19.9 
 
 4.0 
 
 42.7 to 57-2 
 
 8.8 to 17.9 
 10. o 
 
 6.8 
 
 38.3 
 
 136 
 
 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 
 11. 9 to 136 
 
 6.4 to 13. 1 
 10. 1 to 133 
 
 7.2 to 10.7 
 S.o 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 11. 6 
 
 10.7 
 130 
 84.2 
 
 10.2 to 21.9 
 2 . o to 22 . 5 
 7.9 to 16.6 
 
 16.5 
 
 195 
 
 20.4 to 28.0 
 
 10.7 
 
 5-9 to 11. 3 
 4-9to 8.8 
 
 12.2 to 14.6 
 
 10.3 to 14.9 
 9.6 to 11. 4 
 8.6 to 11. 7 
 
 0.7 to 1.5 
 
 1.4 to 3.1 
 
 9.0 
 
 22.3 to 32.5 
 
 1.0 to5.3 
 
 8.8 
 
 36.8 
 
 0.1 
 
 245 to 39-9 
 
 0.3 to 10.9 
 
 0.0 to 4.9 
 
 7-3 
 
 29.1 
 
 0.8 to 1.3 
 
 5.o 
 
 0.1 to 0.7 
 
 0.2 to 1.3 
 
 1.5 to 2.1 
 
 1.9 tO 2.0 
 
 1.3 to 1.6 
 
 8.1 to 11. 3 
 
 IV. Fuel Value 1000-15000 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 
 
 150 
 10. o 
 
 8.6 tc 
 
 47-4 
 
 35-3 
 
 28.4 to 48.0 
 
 13.8 
 
 11. 6 to 25.0 
 
 40.1 to 43-6 
 
 38.0 to 44-9 
 
 27.7 
 
 54 
 
 4 
 
 44 
 
 9 
 
 19 
 
 
 
 13 
 
 I 
 
 44 
 
 9 
 
 53 
 
 6 
 
 32 
 
 5 
 
 1 . 2 to 2 . 5 
 
 92 
 6.5 to 10. 1 
 
 1-9 
 
 2.6tO 5-7 
 
 13.7 to 14.5 
 11. 4 to 12.9 
 
 6.7 
 
 4-8 
 
 4-4 
 
 1.8 
 
 2.3 
 10.9 
 237 
 16.3 
 
 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* 
 
 66 . 9 to 89 . 4 
 
 67.2 to 78.4* 
 66.5* 
 18.5 
 
 58.0 to 67.4* 
 
 78.7 
 75-4 to 81.9* 
 77.6 to 80.2* 
 
 100 
 
 69.5 to 770* 
 
 70.3 to 755 
 
 75.0 to 79-7* 
 
 72.1 to 74-2 
 
 48.6 to 86.91 
 
 53- 1 
 40.3 to 54-3 
 
 70.6 
 68.3 to 83.1 
 
 60.2 
 32.1 
 
 39-2 
 62.2 
 68.5 
 33-3 
 
 * One Calorie equals iooo calories. 
 
FOOD IN RELATION TO HUMAN LIFE 
 
 119 
 
 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. 
 
 
 Per cent. 
 
 8.5 
 
 12.8 
 
 18.0 to 42.7 
 
 Per cent. 
 62.5 
 540 
 
 38.3 to 53-7 
 74.o 
 65.5 
 19.2 
 
 59.9 to 69.2 
 
 52.4 
 
 45.oto 51.2 
 54-6 to 58.2 
 
 52.0 to 71.6 
 
 32.4 to 69.2 
 
 41. 1 to 44-7 
 
 48.5 to 55-7 
 
 Per cent. 
 19.2 
 16. s 
 
 11. 5 to 16.0 
 2.5 
 
 11. 9 
 20.5 
 
 18. 1 to 21.4 
 1-4 
 
 12.6 to 15.0 
 18.6 to 20.2 
 
 2.8 to 4.2 
 7 . 8 to 20 . 2 
 15.8 to 16.8 
 
 14.2 to 16.9 
 
 Per cent 
 9-2 
 16. 1 
 6.9 to 21.5 
 18.5 
 93 
 8.8 
 
 7.8 to 14.2 
 21.0 
 
 6.6 to 9.5 
 5.6 to 98 
 
 2.3 to 4.8 
 0.7 to 15.3 
 
 5.9 to 25.5 
 
 9.4 to 12.8 
 
 Per cent. 
 
 
 
 
 
 
 
 Eggs 
 
 11. 2 
 
 444 
 0.5 to 11. 3 
 
 19.0 
 23-8 to 35-1 
 11. 7 to 16.9 
 
 
 
 
 
 
 Olives 
 
 35 
 
 Salmon (canned) 
 
 
 
 
 
 9.2 to 55-3 
 17. 1 to 32.4 
 15.7 to 25.4 
 
 
 
 
 Veal (breast) 
 
 
 VI. Fuel Value 400-500 Calories per Pound 
 
 Beans (canned red kidney) , 
 
 Calf's-foot jelly. . . 
 
 Salt cod (boneless) 
 
 Succotash (canned) 
 
 Sweet potatoes 
 
 1.6 
 
 72.7 
 
 77.6 
 
 54.8 
 
 71.4 to 79-9 
 
 55.2 
 
 7.0 
 4.3 
 27.7 
 
 2.9 to 4.4 
 1-4 
 
 0.7 to 1.7 
 0.6 
 
 VII. Fuel Value 300-400 Calories per Pound 
 
 Bananas 
 
 Butter beans. 
 Fish (fresh).. 
 
 Grapes 
 
 Hash 
 
 Milk 
 
 Potatoes 
 
 3S.o 
 
 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 
 11. 9 to 12. 
 1.0 
 
 6.0 
 3.3 
 
 1.8 
 
 0.4 
 0.3 
 1.8 to5-9 
 1.2 
 1.9 
 4.0 
 
 VIII. Fuel Value 200-300 Calories per Pound 
 
 Apples 
 
 25.0 
 
 
 
 
 
 
 
 Oysters (solid) 
 
 
 
 
 Pears 
 
 10. 
 
 63.3 
 
 44-6 to 52.4 
 87.6 to 89.5 
 
 78.9 
 82.2 to 92.4 
 
 66.4 
 
 76.2 
 
 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 
 
 1.1 to 1.8 
 
 0.4 to 0.9 
 
 0.3 
 
 0.5 to 1.8 
 
 0.4 
 0.4 
 
 18.5 
 17-4 
 
 14.9 to 22.4 
 21.9 
 
 143 
 14.6 
 
 14.4 
 9-4 
 
 5-0 
 147 
 
 10.8 
 
 9-3 to 10.9 
 
 8.9 
 1.5 to 6.2 
 10.8 
 12.7 
 
 IX. Fuel Value 100-200 Calories per Pound 
 
 Beets 
 
 20.0 
 15.0 
 20.0 
 61.0 
 30.0 
 27.0 
 
 
 
 Green corn 
 
 
 
 
 Spinach 
 
 
 Squash 
 
 50.0 
 
 Tomatoes (canned) 
 
 70.0 
 
 77.7 
 70.6 
 29.4 
 
 62. 5 
 634 
 
 91.0 to 92.8 
 91.6 to 92.8 
 
 44-2 
 92.5 to 97-9 
 
 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 
 
 0.1 
 
 0.2 
 
 0.2 
 
 0.4 
 
 0.5 
 
 0.1 
 0.2 to 0.8 
 0.2 to 0.5 
 
 X. Fuel Value io-ioo 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 
 
 1.8 
 1.7 to 2.6 
 09 
 0.7 
 0.2 
 
 0.2 
 
 0.0 tO 0.2 
 O.I 
 0.2 
 O.I 
 
 7-7 
 4-8 
 7-4 
 7-7 
 59 
 8.5 
 
 0.6 to57 
 3-1 to34 
 
 4-5 
 1.4 to 8.1 
 
 33 
 0.1 to 0.3 
 
 2.6 
 2.6 
 
 2.7 
 
120 AIR, WATER, AND FOOD 
 
 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 1 to 5. 
 
 The preceding table of one hundred common food-materials 
 is arranged in the order of calorific or energy-giving power, but 
 in considering the food value of any one substance its nitro- 
 gen content must also be considered, and such combinations 
 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 differing con- 
 ditions of soil moisture, fertilization in the case of plants, and 
 of fatness or leanness in animals, of method of preparation 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 con- 
 tains 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 nutrition. 
 
 The great variation in the proportion of water leads to many 
 surprises, and the amount of unedible material is to be con- 
 sidered. The uneducated provider buys oysters under the 
 impression that he is furnishing food of high value, and does 
 not distinguish 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 espe- 
 cially 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: 
 
FOOD IN RELATION TO HUMAN LIFE 
 
 121 
 
 Approximate amounts 
 required daily by 
 
 Nitrogenous, 
 grams. 
 
 Fats, 
 grams. 
 
 Carbohydrates, 
 grams. 
 
 Calories. 
 
 Child of 6-9 
 
 62 
 
 78 
 
 IOO 
 
 100 
 
 125 
 
 45 
 45 
 75 
 90 
 
 125 
 
 200 
 
 281 
 380 
 
 450 
 
 500 
 
 1593 
 1890 
 2665 
 3092 
 3725 
 
 Child of 9—14 
 
 Adult at rest 
 
 Adult at moderate work . . 
 Adult at hard work 
 
 (In feeding experiments from 10 to 20 per cent more must be allowed for waste 
 and indigestibility.) 
 
 From the table on page 118 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 per cent 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 utilization, so that 
 other means must be restored 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 com- 
 bination. 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 pur- 
 chased, 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. 
 
122 AIR, WATER, AND FOOD 
 
 The waste of fats is less in proportion 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 voluntary, 
 not, like air, a necessity beyond control, and that the 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 effi- 
 ciency for years or for all his life. 
 
 It is not nearly so difficult to acquire a working knowledge 
 of food values as of whist or golf, so that on entering a restaurant 
 a suitable menu may be made up within one's allowance. It 
 is only necessary to correct prevailing impressions and rein- 
 force one's experience. 
 
 Figs, dates, raisins and prunes are apt to be regarded as 
 luxuries instead of as rich food-substances of a most digestible 
 kind when freed from skin and seed. Nuts are a much neg- 
 lected form of wholesome food, admirably suited to a winter 
 table from their richness in fat, and also furnishing 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 concentration. The some- 
 what 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. 
 
 The foods which furnish the greatest nutrition for the least 
 money are such materials as corn meal, wheat flour, milk, 
 
FOOD IN RELATION TO HUMAN LIFE 1 23 
 
 beans, cheese and sugar. The expensive cuts of meat, high- 
 priced breakfast cereals and the like, add but little to the nu- 
 tritive value but greatly increase the cost of living. 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 sweet breads, grape-fruit, etc., might cost a 
 dollar. Incorrect ideas in regard to food values, and prejudice 
 inherited or acquired against certain foods, have too often 
 resulted in excluding wholesome and nutritious articles from 
 the dietary and decreasing thereby the efficiency of the human 
 machine. 
 
CHAPTER VIII 
 
 THE PROBLEM OF SATE FOOD. ADULTERATION AND 
 SOPHISTICATION 
 
 Adulteration grows largely, if not almost entirely, from ex- 
 cessive competition. Nearly every article of common food has 
 been found at one time or another to be adulterated, yet manu- 
 facturers testify that they willingly would stop this addition of 
 foreign material if they could be sure that their competitors 
 would stop also. Other causes there are also: demands for 
 goods out of season; for perishable products which must come 
 many miles; the failure of the supply of a given substance to 
 meet a continuing demand; all of these lead to adulteration, 
 imitation and substitution. 
 
 To many people otherwise intelligent, the term adulterated food 
 is synonymous with poisoned food. With others, thanks to 
 alarming newspaper articles, not wholly disinterested, the general 
 impression is far beyond the reality. It is not necessary to 
 use poisonous or even deleterious material; it needs only to mix 
 with the food material some substance cheaper but harmless, 
 to make some change in the outward appearance of the article 
 so that people shall not recognize the familiar substance, and 
 then to herald far and wide the discovery of a new process by 
 which the food value is greatly enhanced. "Things are not 
 what they seem" is nowhere more true than in the case of 
 foods. 
 
 Definition of Adulteration. — To adulterate is "to debase," "to 
 make impure by an admixture of baser materials." The word 
 "adulterated " refers to any food to which any foreign substance, 
 not a proper portion of the food, has been added. It does not 
 matter whether the added material is of greater value than the 
 food itself. The addition of coffee to cereal or substitute coffees, 
 
 124 
 
ADULTERATION AND SOPHISTICATION 125 
 
 is properly held to be an adulteration. Deterioration should not 
 be mistaken for adulteration. People who are not wholly familiar 
 with the appearance of a food or the chemical and physical 
 changes which it may undergo, think that if it does not taste just 
 right or look just right that it must be adulterated. Appearance 
 has slight relation to the purity of the article in these days of 
 paint, polish and powder. 
 
 Some forms of adulteration are more properly described under 
 the head of misbranding, that is, referring to foods incorrectly de- 
 scribed by the label. While the significance is not exactly the 
 same as that of the word adulterated, yet the two may sometimes 
 be applied to the same product. For instance, the addition of 
 starch to sausage to conceal the use of excessive amounts of water 
 and of fat constitutes an adulteration, which would not be the case 
 if the article were properly branded to show the presence of the 
 added "filler." 
 
 To adulterate the coin of the realm or the liquor of the bar with 
 a baser metal or an imitation whisky is a heinous offence. So is 
 the mixture of milk with the baser article, water, which thereby 
 lowers its food value. But the "wretched sophistry" which ob- 
 scures the nature of things on a package of prepared food mis- 
 leads more persons and inflicts more injury upon the community 
 than the other, yet goes unrebuked. The most barefaced asser- 
 tions are printed in magazines, and "pure-food shows" only whet 
 the appetite for something new. 
 
 Legal Definition of Adulteration and Misbranding. — In the 
 Federal Pure Food Law, commonly known as the Food and Drugs 
 Act of June 30, 1906, adulteration and misbranding are thus 
 defined : 
 
 Sec. 7. That for the purposes of this Act an article shall be 
 deemed to be adulterated: 
 
 In the case of food: 
 
 First. If any substance has been mixed and packed with it so , 
 as to reduce or lower or injuriously affect its quality or strength. 
 
 Second. If any substance has been substituted wholly or 
 in part for the article. 
 
126 AIR, WATER, AND FOOD 
 
 Third. If any valuable constituent of the article has been 
 wholly or in part abstracted. 
 
 Fourth. If it be mixed, colored, powdered, coated, or stained 
 in a manner whereby damage or inferiority is concealed. 
 
 Fifth. If it contains any added poisonous or other added dele- 
 terious ingredient which may render such articles injurious to 
 health : Provided, That when in the preparation of food products 
 for shipment they are preserved by any external application ap- 
 plied in such manner that the preservative is necessarily removed 
 mechanically, or by maceration in water, or otherwise, and direc- 
 tions for the removal of said preservative shall be printed on the 
 covering or the package, the provisions of this Act shall be con- 
 strued as applying only when said products are ready for con- 
 sumption. 
 
 Sixth. If it consists in whole or in part of a filthy, decomposed, 
 •or putrid animal or vegetable substance, or any portion of an 
 animal unfit for food, whether manufactured or not, or if it is the 
 product of a diseased animal, or one that has died otherwise than 
 by slaughter. 
 
 Sec. 8. That the term "misbranded," as used herein, shall 
 apply to all drugs, or articles of food, or articles which enter into 
 the composition of food, the package or label of which shall bear 
 any statement, design, or device regarding such article, or the 
 ingredients or substances contained therein which shall be false or 
 misleading in any particular, and to any food or drug product 
 which is falsely branded as to the State, Territory, or country in 
 which it is manufactured or produced. 
 
 That for the purposes of this Act an article shall also be deemed 
 to be misbranded : 
 
 In the case of food : 
 
 First. If it be an imitation of or offered for sale under the dis- 
 tinctive name of another article. 
 
 Second. If it be labeled or branded so as to deceive or mislead 
 the purchaser, or purport to be a foreign product when not so, 
 or if the contents of the package as originally put up shall have 
 been removed, in whole or in part, and other contents shall have 
 
ADULTERATION AND SOPHISTICATION 127 
 
 been placed in such package, or if it fail to bear a statement on 
 the label of the quantity or proportion of any morphine, opium, 
 cocaine, heroin, alpha or beta eucaine, chloroform, cannabis 
 indica, chloral hydrate, or acetanilide, or any derivative or prep- 
 aration of any such substances contained therein. 
 
 Third. If in package form, and the contents are stated in terms 
 of weight or measure, they are not plainly and correctly stated on 
 the outside of the package. 
 
 Fourth. If the package containing it or its label shall bear any 
 statement, design, or device regarding the ingredients or the sub- 
 stances contained therein, which statement, design, or device shall 
 be false or misleading in any particular : Provided, That an article 
 of food which does not contain any added poisonous or deleterious 
 ingredients shall not be deemed to be adulterated or misbranded 
 in the following cases : 
 
 First. In the case of mixtures or compounds which may be 
 now or from time to time hereafter known as articles of food, 
 under their own distinctive names, and not an imitation of or 
 offered for sale under the distinctive name of another article, if 
 the name be accompanied on the same label or brand with a state- 
 ment of the place where said article has been manufactured or 
 produced. 
 
 Second. In the case of articles labeled, branded, or tagged 
 so as to plainly indicate that they are compounds, imitations, 
 or blends, and the word "compound," " imitation," or " blend," 
 as the case may be, is plainly stated on the package in which 
 it is offered for sale: Provided, That the term blend as used 
 herein shall be construed to mean a mixture of like substances, 
 not excluding harmless coloring or flavoring ingredients used 
 for the purpose of coloring and flavoring only: And provided 
 further, That nothing in this act shall be construed as requir- 
 ing or compelling proprietors or manufacturers of proprietary 
 foods which contain no unwholesome added ingredient to dis- 
 close their trade formulas, except in so far as the provisions of 
 this act may require to secure freedom from adulteration or 
 misbranding. 
 
128 AIR, WATER, AND FOOD 
 
 Extent of Adulteration. — In any discussion of the extent to 
 which adulterated foods are sold it must be borne in mind that 
 the adulterated articles make up only a relatively small propor- 
 tion of the food that actually passes over the counter. Flour, for 
 example, is seldom adulterated; pepper, mustard and vanilla ex- 
 tract often are. For one pound of these substances sold, iooo 
 pounds or more of flour go out from the store. Figures given in 
 official reports of food inspection do not represent the case exactly, 
 because the inspectors are trained men, and purchase samples of 
 those lines of goods which experience has shown them to be most 
 likely to be adulterated. Brands of foods which they have reason 
 to believe are pure they do not sample. Estimated on the total 
 quantity sold, it is doubtful if more than 5 to 10 per cent of the 
 food sold is adulterated in any way, and these figures would un- 
 doubtedly be much too high for those states in which there is a 
 well-enforced system of food inspection. 
 
 Character of Adulteration. — Much of the present propaganda 
 in the interests of pure food and the movement for the protection 
 of the consumer can be summed up in three words: "An Honest 
 Label." In many cases an accurate and true statement of the 
 contents of the can or package is the only protection needed by 
 the consumer, and is fully as efficient as well as much cheaper 
 than prosecutions or restrictive measures. Many of the terms 
 used on food packages deceive only the ignorant purchaser. 
 "Strictly pure" is a well-understood trade term, with a meaning 
 known to the initiated; the words "Home-Made" may cover 
 some of the most highly developed products of synthetic organic 
 chemistry. 
 
 The cases in which the adulteration is of a character dele- 
 terious to health are fortunately few. 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 foods 
 to stand in the opened tins. The liking for bright green pickles 
 and peas leads to coloration by copper salts. 
 
 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 
 
ADULTERATION AND SOPHISTICATION 129 
 
 the quality of many foods. A baking-powder or a spice which is 
 honestly made to-day may next week pass into the hands of un- 
 scrupulous 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 cus- 
 tomer that the packages came from the same barrel, and yet each 
 might satisfy his individual preference. 
 
 Names that have passed down from a former generation as 
 being above reproach are now found to cover adulterated goods. 
 The trademark has passed into other and less scrupulous hands, 
 and the new owners do not hesitate to trade upon the reputation 
 earned by their predecessors. There are, however, several phases 
 of the subject that should be briefly mentioned. 
 
 Breakfast Foods. — The craving for something new to stimulate 
 a jaded appetite already spoiled by endless variety and bad com- 
 binations has led to the manufacture of a cereal preparation for 
 nearly every day in the year, regarding some of which the state- 
 ment is made that they are "predigested." No better commen- 
 tary on the laziness or wilful ignorance of American providers 
 could be made than this. Little do the people know about wheat 
 or cooking if they suppose that grain can be changed by manipu- 
 lation 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 remains 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 pur- 
 pose were they viewed in the light of common sense. It is not 
 always best to have food which is too easily digested. 
 
 A predigested food is quickly absorbed into the circulation, 
 and hence a small quantity causes a sensation of fulness and satis- 
 faction, which, however, soon passes away and a faintness results. 
 
13© AIR, WATER, AND FOOD 
 
 This is especially true of the sugars and dextrins. Frequent 
 meals should go with easily absorbed foods. The rapid digestion 
 is the cause of much pernicious eating of sweets between meals, 
 which satisfies the appetite for the time being and prevents sub- . 
 stantial quantities of other foods being taken at the time they 
 are offered. 
 
 From a study of analyses of a large number of foods the fol- 
 lowing conclusions are drawn by F. W. Robison: * 
 
 i. The breakfast foods are legitimate and valuable foods. 
 
 2. Predigestion has been carried on in the majority of them 
 to a limited degree only. 
 
 3. The price for which they are sold is as a rule excessive and 
 not in keeping with their nutritive values. 
 
 4. They contain, as a rule, considerable fibre which, while 
 probably rendering them less digestible, at the same time, may 
 render them more wholesome to the average person. 
 
 5. The claims made for many of them are not warranted by 
 the facts. 
 
 6. The claim that they are far more nutritious than the wheat 
 and grains from which they are made is not substantiated. 
 
 7. They are palatable as a rule and pleasing to the eye. 
 
 8. The digestibility of these products as compared with highly 
 milled goods, while probably favorable to the latter, does not give 
 due credit to the former, because of the healthful influence of the 
 fibre and mineral matter in the breakfast foods. 
 
 9. Rolled oats or oatmeal as a source of protein and of fuel is 
 ahead of the wheat preparations, excepting of course the special 
 gluten foods, which are manifestly in a different class. 
 
 In general, the cost of these foods is low if they are considered 
 merely as confections to please the taste, but they are expensive 
 foods regarded as substitutes for the ordinary cereal products. 
 
 This is well shown in the following table in which the fuel 
 value of breakfast foods and other common food products ob- 
 tained for a given sum is graphically compared. 
 
 * Mich. Agr. Expt. Sta., Bull., 211 (1904). 
 
ADULTERATION AND SOPHISTICATION 
 
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132 AIR, WATER, AND FOOD 
 
 Colors and Preservatives in Food. — For many years such sub- 
 stances as alcohol, vinegar, sugar, salt, and the like, have been 
 used to preserve food. Such materials are commonly held to be 
 harmless to persons of sound digestion if used in moderate 
 amounts. Within recent years, however, there has been a con- 
 stantly increasing tendency toward the use in food products of 
 such powerful antiseptics as formaldehyde, salicylic and benzoic 
 acids and their salts, and boric acid. An important distinction 
 to be borne in mind between this class of preservatives and those 
 first named is that the former when used in food in quantity suffi- 
 cient to preserve it make their presence known to the consumer 
 by either their taste or odor. With the chemical preservatives, 
 however, an intimation of their presence is conveyed to the con- 
 sumer only by a statement on the label. It is the general feeling 
 among those engaged, in the enforcement of the food laws that 
 the common use of these preservatives should be forbidden, or 
 that they should be allowed only under certain definite restric- 
 tions. The question is not one of their possible harmful effect 
 only, although it cannot be successfully denied that their unre- 
 stricted use would lead to grave danger to health, especially in the 
 case of invalids and children, or those with various degrees of 
 digestive efficiency. It seems reasonable to infer that the proc- 
 esses of digestion, being largely the result of bacterial and 
 enzymic action, will be retarded or interfered with to a greater 
 or less extent by substances which inhibit bacterial action in 
 food. 
 
 There is, however, another reason for objecting to the use of 
 chemical preservatives. By their use much food that is unwhole- 
 some and unfit for consumption can be, and is, placed upon the 
 market with no warning to the consumer. "The man who adds 
 formaldehyde to his milk takes down the danger signal, but does 
 not remove the danger." 
 
 Similarly, objections can be made to the use of coal-tar colors 
 in foods. There are hundreds of food packages which would 
 never leave the grocers' shelves were it not for the fact that by 
 the use of artificial color their true composition and the actual 
 
ADULTERATION AND SOPHISTICATION 133 
 
 nature of the materials from which they are made is hidden. 
 Apart from any question as to the harmfulness of these dyes 
 there is ample reason for their use being strictly regulated by 
 official action, in that their use except under such supervision 
 allows the manufacturer to sell inferior articles under the appear- 
 ance of standard foods; it permits the customer to be misled as 
 to the strength and purity of the product that he buys; the age 
 and past history of the product may be made a sealed book; 
 finally, by the use of coloring, an unwholesome and improper 
 food may be put upon the market. 
 
 Summary. — The chief dangers in food are from wrong pro- 
 portions of proteid, fat, and carbohydrates, from fermentable 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 ves- 
 sels, to a favorable medium for the growth of pathogenic germs, 
 from unsuitable food scientifically disguised. 
 
 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. Glu- 
 cose is even more easily absorbed than cane-sugar. These are 
 cases of frauds on the pockets, but possibly blessings in disguise 
 for the stomachs. When any community is so ignorant as to per- 
 mit of such glaring cases of adulteration as coal-tar dyes in food, 
 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. 
 
 This knowledge is now easily obtained through the city, state 
 and governmental laboratories, and their publications are acces- 
 sible to all who can read and write. There is therefore no excuse 
 
134 AIR, WATER, AND FOOD 
 
 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 saddest commentary on human weakness and 
 lack of rational thought. 
 
CHAPTER IX 
 
 ANALYTICAL METHODS 
 
 In the discussion of the methods employed for the examination 
 of food-materials, only a few typical substances have been con- 
 sidered, and the processes given are such as to bring into promi- 
 nence the scientific aspect 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 expe- 
 rience in the necessarily short time which can be alloted 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-ma- 
 terials are liable through the growth of the micro-organisms. 
 The analysis of milk includes determinations of specific gravity, 
 water, or total solids, ash, fat, proteids and sugar, the separation 
 of casein and albumin, and the detection of preservatives, color- 
 ing matters, and added water. 
 
 The breakfast cereals are taken as typical of vegetable foods. 
 The examination which may be made of this class includes the 
 determination of moisture, ash, fat, nitrogen and proteids, 
 starch, cellulose, and the products of peptonization and sacchari- 
 fication. 
 
 The nature and composition of the various fats and oils is 
 briefly illustrated by the examination of butter and the deter- 
 mination 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 ard " temperance drinks," flavoring essences and the like. 
 The determination of the relative proportion of volatile and 
 
 135 
 
136 
 
 AIR, WATER, AND FOOD 
 
 fixed acids, of the saccharine products of malting, and of volatile 
 oils or flavoring principles, is also instructive. 
 
 A more elaborate discussion of the methods used in food 
 analysis and of the interpretation of results will be found in 
 the larger works upon the subject. As reference books for the 
 use of the student in the laboratory, the following, in the author's 
 experience, have been found especially helpful: Leach: Food 
 Inspection and Analysis; Sherman: Organic Analysis; Rolfe: 
 The Polariscope in the Laboratory; Bulletin 107, Bureau of 
 Chemistry. 
 
 MILK 
 
 Milk is a food material of somewhat complex and variable 
 composition but can be described as essentially an aqueous 
 solution of milk sugar, mineral salts and soluble albumin con- 
 taining suspended globules of fat and partially dissolved casein. 
 
 General Composition. — In approximate figures the average 
 percentage composition of milk may be stated : 
 
 Per cent 
 Total solids 12.8 
 
 Fat 3 
 
 Protein 3 
 
 Ash o 
 
 Milk sugar 4 
 
 Solids not fat 9 
 
 From these figures there may be in normal milk quite decided 
 variations and figures have been reported which differ widely 
 from them, some of the discrepancies of the older analyses being 
 undoubtedly due to the imperfect methods of analysis employed. 
 
 Lythgoe * states that all milk completely drawn from healthy 
 cows will fall between the following limits : 
 
 
 Extreme limits, 
 per cent. 
 
 Usual limits, 
 per cent. 
 
 Herd milk, 
 per cent. 
 
 Total solids 
 
 IO. O-17.O 
 2.2- 9.O 
 2.1- 8.5 
 0.6- O.9 
 4.O- 6.0 
 7-5-II.O 
 
 10. 5-16.0 
 
 2.8- 7.0 
 
 2-5- 4-5 
 0.7- 0.8 
 
 4-2-5-5 
 7.7-10.0 
 
 II. 8-15.O 
 3.2- 6.0 
 2.5- 4.0 
 0.7- 0.8 
 
 4-3- 5-3 
 8.0- 9.5 
 
 Fat 
 
 Protein 
 
 Ash 
 
 Milk sugar 
 
 Solids not fat 
 
 
 * Bull. Mass. State Bd. Health, 1910, p. 419. 
 
ANALYTICAL METHODS 
 
 137 
 
 Variations in Composition. — Besides variations in compo- 
 sition which may be due to individual cows there are also certain 
 well-established differences due to environment or to racial influ- 
 ences. Among the more important of these are: 
 
 (1) TJie Breed of the Cow. — Some breeds yield quantity, 
 others quality. The Jersey and Guernsey cattle, for instance, 
 give comparatively small quantities of milk rich in fat; the 
 Holstein cows, on the other hand, yield much larger amounts of 
 milk of decidedly lower solids and fat content. These differ- 
 ences are well summarized in the following table based on data 
 collected by the Massachusetts Board of Health.* 
 
 Breed. 
 
 Specific 
 gravity. 
 
 Total 
 
 solids, 
 
 per cent. 
 
 Fat, 
 per 
 cent. 
 
 Protein, 
 
 per 
 
 cent. 
 
 Ash, 
 
 per 
 
 cent. 
 
 Solids 
 not fat, 
 per cent. 
 
 Milk 
 
 sugar, 
 
 per cent. 
 
 Jersey 
 
 Guernsey 
 
 Ayrshire 
 
 Dutch Belt.. . 
 Holstein 
 
 I-034 
 I-034 
 I.032 
 I.032 
 I.032 
 
 14-57 
 
 14.40 
 12.57 
 12.03 
 11.96 
 
 5.40 
 5.00 
 4.00 
 3.60 
 
 3-35 
 
 3-54 
 
 3-77 
 2.90 
 2.62 
 2.99 
 
 O.78 
 O.77 
 
 0-77 
 O.68 
 O.69 
 
 9.17 
 9.40 
 8-57 
 8-43 
 8.6l 
 
 4.85 
 4.86 
 4.90 
 5.00 
 4.89 
 
 If individual differences are eliminated and only fully drawn 
 mixed milk from herds is considered, the variation due to breed 
 is the factor of the greatest influence in permanently affecting 
 the composition of milk. 
 
 (2) The Time of Year. — The poorest milk is produced during 
 the spring and early summer months, the richest during the 
 seasons of autumn and early winter, when the cattle are getting 
 a smaller proportion of green feed. This difference is clearly 
 shown in the following table f which gives the seasonal average 
 for 16 years: 
 
 
 Total solids, 
 per cent. 
 
 Fat, 
 per cent . 
 
 Solids not fat, 
 per cent. 
 
 Nov.— Jan 
 
 I3-04 
 12.72 
 12.66 
 13-03 
 
 4. II 
 3-88 
 3-89 
 4-25 
 
 8-93 
 8.84 
 8-77 
 8.78 
 
 Feb. -Apr 
 
 May — Aug 
 
 Oct. -Nov 
 
 
 * Bar. of Chem., Bull. 132, p. 129. 
 
 f Richmond: Dairy Chemistry, p. 126. 
 
138 
 
 AIR, WATER, AND FOOD 
 
 This variation in composition of milk between the pasture-fed 
 and the stall-fed season has in the past received legal recognition 
 in the fixing of milk standards. In Massachusetts for many 
 years the legal standard for total solids was set at 13 per cent 
 in the winter months and at 12 per cent in the summer season. 
 
 (3) Time of Day. — Milk which has been drawn in the even- 
 ing is nearly always richer in fat than the morning milk as shown 
 in the following averages: 
 
 
 Specific 
 gravity. 
 
 Total solids. 
 
 Fat. 
 
 Morning milk 
 
 I.0322 
 1-0318 
 
 12.53 
 12.94 
 
 3-63 
 4.04 
 
 Evening milk 
 
 (4) "Fore" milk vs. "strip pings." — If different portions of 
 the whole quantity of milk obtained at a single milking are ex- 
 amined separately they will be found to show marked differences 
 in fat content, especially as between the first and last portions. 
 The other constituents of the milk do not vary so greatly as 
 the fat. The first portions of milk, the "fore" milk, contain 
 much less fat than do the last portions or "strippings." The 
 following figures, due to Van Slyke, illustrate this point: 
 
 
 Per cent of fat in milk. 
 
 
 Cow 1. 
 
 Cow 2. 
 
 Cow 3. 
 
 First portion drawn 
 
 O.90 
 2.60 
 
 5-35 
 9.80 
 
 I.60 
 3.20 
 4.10 
 8.IO 
 
 1 .60 
 
 Second portion drawn 
 
 3-25 
 5.00 
 
 Third portion drawn 
 
 Fourth portion drawn (strippings) . 
 
 8.30 
 
 This difference in composition is explained by the separation 
 of the milk while in the udder of the cow, cream rising to the 
 top just as would happen if the milk stood in a vessel, hence 
 being drawn last. Dishonest dairymen have in the past taken 
 advantage of this fact in adulteration cases, by having the cows 
 partially milked in the presence of unsuspecting witnesses, the 
 resulting " known purity" milk being thus largely "fore" milk. 
 
ANALYTICAL METHODS 139 
 
 In general it will be found that to whatever causes the varia- 
 tions noted in the composition of milk are due, the differences 
 are shown much more in the fat than in any other constituent. 
 The protein is also variable, although to a somewhat less extent, 
 and the milk sugar and ash are much more nearly constant. 
 
 METHODS OF ANALYSIS 
 
 Preparation of the Sample. — Since the cream will rise on a 
 sample of milk sufficiently in five minutes to destroy the uni- 
 formity of the sample, great care must be used in taking a portion 
 for analysis to ensure that it represents a fair average of the 
 milk. The best way is to pour the milk from the containing 
 vessel into another and back again several times, or if this is 
 impracticable it should be thoroughly stirred before being sam- 
 pled. If the analytical sample has stood for any appreciable 
 time it should be mixed by pouring back and forth before a 
 portion is removed to test, otherwise concordant results cannot 
 be obtained. Do not shake the sample since this tends toward 
 a separation of the fat. 
 
 Specific Gravity. — This is usually taken with a special form 
 of hydrometer, known as a lactometer. The Quevenne lactom- 
 eter has a scale graduated into 25 equal parts, extending from 
 15 to 40, corresponding to specific gravities from 1.015 to 1.040. 
 The best form of instrument is that provided with a thermometer. 
 
 The lactometer is graduated to give correct results at 6o° F. 
 (15. 6° C.) and the reading should be made at approximately 
 that temperature, between 55 and 65 degrees, and then corrected 
 to standard temperature. This may be done by adding 0.1 
 to the reading for each degree F. above 6o° F., or subtracting 
 0.1 for each degree F. below 6o° F. If the temperature is 
 read in Centigrade degrees the correction may be made by the 
 table on page 216. 
 
 The New York Board of Health lactometer has a scale reading 
 o in water, and 100 in milk with a specific gravity of 1.029, which 
 is taken as the lowest limit for pure milk. The instrument is 
 used in the same manner as the Quevenne lactometer and the 
 
140 AIR, WATER, AND FOOD 
 
 readings can readily be converted into degrees of the latter 
 instrument. 
 
 Notes. — The specific gravity of milk fat is about 0.93 ; of the 
 solids not fat approximately 1.5. The specific gravity of the 
 milk itself is thus a function of the two; the former lowers it, 
 the latter increases it. As would be expected from the variable 
 composition of milk, the specific gravity is also a variable. The 
 values for normal milk from a herd, however, will usually fall 
 between 1.030 and 1.034. 
 
 Taken by itself the specific gravity is of little value in showing 
 adulteration. The addition of water lowers the specific gravity 
 of milk; the removal of cream raises it, this being the lighter 
 portion of the milk. It is therefore theoretically possible by 
 skilful manipulation to both skim and water a sample and still 
 have its specific gravity correspond to that of normal milk. 
 Such a sample would, however, be readily recognized by one 
 familiar with the appearance of the genuine product. 
 
 The lactometer reading is of value in rapid analysis of milk 
 for calculating the solids in connection with the Babcock method 
 of fat determination (see page 148). 
 
 Total Solids. — Use a platinum dish having a flat bottom 
 about 2 \ inches in diameter. Ignite and weigh the dish accu- 
 rately, then add about 5.1 grams to the weights on the balance- 
 pan. With a pipette deliver 5 c.c. of the well-mixed milk into 
 the dish and weigh the whole as rapidly as possible to the nearest 
 milligram. Evaporate the milk to dryness on the water-bath 
 and then dry it in the oven at ioo° C. to constant weight. Three 
 hours drying is usually sufficient. 
 
 Notes. — It is important that the milk should be dried in a 
 thin layer, so that the removal of the water shall take place as 
 quickly as possible. Under these conditions the residue ob- 
 tained is nearly white, but if the process be prolonged, it may 
 have a brownish color from the caramelization of the sugar. 
 
 If it is not desired to determine ash on the same weighed 
 portion as used for the solids, lead foil dishes or tin blacking 
 box covers may be used instead of platinum dishes. 
 
 Ash. — Ignite the platinum dish containing the residue from 
 
ANALYTICAL METHODS 
 
 141 
 
 the preceding determination at a low red heat until the ash is 
 white or of a uniform light gray color. This may be done in a 
 muffle furnace at a temperature not exceeding about 6oo° C, 
 or over a burner carefully regulated so that the dish is nowhere 
 heated above the slightest visible redness. 
 
 The ash, after weighing, may be tested 
 for boric acid or carbonates as described 
 on page 154. 
 
 Fat. — (a) Adams' Paper Coil Method. 
 Roll a strip of fat-free blotting paper * 
 about 22 inches long and 2 \ inches wide, 
 into a loose coil and fasten it by a bit 
 of wire. Hold the coil in one hand and 
 slowly run on to the upper end of it ex- 
 actly 5 c.c. of milk from a pipette. If 
 preferred, about 5 grams of milk may 
 be weighed quickly in a small beaker, 
 and one end of the coil introduced so as 
 to absorb the milk, care being taken to 
 absorb it as nearly completely as possible. 
 The beaker is then quickly re- weighed. 
 
 Place the coil, after charging with the 
 milk, dry end downward, in the water 
 oven and dry it for two hours, then 
 extract it for at least two hours in a 
 Soxhlet extractor as shown in Fig. n. J 
 Use about 100 c.c. of either petroleum^ { 
 ether or anhydrous ethyl ether and weigh 
 the flask to the nearest milligram. At 
 the end of this time disconnect the appa- Fig. n. 
 
 ratus when the extractor is nearly full of ether, thus recovering 
 a large portion of the solvent, and evaporate the remainder 
 {away from a flame), conveniently by the electric heater, using 
 suction. Dry the fat to constant weight in the water-oven. In 
 
 * Schleicher and Schiill make suitable strips which can be obtained from dealers 
 in chemical supplies, or the strips may be previously prepared in the laboratory 
 from thick filter paper and extracted with ether before using. 
 
142 AIR, WATER, AND FOOD 
 
 drying the extracted fat it may be heated for two hours the 
 first time, then in one hour periods until the loss of weight is 
 not over a milligram. 
 
 Notes. — The only part of the method due to Adams is the 
 drying of the milk on porous paper. This is, however, of great 
 importance since the 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 is more easily extracted; further, 
 owing to the greatly increased surface exposed, the extraction 
 of the fat is practically complete in a comparatively short time. 
 
 Ethyl ether is the solvent commonly employed but care should 
 be taken that it is anhydrous, otherwise small amounts of milk 
 sugar will be extracted. For this reason petroleum ether is 
 to be preferred as a solvent, although its action is considerably 
 slower than that of the other. 
 
 The Adams method is probably the most accurate for fat de- 
 termination in milk, but in actual practice is not used so much 
 as the more rapid centrifugal methods. 
 
 (b) Babcock Method. — Measure 17.6 c.c. of the milk from a 
 pipette into the graduated test bottle; add 17.5 c.c. of sulphuric 
 acid (sp. gr. = 1.825) pouring it in slowly so as to form a layer 
 beneath the milk. After the acid has thus been added to all the 
 bottles mix the milk and acid thoroughly by a rotary motion, 
 avoiding the spurting of the liquid into the neck of the bottle. 
 Place the bottles in opposite pockets of the centrifuge in even 
 numbers and whirl them for five minutes at the proper speed. 
 The correct speed varies from 1000 revolutions per minute for 
 a 10-inch wheel to 700 for one of 24 inches diameter. Then re- 
 move the bottles and add hot water up to the necks, after which 
 whirl them again for one minute. Again add hot water until 
 the fat rises nearly to the top of the graduations. Whirl again 
 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 bottles in water at 6o° C. If now one point of the 
 
ANALYTICAL METHODS 143 
 
 dividers is placed at the o mark of the scale on the bottle used, 
 the other will indicate the per cent of fat in the milk. 
 
 Notes. — Methods based on centrifugal separation of the fat, 
 of which the Babcock method is the pioneer, are by far the most 
 rapid and convenient for general use. They have practically re- 
 placed the more tedious extraction methods and are universally 
 employed in creameries and milk depots. 
 
 When the acid and milk are mixed the mixture becomes hot 
 and turns dark colored on account of the charring of the milk 
 sugar. The casein is first precipitated and then dissolved. 
 The retarding effect of the milk serum solids being thus elimi- 
 nated, the fat globules are free to collect in a mass. 
 
 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, often with a layer of white par- 
 ticles beneath it, it generally indicates that the acid is too weak 
 or that the milk was too cold when the acid was added. A 
 dark-colored fat with a sub-stratum of black particles indicates 
 that the acid is too strong. The best results will be obtained 
 by the use of acid of the strength noted above. 
 
 The capacity of the graduated neck of the bottle between the 
 o and 10 marks is 2 c.c. The specific gravity of warm milk fat 
 is 0.9, hence 2 c.c. will weigh 1.8 grams or one-tenth of the 
 weight of 17.6 c.c. of milk (approximately 18 grams). The 
 measurement of the extreme limits of the column of fat, rather 
 than to the upper meniscus, is to correct for the small amount of 
 fat, 0.1 to 0.2 per cent, that remains in the acid solution. 
 
 Milk which has been preserved with formaldehyde usually re- 
 quires a longer time and more vigorous shaking to dissolve the 
 curd, on account of the hardening action of this preservative on 
 the coagulated casein. It is often advantageous to stand the 
 bottles in water at 6o° C. for a time before whirling. Samples 
 containing formaldehyde will usually give a violet color when 
 the acid is added to the milk. 
 
 (c) Gottlieb Method.* — With a pipette place 5 c.c. of milk 
 in a 50-c.c. glass stoppered cylinder and add the following re- 
 
 * Rose: Z. angew. Chem., 1888, 100; Gottlieb: Landw. Vers. Stat., i8q2, 6. 
 
144 
 
 AIR, WATER, AND FOOD 
 
 agents, being careful to add them in the order given and to 
 shake the stoppered cylinder thoroughly after the addition of 
 each reagent: i c.c. of ammonia (sp. gr. = 0.96), 5 c.c. of alcohol, 
 12.5 c.c. of ethyl ether, and 12.5 c.c. of petroleum ether. Let 
 the cylinder stand until the lower layer is free from bubbles — 
 several hours if necessary. Transfer the upper layer to a tared 
 flask by means of an arrangement similar to a wash-bottle, 
 as shown in Figure 12. Adjust the sliding tube until the end 
 rests just above the junction of the two lay- 
 ers, then by gently blowing force out the 
 upper layer into the flask. Repeat the ex- 
 traction, using 10 c.c. each of ethyl ether and 
 petroleum ether and blowing it off into the 
 flask as before. Distill off the solvent and 
 dry the residual fat to constant weight in 
 the water oven. Dissolve the weighed fat 
 in a little petroleum ether. If a residue 
 is found, due to a trace of the aqueous layer 
 which was blown off with the ether, wash it 
 several times in the flask by careful decanta- 
 tion with petroleum ether. Finally dry and 
 weigh the flask and residue and deduct from 
 the previous weight. The difference is the 
 weight of purified fat. 
 Notes. — All of the successful methods for determining the fat 
 by direct extraction from the milk itself involve the complete or 
 partial solution of the casein. In the Gottlieb method the 
 casein, precipitated from the milk in very finely divided form by 
 the alcohol, is dissolved by the ammonia. The fat is dissolved 
 by the ethyl ether and the addition of petroleum ether is to 
 render less soluble the milk sugar or other non-fatty solids 
 which would be dissolved by ethyl ether alone. 
 
 The method, while applicable to whole milk, is especially 
 valuable in determining fat in such products as skim milk or 
 buttermilk which are low in fat. In such cases it is better to 
 use 10 c.c. of milk and double the quantity of reagents. 
 
ANALYTICAL METHODS 145 
 
 Milk Sugar. — The sugar in milk is most readily determined 
 by its reducing action on Fehling's solution. 
 
 Munson and Walker Method.* — Directions. — Measure 25 
 c.c. of milk into a 500-c.c. graduated flask. Add about 400 c.c. 
 of water, 10 c.c. of copper sulphate solution,! then 35 c.c. of 
 tenth-normal sodium hydroxide (or an equivalent quantity of a 
 stronger solution) and make up to 500 c.c. Mix thoroughly 
 and filter through a dry filter. 
 
 In a Xo. 3 beaker mix 25 c.c. of the Fehling's copper sulphate 
 solution and 25 c.c. of the alkaline tartrate solution. Add 50 
 c.c. of the milk sugar solution, prepared as above, cover the 
 beaker with a watch glass, and heat it upon wire gauze. Reg- 
 ulate the flame so that boiling shall begin in four minutes, and 
 continue the boiling for exactly two minutes. 
 
 Filter the cuprous oxide without delay through asbestos in 
 a weighed Gooch crucible, wash it with hot water until free 
 from alkali, pour out the hot filtrate, then wash with 10 c.c. 
 of alcohol and, finally, with 10 c.c. of ether. Dry the crucible 
 for 30 minutes at the temperature of boiling water and weigh. 
 Find the milligrams of lactose monohydrate corresponding to 
 the weight of cuprous oxide from Table XII on page 221 and 
 calculate the percentage present in the milk. 
 
 Notes. — Before the lactose can be determined by Fehling's 
 solution the protein and fat must first be removed. This is 
 done by the precipitation with copper hydroxide, the fat being 
 carried down mechanically by the precipitated protein. The 
 addition of alkali should be such that a slight excess of copper 
 still remains in solution, since an excess of alkali will prevent 
 the precipitation of part of the protein. The quantity stated 
 in the procedure is correct for most milks. 
 
 On account of the considerable dilution of the sample, the vol- 
 ume of the precipitated protein and fat need not be considered. 
 
 The general principle upon which all these methods depend 
 
 * /. Am. Chem. Soc, 1906, 663; 1907, 541. 
 
 f 69.28 grams per liter. The copper sulphate solution used in the Fehling de- 
 termination may be conveniently employed. 
 
146 AIR, WATER, AND FOOD 
 
 is based on the fact that certain sugars, among which is lactose, 
 have the power of reducing an alkaline 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 solution is liable to change. 
 
 The amount of reduction of the copper salt to the cuprous 
 oxide is affected by the rate at which the sugar solution is added, 
 the time and degree of heating, and the strength of the sugar so- 
 lution; hence the necessity for adopting a definite procedure 
 and for taking the results from a table determined by exactly 
 the same procedure for varying amounts of the sugar. 
 
 The asbestos which is used should be previously boiled in 
 nitric acid and then in dilute sodium hydroxide and thoroughly 
 washed. A layer about a centimeter thick should be used in 
 the crucible, and a "blank" determination made with the 
 Fehling's solution should not show a change in weight greater 
 than one-half milligram. After the precipitated cuprous oxide 
 has been weighed it may be dissolved in hot dilute nitric acid, 
 and the asbestos in the crucible washed and dried as described, 
 when it is again ready for use. Do not remove the asbestos 
 from the crucible. 
 
 Proteins. Determination of Total Protein. — This is best done 
 by the Kjeldahl method. Weigh 5 grams of milk into a Kjeldahl 
 flask, add 10 c.c. of concentrated sulphuric acid and three drops 
 of mercury and carry out the determination as described on 
 page 182. 
 
 The tendency of the alkaline solution to froth during the 
 distillation, which is especially noticeable with milk, can be 
 prevented by the addition of a piece of paraffin the size of a pea. 
 Multiply the per cent of nitrogen by the factor 6.38 to obtain 
 the per cent of protein. 
 
 Separation of Casein and Albumin. — The usual method of 
 precipitating the casein by acid at a temperature below the 
 
ANALYTICAL METHODS p 147 
 
 coagulating point of the albumin, while capable of good results, 
 is tedious and rather unsatisfactory except after considerable 
 experience. The following volumetric method, devised by 
 Van Slyke and Bosworth * gives results of almost equal 
 accuracy, but requires much less time and skill. 
 
 Measure 20 c.c. of the well-mixed milk into a 200-c.c. grad- 
 uated flask and add about 80 c.c. of water. Add 1 c.c. of phenol- 
 phthalein solution and tenth-normal sodium hydroxide until a 
 faint pink color remains throughout the mixture even after con- 
 siderable shaking. Avoid an excess of alkali. 
 
 To the neutralized diluted sample, which should be at a tem- 
 perature of 1 8° C. to 24 C, add tenth-normal acetic acid in 
 5-c.c. portions, shaking vigorously for a few seconds after each 
 addition. After thus adding 25 c.c. and shaking, the mixture 
 is allowed to come to rest. If enough acid has been added, the 
 casein separates promptly in large, white flakes, and on standing 
 a short time, the supernatant liquid appears clear, not at all 
 milky. If the addition of 25 c.c. of acid is insufficient to sepa- 
 rate the casein properly, add 1 c.c. more of acid and shake; 
 continue this addition of acid 1 c.c. at a time, until the casein 
 separates promptly and completely upon standing a short time. 
 Note the number of c.c. of acid used. 
 
 After the casein is completely precipitated make up the mix- 
 tures to the 200-c.c. mark with water, shake thoroughly and 
 filter through a dry filter. Filtration should be rapid and the 
 the filtrate quite clear. If a marked turbidity is apparent in 
 the filtrate, a new sample should be taken and the process re- 
 peated, using more acid than before. Titrate 100 c.c. of the 
 filtrate with tenth-normal sodium hydroxide and phenolphtha- 
 lein to a pink color which remains throughout the solution for 
 thirty seconds. Subtracting the number of c.c. of sodium hy- 
 droxide from one-half the c.c. of tenth-normal acetic acid added 
 will give the c.c. of acid required to precipitate the casein for 
 
 10 c.c. of milk. (1 c.c. of — acetic acid = o. 113 15 gms. of 
 
 casein.) 
 
 * /. Ind. Eng. Chem., 1909, 768. 
 
148 AIR, WATER, AND FOOD 
 
 Calculation of Milk Solids. — It has long been recognized that 
 in normal milk the constituents are present in a fairly constant 
 ratio. This being true, it should be possible, having deter- 
 mined two factors, to find a third by calculation, or at least 
 to show by such calculation a sufficient variation from the 
 normal to indicate the adulteration of the sample. For ex- 
 ample, given the lactometer reading and fat, to calculate the 
 total solids: 
 
 L = the lactometer reading, 
 
 s = increase in lactometer reading by 1 per cent solids not fat, 
 / = decrease in lactometer reading by 1 per cent fat, 
 T = total solids, 
 S = per cent of solids not fat, 
 F = per cent of fat. 
 
 Then L = Ss - Ff, 
 
 Since S = T - F 
 
 L = (T-F)s-Ff, 
 
 whence T = •*■ + F. 
 
 s 
 
 The uncertainty of the calculation lies in the values for 5 and/, 
 which, on account of the difference in solution densities of the 
 components of the solids not fat, are not absolute constants. 
 
 Based on the principle just stated, various formulas have 
 been proposed for the calculation of milk solids. One of the 
 simplest of these is that of Hehner and Richmond * 
 
 T = - + 1.2 F + 0.14, 
 4 
 
 where T is the per cent of total solids, L the reading of the lac- 
 tometer, and F the fat. 
 
 When a number of calculations are to be made, Richmond's 
 "Milk Scale" will be found convenient. This is an instrument 
 based on the principle of the slide-rule, having three scales, 
 two of which, for the fat and the total solids, are marked on 
 
 * Analyst, 1888, 26; 1892, 170. 
 
ANALYTICAL METHODS 
 
 149 
 
 the body of the rule, while that for the lactometer readings 
 is marked on the sliding part. 
 
 A similar relation has been worked out for the protein, so 
 that if a constant value be assumed for the ash, the composition 
 of a sample may be determined with a fair degree of approxima- 
 tion from the two simple determinations of specific gravity and 
 Babcock test. 
 
 The relation between the protein and fat has been expressed 
 by Van Slyke* as P = 04 (F - 3) + 2.8. Similarly Olsen f 
 has proposed the following formula for calculating the protein 
 from the total solids (T.S.) : 
 
 T.S. 
 
 T.S. - 
 
 i-34 
 
 These values will naturally be most nearly correct in the case 
 of normal average milk. With watered or skimmed milk they 
 will be only approximate. 
 
 In the table below the values calculated for a sample are com- 
 pared with those actually determined: 
 
 Determination. 
 
 Actual 
 
 values. 
 
 33 
 
 
 3 
 
 80 
 
 12 
 
 73 
 
 
 
 7i 
 
 3 
 
 33 
 
 5 
 
 04 
 
 8 
 
 93 
 
 Calculated values. 
 
 Lactometer reading 
 
 Fat (Babcock) 
 
 Total solids 
 
 Ash 
 
 Proteins 
 
 Milk sugar 
 
 Solids not fat 
 
 12.95, 
 
 0.7 (assumed) 
 j 3.12 (Van Slyke) 
 I 3 . 29 (Olsen) 
 
 5.16 
 
 9-i5 
 
 Examination of Milk Serum. — The most variable constitu- 
 ents of normal milk are the fat and protein, especially the former; 
 the least variable are the ash and milk sugar. The milk serum, 
 or milk from which the fat and protein have been removed, is, 
 therefore, of more uniform composition than the milk itself, 
 hence better suited for the detection of adulteration and espe- 
 
 * /. Am. Chem. Soc, igoS, 1182. 
 t /. Ind. Eng. Chem., igog, 253. 
 
150 AIR, WATER, AND FOOD 
 
 daily of added water. The serum may be prepared by adding 
 to the milk some suitable precipitant of the protein, as calcium 
 chloride, acetic acid or copper sulphate. The clear liquid after 
 nitration may be examined for its content of dissolved solids, 
 its specific gravity or most conveniently by the immersion 
 refractometer. 
 
 The Copper Sulphate Method* — Dissolve 72.5 grams of 
 crystallized copper sulphate in water and dilute to a liter. This 
 solution should be adjusted, if necessary, so that it will refract at 
 36 degrees on the scale of the immersion refractometer at 20 C. 
 or have a specific gravity of 1.0443 at 2 °° C. compared with 
 water at 4 C. To one volume of the copper solution add 
 four volumes of milk, shake well and filter. The filtrate will 
 usually be clear after the first few drops have passed through. 
 On the clear filtrate either the refraction at 20 C, the specific 
 
 gravity ( — ^ J or the total solids may be determined. 
 
 Notes. — Examination of the copper serum from 150 samples of 
 known purity milk gave refractions varying from 36.1 to 39.5, 
 while the total solids of the same samples showed a range from 
 17.17 per cent to 10.40 per cent and the fat varied from 7.7 per 
 cent to 2.45 per cent. 
 
 The minimum values for the copper serum of normal milk 
 are 36 degrees for the refraction at 20 C, 1.0245 for the specific 
 
 gravity (— - 1 and 5.28 per cent for total solids. 
 
 If the milk is already soured, it may be filtered and similar 
 determinations made on the natural sour serum, which for un- 
 watered milk should not refract below 38.3 or have a specific 
 
 gravity at — 5- 1 below 1.0229. 
 4 
 
 SPECIAL TESTS FOR ADULTERANTS 
 
 Cane Sugar. — Cane sugar may be present in milk from 
 diluted condensed milk used to eke out the supply or may be 
 present from calcium saccharate, added as a thickening agent. 
 * Lythgoe: Ann. Rpt. Mass. Bd. Health, 1908, 594. 
 
ANALYTICAL METHODS 151 
 
 It is evident that any considerable amount which had been 
 added could be detected by the taste. 
 
 To detect the presence of cane sugar boil about 10 c.c. of the 
 milk with 0.1 gram of resorcin and 1 c.c. of strong hydrochloric 
 acid for five minutes. The liquid will be colored rose-red if 
 cane sugar is present. The color produced by heating should 
 not be confused with the pink color which may appear in the 
 cold if the milk contain certain coal-tar colors. 
 
 A similar test is the reduction of ammonium molybdate. As 
 recommended by Cotton * 10 c.c. of the milk are mixed with 
 0.5 gram of powdered ammonium molybdate and 10 c.c. of dilute 
 (1 to 10) hydrochloric acid are added. In another tube 10 c.c. 
 of milk known to be free from sucrose are similarly treated and 
 the tubes placed in a water-bath, the temperature of which is 
 gradually raised to about 8o° C. If sucrose is present, the 
 milk will gradually turn deep blue, while genuine milk remains 
 unchanged unless the temperature approaches the boiling point. 
 Cotton states that the reaction will detect as little as 1 gram 
 of cane sugar in a liter of milk. 
 
 Note. — Both of these tests, although used to detect cane 
 sugar, are in reality tests for levulose, formed in this case by 
 the partial inversion of the sucrose. 
 
 Preservatives. — The preservatives most commonly employed 
 in milk are formaldehyde, boric acid or borax, and mixtures of 
 the two, and possibly hydrogen peroxide and fluorides. Sali- 
 cylic acid and sodium benzoate, although largely used in some 
 other classes of food materials, have been reported very rarely 
 as present in milk. 
 
 Formaldehyde. — This is the ideal preservative for milk, 
 being readily used and by far the most efficient. Quantities 
 which give a proportion in the milk of from 1 in 10,000 parts 
 to 1 in 50,000 are ordinarily employed. Such an amount will 
 suffice to preserve the milk for from 24 hours to several days. 
 Larger quantities, such as 1 part in 3000, will preserve the milk 
 for months. These large amounts, however, would be more or 
 
 * /. Pharm. Chim., 1897, 362. 
 
152 AIR, WATER, AND FOOD 
 
 less apparent by the taste or odor. A tabular statement show- 
 ing the efficiency of formaldehyde in preserving milk as com- 
 pared with boric acid, borax and sodium carbonate will be found 
 in Leach's Food Analysis. 
 
 Several of the best tests for detecting formaldehyde are de- 
 scribed below. These may be applied directly to 10 c.c. of the 
 milk, or as suggested in the gallic acid test, a larger quantity, 
 25 to 100 c.c, may be distilled and the test applied to the first 
 portion of the distillate. 
 
 (1) When the sulphuric acid is added to the milk in making 
 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 de- 
 tected by this test, but it fails when the formaldehyde amounts 
 to 0.5 per cent. The test is more delicate if the sulphuric acid 
 contains a trace of ferric chloride. 
 
 (2) To 10 c.c. of milk in a small porcelain dish add an equal 
 volume of hydrochloric acid (1.20 sp. gr.). Add one drop of 
 ferric chloride solution and heat the dish with a small flame, 
 stirring vigorously, until the contents are nearly boiling. 
 Remove the flame and continue the stirring for two or three min- 
 utes, then add about 50 c.c. of water. The presence of formal- 
 dehyde 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. The color should 
 be observed carefully at the moment of dilution. This test 
 readily shows the presence of one part of formaldehyde in 
 250,000 parts of milk, if fresh. 
 
 (3) Gallic Acid Test* — This test has been found by Shermanf 
 to be much more delicate than either of the preceding tests. 
 25 to 50 c.c. of the milk should be acidulated with phosphoric 
 acid and distilled. To the first 5 c.c. of the distillate add 0.2 
 to 0.3 c.c. of a saturated solution of gallic acid in pure ethyl 
 
 * Barbier and Jandrier: Ann. Chim. anal., 1, 325; Mulliken and Scudder: Am. 
 Chem. J., igoo, 444. 
 
 f /. Am. Chem. Soc, 1905, 1499. 
 
ANALYTICAL METHODS 153 
 
 alcohol and pour it cautiously down the side of an inclined test 
 tube containing 3-5 c.c. of pure concentrated sulphuric acid. 
 If formaldehyde is present a green zone is formed at the junction 
 of the two layers, gradually changing to a pure blue ring. 
 
 The delicacy of the test is about one part of formaldehyde in 
 500,000 parts of milk. 
 
 Notes. — It should be borne in mind that when small amounts 
 of formaldehyde are added to milk the ordinary tests will show 
 the presence of the preservative for only a short time. For 
 example, it has been shown by Williams and Sherman * that 
 when formaldehyde was added to milk in the proportion of 1 part 
 to 100,000 only a faint test was given after 48 hours standing; 
 and that the preservative had entirely disappeared in from three 
 to five days. This is due to the gradual formation of conden- 
 sation products of the formaldehyde with the proteins of the milk 
 which do not respond to the usual reaction. In such a case, it is 
 better to distill the milk as directed and apply the test with 
 gallic acid to the distillate. The test is thus made more delicate, 
 so that the preservative may still be shown when the simpler 
 tests have failed. 
 
 Another possible contingency is that some substance may be 
 added with the formaldehyde which will interfere with the tests 
 for its detection. Both hydrogen peroxide and nitrites prevent 
 the reaction of formaldehyde in the usual tests and preserva- 
 tives are on the market which are mixtures of formaldehyde 
 with hydrogen peroxide or a nitrite. The sulphuric acid test 
 and the hydrochloric acid-ferric chloride test can be used to 
 show the formaldehyde in the presence of considerably larger 
 quantities of nitrites by first removing the latter. Add to 10 c.c. 
 of the milk 1 c.c. of a 10 per cent solution of urea, then 2 c.c. 
 of dilute (1 140) sulphuric acid and immerse the test tube in boil- 
 ing water for two minutes. Cool and carry out the test as usual. 
 The reaction between the urea and the nitrous acid may be 
 expressed : 
 
 CO (NH 2 ) 2 + 2 HNO2 = C0 2 + 2 N 2 + 3 H 2 0. 
 
 * /. Am. Chem. Soc, 1905, 1497. 
 
154 AIR, WATER, AND FOOD 
 
 Boric Acid or Borax. — Make 25 c.c. of the milk distinctly 
 alkaline with lime water and evaporate to dryness on the water- 
 bath. Char the residue over a flame but do not necessarily 
 heat it until white. Digest the residue with 15-20 c.c. of water 
 and add hydrochloric acid (1.12) until the mixture is faintly 
 acid to litmus paper. Filter, and add 1 c.c. of acid in excess. 
 Place a strip of turmeric paper in the solution and evaporate to 
 dryness on the water-bath. If boric acid or borates are present, 
 the paper takes on a peculiar red color, which is changed by 
 ammonia to a dark blue-green, but is restored by acid. Excess 
 of hydrochloric acid should be avoided, as it turns the paper a 
 dirty green when evaporated. This test can also be applied 
 to the hydrochloric acid solution of the ash. 
 
 Sodium Carbonate. — Detected in the milk-ash, as on page 
 141. 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 rosolic 
 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. 
 
 Salicylic and benzoic acids. — If it is desired to test for these, 
 the following method may be employed. To 25 c.c. of milk add 
 100 c.c. of water and precipitate the proteins and fat with copper 
 sulphate and sodium hydroxide, as described on page 145. 
 Filter and add to the filtrate 5 c.c. of concentrated hydro- 
 chloric acid. Extract with ether and proceed as outlined on 
 page 196. 
 
 Coloring Matter. — The object in adding coloring matter to 
 milk is in general to disguise the bluish appearance of skimmed 
 or watered milk. For this reason it is rather unusual to find 
 added color in the case of milk which is of standard quality, 
 although such cases have been reported. 
 
 Formerly the chief color used was annatto, a reddish-yellow 
 coloring matter obtained from the seeds of Bixa Orellana, a 
 shrub growing in South America and the West Indies. A solution 
 of the color in very dilute alkali is employed. More recently 
 
ANALYTICAL METHODS 155 
 
 various coal-tar dyes and even caramel have been used. The 
 latter is, perhaps, not so likely to be found, because its color 
 is too brown and not enough yellow to give the desired creamy 
 appearance to the milk which is so easily obtained with annatto. 
 The coal-tar colors, especially mixtures of yellow and orange 
 azo dyes, give very good results. 
 
 Leach * has suggested a general scheme for the identification 
 of these colors in milk, which with some modifications which 
 experience in the writer's laboratory has shown to be helpful 
 in detecting annatto especially, is given below. 
 
 Procedure. — Place about 100 c.c. of the milk in a small 
 beaker, add 3-4 c.c. of 25 per cent acetic acid (sp. gr. = 1.04), 
 stir thoroughly and allow the beaker to stand quietly on the 
 water-bath for about ten minutes, the casein being thus sepa- 
 rated as a compact cake. Decant off the whey, squeezing the 
 curd as dry as possible with a spatula. Transfer the curd to 
 a flask, cover it with ether, stopper tightly, and shake the flask 
 violently in order to break up the curd as much as possible. 
 Let it stand for several hours, preferably over night. 
 
 Pour off the ether, which contains the annatto, and evap- 
 orate {away from a flame) until no odor of ether remains. Add 
 5 c.c. of water and then dilute sodium hydroxide until the mix- 
 ture, after thorough stirring with a glass rod, is faintly alkaline 
 to litmus paper, and filter through a wet filter. If annatto is 
 present it will permeate the filter and give it an orange-brown 
 color which may readily be seen if the filter is removed from the 
 funnel and the fat washed off under the tap. Its presence may 
 be confirmed by touching the colored portion of the paper with 
 a drop of stannous chloride, which gives a pink color with annatto. 
 
 After pouring off the ether examine the milk-curd for caramel 
 or coal-tar color. 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 coal-tar dye, 
 the curd will have a yellow or orange tint. If now some con- 
 centrated hydrochloric acid is poured over the curd, the color 
 
 * /. Am. Chem. Soc, igoo, 207. 
 
156 AIR, WATER, AND FOOD 
 
 will change immediately to a bright pink with the coal-tar colors 
 ordinarily used. 
 
 Notes. — When the milk is curdled by the acid, any added color 
 is carried down by the curd. When this is subsequently treated 
 with ether the fat and annatto are dissolved, leaving any cara- 
 mel or coal-tar color still in the curd. Since the detection 
 of the two latter colors may depend upon recognizing color in 
 the curd, this should always be compared with the curd prepared 
 in the same manner from a sample of milk known to be free from 
 color. 
 
 The ordinary tests for caramel as used to show its presence 
 in distilled liquors or vanilla extract are not sufficiently delicate 
 to detect the extremely small quantity which suffices to impart 
 the desired shade of color to the milk. The color imparted to 
 the curd, however, is characteristic and readily recognized. 
 
 It is possible that coal-tar dyes may be used which do not 
 give the pink reaction with hydrochloric acid, since this is char- 
 acteristic in general only of the azo class of dyes. Even in 
 these cases, however, the orange color of the dye is readily per- 
 ceptible in the separated curd. 
 
 Milk colored with an azo dye may occasionally fail to show 
 its presence if the sample is old or partly decomposed before 
 being tested. This has been shown by Blyth * to be due to the 
 reduction of the dye by nascent hydrogen produced by the growth 
 of certain anaerobic organisms. 
 
 Interpretation of Results. — Apart from the addition of 
 foreign ingredients, such as colors and preservatives, which are 
 detected by the specific tests described, the most common forms 
 of adulteration are the addition of water and the removal of 
 cream. By reference to the table on page 136, it will be seen 
 that on account of the variation in the composition of unadul- 
 terated cow's milk the detection in all cases is not an easy prob- 
 lem. The variation in the fat content, especially, makes it 
 more difficult to show with certainty the partial removal of 
 cream than the addition of water. 
 
 * Analyst, igo2, 146. 
 
ANALYTICAL METHODS 
 
 157 
 
 This is well shown in the following table in which "A " is 
 a normal milk, U B" the same milk in which the fat has been 
 reduced to 3.6 per cent by adding water and "C" the same milk 
 in which the fat has been reduced to 3.6 per cent by skimming. 
 
 
 A 
 
 B 
 
 C 
 
 Total solids 
 
 12.78 
 4.00 
 2.89 
 5.00 
 0.71 
 8.78 
 
 n-34 
 
 3.60 
 2.60 
 4-5o 
 0.64 
 
 7-74 
 
 12.09 
 3.60 
 2.91 
 4.98 
 0. 72 
 
 Fat 
 
 Protein 
 
 Sugar 
 
 Ash 
 
 Solids not fat 
 
 8.61 
 
 
 
 It is seen that in sample C it is only the fat that has been 
 decreased to any degree. In fact there is nothing in the figures 
 given for C to indicate in any way that the sample is not genuine 
 milk, while in B the solids not fat are so low as to show the adul- 
 teration quite plainly. 
 
 Composition of Milk of Known Purity. — The average com- 
 position of milk, together with the usual and the extreme limits 
 of variation, have already been stated on page 136. The greater 
 number of published analyses of genuine cows' milk have been 
 limited to determination of solids, fat and specific gravity. A 
 more detailed study, including the constants of the copper 
 serum, will be found in the following table,* which includes the 
 analyses of 33 samples of known purity milk from individual 
 cows, and 4 samples of herd milk, arranged in the order of their 
 percentage of total solids. 
 
 In collecting the samples milk was taken from the heaviest 
 milkers, so as to include a larger proportion of low-grade milk 
 for minimum values. None of the milk could be called excep- 
 tionally high grade, as samples were not collected from Jersey or 
 Guernsey cows. 
 
 Inspection of this table shows, as would be expected, a great 
 variation in the percentage of fat in the individual samples, the 
 highest being almost 100 per cent higher than the minimum 
 values. The solids not fat are seen to present a much less 
 
 * Lythgoe: Bull. Mass. Bd. Health, 1910, 422. 
 
158 AIR, WATER, AND FOOD 
 
 variation, and as Lythgoe has pointed out, this variation 
 is due very largely to the changes in protein content, the milk 
 sugar and ash remaining fairly constant. Upon this fact 
 depends the special value of an examination of the milk 
 serum. 
 
 In some cases all that may be necessary is to show by the 
 analysis that the milk does not conform to the legal standard. 
 In certain of the states, however, a legal distinction is made 
 between milk which is simply below standard and milk which has 
 been actually adulterated by skimming or watering. It is there- 
 fore of importance to show by the analysis whether water has 
 been added to the milk directly and not through the breed or 
 feed of the cow. 
 
 Detection of Watered Milk. — Since in general the water that 
 has been added is no different from the water already present 
 in the milk it is evident that this form of adulteration can be 
 detected only by showing chemical or physical changes in the 
 milk that could be ascribed only to the addition of water. Meth- 
 ods have been proposed, it is true, based on differences in the 
 added water, such as an abnormally high amount of nitrates, 
 which might have been derived from the polluted barnyard 
 well, but these methods are of little importance. 
 
 (a) Solids Not Fat. — Since the variation in proportion of 
 solids not fat in normal milk is much less than the range of 
 total solids this is of distinct value in showing added water. 
 Although as indicated in the table of limiting values on page 136, 
 the value for solids not fat may go as low as 7.5 per cent, this 
 is rather uncommon, and a fairer minimum would be 7.7 per 
 cent. A value below 7.7 per cent would certainly be suspicious 
 of added water and if accompanied by correspondingly low values 
 for the constants of the serum could be regarded as direct evidence 
 of adulteration. 
 
 (b) Milk Sugar. — As suggested by Lythgoe,* the milk sugar 
 may be employed to even greater advantage than the solids not 
 fat in showing adulteration. Knowing the percentage of solids 
 
 * Loc. cit. 
 
ANALYTICAL METHODS 
 
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 and of fat, the protein may be calculated by the formulae given 
 on page 149. Then if 0.7 be assumed as the value for the ash, 
 the milk sugar may be determined by subtracting from the 
 total solids the sum of the other constituents. The expression 
 for the milk sugar would then become 
 
 (1) Milk sugar = T.S. - (F + [0.4 (F - 3) + 2.8] + 0.7). 
 
 (2) Milk sugar = T.S. - (F + [~T.S. - — 1 + 0.7). 
 
 L 1.34J 
 
 The portion of the formula enclosed in brackets is the calcu- 
 lated protein in each case. In the case of pure milk the formulae 
 for calculating the protein will give very similar results, but 
 with adulterated milk they will be divergent, the difference 
 increasing with the extent of adulteration. In the case of 
 watered milk the calculated milk sugar will be too low, ordinarily 
 falling below 4.2 per cent, while, as will be shown later, with 
 skimmed milk, the milk sugar will be too high, generally above 4.8 
 per cent. 
 
 (c) Milk Serum. — If the preliminary calculation indicates a 
 possibility of the samples being watered an examination of the 
 serum should be made. This may be done preferably by the 
 copper sulphate method, which is described and the minimum 
 values for pure milk stated on page 150. The following table 
 due to Lythgoe shows the effect of systematic watering on the 
 composition of the milk and the constants of the serum in the 
 case of a milk which was above the average in solids not fat 
 and refraction. 
 
 COMPOSITION OF A SAMPLE OF MILK SYSTEMATICALLY 
 WATERED 
 
 Added 
 
 Solids 
 
 (per 
 
 cent). 
 
 Fat (per 
 cent). 
 
 Solids not 
 fat (per 
 cent). 
 
 Copper serum. 
 
 water 
 
 (per 
 
 cent). 
 
 Refrac- 
 tion, 20°. 
 
 Specific 
 
 gravity, 
 
 20° 
 
 4° 
 
 Solids 
 
 (per 
 
 cent). 
 
 O 
 IO 
 20 
 
 3° 
 40 
 
 50 
 
 13.18 
 
 11.86 
 
 IO-S4 
 
 9-23 
 
 7.91 
 
 6-59 
 
 4.20 
 3-78 
 3-36 
 2.94 
 2.52 
 2. 10 
 
 8.98 
 8.08 
 7.18 
 6.29 
 5-39 
 4-49 
 
 38.5 
 36.4 
 34-4 
 32.4 
 30.6 
 28.6 
 
 I .0272 
 I . 0249 
 I.0233 
 I .02II 
 I .0194 
 I. 0174 
 
 6.09 
 5-57 
 5-05 
 4-56 
 4.10 
 3-54 
 
ANALYTICAL METHODS 161 
 
 It is seen that each 5 per cent of added water lowers the 
 refraction by one scale division, hence with average milk, 
 refracting below 38 degrees, 10 per cent of added water could 
 be detected, and with rich milk 15 per cent can usually be 
 found. 
 
 Detection of Skimmed Milk. — Watering milk does not in 
 general change the relation of the various constituents to one 
 another, since these are all reduced in the same proportion, 
 but removing the fat does change these ratios. It is immaterial 
 whether the milk is skimmed by the actual removal of some of 
 the fat or whether separator skim milk is added to normal milk. 
 In either case the resulting product will have its fat content 
 largely reduced, while the proteins and sugar suffer but little 
 change. In normal milk, especially in the mixed milk of a herd, 
 the percentage of fat is rarely less than the protein (see table, 
 page 159). In 5500 analyses of American milks compiled by 
 Van Slyke, with a fat content between 3 and 5 per cent, the 
 average amount of fat was 3.92 per cent and the average amount 
 of proteins 3.20 per cent. If such milk be skimmed the fat may 
 be reduced to 1 per cent or even to 0.1 per cent but the protein 
 content will still be approximately the same as before. In the 
 calculation of milk sugar by the formulae given on page 160, 
 the same effect will be noticed, that is, the skimming will 
 lower the fat or the solids to a greater extent than the protein. 
 Hence the proteins calculated from the fat or total solids will 
 be too low and the calculated milk sugar will be too high. For 
 practical purposes the limit for unskimmed milk may be set 
 at 4.8 per cent, values above this being suspicious of skimmed 
 milk. 
 
 In addition to this preliminary test, the milk may be with 
 certainty declared skimmed if the fat falls below 2.2 per cent, 
 the solids not fat remaining above the average value of 8.5 
 per cent. If the fat is above 2.2 per cent and below 3.5 per 
 cent, the presence of skimmed milk may be confirmed by making 
 a Kjeldahl nitrogen determination on the suspected sample and 
 calculating the proteins by the factor 6.38. If the proteins 
 
162 AIR, WATER, AND FOOD 
 
 exceed the fat, as stated in the preceding paragraph, the sample 
 is skimmed. If, however, the fat is above 3.5 per cent, this pro- 
 cedure will no longer suffice, since the proteins rarely exceed 
 3.5 per cent. In these few cases, the skimming can be judged 
 only from the high specific gravity, high solids not fat and cor- 
 respondingly low fat. 
 
 Specific Gravity of Milk Solids. — The specific gravity of the 
 milk solids is sometimes used to show skimming. Fleisch- 
 mann's formula for calculating this is 
 
 T.S. 
 
 x == — — — ^— — — ^— ^— -^^^— ^— — — 
 
 „ c (100 X Gr) — 100 
 ib ~ Gr 
 
 when T.S. = the total solids and Gr the specific gravity of the 
 milk. 
 
 Example. — A sample of milk contains 12.85 per cent of milk 
 solids and has a specific gravity of 1.031. Required the specific 
 gravity of the milk solids. 
 
 12.85 I2 -85 * 
 
 x = -. r = — = 1.306. 
 
 I2 o (100 X 1.031) - 100 12.85-3.006 
 
 1-031 
 
 The specific gravity of the solids of normal milk varies be- 
 tween 1.25 and 1.34. It is not changed by watering the milk, 
 but is increased by removing the fat or adding skimmed milk. 
 A value above 1.32 is suspicious while a specific gravity of the 
 milk solids above 1.40 is regarded as conclusive evidence of 
 skimming. 
 
 BUTTER 
 
 General Statements. — Butter consists of the fat of milk, 
 together with a small percentage of water, salt, and curd. The 
 curd is made up principally of the casein of the milk. These 
 various ingredients are present in about the following propor- 
 tions : 
 
 Fat 78.00-90.0 per cent; average, 82 per cent. 
 
 Water 5.00-20.0 per cent; average, 12 per cent. 
 
 Salt. 0.40-15.0 per cent; average, 5 per cent. 
 
 Curd 0.11- 5.3 per cent; average, 1 per cent. 
 
ANALYTICAL METHODS 
 
 163 
 
 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. 
 
 The following may be taken as the probable composition 
 of normal butter-fat : * 
 
 Acid. 
 
 Per cent 
 Acid. 
 
 Per cent 
 Triglycerides. 
 
 Dioxystearic 
 
 I .OO 
 32-50 
 
 I-8 3 
 38.61 
 
 9.89 
 
 2-57 
 O.32 
 O.49 
 2.09 
 5-45 
 
 1.04 
 
 33-95 
 1. 91 
 
 40.5I 
 IO.44 
 
 2-73 
 0.34 
 O.53 
 2.32 
 6.23 
 
 Oleic 
 
 Stearic 
 
 Palmitic 
 
 Myristic 
 
 Laurie 
 
 Capric 
 
 Caprylic 
 
 Caproic 
 
 Butyric 
 
 Total 
 
 94-75 
 
 IOO . OO 
 
 
 According to this, the proportion of volatile acids in butter 
 (butyric, caproic, caprylic and capric acids) amounts to 8.35 per 
 cent. The amount of volatile acid in lard, for example, is about 
 0.1 percent. 
 
 The usual examination of butter consists in the examina- 
 tion of the butter-fat, in order to detect the presence of foreign 
 fats. Those commonly used for this purpose are lard, oleo- 
 margarine, and sometimes butter substitutes containing cocoanut 
 oil. 
 
 The term "oleomargarine" is usually applied to a mixture 
 of refined lard, "oleo oil," which is mainly the olein of beef fat, 
 and cottonseed oil. Ordinarily a small proportion of butter 
 is added and the product is generally churned with milk. 
 
 A comparatively recent form of butter substitute which 
 finds extensive use in some sections of the country is " process," 
 or "renovated," butter. The raw material, or "stock," used for 
 the manufacture of this consists of butter which cannot be sold 
 
 * Browne: /. Am. Chem. Soc, 1899, 807. 
 
164 AIR, WATER, AND FOOD 
 
 as butter either because of deterioration through rancidity or 
 molding or because, through carelessness on the part of the 
 makers, it possesses an unattractive appearance or flavor. The 
 chief recruiting-ground for this material is the country grocery 
 store. The fat, separated from the curd by melting and settling, 
 is aerated to remove disagreeable odors and leave it nearly 
 neutral. This is then emulsified with fresh milk which has 
 been inoculated with a bacterial culture, and the whole is chilled, 
 granulated, and churned. The butter is then worked and packed 
 for market in the usual manner. The character of the product 
 has much improved since the early days of the industry, the 
 best grades now approximating the lower grades of creamery 
 butter. 
 
 The "aroma" of butter seems to be connected with the decom- 
 position 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. 
 
 Analysis of Butter. — Apart from the examination of the 
 butter fat to detect the addition of foreign fats, butter itself 
 is often analyzed in order to determine variations in its con- 
 stituents from the normal, or the addition of deleterious 
 substances. 
 
 The Federal standard for butter describes it as "the clean, 
 non-rancid product made by gathering in any manner the fat 
 of fresh or ripened milk or cream into a mass, which also con- 
 tains a small portion of the other milk constituents, with or 
 without salt, and contains not less than eighty-two and five- 
 tenths (82.5) per cent of milk fat. By acts of Congress approved 
 August 2, 1886, and May 9, 1902, butter may also contain added 
 coloring matter." 
 
 The determinations usually made to ascertain whether the 
 
ANALYTICAL METHODS 165 
 
 butter is of standard quality are the water, fat, ash, curd, and 
 salt. Of these the first four can be made on the same weighed 
 sample, following in general the methods recommended by the 
 Association of Official Agricultural Chemists.* 
 
 The following method is simpler and gives results comparable 
 with the official methods: 
 
 Weigh about 2 grams of butter into a platinum Gooch cruci- 
 ble, half-filled with ignited fibrous asbestos, and dry it at ioo° C. 
 to constant weight. The loss in weight is the amount of water. 
 Then treat the crucible repeatedly with small portions of pe- 
 troleum 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 asbestos 
 is the ash. If desired, the salt may be washed out of the ash 
 and determined by titration with silver nitrate after neutraliz- 
 ing the solution with calcium carbonate. 
 
 Notes. — If the sample for analysis is to be taken from a 
 considerable quantity of butter, great care must be taken in 
 sampling, because the butter is usually not homogeneous in 
 composition and cannot be mixed by stirring. The best plan 
 is to take a fairly large sample of 100 to 200 grams or more, 
 melt it at the lowest possible temperature in a jar or wide- 
 mouthed glass-stoppered bottle and mix by violent shaking. 
 Then cool until sufficiently solid to prevent the separation of the 
 fat and water, taking especial care to shake the sample thor- 
 oughly during the cooling. 
 
 Rapid methods for the determination of water in butter have 
 been devised by Patrick f and Gray J especially for the exami- 
 nation of large numbers of samples. 
 
 Good butter should in general contain not less than the amount 
 
 * Bur. of Chem., Bull. 107 (Rev.), p. 123. 
 f /. Am. Chem. Soc., iooj, 11 26. 
 % Bur. Animal hid., Circ. 100. 
 
1 66 AIR, WATER, AND FOOD 
 
 of fat required by standard, not more than 2.0 per cent of curd, 
 and not over 16 per cent of water. 
 
 Salt. — If a direct determination of salt is desired, the fol- 
 lowing method, although tedious, will give satisfactory results: 
 
 Weigh 10 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 
 
 20 
 
 potassium chroma te as an indicator. 
 
 Preservatives. — About 50 grams of butter are mixed with 
 25 c.c. of chloroform in a separatory funnel, 100 c.c. of dilute 
 (0.1 per cent) sodium carbonate solution added, and the whole 
 mixed, avoiding violent shaking. After the separation of the 
 layers, which may be greatly aided by a suitable centrifuge, 
 the aqueous layer is examined for preservatives, especially for 
 boric, benzoic and salicylic acids, by the methods described on 
 pages 154 and 196. 
 
 Colors. — No methods are described for the detection of 
 colors in butter since these, being allowed, do not constitute 
 an adulteration. If it be desired to test for added color in oleo- 
 margarine, methods may be found in Allen's Commercial Organic 
 Analysis, 4th Ed., Vol. II, or in Leach's Food Analysis. 
 
 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, about two cubic inches, 
 in a small beaker placed on top of the water-bath so that the 
 temperature shall not rise above 50 to 6o°. After about fifteen 
 minutes the water, salt, and curd will have settled to the bottom. 
 (A better separation may be secured by dividing the melted 
 sample equally between two test-tubes and whirling them for 
 
ANALYTICAL METHODS 167 
 
 3 to 4 minutes in a centrifugal machine.) Place a bit of absorb- 
 ent 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 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 0.35 to 0.5 gram each into 300-c.c. 
 glass-stoppered bottles for determination of the iodine value. 
 In the case of the larger portions, weigh only to the nearest 
 milligram. 
 
 (1) Reichert-Meissl Number for Volatile Fatty Acids — Di- 
 rections. — 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 recently boiled distilled water which 
 has been cooled to about 50 degrees. The water should be added 
 slowly, a few cubic centimeters 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 degrees 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 degrees, re- 
 
1 68 AIR, WATER, AND FOOD 
 
 move the cork, and immediately attach the flask to the 
 condenser. 
 
 Distill no c.c. into a graduated flask in as nearly thirty min- 
 utes as possible. Thoroughly mix the distillate, pour the whole 
 of it through a dry filter, and titrate ioo c.c. of the mixed filtrate 
 
 N 
 with — sodium hydroxide, using phenolphthalein as an indicator. 
 10 
 
 Multiply the number of cubic centimeters of alkali used by 
 
 eleven-tenths, 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 c.c. 
 
 N 
 of the distillate require 27.4 c.c. of — NaOH, no c.c. would re- 
 
 10 
 
 quire 27.4 Xjj = 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. 
 
 Cocoanut oil gives a value of 6-8; other edible fats and oils 
 have a value usually less than 1. 
 
 Cocoanut oil is used, to some extent, as a substitute for butter 
 in confections and crackers, in cooking fats, and also in cocoa- 
 butter substitutes. Its presence is indicated by the Reichert- 
 Meissl number taken in connection with the saponification value, 
 that is, the number of milligrams of potassium hydroxide re- 
 quired to saponify one gram of the fat. (For a description of 
 the method of determining this see Lewkowitsch: Oils, Fats 
 and Waxes; or Gill: A Short Handbook of Oil Analysis.) The 
 Reichert-Meissl number is higher in butter fat than in cocoanut 
 oil, while the saponification value is lower. In pure butter fat 
 the value of the expression: 
 
 Saponification value — (Reichert-Meissl number — 200) varies 
 from 3.4 to 4.1; in pure cocoanut oil, it runs from 47 to 50.7.* 
 
 Another method of value in showing the presence of cocoanut 
 oil is the determination of the Polenske number f which repre- 
 
 * Juckenack and Pasternack: Ztschr. Nahr. Genussm., 7, 1904, 193. 
 f Polenske: Ztschr. Nahr. Genussm., 1904, 273. 
 
ANALYTICAL METHODS 169 
 
 sents the volatile fatty acids insoluble in water. This value for 
 butter is from 1 to 3; for cocoanut oil, from 16 to 18. Details 
 of the procedure, which it requires some experience to carry out 
 successfully, may be found in the original paper or in Leach's 
 Food Analysis, 3d ed., page 483. 
 
 The reactions involved in the Reichert-Meissl method may be 
 simply explained as follows: 
 
 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 may be expressed, 
 
 C 3 H5(C 3 H 7 COO)3 + 3 KOH = 3 C 3 H 7 COOK + C3H 5 (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: 
 
 C 3 H 7 COOH + C2H5OH = C 3 H 7 COOC 2 H 5 + H 2 0. 
 
 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 rapidly, 
 the soap may be decomposed with the liberation of the fatty 
 acids: C 3 H 7 COOK + H 2 = C 3 H 7 COOH + KOH. 
 
 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 dis- 
 tillate, 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 prescribed pro- 
 cedure with great care. 
 
 In Great Britain all determinations of the Reichert-Meissl 
 number, which are likely to lead to prosecutions under the Mar- 
 garine Act, must be made in a specified apparatus, the dimensions 
 of which are definitely stated and the procedure exactly defined.* 
 * Analyst, 25, 1900, 309. 
 
170 AIR, WATER, AND FOOD 
 
 Some of the errors in the Reichert-Meissl method may be 
 avoided, and the process materially shortened by carrying out 
 the saponification with glycerol and caustic soda as recommended 
 by Leffman and Beam.* The method is as follows: 
 
 Weigh 5 grams of the fat into a 250-c.c. round-bottomed 
 flask and add 20 c.c. of glycerol-soda solution.! Hold the flask 
 with tongs, and heat it directly over a flame until foaming ceases 
 and the mixture becomes perfectly clear, which ordinarily re- 
 quires about five minutes. Add to the clear soap solution 135 
 c.c. of water, adding it at first in very small portions to prevent 
 foaming. Finally add the pumice and sulphuric acid, as in the 
 Reichert-Meissl method, and distill without previous melting of 
 the fatty acids. 
 
 (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 1 c.c. of caustic potash 
 and 20 c.c. of 95 per cent alcohol. Cover 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 completely dissolved, add 10 c.c. of hydro- 
 chloric acid (sp. gr. 1.12), and heat the beaker in the water- 
 bath almost to boiling 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. If the filter paper is of good 
 texture and thoroughly wet beforehand, it will retain the fatty 
 acids completely. If, however, oily particles are noticed in the 
 
 * Analyst, 1891, 153. 
 
 t 20 c.c. of 50 per cent caustic soda solution to 180 c.c. of glycerol. 
 
ANALYTICAL METHODS 171 
 
 filtrate, cool it by adding pieces of ice, remove the solidified par- 
 ticles with a glass rod and transfer them to the filter. Cool the 
 funnel by plunging it into cold water, remove the filter, place it 
 in the weighing-beaker, and dry it at ioo° to constant weight. 
 The fat should be heated about an hour at first, then for periods 
 of about thirty 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) Determination of Iodine Value. — This method is based 
 on the fact that certain of the fatty acids, notably the " unsatu- 
 rated acids," as oleic acid, G7H33COOH, take up the halogens 
 with the formation of addition products. 
 
 Directions. — Dissolve the fat in the 300-c.c. bottles in 10 c.c. 
 
 of chloroform. Add 30 c.c. of the iodine solution from a pipette 
 
 or glass-stoppered burette, and allow the bottles to stand with 
 
 occasional shaking for thirty minutes. Add 10 c.c. of 20 per 
 
 cent potassium iodide solution and mix thoroughly, then 100 c.c. 
 
 N 
 of distilled water, and titrate the excess of iodine with — sodium 
 
 10 
 
 thiosulphate until the solution is faintly yellow. Add 2 to 3 c.c. 
 of starch solution and titrate to the disappearance of the blue 
 color. Toward the end of the titration shake the bottle vigor- 
 ously so that any iodine remaining in the chloroform may react 
 with the thiosulphate. Calculate the result in grams of iodine 
 absorbed by 100 grams of fat. This is called the Iodine 
 Number, or Iodine Value. 
 
 At the time of making the determination carry out two 
 " blanks" in exactly the same way except that no fat is used. 
 
 Standardization of the Thiosulphate Solution. — As this is not 
 permanent, its strength should be determined by means of the 
 standard potassium bichromate solution, 1 c.c. of which is 
 equivalent to 0.01 gram of iodine. 
 
 Measure 20 c.c. of the potassium bichromate from a pipette 
 
172 AIR, WATER, AND FOOD 
 
 into an Erlenmeyer flask. Add 5 c.c. of potassium iodide, 100 
 ex. of water, and 5 c.c. of strong hydrochloric acid. 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 disappears, leaving the sea- 
 green color of the chromium chloride. The iodine is liberated in 
 accordance with the following equation : 
 K 2 Cr 2 7 + 14 HC1 + 6 KI = 8 KC1 + 2 CrCl 3 + 7 H 2 + 6 I. 
 
 Calculation of Results. — Example. — From the standardi- 
 zation, 
 
 16.07 cx - thiosulphate = 20 c.c. bichromate = 0.200 gram I; 
 1 c.c. thiosulphate = 0.0125 gram I. 
 
 Also, from blank, 
 
 30 c.c. iodine solution = 63.60 c.c. thiosulphate. 
 
 If 44.85 c.c. thiosulphate were used to titrate the excess of 
 free iodine, 63.60 — 44.85 = 18.75 cx - * s the amount of thio- 
 sulphate equivalent to the iodine combined with the fat. If 
 0.3271 gram of fat were used, since 1 c.c. thiosulphate is equiva- 
 
 i £ • j- I ^-75 X 0.0125 w 
 
 lent to 0.012 s gram free iodine, — — X 100 = 71.66 
 
 0.3271 
 
 grams of iodine combined with 100 grams fat. 
 
 Notes. — The Iodine Number of butter fat varies between 26 
 and 38; of oleomargarine, between 60 and 75; of lard, between 
 46 and 70; of cottonseed oil, from 106 to no; and of cocoanut 
 oil, between 8 and 9.5. 
 
 The products formed by the action of iodine on the fats are 
 mainly addition products with a slight proportion of substituted 
 bodies. Thus the unsaturated olein, 
 
 (C 17 H33COO) 3 C 3 H5, 
 
 takes up six atoms of iodine, forming an addition product, 
 di-iodo-stearin, (Ci7H33l2COO) 3 C 3 H5. 
 
 The method in general use for determining the iodine value 
 of fats and oils has been that of Baron Hiibl,* an alcoholic solu- 
 
 * Ding. Poly. J., 253, 281; /. Soc. Chem. Ind., 3, 1884, 641. 
 
ANALYTICAL METHODS 1 73 
 
 tion of iodine and mercuric chloride being used as the reagent. 
 The method here described, due to Hanus,* has the advantage 
 that the solutions keep better, remaining practically unchanged 
 for several months, and that the action is about sixteen times 
 as rapid. For the fats and for oils with low iodine values, the 
 results are very close to the figures obtained by the Hiibl proc- 
 ess. If it is desired to carry out the determination by the 
 older method, directions can be found in any standard work on 
 the analysis of oils. 
 
 It should be noted that the " iodine solution" is a solution of 
 iodine bromide in glacial acetic acid, hence great care should be 
 taken that there is no change in temperature between the time 
 of measuring the solution of iodine for the blanks and for the de- 
 terminations, since the high coefficient of expansion of acetic 
 acid may cause a material error. 
 
 Further, the amount of fat taken for the analysis should be 
 such that only a portion of the iodine is absorbed, 60 to 70 per 
 cent being in excess. Care should also be taken to avoid vigor- 
 ous shaking of the glass-stoppered bottles until near the end of 
 the titration to prevent loss of iodine from the stopper. 
 
 (4) Refractive Index. — The determination of the refractive 
 index is especially valuable in the examination of butter, and for 
 that matter, in food analysis in general, owing to the rapidity 
 with which the test can be made and the fact that so little of the 
 substance is required. Various forms of refractometers are 
 used for the purpose, a fairly complete description of which 
 will be found in some of the larger works, such as Leach: Food 
 Inspection and Analysis; or Vaubel: Quantitative Bestimmung 
 organischer Verbindungen. The instrument having the widest 
 range is the Abbe refractometer, in which the index of re- 
 fraction is determined by measuring the total reflection pro- 
 duced by a very thin layer of the melted fat, placed between two 
 prisms of flint glass. This instrument, fitted with water- jacketed 
 prisms, is shown in Fig. 13. 
 
 Directions. — Revolve the whole instrument on the axis b until 
 
 * Ztschr. Unters. Nahr. u. Genussm., 4, 1901, 913. 
 
174 
 
 AIR, WATER, AND FOOD 
 
 it reaches the stop provided, then open the prism casing AB by 
 giving the pin v a half-turn (to the right). Be sure that the 
 prism surfaces are clean. If not, clean them carefully with a soft 
 cloth and a little alcohol. Place a few drops of the melted 
 
 Fig. 13. 
 
 sample directly on the surface of the prism and clamp the two 
 together again by turning the pin v in the opposite direction. 
 Now turn the instrument back (toward the observer) as far as 
 possible and bring the "critical line" into the field of vision of 
 the telescope. This is done by holding the sector 5 firmly with 
 the hand and revolving the double prism by means of the alidade 
 / until the field is divided into a light and a dark portion. If 
 
ANALYTICAL METHODS 
 
 175 
 
 the line is not sharp focus the ocular of the telescope. If it is 
 colored it is due to dispersion of the light by the liquid and 
 should be corrected by revolving the compensator T by the 
 milled screw M. The correction is made by a system of two re- 
 volving Amici prisms in the lower part of the telescope. Adjust 
 the critical line so that it falls on the intersection of the cross 
 hairs of the telescope. Observe the temperature by the ther- 
 mometer inserted in 
 the prism casing. In 
 the case of solid fats, 
 a sufficiently high 
 temperature should 
 be maintained by a 
 current of war m 
 water to keep the 
 sample well above its 
 melting point. A 
 temperature of 30 to 
 40 C. is usually suffi- 
 cient. Do not let the temperature rise above 70 or the prisms 
 may be injured. Read the index of refraction directly through 
 the small lens L, estimating the fourth decimal. Calculate the 
 value for the refractive index at 25 C. 
 
 Notes. — The principle on which the Abbe refractometer is 
 based will, perhaps, be more clearly understood by reference to 
 Fig. 14. 
 
 Let AB be the surface of separation between two media, of 
 which the upper is the rarer, and let a beam of light pass through 
 in the direction 10. It will be seen that as the light passes from 
 the denser to the rarer medium, the angle of refraction r will be 
 greater than the angle of incidence i. If the angle of incidence 
 be increased, then for a certain incident angle, the angle of re- 
 fraction will become 90 , that is, the refracted ray will coincide 
 with the dividing surface. For incident rays striking the sur- 
 face at a greater angle than this, the light will be totally reflected 
 and there will be no refracted ray. The angle of incidence at 
 
 Fig. 14. 
 
176 
 
 AIR, WATER, AND FOOD 
 
 which this occurs is known as the critical angle, 
 sin i 
 
 Then since n 
 
 sin r 
 
 sin 1 
 
 sin 1 
 
 sin 
 
 at the critical angle n 
 
 sin 90 1 
 
 That is, in passing from a denser to a rarer medium, the index of 
 
 refraction is equal to the sine of the angle of incidence for the 
 
 border line of total re- 
 
 flection. 
 
 In the Abbe refrac- 
 tometer the refractive 
 index of the liquid is 
 determined by measur- 
 ing the critical angle 
 for light passing into 
 it from a glass prism of 
 higher refractive index. The sine of 
 this angle is the index of refraction 
 of the liquid, referred to glass, and 
 this multiplied by the refractive in- 
 dex of the glass gives the index of 
 refraction of the liquid referred to air. 
 The divisions on the scale are pro- 
 portional to the sines of the angles 
 of incidence for total reflection, multi- 
 plied by 1.75, the refractive index of 
 the prism and, therefore, give directly 
 the refractive index of the substance 
 examined. Since the light must pass 
 from the denser to the rarer medium, 
 it is evident that the instrument is FlG - I S- 
 
 limited to liquids whose refractive indices are less than 1.75. 
 
 Fig. 15, from Browne's Handbook of Sugar Analysis, illus- 
 trates diagrammatically the passage of light through the in- 
 strument. The heavy line represents the border line of total 
 reflection, the light striking the surface AB at a less angle being 
 
ANALYTICAL METHODS 
 
 177 
 
 refracted, and illuminating the field of the telescope. The rays 
 which fall upon the surface at a greater angle are totally reflected, 
 leaving the corresponding portion of the telescopic field dark. 
 
 The index of refraction decreases with rising temperature. 
 With the common oils and fats, the change for each degree is 
 very nearly a constant, amounting to 0.000365. Leach and 
 Lythgoe * have devised a sliding scale by means of which the 
 temperature correction may be readily made without reference to 
 tables. 
 
 The values of tin for genuine butter lie between 1.4590 and 
 1.4620; for oleomargarine the values range from 1.4650 to 
 1.4700. 
 
 The correctness of the instrument should be tested by the 
 "test-plate" which comes with it, cementing it to the prism 
 with monobromnaphthalene, or the testing may be done more 
 conveniently with distilled water. The refractive index of water 
 at ordinary temperatures is given below: 
 
 Tempera- 
 
 Refractive 
 
 Tempera- 
 
 Refractive 
 
 ture, °c. 
 
 Index. 
 
 ture, °C. 
 
 Index. 
 
 18 
 
 1-3332 
 
 23 
 
 1-3327 
 
 19 
 
 I 3331 
 
 24 
 
 I.3326 
 
 20 
 
 1-3330 
 
 25 
 
 I-332S 
 
 21 
 
 1-3329 
 
 26 
 
 1-3324 
 
 22 
 
 1-3328 
 
 27 
 
 1-3323 
 
 Special Tests for Distinguishing Renovated Butter. — Spoon 
 Test or "Foam" Test. — Melt a piece of the sample as large as a 
 small chestnut in an ordinary tablespoon or a small tin dish. 
 Use a small flame and stir the melting fat with a splinter of wood 
 (such as a match) . Then increase the heat so that the fat shall 
 boil briskly, and stir thoroughly, not neglecting the outer edges, 
 several times during the boiling. 
 
 Oleomargarine and renovated butter boil noisily, usually 
 sputtering like a mixture of grease and water when boiled, and 
 
 * /. Am. Chem. Soc, 1904, 1193. 
 
178 AIR, WATER, AND FOOD 
 
 produce little or no foam. Genuine butter usually boils with 
 much less noise and produces an abundance of foam, often rising 
 over the sides of the dish or spoon when the latter is removed 
 temporarily from the flame. The difference in regard to the 
 foam is very marked. 
 
 Note also the appearance of the particles of curd after the 
 boiling. With genuine butter these will be very small and 
 finely divided, hardly noticeable in fact, while with oleomargarine 
 and renovated butter the curd gathers in much larger masses 
 or lumps. 
 
 Notes. — This simple method is of value for giving a quick 
 decision regarding a sample, and is especially useful for the 
 detection of renovated butter. The differences in the compo- 
 sition of butter-fat brought about by renovation are so slight 
 that chemical methods are here of no avail. 
 
 The spoon test, however, will distinguish in the great majority 
 of cases between genuine butter on the one hand and oleo- 
 margarine and renovated butter on the other; the index of 
 refraction or the chemical methods just described readily dis- 
 tinguish between the two latter. 
 
 In genuine butter the curd is somewhat different in compo- 
 sition from that of renovated butter or oleomargarine in that it 
 consists largely of the milk proteins that are insoluble in water, 
 and hence accompany the separated cream. The curd of reno- 
 vated butter or oleomargarine, on the other hand, comes from 
 the proteins of the milk added directly in the process of manu- 
 facture, and consists mainly of coagulated casein. Hence its 
 different appearance in the test. 
 
 The crackling and sputtering of the fat in the case of oleo- 
 margarine and renovated butter are due to the fact that in the 
 process of manufacture of these the melted fat is sprayed into 
 ice-water, and the cooled particles enclose some water. 
 
 Microscopic Examination. — Pure, fresh butter is not ordi- 
 narily crystalline in structure. Butter which has been melted, 
 however, and fats which have been liquefied and allowed to cool 
 slowly show a distinct crystalline structure, especially by polar- 
 
ANALYTICAL METHODS 1 79 
 
 ized light. If only fresh butter 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, however, it is most useful in making comparative exami- 
 nations of samples which have been subjected to the same 
 conditions. 
 
 About the most that can be said is that if a small bit, about 
 the size of a pin-head, of the fresh, unmelted sample, is taken 
 from the center of the mass and pressed out on a slide by gentle 
 pressure on the cover glass, it ought to show a fairly uniform 
 field if examined with a one-sixth objective, using polarized 
 light and a selenite plate. Other fats melted and cooled, and 
 mixed with butter, generally show a crystalline structure and a 
 variegated color with the selenite plate. 
 
 In the case of renovated butter, however, there is a distinct 
 difference to be noted in the appearance of the field. With 
 genuine butter the field is much more clear and free from opaque 
 masses of curd than with renovated butter. When the slide is 
 examined by reflected light, turning the mirror so as not to pass 
 light through the slide, these opaque masses in the case of reno- 
 vated butter show strikingly as white masses against a dark 
 background. 
 
 CEREALS 
 
 The great importance of cereal food in the diet may be 
 gathered from the fact that dietary studies among a large num- 
 ber of American families have shown that about three-fourths 
 of the vegetable protein, one-half of the carbohydrates, and 
 seven-eighths of the vegetable fat are supplied by the cereals. 
 The reason for such an extensive use of the cereals lies in the 
 fact that, besides being cheap and easily grown, they contain 
 unusually large proportions of nutriment with a very small pro- 
 portion of refuse. They are readily prepared for the table, are 
 palatable and digestible. In distinction from the two classes of 
 food materials already considered, they are in a dry form, and 
 not liable to rapid change by micro-organisms. 
 
180 AIR, WATER, AND FOOD 
 
 Prepared breakfast foods may be taken as typical and inter- 
 esting cereal products, and since many of these are somewhat 
 modified from their original composition by cooking or by 
 treatment with malt, the form in which the carbohydrates are 
 present is of almost equal importance with the determination of 
 nitrogen. 
 
 The fact that in the breakfast cereals the process of manu- 
 facture has in no way increased their actual food value over the 
 grains from which they were prepared, as pointed out in Chapter 
 VIII, is emphasized by the figures in the accompanying table in 
 which some of the most widely-used preparations are compared 
 with the original grains. It will be observed that practically the 
 only change is in the solubility of the carbohydrates, the starch 
 being changed in part to dextrin. In the case of the malted food, 
 the change may go even farther, and a greater or less amount of 
 reducing sugar, principally maltose, be formed. 
 
 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 ioo° C. for five hours. On account of the 
 ready absorption of moisture by the dried sample, the use of 
 clipped watch-glasses will be found advantageous. 
 
 Note. — With some substances drying in a current of hydro- 
 gen 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 platinum 
 dish, such as is used for the determination of solids in milk, and 
 char it carefully. Ignite at a very low red heat until the ash is 
 white, preferably in a mufHe. 
 
 Notes. — 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. 
 
 Some cereals, such as whole wheat and barley, will act de- 
 structively on platinum dishes, on account of the phosphates 
 present, but can be ignited safely in platinum in the mufHe. 
 
ANALYTICAL METHODS 
 
 181 
 
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1 82 AIR, WATER, AND FOOD 
 
 Fat: Ether Extract. — Directions. — Place the residue from 
 the determination of moisture, as described above, in a porous 
 paper cup and extract it with pure anhydrous ether for sixteen 
 hours, using the Soxhlet extractor and electric heater as de- 
 scribed on page 141. Evaporate off the ether and dry the 
 residual fat at the temperature of boiling water to constant 
 weight. 
 
 Note. — The ether extract of cereals is not pure fat but may 
 contain more or less coloring matter or resins. Petroleum ether 
 can be used for the extraction, giving results not essentially 
 different from those obtained with anhydrous ethyl ether. 
 
 Total Protein: Determination of Nitrogen by the Kjeldahl 
 Process.* — This method is based upon the decomposition of 
 the nitrogenous material by boiling with strong sulphuric acid. 
 The carbon and hydrogen are oxidized to carbon dioxide and 
 water, a portion of the sulphuric acid being reduced to sulphur 
 dioxide. The nitrogen is left as ammonium sulphate from 
 which the ammonia is liberated by potash or soda and distilled 
 into a known excess of standard acid. The time of digestion 
 can be materially shortened by the use of substances like mer- 
 cury or potassium sulphate which assist the oxidation or raise 
 the boiling-point of the acid. 
 
 Directions. — Transfer about 0.5 gram of the finely divided 
 substance from a weighing-tube to a pear-shaped digestion flask, 
 add 10 c.c. of concentrated sulphuric acid free from nitrogen, 
 and 0.2 gram (three small drops) 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 at least an 
 hour after it becomes colorless. Allow the flask to cool for a 
 minute or two, and add a few crystals of potassium permanganate 
 until the liquid has acquired a slight green or purple color. 
 
 N 
 Measure 25 c.c. of — acid from a burette into a 300-c.c. 
 10 
 
 * Ztschr. anal. Chetn., 22, 1883, 366. 
 
ANALYTICAL METHODS 183 
 
 Erlenmeyer flask and place the condenser-tip beneath the 
 
 surface of the liquid, adding a little water, if necessary, to seal 
 
 it. 
 
 Transfer the digestate with several small portions of distilled 
 
 water to the distilling flask of the apparatus, add 20 c.c. of 
 
 potassium sulphide solution, and connect the flask with the 
 
 condenser. Add 50 c.c. of caustic potash through the separa- 
 
 tory funnel, and distill off the ammonia by steam. When 200 
 
 c.c. have distilled over, remove the collecting-flask, after rinsing 
 
 off the condenser-tip with distilled water, and titrate the excess 
 
 N 
 of acid with — sodium hydroxide, using methyl orange or 
 10 
 
 cochineal as indicator. If using new reagents, a blank deter- 
 mination should be made with 0.5 gram of cane-sugar in order 
 to reduce any nitrates present 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. 
 
 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 unnecessary in 
 the majority of analyses. 
 
 The addition of potassium sulphide before distilling is to pre- 
 cipitate the mercury and thus prevent the formation of non- 
 volatile mercur-ammonium compounds. 
 
 The Kjeldahl process in the form outlined above is not ap- 
 plicable to the determination of nitrogen in the form of nitrates. 
 In order to render it of more general application various modi- 
 fications 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 sulphuric acid, being con- 
 verted 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 ammonium sulphate by the 
 
 * U. S. Dept. Agr., Bull. 16, 1887, 51. 
 
184 AIR, WATER, AND FOOD 
 
 heating with sulphuric acid, the use of mercury being absolutely 
 necessary in this case to secure the complete transformation. It 
 is true also that certain other nitrogenous bodies, notably the 
 alkaloids and certain organic bases, do not yield all their nitro- 
 gen to the Kjeldahl process without modifications which com- 
 plicate the method. For a discussion of the efficiency of these 
 various modifications the student is referred to a paper by 
 Sherman and Falk.* In the case of cereals, however, and with 
 the majority of food products, the simpler method outlined will 
 prove entirely satisfactory. 
 
 The per cent of proteids may be found by multiplying the 
 per cent of nitrogen by an appropriate factor, the one in general 
 use being 6.25. Recent work has shown, however, that most 
 of the proteids of cereals contain more than 16 per cent of 
 nitrogen, so that the factor 6.25 gives results that are too high. 
 Because all the older work was calculated on this factor, it is 
 still generally used, nevertheless. 
 
 Kjeldahl-Gunning Method. — The Gunning method can be 
 used in all cases where the Kjeldahl- Wilfarth modification, just 
 described, is employed, and in some ways it is simpler. 
 
 The digestion and distillation are carried out as described on 
 page 182, using the same amount of sample, together with 20 c.c. 
 of concentrated sulphuric acid and 10 grams of powdered potas- 
 sium sulphate. No mercury and, consequently, no potassium 
 sulphide is used. 100 c.c. of the potash should be added in- 
 stead of 50. 
 
 Note. — The potassium sulphate is added to raise the boiling 
 point of the sulphuric acid and thus shorten the time required 
 for the digestion. 
 
 Carbohydrates. — The total carbohydrates, often stated in 
 analyses as " nitrogen-free extract," may be readily obtained by 
 subtracting from 100 the sum of the percentages of the other 
 constituents, viz., moisture, ash, ether extract, and nitrogenous 
 bodies. In many cases, however, especially with the cooked or 
 treated cereals and with such classes of cereal preparations as 
 
 * /. Am. Chem. Soc, 1904, 1469. 
 
ANALYTICAL METHODS 185 
 
 infant or invalid foods, a further study of the carbohydrates is 
 desirable. These are made up of two general classes : (a) soluble 
 carbohydrates, including sugars, as sucrose, dextrose and maltose, 
 dextrin and soluble starch, by the latter term being meant starch 
 which is soluble in water but still gives the characteristic blue 
 color with iodine, in distinction from some of the more com- 
 pletely broken-down forms like dextrin, which no longer give 
 blue or purple colors with iodine; (b) insoluble carbohydrates, in- 
 cluding starch, pentosans, lignin bodies, and cellulose. The 
 three latter occur chiefly in the husk or envelope of the grain 
 or in the woody fiber of the plant. The pentosans or gums are 
 distinguished from one another by the formation of specific 
 sugars upon hydrolysis with acids. For ordinary analytical 
 purposes it is sufficient to determine the lignin and cellulose to- 
 gether as " crude fiber." Since the exact procedure to be fol- 
 lowed in the determination of the carbohydrates varies largely 
 with each specific case, only a general outline can be presented 
 here. 
 
 Sugars. — The finely ground material, previously dried and 
 extracted with ether for the removal of crude fat, is extracted 
 with 85 per cent alcohol. In the extract the reducing sugars 
 may be determined by means of Fehling's solution as described 
 on page 145, and the sucrose determined in the same way after 
 inversion with hydrochloric acid. 
 
 Dextrin and Soluble Starch. — The residue from the extrac- 
 tion of the sugars is treated for eighteen to twenty-four hours 
 with water at laboratory temperature with frequent agitation, 
 made up to definite volume, and filtered. This may be tested 
 with iodine, and if no blue color is produced, evaporated to small 
 volume, and the dextrin converted to dextrose by dilute hydro- 
 chloric acid and determined by Fehling's solution. In some few 
 cases, however, a blue color with iodine may indicate the presence 
 of soluble starch, in which case an aliquot part of the filtrate may 
 be treated with an excess of barium hydroxide to precipitate 
 the starch. In the filtrate from this precipitate the dextrin is 
 determined by inversion and copper reduction as before. The 
 
186 AIR, WATER, AND FOOD 
 
 difference between the dextrin thus found and the first deter- 
 mination gives the soluble starch. 
 
 Starch. — This may be determined in the residue insoluble in 
 cold water by digesting it with malt extract, and determining the 
 dextrose after hydrolysis with dilute acid. It is more common, 
 however, to determine the starch and other insoluble carbo- 
 hydrates directly on the original material. 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 determined 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, especially the pentosans, become soluble under these 
 conditions and the results are too high. In such cases, the 
 starch is brought into solution by treatment with diastase or by 
 heating with water under pressure. The results obtained by 
 direct acid hydrolysis, however, in cases where the highest 
 accuracy is not required, may be sufficient and the method is 
 much quicker and easier of execution than the digestion with 
 diastase. 
 
 Direct Acid Hydrolysis. — Directions. — Weigh out from 2 to 
 5 grams of the sample, depending upon the amount of starch 
 present, and wash on a filter with five successive portions of 
 10 c.c. each of ether. Allow the ether to evaporate from the 
 residue and then wash it with 10 per cent alcohol until free from 
 soluble carbohydrates. 150 c.c. of the dilute alcohol is generally 
 sufficient, but if much reducing sugar or dextrin is present, as 
 may be the case with malted cereals, more will be necessary. 
 Wash the residue from the filter with 200 c.c. of water into a 
 500 c.c. graduated flask, add 20 c.c. of hydrochloric acid, sp. gr. 
 1. 1 2 5, place a funnel in the neck of the flask to retard evapo- 
 ration, and heat in a boiling water-bath for two and one-half 
 hours. Cool, nearly neutralize with sodium hydroxide and 
 make up to 500 c.c. Filter, and determine dextrose in an 
 aliquot portion, 25 or 50 c.c. of the filtrate, using the method de- 
 
ANALYTICAL METHODS 187 
 
 scribed on page 145. Convert dextrose to starch by the factor 
 0.9. 
 
 Note. — The washing to remove soluble carbohydrates is per- 
 formed with dilute alcohol rather than with water, because the 
 former is less likely to carry starch granules through the paper. 
 The sugar solution when added to the Fehling's solution should 
 be clear and only faintly acid. It should, in general, contain 
 not more than 0.5 per cent of reducing sugar. 
 
 Determination with Diastase. — Directions. — Treat 2 to 5 
 grams of the sample with ether and dilute alcohol, as in the 
 previous method, and wash the residue into a 250-c.c. flask 
 with 50 c.c. of water. Heat slowly to boiling, or immerse the 
 flask in boiling water, until the starch gelatinizes, stirring con- 
 stantly to prevent the formation of lumps. Cool to 55 C, add 
 20 to 40 c.c. of malt extract, and keep the solution within two 
 degrees of the stated temperature for an hour or until the solu- 
 tion no longer gives the starch reaction with iodine under the 
 microscope. In either case, heat the solution again to boiling 
 to gelatinize any remaining starch granules, test again and if 
 starch is found, cool to 55 C, and treat as before, using a 
 fresh portion of malt extract. Continue this treatment until, 
 when carefully examined under the microscope, a drop of the 
 solution fails to give the iodine reaction for starch. Cool, 
 make up to 250 c.c. and filter through a dry filter. Transfer 
 200 c.c. of the nitrate to a 500-c.c. graduated flask, add 20 c.c. 
 of hydrochloric acid, sp. gr. 1.125, and carry out the determina- 
 tion as described in the preceding method. 
 
 A blank determination must be carried through, using 50 c.c. 
 of water and exactly the same amount of malt extract as used in 
 the regular procedure, in order to correct for the cupric reducing 
 power of the malt extract. 
 
 Malt Extract. — Treat 40 grams of fresh coarsely ground malt 
 several hours with 200 c.c. of water, shaking occasionally. 
 Filter and add a few drops of chloroform to prevent the growth 
 of molds. 
 
 Notes. — The action of the diastase on the gelatinized starch 
 
1 88 AIR, WATER, AND FOOD 
 
 is to convert it into maltose and dextrin, that is, into soluble 
 bodies that can be separated by filtration from the pentosans 
 and other carbohydrates that give the high results in the direct 
 acid method. By the action of acid (hydrolysis) the maltose and 
 dextrin are converted to dextrose. 
 
 The determination should, if possible, be carried through 
 without interruption. In case this cannot be done, salicylic acid 
 may be used to prevent fermentation, not adding it, however, 
 until after the digestion with diastase. 
 
 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 illustration. 
 When possible, however, it is preferable to use the freshly pre- 
 pared malt extract, as the prepared diastase, made at different 
 times and from separate portions of malt, may show great differ- 
 ences in hydrolytic power. 
 
 It is sometimes convenient to use freshly collected saliva, 
 this being free from carbohydrate. In this case, the digestion 
 should be carried out at 38 C. instead of 55 C. 
 
 Crude Fibre. — The Weende method, the one adopted by the 
 Association of Official Agricultural Chemists, is based on the 
 assumption that the starch and other digestible carbohydrates 
 and protein will be removed from the cereal by successive di- 
 gestion at a boiling temperature with acid and alkali of a definite 
 strength. The complex body thus obtained is not a definite 
 chemical compound, but may be considered as being composed 
 largely of cellulose. 
 
 Use 2 grams of the finely-ground sample and wash on a filter 
 with 5 portions of 10 c.c. each of ether. (The residue from the 
 determination of " ether extract" can be used if desired.) 
 
 Transfer the washed material to a 500-c.c. Erlenmeyer flask, 
 add 200 c.c. of boiling 1.25 per cent sulphuric acid, place a 
 funnel in the neck of the flask and boil gently for 30 minutes. 
 Filter on a ribbed filter and wash with several portions of boiling 
 water. Transfer the precipitate by means of 200 c.c. of boiling 
 1.25 per cent sodium hydroxide in a small wash-bottle to the 
 
ANALYTICAL METHODS 189 
 
 same 500-c.c. Erlenmeyer flask, and boil again gently for 30 
 minutes. 
 
 Filter on ignited asbestos in a Gooch crucible, wash with 
 boiling water until free from alkali, then with 10 c.c. of alcohol, 
 and finally with 10 c.c. of ether. Dry at the temperature of 
 boiling water to constant weight. Ignite carefully at first, then 
 at a low red heat until the organic matter is destroyed. Calcu- 
 late the loss on ignition as " crude fibre." 
 
 Note. — The filtration will be found to proceed fairly rapidly 
 if the solution is filtered hot and care is taken to keep the residue 
 from the filter as long as possible. 
 
 The sulphuric acid and sodium hydroxide should be carefully 
 prepared and the strength determined by titration. 
 
 Examination of Malted Cereals. — The relation of the carbo- 
 hydrates in a malted cereal, which ordinarily consist of maltose, 
 dextrin and starch, may be readily learned by the following 
 simple analytical scheme, due to Sherman.* 
 
 Directions. — Mix 5 grams of the ground sample with 125 c.c. 
 of cold water in a 250-c.c. graduated flask and allow it to stand 
 at room temperature for an hour, shaking frequently. Make 
 up to the mark, mix and filter through a dry filter. Determine 
 the reducing sugar in 25 c.c. of the filtrate as described on page 
 145, and calculate as maltose in the original sample. Measure 
 50 c.c. of the same filtrate into a 100-c.c. flask, add 5 c.c. of 
 hydrochloric acid (sp. gr. 1.12), and hydrolyze as directed on 
 page 186. Filter and determine the dextrose in the filtrate as 
 on page 145. Subtract the amount due to maltose and calculate 
 the remainder to dextrin by multiplying by 0.9. 
 
 Treat another portion of the original sample as described un- 
 der the determination of starch by acid hydrolysis, page 186, 
 without, however, extracting the soluble carbohydrates. From 
 the dextrose found subtract that given by dextrin and maltose 
 and calculate the remainder to starch. 
 
 Notes. — The presence of undissolved material in the flask 
 when diluted to volume renders the result somewhat inaccurate, 
 
 * Methods of Organic Analysis, 2d Ed., p. 341. 
 
190 AIR, WATER, AND FOOD 
 
 and the possible presence of other reducing sugars than maltose 
 introduces error, but the results are sufficiently close for com- 
 parative tests. 
 
 Examination of Fermented Liquors 
 wine 
 
 General Statements. — The object of a wine analysis is ordi- 
 narily to determine whether or not a wine is pure and un- 
 adulterated, or whether it has been properly made. Special 
 works furnish sufficient information concerning processes of 
 manufacture, and it is essential to know here only the general 
 composition of the grape- juice or "must" and how, by the 
 natural process of fermentation, this may be altered in the 
 finished product. 
 
 The "must" contains sugars (mainly dextrose); dextrin; 
 organic acids and salts, mainly tartaric and malic acids; salts of 
 inorganic acids, chiefly phosphates, sulphates, and chlorides. 
 Various extractive matters, which largely affect the color and flavor 
 of the wine, together with a little tannin and albuminous sub- 
 stances, are also present. The wine will contain, then, besides 
 water, the following: Alcohol, glycerine, frequently some sugar 
 that has escaped fermentation, ethers, which determine largely 
 the "bouquet" of the wine, and more or less of the acids, salts, 
 coloring and extractive matters of the must, together with vary- 
 ing amounts of carbonic, acetic, and succinic acids. 
 
 According to differences in their composition, wines may be 
 divided into various classes, such as "dry" wines, which contain 
 very little sugar, as distinguished from the sweet wines, in which 
 a notable quantity of sugar has escaped fermentation, or to 
 which an addition of sugar has been made subsequent to the 
 main fermentation. Or they may be divided according to the 
 content of alcohol into natural wines and those fortified by ad- 
 dition of alcohol, as port, sherry, and madeira. 
 
 The composition of the wine may be changed, moreover, by 
 the various methods which are used for its "improvement," 
 
ANALYTICAL METHODS 191 
 
 such as fortification already mentioned, plastering, petiotization, 
 etc. Information regarding these methods will be found in 
 some of the larger works mentioned in the bibliography. 
 
 Determinations of value in judging the purity of wine are 
 alcohol, glycerine, extract, ash, total and volatile acids. The 
 actual percentages of these substances are not of so great value as 
 certain relations between them, such as the ratio of ash to extract, 
 extract to alcohol, alcohol to glycerine, alcohol to acids, and 
 volatile to total acids. Examination for preservatives and for- 
 eign coloring matters should also be made. It should, perhaps, be 
 stated that the analytical procedure given here is to furnish 
 practice in the examination of a fermented food product, and is 
 by no means as thorough as might be needed to judge the quality 
 or genuineness of a wine. 
 
 Specific Gravity. — This is to be taken by means of the 
 pyknometer at i5°.5 C. 
 
 Notes. — Where the specific gravity of the sample is known, 
 the various portions taken for analysis can be more conven- 
 iently measured than weighed. The results can be calculated 
 to per cent by weight by dividing the results expressed as grams 
 per 100 c.c. by the specific gravity. 
 
 Effervescing wines should, before analysis, be vigorously 
 shaken in a large flask to hasten the escape of carbon dioxide. 
 The liquid may then be poured from under the foam into an- 
 other vessel. 
 
 Alcohol. — Principle. — The alcohol is obtained freed from 
 everything but water, and its amount determined by ascertain- 
 ing the specific gravity of the mixture, and taking the per cent 
 from the tables. 
 
 Directions. — Measure (or weigh) 100 c.c. of the wine into a 
 500-c.c. round-bottomed flask. Add 50 c.c. of water and if the 
 wine is very acid a small pinch of precipitated calcium carbon- 
 ate. With most wines this addition will not be necessary. 
 Distill about 95 c.c. into a 100-c.c. graduated flask. Fill to the 
 mark with distilled water, mix thoroughly, and take the specific 
 gravity of the distillate at 15.5 C. with a pyknometer. The per- 
 
192 AIR, WATER, AND FOOD 
 
 centage of absolute alcohol by volume corresponding to the 
 observed density will be found in Table X, page 217. 
 
 To find the alcohol by weight in the sample, multiply the per 
 cent of alcohol by weight in the distillate as taken from the table, 
 by the weight of the distillate and divide the result by the 
 weight of the sample used. 
 
 Notes. — The addition of calcium carbonate is to prevent the 
 distillation of acetic acid. A certain amount of volatile ethers 
 may also pass over into the distillate, but it is so slight that its 
 influence may be neglected. 
 
 Normal wines ordinarily contain between 4.5 and 12 per cent of 
 alcohol except in the case of "fortified" wines, where the amount 
 may be even 20 per cent. Fermentation does not yield more 
 than about 14 per cent of alcohol. 
 
 Extract. — The method to be employed depends on the pro- 
 portion of extract. A preliminary calculation should be made 
 by the aid of the formula 
 
 x = 1 -j- d — d f , 
 where x is the specific gravity of the dealcoholized wine, d the 
 specific gravity of the wine, and d r the specific gravity of the 
 distillate obtained in the determination of alcohol. The value 
 for x is found from Table XI, page 220. 
 
 Dry Wines. — (Having an extract content of less than 3 per 
 cent.) Evaporate 50 c.c. on the water-bath to a sirupy con- 
 sistency in a flat-bottomed platinum dish. Heat the residue in 
 the oven at ioo° C. for two hours and a half, cool in a desiccator 
 and weigh. 
 
 Sweet Wines. — When the extract content is between 3 and 
 6 per cent treat 25 c.c. of the sample as described under dry 
 wines. When the amount of extract exceeds 6 per cent it is best 
 to accept the result found from the table and not to determine 
 it gravimetrically. 
 
 Notes. — The gravimetric determination will be inaccurate 
 with wines high in extract on account of the serious error caused 
 by drying levulose at high temperatures. The figures in the 
 table are based on determinations made at 75 C. in vacuo. 
 
ANALYTICAL METHODS 193 
 
 Wine made from the juice of ripe grapes rarely contains less 
 than 1.5 per cent of extract in the case of white wines and about 
 2.0 per cent in the case of red wines. The amount of extract 
 decreases of course with age. 
 
 Alcohol-extract Ratio. — The municipal laboratory of Paris 
 considers a wine " fortified" if the alcohol exceeds 4.5 times the 
 extract for red wines and 6.5 for white wines. The extract and 
 alcohol should both be expressed in per cent by weight. The 
 amount of added alcohol is calculated by the municipal labora- 
 tory by subtracting the " natural" alcohol (extract X 4.5 or 6.5) 
 from the total alcohol. 
 
 Ash. — Ignite the residue from the extract determination as 
 described on page 180. 
 
 Note. — The amount of ash in a natural wine averages about 
 10 per cent of the extract, varying ordinarily between 0.14 per 
 cent and 0.35 per cent. 
 
 Glycerine. — The determination of glycerine, and the ratio 
 of glycerine to alcohol is of much value in judging the purity of 
 a wine. The determination of the glycerine, however, is rather 
 difficult and requires some little experience in order to obtain 
 good results. The official method of the Association of Agri- 
 cultural Chemists will be found in Bur. of Chem., Bull. 107, 
 (Rev. Ed.), p. 83. A more accurate modification, however, is 
 that of Ross {Bull. 132, p. 85). 
 
 Free Acids: Total Acidity Calculated as Tartaric Acid. — 
 
 Measure 25 c.c. of the wine into a small beaker, heat just below 
 
 N 
 the boiling point to expel carbon dioxide, and titrate with — 
 
 10 
 
 sodium hydroxide and phenolphthalein. In the case of red 
 
 wines use delicate red litmus paper, taking the end-point when 
 
 a drop of the liquid placed upon the 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. 
 
194 AIR, WATER, AND FOOD 
 
 Volatile Acids Calculated as Acetic Acid. — Measure 50 c.c. 
 
 of wine into a 300-c.c. flask provided with a cork having two 
 
 perforations. One is fitted with a tube 6 mm. in diameter and 
 
 blown out to a bulb 40 mm. in diameter a short distance above 
 
 the cork; this tube is connected with a condenser. 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 containing water. Heat both 
 
 flasks to boiling; then lower the flame under that containing the 
 
 wine, adjusting the flame so that the volume of liquid remains 
 
 constant, and continue the distillation by means of steam until 200 
 
 N 
 c.c. have distilled. Titrate the distillate with — ■ sodium hydrox- 
 
 10 
 
 ide, using phenolphthalein as an indicator. Calculate the results 
 
 N 
 as acetic acid. One c.c. — sodium hydroxide = 0.0060 gram 
 
 of acetic acid. 
 
 Hortvet * has described a compact self-contained apparatus 
 for determining the fixed and volatile acids in which the wine is 
 surrounded by boiling water while the steam is being passed 
 through, giving excellent results. 
 
 Fixed Acids Calculated as Tartaric Acid. — These may be 
 found by calculating the volatile acids as tartaric and sub- 
 tracting the result from the total tartaric acid found by direct 
 titration. 
 
 Note. — The total acids in a wine vary usually between 0.45 
 per cent and 1.5 per cent. The acid content is frequently 
 diminished by aging or by the separation of cream of tartar. 
 The volatile acid should, in general, not be over 0.12 to 0.16 
 per cent, depending upon the age of the wine. A wine properly 
 made should not have the volatile acid, estimated as acetic, ex- 
 ceed one-fourth of the total free acid, calculated as tartaric. 
 
 Coloring Matters: Detection of Coal-tar Dyes.j — Fifty c.c. 
 of the sample are diluted to 100 c.c. with water, filtered if neces- 
 
 * /. Ind. Eng. Chem., 1910, 31. 
 
 f Sostegni and Carpentieri: Ztschr. anal. Chem., 35, 1896, 397. 
 
ANALYTICAL METHODS 195 
 
 sary, faintly acidified with hydrochloric or acetic acid, and a 
 piece of white woolen cloth, which has been thoroughly washed 
 with hot water, is immersed in the solution and boiled for five to 
 ten minutes. The cloth is then removed and thoroughly washed 
 with boiling water, and boiled in a dilute solution of ammonia 
 (1 : 50). With some of the dyes the color is stripped from the 
 wool quite readily; with others it is necessary to boil for some 
 time. The wool is removed, the ammoniacal solution made 
 faintly acid with hydrochloric acid, and another piece of white 
 wool is immersed and again boiled. This second dyeing fixes 
 coal-tar dyes on the fibre, but fruit and vegetable colors remain 
 on the first piece of wool. 
 
 Notes. — It is absolutely necessary that the second dyeing 
 should be made, as some of the coal-tar dyes will dye a dirty 
 orange in the first acid bath which might be easily passed for 
 vegetable color but on treatment in alkaline bath and second 
 acid bath becomes a bright pink. 
 
 Excess of acid should be avoided since some of the colors do 
 not dye readily in strongly acid solution. 
 
 Another advantage in the second dyeing is that if a large 
 piece of woolen cloth is used in the first dyeing, and a small 
 piece in the second dyeing, small amounts of coloring matter 
 can be brought out much more decidedly in the second dyeing, 
 where practically all of the vegetable coloring matter has been 
 excluded. 
 
 Several colors which are not coal-tar dyes, notably archil and 
 archil derivatives, give reactions by this method and are liable 
 to be confused with coal-tar colors. For hints as to the method 
 for detecting these reference may be made to Bulletin 107, 
 Bureau of Chemistry, page 190. 
 
 The further separation and identification of the artificial 
 colors is too difficult a matter to be taken up here. The student 
 is referred for information on this point to the following: Mulli- 
 ken: The Identification of Commercial Dyestuffs; Loomis: 
 Circular 63, Bureau of Chemistry; Allen: Commercial Organic 
 
196 AIR, WATER, AND FOOD 
 
 Analysis, 4th Ed., Vol. V; Green and others*: The Identi- 
 fication of Dyestuffs on Animal Fibres. 
 
 Preservatives. — The preservatives to be sought generally in 
 wines are salicylic and benzoic acids and their salts. Sulphurous 
 acid and sulphites are also used. For methods of detecting 
 other substances less commonly employed, such as abrastol, beta- 
 naphthol, etc., reference may be made to Bulletin 107 of the 
 Bureau of Chemistry. Boric acid is occasionally used, but since 
 a small amount of it is normally present in wines, tests, to be 
 of value, should be quantitative. 
 
 Salicylic Acid. — Acidify about 50 c.c. of the wine with 5 c.c. 
 of dilute (1 -.3) sulphuric acid and extract in a separatory fun- 
 nel with 25 c.c. of ether. Draw off the lower layer, wash the 
 ether twice with water, using 10 c.c. each time and finally evapo- 
 rate the ether in a porcelain dish at room temperature. To the 
 residue in the dish add 2 to 3 drops of very dilute ferric chloride 
 or better ferric alum solution (App. B). A deep purple or violet 
 color indicates salicylic acid. 
 
 Notes. — Not more than 50 c.c. should be used for the test, 
 since a trace of salicylic acid seems normally present in some 
 wines. 
 
 The washing with water is to free the ether from traces of 
 sulphuric acid which interferes with the development of the 
 violet color. 
 
 Care should be exercised in making the extraction with ether 
 not to shake the separatory funnel too violently, since a trouble- 
 some emulsion may result. 
 
 Benzoic Acid.\ — Acidify about 100 c.c. of wine with sulphuric 
 acid, extract with ether, and evaporate the ethereal solution as 
 in the detection of salicylic acid. Treat the residue with 2 or 
 3 c.c. of strong sulphuric acid. Heat till white fumes appear; 
 organic matter is charred and benzoic acid is converted into 
 sulpho-benzoic acid. A few crystals of ammonium nitrate are 
 then added. This causes the formation of metadinitrobenzoic 
 
 * /. Soc. Dyers and Colourists, 1905, 236. 
 t Mohler: Bull. Soc. Chim. [3], 3, 1890, 414. 
 
ANALYTICAL .METHODS 197 
 
 acid. When cool the acid is diluted with water and ammonia 
 added in excess, followed by a drop or two of ammonium sulphide. 
 The nitro-compound becomes converted into ammonium meta- 
 diamidobenzoic acid, which possesses a red color. This reaction 
 takes place immediately, and is seen at the surface of the liquid 
 without stirring. 
 
 Sulphurous Acid and Sulphites. — See directions under Beer, 
 page 198. 
 
 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 at 15.5 C. 
 
 Alcohol. — Determined as in the analysis of wine. The ad- 
 dition of calcium carbonate will not be necessary. If the sample 
 foams much this can be prevented by the addition of about half 
 a gram of tannin before distilling. 
 
 Extract. — Determine the extract content corresponding to 
 the specific gravity of the dealcoholized beer according to Table 
 XIII. For this purpose employ the formula 
 
 Sp = g + (i- g'), 
 
 in which Sp is the specific gravity of the dealcoholized beer, g 
 the specific gravity of the beer, and g' the specific gravity of the 
 distillate obtained in the determination of alcohol. Instead of 
 using this formula the residue from the distillation of alcohol is 
 sometimes diluted to the original volume, and its specific gravity 
 taken. This is often impracticable owing to the necessity of 
 employing tannic acid to prevent foaming in the distilling flask, 
 and owing to the coagulation of proteids during the distillation. 
 
 Note. — The extract of beer cannot be accurately determined 
 by evaporation and drying at the boiling-point of water because 
 of the dehydration of the maltose. 
 
 Ash. — Evaporate 25 c.c. to dryness and determine as de- 
 scribed on page 180. 
 
 Free Acids. — Heat 20 c.c. to incipient boiling to expel carbon 
 dioxide and titrate as in the analysis of wine. Fixed acids, con- 
 
198 AIR, WATER, AND FOOD 
 
 sisting principally of lactic and succinic, are calculated as lactic 
 
 N 
 acid. One c.c. of — sodium hydroxide = 0.0090 gram of lactic 
 10 
 
 acid. 
 
 Reducing Sugar. — Dilute 25 c.c. of the beer, freed from car- 
 bon dioxide, to 100 c.c. Determine the reducing sugar in 25 c.c. 
 of this solution as directed on page 145, enough water being 
 added to make the total volume of the Fehling's solution-sugar 
 mixture 100 c.c. Express the results in terms of maltose, as 
 given in Table XII. 
 
 Preservatives. — The preservatives most commonly employed 
 in beer are benzoic and salicylic acids and their sodium salts, 
 sulphites and fluorides. 
 
 Benzoic and Salicylic Acids. — Detected as described under 
 Wine. 
 
 Sulphites. — Qualitative Test. — Use an apparatus similar to 
 that described for the determination of volatile acids in wine. 
 To 50 c.c. of the sample add about a gram of sodium bicarbonate, 
 20 c.c. of 20 per cent phosphoric acid, and immediately con- 
 nect the flask with the condenser. Pass steam through the 
 flask until about 20 c.c. have collected in the distillate. To the 
 distillate add bromine water in slight excess and boil. Expel 
 the excess of bromine and test for sulphuric acid with hydro- 
 chloric acid and barium chloride in the usual manner. 
 
 Notes. — The method described does not distinguish between 
 free sulphurous acid and that present in the form of sulphites. 
 The former can be distilled without the addition of phosphoric 
 acid. 
 
 The presence of sulphites in a sample should not be con- 
 sidered evidence of added preservatives unless an excessive 
 amount is found, since the use of sulphured malt or hops may 
 introduce a small amount. To obtain conclusive data, a quan- 
 titative determination of the amount present should be made. 
 
 This can be done by a method similar to that used for its 
 detection, distilling in a current of carbon dioxide, absorbing 
 the sulphur dioxide in bromine water and determining the re- 
 
ANALYTICAL METHODS 1 99 
 
 suiting sulphuric acid as barium sulphate. In the case of food 
 products, where sulphides are liable to be present also, the steam 
 should pass through a solution of copper sulphate* before en- 
 tering the condenser in order to remove any hydrogen sulphide 
 formed by the action of the phosphoric acid. Details of the 
 method will be found in Leach's Food Analysis. 
 
 In Bulletin 107 it is recommended to distill into a standard 
 iodine solution and titrate the excess of iodine. This has the 
 disadvantage, however, that other iodine-reducing substances 
 than sulphurous acid may pass into the distillate and give too 
 high results. 
 
 Fluorides. — The well-known qualitative test for fluorides by 
 etching a glass plate may be modified by the use of a suitable 
 condenser and made sufficiently delicate to be used here. It is 
 possible also by suitable regulation of the temperature to make 
 the test approximately quantitative.! 
 
 Flavoring Extracts 
 
 The work on alcoholic liquids can be pleasantly varied by 
 substituting for it, in some cases, the determination of alcohol 
 and other important components of the usual flavoring essences, 
 the most important of which are vanilla and lemon. Several 
 important types of analytical methods, such as the determina- 
 tion of essential oils and quantitative extraction with volatile 
 solvents, are also brought to the attention of the student. 
 
 VANILLA 
 
 Vanilla extract is a dilute alcoholic tincture of the vanilla 
 bean, the fruit of a climbing plant of the orchid family. The 
 best grades are made by allowing the cut and bruised beans to 
 macerate in the alcohol for several months, the liquid thus 
 obtained being deep brown in color, with a delightful perfume 
 and flavor. Sugar is added to assist in the extraction and to 
 sweeten the product. 
 
 * Winton and Bailey: J. Am. Chem. Soc, 1907, 1499. 
 
 t Woodman and Talbot: J. Am. Chem. Soc, 1906, 1437; 1907, 1362. 
 
200 
 
 AIR, WATER, AND FOOD 
 
 The cost of a quart of the pure extract, according to Winton,* 
 is from about 60 cents to $2.50, depending chiefly upon the 
 grade of beans used. 
 
 The composition of five pure vanilla extracts, made from 
 beans of different grades, is given in the following table,| the 
 results being expressed in per cent by weight: 
 
 Grade of bean. 
 
 Specific 
 gravity. 
 
 Vanillin. 
 
 Alcohol. 
 
 Total 
 residue. 
 
 Cane- 
 sugar. 
 
 Mexican (whole) 
 
 Mexican (cut) 
 
 South American (whole) . 
 
 Bourbon (whole) 
 
 Tahiti (whole) 
 
 I. 0159 
 I .0146 
 I . 1009 
 I .0166 
 I. 0104 
 
 O.125 
 O.065 
 0.215 
 O.138 
 0.108 
 
 37-96 
 39-92 
 38.58 
 38.32 
 38.84 
 
 22.6o 
 23.10 
 22.00 
 23.13 
 
 21-75 
 
 19.90 
 19.20 
 19.OO 
 20.40 
 20.00 
 
 The adulteration of vanilla extract consists principally in the 
 use of extract of Tonka bean, a cheap substitute somewhat re- 
 sembling vanilla in its flavor, in the use of artificial prepara- 
 tions of the active principles of vanilla and tonka, vanillin and 
 coumarin, and in the addition of artificial color, usually cara- 
 mel. A cheap extract may be entirely an artificial mixture, 
 made of artificial vanillin or coumarin, or both, in weak alcohol, 
 colored with caramel. An occasional adulteration is the use of 
 alkali, such as potassium bicarbonate, to hold the resin in solu- 
 tion and permit the use of a more dilute alcohol. 
 
 An extract of vanilla of good quality should contain from 25 
 to 40 per cent of alcohol, from 0.10 to 0.20 per cent of vanillin, 
 and give a good precipitate of vanilla resins. Imitation extracts 
 usually show one or several of the following characteristics: 
 Presence of coumarin; deficiency in resins; abnormally low or 
 high content of vanillin; presence of artificial color; low lead 
 number. 
 
 Analytical Methods. — Alcohol. — Measure 25 c.c. of the 
 sample, add 100 c.c. of water, and determine the alcohol by 
 
 * Conn. Agr. Exp. Sta. Report, 1901, 150. 
 t Conn. Agr. Exp. Sta. Report, 1901, 150. 
 
ANALYTICAL METHODS 201 
 
 volume, as directed on page 191, omitting the use of calcium 
 carbonate and tannic acid. 
 
 Vanillin and Coumarin. — (Modified method of Hess and 
 Prescott).* Weigh 50 grams into a 250-c.c. beaker with marks 
 showing volumes of 80 c.c. and 50 c.c., dilute to 80 c.c., and 
 evaporate to 50 c.c. in a water-bath kept at 70 C. Dilute again 
 to 80 c.c. and evaporate to 50 c.c. Transfer to a 100-c.c. flask, 
 rinsing out the beaker with hot water, add 25 c.c. of lead acetate 
 solution (80 grams of neutral lead acetate made up to a liter), 
 make up to the mark with water, shake and allow it to stand 
 over night. Decant on a small dry filter, pipette off 50 c.c. of 
 the nitrate, and extract it four times in a separatory funnel, 
 using 15 c.c. of ether each time. 
 
 Combine the ether extracts in another separatory funnel and 
 wash five times with 2 per cent ammonium hydroxide, using 
 10 c.c. the first time and 5 c.c. for each subsequent shaking. Set 
 aside the combined ammoniacal solutions for the determination 
 of vanillin. 
 
 Transfer the ether solution to a weighed dish and allow the 
 ether to evaporate at room temperature. Dry in a desiccator 
 over sulphuric acid and weigh. If the residue is not white and 
 crystalline stir it for fifteen minutes with 15 c.c. of petroleum 
 ether (boiling point 30 to 40 C.) and decant the clear liquid into 
 a beaker. Repeat the treatment with petroleum ether two or 
 three times. Allow the residue to stand in the air until ap- 
 parently dry, completing the drying in the desiccator. Weigh, 
 and deduct the weight from the weight of the residue obtained 
 after the ether evaporation, thus obtaining the weight of the 
 coumarin. This may be recognized by its characteristic odor, 
 resembling that of " sweet grass," and by Leach's testf as 
 follows: Dissolve the residue in a few drops of hot water, 
 
 N 
 and add one or two drops of — iodine in potassium iodide. 
 
 On stirring with a rod, a brown precipitate will form, which 
 
 * /. Am. Chem. Soc, 1905, 719; Bur. of C hem., Bull. 137, 68. 
 f Leach: "Food Inspection and Analysis," 3d Ed., p. 867. 
 
202 AIR, WATER, AND FOOD 
 
 will gather into dark green flocks. The reaction is especially 
 marked if carried out in a white porcelain crucible or dish. 
 
 Slightly acidulate the ammoniacal solution reserved for vanillin 
 with 10 per cent hydrochloric acid. Cool, and shake out in a 
 separatory funnel with four portions of ether, as described for 
 the first ether extraction. Evaporate the ether at room tem- 
 perature in a weighed dish, dry over sulphuric acid, and weigh 
 the vanillin. 
 
 If the residue is white, it may be safely assumed, in the majority 
 of cases, that it is pure vanillin. If dark colored, however, the 
 dry residue should be extracted not less than fifteen times with 
 boiling petroleum ether (boiling point 40 C. or below). Evapo- 
 rate the solvent, dry and weigh the vanillin. A small amount 
 of the residue, dissolved in two drops of concentrated hydro- 
 chloric acid, should give a pink color upon the addition of a 
 crystal of resorcin. 
 
 Notes. — The separation of vanillin and coumarin is based 
 on the differences in their chemical constitution. Vanillin is 
 hydroxymethoxybenzoic aldehyde, while coumarin is the anhy- 
 dride of orthohydroxycinnamic acid. On account of the alde- 
 hydic nature of the vanillin, the separation by dilute ammonia 
 is possible, the aldehyde ammonia compound of vanillin being 
 readily soluble in water, while the coumarin remains wholly in 
 the ether. 
 
 If a portion of the vanillin, after weighing, be dissolved in two 
 or three drops of ether and allowed to evaporate spontaneously 
 on a microscope slide it shows a characteristic appearance with 
 polarized light. The vanillin crystallizes in slender needles, 
 forming star-shaped clusters. These give a brilliant play of 
 colors with crossed Nicols, even without the selenite plate. 
 
 Normal Lead Number. — To a 10-c.c. portion of the filtrate 
 obtained from the lead acetate in the determination of vanillin 
 and coumarin add 25 c.c. of water, sulphuric acid in slight excess, 
 and 100 c.c. of 95 per cent alcohol, let stand over night, filter on a 
 Gooch crucible, wash with alcohol, dry in the oven of the water- 
 bath, ignite for three minutes at low redness, taking care to 
 
ANALYTICAL METHODS 203 
 
 avoid the reducing flame, and weigh the lead sulphate. Cal- 
 culate the normal lead number by the following formula 
 
 _ 100 X 0.6831 (S - W) 
 5 
 
 in which P = normal lead number, S = grams of lead sulphate 
 corresponding to 2.5 c.c. of the lead acetate solution, as deter- 
 mined from a blank analysis, and W = grams of lead sulphate 
 obtained in 10 c.c. of the filtrate, as just described. 
 
 Note. — The normal lead number of genuine vanilla extracts 
 determined by this method ranges from 0.35 to 0.60. Artificial 
 extracts generally are distinctly lower, sometimes as low as 0.03. 
 
 More accurate results can be obtained by regulating more 
 closely the time and temperature during the standing of the so- 
 lution with lead acetate. Winton and Berry* recommend stand- 
 ing 18 hours at 37 to 40 C. They find that, determined in this 
 manner, the minimum normal lead number for vanilla extracts 
 prepared according to the U. S. Pharmacopoeia is 0.40. 
 
 Resins. — Evaporate 25 or 50 c.c. of the extract to one-third 
 its volume on the water-bath in order to remove the alcohoL 
 Make up to the original volume with hot water. If no alkali 
 has been used in the manufacture of the extract, the resin 
 should appear at this point as a flocculent brown residue. Add 
 acetic acid in slight excess, allow the evaporating-dish to stand 
 in a warm place for a time to separate the resin completely, 
 and filter. Wash the residue on the filter, and save both the 
 filtrate and residue. Test the resin by placing pieces of the 
 filter, with the resin attached, in a few cubic centimeters of 
 dilute caustic potash. The resin is dissolved with a deep red 
 color, and on acidifying is again precipitated. Test the filtrate 
 by adding to it a few drops of basic lead acetate. A bulky pre- 
 cipitate is formed, on account of the organic acid, gums, etc., 
 present. 
 
 Confirm the resin test by shaking 5 c.c. portions of the ex- 
 tract in separate test-tubes with 10 c.c. of amyl alcohol and 
 
 * Bur. of Chem., Bull. 137, 120. 
 
204 AIR, WATER, AND FOOD 
 
 10 c.c. of ether. With pure extracts the upper layers will be 
 colored, varying from light yellow to deep brown; with artificial 
 extracts, free from resin, the amyl alcohol and ether layers will 
 be uncolored. 
 
 Note. — While the artificial vanillin, as sold on the market 
 and used in the manufacture of low-grade extracts, is identical 
 with the vanillin of the vanilla bean, it is true that pure extracts 
 owe their value and flavor to other ingredients as well as to the 
 vanillin present. Among these " extractive matters" the resins 
 are important from an analytical standpoint, serving by their 
 presence or absence to determine whether true vanilla is present 
 or the extract entirely artificial. As a quick and ready test, 
 serving to distinguish artificial extracts from genuine prepara- 
 tions of the vanilla bean, the amyl alcohol and ether tests will 
 be found especially useful. 
 
 Color : Caramel. — Caramel is the color commonly used in 
 vanilla extracts, although coal-tar dyes have been found. The 
 presence of dyes is sometimes indicated by the color of the 
 amyl alcohol in testing for the resin, they being in many cases 
 soluble in amyl alcohol, but insoluble in ether. 
 
 Lead Acetate Test. — The coloring matter present in vanilla 
 extracts is almost completely removed when the dealcoholized 
 extract is treated with a few cubic centimeters of basic lead 
 acetate solution. When caramel is present, the filtrate and 
 precipitate, if any, have the characteristic red-brown color of 
 caramel. 
 
 Marsh Test* — Evaporate 25 c.c. of the extract until the odor 
 of alcohol is no longer apparent and the liquid is reduced to a 
 thick sirup. Dissolve the residue in water and alcohol, using 
 26.3 c.c. of 95 per cent alcohol, and making up to volume in a 
 50-c.c. flask with water. Transfer 25 c.c. of this solution to a 
 separatory funnel; add 25 c.c. of the Marsh reagent and shake, 
 not too vigorously, to avoid emulsification. Allow the layers 
 to separate and repeat the shaking twice more. After the 
 layers have separated clearly, run off the lower layer into a 25-c.c. 
 
 * Bur. of C hem., Bull. 152, p. 149. 
 
ANALYTICAL METHODS 205 
 
 cylinder, and make up to volume with 50 per cent (by volume) 
 alcohol. Filter if necessary and compare in a colorimeter with 
 the remaining 25-c.c. portion (which has not been extracted with 
 the reagent) and express the results as per cent of color insolu- 
 ble in amyl alcohol. 
 
 The Marsh reagent is prepared as follows: Mix 100 c.c. of 
 amyl alcohol, 3 c.c. of sirupy phosphoric acid, and 3 c.c. of water; 
 shake before using. If the reagent becomes colored on standing, 
 the amyl alcohol should be redistilled over 5 per cent phosphoric 
 acid. 
 
 Note. — The method is based on the greater solubility in acid 
 amyl alcohol of the natural color of the vanilla bean as com- 
 pared with caramel. A genuine extract, uncolored with caramel, 
 will not usually show more than 40 per cent of color insoluble in 
 amyl alcohol. 
 
 LEMON 
 
 Lemon extract is usually made by dissolving oil of lemon, 
 obtained by expression or distillation from the rind of the lemon, 
 in strong alcohol. The product is sometimes colored with the 
 color of lemon peel. The Federal standards * require a content 
 of lemon oil of at least 5 per cent by volume. The expensive 
 ingredient of the extract is the alcohol, since alcohol of at least 
 80 per cent strength by volume must be used to dissolve 5 per 
 cent of lemon oil; hence in making cheap extracts the manu- 
 facturer endeavors to use a dilute alcohol, even under the neces- 
 sity of omitting a portion or all of the oil of lemon. 
 
 The common forms of adulteration of lemon extract are the 
 use of weak alcohol and consequent deficiency of lemon oil, as 
 already noted ; the substitution for the lemon oil of small amounts 
 of stronger oils, as oil of citronella, oil of lemon-grass, and the 
 like; the use of citral, the odorous principle of lemon oil, used 
 for making the so-called "terpeneless lemon extracts;" and the 
 coloring of the extracts by coal-tar colors or turmeric. 
 
 Preliminary Test. — To a little of the extract in a test-tube 
 add seven or eight times its volume of water. A high-grade ex- 
 
 * U. S. Dept. Agric, Office of the Secretary, Circ. 19. 
 
206 AIR, WATER, AND FOOD 
 
 tract will show a heavy cloud, due to the precipitation of the 
 lemon oil. If no cloudiness or turbidity appears it may be safely 
 inferred that no oil is present. 
 
 Alcohol. — The determination of alcohol is somewhat com- 
 plicated in this case by the presence of the volatile oil of lemon 
 which must be removed before distilling. 
 
 Dilute 20 c.c. of the extract to 100 c.c. with water, and pour 
 the mixture into a dry Erlenmeyer flask containing 5 grams of 
 light magnesium carbonate. Shake thoroughly and filter 
 through a dry filter. Measure 50 c.c. of the clear filtrate, add 
 about 15 c.c. of water, and distill 50 c.c, as directed on page 191. 
 From the specific gravity of the distillate determine the per cent 
 of alcohol by volume, and this, multiplied by 5, will give the 
 percentage in the original extract. 
 
 Note. — The magnesia serves to absorb the precipitated oil 
 and prevent it from passing through the filter. 
 
 Lemon Oil. — Pipette 20 c.c. of the extract into a Babcock 
 milk bottle; add 1 c.c. dilute hydrochloric acid (1 : 1); then 
 add from 25 to 28 c.c. of water previously warmed to 6o°C; 
 mix and let stand in water at 6o° for five minutes; whirl in 
 centrifuge for five minutes; fill with warm water to bring the 
 oil into the graduated neck of the flask; repeat whirling for 
 two minutes; stand the flask in water at 6o° C. for a few min- 
 utes and read the per cent of oil by volume. If the determina- 
 tion is not made in duplicate the flask should be balanced by 
 another containing an equal weight of water. In case oil of 
 lemon is present in amounts over 2 per cent add to the percent- 
 age of oil found 0.4 per cent to correct for the oil retained in 
 solution. If less than 2 per cent and more than 1 per cent is 
 present, add 0.3 per cent for correction. 
 
 Color. — Test for coal-tar colors by evaporating a portion of 
 the extract to dryness on the water-bath. Dissolve the residue 
 in water and carry out the double dyeing method, as described 
 on page 194. 
 
 It may be advisable not to add any acid to the dye bath, as 
 Naphthol Yellow S, which is commonly used in lemon extracts, 
 dyes wool best from a nearly neutral bath. 
 
ANALYTICAL METHODS 207 
 
 To test for turmeric add to a portion of the sample three 
 drops of saturated boric acid solution, one small drop of dilute 
 (1 : 10) hydrochloric acid, and a piece of filter-paper so ar- 
 ranged that it is only half immersed in the liquid. Evaporate 
 to dryness on the water-bath. In the presence of turmeric the 
 paper will be colored pink and the test may be confirmed as 
 described on page 154. Excess of hydrochloric acid should be 
 avoided as in testing for boric acid. 
 
 To show the presence of natural color derived from lemon 
 peel the following reactions will be found helpful : * Dilute a few 
 cubic centimeters of the extract until the color has nearly dis- 
 appeared and divide the solution between two test-tubes. To 
 one add a few drops of concentrated hydrochloric acid and to 
 the other a few drops of strong ammonia. In the presence of 
 natural color a distinct yellow color should result in each case. 
 
 Citral. — See Bur. of Chem., Bull. 137, 70. 
 
 * Albrech: Bur. of Chem., Bull. 137, 71. 
 
APPENDICES 
 
 APPENDIX A 
 
 TABLE I 
 
 TENSION OF AQUEOUS VAPOR IN MILLIMETERS OF MERCURY FROM O TO 3O.9 C, 
 REDUCED TOO° AND SEA-LEVEL 
 
 
 0.0 
 
 O.I 
 
 0.2 
 
 0.3 
 
 0.4 
 
 o.S 
 
 0.6 
 
 0.7 
 
 0.8 
 
 0.9 
 
 o° 
 
 4-57 
 
 4.60 
 
 4.64 
 
 4.67 
 
 4.70 
 
 4-74 
 
 4-77 
 
 4.80 
 
 4.84 
 
 4.87 
 
 I 
 
 4.91 
 
 4-94 
 
 4.98 
 
 5.02 
 
 5-05 
 
 5 09 
 
 5-12 
 
 5-i6 
 
 5.20 
 
 523 
 
 2 
 
 5-27 
 
 5-31 
 
 5-35 
 
 5-39 
 
 5-42 
 
 5 -46 
 
 5-5o 
 
 5-54 
 
 5-58 
 
 5.62 
 
 3 
 
 5-66 
 
 5-7o 
 
 5-74 
 
 5-78 
 
 5.82 
 
 5-86 
 
 5 90 
 
 5-94 
 
 5-99 
 
 6.03 
 
 4 
 
 6.07 
 
 6. 11 
 
 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 
 
 6.92 
 
 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 
 
 7-8 3 
 
 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 
 
 8.90 
 
 8.96 
 
 9.02 
 
 9.08 
 
 10 
 
 9.14 
 
 9.20 
 
 9.26 
 
 9-32 
 
 9-39 
 
 9-45 
 
 9-51 
 
 9-58 
 
 9.64 
 
 9.70 
 
 11 
 
 9-77 
 
 9-83 
 
 9.90 
 
 9.96 
 
 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 
 
 11 .14 
 
 11 .21 
 
 11.28 
 
 11.36 
 
 H-43 
 
 11.50 
 
 11.58 
 
 11.66 
 
 n-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 
 
 I3-I7 
 
 13-25 
 
 13-34 
 
 13-42 
 
 16 
 
 i3-5i 
 
 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 
 
 18 
 
 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 
 
 i8.35 
 
 21 
 
 18.47 
 
 18.58 
 
 18.69 
 
 18.81 
 
 18.92 
 
 19.04 
 
 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 . 11 
 
 21.24 
 
 21.37 
 
 21.50 
 
 21.63 
 
 21.76 
 
 21.89 
 
 22.02 
 
 24 
 
 22.15 
 
 22.29 
 
 22.42 
 
 22.55 
 
 22.69 
 
 22.83 
 
 22.96 
 
 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 
 
 27.90 
 
 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 
 
 30.97 
 
 3I-I5 
 
 31-33 
 
 30 
 
 3i-5i 
 
 31.69 
 
 3187 
 
 32.06 
 
 32.24 
 
 32.43 
 
 32.61 
 
 32.80 
 
 3299 
 
 33.18 
 
 208 
 
APPENDIX A 
 
 209 
 
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APPENDIX A 
 
 211 
 
 
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 APPENDIX A 
 
 213 
 
 t-H O ^ 
 
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214 
 
 AIR, WATER, AND FOOD 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 . r/5 
 
 
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APPENDIX A 
 
 215 
 
 TABLE VII 
 
 SULPHATES IN WATER 
 
 (Reduced from table in article by H. F. Muer, J. Ind. Eng. Chem., 1911, 
 
 Vol. 3, p. 553) 
 
 Depth, 
 
 S0 3 , pts. per 
 
 Depth, 
 
 S0 3 , pts. per 
 
 Depth, 
 
 SO3, pts. per 
 
 Depth, 
 
 S0 3 , pts. per 
 
 cm. 
 
 million. 
 
 cm. 
 
 million. 
 
 cm. 
 
 million. 
 
 cm. 
 
 million. 
 
 i-5 
 
 3I30 
 
 6.7 
 
 72.O 
 
 II. 9 
 
 47-3 
 
 17,1 
 
 37-3 
 
 1 
 
 6 
 
 280.0 
 
 6 
 
 8 
 
 71 
 
 3 
 
 I2.0 
 
 47 
 
 .0 
 
 17.2 
 
 37 
 
 3 
 
 1 
 
 7 
 
 250.O 
 
 6 
 
 9 
 
 70 
 
 5 
 
 12. 1 
 
 46 
 
 .8 
 
 17-3 
 
 37 
 
 
 
 1 
 
 8 
 
 238.0 
 
 7 
 
 .0 
 
 69 
 
 8 
 
 12.2 
 
 46 
 
 •5 
 
 17-4 
 
 36 
 
 8 
 
 1 
 
 9 
 
 225.O 
 
 7 
 
 .1 
 
 69 
 
 
 
 12.3 
 
 46 
 
 ■3 
 
 17-5 
 
 36 
 
 8 
 
 * 
 
 
 
 213.O 
 
 7 
 
 .2 
 
 68 
 
 3 
 
 12.4 
 
 46 
 
 .0 
 
 17.6 
 
 36 
 
 5 
 
 2 
 
 1 
 
 200.0 
 
 7 
 
 •3 
 
 67 
 
 5 
 
 12.5 
 
 45 
 
 .8 
 
 17.7 
 
 36 
 
 3 
 
 2 
 
 2 
 
 190.O 
 
 7 
 
 •4 
 
 66 
 
 8 
 
 12.6 
 
 45 
 
 •5 
 
 17.8 
 
 36 
 
 
 
 2 
 
 3 
 
 183.O 
 
 7 
 
 5 
 
 66 
 
 
 
 12.7 
 
 45 
 
 3 
 
 17.9 
 
 36 
 
 
 
 2 
 
 4 
 
 I7S-0 
 
 7 
 
 6 
 
 65 
 
 3 
 
 12.8 
 
 45 
 
 
 
 18.0 
 
 35 
 
 8 
 
 2 
 
 5 
 
 168.O 
 
 7 
 
 •7 
 
 64 
 
 8 
 
 12.9 
 
 44 
 
 .8 
 
 18. 1 
 
 35 
 
 8 
 
 * 
 
 6 
 
 163.0 
 
 7 
 
 8 
 
 64 
 
 
 
 13.0 
 
 44 
 
 5 
 
 18.2 
 
 35 
 
 5 
 
 2 
 
 7 
 
 158.0 
 
 7 
 
 9 
 
 63 
 
 5 
 
 13- 1 
 
 44 
 
 3 
 
 18.3 
 
 35 
 
 3 
 
 2 
 
 8 
 
 I530 
 
 8 
 
 
 
 62 
 
 8 
 
 13.2 
 
 44 
 
 
 
 18.4 
 
 35 
 
 3 
 
 2 
 
 9 
 
 148.O 
 
 8 
 
 1 
 
 62 
 
 3 
 
 13-3 
 
 43 
 
 8 
 
 18.5 
 
 35 
 
 
 
 3 
 
 
 
 I43.0 
 
 8 
 
 2 
 
 61 
 
 8 
 
 13-4 
 
 43 
 
 5 
 
 18.6 
 
 35 
 
 
 
 3 
 
 1 
 
 138.O 
 
 8 
 
 3 
 
 61 
 
 
 
 13-5 
 
 43 
 
 3 
 
 18.7 
 
 34 
 
 8 
 
 3 
 
 2 
 
 I35-0 
 
 8 
 
 4 
 
 60 
 
 5 
 
 136 
 
 43 
 
 3 
 
 18.8 
 
 34 
 
 5 
 
 3 
 
 3 
 
 130.0 
 
 8 
 
 5 
 
 60 
 
 
 
 13 -7 
 
 43 
 
 
 
 18.9 
 
 34 
 
 5 
 
 3 
 
 4 
 
 128.O 
 
 8 
 
 6 
 
 59 
 
 5 
 
 13-8 
 
 42 
 
 8 
 
 19.0 
 
 34 
 
 3 
 
 3 
 
 5 
 
 125.O 
 
 8 
 
 7 
 
 59 
 
 
 
 13-9 
 
 42 
 
 5 
 
 19. 1 
 
 34 
 
 3 
 
 3 
 
 6 
 
 122.5 
 
 8 
 
 8 
 
 58 
 
 5 
 
 14.0 
 
 42 
 
 5 
 
 19.2 
 
 34 
 
 
 
 3 
 
 7 
 
 120.0 
 
 8 
 
 9 
 
 58 
 
 
 
 14. 1 
 
 42 
 
 3 
 
 19-3 
 
 33 
 
 8 
 
 3 
 
 8 
 
 «7-5 
 
 9 
 
 
 
 57 
 
 5 
 
 14.2 
 
 42 
 
 
 
 19.4 
 
 33 
 
 8 
 
 3 
 
 9 
 
 115. 
 
 9 
 
 1 
 
 57 
 
 
 
 14-3 
 
 4i 
 
 8 
 
 19-5 
 
 33 
 
 5 
 
 4 
 
 
 
 112. 5 
 
 9 
 
 2 
 
 56 
 
 5 
 
 14.4 
 
 4i 
 
 5 
 
 19.6 
 
 33 
 
 5 
 
 4 
 
 1 
 
 110.0 
 
 9 
 
 3 
 
 56 
 
 3 
 
 14-5 
 
 4i 
 
 5 
 
 19.7 
 
 33 
 
 3 
 
 4 
 
 2 
 
 107.5 
 
 9 
 
 4 
 
 55 
 
 8 
 
 14.6 
 
 4i 
 
 3 
 
 19.8 
 
 33 
 
 
 
 4 
 
 3 
 
 105.0 
 
 9 
 
 5 
 
 55 
 
 3 
 
 14-7 
 
 4i 
 
 
 
 19.9 
 
 33 
 
 
 
 4 
 
 4 
 
 102.5 
 
 9 
 
 6 
 
 54 
 
 8 
 
 14.8 
 
 40 
 
 8 
 
 20.0 
 
 32 
 
 8 
 
 4 
 
 5 
 
 100. 
 
 9 
 
 7 
 
 54 
 
 5 
 
 14.9 
 
 40 
 
 5 
 
 20.1 
 
 32 
 
 5 
 
 4 
 
 6 
 
 98-3 
 
 9 
 
 8 
 
 54 
 
 
 
 150 
 
 40 
 
 5 
 
 20.2 
 
 32 
 
 5 
 
 4 
 
 7 
 
 96-5 
 
 9 
 
 9 
 
 53 
 
 8 
 
 151 
 
 40 
 
 3 
 
 20.3 
 
 32 
 
 3 
 
 4 
 
 8 
 
 94.8 
 
 10 
 
 
 
 53 
 
 3 
 
 152 
 
 40 
 
 
 
 20.4 
 
 32 
 
 
 
 4 
 
 9 
 
 93 
 
 10 
 
 1 
 
 52 
 
 8 
 
 15-3 
 
 40 
 
 
 
 20.5 
 
 32 
 
 
 
 5 
 
 
 
 91-5 
 
 10 
 
 2 
 
 52 
 
 5 
 
 15-4 
 
 39 
 
 8 
 
 20.6 
 
 3i 
 
 8 
 
 5 
 
 1 
 
 90.0 
 
 10 
 
 3 
 
 52 
 
 3 
 
 15-5 
 
 39 
 
 8 
 
 20.7 
 
 31 
 
 5 
 
 5 
 
 2 
 
 88.5 
 
 10 
 
 4 
 
 5i 
 
 8 
 
 15-6 
 
 39 
 
 5 
 
 20.8 
 
 3i 
 
 5 
 
 5 
 
 3 
 
 87-3 
 
 10 
 
 5 
 
 5i 
 
 5 
 
 15-7 
 
 39 
 
 3 
 
 20.9 
 
 3i 
 
 3 
 
 5 
 
 4 
 
 85.8 
 
 10 
 
 6 
 
 5i 
 
 
 
 15-8 
 
 39 
 
 3 
 
 21 .0 
 
 31 
 
 3 
 
 5 
 
 5 
 
 84-5 
 
 10 
 
 7 
 
 50 
 
 8 
 
 15-9 
 
 39 
 
 
 
 21 .1 
 
 3i 
 
 
 
 5 
 
 6 
 
 83-3 
 
 10 
 
 8 
 
 50 
 
 5 
 
 16.0 
 
 39 
 
 
 
 21 .2 
 
 30 
 
 8 
 
 5 
 
 7 
 
 82.0 
 
 10 
 
 9 
 
 50 
 
 3 
 
 16. 1 
 
 38 
 
 8 
 
 21.3 
 
 30 
 
 8 
 
 5 
 
 8 
 
 81.0 
 
 11 
 
 
 
 50 
 
 
 
 16.2 
 
 38 
 
 5 
 
 21.4 
 
 30 
 
 5 
 
 5 
 
 9 
 
 80.0 
 
 11 
 
 1 
 
 49 
 
 5 
 
 16.3 
 
 38 
 
 5 
 
 21.5 
 
 30 
 
 3 
 
 6 
 
 
 
 78.8 
 
 11 
 
 2 
 
 49 
 
 3 
 
 16.4 
 
 38 
 
 3 
 
 21 .6 
 
 30 
 
 3 
 
 6 
 
 1 
 
 77.8 
 
 11 
 
 3 
 
 48 
 
 8 
 
 16.5 
 
 38 
 
 3 
 
 21.7 
 
 30 
 
 
 
 6 
 
 2 
 
 76.8 
 
 11 
 
 4 
 
 48 
 
 5 
 
 16.6 
 
 38 
 
 
 
 21.8 
 
 30 
 
 
 
 6 
 
 3 
 
 75-8 
 
 11 
 
 5 
 
 48 
 
 3 
 
 16.7 
 
 38 
 
 
 
 21 .9 
 
 29 
 
 8 
 
 6 
 
 4 
 
 74.8 
 
 11 
 
 6 
 
 48 
 
 
 
 iS-8 
 
 37 
 
 8 
 
 22.0 
 
 29 
 
 5 
 
 6 
 
 5 
 
 73-8 
 
 11 
 
 7 
 
 47 
 
 8 
 
 16.9 
 
 37 
 
 5 
 
 
 
 
 6 
 
 6 
 
 73 -o 
 
 11 
 
 8 
 
 47 
 
 5 
 
 17.0 
 
 37 
 
 5 
 
 
 
 
2l6 
 
 AIR, WATER, AND FOOD 
 
 TABLE VIII 
 
 TABLE OF HARDNESS, SHOWING THE PARTS OF CALCIUM CARBONATE (CaCC*) IN 
 
 1,000,000 FOR EACH TENTH OF A CUBIC CENTIMETER 
 
 OF SOAP SOLUTION USED 
 
 
 0.0 
 
 O.I 
 
 0.2 
 
 0.3 
 
 0.4 
 
 0.5 
 
 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 
 
 
 
 
 
 
 
 
 O.O 
 
 1.6 
 
 3-2 
 
 1.0 
 
 4.8 
 
 6 
 
 3 
 
 7-9 
 
 9 
 
 5 
 
 II .1 
 
 12.7 
 
 14-3 
 
 15-6 
 
 16.9 
 
 18.2 
 
 2.0 
 
 19 -5 
 
 20 
 
 8 
 
 22. 1 
 
 23 
 
 4 
 
 24.7 
 
 26.O 
 
 27-3 
 
 28.6 
 
 29.9 
 
 31.2 
 
 3-o 
 
 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 
 
 
 
 5i-4 
 
 52-9 
 
 54-3 
 
 55-7 
 
 57-i 
 
 58.6 
 
 5-o 
 
 60.0 
 
 61 
 
 4 
 
 62.9 
 
 64 
 
 3 
 
 65-7 
 
 67.1 
 
 68.6 
 
 70.0 
 
 7i-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 
 
 
 
 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. 
 
 II3-5 
 
 115. 
 
 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 
 
 
 
 139- 1 
 
 140.6 
 
 142. 1 
 
 143-7 
 
 145-2 
 
 146.8 
 
 11. 
 
 148.4 
 
 150 
 
 
 
 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 
 
 
 
 170.6 
 
 172.2 
 
 173-8 
 
 175-4 
 
 177.0 
 
 178.6 
 
 13.0 
 
 180.2 
 
 181 
 
 7 
 
 183 -3 
 
 184 
 
 Q 
 
 186.5 
 
 188. 1 
 
 189.7 
 
 I9I-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 
 
 150 
 
 211 .9 
 
 213 
 
 5 
 
 215. 1 
 
 2l6 
 
 8 
 
 218.5 
 
 220.2 
 
 221.8 
 
 223-5 
 
 225.2 
 
 226.9 
 
 TABLE IX 
 
 FOR CORRECTING THE SPECIFIC GRAVITY OF MILK ACCORDING TO TEMPERATURE 
 ADAPTED FROM THE TABLE OF VIETH 
 
 (Temperature in Degrees Centigrade) 
 
 Specific 
 gravity. 
 
 10° 
 
 ii° 
 
 12° 
 
 13° 
 
 14° 
 
 i5° 
 
 16 
 
 17° 
 
 18 
 
 19° 
 
 20° 
 
 I.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 
 
 Q 
 
 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 
 
 
 
 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 
 
 3° 
 
 29.0 
 
 29. 1 
 
 29 
 
 3 
 
 29 
 
 5 
 
 29.7 
 
 29 
 
 9 
 
 30.1 
 
 30 
 
 4 
 
 30 
 
 5 
 
 3° 
 
 8 
 
 3ii 
 
 31 
 
 29.9 
 
 30.1 
 
 30 
 
 3 
 
 30 
 
 4 
 
 30.6 
 
 30 
 
 Q 
 
 31.2 
 
 31 
 
 4 
 
 31 
 
 5 
 
 31 
 
 8 
 
 32.2 
 
 32 
 
 30-9 
 
 3ii 
 
 3i 
 
 3 
 
 31 
 
 4 
 
 3i-6 
 
 3i 
 
 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-i 
 
 34-4 
 
 34-6 
 
 34-9 
 
 35-2 
 
 35 
 
 4 
 
 35-6 
 
 35 
 
 
 
 36.2 
 
 Directions. — Find the observed gravity in the left-hand column. Then, in 
 the same line, and under the observed temperature, will be found the corrected 
 reading. 
 
APPENDIX A 
 
 217 
 
 TABLE X 
 
 PERCENTAGE OF ALCOHOL FROM THE SPECIFIC GRAVITY AT 
 
 15 °. 5 c. (hehner) 
 
 
 Per cent 
 
 Per cent 
 
 
 Per cent 
 
 Per cent 
 
 
 Per cent 
 
 Per cent 
 
 Sp.gr. 
 
 alcohol 
 
 alcohol 
 
 Sp. gr. 
 
 alcohol 
 
 alcohol 
 
 Sp. gr. 
 
 alcohol 
 
 alcohol 
 
 I5°o C. 
 
 by 
 
 by 
 
 I5°.5 C. 
 
 by 
 
 by 
 
 I5°.S C. 
 
 by 
 
 by 
 
 
 weight. 
 
 volume. 
 
 
 weight. 
 
 volume. 
 
 
 weight. 
 
 volume. 
 
 I . OOOO 
 
 0.00 
 
 0.00 
 
 
 
 
 
 
 
 0.9999 
 
 0.05 
 
 0.07 
 
 0-9959 
 
 2 33 
 
 2 93 
 
 O.9919 
 
 4.69 
 
 5 86 
 
 8 
 
 0. II 
 
 0.13 
 
 8 
 
 2 
 
 39 
 
 3 
 
 00 
 
 8 
 
 4-75 
 
 5 
 
 94 
 
 7 
 
 0.16 
 
 0.20 
 
 7 
 
 2 
 
 44 
 
 3 
 
 07 
 
 7 
 
 4.81 
 
 6 
 
 02 
 
 6 
 
 0.21 
 
 0.26 
 
 6 
 
 2 
 
 50 
 
 3 
 
 14 
 
 6 
 
 4.87 
 
 6 
 
 10 
 
 5 
 
 0.26 
 
 033 
 
 5 
 
 2 
 
 56 
 
 3 
 
 21 
 
 5 
 
 4-94 
 
 6 
 
 17 
 
 4 
 
 0.32 
 
 0.40 
 
 4 
 
 2 
 
 61 
 
 3 
 
 28 
 
 4 
 
 5.00 
 
 6 
 
 24 
 
 3 
 
 0.37 
 
 0.46 
 
 3 
 
 2 
 
 67 
 
 3 
 
 35 
 
 3 
 
 5.06 
 
 6 
 
 32 
 
 2 
 
 0.42 
 
 053 
 
 2 
 
 2 
 
 72 
 
 3 
 
 42 
 
 2 
 
 5-i2 
 
 6 
 
 40 
 
 1 
 
 0.47 
 
 0.60 
 
 1 
 
 2 
 
 78 
 
 3 
 
 49 
 
 1 
 
 519 
 
 6 
 
 48 
 
 
 
 053 
 
 0.66 
 
 
 
 2 
 
 83 
 
 3 
 
 55 
 
 
 
 5-25 
 
 6 
 
 55 
 
 O.9989 
 
 0.58 
 
 0.73 
 
 0.0049 
 
 2 
 
 89 
 
 3 
 
 62 
 
 0.9909 
 
 5 3i 
 
 6 
 
 63 
 
 8 
 
 0.63 
 
 0.79 
 
 8 
 
 2 
 
 94 
 
 3 
 
 69 
 
 8 
 
 5-37 
 
 6 
 
 7i 
 
 7 
 
 0.68 
 
 0.86 
 
 7 
 
 3 
 
 00 
 
 3 
 
 76 
 
 7 
 
 5-44 
 
 6 
 
 78 
 
 6 
 
 0.74 
 
 093 
 
 6 
 
 3 
 
 06 
 
 3 
 
 83 
 
 6 
 
 5-5° 
 
 6 
 
 86 
 
 5 
 
 0.79 
 
 0.99 
 
 5 
 
 3 
 
 12 
 
 3 
 
 90 
 
 5 
 
 5-56 
 
 6 
 
 94 
 
 4 
 
 0.84 
 
 1 .06 
 
 4 
 
 3 
 
 18 
 
 3 
 
 98 
 
 4 
 
 5.62 
 
 7 
 
 01 
 
 3 
 
 0.89 
 
 I 13 
 
 3 
 
 3 
 
 24 
 
 4 
 
 05 
 
 3 
 
 569 
 
 7 
 
 09 
 
 2 
 
 o-95 
 
 1. 19 
 
 2 
 
 3 
 
 29 
 
 4 
 
 12 
 
 2 
 
 5-75 
 
 7 
 
 17 
 
 1 
 
 1 .00 
 
 1.26 
 
 1 
 
 3 
 
 35 
 
 4 
 
 20 
 
 1 
 
 5-8i 
 
 7 
 
 25 
 
 
 
 1.06 
 
 i-34 
 
 
 
 3 
 
 41 
 
 4 
 
 27 
 
 
 
 5-8 7 
 
 7 
 
 32 
 
 09979 
 
 1.12 
 
 1.42 
 
 0.9939 
 
 3 
 
 47 
 
 4 
 
 34 
 
 0.9809 
 
 5 94 
 
 7 
 
 40 
 
 8 
 
 1. 19 
 
 1.49 
 
 8 
 
 3 
 
 53 
 
 4 
 
 42 
 
 8 
 
 6.00 
 
 7 
 
 48 
 
 7 
 
 1.25 
 
 i-57 
 
 7 
 
 3 
 
 59 
 
 4 
 
 49 
 
 7 
 
 6.07 
 
 7 
 
 57 
 
 6 
 
 1. 31 
 
 1.65 
 
 6 
 
 3 
 
 65 
 
 4 
 
 56 
 
 6 
 
 6.14 
 
 7 
 
 66 
 
 5 
 
 i-37 
 
 i-73 
 
 5 
 
 3 
 
 7i 
 
 4 
 
 63 
 
 5 
 
 6.21 
 
 7 
 
 74 
 
 4 
 
 1.44 
 
 1. 81 
 
 4 
 
 3 
 
 76 
 
 4 
 
 7i 
 
 4 
 
 6.28 
 
 7 
 
 83 
 
 3 
 
 1-50 
 
 1.88 
 
 3 
 
 3 
 
 82 
 
 4 
 
 78 
 
 3 
 
 6.36 
 
 7 
 
 92 
 
 2 
 
 1-56 
 
 1.96 
 
 2 
 
 3 
 
 88 
 
 4 
 
 85 
 
 2 
 
 6-43 
 
 8 
 
 01 
 
 1 
 
 1 .62 
 
 2.04 
 
 1 
 
 3 
 
 94 
 
 4 
 
 93 
 
 1 
 
 6.50 
 
 8 
 
 10 
 
 
 
 1 .69 
 
 2.12 
 
 
 
 4 
 
 00 
 
 5 
 
 00 
 
 
 
 6-57 
 
 8 
 
 18 
 
 O.9969 
 
 1 75 
 
 2.20 
 
 0.0929 
 
 4 
 
 06 
 
 5 
 
 08 
 
 0.9889 
 
 6.64 
 
 8 
 
 27 
 
 8 
 
 1. 81 
 
 2 . 27 
 
 8 
 
 4 
 
 12 
 
 5 
 
 16 
 
 8 
 
 6.71 
 
 8 
 
 36 
 
 7 
 
 1.87 
 
 2-35 
 
 7 
 
 4 
 
 19 
 
 5 
 
 24 
 
 7 
 
 6.78 
 
 8 
 
 45 
 
 6 
 
 1.94 
 
 2-43 
 
 6 
 
 4 
 
 25 
 
 5 
 
 32 
 
 6 
 
 6.86 
 
 8 
 
 54 
 
 5 
 
 2 .00 
 
 2.51 
 
 5 
 
 4 
 
 3i 
 
 5 
 
 39 
 
 5 
 
 6-93 
 
 8 
 
 63 
 
 4 
 
 2.06 
 
 2.58 
 
 4 
 
 4 
 
 37 
 
 5 
 
 47 
 
 4 
 
 7.00 
 
 8 
 
 72 
 
 3 
 
 2. 11 
 
 2.62 
 
 3 
 
 4 
 
 44 
 
 5 
 
 55 
 
 3 
 
 7.07 
 
 8 
 
 80 
 
 2 
 
 2.17 
 
 2.72 
 
 2 
 
 4 
 
 50 
 
 5 
 
 63 
 
 2 
 
 7-i3 
 
 8 
 
 88 
 
 1 
 
 2.22 
 
 2-79 
 
 1 
 
 4 
 
 56 
 
 5 
 
 7i 
 
 1 
 
 7. 20 
 
 8 
 
 96 
 
 
 
 2.28 
 
 2.86 
 
 
 
 4 
 
 62 
 
 5 
 
 78 
 
 
 
 7.27 
 
 9.04 
 
2l8 
 
 AIR, WATER, AND FOOD 
 
 TABLE X. — (Continued) 
 
 PERCENTAGE OF ALCOHOL 
 
 
 Per cent 
 
 Per cent 
 
 
 Per cent 
 
 Per cent 
 
 
 Per cent 
 
 Per cent 
 
 Sp. gr. 
 
 alcohol 
 
 alcohol 
 
 Sp.gr. 
 
 alcohol 
 
 alcohol 
 
 Sp. gr. 
 
 alcohol 
 
 alcohol 
 
 i5°-5 C. 
 
 by 
 
 by 
 
 IS°.5 C. 
 
 by 
 
 by 
 
 I5°.5 C. 
 
 by 
 
 by 
 
 
 weight. 
 
 volume. 
 
 
 weight. 
 
 volume. 
 
 
 weight. 
 
 volume. 
 
 O.9879 
 
 7 33 
 
 9 13 
 
 5 
 
 IO.46 
 
 12.96 
 
 2 
 
 13-77 
 
 16.98 
 
 8 
 
 7 
 
 40 
 
 9.21 
 
 4 
 
 IO-54 
 
 13 
 
 •05 
 
 I 
 
 13 
 
 .85 
 
 17.08 
 
 7 
 
 7 
 
 47 
 
 9.29 
 
 3 
 
 IO.62 
 
 13 
 
 •15 
 
 O 
 
 13 
 
 .92 
 
 17.17 
 
 6 
 
 7 
 
 53 
 
 9-37 
 
 2 
 
 IO.69 
 
 13 
 
 .24 
 
 
 
 
 
 5 
 
 7 
 
 60 
 
 9-45 
 
 1 
 
 IO.77 
 
 13 
 
 •34 
 
 O.9789 
 
 14 
 
 00 
 
 17.26 
 
 4 
 
 7 
 
 67 
 
 9-54 
 
 
 
 10.85 
 
 13 
 
 43 
 
 8 
 
 14 
 
 09 
 
 17-37 
 
 3 
 
 7 
 
 73 
 
 9.62 
 
 
 
 
 
 7 
 
 14 
 
 18 
 
 17.48 
 
 2 
 
 7 
 
 80 
 
 9.70 
 
 0.9829 
 
 IO.92 
 
 13 
 
 52 
 
 6 
 
 14 
 
 27 
 
 17-59 
 
 1 
 
 7 
 
 87 
 
 9.78 
 
 8 
 
 11 .00 
 
 13 
 
 62 
 
 5 
 
 14 
 
 36 
 
 17.70 
 
 
 
 7 
 
 93 
 
 9.86 
 
 7 
 
 11.08 
 
 13 
 
 72 
 
 4 
 
 14 
 
 45 
 
 17.81 
 
 
 
 
 
 6 
 
 II. 15 
 
 13 
 
 81 
 
 3 
 
 14 
 
 55 
 
 17.92 
 
 0.9869 
 
 8 
 
 00 
 
 9 95 
 
 5 
 
 II.23 
 
 13 
 
 90 
 
 2 
 
 14 
 
 64 
 
 18.03 
 
 8 
 
 8 
 
 07 
 
 10.03 
 
 4 
 
 II. 31 
 
 13 
 
 99 
 
 1 
 
 14 
 
 73 
 
 18.14 
 
 7 
 
 8 
 
 •14 
 
 10.12 
 
 3 
 
 11.38 
 
 14 
 
 09 
 
 
 
 14 
 
 82 
 
 18.25 
 
 6 
 
 8 
 
 .21 
 
 10.21 
 
 2 
 
 II.46 
 
 14 
 
 18 
 
 
 
 
 
 5 
 
 8 
 
 .29 
 
 10.30 
 
 1 
 
 H-54 
 
 14 
 
 27 
 
 0.9779 
 
 14 
 
 90 
 
 18.36 
 
 4 
 
 8 
 
 •36 
 
 10.38 
 
 
 
 11 .62 
 
 14 
 
 37 
 
 8 
 
 15 
 
 00 
 
 18.48 
 
 3 
 
 8 
 
 •43 
 
 10.47 
 
 
 
 
 
 7 
 
 15 
 
 08 
 
 18.58 
 
 2 
 
 8 
 
 •So 
 
 10.56 
 
 0.9819 
 
 11.69 
 
 14 
 
 46 
 
 6 
 
 15 
 
 17 
 
 18.68 
 
 1 
 
 8 
 
 •57 
 
 10.65 
 
 8 
 
 11.77 
 
 14 
 
 56 
 
 5 
 
 15 
 
 25 
 
 18.78 
 
 
 
 8 
 
 .64 
 
 10.73 
 
 7 
 
 n.85 
 
 14 
 
 65 
 
 4 
 
 15 
 
 33 
 
 18.88 
 
 0.9859 
 
 8 
 7 
 
 8 
 
 8 
 8 
 
 7i 
 
 79 
 86 
 
 10.82 
 
 10.91 
 11 .00 
 
 6 
 
 5 
 4 
 
 11.92 
 
 12.00 
 12.08 
 
 14 
 14 
 14 
 
 74 
 84 
 93 
 
 3 
 2 
 
 1 
 
 15 
 15 
 15 
 
 42 
 50 
 58 
 
 18.98 
 19.08 
 19.18 
 
 6 
 
 8 
 
 93 
 
 11.08 
 
 3 
 2 
 
 12.15 
 12.23 
 12.31 
 12.38 
 
 12.46 
 
 15 
 15 
 15 
 15 
 
 15 
 
 02 
 12 
 
 
 
 15 
 
 67 
 
 19.28 
 
 5 
 4 
 3 
 2 
 
 9 
 9 
 9 
 9 
 
 00 
 07 
 
 14 
 
 21 
 
 11. 17 
 11.26 
 
 n-35 
 11.44 
 
 1 
 
 
 O.9809 
 
 21 
 
 30 
 
 40 
 
 O.9769 
 
 8 
 
 7 
 6 
 
 15 
 
 15 
 15 
 16 
 
 75 
 
 83 
 92 
 00 
 
 19 39 
 
 19.49 
 
 19-59 
 19.68 
 
 1 
 
 
 9 
 9 
 
 29 
 36 
 
 11 .52 
 11. 61 
 
 8 
 
 7 
 
 12.54 
 12.62 
 
 15 
 15 
 
 49 
 
 58 
 
 5 
 4 
 
 16 
 16 
 
 08 
 15 
 
 19.78 
 19.87 
 
 0.9849 
 
 9 
 
 43 
 
 11.70 
 
 6 
 
 12.69 
 
 15 
 
 68 
 
 3 
 
 16 
 
 23 
 
 19.96 
 
 8 
 
 9 
 
 5° 
 
 11.79 
 
 5 
 
 12.77 
 
 15 
 
 77 
 
 2 
 
 16 
 
 31 
 
 20.06 
 
 7 
 
 9 
 
 57 
 
 11.87 
 
 4 
 
 12.85 
 
 15 
 
 86 
 
 1 
 
 16. 
 
 38 
 
 20.15 
 
 6 
 
 9 
 
 64 
 
 11.96 
 
 3 
 
 12.92 
 
 15 
 
 96 
 
 
 
 16. 
 
 46 
 
 20.24 
 
 5 
 
 9 
 
 7i 
 
 12.05 
 
 2 
 
 13.00 
 
 16 
 
 05 
 
 
 
 
 
 4 
 
 9 
 
 79 
 
 12.13 
 
 1 
 
 13.08 
 
 16 
 
 15 
 
 0-9759 
 
 16. 
 
 54 
 
 20.33 
 
 3 
 
 9 
 
 86 
 
 12.22 
 
 
 
 I3-I5 
 
 16. 
 
 24 
 
 8 
 
 16. 
 
 62 
 
 20.43 
 
 2 
 
 9 
 
 93 
 
 12.31 
 
 
 
 
 
 7 
 
 16. 
 
 69 
 
 20.52 
 
 1 
 
 10 
 
 00 
 
 12.40 
 
 0.9799 
 
 13 23 
 
 16 
 
 33 
 
 6 
 
 16. 
 
 77 
 
 20.61 
 
 
 
 10 
 
 08 
 
 12.49 
 
 8 
 
 I33I 
 
 16. 
 
 43 
 
 5 
 
 16. 
 
 85 
 
 20.71 
 
 
 
 
 
 7 
 
 13-38 
 
 16. 
 
 52 
 
 4 
 
 16. 
 
 92 
 
 20.80 
 
 0.9839 
 
 10 
 
 15 
 
 12.58 
 
 6 
 
 13.46 
 
 16. 
 
 61 
 
 3 
 
 17. 
 
 00 
 
 20.89 
 
 8 
 
 10 
 
 23 
 
 12.68 
 
 5 
 
 13-54 
 
 16. 
 
 7o 
 
 2 
 
 17- 
 
 08 
 
 20.99 
 
 7 
 
 10 
 
 3i 
 
 12.77 
 
 4 
 
 13.62 
 
 16. 
 
 80 
 
 1 
 
 17- 
 
 17 
 
 21.09 
 
 6 
 
 10 
 
 38 
 
 12.87 
 
 3 
 
 13.69 
 
 16 
 
 89 
 
 
 
 1725 
 
 21.19 
 

 APPENDIX A 
 TABLE X. — {Continued) 
 
 PERCENTAGE OF ALCOHOL 
 
 219 
 
 
 Per cent 
 
 Per cent 
 
 
 Per cent 
 
 Per cent 
 
 
 Per cent 
 
 Per cent 
 
 Sp. gr. 
 
 alcohol 
 
 alcohol 
 
 Sp. gr. 
 
 alcohol 
 
 alcohol 
 
 Sp. gr. 
 
 alcohol 
 
 alcohol 
 
 I5°.5 C. 
 
 by 
 
 by 
 
 I5°.5 C. 
 
 by 
 
 by 
 
 I5°.5C. 
 
 by 
 
 by 
 
 
 weight. 
 
 volume. 
 
 
 weight. 
 
 volume. 
 
 
 weight. 
 
 volume. 
 
 0.9749 
 
 17 33 
 
 21.29 
 
 6 
 
 20.00 
 
 24.48 
 
 3 
 
 22.62 
 
 27-59 
 
 8 
 
 17 
 
 42 
 
 20.39 
 
 5 
 
 20.08 
 
 24 
 
 58 
 
 2 
 
 22.69 
 
 27.68 
 
 7 
 
 17 
 
 50 
 
 21.49 
 
 4 
 
 20.17 
 
 24 
 
 68 
 
 I 
 
 22.77 
 
 27.77 
 
 6 
 
 17 
 
 58 
 
 21.59 
 
 3 
 
 20.25 
 
 24 
 
 78 
 
 O 
 
 22.85 
 
 27.86 
 
 5 
 
 17 
 
 67 
 
 21 .69 
 
 2 
 
 20.33 
 
 24 
 
 88 
 
 
 
 
 4 
 
 17 
 
 75 
 
 21-79 
 
 1 
 
 20.42 
 
 24 
 
 98 
 
 O.9679 
 
 22.92 
 
 27 95 
 
 3 
 
 17 
 
 S3 
 
 21.89 
 
 
 
 20.50 
 
 25 
 
 07 
 
 8 
 
 23.00 
 
 28 . 04 
 
 2 
 
 17 
 
 92 
 
 21.99 
 
 
 
 
 
 7 
 
 23.08 
 
 28.13 
 
 1 
 
 18 
 
 00 
 
 22.09 
 
 0.9709 
 
 20.58 
 
 25 
 
 17 
 
 6 
 
 23 15 
 
 28.22 
 
 
 
 18 
 
 08 
 
 22.18 
 
 8 
 
 20.67 
 
 25 
 
 27 
 
 5 
 
 23-23 
 
 28.31 
 
 
 
 
 
 7 
 
 20.75 
 
 25 
 
 37 
 
 4 
 
 23-31 
 
 28.41 
 
 0-9739 
 
 18 
 
 15 
 
 22.27 
 
 6 
 
 20 . 83 
 
 25 
 
 47 
 
 3 
 
 23-38 
 
 28.50 
 
 8 
 
 18 
 
 23 
 
 22.36 
 
 5 
 
 20.92 
 
 25 
 
 57 
 
 2 
 
 23.46 
 
 28.59 
 
 7 
 
 18 
 
 31 
 
 22.46 
 
 4 
 
 2I.OO 
 
 25 
 
 67 
 
 1 
 
 23-54 
 
 28.68 
 
 6 
 
 18 
 
 38 
 
 22.55 
 
 3 
 
 21.08 
 
 25 
 
 76 
 
 
 
 23.62 
 
 28.77 
 
 5 
 
 18 
 
 46 
 
 22.64 
 
 2 
 
 21.15 
 
 25 
 
 86 
 
 
 
 
 4 
 
 18 
 
 54 
 
 22-73 
 
 1 
 
 21.23 
 
 25 
 
 95 
 
 0.9669 
 
 2369 
 
 28.86 
 
 3 
 
 18 
 
 62 
 
 22.82 
 
 
 
 21.31 
 
 26 
 
 04 
 
 8 
 
 23-77 
 
 28.95 
 
 2 
 
 18 
 
 69 
 
 22.92 
 
 
 
 
 
 7 
 
 2385 
 
 29.04 
 
 1 
 
 18 
 
 77 
 
 23.OI 
 
 0.9699 
 
 21.38 
 
 26 
 
 13 
 
 6 
 
 23.92 
 
 29.13 
 
 
 
 18 
 
 85 
 
 23.IO 
 
 8 
 
 21.46 
 
 26 
 
 22 
 
 5 
 
 24.00 
 
 29.22 
 
 
 
 
 
 7 
 
 21-54 
 
 26 
 
 31 
 
 4 
 
 24.08 
 
 29.31 
 
 09729 
 
 18 
 
 92 
 
 23.19 
 
 6 
 
 21.62 
 
 26 
 
 40 
 
 3 
 
 2415 
 
 29.40 
 
 8 
 
 19 
 
 00 
 
 23.28 
 
 5 
 
 21 .69 
 
 26 
 
 49 
 
 2 
 
 24.23 
 
 29.49 
 
 7 
 
 19 
 
 08 
 
 23.38 
 
 4 
 
 21-77 
 
 26 
 
 58 
 
 1 
 
 24-31 
 
 29.58 
 
 6 
 
 19 
 
 17 
 
 23.48 
 
 3 
 
 21.85 
 
 26 
 
 67 
 
 
 
 24.38 
 
 29.67 
 
 5 
 
 19 
 
 25 
 
 2358 
 
 2 
 
 21.92 
 
 26 
 
 77 
 
 
 
 
 4 
 
 19 
 
 33 
 
 23.68 
 
 1 
 
 22.CO 
 
 26 
 
 86 
 
 0.9659 
 
 24.46 
 
 29.76 
 
 3 
 
 19 
 
 42 
 
 23.78 
 
 
 
 22.08 
 
 26 
 
 95 
 
 8 
 
 24-54 
 
 29.86 
 
 2 
 
 19 
 
 50 
 
 23-88 
 
 
 
 
 
 7 
 
 24.62 
 
 29-95 
 
 1 
 
 19 
 
 58 
 
 23.98 
 
 0.9689 
 
 22.15 
 
 27 
 
 04 
 
 6 
 
 24.69 
 
 30.04 
 
 
 
 19 
 
 67 
 
 24.08 
 
 8 
 
 22 . 23 
 
 27 
 
 13 
 
 5 
 
 24.77 
 
 30.13 
 
 
 
 
 
 7 
 
 22.31 
 
 27 
 
 22 
 
 4 
 
 24.85 
 
 30.22 
 
 O.0719 
 
 19 
 
 75 
 
 24.18 
 
 6 
 
 22.38 
 
 27 
 
 3i 
 
 3 
 
 24.92 
 
 30-31 
 
 8 
 
 19 
 
 83 
 
 24.28 
 
 5 
 
 22.46 
 
 27 
 
 40 
 
 2 
 
 25.00 
 
 30.40 
 
 7 
 
 19.92 
 
 24-38 
 
 4 
 
 22-54 
 
 27.49 
 
 
 
 
220 
 
 AIR, WATER, AND FOOD 
 
 TABLE XI 
 
 EXTRACT IN WINE 
 
 Per cent by Weight 
 (According to Windisch) 
 
 Sp.gr. 
 
 Ex- 
 
 Sp.gr. 
 
 Ex- 
 
 Sp. gr. 
 
 Ex- 
 
 Sp.gr. 
 
 Ex- 
 
 Sp.gr. 
 
 Ex- 
 
 Sp. gr. 
 
 Ex- 
 
 
 tract. 
 
 
 tract. 
 
 
 tract. 
 
 
 tract. 
 
 
 tract. 
 
 
 tract. 
 
 I.OOOO 
 
 0.00 
 
 1 . 0200 
 
 5.17 
 
 1 . 0400 
 
 10.35 
 
 1 . 0600 
 
 15.55 
 
 1.0800 
 
 20.78 
 
 1. 1000 
 
 26.04 
 
 i. coos 
 
 0.13 
 
 1 . 0205 
 
 530 
 
 1.0405 
 
 10.48 
 
 1 . 0605 
 
 15-68 
 
 1.0805 
 
 20.91 
 
 1. 1005 
 
 26.17 
 
 I.OOIO 
 
 0.26 
 
 1. 0210 
 
 5-43 
 
 1. 0410 
 
 10.61 
 
 1. 0610 
 
 15.81 
 
 1. 0810 
 
 21.04 
 
 I.IOIO 
 
 26.30 
 
 1. 0015 
 
 0.39 
 
 1. 0215 
 
 5.56 
 
 1. 0415 
 
 10.74 
 
 1. 0615 
 
 15.94 
 
 1. 0815 
 
 21.17 
 
 1.1015 
 
 26.43 
 
 1.0020 
 
 0.52 
 
 1 . 0220 
 
 569 
 
 1 . 0420 
 
 10.87 
 
 1 . 0620 
 
 16.07 
 
 1.0820 
 
 21.31 
 
 1 . 1020 
 
 26.56 
 
 1.0025 
 
 0.64 
 
 1.0225 
 
 582 
 
 1.0425 
 
 11.00 
 
 1.0625 
 
 16.21 
 
 1.0825 
 
 21.44 
 
 1 . 1025 
 
 26.70 
 
 1.0030 
 
 0.77 
 
 1.0230 
 
 594 
 
 1.0430 
 
 11. 13 
 
 1.0630 
 
 i6.33 
 
 1.0830 
 
 21.57 
 
 1 . 1030 
 
 26.83 
 
 1.0035 
 
 0.90 
 
 1.0235 
 
 6.07 
 
 1043s 
 
 11.26 
 
 10635 
 
 16.47 
 
 1.083S 
 
 21.70 
 
 1. 1035 
 
 26.96 
 
 1.0040 
 
 1.03 
 
 1 . 0240 
 
 6.20 
 
 1 . 0440 
 
 11.39 
 
 1 . 0640 
 
 16.60 
 
 1.0840 
 
 21.83 
 
 1 . 1040 
 
 27.00 
 
 I . 0045 
 
 1. 16 
 
 1.024s 
 
 6.33 
 
 1.0445 
 
 11.52 
 
 1 . 0645 
 
 16.73 
 
 1.0845 
 
 21.96 
 
 1 -1045 
 
 27.22 
 
 1.0050 
 
 1.29 
 
 1.0250 
 
 6?46 
 
 1.0450 
 
 11.65 
 
 1 . 0650 
 
 16.86 
 
 1.0850 
 
 22.09 
 
 I . 1050 
 
 27.35 
 
 1.0055 
 
 1.42 
 
 1.0255 
 
 6.59 
 
 1.045s 
 
 11.78 
 
 1.065S 
 
 16.99 
 
 10855 
 
 22.22 
 
 1. 1055 
 
 27.49 
 
 I . 0060 
 
 155 
 
 1 . 0260 
 
 6.72 
 
 1.0460 
 
 11. 91 
 
 1 . 0660 
 
 17.12 
 
 1.0860 
 
 22.36 
 
 1. 1060 
 
 27.62 
 
 1.0065 
 
 1.68 
 
 1.0265 
 
 6.85 
 
 1.0465 
 
 12.04 
 
 1 . 0665 
 
 1725 
 
 1.0865 
 
 22.49 
 
 1 . 1065 
 
 27-75 
 
 1.0070 
 
 1. 81 
 
 1 . 0270 
 
 '6 : 98 
 
 .1 ■ 0470 
 
 12.17 
 
 1 . 0670 
 
 17.38 
 
 1 . 0870 
 
 22.62 
 
 1. 1070 
 
 27.88 
 
 1.0075 
 
 1 94 
 
 1.0275 
 
 7Tn 
 
 1.0475 
 
 12.30 
 
 1.067S 
 
 I7.5I 
 
 1.087s 
 
 22.75 
 
 1. 1075 
 
 28. or 
 
 1.0080 
 
 2.07 
 
 1 . 0280 
 
 7*24 
 
 1 . 0480 
 
 12.43 
 
 1.0680 
 
 17.64 
 
 1.0880 
 
 22.88 
 
 1. 1080 
 
 28. is 
 
 I . 0085 
 
 2.19 
 
 1.0285 
 
 J. 37 
 
 1.0485 
 
 12.56 
 
 1.0685 
 
 17-77 
 
 1.0885 
 
 23.01 
 
 1 . 1085 
 
 28.28 
 
 1.0090 
 
 2.32 
 
 1 . 0290 
 
 Y'.50 
 
 1 . 0490 
 
 12.69 
 
 1 . 0690 
 
 17.90 
 
 1 . 0890 
 
 2314 
 
 1. 1090 
 
 28.41 
 
 1.0095 
 
 2.45 
 
 1.0295 
 
 763 
 
 1.0495 
 
 12.82 
 
 1.0695 
 
 18.03 
 
 1.0895 
 
 2328 
 
 1. 1095 
 
 28.54 
 
 I . 0100 
 
 2.58 
 
 1.0300 
 
 7-76 
 
 1.0500 
 
 12.95 
 
 1.0700 
 
 18.16 
 
 1 . 0900 
 
 23.41 
 
 I.IIOO 
 
 28.67 
 
 I . 0105 
 
 2.71 
 
 1. 0305 
 
 7.89 
 
 1. 0505 
 
 1308 
 
 1.0705 
 
 18.30 
 
 1.0905 
 
 23.54 
 
 1.1105 
 
 28.81 
 
 I. OIIO 
 
 2.84 
 
 1. 0310 
 
 8.02 
 
 1. 0510 
 
 1321 
 
 1. 0710 
 
 18.43 
 
 1. 0910 
 
 23.67 
 
 I.IIIO 
 
 28.94 
 
 1.0115 
 
 2.97 
 
 1. 0315 
 
 8.14 
 
 1. 0515 
 
 13-34 
 
 1. 0715 
 
 18.56 
 
 1-0915 
 
 23.80 
 
 1. HIS 
 
 29.07 
 
 I. 0120 
 
 310 
 
 1.0320 
 
 8.27 
 
 1.0520 
 
 13-47 
 
 1.0720 
 
 18.69 
 
 1.0920 
 
 23-93 
 
 1.1120 
 
 29.20 
 
 I. 0125 
 
 323 
 
 1.0325 
 
 8.40 
 
 10525 
 
 1360 
 
 1.0725 
 
 18.82 
 
 1.0925 
 
 24.07 
 
 1.1125 
 
 29.33 
 
 I. 0130 
 
 3.36 
 
 10330 
 
 8.53 
 
 1.0530 
 
 13.73 
 
 1.0730 
 
 18.95 
 
 1 . 0930 
 
 24.20 
 
 1.1130 
 
 29-47 
 
 I. 0135 
 
 3-49 
 
 1.0335 
 
 8.66 
 
 1-0535 
 
 13-86 
 
 I.0735 
 
 19.08 
 
 1 0935 
 
 2433 
 
 I.H35 
 
 29.60 
 
 I. 0140 
 
 3-62 
 
 1.0340 
 
 8.79 
 
 1 . 0540 
 
 13.99 
 
 1.0740 
 
 19.21 
 
 1 . 0940 
 
 24.46 
 
 1.1140 
 
 29.73 
 
 I. 0145 
 
 3-75 
 
 1.0345 
 
 8.92 
 
 1.0545 
 
 14.12 
 
 1.0745 
 
 1934 
 
 1.0945 
 
 2459 
 
 I.H45 
 
 29.86 
 
 I. 0150 
 
 3.87 
 
 1.0350 
 
 905 
 
 1.0550 
 
 14.25 
 
 1.0750 
 
 19-47 
 
 1.0950 
 
 24.72 
 
 1.1150 
 
 29.99 
 
 I. 0155 
 
 4.00 
 
 1.0355 
 
 9.18 
 
 I.OS55 
 
 14.38 
 
 I.0755 
 
 19.60 
 
 1. 0955 
 
 24.85 
 
 I.H55 
 
 30.13 
 
 I. 0160 
 
 4.13 
 
 1 . 0360 
 
 9-31 
 
 1.0560 
 
 14.51 
 
 1 . 0760 
 
 1973 
 
 1 . 0960 
 
 2499 
 
 
 
 I. 0165 
 
 4.26 
 
 10365 
 
 9-44 
 
 1.056s 
 
 14.64 
 
 1.0765 
 
 19.86 
 
 1 . 0965 
 
 25.12 
 
 
 
 I. 0170 
 
 4-39 
 
 1.0370 
 
 9-57 
 
 1.0570 
 
 14.77 
 
 1.0770 
 
 20.00 
 
 1 . 0970 
 
 25.25 
 
 
 
 10T75 
 
 4-52 
 
 1.0375 
 
 9- 70 
 
 1. 0575 
 
 14.90 
 
 1.0775 
 
 20.12 
 
 10975 
 
 25.38 
 
 
 
 1. 0180 
 
 4.65 
 
 1.0380 
 
 9.83 
 
 1.0580 
 
 15.03 
 
 1 . 0780 
 
 20.26 
 
 1.0980 
 
 25.51 
 
 
 
 1. 0185 
 
 4.78 
 
 1.0385 
 
 996 
 
 1.058S 
 
 15- 16 
 
 1.0785 
 
 20.39 
 
 1.0985 
 
 25.64 
 
 
 
 1. 0190 
 
 4-91 
 
 1.0390 
 
 10.09 
 
 1.0590 
 
 1529 
 
 1 . 0790 
 
 20.52 
 
 1 . 0990 
 
 25-78 
 
 
 
 1. 0195 
 
 5.04 
 
 I. 0395 
 
 10.22 
 
 1. o59S 
 
 15.42 
 
 1.0795 
 
 20.65 
 
 1 0995 
 
 25.91 
 
 
 
APPENDIX A 
 
 221 
 
 TABLE XII 
 
 TABLE FOR REDUCING SUGAR CONDENSED FROM THAT OF 
 MUNSON AND WALKER 
 
 (Expressed in milligrams) 
 
 
 
 
 
 
 
 12 
 
 °o 
 
 So 
 
 aj 
 w 
 
 2 
 p 
 
 bO 
 
 w 
 u 
 
 > 
 
 *5 
 
 H 
 
 &6 
 
 O 
 
 
 t— 1 
 
 
 
 
 10 
 
 4-0 
 
 4-5 
 
 4.0 
 
 5.9 
 
 15 
 
 6.2 
 
 6.7 
 
 7.5 
 
 99 
 
 20 
 
 8.3 
 
 8.9 
 
 10.9 
 
 13.8 
 
 25 
 
 10.5 
 
 n. 2 
 
 14.4 
 
 17.8 
 
 30 
 
 12.6 
 
 13-4 
 
 17.8 
 
 21.8 
 
 35 
 
 14.8 
 
 15.6 
 
 21.3 
 
 25-7 
 
 40 
 
 16.9 
 
 17.8 
 
 24.8 
 
 297 
 
 45 
 
 19. 1 
 
 20.1 
 
 28.2 
 
 337 
 
 5o 
 
 21.3 
 
 22.3 
 
 31 -7 
 
 37.6 
 
 55 
 
 23.5 
 
 24.6 
 
 35- 1 
 
 41.6 
 
 60 
 
 25.6 
 
 26.8 
 
 38.6 
 
 45-6 
 
 65 
 
 27.8 
 
 29.1 
 
 42.1 
 
 495 
 
 70 
 
 30.0 
 
 313 
 
 45-5 
 
 535 
 
 75 
 
 32.2 
 
 33-6 
 
 49-0 
 
 57-5 
 
 80 
 
 34-4 
 
 359 
 
 52.5 
 
 61.4 
 
 85 
 
 36.7 
 
 38.2 
 
 56.0 
 
 654 
 
 90 
 
 38.9 
 
 40.4 
 
 59-4 
 
 693 
 
 95 
 
 41. 1 
 
 42.7 
 
 62.9 
 
 733 
 
 100 
 
 433 
 
 45.o 
 
 66.4 
 
 77-3 
 
 105 
 
 45-5 
 
 47-3 
 
 69.8 
 
 81.2 
 
 no 
 
 47-8 
 
 49-6 
 
 73-3 
 
 85.2 
 
 115 
 
 50.0 
 
 51.9 
 
 76.8 
 
 89.2 
 
 120 
 
 52-3 
 
 54-3 
 
 80.3 
 
 93- 1 
 
 125 
 
 54-5 
 
 56.6 
 
 83.8 
 
 971 
 
 130 
 
 56.8 
 
 58.9 
 
 87.3 
 
 IOI.O 
 
 135 
 
 59-0 
 
 61.2 
 
 90.8 
 
 105.0 
 
 140 
 
 61.3 
 
 63.6 
 
 942 
 
 109.0 
 
 145 
 
 63.6 
 
 65-9 
 
 977 
 
 112. 9 
 
 150 
 
 65-9 
 
 68.3 
 
 101.2 
 
 116. 9 
 
 155 
 
 68.2 
 
 70.6 
 
 104.7 
 
 120.8 
 
 160 
 
 70.4 
 
 73-0 
 
 108.2 
 
 124.8 
 
 165 
 
 72.8 
 
 75-3 
 
 ill. 7 
 
 128.8 
 
 170 
 
 75.1 
 
 77-7 
 
 115 2 
 
 132.7 
 
 175 
 
 77-4 
 
 80.1 
 
 118. 7 
 
 136.7 
 
 180 
 
 79-7 
 
 82.5 
 
 122.2 
 
 140.6 
 
 185 
 
 84.2 
 
 849 
 
 125-7 
 
 1446 
 
 190 
 
 843 
 
 87.2 
 
 129.2 
 
 148.6 
 
 195 
 
 86.7 
 
 89.6 
 
 132.7 
 
 152.5 
 
 200 
 
 89.0 
 
 92.0 
 
 1362 
 
 156.5 
 
 205 
 
 91.4 
 
 945 
 
 139-7 
 
 160.4 
 
 210 
 
 93-7 
 
 96.9 
 
 143.2 
 
 164.4 
 
 215 
 
 96.1 
 
 993 
 
 146.7 
 
 168.3 
 
 220 
 
 98.4 
 
 101.7 
 
 150.2 
 
 172.3 
 
 225 
 
 100.8 
 
 104.2 
 
 153 7 
 
 176.2 
 
 230 
 
 103.2 
 
 106.6 
 
 157.2 
 
 180.2 
 
 235 
 
 105.6 
 
 109. 1 
 
 160.7 
 
 184.2 
 
 240 
 
 108.0 
 
 in. 5 
 
 164.3 
 
 188. 1 
 
 245 
 
 no. 4 
 
 114. 
 
 167.8 
 
 192. 1 
 
 250 
 
 112. 8 
 
 116. 4 
 
 I7I- 3 
 
 196.0 
 
 255 
 
 115. 2 
 
 118. 9 
 
 174-8 
 
 200.0 
 
 <u 
 
 
 
 q 
 
 
 I© 
 
 2 
 
 a 
 00 
 3 
 
 
 s 
 
 3 
 
 Q 
 
 C 
 > 
 
 "£0 
 
 *6 
 
 
 
 
 i— 1 
 
 
 
 
 260 
 
 117. 6 
 
 121. 4 
 
 178.3 
 
 203.9 
 
 265 
 
 120.0 
 
 1239 
 
 181. 9 
 
 207.9 
 
 270 
 
 122.5 
 
 I26.4 
 
 185.4 
 
 211. 8 
 
 275 
 
 124.9 
 
 128.9 
 
 188.9 
 
 215.8 
 
 280 
 
 1273 
 
 I3I-4 
 
 192.4 
 
 219.7 
 
 285 
 
 129.8 
 
 1339 
 
 196.0 
 
 223.7 
 
 290 
 
 132.3 
 
 136.4 
 
 199 .5 
 
 227.6 
 
 295 
 
 134.7 
 
 138.9 
 
 203.0 
 
 231.6 
 
 300 
 
 137-2 
 
 141. 5 
 
 206.6 
 
 235-5 
 
 305 
 
 139-7 
 
 I44-Q 
 
 210. 1 
 
 239.5 
 
 310 
 
 142.2 
 
 146.6 
 
 2137 
 
 2435 
 
 315 
 
 144.7 
 
 149- 1 
 
 217.2 
 
 247-4 
 
 320 
 
 147-2 
 
 151. 7 
 
 220.7 
 
 251-3 
 
 325 
 
 149-7 
 
 1543 
 
 224.3 
 
 2553 
 
 330 
 
 152.2 
 
 156.8 
 
 227.8 
 
 2593 
 
 335 
 
 154.7 
 
 1594 
 
 2314 
 
 263.2 
 
 340 
 
 157-3 
 
 162.0 
 
 234-9 
 
 267.1 
 
 345 
 
 159-8 
 
 164.6 
 
 238.5 
 
 271. 1 
 
 350 
 
 162.4 
 
 167.2 
 
 242.0 
 
 2750 
 
 355 
 
 164.9 
 
 169.8 
 
 245.6 
 
 279.0 
 
 360 
 
 167.5 
 
 172.5 
 
 249.1 
 
 282.9 
 
 365 
 
 170. 1 
 
 175. 1 
 
 252.7 
 
 286.9 
 
 370 
 
 172.7 
 
 177.7 
 
 256.2 
 
 290.8 
 
 375 
 
 175-3 
 
 180.4 
 
 2598 
 
 294.8 
 
 380 
 
 1779 
 
 183.0 
 
 263.4 
 
 298.7 
 
 385 
 
 180.5 
 
 185.7 
 
 266.9 
 
 302.7 
 
 390 
 
 183. 1 
 
 188.4 
 
 270.5 
 
 306.6 
 
 395 
 
 185.7 
 
 191. 
 
 274-0 
 
 310.6 
 
 400 
 
 188.4 
 
 1937 
 
 277.6 
 
 314-5 
 
 405 
 
 191. 
 
 196.4 
 
 281. 1 
 
 318.5 
 
 410 
 
 1937 
 
 199- 1 
 
 284.7 
 
 322.4 
 
 415 
 
 196.3 
 
 201.8 
 
 288.3 
 
 326.3 
 
 420 
 
 199 
 
 204.6 
 
 291.9 
 
 330.3 
 
 425 
 
 201.7 
 
 207.3 
 
 295-4 
 
 3342 
 
 430 
 
 204.4 
 
 210.0 
 
 299.0 
 
 338.2 
 
 435 
 
 207.1 
 
 212.8 
 
 302.6 
 
 342.1 
 
 440 
 
 209.8 
 
 2155 
 
 306.2 
 
 346.1 
 
 445 
 
 212.5 
 
 218.3 
 
 309-7 
 
 350.0 
 
 450 
 
 2152 
 
 221. 1 
 
 313 3 
 
 3539 
 
 455 
 
 218.0 
 
 223.9 
 
 316.9 
 
 357-9 
 
 460 
 
 220.7 
 
 226.7 
 
 320.5 
 
 361.8 
 
 465 
 
 223.5 
 
 229.5 
 
 324- 1 
 
 365.8 
 
 470 
 
 226.2 
 
 232.3 
 
 327-7 
 
 369-7 
 
 475 
 
 229.0 
 
 235.1 
 
 331.3 
 
 3737 
 
 480 
 
 231.8 
 
 2379 
 
 3348 
 
 377-6 
 
 485 
 
 234-6 
 
 240.8 
 
 338.4 
 
 381.5 
 
 490 
 
 237-4 
 
 2436 
 
 342.0 
 
 385.5 
 
222 
 
 AIR, WATER, AND FOOD 
 
 TABLE XIII 
 
 EXTRACT IN BEER-WORT 
 
 (According to Schultz and Ostermann) 
 
 Specific 
 
 Extract. S 
 
 pecific 
 
 Extract. Si 
 
 jecific 
 
 Extract. S] 
 
 )ecific 
 
 Extract. 
 
 gravity at 
 
 Per cent gn 
 
 ivity at 
 
 Per cent gra 
 
 vity at 
 
 Per cent gra 
 
 vity at 
 
 Per cent 
 
 15° C. 
 
 by weight. j 
 
 5°C. 
 
 by weight. 1 
 
 5°C. 
 
 by weight. 1 
 
 5°C. 
 
 by weight. 
 
 I . oooo 
 
 O.OO 1 
 
 0235 
 
 6.07 I 
 
 0470 
 
 11.89 1 
 
 0705 
 
 17-59 
 
 I . 0005 
 
 O 
 
 13 1 
 
 0240 
 
 6 
 
 19 1 
 
 0475 
 
 12 
 
 OI I 
 
 0710 
 
 17.70 
 
 I .0010 
 
 O 
 
 26 1 
 
 0245 
 
 6 
 
 3i 1 
 
 0480 
 
 12 
 
 14 I 
 
 0715 
 
 17.81 
 
 I. 0015 
 
 O 
 
 39 1 
 
 0250 
 
 6 
 
 44 1 
 
 0485 
 
 12 
 
 26 I 
 
 0720 
 
 17-93 
 
 I .0020 
 
 O 
 
 52 1 
 
 0255 
 
 6 
 
 58 1 
 
 0490 
 
 12 
 
 38 I 
 
 0725 
 
 18.04 
 
 I .0025 
 
 O 
 
 66 1 
 
 0260 
 
 6 
 
 71 1 
 
 0495 
 
 12 
 
 50 I 
 
 0730 
 
 18.15 
 
 I . 0030 
 
 O 
 
 79 1 
 
 0265 
 
 6 
 
 85 1 
 
 0500 
 
 . 12 
 
 63 I 
 
 0735 
 
 18.26 
 
 1.003s 
 
 O 
 
 92 1 
 
 0270 
 
 6 
 
 99 1 
 
 0505 
 
 12 
 
 75 1 
 
 0740 
 
 18.38 
 
 I . 0040 
 
 1 
 
 05 1 
 
 0275 
 
 7 
 
 12 1 
 
 0510 
 
 12 
 
 87 1 
 
 0745 
 
 18.49 
 
 1.0045 
 
 I 
 
 18 1 
 
 0280 
 
 7 
 
 26 1 
 
 05I5 
 
 12 
 
 99 1 
 
 0750 
 
 18.59 
 
 I .0050 
 
 I 
 
 3i 1 
 
 0285 
 
 7 
 
 37 1 
 
 0520 
 
 13 
 
 12 1 
 
 0755 
 
 18.70 
 
 * -0055 
 
 1 
 
 44 1 
 
 0290 
 
 7 
 
 48 1 
 
 0525 
 
 13 
 
 24 1 
 
 0760 
 
 18.81 
 
 I . 0060 
 
 I 
 
 56 1 
 
 0295 
 
 7 
 
 60 1 
 
 0530 
 
 13 
 
 36 1 
 
 0765 
 
 18.91 
 
 I .0065 
 
 I 
 
 69 1 
 
 0300 
 
 7 
 
 71 1 
 
 0535 
 
 13 
 
 48 1 
 
 0770 
 
 19.02 
 
 J .0070 
 
 I 
 
 82 1 
 
 0305 
 
 7 
 
 82 1 
 
 0540 
 
 13 
 
 61 1 
 
 0775 
 
 19.12 
 
 1.0075 
 
 1 
 
 95 1 
 
 0310 
 
 7 
 
 93 1 
 
 0545 
 
 13 
 
 73 1 
 
 0780 
 
 19.23 
 
 I . 0080 
 
 2 
 
 07 1 
 
 0315 
 
 8 
 
 04 1 
 
 0550 
 
 13 
 
 86 1 
 
 0785 
 
 19-33 
 
 1.0085 
 
 2 
 
 20 1 
 
 0320 
 
 8 
 
 16 1 
 
 0555 
 
 13 
 
 98 1 
 
 0790 
 
 19.44 
 
 I . 0090 
 
 2 
 
 33 1 
 
 0325 
 
 8 
 
 27 1 
 
 0560 
 
 M 
 
 11 1 
 
 0795 
 
 19.56 
 
 1.0095 
 
 2 
 
 46 1 
 
 0330 
 
 8 
 
 40 1 
 
 O505 
 
 14 
 
 23 1 
 
 0800 
 
 19.67 
 
 I .0100 
 
 2 
 
 58 1 
 
 0335 
 
 8 
 
 53 1 
 
 0570 
 
 14 
 
 36 1 
 
 0805 
 
 19.79 
 
 I. 0105 
 
 2 
 
 71 1 
 
 0340 
 
 8 
 
 67 1 
 
 0575 
 
 14 
 
 49 1 
 
 0810 
 
 19.91 
 
 I .0110 
 
 2 
 
 84 1 
 
 0345 
 
 8 
 
 80 1 
 
 0580 
 
 14 
 
 62 1 
 
 0815 
 
 20.03 
 
 1.0115 
 
 2 
 
 97 1 
 
 0350 
 
 8 
 
 94 1 
 
 0585 
 
 14 
 
 75 1 
 
 0820 
 
 20.14 
 
 I .0120 
 
 3 
 
 10 1 
 
 0355 
 
 9 
 
 07 1 
 
 0590 
 
 14 
 
 89 1 
 
 0825 
 
 20.26 
 
 I. 0125 
 
 3 
 
 23 1 
 
 0360 
 
 9 
 
 21 1 
 
 °595 
 
 15 
 
 02 1 
 
 0830 
 
 20.37 
 
 I. 0130 
 
 3 
 
 35 1 
 
 0365 
 
 9 
 
 34 1 
 
 0600 
 
 15 
 
 14 1 
 
 0835 
 
 20.48 
 
 I 0135 
 
 3 
 
 48 1 
 
 0370 
 
 9 
 
 45 1 
 
 0605 
 
 15 
 
 25 1 
 
 0840 
 
 20.59 
 
 I. 0140 
 
 3 
 
 61 1 
 
 0375 
 
 9 
 
 57 1 
 
 0610 
 
 15 
 
 36 1 
 
 0845 
 
 20.70 
 
 I. 0145 
 
 3 
 
 74 1 
 
 0380 
 
 9 
 
 69 1 
 
 0615 
 
 15 
 
 47 1 
 
 0850 
 
 20.81 
 
 I. 0150 
 
 3 
 
 87 1 
 
 038S 
 
 9 
 
 81 1 
 
 0620 
 
 15 
 
 58 1 
 
 0855 
 
 20.93 
 
 I. 0155 
 
 4 
 
 00 1 
 
 0390 
 
 9 
 
 92 1 
 
 0625 
 
 15 
 
 69 1 
 
 0860 
 
 21 .06 
 
 I .0160 
 
 4 
 
 13 1 
 
 0395 
 
 10 
 
 04 1 
 
 0630 
 
 15 
 
 80 1 
 
 0865 
 
 21.19 
 
 1.016s 
 
 4 
 
 26 1 
 
 04OO 
 
 10 
 
 16 1 
 
 0635 
 
 15 
 
 92 1 
 
 0870 
 
 21-33 
 
 I .0170 
 
 4 
 
 39 1 
 
 0405 
 
 10 
 
 27 1 
 
 0640 
 
 16 
 
 03 1 
 
 0875 
 
 21-43 
 
 :1.017s 
 
 4 
 
 53 1 
 
 0410 
 
 10 
 
 40 1 
 
 0645 
 
 16 
 
 14 1 
 
 0880 
 
 21-54 
 
 I. 0180 
 
 4 
 
 66 1 
 
 0415 
 
 10 
 
 52 1 
 
 0650 
 
 16 
 
 25 1 
 
 0885 
 
 21 .64 
 
 1.0185 
 
 4 
 
 79 1 
 
 0420 
 
 10 
 
 65 1 
 
 0655 
 
 16 
 
 37 1 
 
 0890 
 
 21-75 
 
 I .0190 
 
 4 
 
 93 1 
 
 0425 
 
 10 
 
 '7 1 
 
 0660 
 
 16 
 
 50 1 
 
 0895 
 
 21.86 
 
 1.019s 
 
 5 
 
 06 1 
 
 0430 
 
 10 
 
 90 1 
 
 0665 
 
 16 
 
 62 1 
 
 0900 
 
 21.98 
 
 1.0200 
 
 5 
 
 20 1 
 
 0435 
 
 11 
 
 03 1 
 
 0670 
 
 16 
 
 74 1 
 
 0905 
 
 22.08 
 
 1.0205 
 
 5 
 
 33 1 
 
 0440 
 
 11 
 
 15 1 
 
 0675 
 
 16 
 
 86 1 
 
 0910 
 
 22.19 
 
 I. 0210 
 
 5 
 
 45 1 
 
 0445 
 
 11 
 
 28 1 
 
 0680 
 
 16 
 
 99 1 
 
 09I5 
 
 22.30 
 
 I. 0215 
 
 5 
 
 57 1 
 
 0450 
 
 11 
 
 40 1 
 
 0685 
 
 17 
 
 11 1 
 
 0920 
 
 22.41 
 
 I .0220 
 
 5 
 
 70 1 
 
 0455 
 
 11 
 
 53 1 
 
 0690 
 
 17 
 
 23 1 
 
 0925 
 
 22.52 
 
 I .0225 
 
 5 
 
 82 1 
 
 0460 
 
 11 
 
 65 1 
 
 0695 
 
 17 
 
 35 1 
 
 0930 
 
 22.63 
 
 1.0230 
 
 5 
 
 94 1 
 
 0465 
 
 11 
 
 77 1 
 
 0700 
 
 17 
 
 48 1 
 
 0935 
 
 22.73 
 
APPENDIX A 
 
 223 
 
 TABLE XIII. — (Continued) 
 
 EXTRACT IN BEER-WORT 
 
 (According to Schultz and Ostermann) 
 
 Specific 
 
 Extract. 
 
 Specific 
 
 Extract. 
 
 Specific 
 
 Extract. 
 
 Specific 
 
 Extract. 
 
 gravity at 
 
 Per cent 
 
 gravity at 
 
 Per cent 
 
 gravity at 
 
 Per cent 
 
 gravity at 
 
 Per cent 
 
 15° C. 
 
 by weight. 
 
 15° C. 
 
 by weight. 
 24-53 
 
 15° C. 
 
 by weight. 
 
 15° C. 
 
 by weight. 
 
 I . 0940 
 
 22.84 
 
 I . 1020 
 
 I . I 100 
 
 26.27 
 
 I. I 180 
 
 27.88 
 
 I 
 
 •0945 
 
 22 
 
 94 
 
 1. 1025 
 
 24.64 
 
 I.1105 
 
 26.37 
 
 I.H85 
 
 27.98 
 
 I 
 
 0950 
 
 23 
 
 05 
 
 I . 1030 
 
 24.74 
 
 I.IIIO 
 
 26.48 
 
 I .1190 
 
 28.09 
 
 I 
 
 0955 
 
 23 
 
 16 
 
 1 I035 
 
 24.85 
 
 1. iiiS 
 
 26.58 
 
 I.1195 
 
 28.19 
 
 I 
 
 0960 
 
 23 
 
 27 
 
 I . 1040 
 
 24.96 
 
 1 . 1 1 20 
 
 26.68 
 
 I. I200 
 
 28.28 
 
 I 
 
 0965 
 
 23 
 
 37 
 
 1 • 1045 
 
 25.07 
 
 1.1125 
 
 26. 79 
 
 1-1205 
 
 28.38 
 
 I 
 
 0970 
 
 23 
 
 48 
 
 I . 1050 
 
 25.18 
 
 1-1130 
 
 26.89 
 
 I .I2IO 
 
 28.48 
 
 I 
 
 0975 
 
 23 
 
 59 
 
 1 -IQ55 
 
 25.29 
 
 I-H35 
 
 26.99 
 
 I.1215 
 
 28.58 
 
 I 
 
 0980 
 
 23 
 
 69 
 
 I . 1060 
 
 25.40 
 
 1.1140 
 
 27.09 
 
 I .1220 
 
 28.68 
 
 I 
 
 0985 
 
 23 
 
 80 
 
 1 ■ 1065 
 
 25-50 
 
 1.1145 
 
 27.19 
 
 1. 1225 
 
 28.78 
 
 I 
 
 0990 
 
 23 
 
 90 
 
 I . 1070 
 
 25.61 
 
 1-1150 
 
 27.29 
 
 1. 1230 
 
 28.88 
 
 I 
 
 0995 
 
 24 
 
 01 
 
 1. 1075 
 
 25-71 
 
 III55 
 
 27.38 
 
 1-1235 
 
 28.98 
 
 I 
 
 IOOO 
 
 24 
 
 11 
 
 I . 1080 
 
 25.82 
 
 1 . 1 160 
 
 27.48 
 
 1 . 1 240 
 
 29.08 
 
 I 
 
 1005 
 
 24 
 
 21 
 
 1 . 1085 
 
 25-93 
 
 1-1165 
 
 27.58 
 
 1. 1245 
 
 29.18 
 
 I 
 
 IOIO 
 
 24 
 
 32 
 
 I . 1090 
 
 26.05 
 
 1.1170 
 
 27.68 
 
 1-1250 
 
 29.28 
 
 I 
 
 1015 
 
 24 
 
 43 
 
 I . 1095 
 
 26.16 
 
 1. "75 
 
 27.78 
 
 1 -1255 
 
 29.38 
 
224 
 
 AIR, WATER, AND FOOD 
 
 
 
 
 
 LOGARITHMS 
 
 OF 
 
 NUMBERS 
 
 
 
 
 
 
 Natural 
 num- 
 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 Proportional parts. 
 
 bers. 
 
 4 
 4 
 3 
 3 
 3 
 
 2 
 
 8 
 8 
 7 
 6 
 6 
 
 3 
 
 12 
 11 
 
 10 
 10 
 9 
 
 4 5 6 
 
 17 21 25 
 15 19 23 
 14 17 21 
 13 l6 19 
 12 15 18 
 
 789 
 
 IO 
 II 
 12 
 13 
 14 
 
 0000 
 0414 
 0792 
 
 ii39 
 146 1 
 
 0043 
 
 0453 
 0828 
 
 "73 
 1492 
 
 0086 
 0492 
 0864 
 1206 
 1523 
 
 0128 
 
 0531 
 0899 
 1239 
 
 1553 
 
 0170 
 0569 
 
 0934 
 1271 
 
 1584 
 
 0212 
 0607 
 0969 
 
 I303 
 1614 
 
 0253 
 0645 
 1004 
 
 1335 
 1644 
 
 0294 
 0682 
 1038 
 1367 
 1673 
 
 0334 
 0719 
 1072 
 
 1399 
 1703 
 
 0374 
 0755 
 1 106 
 
 I430 
 
 1732 
 
 29 33 37 
 263034 
 24 28 31 
 23 26 29 
 21 24 27 
 
 15 
 
 16 
 
 17 
 18 
 
 19 
 
 1761 
 2041 
 2304 
 
 2553 
 2788 
 
 1790 
 2068 
 2330 
 2577 
 2810 
 
 1818 
 
 2095 
 
 2355 
 2601 
 
 2833 
 
 1847 
 2122 
 2380 
 2625 
 2856 
 
 1875 
 2148 
 2405 
 2648 
 2878 
 
 1903 
 
 2175 
 2430 
 2672 
 2900 
 
 1931 
 
 2201 
 
 2455 
 2695 
 2923 
 
 1959 
 
 2227 
 2480 
 2718 
 2945 
 
 1987 
 2253 
 2504 
 2742 
 2967 
 
 2014 
 2279 
 
 2529 
 2765 
 2989 
 
 3 
 3 
 2 
 2 
 
 2 
 
 6 
 
 5 
 5 
 5 
 4 
 
 8 
 8 
 7 
 7 
 7 
 
 II 14 17 
 II 13 l6 
 10 12 15 
 
 9 12 14 
 9 11 13 
 
 20 22 25 
 18 21 24 
 17 20 22 
 16 19 21 
 16 18 20 
 
 20 
 21 
 22 
 
 23 
 24 
 
 3010 
 3222 
 
 3424 
 3617 
 3802 
 
 3032 
 3243 
 3444 
 3636 
 3820 
 
 3054 
 3263 
 3464 
 3655 
 3838 
 
 3075 
 3284 
 3483 
 3674 
 3856 
 
 3096 
 3304 
 3502 
 3692 
 3874 
 
 3118 
 3324 
 3522 
 
 3711 
 3892 
 
 3139 
 3345 
 354i 
 3729 
 3909 
 
 3160 
 
 3365 
 356o 
 3747 
 3927 
 
 3181 
 
 3385 
 3579 
 3766 
 
 3945 
 
 3201 
 3404 
 3598 
 3784 
 3962 
 
 2 
 2 
 2 
 2 
 2 
 
 4 
 4 
 4 
 4 
 
 4 
 
 6 
 6 
 6 
 6 
 
 5 
 
 8ll 13 
 
 8 10 12 
 8 10 12 
 7 9 11 
 7 9 11 
 
 IS 17 19 
 
 14 16 18 
 14 15 17 
 13 15 17 
 12 14 16 
 
 25 
 26 
 
 27 
 28 
 
 29 
 
 3979 
 4150 
 4314 
 4472 
 4624 
 
 3997 
 4166 
 
 4330 
 4487 
 
 4639 
 
 4014 
 4183 
 4346 
 4502 
 4654 
 
 4031 
 4200 
 4362 
 4518 
 4669 
 
 4048 
 4216 
 4378 
 4533 
 4683 
 
 4065 
 
 4232 
 4393 
 4548 
 4698 
 
 4082 
 4249 
 4409 
 4564 
 4713 
 
 4099 
 4265 
 4425 
 4579 
 4728 
 
 4116 
 4281 
 4440 
 4594 
 4742 
 
 4133 
 
 4298 
 4456 
 4609 
 4757 
 
 2 
 2 
 2 
 2 
 
 I 
 
 3 
 3 
 3 
 3 
 
 3 
 
 5 
 5 
 5 
 5 
 4 
 
 7 9 10 
 7 8 10 
 689 
 689 
 679 
 
 12 14 15 
 11 13 15 
 11 13 14 
 11 12 14 
 10 12 13 
 
 30 
 31 
 32 
 
 33 
 34 
 
 477i 
 4914 
 
 5051 
 5185 
 5315 
 
 4786 
 4928 
 5065 
 5198 
 5328 
 
 4800 
 4942 
 
 5079 
 5211 
 5340 
 
 4814 
 4955 
 5092 
 5224 
 5353 
 
 4829 
 4969 
 5io5 
 5237 
 5366 
 
 4843 
 4983 
 5ii9 
 5250 
 5378 
 
 4857 
 4997 
 5132 
 5263 
 539i 
 
 4871 
 501 1 
 
 5145 
 5276 
 
 5403 
 
 4886 
 5024 
 5159 
 5289 
 54i6 
 
 4900 
 5038 
 5172 
 53°2 
 5428 
 
 I 
 I 
 I 
 
 I 
 I 
 
 3 
 3 
 3 
 3 
 
 3 
 
 4 
 4 
 4 
 4 
 4 
 
 679 
 678 
 5 7 8 
 568 
 568 
 
 to 11 13 
 
 CO II 12 
 9 II 12 
 9 10 12 
 9 10 ir 
 
 35 
 36 
 37 
 38 
 39 
 
 544i 
 5563 
 5682 
 
 5798 
 59 11 
 
 5453 
 5575 
 5694 
 5809 
 5922 
 
 5465 
 5587 
 5705 
 5821 
 5933 
 
 5478 
 5599 
 5717 
 5832 
 5944 
 
 549° 
 5611 
 
 5729 
 5843 
 5955 
 
 5502 
 5623 
 5740 
 5855 
 5966 
 
 5514 
 
 5635 
 5752 
 5866 
 5977 
 
 5527 
 5647 
 5763 
 5877 
 5988 
 
 5539 
 5658 
 
 5775 
 5888 
 
 5999 
 
 555i 
 
 5670 
 5786 
 
 5899 
 6010 
 
 I 
 I 
 
 I 
 I 
 I 
 
 2 
 2 
 2 
 2 
 2 
 
 4 
 4 
 3 
 3 
 3 
 
 567 
 567 
 567 
 567 
 4 5 7 
 
 9 10 II 
 8 10 11 
 8 9 10 
 8 9 10 
 8 9 10 
 
 40 
 4i 
 42 
 43 
 44 
 
 6021 
 6128 
 6232 
 6335 
 6435 
 
 6031 
 6138 
 6243 
 6345 
 6444 
 
 6042 
 6149 
 6253 
 6355 
 6454 
 
 6053 
 6160 
 6263 
 
 6365 
 6464 
 
 6064 
 6170 
 6274 
 
 6375 
 6474 
 
 6075 
 6180 
 6284 
 6385 
 6484 
 
 6085 
 6191 
 6294 
 6395 
 6493 
 
 6096 
 6201 
 6304 
 6405 
 6503 
 
 6107 
 6212 
 6314 
 6415 
 6513 
 
 6117 
 6222 
 
 6325 
 6425 
 6522 
 
 I 
 I 
 I 
 
 I 
 I 
 
 2 
 2 
 2 
 2 
 2 
 
 3 
 3 
 3 
 3 
 3 
 
 4 5 6 
 4 5 6 
 4 5 6 
 4 5 6 
 4 5 6 
 
 8 9 10 
 789 
 789 
 789 
 789 
 
 45 
 46 
 
 47 
 48 
 
 49 
 
 6532 
 6628 
 6721 
 6812 
 6902 
 
 6542 
 6637 
 6730 
 6821 
 691 1 
 
 655i 
 6646 
 
 6739 
 6830 
 6920 
 
 6561 
 6656 
 6749 
 6839 
 6928 
 
 6571 
 6665 
 6758 
 6848 
 6937 
 
 6580 
 6675 
 6767 
 6857 
 6946 
 
 6590 
 6684 
 6776 
 6866 
 6955 
 
 6599 
 6693 
 
 6785 
 6875 
 6964 
 
 6609 
 6702 
 6794 
 6884 
 6972 
 
 6618 
 6712 
 6803 
 
 6893 
 6981 
 
 I 
 
 I 
 I 
 I 
 
 I 
 
 2 
 
 2 
 2 
 2 
 2 
 
 3 
 3 
 3 
 3 
 3 
 
 4 5 6 
 4 5 6 
 
 4 5 5 
 4 4 5 
 4 4 5 
 
 789 
 7 7 8 
 678 
 678 
 6 7 8 
 
 5o 
 5i 
 52 
 53 
 54 
 
 6990 
 7076 
 7160 
 7243 
 7324 
 
 6998 
 7084 
 7168 
 7251 
 7332 
 
 7007 
 
 7093 
 7177 
 
 7259 
 734o 
 
 7016 
 7101 
 
 7185 
 7267 
 7348 
 
 7024 
 7110 
 7i93 
 
 7275 
 7356 
 
 7033 
 7118 
 7202 
 7284 
 7364 
 
 7042 
 7126 
 7210 
 7292 
 7372 
 
 7050 
 
 7135 
 7218 
 7300 
 738o 
 
 7059 
 7143 
 7226 
 73o8 
 7388 
 
 7067 
 7152 
 7235 
 73i6 
 7396 
 
 I 
 I 
 I 
 
 I 
 I 
 
 2 
 
 2 
 2 
 2 
 2 
 
 3 
 3 
 
 2 
 
 2 
 2 
 
 3 4 5 
 3 4 5 
 3 4 5 
 3 4 5 
 3 4 5 
 
 6 7 8 
 6 7 8 
 6 7 7 
 667 
 667 
 
APPENDIX A 
 
 225 
 
 
 
 
 
 LOGARITHMS 
 
 OF 
 
 NUMBERS 
 
 
 Natural 
 
 
 
 
 
 
 
 
 
 
 Proportic 
 
 jnal parts. 
 
 num- 
 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 
 bers. 
 
 
 7412 
 
 7419 
 
 
 
 
 
 7459 
 
 
 12 3 4 
 
 56789 
 
 55 
 
 7404 
 
 7427 
 
 7435 
 
 7443 
 
 7451 
 
 7466 
 
 7474 1223 
 
 45567 
 
 56 
 
 7482 
 
 7490 
 
 7497 
 
 7505 
 
 75i3 
 
 7520 
 
 7528 
 
 7536 
 
 7543 
 
 7551 1223 
 
 45567 
 
 57 
 
 7559 
 
 7566 
 
 7574 
 
 7582 
 
 7589 
 
 7597 
 
 7604 
 
 7612 
 
 7619 
 
 7627 1223 
 
 45567 
 
 58 
 
 7634 
 
 7642 
 
 7649 
 
 7657 
 
 7664 
 
 7672 
 
 7679 
 
 7686 
 
 7694 
 
 7701 1 1 2 3 
 
 44567 
 
 59 
 
 7709 
 
 7716 
 
 7723 
 
 773i 
 
 7738 
 
 7745 
 
 7752 
 
 7760 
 
 7767 
 
 7774 1 1 2 3 
 
 44567 
 
 60 
 
 7782 
 
 7789 
 
 7796 
 
 7803 
 
 7810 
 
 7818 
 
 7825 
 
 7832 
 
 7839 
 
 7846 1 2 3 
 
 4 4 5 6 6 
 
 61 
 
 7853 
 
 7860 
 
 7868 
 
 7875 
 
 7882 
 
 7889 
 
 7896 
 
 7903 
 
 7910 
 
 79 J 7 1 1 2 3 
 
 4 4 5 6 6 
 
 62 
 
 7924 
 
 793i 
 
 7938 
 
 7945 
 
 7952 
 
 7959 
 
 7966 
 
 7973 
 
 7980 
 
 7987 1 1 2 3 
 
 3 4 5 6 6 
 
 63 
 
 7993 
 
 8000 
 
 8007 
 
 8014 
 
 8021 
 
 8028 
 
 8035 
 
 8041 
 
 8048 
 
 8055 1 1 2 3 
 
 3 4 5 5 6 
 
 64 
 
 8062 
 
 8069 
 
 8075 
 
 8082 
 
 8089 
 
 8096 
 
 8102 
 
 8109 
 
 8116 
 
 8122 1 1 2 3 
 
 3 4 5 5 6 
 
 65 
 
 8129 
 
 8136 
 
 8142 
 
 8149 
 
 8156 
 
 8162 
 
 8169 
 
 8176 
 
 8182 
 
 8189 1 1 2 3 
 
 3 4 5 5 6 
 
 66 
 
 8i95 
 
 8202 
 
 8209 
 
 8215 
 
 8222 
 
 8228 
 
 8235 
 
 8241 
 
 8248 
 
 8254 1 1 2 3 
 
 3 4 5 5 6 
 
 67 
 
 8261 
 
 8267 
 
 8274 
 
 8280 
 
 8287 
 
 8293 
 
 8299 
 
 8306 
 
 8312 
 
 8319 1 1 2 3 
 
 3 4 5 5 6 
 
 68 
 
 8325 
 
 833i 
 
 8338 
 
 8344 
 
 835i 
 
 8357 
 
 8363 
 
 8370 
 
 8376 
 
 8382 1 1 2 3 
 
 3 4 4 5 6 
 
 69 
 
 8388 
 
 8395 
 
 8401 
 
 8407 
 
 8414 
 
 8420 
 
 8426 
 
 8432 
 
 8439 
 
 8445 1 1 2 2 
 
 3 4 4 5 6 
 
 70 
 
 8451 
 
 8457 
 
 8463 
 
 8470 
 
 8476 
 
 8482 
 
 8488 
 
 8494 
 
 8500 
 
 8506 1 1 2 2 
 
 3 4 4 5 6 
 
 7i 
 
 8513 
 
 8519 
 
 8525 
 
 8531 
 
 8537 
 
 8543 
 
 8549 
 
 8555 
 
 8561 
 
 8567 1 1 2 2 
 
 3 4 4 5 5 
 
 72 
 
 8573 
 
 8579 
 
 8585 
 
 8591 
 
 8597 
 
 8603 
 
 8609 
 
 8615 
 
 8621 
 
 8627 1 1 2 2 
 
 3 4 4 5 5 
 
 73 
 
 8633 
 
 8639 
 
 8645 
 
 8651 
 
 8657 
 
 8663 
 
 8669 
 
 8675 
 
 8681 
 
 8686 1 1 2 2 
 
 3 4 4 5 5 
 
 74 
 
 8692 
 
 8698 
 
 8704 
 
 8710 
 
 8716 
 
 8722 
 
 8727 
 
 8733 
 
 8739 
 
 8745 1 1 2 2 
 
 3 4 4 5 5 
 
 75 
 
 875i 
 
 8756 
 
 8762 
 
 8768 
 
 8774 
 
 8779 
 
 8785 
 
 8791 
 
 8797 
 
 8802 1 1 2 2 
 
 3 3 4 5 5 
 
 76 
 
 8808 
 
 8814 
 
 8820 
 
 8825 
 
 8831 
 
 8837 
 
 8842 
 
 8848 
 
 8854 
 
 8859 1 1 2 2 
 
 3 3 4 5 5 
 
 77 
 
 8865 
 
 8871 
 
 8876 
 
 8882 
 
 8887 
 
 8893 
 
 8899 
 
 8904 
 
 8910 
 
 8915 1 1 2 2 
 
 3 3 4 4 5 
 
 78 
 
 8921 
 
 8927 
 
 8932 
 
 8938 
 
 8943 
 
 8949 
 
 8954 
 
 8960 
 
 8965 
 
 8971 1 1 2 2 
 
 3 3 4 4 5 
 
 79 
 
 8976 
 
 8982 
 
 8987 
 
 8993 
 
 8998 
 
 9004 
 
 9009 
 
 9015 
 
 9020 
 
 9026 1 1 2 2 
 
 3 3 4 4 5 
 
 80 
 
 9031 
 
 9036 
 
 9042 
 
 9047 
 
 9053 
 
 9058 
 
 9063 
 
 9069 
 
 9074 
 
 9079 1 1 2 2 
 
 3 3 4 4 5 
 
 81 
 
 9085 
 
 9090 
 
 9096 
 
 9101 
 
 9106 
 
 9112 
 
 9117 
 
 9122 
 
 9128 
 
 9133 1 1 2 2 
 
 3 3 4 4 5 
 
 82 
 
 9138 
 
 9143 
 
 9149 
 
 9154 
 
 9159 
 
 9165 
 
 9170 
 
 9175 
 
 9180 
 
 9186 1 1 2 2 
 
 3 3 4 4 5 
 
 83 
 
 9191 
 
 9196 
 
 9201 
 
 9206 
 
 9212 
 
 9217 
 
 9222 
 
 9227 
 
 9232 
 
 9238 1 1 2 2 
 
 3 3 4 4 5 
 
 84 
 
 9243 
 
 9248 
 
 9253 
 
 9258 
 
 9263 
 
 9269 
 
 9274 
 
 9279 
 
 9284 
 
 9289 1 1 2 2 
 
 3 3 4 4 5 
 
 85 
 
 9294 
 
 9299 
 
 9304 
 
 9309 
 
 9315 
 
 9320 
 
 9325 
 
 9330 
 
 9335 
 
 9340 1 1 2 2 
 
 3 3 4 4 5 
 
 86 
 
 9345 
 
 935o 
 
 9355 
 
 9360 
 
 9365 
 
 937o 
 
 9375 
 
 9380 
 
 9385 
 
 9390 1 1 2 2 
 
 3 3 4 4 5 
 
 87 
 
 9395 
 
 9400 
 
 9405 
 
 9410 
 
 9415 
 
 9420 
 
 9425 
 
 9430 
 
 9435 
 
 9440 1 1 2 
 
 2 3 3 4 4 
 
 88 
 
 9445 
 
 945o 
 
 9455 
 
 9460 
 
 9465 
 
 9469 
 
 9474 
 
 9479 
 
 9484 
 
 9489 1 1 2 
 
 2 3 3 4 4 
 
 89 
 
 9494 
 
 9499 
 
 9504 
 
 9509 
 
 9513 
 
 95i8 
 
 9523 
 
 9528 
 
 9533 
 
 9538 1 1 2 
 
 2 3 3 4 4 
 
 90 
 
 9542 
 
 9547 
 
 9552 
 
 9557 
 
 9562 
 
 9566 
 
 957i 
 
 9576 
 
 958i 
 
 9586 1 1 2 
 
 2 3 3 4 4 
 
 9i 
 
 9590 
 
 9595 
 
 9600 
 
 9605 
 
 9609 
 
 9614 
 
 9619 
 
 9624 
 
 9628 
 
 9633 1 1 2 
 
 2 3 3 4 4 
 
 92 
 
 9638 
 
 9643 
 
 9647 
 
 9652 
 
 9657 
 
 9661 
 
 9666 
 
 9671 
 
 9675 
 
 9680 1 1 2 
 
 2 3 3 4 4 
 
 93 
 
 9685 
 
 9689 
 
 9694 
 
 9699 
 
 9703 
 
 9708 
 
 9713 
 
 9717 
 
 9722 
 
 9727 1 1 2 
 
 2 3 3 4- 
 
 94 
 
 973i 
 
 9736 
 
 974i 
 
 9745 
 
 975o 
 
 9754 
 
 9759 
 
 9763 
 
 9768 
 
 9773 1 1 2 
 
 2 3 3 4^! 
 
 95 
 
 9777 
 
 9782 
 
 9786 
 
 9791 
 
 9795 
 
 9800 
 
 9805 
 
 9809 
 
 9814 
 
 9818 1 1 2 
 
 2 3 3 4 4 
 
 96 
 
 9823 
 
 9827 
 
 9832 
 
 9836 
 
 9841 
 
 9845 
 
 9850 
 
 9854 
 
 9859 
 
 9863 1 1 2 
 
 2 3 3 4 4 
 
 97 
 
 9868 
 
 9872 
 
 9877 
 
 9881 
 
 9886 
 
 9890 
 
 9894 
 
 9899 
 
 9903 
 
 9908 1 1 2 
 
 2 3 3 4 4 
 
 98 
 
 9912 
 
 9917 
 
 9921 
 
 9926 
 
 9930 
 
 9934 
 
 9939 
 
 9943 
 
 9948 
 
 9952 1 1 2 
 
 2 3 3 4 4 
 
 99 
 
 9956 
 
 9961 
 
 9965 
 
 9969 
 
 9974 
 
 9978 
 
 9983 
 
 9987 
 
 9991 
 
 9996 1 1 2 
 
 2 3 3 3 4 
 
26 
 
 AIR, WATER, AND FOOD 
 
 ANTILOGARITHMS 
 
 Loga- 
 rithms. 
 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 Proportional parts. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 2 
 
 
 3 
 I 
 
 4 
 
 1 
 
 5 
 
 1 
 
 6 
 
 1 
 
 7 
 2 
 
 8 
 
 2 
 
 9 
 
 O.OO 
 
 1000 
 
 1002 
 
 1005 
 
 1007 
 
 IOO9 
 
 IOI2 
 
 1014 
 
 1016 
 
 1019 
 
 I02I 
 
 
 
 2 
 
 O.OI 
 
 1023 
 
 1026 
 
 1028 
 
 IO30 
 
 I033 
 
 I035 
 
 1038 
 
 1040 
 
 1042 
 
 I045 
 
 
 
 
 
 I 
 
 I 
 
 1 
 
 1 
 
 2 
 
 2 
 
 2 
 
 0.02 
 
 1047 
 
 1050 
 
 1052 
 
 I054 
 
 IO57 
 
 I059 
 
 1062 
 
 1064 
 
 1067 
 
 1069 
 
 
 
 
 
 I 
 
 I 
 
 1 
 
 1 
 
 2 
 
 2 
 
 2 
 
 O.O3 
 
 1072 
 
 1074 
 
 1076 
 
 1079 
 
 1081 
 
 1084 
 
 1086 
 
 1089 
 
 1091 
 
 IO94 
 
 
 
 
 
 I 
 
 I 
 
 1 
 
 1 
 
 2 
 
 2 
 
 2 
 
 O.O4 
 
 1096 
 
 1099 
 
 1102 
 
 1 104 
 
 1107 
 
 I IO9 
 
 1112 
 
 1 1 14 
 
 1117 
 
 III9 
 
 
 
 I 
 
 I 
 
 I 
 
 1 
 
 2 
 
 2 
 
 2 
 
 2 
 
 O.05 
 
 1122 
 
 1125 
 
 1127 
 
 1130 
 
 1132 
 
 1135 
 
 1138 
 
 1 140 
 
 1 143 
 
 1 146 
 
 
 
 I 
 
 I 
 
 I 
 
 1 
 
 2 
 
 2 
 
 2 
 
 2 
 
 O.06 
 
 1 148 
 
 "Si 
 
 ii53 
 
 1156 
 
 1159 
 
 Il6l 
 
 1 164 
 
 1167 
 
 1 169 
 
 II72 
 
 
 
 I 
 
 I 
 
 1 
 
 1 
 
 2 
 
 2 
 
 2 
 
 2 
 
 O.07 
 
 "75 
 
 1178 
 
 1 180 
 
 1183 
 
 1186 
 
 H89 
 
 1191 
 
 1 194 
 
 1197 
 
 1 199 
 
 
 
 I 
 
 I 
 
 I 
 
 1 
 
 2 
 
 2 
 
 2 
 
 2 
 
 O.08 
 
 1202 
 
 1205 
 
 1208 
 
 I2II 
 
 1213 
 
 I2l6 
 
 1219 
 
 1222 
 
 1225 
 
 1227 
 
 
 
 I 
 
 I 
 
 1 
 
 1 
 
 2 
 
 2 
 
 2 
 
 3 
 
 O.O9 
 
 1230 
 
 1233 
 
 1236 
 
 1239 
 
 1242 
 
 1245 
 
 1247 
 
 1250 
 
 1253 
 
 I256 
 
 
 
 I 
 
 I 
 
 I 
 
 1 
 
 2 
 
 2 
 
 2 
 
 3 
 
 O.IO 
 
 1259 
 
 1262 
 
 1265 
 
 1268 
 
 1271 
 
 1274 
 
 1276 
 
 1279 
 
 1282 
 
 1285 
 
 
 
 I 
 
 I 
 
 I 
 
 1 
 
 2 
 
 2 
 
 2 
 
 3 
 
 O.II 
 
 1288 
 
 1291 
 
 1294 
 
 1297 
 
 1300 
 
 I303 
 
 1306 
 
 1309 
 
 1312 
 
 1315 
 
 
 
 I 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 2 
 
 3 
 
 O.I2 
 
 1318 
 
 1321 
 
 1324 
 
 1327 
 
 I330 
 
 1334 
 
 1337 
 
 I340 
 
 1343 
 
 1346 
 
 
 
 I 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 2 
 
 3 
 
 0.13 
 
 1349 
 
 1352 
 
 1355 
 
 1358 
 
 1361 
 
 1365 
 
 1368 
 
 1371 
 
 1374 
 
 1377 
 
 c 
 
 I 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 0.14 
 
 1380 
 
 1384 
 
 1387 
 
 I39O 
 
 1393 
 
 I396 
 
 1400 
 
 1403 
 
 1406 
 
 I409 
 
 c 
 
 I 
 
 1 
 
 I 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 015 
 
 1413 
 
 1416 
 
 1419 
 
 1422 
 
 1426 
 
 I429 
 
 1432 
 
 1435 
 
 1439 
 
 1442 
 
 c 
 
 I 
 
 I 
 
 1 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 0.16 
 
 1445 
 
 1449 
 
 1452 
 
 1455 
 
 1459 
 
 I462 
 
 1466 
 
 1469 
 
 1472 
 
 1476 
 
 
 
 I 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 0.17 
 
 1479 
 
 1483 
 
 i486 
 
 I489 
 
 1493 
 
 1496 
 
 1500 
 
 I503 
 
 1507 
 
 I5IO 
 
 
 
 I 
 
 I 
 
 1 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 0.18 
 
 1514 
 
 1517 
 
 1521 
 
 1524 
 
 1528 
 
 1531 
 
 1535 
 
 1538 
 
 1542 
 
 1545 
 
 
 
 I 
 
 I 
 
 1 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 0.19 
 
 1549 
 
 1552 
 
 1556 
 
 I560 
 
 1563 
 
 1567 
 
 I570 
 
 1574 
 
 1578 
 
 I58l 
 
 c 
 
 I 
 
 I 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 3 
 
 0.20 
 
 1585 
 
 1S89 
 
 1592 
 
 1596 
 
 1600 
 
 1603 
 
 1607 
 
 1611 
 
 1614 
 
 l6l8 
 
 
 
 I 
 
 I 
 
 1 
 
 2 
 
 2 
 
 3 
 
 3 
 
 3 
 
 0.21 
 
 1622 
 
 1626 
 
 1629 
 
 1633 
 
 1637 
 
 1641 
 
 1644 
 
 1648 
 
 1652 
 
 1656 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 3 
 
 0.22 
 
 1660 
 
 1663 
 
 1667 
 
 167I 
 
 1675 
 
 1679 
 
 1683 
 
 1687 
 
 1690 
 
 1694 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 3 
 
 0.23 
 
 1698 
 
 1702 
 
 1706 
 
 I7IO 
 
 1714 
 
 1718 
 
 1722 
 
 1726 
 
 1730 
 
 1734 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 0.24 
 
 1738 
 
 1742 
 
 1746 
 
 I750 
 
 1754 
 
 1758 
 
 1762 
 
 1766 
 
 1770 
 
 1774 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 0.25 
 
 1778 
 
 1782 
 
 1786 
 
 1791 
 
 1795 
 
 1799 
 
 1803 
 
 1807 
 
 1811 
 
 l8l6 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 0.26 
 
 1820 
 
 1824 
 
 1828 
 
 1832 
 
 1837 
 
 1841 
 
 1845 
 
 1849 
 
 1854 
 
 1858 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 3 
 
 4 
 
 0.27 
 
 1862 
 
 1866 
 
 1871 
 
 1875 
 
 1879 
 
 1884 
 
 1888 
 
 1892 
 
 1897 
 
 I9OI 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 3 
 
 4 
 
 0.28 
 
 1905 
 
 1910 
 
 1914 
 
 1919 
 
 1923 
 
 1928 
 
 1932 
 
 1936 
 
 1941 
 
 1945 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 0.29 
 
 i95o 
 
 1954 
 
 1959 
 
 I963 
 
 1968 
 
 1972 
 
 1977 
 
 1982 
 
 1986 
 
 1991 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 0.30 
 
 1995 
 
 2000 
 
 2004 
 
 2009 
 
 2014 
 
 20l8 
 
 2023 
 
 2028 
 
 2032 
 
 2037 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 0.31 
 
 2042 
 
 2046 
 
 2051 
 
 2056 
 
 2061 
 
 2065 
 
 2070 
 
 2075 
 
 2080 
 
 2084 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 0.32 
 
 2089 
 
 2094 
 
 2099 
 
 2I04 
 
 2109 
 
 2113 
 
 2118 
 
 2123 
 
 2128 
 
 2133 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 033 
 
 2138 
 
 2143 
 
 2148 
 
 2153 
 
 2158 
 
 2163 
 
 2168 
 
 2173 
 
 2178 
 
 2183 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 0.34 
 
 2188 
 
 2193 
 
 2198 
 
 2 203 
 
 2208 
 
 2213 
 
 2218 
 
 2223 
 
 2228 
 
 2234 
 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 5 
 
 0.35 
 
 2239 
 
 2244 
 
 2249 
 
 2254 
 
 2259 
 
 2265 
 
 2270 
 
 2275 
 
 2280 
 
 2286 
 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 5 
 
 0.36 
 
 2291 
 
 2296 
 
 2301 
 
 2307 
 
 2312 
 
 2317 
 
 2323 
 
 2328 
 
 2333 
 
 2339 
 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 5 
 
 0.37 
 
 2344 
 
 2350 
 
 2355 
 
 2360 
 
 2366 
 
 2371 
 
 2377 
 
 2382 
 
 2388 
 
 2393 
 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 5 
 
 0.38 
 
 2399 
 
 2404 
 
 2410 
 
 2415 
 
 2421 
 
 2427 
 
 2432 
 
 2438 
 
 2443 
 
 2449 
 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 5 
 
 0.39 
 
 2455 
 
 2460 
 
 2466 
 
 2472 
 
 2477 
 
 2483 
 
 2489 
 
 2495 
 
 2500 
 
 2506 
 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 5 
 
 5 
 
 0.40 
 
 2512 
 
 2518 
 
 2523 
 
 2529 
 
 2535 
 
 2541 
 
 2547 
 
 2553 
 
 2559 
 
 2564 
 
 
 I 
 
 2 
 
 2 
 
 3 
 
 4 
 
 4 
 
 5 
 
 5 
 
 0.41 
 
 2570 
 
 2576 
 
 2582 
 
 2588 
 
 2594 
 
 260O 
 
 2606 
 
 2612 
 
 2618 
 
 2624 
 
 
 I 
 
 2 
 
 2 
 
 3 
 
 4 
 
 4 
 
 5 
 
 5 
 
 0.42 
 
 2630 
 
 2636 
 
 2642 
 
 2649 
 
 2655 
 
 2661 
 
 2667 
 
 2673 
 
 2679 
 
 2685 
 
 
 I 
 
 2 
 
 2 
 
 3 
 
 4 
 
 4 
 
 5 
 
 6 
 
 0.43 
 
 2692 
 
 2698 
 
 2704 
 
 27IO 
 
 2716 
 
 2723 
 
 2729 
 
 2735 
 
 2742 
 
 2748 
 
 
 I 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 5 
 
 6 
 
 0.44 
 
 2754 
 
 2761 
 
 2767 
 
 2773 
 
 2780 
 
 2786 
 
 2793 
 
 2799 
 
 2805 
 
 28l2 
 
 
 I 
 
 2 
 
 3 
 
 3 
 
 4 
 
 4 
 
 5 
 
 6 
 
 o-45 
 
 2818 
 
 2825 
 
 2831 
 
 2838 
 
 2844 
 
 2851 
 
 2858 
 
 2864 
 
 2871 
 
 2877 
 
 
 I 
 
 2 
 
 3 
 
 3 
 
 4 
 
 S 
 
 5 
 
 6 
 
 0.46 
 
 2884 
 
 2891 
 
 2897 
 
 2904 
 
 2911 
 
 2917 
 
 2924 
 
 2931 
 
 2938 
 
 2944 
 
 
 I 
 
 2 
 
 3 
 
 3 
 
 4 
 
 5 
 
 5 
 
 6 
 
 0.47 
 
 2951 
 
 2958 
 
 2965 
 
 2972 
 
 2979 
 
 2985 
 
 2992 
 
 2999 
 
 3006 
 
 30I3 
 
 
 I 
 
 2 
 
 3 
 
 3 
 
 4 
 
 5 
 
 5 
 
 6 
 
 0.48 
 
 3020 
 
 3027 
 
 3034 
 
 304I 
 
 3048 
 
 3055 
 
 3062 
 
 3069 
 
 3076 
 
 3083 
 
 I 
 
 I 
 
 2 
 
 3 
 
 4 
 
 4 
 
 5 
 
 6 
 
 6 
 
 0.49 
 
 3090 
 
 3097 
 
 3io5 
 
 3112 
 
 3119 
 
 3126 
 
 3133 
 
 3141 
 
 3X48 
 
 3155 
 
 I 
 
 I 
 
 2 
 
 3 
 
 4 
 
 4 
 
 5 
 
 6 6 
 
APPENDIX A 
 ANTILOGARITHMS 
 
 227 
 
 Loga- 
 
 
 
 
 
 
 
 
 
 
 
 Proportional parts. 
 
 rithms. 
 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 2 
 1 1 
 
 3 
 
 2 
 
 4 
 3 
 
 5 
 
 4 
 
 6 
 4 
 
 7 
 
 5 
 
 8 
 
 6 
 
 9 
 
 O.50 
 
 3162 
 
 3170 
 
 3177 
 
 3184 
 
 3192 
 
 3199 
 
 3206 
 
 3214 
 
 3221 
 
 3228 
 
 7 
 
 0.5I 
 
 3236 
 
 3243 
 
 3251 
 
 3258 
 
 3266 
 
 3273 
 
 3281 
 
 3289 
 
 3296 
 
 3304 
 
 1 2 
 
 2 
 
 3 
 
 4 
 
 5 
 
 5 
 
 6 
 
 7 
 
 O.52 
 
 33H 
 
 3319 
 
 3327 
 
 3334 
 
 3342 
 
 335o 
 
 3357 
 
 3365 
 
 3373 
 
 338i 
 
 1 2 
 
 2 
 
 3 
 
 4 
 
 5 
 
 5 
 
 6 
 
 7 
 
 0.53 
 
 3338 
 
 3396 
 
 3404 
 
 3412 
 
 3420 
 
 3428 
 
 3436 
 
 3443 
 
 345i 
 
 3459 
 
 1 2 
 
 2 
 
 3 
 
 4 
 
 S 
 
 6 
 
 6 
 
 7 
 
 0.54 
 
 3467 
 
 3475 
 
 3483 
 
 349i 
 
 3499 
 
 35o8 
 
 35i6 
 
 3524 
 
 3532 
 
 3540 
 
 1 2 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 6 
 
 7 
 
 o-55 
 
 3548 
 
 3556 
 
 3565 
 
 3573 
 
 358i 
 
 3589 
 
 3597 
 
 3606 
 
 3614 
 
 3622 
 
 1 2 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 7 
 
 0.56 
 
 3631 
 
 3639 
 
 3648 
 
 3656 
 
 3664 
 
 3673 
 
 3681 
 
 3690 
 
 3698 
 
 3707 
 
 1 2 
 
 3 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 o.57 
 
 3715 
 
 3724 
 
 3733 
 
 374i 
 
 375o 
 
 3758 
 
 3767 
 
 3776 
 
 3784 
 
 3793 
 
 1 2 
 
 3 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 0.58 
 
 3802 
 
 3811 
 
 3819 
 
 3828 
 
 3837 
 
 3846 
 
 3855 
 
 3864 
 
 3873 
 
 3882 
 
 1 2 
 
 3 
 
 4 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 o.59 
 
 3890 
 
 3899 
 
 3908 
 
 39*7 
 
 3926 
 
 3936 
 
 3945 
 
 3954 
 
 39 6 3 
 
 3972 
 
 1 2 
 
 3 
 
 4 
 
 5 
 
 5 
 
 6 
 
 7 
 
 8 
 
 0.60 
 
 398i 
 
 399o 
 
 3999 
 
 4009 
 
 4018 
 
 4027 
 
 4036 
 
 4046 
 
 4055 
 
 4064 
 
 1 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 6 
 
 7 
 
 8 
 
 0.61 
 
 4074 
 
 4083 
 
 4093 
 
 4102 
 
 4111 
 
 4121 
 
 4130 
 
 4140 
 
 4150 
 
 4159 
 
 1 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 0.62 
 
 4169 
 
 4178 
 
 4188 
 
 4198 
 
 4207 
 
 4217 
 
 4227 
 
 4236 
 
 4246 
 
 4256 
 
 1 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 0.63 
 
 4266 
 
 4276 
 
 4285 
 
 4295 
 
 4305 
 
 4315 
 
 4325 
 
 4335 
 
 4345 
 
 4355 
 
 1 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 0.64 
 
 4365 
 
 4375 
 
 4385 
 
 4395 
 
 4406 
 
 4416 
 
 4426 
 
 4436 
 
 4446 
 
 4457 
 
 1 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 0.65 
 
 4467 
 
 4477 
 
 4487 
 
 4498 
 
 4508 
 
 4519 
 
 4529 
 
 4539 
 
 455o 
 
 4560 
 
 1 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 0.66 
 
 457i 
 
 458i 
 
 4592 
 
 4603 
 
 4613 
 
 4624 
 
 4634 
 
 4645 
 
 4656 
 
 4667 
 
 1 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 9 
 
 10 
 
 0.67 
 
 4677 
 
 4688 
 
 4699 
 
 4710 
 
 4721 
 
 4732 
 
 4742 
 
 4753 
 
 4764 
 
 4775 
 
 1 2 
 
 3 
 
 4 
 
 5 
 
 7 
 
 8 
 
 9 
 
 10 
 
 0.68 
 
 4786 
 
 4797 
 
 4808 
 
 4819 
 
 4831 
 
 4842 
 
 4853 
 
 4864 
 
 4875 
 
 4887 
 
 1 2 
 
 3 
 
 4 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 0.69 
 
 4898 
 
 4909 
 
 4920 
 
 4932 
 
 4943 
 
 4955 
 
 4966 
 
 4977 
 
 4989 
 
 5000 
 
 1 2 
 
 3 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 0.70 
 
 5012 
 
 5023 
 
 5035 
 
 5047 
 
 5058 
 
 5070 
 
 5082 
 
 5093 
 
 5105 
 
 5ii7 
 
 1 2 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 II 
 
 0.71 
 
 5129 
 
 5140 
 
 5152 
 
 5164 
 
 5176 
 
 5188 
 
 5200 
 
 5212 
 
 5224 
 
 5236 
 
 1 2 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 10 
 
 II 
 
 0.72 
 
 5248 
 
 5260 
 
 5272 
 
 5284 
 
 5297 
 
 5309 
 
 532i 
 
 5333 
 
 5346 
 
 5358 
 
 1 2 
 
 4 
 
 5 
 
 6 
 
 7 
 
 9 
 
 10 
 
 11 
 
 o.73 
 
 5370 
 
 5383 
 
 5395 
 
 5408 
 
 5420 
 
 5433 
 
 5445 
 
 5458 
 
 547o 
 
 5483 
 
 1 3 
 
 4 
 
 5 
 
 6 
 
 8 
 
 9 
 
 10 
 
 11 
 
 0.74 
 
 5495 
 
 55o8 
 
 552i 
 
 5534 
 
 5546 
 
 5559 
 
 5572 
 
 5585 
 
 5598 
 
 5610 
 
 1 3 
 
 4 
 
 5 
 
 6 
 
 8 
 
 9 
 
 10 
 
 12 
 
 o.75 
 
 5623 
 
 5636 
 
 5649 
 
 5662 
 
 5675 
 
 5689 
 
 5702 
 
 5715 
 
 5728 
 
 574i 
 
 I 3 
 
 4 
 
 5 
 
 7 
 
 8 
 
 9 
 
 10 
 
 12 
 
 0.76 
 
 5754 
 
 5768 
 
 578i 
 
 5794 
 
 5808 
 
 5821 
 
 5834 
 
 5848 
 
 5861 
 
 5875 
 
 I 3 
 
 4 
 
 5 
 
 7 
 
 8 
 
 9 
 
 11 
 
 12 
 
 0.77 
 
 5888 
 
 5902 5916 
 
 5929 
 
 5943 
 
 5957 
 
 597o 
 
 5984 
 
 5998 
 
 6012 
 
 1 3 
 
 4 
 
 5 
 
 7 
 
 8 
 
 10 
 
 11 
 
 12 
 
 0.78 
 
 6026 
 
 6039 
 
 6053 
 
 6067 
 
 6081 
 
 6095 
 
 6109 
 
 6124 
 
 6138 
 
 6152 
 
 I 3 
 
 4 
 
 6 
 
 7 
 
 8 
 
 IC 
 
 11 
 
 13 
 
 0.79 
 
 6166 
 
 6180 
 
 6194 
 
 6209 
 
 6223 
 
 6237 
 
 6252 
 
 6266 
 
 6281 
 
 6295 
 
 I 3 
 
 4 
 
 6 
 
 7 
 
 9 
 
 10 
 
 11 
 
 13 
 
 0.80 
 
 6310 
 
 6324 
 
 6339 
 
 6353 
 
 6368 
 
 6383 
 
 6397 
 
 6412 
 
 6427 
 
 6442 
 
 I 3 
 
 4 
 
 6 
 
 7 
 
 9 
 
 10 
 
 12 
 
 13 
 
 0.81 
 
 6457 
 
 6471 
 
 6486 
 
 6501 
 
 6516 
 
 6531 
 
 6546 
 
 6561 
 
 6577 
 
 6592 
 
 2 3 
 
 5 
 
 6 
 
 8 
 
 9 
 
 11 
 
 12 
 
 14 
 
 0.82 
 
 6607 
 
 6622 
 
 6637 
 
 6653 
 
 6668 
 
 6683 
 
 6699 
 
 6714 
 
 6730 
 
 6745 
 
 2 3 
 
 5 
 
 6 
 
 8 
 
 9 
 
 11 
 
 12 
 
 14 
 
 0.83 
 
 6761 
 
 6776 
 
 6792 
 
 6808 
 
 6823 
 
 6839 
 
 6855 
 
 6871 
 
 6887 
 
 6902 
 
 2 3 
 
 5 
 
 6 
 
 8 
 
 9 
 
 11 
 
 13 
 
 14 
 
 0.84 
 
 6918 
 
 6934 
 
 6950 
 
 6966 
 
 6982 
 
 6998 
 
 7015 
 
 7031 
 
 7047 
 
 7063 
 
 2 3 
 
 5 
 
 
 
 8 
 
 10 
 
 11 
 
 13 
 
 IS 
 
 0.85 
 
 7079 
 
 7096 
 
 7112 
 
 7129 
 
 7145 
 
 7161 
 
 7178 
 
 7194 
 
 7211 
 
 7228 
 
 2 3 
 
 5 
 
 7 
 
 8 
 
 10 
 
 12 
 
 13 
 
 15 
 
 0.86 
 
 7244 
 
 7261 
 
 7278 
 
 7295 
 
 73" 
 
 7328 
 
 7345 
 
 7362 
 
 7379 
 
 7396 
 
 2 3 
 
 5 
 
 7 
 
 8 
 
 10 
 
 12 
 
 13 
 
 15 
 
 0.87 
 
 7413 
 
 743° 
 
 7447 
 
 7464 
 
 7482 
 
 7499 
 
 75i6 
 
 7534 
 
 755i 
 
 7568 
 
 2 3 
 
 5 
 
 7 
 
 9 
 
 10 
 
 12 
 
 14 
 
 16 
 
 0.88 
 
 7586 
 
 7603 
 
 7621 
 
 7638 
 
 7656 
 
 7674 
 
 7691 
 
 7709 
 
 7727 
 
 7745 
 
 2 4 
 
 5 
 
 7 
 
 9 
 
 11 
 
 12 
 
 14 
 
 16 
 
 0.89 
 
 7762 
 
 7780 
 
 7798 
 
 7816 
 
 7834 
 
 7852 
 
 7870 
 
 7889 
 
 7907 
 
 7925 
 
 2 4 
 
 5 
 
 7 
 
 9 
 
 11 
 
 13 
 
 14 
 
 16 
 
 0.90 
 
 7943 
 
 7962 
 
 798o 
 
 7998 8017 
 
 8035 
 
 8054 
 
 8072 
 
 8091 
 
 8110 
 
 2 4 
 
 « 
 
 7 
 
 9 
 
 11 
 
 13 
 
 15 
 
 17 
 
 0.91 
 
 8128 
 
 8147 
 
 8166 
 
 81858204 
 
 8222 
 
 8241 
 
 8260 
 
 8279 
 
 8299 
 
 2 4 
 
 6 
 
 8 
 
 9 
 
 11 
 
 13 
 
 15 
 
 17 
 
 0.92 
 
 8318 
 
 8337 
 
 8356 
 
 8375^395 
 
 8414 
 
 8433 
 
 8453 
 
 8472 
 
 8492 
 
 2 4 
 
 6 
 
 8 
 
 10 
 
 12 
 
 14 
 
 15 
 
 17 
 
 °-93 
 
 8511 
 
 8531 
 
 855i 
 
 85708590 
 
 8610 
 
 8630 
 
 8650 
 
 8670 
 
 8690 
 
 2 4 
 
 6 
 
 8 
 
 10 
 
 12 
 
 14 
 
 16 
 
 18 
 
 0.94 
 
 8710 
 
 8730 
 
 8750 
 
 8770:8790 
 
 8810 
 
 8831 
 
 8851 
 
 8872 
 
 8892 
 
 2 4 
 
 6 
 
 8 
 
 10 
 
 12 
 
 14 
 
 16 
 
 18 
 
 °-95 
 
 8913 
 
 8933 
 
 8954 
 
 89748995 
 
 9016 
 
 9036 
 
 9057 
 
 9078 
 
 9099 
 
 2 4 
 
 ^ 
 
 8 
 
 10 
 
 12 
 
 15 
 
 17 
 
 19 
 
 0.96 
 
 9120 
 
 9141 
 
 9162 
 
 9183 9204 
 
 9226 
 
 9247 
 
 9268 
 
 92909311 
 
 2 4 
 
 6 
 
 8 
 
 11 
 
 13 
 
 15 
 
 17 
 
 19 
 
 0.97 
 
 9333 
 
 9354 
 
 9376 
 
 93979419 
 
 9441 
 
 9462 
 
 9484 
 
 9506 9528 
 
 2 4 
 
 7 
 
 9 
 
 11 
 
 13 
 
 15 
 
 17 
 
 20 
 
 0.98 
 
 9550 9572 
 
 9594 
 
 9616 9638 
 
 9661 
 
 9683 
 
 9705 
 
 9727 
 
 975o 
 
 2 4 
 
 7 
 
 9 
 
 11 
 
 13 
 
 16 
 
 18 
 
 20 
 
 0.99 
 
 97729795 
 
 9817 
 
 9840 9863 
 
 9886 9908 
 
 9931 
 
 9954 
 
 9977 
 
 2 5 
 
 7 
 
 9 
 
 11 
 
 14 
 
 16 
 
 18 
 
 20 
 
APPENDIX B 
 
 REAGENTS 
 
 Air Analysis 
 
 Pettenkofer Method. — Barium Hydroxide. — A solution con- 
 taining about 4 grams of BaO and 0.2 gram of BaCl 2 to the liter. 
 (1 c.c. = 1 mg. C0 2 , approximately.): 
 
 Sulphuric Acid. — Dilute 45.45 c.c. of normal sulphuric acid 
 to one liter. (1 c.c. = 1 mg. CO2.) To standardize the solu- 
 tion measure 25 c.c. into a weighed platinum dish, add dilute 
 ammonia-water in slight excess, evaporate to dryness on the 
 water-bath, and dry at 120 C. to constant weight. 
 
 Standard Lime-water. — (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. To a liter of 
 distilled water add 2.5 c.c. of a solution of 0.7 gram of phenol- 
 phthalein in 100 c.c. of 50 per cent alcohol and add lime-water 
 drop by drop until a slight permanent pink color is produced. 
 Then add 6.3 c.c. of the above calcium hydroxide solution. The 
 resulting solution is the standard lime-water used for the tests. 
 
 Water Analysis 
 
 For Ammonia. — Water Free from Ammonia. — The ammonia- 
 free water used in this laboratory is made by redistilling distilled 
 water from a solution of alkaline permanganate in a steam-heated 
 copper still. 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 HgCl 2 which has been 
 saturated by boiling with an excess of the salt and allowing it 
 
 228 
 
APPEXDIX 229 
 
 to crystallize out. Add the HgCl 2 cautiously until a slight per- 
 manent red precipitate (HgL) appears. Dissolve this 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 
 a liter and allow it to stand over night 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 
 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 specific gravity of 1.125, a dd 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 3.82 grams chemi- 
 cally pure XH4CI in a liter of water free from ammonia. This 
 is the strong solution from which the standard solution is 
 made by diluting 10 c.c. to a liter with water free from am- 
 monia. One cubic centimeter of the standard solution = 
 0.00001 gram nitrogen. This solution, like the nitrite standard 
 and other dilute solutions, must be preserved in sterilized bot- 
 tles protected from dust and organic matter. 
 
 For Nitrites. — Standard Nitrite Solution. — The pure silver 
 nitrite used in making this solution is prepared by the double 
 decomposition of silver nitrate and potassium nitrite, and re- 
 peated crystallizations from water of the rather difficultly solu- 
 ble silver nitrite. 1.1 grams of this silver nitrite are dissolved 
 in nitrite-free water, the silver completely precipitated by the 
 addition of the standard salt solution used in the determination 
 of chlorine, and the solution made up to 1 liter. 100 c.c. of this 
 strong solution are diluted to 1 liter, and 10 c.c. of this last 
 solution again diluted to 1 liter. The final solution is the one 
 used in preparing standards. 1 c.c. = 0.0000001 gram nitrogen. 
 
 Sulphanilic Acid. — Dissolve 3.3 grams sulphanilic acid in 
 
23O APPENDIX 
 
 750 c.c. of water by the aid of heat, and add 250 c.c. glacial 
 acetic acid. 
 
 N aphthylamine Acetate. — Boil 0.5 gram of a-naphthylamine 
 in 100 c.c. of water in a small Erlenmeyer flask for about five 
 minutes, filter through a plug of washed absorbent cotton, add 
 250 c.c. glacial acetic acid, and dilute to 1 liter. 
 
 For Nitrates. — Standard Nitrate Solution. — Dissolve 0.720 
 gram of pure recrystallized KN0 3 in 1 liter of water. Evapo- 
 rate 10 c.c. of this strong solution cautiously on the water-bath, 
 moisten quickly and thoroughly with 2 c.c. of phenol-disul- 
 phonic acid, and dilute to 1 liter for the standard solution. 
 1 c.c. = 0.000001 gram nitrogen. 
 
 Phenol-disulphonic Acid. — Heat together 3 grams synthetic 
 phenol with 37 grams pure, concentrated H 2 S0 4 in a boiling 
 water-bath for six hours. 
 
 Potassium Hydroxide. — 30 per cent. 
 
 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 2.25 liters of water and boil down to something 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 
 solution dilute 100 c.c. of this strong solution to 1 liter. 1 c.c. = 
 0.001 gram chlorine. 
 
 Silver Nitrate. — Dissolve about 2.42 grams of AgN0 3 (dry 
 crystals) in 1 liter of chlorine-free water. 1 c.c. = 0.0005 gram 
 CI, approximately. Standardize against the NaCl solution. 
 
 Potassium Chromate. — Dissolve 50 grams neutral K 2 Cr0 4 in 
 a little distilled water. Add enough AgN0 3 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- 
 
APPENDIX 231 
 
 cipitate the A1(0H) 3 by the cautious addition of NH 4 OH. 
 Wash the precipitate in a large jar by decantation until free from 
 chlorine, nitrites, and ammonia. 
 
 For Hardness. — Standard Calcium Chloride Solution. — Dis- 
 solve 0.200 gram of pure Iceland spar in dilute HC1, taking 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 1 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 to 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 CaCl 2 solution. 
 
 Erythrosine Indicator. — Dissolve 0.1 gram of erythrosine in 
 1 liter of water. 
 
 Methyl Orange Indicator. — Dissolve 0.1 gram Aniline Orange, 
 Merck, (Methyl) or Orange III in a few cubic centimeters of 
 alcohol and dilute to 100 c.c. with distilled water. 
 
 Soda Reagent. — Equal parts of sodium hydroxide and sodium 
 
 N 
 carbonate solutions, the mixture to be approximately — 
 
 10 
 
 For Iron. — Standard Solution. — Dissolve 0.7 gram of crys- 
 tallized ferrous ammonium sulphate in 50 c.c. of distilled water 
 and add 20 c.c. of dilute sulphuric acid. Warm the solution 
 slightly and add potassium permanganate until the iron is com- 
 pletely oxidized. Dilute the solution to one liter. One cubic 
 centimeter of the standard solution equals 0.1 mg. Fe. 
 
 Potassium Sulphocyanate. — 20 grams per liter. 
 
 Hydrochloric Acid. — One part HC1 (sp. gr. 1.20) to 1 part of 
 water. 
 
 Potassium Permanganate. — Five grams KMn0 4 in 1 liter of 
 water. 
 
 For Dissolved Oxygen. — Manganous Sulphate. — 48 grams 
 of MnS0 4 . 4 H 2 in 100 c.c. of water. 
 
 Alkaline Potassium Iodide. — 360 grams of NaOH and 100 
 grams of KI in 1 liter of water. 
 
232 APPENDIX 
 
 Hydrochloric Acid. — Sp. gr. 1.20. 
 
 Potassium Acetate. — 100 grams in 100 c.c. of water. 
 
 N 
 
 Sodium Thiosulphate Solution. • Dissolve 2.48 grams of 
 
 100 
 
 the pure crystallized salt in water and dilute to one liter. Stand- 
 
 N 
 ardize against a — potassium bichromate solution. 
 100 
 
 For Oxygen Consumed. — Standard Ammonium Oxalate Solu- 
 tion. — Dissolve 0.888 gram pure ammonium oxalate in 1 liter 
 of distilled water. One cubic centimeter is equivalent to 0.0001 
 gram oxygen consumed. 
 
 Potassium Permanganate Solution. — Dissolve 0.4 gram potas- 
 sium permanganate in 1 liter of distilled water and standardize 
 against the ammonium oxalate solution according to the method 
 described in the text. 
 
 N 
 For Free Carbonic Acid. — Standard — Sodium Carbonate 
 
 22 
 
 Solution. 
 
 For Lead. — Standard Lead Solution. — To a strong solution 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 the lead in an aliquot 
 part by precipitating with K 2 Cr 2 07 and weighing the lead chro- 
 mate. Dilute an aliquot part to make a convenient standard, 
 say about 1 c.c. = 0.001 gram of Pb. 
 
 Food Analysis 
 
 Pumice. — Bits of ignited pumice, about the size of a pea, 
 dropped while hot into water and bottled for use. 
 
 Alcohol (for Reichert-Meissl method). — 95 per cent alcohol 
 redistilled from potassium hydroxide. 
 
 Iodine Solution (for Hanus' method) . — This is conveniently 
 made up according to the directions of Hunt.* Dissolve 13.2 
 grams iodine in 1 liter of glacial acetic acid (99 per cent, show- 
 
 * /. Soc. Chem. Ind., 21, IQ02, 454. 
 
APPENDIX 233 
 
 ing no reduction with bichromate and sulphuric acid). This will 
 best be done by adding the acetic acid in portions and heating 
 on the water-bath with frequent shaking. To the cold solution 
 add enough bromine to double the halogen content, as shown 
 by titration. Three cubic centimeters of bromine is sufficient. 
 A slight excess of iodine is not detrimental. 
 
 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 evolution of hydrogen 
 gas. The ether thus prepared should be kept over metallic 
 sodium and a tube of calcium chloride should be inserted in the 
 stopper, in order to allow the escape of any accumulated gas. 
 
 Potassium Sulphide. — Dissolve 40 grams of the crystallized 
 salt in 1 liter of water and filter through glass wool. 
 
 Potassium Hydroxide (for Kjeldahl process). — Dissolve 700 
 grams of the best quality of stick potash in water and dilute to 
 1 liter. 
 
 Basic Lead Acetate. — Boil for half an hour 440 grams of 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 
 liquid. (Specific gravity about 1.27, containing about 35 per 
 cent of the basic salt.) 
 
 Ferric Alum. — Dissolve 2 grams of ferric alum in 100 c.c. of 
 water, boil the solution until a precipitate appears, and filter. 
 
 Fehling , s Solution. — (a) Dissolve 69.28 grams of C.P. crys- 
 tallized copper sulphate, carefully dried between blotting-paper, 
 in water and make up to 1 liter, including 1 c.c. of strong sul- 
 phuric acid: (b) Dissolve 346 grams of sodium potassium tar- 
 trate and 100 grams of sodium hydroxide in water and make 
 up to a liter. 
 
 
BIBLIOGRAPHY 
 
 AIR 
 
 The following list contains the more important books and 
 articles of recent publication. 
 
 Barker, A. H. The Theory and Practice of Heating and Ventilation. The 
 Carton Press, London, 191 2.. 
 
 Greene, A. M. The Elements of Heating and Ventilation. John Wiley & Sons, 
 New York, 1913. 
 
 Hammarsten-Mandel. A Text Book of Physiological Chemistry. John 
 Wiley & Sons, New York, 1908. 
 
 Hoffman, J. D. Handbook for Heating and Ventilating Engineers. McGraw- 
 Hill Book Co., New York, 19 13. 
 
 Macfie, Ronald C. Air and Health. Methuen & Co., London, 1909. 
 
 Richards, Ellen H. Conservation by Sanitation. John Wiley & Sons, New 
 York, 191 1. 
 
 Rosenau, M. J. Preventive Medicine and Hygiene. Appleton, New York, 
 
 1913. 
 
 Shaw, W. W. Air Currents and the Laws of Ventilation. University Press, 
 Cambridge, Eng., 1907. 
 
 Soper, J. A. Air and Ventilation in Subways. John Wiley & Sons, New 
 York, 1908. 
 
 Talbot, Marion. House Sanitation. Whitcomb & Barrows, Boston, 1913. 
 
 Standard Methods for the Examination of Air. American Public Health Asso- 
 ciation, Boston, 1910. 
 
 Affleck. Ventilation of Gymnasia. Am. Phys. Ed. Rev., 1912. 
 
 Air Supply and Ventilation Number. Am. J. Pub. Health, Nov., 1913, 3, 
 pp. 1123-1210. 
 
 Crowder. A Study of the Ventilation of Sleeping Cars. Arch. Intern. Med., 
 1911, 7, pp. 85-133. 
 
 Jordan and Carlson. Ozone: Its Bactericidal, Physiologic and Deodorizing 
 Action. J. Am. Med. Assn., 1913, 61, p. 1007. 
 
 McCurdy. Recirculated Air. Am. Phys. Ed. Rev., 1913, Dec. 
 
 Norton. Ventilation of Sleeping Cars. Science Conspectus, 191 2, 2, pp. 
 79-82. 
 
 Transactions of the 15th International Congress of Hygiene and Demography. 
 1913, Vol. 2, Pt. II. 
 
 Ventilation Symposium. J. Ind. Eng. Chem., 1914, 6, p. 245. 
 
 Vosmaer. Industrial Uses of Ozone. J. Ind. Eng. Chem., 1914, 6, p. 229. 
 
 Winslow & Kligler. A Quantitative Study of Bacteria in City Dust. Am. 
 J. Pub. Health, 191 2, 2, p. 663. 
 
 234 
 
BIBLIOGRAPHY 235 
 
 WATER 
 
 The following list contains the most important recent books 
 on water, from a sanitary standpoint. 
 
 Don, J. & Chlsholm, J. Modem Methods of Water Purification. 2nd Ed., 
 Longmans, Green & Co., New York, 1913. 
 
 Fuller, M. L. Domestic Water Supplies for the Farm. John Wiley & Sons, 
 New York, 191 2. 
 
 Gerhard, W. P. The Sanitation, Water Supply and Sewage Disposal of 
 Country Houses. D. Van Nostrand Co., New York, 1909. 
 
 Hazen, Allen. The Filtration of Public Water Supplies. . 3rd Ed., John 
 Wiley & Sons, New York, 19 10. 
 
 Hazen, Allen. Clean Water and How to Get It. 2nd Ed., John Wiley & 
 Sons, New York, 19 14. 
 
 Mason, W. P. Examination of Water. 4th Ed., John Wiley & Sons, New- 
 York, 191 2. 
 
 Mason, W. P. Water Supply. John Wiley & Sons, New York, 1909. 
 
 Prescott, S. C. and Winslow, C. E. A. Elements of Water Bacteriology. 
 3rd Ed., John Wiley & Sons, New York, 1913. 
 
 Rideal, S. Water and Its Purification. Lockwood & Son, London, 1902. 
 
 Stocks, H. B. Water Analysis. Griffin & Co., London, 191 2. 
 
 Thresh, J. C. The Examination of Waters and Water Supplies. 2nd Ed., P. 
 Blackiston's Son & Co., Philadelphia, 1913. 
 
 Thresh, J. C. A Simple Method of Water Analysis. 7th Ed., Churchill, 
 London, 191 2. 
 
 Tillsman, J. Translation by H. S. Taylor. Water Purification and Sewage 
 Disposal. D. Van Nostrand Co., New York, 1913. 
 
 Whipple, G. C. The Microscopy of Drinking Water. 3rd Ed., John Wiley 
 & Sons, New York, 19 14. 
 
 Whipple, G. C. The Value of Pure Water. John Wiley & Sons, New York, 
 1907. 
 
 Annual Reports, Massachusetts State Board of Health, 1879 to 1912. 
 
 Reports of the Metropolitan Water Board, New York City. 
 
 Reports of the Royal Commission on Sewage Disposal, England. 
 
 FOOD 
 
 Only the general books and bulletins published since 1890 
 which are most available to the student are given here. A de- 
 tailed list of all important references to food will be found at 
 the end of each chapter in Leach's Food Inspection and Analysis. 
 
 Allen, A. H. Commercial Organic Analysis. 4th Ed., Blakiston, Phila., 
 1911. 
 
 Bailey, E. H. S. Sanitary and Applied Chemistry. Macmillan, New York, 
 1906. 
 
236 BIBLIOGRAPHY 
 
 Blyth, A. W. and M. W. Foods, their Composition and Analysis. Griffin, 
 London, 1909. 
 
 Farrington, E. H., and Woll, F. W. Testing Milk and Its Products. Men- 
 dota Book Co., Madison, Wis., 1908. 
 
 Girard, C. and Dupre, A. Analyse des Matieres Alimentaires. 2d Ed., 
 Dunod, Paris, 1904. 
 
 Hutchison, R. Food and Dietetics. William Wood, New York, 1908. 
 
 Konig, J. Die Menschlichen Nahrungs = u. Genussmittel. Springer, Berlin, 
 1904. 
 
 . Die Untersuchung landwirtschaftlich und gewerblich wichtiger Stoffe. 
 
 Parey, Berlin, 191 1. 
 
 Leach, A. E. Food Inspection and Analysis. Wiley, New York, 1909. 
 
 Leffmann, H. and Beam, W. Food Analysis. Blakiston, Phila., 1905. 
 
 Lewkowitsch, J. Oils, Fats and Waxes. Macmillan, New York, 1909. 
 
 Mitchell, C. A. Flesh Foods. Griffin, London, 1900. 
 
 Moor, C. G. Standards for Food and Drugs. Bailliere, Tindall & Cox, London, 
 1902. 
 
 Norton, A. P. Food and Dietetics. School of Home Economics, Chicago, 
 1907. 
 
 Olsen, J. C. Pure Food. Ginn & Co., Boston, 191 1. 
 
 Pearmain, T. H., and Moor, C. G. The Analysis of Food and Drugs. Bailliere, 
 Tindall & Cox, London, 1897. 
 
 Richards, E. H. The Cost of Food. Wiley, New York, 1901. 
 
 . Food Materials and their Adulterations. Home Science Pub. Co., 
 
 Boston, 1908. 
 
 Richmond, H. D. Dairy Chemistry. London, 1889. 
 
 Rupp, G. Die Untersuchung von Nahrungsmitteln. Winter, Heidelberg, 1900. 
 
 Sherman, H. C. Chemistry of Food and Nutrition. Macmillan, New York, 
 1911. 
 
 . Organic Analysis. Macmillan, New York, 191 2. 
 
 Snyder, H. Human Foods. Macmillan, New York, 1908. 
 
 Van Slyke, L. L. Testing Milk and Milk Products. Orange Judd, New York, 
 1911. 
 
 Wiley, H. W. Principles and Practice of Agricultural Analysis. Vol. III. 
 Chem. Pub. Co., Easton, Pa., 1897. 
 
 . Foods and their Adulteration. Blakiston, Phila., 1911. 
 
 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. 
 
 11. Analyses of American Feeding Stuffs. 1892. 
 
 21. Chemistry and Economy of Food. 1895. 
 
 25. Dairy Bacteriology. 1895. 
 
INDEX 245 
 
 Page 
 
 Malted cereals, analysis of 189 
 
 Manganese sulphate solution 231 
 
 Marsh test for caramel 204 
 
 Methyl orange indicator 231 
 
 Milk, composition of 136 
 
 detection of added water 158 
 
 interpretation of analysis 156 
 
 serum, examination of ! 149 
 
 solids, calculation of 148 
 
 sugar, determination of 145 
 
 variations in compositions of 137 
 
 Mills-Reincke phenomenon 45 
 
 Mineral matter in water 65 
 
 determination of 87 
 
 salts, value in food 116 
 
 Misbranding 125 
 
 Moisture in cereals 180 
 
 see Humidity. 
 
 Motion of air, determination of 22 
 
 effect on heat loss 14 
 
 Naphthylamine acetate solution 80, 230 
 
 Nessler reagent , 72, 228 
 
 Nitrate solution, standard 230 
 
 Nitrates in water, determination of 82 
 
 significance of 63 
 
 Nitrite solution, standard 229 
 
 Nitrites in air, determination of 42 
 
 in water, determination of 80 
 
 significance of 63 
 
 Nitrogen cycle 60 
 
 in water, determination of total 78 
 
 Nitrogen-free extract 184 
 
 Nitrogenous substances, function of 113 
 
 Nutritive ratio 117 
 
 Odor in water, determination of 106 
 
 Odors in water, extermination of 48 
 
 Oleomargarine 163 
 
 Organic matter in water 66 
 
 determination of 85 
 
 Oxygen consumed, determination of 85 
 
 dissolved in water, determination of 100 
 
 significance of 66 
 
 in expired air , n 
 
 in inspired air 9 
 
 table of saturation of water with 103 
 
246 INDEX 
 
 Page 
 
 Ozone, use in purifying air 20 
 
 sterilizing water 54 
 
 Pettenkofer method for carbon dioxide 33 
 
 Pettersen-Palmquist apparatus 27 
 
 Phenoldisulphonic acid reagent 82, 230 
 
 Pollution in wells, methods of tracing 50 
 
 past 63 
 
 Potassium acetate solution 232 
 
 chromate indicator 230 
 
 iodide solution, alkaline 231 
 
 permanganate, alkaline 73, 229 
 
 permanganate solution, standard 232 
 
 sulphocyanate reagent 89, 231 
 
 Preservatives, detection in butter 166 
 
 Preservatives in food 132 
 
 Protein by Kjeldahl method 182 
 
 Proteins in milk 146 
 
 Psychrometer 22 
 
 Putrescibility test 104 
 
 Radiator, platinum 88 
 
 Rain fall, average 46 
 
 water 45 
 
 Rapid methods for air analysis 35 
 
 Reagents for air analysis 228 
 
 water analysis 228 
 
 Reducing sugar, Munson and Walker's table 221 
 
 Refractive index 173 
 
 Refractometer 174 
 
 principle of 175 
 
 Reichert-Meissl number 167 
 
 Renovated butter, manufacture of 163 
 
 Residue on evaporation, determination of 87 
 
 Resins, in vanilla 203 
 
 Respiration n 
 
 Salicylic acid, detection of 196 
 
 Salt, determination in butter 166 
 
 Sanitary science, importance of 2 
 
 Sanitation, scope of chemistry of 1 
 
 Sediment, determination of 108 
 
 Self-purification of streams 47 
 
 Septic tank 61 
 
 Sewage analysis 67, 109 
 
 purification required 44 
 
 tables of analyses of 213 
 
BIBLIOGRAPHY 237 
 
 28. (Rev. Ed.) Chemical Composition of American Food Materials. 1895. 
 
 29. Dietary Studies at the University of Tennessee. 1896. 
 
 31. Dietary Studies at the University of Missouri. 1896. 
 
 32. Dietary Studies at Purdue University. 1896. 
 
 34. Carbohydrates of Wheat, Maize, Flour, and Bread. 1896. 
 
 35. Food and Nutrition Investigations in New Jersey. 1896. 
 
 37. Dietary Studies at the Maine State College. 1897. 
 
 38. Dietary Studies — Food of the Negro in Alabama. 1897. 
 40. Dietary Studies 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. Nutrition Investigations at the University of Tennessee. 1898. 
 
 54. Nutrition Investigations in New Mexico. 1898. 
 
 55. Dietary Studies in Chicago. 1898. 
 
 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. Dietary Studies of University Boat Crews. 1900. 
 
 84. Nutrition Investigations at the California Agr. Expt. Station. 1900. 
 
 85. Investigations on the Digestibility and Nutritive Value of Bread. 1900. 
 89. Effect of Muscular Work on Digestion of Food and Metabolism of 
 
 Nitrogen. 1901. 
 91. Nutrition Investigations at the University of Illinois, etc. 1901. 
 98. Effect of Severe and Prolonged Muscular Work on Food Consumption 
 
 Digestibility, and Metabolism. 1901. 
 
 101. Studies on Bread and Bread Making. 1901. 
 
 102. Losses in Cooking Meat. 1901. 
 
 107. Nutrition Investigations among Fruitarians and Chinese. 1901. 
 
 109. Metabolism of Matter and Energy in the Human Body. 1902. 
 
 116. Dietary Studies in New York City. 1902. 
 
 117. Effect of Muscular Work upon Digestibility of Food and Metabolism 
 
 of Nitrogen. 1902. 
 121. Metabolism of Nitrogen, Sulphur, and Phosphorus in the Human 
 
 Organism. 1902. 
 126. Digestibility and Nutritive Value of Bread. 1903. 
 129. Dietary Studies: Boston and other Places. 1903. 
 132. Further Investigations among Fruitarians. 1903. 
 152. Dietary Studies with Harvard University Students. 
 162. Studies on Influence of Cooking on Nutritive Value of Meats. 
 227. Calcium, Magnesium and Phosphorus in Food and Nutrition. 
 
238 BIBLIOGRAPHY 
 
 Bureau of Chemistry, Bulletins 
 
 No. 13. Foods and Food Adulteration — (Ten Parts). 
 
 45. Analyses of Cereals. 
 
 50. Composition of Maize. 
 
 59. Composition of American Wines. 
 
 61. Pure Food Laws of Foreign Countries. 
 
 66. Fruits and Fruit Products. 
 
 69. Foods and Food Control. 
 
 72. American Wines at Paris Exposition of 1900. 
 
 77. Olive Oil and Its Substitutes. 
 
 84. Influence of Food Preservatives and Artificial Colors on Digestion and 
 
 Health. 
 
 100. Some Forms of Food Adulteration and Simple Methods for their De- 
 tection. 
 
 107. Official and Provisional Methods of Analysis. 
 
 no. Chemical Analysis and Composition of American Honeys. 
 
 114. Meat Extracts and Similar Preparations. 
 
 115. Effects of Cold Storage on Eggs, Quail and Chickens. 
 
 120. Feeding Value of Cereals. 
 
 122. Annual Proceedings A. O. A. C. 
 
 132. Annual Proceedings A. O. A. C. 
 
 137. Annual Proceedings A. O. A. C. 
 
 152. Annual Proceedings A. O. A. C. 
 
 162. Annual Proceedings A. O. A. C. 
 
 164. Graham Flour. 
 
 Farmers' Bulletins 
 
 No. 23. Foods: Nutritive Value and Cost. 1894. 
 29. Souring of Milk. 1895. 
 34. Meats: Composition and Cooking. 1896. 
 74. Milk as Food. 1898. 
 
 85. Fish as Food. 1898. 
 93. Sugar as Food. 1899. 
 
 112. Bread and the Principles of Bread Making. 1900. 
 
 121. Beans, Peas, and other Legumes as Food. 1900. 
 128. Eggs and their Uses as Food. 1901. 
 
 131. Household Tests for Detection of Oleomargarine and Renovated Butter. 
 
 1901. 
 
 142. The Nutritive and Economic Value of Food. 1901. 
 
 182. Poultry as Food. 
 
 249. Cereal Breakfast Foods. 
 
 252. Maple Sugar and Sirup. 
 
 293. Use of Fruit as Food. 
 
 332. Nuts and their Uses as Food. 
 
 363. Use of Milk as Food. 
 
 490. Bacteria in Milk. 
 
BIBLIOGRAPHY 239 
 
 Much valuable information will also be found in the regular bulletins and re- 
 ports of several of the State experiment stations and boards of health, notably 
 those of Connecticut, North Dakota, Maine, Kansas, New Hampshire, Vermont 
 and Massachusetts. The "Food Inspection Divisions" and "Notices of Judg- 
 ment" issued from time to time in the enforcement of the Federal Pure Food 
 Law also contain interesting information concerning the adulteration of food. 
 
INDEX 
 
 Page 
 
 Acid, sulphanilic, reagent 229 
 
 sulphuric, reagent for air analysis 228 
 
 Adams' method for fat 141 
 
 Adulteration, cause of 124 
 
 character of 128 
 
 definition of 124 
 
 extent of 128 
 
 Air, amount of, required 18 
 
 bacteria in " 10, 42 
 
 collection of samples of 24 
 
 composition of expired n 
 
 composition of inspired 9 
 
 dust in 9 
 
 essential to life 2 
 
 humidity of 9, 14 
 
 methods of analysis of 21 
 
 purification 20 
 
 poisonous gases in 10 
 
 Alcohol, determination of 191 
 
 table 217 
 
 Alkalinity, determination of, in water 92 
 
 Alum, determination of, in water 95 
 
 Alumina, milk of 230 
 
 Ammonia, albuminoid, determination of 72 
 
 significance of 61 
 
 free, determination of 72 
 
 significance of 62 
 
 free water 228 
 
 standard solution of 229 
 
 Ammonium oxalate solution, standard 232 
 
 Analysis, air, methods of 21 
 
 water, methods of 69 
 
 accuracy of methods of 59 
 
 expression of results of 58 
 
 interpretation of results of 56 
 
 Ash, in cereals 180 
 
 in wine 193 
 
 of milk 141 
 
 241 
 
242 INDEX 
 
 Page 
 
 Babcock method for fat 142 
 
 Bacteria in air, 10 
 
 determination of 42 
 
 Barometers 21 
 
 Basic lead acetate 233 
 
 Beer, analysis of 197 
 
 Benzoic acid, detection of 196 
 
 Bibliography 234 
 
 Bleach, use of, in water sterilization 54 
 
 Boric acid, detection in milk 154 
 
 Breakfast foods 130 
 
 Butter, analysis of 165 
 
 composition of 162 
 
 Federal standard for 164 
 
 microscopic examination 178 
 
 Butter-fat, composition of 163 
 
 Calcium chloride solution, standard 231 
 
 Calorie, definition of 117 
 
 Calorific value 117 
 
 Cane-sugar, detection in milk 150 
 
 Caramel in vanilla extracts 204 
 
 Carbohydrates, function of 115 
 
 Carbon dioxide, allowable amounts in air 17 
 
 determination of, in air 27 
 
 in water 84 
 
 in expired air n 
 
 in inspired air 9 
 
 poisonous action of 12 
 
 table of weights of cubic centimeters of 209 
 
 use as a ventilation test 17 
 
 Carbon monoxide in air 10 
 
 determination of 40 
 
 Carbonaceous matter in water, determination of 85 
 
 Casein, determination in milk 146 
 
 Cereals, analysis of 180 
 
 composition of 181 
 
 Chloride of lime, use in water sterilization 54 
 
 Chlorides in water, significance of 64 
 
 determination of 84 
 
 Chlorine, map of normal 65 
 
 in water, see chlorides. 
 
 Cholera 44 
 
 Coal-tar dyes, detection of 194 
 
 Cohen and Appleyard method for air analysis 37 
 
 Collection of samples of air 24 
 
 water 69 
 
INDEX 243 
 
 Page 
 
 Color in water, determination of 105 
 
 Color, detection in milk 154 
 
 Colors in food 132 
 
 Comfort 11 
 
 curve of 16 
 
 Cooking, changes caused by 116 
 
 Coumarin, determination of 201 
 
 Crowd poisoning, theory of 12 
 
 Crude fibre 188 
 
 Dextrin, determination in cereals 185 
 
 Dietaries 120 
 
 Dust in air 9 
 
 determination of 23 
 
 Electric muffle furnace 88 
 
 Erythrosine indicator 231 
 
 Ether, anhydrous 233 
 
 extract in cereals 182 
 
 Extract in beer-wort 222 
 
 in wine 192 
 
 in wine, table 220 
 
 Fat, determination in milk 141 
 
 in cereals 182 
 
 Fats, function of 114 
 
 Fehlings' solution 233 
 
 Ferric alum 233 
 
 Ferrous ammonium sulphate, standard solution 89, 231 
 
 Filter galleries 50 
 
 Filters, water 52 
 
 Filtration, methods of 52 
 
 Fitz shaker 39 
 
 Food, composition of 112 
 
 definition and uses 111 
 
 essential for lif e 5 
 
 materials, composition of 118 
 
 principles 112 
 
 values, discussion of 122 
 
 Foods, predigested 129 
 
 "Fore" milk 138 
 
 Formaldehyde, detection in milk 151 
 
 Free acids, in wine 193 
 
 Gottlieb method for fat 143 
 
 Ground waters 48 
 
 Gunning method 184 
 
244 INDEX 
 
 Page 
 
 Hale and Melia method for dissolved oxygen 101 
 
 Hanus method 171 
 
 Hardness, acid method for 91 
 
 permanent, determination of s . 93 
 
 soap method for 90 
 
 table of 216 
 
 temporary, determination of 92 
 
 total, determination of 94 
 
 Hazen's theorem 45 
 
 Heat loss from the body, methods of 13 
 
 Heat of combustion 117 
 
 Hehner value 1 70 
 
 Hehner's acid method for hardness 91 
 
 Humidity 9 
 
 determination of 22 
 
 effect on heat loss of 14 
 
 table of relative 210 
 
 Hygrometer, hair 22 
 
 Ice 55 
 
 Imhoff tank 61 
 
 Indicator, erythrosine 231 
 
 methyl orange 231 
 
 potassium chromate 84, 230 
 
 Iodine value 171 
 
 Hanus solution for 232 
 
 Iron in water, determination of 89 
 
 standard solution of 231 
 
 Jackson's candle turbidimeter 95 
 
 Kjeldahl method 183 
 
 process for nitrogen in water 78 
 
 reagents for 230 
 
 Kubel's hot acid method 86 
 
 Lead in water, determination of 97 
 
 number of vanilla 202 
 
 standard solution of 232 
 
 Lemon color 207 
 
 extract 205 
 
 oil, determination of 206 
 
 Lime water reagent for air analysis 38, 228 
 
 Logwood test for alum in water 95 
 
 Loss on ignition, determination of, in water 87 
 
 Low's method for alum in water 96 
 
INDEX 247 
 
 Page 
 
 Silver nitrate solution 84, 230 
 
 Skimmed milk, detection of 161 
 
 Soap method for hardness 90 
 
 solution, standard 231 
 
 Soda reagent 93, 231 
 
 Sodium carbonate, detection in milk : 154 
 
 Sodium chloride solution, standard 84, 230 
 
 thiosulphate solution, standard 232 
 
 Solids of milk 140 
 
 Sonden apparatus for air analysis 27 
 
 Specific gravity of milk 139 
 
 correction table 216 
 
 solids 162 
 
 wine 191 
 
 Spoon test 177 
 
 Standards for ammonia determination 75, 77 
 
 Starch, determination of 186 
 
 Steam vacuum method for air samples 25 
 
 " Strippings " 138 
 
 Sulphanilic acid 80, 229 
 
 Sulphates in water, determination of 95 
 
 table of 215 
 
 Sulphites, detection of 198 
 
 Sugars in cereal products . 185 
 
 Surface waters 46 
 
 Temperature, determination of 21 
 
 effect on heat loss 13 
 
 Tests on water, value of 67 
 
 Thermometers, wet and dry bulb 22 
 
 Turbidimeter for sulphates 95 
 
 Turbidity, determination of 108 
 
 Turmeric in lemon extract 207 
 
 Typhoid fever 45 
 
 Ultraviolet light for water sterilization 54 
 
 Vanilla, adulteration of 200 
 
 determination of 201 
 
 extract 199 
 
 Vapor tension of water, table of 208 
 
 Ventilation 17 
 
 formulae 18 
 
 methods of 19 
 
 Volatile acids, in wine 194 
 
 Walker method for carbon dioxide 28 
 
 Water, analytical methods 69 
 
248 INDEX 
 
 Page 
 
 Water, bacteriological examination of 57, 109 
 
 chemical examination of 59, 67 
 
 consumption 43 
 
 cycle of 45 
 
 daily quantity required 4 
 
 ground , . . 48 
 
 need of 3 
 
 physiological action of 43 
 
 purification of 51 
 
 rain 45 
 
 relation to disease 44 
 
 safe 56 
 
 necessity of 45 
 
 samples, collection of 69 
 
 sanitary examination of 57 
 
 siphon method 24 
 
 sterilization of 54 
 
 storage of 46 
 
 supplies, requirements for 56 
 
 surface 46 
 
 vapor in air, see Humidity. 
 
 waste 43 
 
 Waters, table of average composition of 211 
 
 table of normal 212 
 
 tables of polluted 213 
 
 Wells, deep 49 
 
 shallow 49 
 
 Wine, composition of 190 
 
 Winkler method for dissolved oxygen 100 
 
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