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remains in the solution after removal of the silver, with the result that the crystals, which are obtained on slow evaporation, are in both cases nitrates. Feeding tests of the several crystalline compounds on pigeon$ showed that they retain very little, if any, of the antineuritic properties of the ammoniacal silver precipitate. It is possible that the loss of activity may result from the constant presence of nitric acid in the solutions from which the crystals are obtained.
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Far less is known of the antiscorbutic vitaminel than of the antineuritic vitamine. We know that the antiscorbutic vitamine is water-soluble; indeed, it has been called the watersoluble C vitamine. It is also soluble in alcohol and in acetone. It is not adsorbed by the fuller’s earth method introduced by Dr. Beidell; in fact, from a mixture containing both water-soluble B and C vitamines it can be separated by t8hismeans. Little more is known from a purely chemical point of view. But that does not imply that considerable progress has not been made in the past few years in regard to this vitamine. Indeed, since the publication of the report of the British Research Committee, only three years ago, views have altered essentially in this regard. It was previously supposed, and brought forth in 1918 in this report, that this vitamine is destroyed by drying, by aging, by the canning process, and by heating. That had long since been the accepted view in regard to the factors which lead to the destruction of the antiscorbutic vitamine and bring about the development of scurvy. Recently our ideas in this respect have undergone important modifications. Without going into detail in regard to drying, it may be stated that experiment.s of Dr. Unger and the writer12substantiated by others, have clearly shown that although most substances lose, the vitamine in the course of drying, desiccation does not necessarily destroy this vitamine. For instance, milk may be dried to a powder and nevertheless retain the major part of its vitamine. This dried milk may even be aged and still retain this vitamine. It may be canned and aged and dried and still retain its antiscorbutic vitamine and be able to cure infantile scurvy. I n the course of the desiccating process it is subjected to about 240’ F., so that we may add, it also may be heated and nevertheless remain antiscorbbtic. It is evident that there must be some other factor or factors involved in its destruction. Reference should be made in passing to the importance of the reaction of the medium to the stability of this vitamine. It is known to most of you that if an antiscorbutic food is acid, it is much less apt to undergo destruction. For instance, this is the main reason why orange juice can retain its highly antiscorbutic potency in spite of having been boiled. It explains why the tomato is a very efficient antiscorbutic, even after it has been heated, canned, and allowed to age. I n our experience tomatoes canned a year were found to have retained their full antiscorbutic value. Clearly there must be some further explanation for the instability of the antiscorbutic vitamine; heat, to which its destruction has almost universally been attributed, cannot
be the sole or even the preeminent factor. The clinical reports of experienced physicians also lead to this conclusion. For instance, children’s specialists in France have reported that they have fed thousands of babies on hundreds of thousands of bottles of sterilized milk in the course of years, milk that had been heated to the boiling point and over and that throughout this long period they have never encountered a case of scurvy. Surely, such extensive reports covering a period of years cannot be passed over lightly. EFFECT OF OXIDATIONON DESTRUCTION OF VITAMINE Some experiments carried out by the writer in conjunction with Dr. Unger showed that there is another factor, perhaps a more important factor than those mentioned, which leads to the destruction of this vitamine, namely, oxidation.l This action can be demonstrated in a very simple way. For instance, if a liter of milk is treated with a very small amount of hydrogen peroxide (4 cc. of a normal solution) and allowed to stand over night in an incubator a t blood heat, the antiscorbutic vitamine is almost entirely destroyed. This is tested by the biological method; 80 cc. of milk per day per capita are fed to a series of guinea pigs. It is found that all these guinea pigs develop scurvy, whereas control guinea pigs receiving the same amount of milk to which peroxide has not been added remain free from signs or symptoms. Furthermore, the guinea pigs which develop scurvy on this oxygenated milk rapidly lose all symptoms of this disorder when a few cubic centimeters of orange juice are added to the dietary. In other words, the small amount of peroxide thoroughly destroyed the antiscorbutic content of the milk, destroyed it to the same extent as heating milk to 100’ C. for an hour. The authors showed also that if orange juice is subjected to a stream of oxygen its antiscorbutic potency is likewise diminished, and that the same is true of milk. This destructive effect of oxidation has been substantiated by experiments carried out by Dutcher2 in this country and by Zilva a t the Lister Institute in London.8 That antiscorbutic vitamine is sensitive to oxidation is of importance from a theoretical as well as from an industrial point of view. It explains, for instance, why some. dried milk possesses the antiscorbutic property, whereas other dried milk is markedly lacking in this factor. when we stated some years ago that experiments showed that dried milk may have antiscorbutic value, our conclusions met with skepticism. It is now recognized that the nature of the product depends upon the process of drying. If, in the course of drying, milk is subjected to oxygenation, as it is in the spraying process, it loses much or most of its antiscorbutic vitamine, whereas if it is dried on a drum and its particles not subjected to the air, it is found to retain the greater part of this vitamine. Condensed milk retains considerable of this factor, owing to the fact that the condensation process is conducted with very little access of air. This new conception of the role of oxidation harmonizes many views which heretofore appeared discordant. It explains how the French physicians were probably quite correct when they reported encountering practically no scurvy in the course of feeding sterilized milk t o babies; we had paid no attention to the fact that the milk which they fed had been heated in and kept in hermetically sealed bottles. This probably is the more precise explanation of what we have called “aging,” a term which is descriptive but hardly scientific. The aging which destroys the antiscorbutic vitamine is oxygenation.
For fuller information on this subject reference may be made t o the following papers b y the author: “The Role of Antiscorbutics in Our Dietary,” J . A m . Med. Assoc., 71 (1918),941; “Newer Aspects of Some Nutritional Disorders,” I b i d . , 76 (1921), 693. * “ T h e Scurvy of the GuiIiea Pigs. 111-The Effect of Age, Heat, and Reaction of Antiscorbutic Foods,” J . B i d . Chem., 38 (1919), 293.
1 “The Destructive Effect of Oxidation on Antiscorbutic Vitamine,” Proc. Soc. Ex$tZ. B d . M e d . , 18 (19211,143. K. A. Dutcher, H . M. Harsham and J. S. Hall, “Effect of Heat and Oxidation on Antiscorbutic Vitamine,” J . B i d . Chem., 47 (1921), 483. “The Influence of Aeration on the Stability of the Antiscorbutic Factor,” Lancet, 1921 [I], 478.
The Antiscorbutic Vitamine By Alfred F. Hess 16 WEST 86TH ST., NEW YORK,N. Y .
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CATALYSIS Another factor in the destruction of antiscorbutic vitamine is catalysis. Its effect may be illustrated by citing the following experiment. If milk is pasteurized (145" F. for 0 . 5 hr.), heating half of it in a glass vessel, and the other half in a copper vessel for the same length of time, the milk heated in the copper vessel will be found to have lost considerable of its antiscorbutic vitamine. On feeding 80 cc. per capita of these two lots of milk to a series of guinea pigs, the animals receiving the milk pasteurized in the copper vessel will develop scurvy) whereas those receiving the milk which had been heated in the glass vessel will thrive and not develop this disorder. That the signs and symptoms are truly'those of scurvy is proved by their prompt disappearance-in spite of continuing the same milk-if a few cubic centimeters of orange juice are given in addition. The milk heated in the copper vessel contained but three or four parts of copper per million -a very small amount. This experiment has a practical application for, as is well known, milk in the process of pasteurization passes through copper pipes; it is true that these are lined, but the lining frequently becomes defective after a short period. Lined copper vessels are commonly used in the course of condensing and drying milk. It is, therefore, not astonishing that copper
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is found very frequently in small amounts of milk. I n a British medical report, it was found eleven times in eightyseven samples. It is impossible to state how important a factor catalysis is. But whatever may prove to be the scope of its application, an experiment of this nature shows the little suspected factors which may be introduced and which must be taken into consideration in relation to the destruction of this most delicate vitamine, and warns us that in the handling of food products containing vitamines we must consider the influence of every new industrial process. Quite apart from the question of the destruction of the vitamines, the last few years have demonstrated that we should not consider foodstuffs as entities from the standpoint of their vitamine content. A food may be rich or poor in this factor according to attendant circumst,ances. For instance, carrots cannot be classed as containing a definite amount of antiscorbutic vitamine; if they are fresh they will contain much more than if they are old, or, again, if they have been plucked young, they will have far more than if they were tough and old. We must avoid cataloguing foods too rigidly. It is probably of aid to arrange them in categories and to assign them definite potencies, but we must remember that such a list possesses merely comparative and approximate value.
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Some Factors Affecting the Stability and Inversion of Oil-Water Emulsions'" By Leon W. Parsons and 0. G. Wilson, Jr. RESEARCH LABORATORY OF APPLIEDCHEMISTRY, MASSACHUSETTS INSTITUTE O F TECHNOLOGY, CAMBRIDGE, MASS.
SCOPEOF INVESTIGATION This work covers some preliminary results obtained in the course of a fundamental investigation of the properties and behavior of mineral oil-water emulsions. Exact information regarding the properties of commercial emulsions is difficult to obtain and classify accurately on account of the complexity of the factors involved. It is felt that by obtaining more complete information regarding the general principles which govern the behavior of emulsions in simple systems and then applying the information to a systematic study of more complicated emulsions, greater progress may be made than by starting a t once with the study of a few complex emulsions which happen to be of commercial importance. Much, though not all, of the work thus far undertaken has dealt with the inversion point of oil-water emulsions. By definition the inversion point is that point where there is a change from an oil-in-water type of emulsion to a water-in-oil, or vice versa. This evidently marks a region of instability, and hence is of practical importance from the standpoint of breaking emulsions. I n general the work has been divided into three phases: (1) an investigation of the factors affecting the inversion 1 Presented a t the Symposium on Emulsification Problems in the Petroleum Industry before the Section of Petroleum Chemistry at the 62nd Meeting of the American Chemical Society, New York, N . Y., September 6 to 10, 1921. 2 Published as Contribution No. 41 from the Research Laboratory of Applied Chemistry, Massachusetts Institute of Technology, Cambridge, Mass.
point in the case of emulsions with water of a highly purified oil like Nujol; (2) in emulsions containing Nujol to which substances which are known to be present in commercial oils have been added; and (3) in the case of emulsions of different commercial oils. From such investigations, it is hoped that much fundamental information may be obtained which should be of assistance in solving the difficult problems involved in breaking commercial emulsions.
SOMEGENERALPROPERTIES OF OIL-WATEREMULSIONS Although there is much information in the literature regarding emulsions, correlation of the results of various investigations is difficult on account of the difference in the nature of the materials used, the method of studying the emulsions, and the complexity of the factors involved. From a consideration of the literature and from scattered information obtained from various oil companies, an attempt has been made in the chart in Fig. 1 to enumerate some fundamental properties of importance in considering the stability of commercial emulsions. Referring to this chart it will be seen that a rough division may be made of systems ordinarily called emulsions, into mechanical suspensions and true emulsions, the former being characterized chiefly by a greater instability; the latter being characterized by extreme stability which is in general produced by the presence of an effective emulsifying agent. It is realized, however, that no sharp line of demarcation may be drawn between the two. This investigation deals only with true emulsions.
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