II. Nicotinic acid melting at 235°C. C_6H_5O_2N.
Funk held at the time that the possible nature of the compound was:
HN
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OC C_16H_18O_6
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HN
It was this idea that led him to call it an "amine."
We are unable at present to report any nearer approach to the elementary analysis and all attempts at purification have shown a tendency to make the active substance either disappear entirely or else distribute itself over the several fractions instead of concentrating itself in one. Its basic nature seems to be well established by its behavior with phosphotungstic acid and its ready adsorption by carbons activated to take up basic substances.
III. THE CHEMICAL PROPERTIES OF WATER-SOLUBLE "C"
The properties of this newest member of the family are still less defined. All are agreed that it is much more sensitive to heat and alkali than the other two. Temperatures above 50°C. are usually destructive though the time factor is extremely important as well as the reaction. Hess for example has found that the temperature used to pasteurize milk continued for some time, is more destructive to the vitamine than boiling water temperature continued for only a few minutes. The extent to which orange juice and tomato juice will resist high temperatures indicates the protective action of acids to be considerable.
Dr. Delf's experiments at the Lister Institute were especially directed to the behavior of this vitamine in cabbage. She first determined the minimum close of raw cabbage required to prevent scurvy in guinea pigs and found that it was less than 1.5 grams and more than 0.5 gram daily. When the cabbage was heated in water at 60°C. for an hour, symptoms of severe scurvy were just prevented by 5 grams of the cooked cabbage fed daily. By heating at 70°, 80°, 90° and 100° for the same length of time the 5 grams of cooked material could be made non-effective as a preventive. Her conclusions are that when cabbage is cooked for one hour at temperatures ranging from 80° to 100°C. the cabbage leaves lose about 90 per cent of the antiscorbutic power originally held by the raw equivalent. Sixty minutes at 60° or twenty minutes at 90° to 100° resulted in about 80 per cent destruction. Dr. Delf calls attention also to the fact that the effect of the heat is increased to only a slight degree by rise in temperature. Assuming that the effect of the rise is orderly, a temperature coefficient of 1.3 is indicated for each rise of 10°C. This low result suggests to Delf a contradiction to any theory which imputes to the vitamine enzyme or protein-like qualities and on the other hand suggests that the substance is much simpler in constitution. Her results also confirm Hoist and Fröhlich as showing its great sensitiveness at temperatures of 100° and below and obviously have a direct bearing upon cookery methods.
The substance is soluble in water and passes through a parchment membrane or a porcelain filter. Unlike the "B" it is apparently not adsorbed by fine precipitates such as fullers' earth or colloidal iron. Harden and Zilva showed that when a mixture of equal volumes of autolysed yeast and orange juice is treated with fuller's earth the "B" is removed and the "C" left unaltered. Eddy and La Mer have treated orange juice with fullers' earth and then tested the filtered off juice as cure and preventive of scurvy in guinea pigs. Their results showed that 6-2/3 cc. of the treated juice was curative, hence the loss due to adsorption must be less than 60 per cent to 70 per cent. Harden and Zilva were among the first to state that the vitamine is much more stable in acid than in alkali. They have shown, that even 1/50 N sodium hydrate at room temperature has a rapidly destructive effect. On the other hand Delf showed that when 0.5 gm. citric acid is added to the water in which germinated lentils are boiled, the loss of the antiscorbutic properties is, if anything, greater than when no addition of acid is made. She therefore concluded that in cooking vegetables there should be no addition of either acid or alkali to the cooking water if one wishes to conserve this vitamine. Sherman, La Mer, and Campbell have been engaged in experiments bearing on this point throughout the past two years. Some of their results have recently been published and their observations are worthy of special attention from their bearing on the character of reaction of the vitamine in general. They first proceeded to determine the amount of filtered tomato juice just necessary to produce scurvy in degrees extending from no protection to complete protection and they also constructed a basal diet which is apparently optimum in nutrients and all other factors except the "C" vitamine. They found that at the natural acidity of tomato juice (pH 4.2) boiling for one hour destroyed practically 50 per cent of the antiscorbutic power and by boiling for four hours they destroyed 70 per cent, which indicates that the curve of the destructive process tends to flatten more than that of a unimolecular reaction. This result was confirmed by heating experiments conducted at 60°, 80° and 100°. In all cases the temperature coefficients are low. (Q_10 equals 1.1-1.3) confirming Delf's results. When the natural acidity of the juice was first neutralized in whole or in part, the juice then boiled for an hour and immediately cooled and reacidified, it was found that at less than half neutralization (pH 5.1-4.9) the destructive effect of an hour's boiling was increased to 58 per cent. When alkali was added to an initial pH 11 (about N/40 titratable alkali to phenolphthalein) which fell to 9 during the hour's boiling the destructive effect was about 65 per cent. When reacidification was omitted and the neutralized boiled juice stored in a refrigerator for five days before using the destruction increased 90 to 95 per cent. These particular observations seem to confirm the view of Harden and Zilva that the vitamine is especially sensitive to alkali. Hess has recently reported that oxygen is destructive to this vitamine.