Abstract
The work here presented was conceived by the observations of Bills 1 on the action of various reagents on the antirachitic vitamin, and was carried to completion in 1927. It occurred to us that an extension of Bills' work to vitamin A might be of value in throwing light on the chemical nature of this factor.
Of the reagents examined by Bills, sulphur dioxide was found to be without action on the antirachitic vitamin. Early in our investigation, however, we found the effect of this substance on vitamin A in cod liver oil to be of such a magnitude as to render desirable an examination of vitamin A from other sources.
In doing so we were guided by two principal considerations: (1) whether vitamin A activity is the property of a single chemical individual or that of a specific atomic grouping possessed in common by several different molecules; (2) assuming that vitamin A of the green plant would be as susceptible to destruction by sulphur dioxide as vitamin A of animal origin, it occurred to us that one important aspect of the damage to vegetation by smelter smoke would be the destruction of vitamin A. With these considerations before us we gave primary attention to experimentation with sulphur dioxide. Cod liver oil, butter, and extracts of alfalfa were used.
Cod liver oil was treated by bubbling with the purified gas at temperatures of 20° to 100° for periods of 15 minutes to 2 hours. The excess of sulphur dioxide remaining at the end of the experimental time was removed by exposure in vacuo.
Butter was melted at 60°, freed of casein by filtration, and treated with sulphur dioxide at 60° for 1 to 24 hours.
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