The vitamin D problem

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Abstract
If the necessary precautions are taken, the change of the rotation of ergosterol solutions on irradiation with longwave ultra-violet rays is very simple, the rotation showing a linear dependence on the degree of transformation of the ergosterol. These experiments provide further proof for the authors'' hypothesis that under definite conditions long-wave irradiation of ergosterol gives rise to one reaction-product only, which, on account of its intense antirachitic activity, must be vitamin D. From these experiments the rotation of vitamin D is calculated to be (a)d = 66.7[degree] [plus or minus]2.7[degree] (in ether). From correctly irradiated solutions, crystalline ergosterol-free preparations of vitamin D may easily be produced by re crystallisation and treatment with digitonin in vacuo. As a result of the instability of the vitamin D the properties of these preparations vary with the time and temperature used during the performance of the necessary operations.

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