Photolysis of the Previtamin

It has been found that prolonged irradiation of the initial quasi stationary state results in new products being formed in an irreversible process. The structure of these products, derived primarily from the previtamin and called toxisterols, have recently been investigated in two laboratories. The nature of the product mixture obtained depends on the temperature and the type of solvent used in the photolysis as well as on the wavelength of the light used. 

In Barton s laboratory, ergosterol was irradiated in a quartz apparatus at room temperature with a high pressure mercury arc lamp until the starting sterol absorption reached a minimmn (24 hours in 

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