214 



VITAMIN D GROUP 



closed systems or by replacing the air over solutions with inert gas. Ether 

 used as a solvent should be peroxide-free. Stabilizers added to the solution 

 are claimed to greatly increase the yield of vitamin. Among these, various 

 sugar amines have been employed.^ The most effective stabilizers appear to 

 be the non-provitamin D sterols, such as cholesterol or the inactivatable 

 fraction of moUusk sterols. Waddell and Woessner'" claim that in the activa- 



FlG 



16. Irradiating units in series for vitamin D production. Each unit consists of 



a vertical quartz mercury lamp surrounded by two cylindrical chambers through 

 which water circulates for cooling. The solution of ergosterol or other provitamin D 

 is circulated through a third cylindrical chamber. (Courtesy of E. R. Squibb and 

 Sons.) 



tion of 7-dehydrocholesterol the presence of an equal amount of cholesterol 

 increases the vitamin yield almost 40 %, besides enhancing the recovery of 

 unconverted provitamin. The highly unstable provitamins D of mollusks 

 are protected by the non-provitamin D sterols which naturally accompany 

 them. When, in the course of repeated irradiations, the protecting sterols 

 of the mollusk sterol mixture accumulate excessively, they can be removed 

 and converted into provitamins by reactions analogous to those employed 

 in the synthesis of T-dehydrocholesterol.^i The stabilization of provitamins 



9 H. W. EUey and J. Waddell, U.S. Pat. 2,234,554 (1941). 



10 J. Waddell and W. W. Woessner, U.S. Pat. 2,410,254 (1946). 



11 H. R. Rosenberg, U.S. Pat. 2,475,917 (1949). 



