640 X. VITAMINS D 



lamp and cored carbon electrodes impregnated with different metals.""^ 

 Reerink and van Wijk^^^ employed a bismuth vapor lamp with satisfactory 

 results. For a description of the filters employed, and other details, the 

 reader is referred to Volume I, The Lipids, pp. 759, 760, and to the review of 

 Bills, 2 w^ho described various specific technical methods for carrjdng out 

 irradiation of special products. 



In addition to the usual types of irradiation, other methods have been 

 shown to accomplish the activation of the provitamin D molecule. These 

 procedures include the use of cathode rays,^^^'^*^ alone or with catalysts 

 such as iron or uranium salts. ^^^ Canal rays and the a-, I3-, and 7-rays of 

 radioactive elements have been used. Radium emanation provides an- 

 other method for the activation of the provitamins, D,^*' and corpuscular 

 rays for accompHshing this activation w^as described in a German patent. ^^^ 

 In addition, electrons of high frequency have been widely empoloyed,'*^''^'* 

 as well as alternating current of high frequency. ^^^'^^^ Goldblatt^^^ observed 

 that x-raj^s were unable to effect the activation of provitamins D. On the 

 other hand, later experiments^^^ established the fact that irradiation by 

 cold quartz mercury lamp rendered ergosterol powerfully antirachitic. 

 Bills^''* found radio waves of high intensity and short Avave length entirely 

 ineffective. 



The process of activation is not instantaneous, but requires a given 

 amount of time. A series of compounds are formed in order, prior to 

 vitamin D. When irradiation is continued for a prolonged period, the 

 vitamin D is decomposed, resulting in the formation of products which may 

 be toxic. Analogous series of compounds are formed from each of the 

 provitamins D, but each series varies from the other in the structure of the 

 side chain. The following is the sequence of products formed on irradiation 

 of ergosterol: 



137 E. H. Reerink and A. van Wijk (to N. V. Philips' Gloeilampenfabrieken, Holland), 

 U. S. Patent No. 1,904,751 (Apr. 18, 1933). 



138 A. Knudson and C. N. Moore, /. Biol. Chem., 81, 49-64 (1929). 

 "9 R. M. Hoffman and F. Daniels, /. Biol. Chem. 115, 119-130 (1936). 



i« A. J. Pacini (to Research Products, Inc.) U.S. Patent No. 1,983,9U (Dec. 11, 1934). 

 1" R. B. Moore and T. de Vries, /. Am. Chem. Sac, 53, 2676-2681 (1931). 

 i« K. Hembd and Vitam Fabrik, German Patent No. 577,170 (Aug. 10, 1933). 

 1" Brit. Thompson-Houston Co., British Patent No. 292,926 (Aug. 22, 1928). 

 1" A. Knudson (to Sun-A-Sured, Inc.), U. S. Patent No. 2,007,765 (July 9, 1935). 

 i« I. G. Farbenindustrie, Austrian Patent No. 119,210 (Apr. 15, 1930). 

 "6 C. C. Whittier, U. S. Patent Nos. 2,106,779; 2,106,780 (to Nutrition Research 

 Labs., Inc., Chicago), 2,106,781; 2,106,782 {Yeh. 1, 1938). 



i« H. Goldblatt, Ergeh. allgem. Pathol, path. Anat., Abt. 2, 25, 58-491 (1931). 

 i« H. Goldblatt, Proc. Sac. Exptl. Biol. Med., 30, 380-383 (1932). 



