RADIATION AND VITAMINS 331 



definite addition compound in the ratio of 1:1, this being the vitamin Di 

 of the German workers. 



3. Tachysterol. — C28H43OH; m.p. indeterminate; principal absorp- 

 tion band at 2800 A, lesser bands at 2680 and 2940 A; [a]546i = -86.3°; 

 [a]^8 = -70° in ''Normalbenzin." 



Windaus, LUttringhaus, and Busse (99) remo^'ed from the crude 

 resin another sterol which they called Tachysterin. This was the object 

 of a special study by Windaus, v. Werder, and Liittringhaus (101), who 

 prepared it from the addition compound, tachysteryl acetate citraconic 

 anhydride, via tachysteryl 3.5-dinitro-4-methyl benzoate. These prod- 

 ucts form good crystals, although tachysterol itself does not crystallize. 

 The absorption spectrum of tachysterol is characterized by its great 

 intensity at 2800 A. Tachysterol is a source of trouble in the separation 

 of irradiation products. Besides failing to crystallize, it exhibits an 

 exceptional affinity for oxygen, so great that perbenzoic acid titra- 

 tions to determine its degree of unsaturation have been uninformative. 

 Tachysterol follows lumisterol and precedes calciferol in the sequence of 

 irradiation products. It probably is devoid of antirachitic action, but 

 it may have a slight toxic effect. 



4. Vitamin D. Calciferol— d^UisOU; \T; m.p. 115 to 117°; X 2650 A; 

 [a]l%, = +122°; [a]^° = +102.5° in alcohol. 



By means of an ingenious method of fractional sublimation Askew, 

 Bourdillon, Bruce, Jenkins, and Webster (3) were able to obtain small 

 amounts of potent crystals from the crude resin. The method was 

 improved, and a detailed study of the active crystals was reported by 

 Angus, Askew, Bourdillon, Bruce, Callow, Fischmann, Philpot, and 

 Webster (1). The name, calciferol, was given to the crystalline sub- 

 stance. A few months later Askew, Bourdillon, Bruce, Callow, Philpot, 

 and Webster (2) discovered that the original calciferol was a mixture, 

 separable via the 3.5-dinitrobenzoate into pure calciferol and two inactive 

 sterols. One of the latter, pyrocalciferol, was merely a thermal trans- 

 formation product, produced during the distillation. The other, "sterol 

 X," had probably come over from the original irradiation product. By 

 the new esterification method calciferol could be obtained directly from 

 the resin, without distillation. The antirachitic potency of pure calciferol 

 was found to be 40,000 international units per milligram. 



While the isolation of calciferol was in progress in England, Windaus 

 and his associates in Germany were developing a different technique 

 to the same end. Windaus (90) and Windaus, Luttringhaus, and 

 Deppe (100) reviewed their preliminary studies on activation, and 

 announced that a crystalline vitamin D was obtained by removing the 

 inactive components of the resin by means of maleic or citraconic anhy- 

 dride. Soon after this, Linsert (54) obtained another crystalline prepa- 

 ration somewhat different in its properties from the first. For a few 



