VITAMIN A 237 



(f) "indicated that vitamin A passed over mainly between 180°-220° 

 at 2-3 mm." 



Even the most active distillate, however, could not be regarded as 

 an isolated vitamin A for it appeared to be a mixture of at least three 

 substances. "Chemical examination of active distillates indicated the 

 presence of (a) a saturated soHd alcohol (m.p. about 60°), (b) the 

 unsaturated hydrocarbon spinacene, (c) one or more than one unsatu- 

 rated alcohol,, boiling about 200° at 2-3 mm." (Drummond, Channon 

 and Coward, 1925.) Separations of these substances could not be effected 

 either by re-distillation, crystallization from solvents, or attempts to 

 fractionate through differential solubilities. In the judgment of these 

 investigators, the final products obtained, both in their own attempts at 

 isolation and in those of Takahashi and his coworkers, must still be 

 regarded as mixtures. 



The authors considered that this work conclusively proves that 

 vitamin A can be distilled either with super-heated steam or directly 

 under reduced pressure, and still retain its characteristic activity; but 

 that it is not definitely established whether the vitamin activity is due 

 to an unsaturated sterol or not. "No satisfactory answer to this question 

 can be given until the active constituent has been isolated in pure con- 

 dition or as a derivative suitable for purification. It was of interest to 

 observe that, during the course of exhaustive experiments to obtain 

 solid derivatives suitable for purification and examination, the vitamin 

 activity of our fractions survived certain chemical treatments of the 

 hydroxyl group of the alcohols present, e.g., acetylation, benzoylation, 

 and treatment with phthalic anhydride or substituted benzoyl chlorides, 

 but in no case did it survive exposure to reagents that affected the 

 unsaturated linkages, e.g., bromination, reduction." 



The observations just mentioned, taken in conjunction with the fact 

 that the unsaturated hydrocarbon spinacene is without vitamin A action, 

 plainly furnish another indication of the possibility that vitamin A may 

 prove to be an unsaturated alcohol of the "sterol" group ; but the authors 

 concluded that, "It has not been possible to decide whether vitamin A 

 is identifiable with one of the unsaturated alcohols. . . . The unsatu- 

 rated alcohols, oleyl alcohol (CigHgeO) and selachyl alcohol 

 (C20H40O3), which have been described as constituents of other liver 

 oils, are not identifiable with vitamin A. The unsaturated alcohol, phytol 

 (C20H40O), which is present in the chlorophyll molecule, is also devoid 

 of activity." (Drummond, Channon and Coward, 1925, p. 1066.) 



Drummond and Baker (1929a) concluded from further studies of 

 the chemical nature of vitamin A that the active substance is present in 



