OCCURRENCE OF THE VITAMINS A 689 



new method of Embree and Kiihrt^^" in which the ester and free alcohol are 

 separated by distribution between petroleum ether and 83% aqueous 

 ethanol. The results of their studies are recorded in Table 8. 



TABLE 8 

 Vitamin A Ester Analyses as Determined by Petroleum Ether: 83% Ethyl 

 Alcohol Distribution" 



" H. M. Kascher and J. G. Baxter, Ind. Eng. Chem., Anal. Ed., 17, 499-503 (1945). 

 p. 499. 



Kascher and Baxter^^^ have demonstrated not only the high proportion 

 of ester in a wide variety of fish liver oils and distilled concentrates, but also 

 the high accuracy of their technic, by obtaining a quantitative recovery of 

 vitamin A alcohol when added to the fish liver oils or vitamin A concen- 

 trates. The reason for the aberrant results obtained by the fluorescence 

 technic is ascribed to the fact that this method cannot be employed satis- 

 factorily with fish liver oils or vitamin A concentrates. 



Vitamin A may also be combined with protein under certain conditions so 

 that it becomes unextractable with ordinary fat solvents until it is hy- 

 drolyzed. Although simple extraction methods are ample for removing 

 this vitamin from most tissues, ^^^-^^^ Lovern et al.^'' have reported that in 

 fish eyes vitamin A is not directly extractable, and that it can be removed 

 only after its separation from the protein. These protein-vitamin A com- 



'*" N. D. Embree and X. H. Kuhrt, Unpublished results, reported by H. M. Kascher 

 and J. G. Baxter, Ind. Eng. Chem., Anal. Ed., 17, 499-503 (1945). 

 121 A. \T. Davies, Biochem. J., 27, 1770-1774 (1933). 

 1" L. I. Pugsley, /. Biol. Chem., 128, Ixxx (1939). 



