124 THE VITAMINS 



third of the antineuritic fraction (vitamin B) was adsorbed by the 

 fuller's earth, while only a negligible amount of the P-P factor (vitamin 

 G) was thus adsorbed. To obtain a concentrate of the latter free from 

 the former, a combination of treatment with small amounts of fuller's 

 earth to remove vitamin B, and fractionation of the resulting filtrate 

 with alcohol was attempted. The filtrate left after the first adsorption 

 with fuller's earth was concentrated by vacuum distillation and then 

 treated with successive portions of fuller's earth. The resulting filtrate 

 and washings were again concentrated, and 2 liters poured into 3 liters 

 of 93 per cent alcohol according to the method of Osborne and Wake- 

 man. The precipitate (Fraction I), after washing with 51 per cent 

 alcohol, was rejected; the filtrate and washings were concentrated to 

 300 cubic centimeters and poured into 3 liters of 93 per cent alcohol. 

 This second precipitate was mixed with cornstarch, macerated in abso- 

 lute alcohol, filtered, washed with absolute alcohol, and dried at from 

 50° to 60° C, making Fraction II. The remaining filtrate and washings 

 were reduced to small volume by vacuum distillation, taken up on corn- 

 starch, and dried (Fraction III). 



Fraction II, by itself, had no growth-promoting properties, but 

 prevented pellagra-like symptoms in rats. When combined with a small 

 amount of the antineuritic factor, growth was promoted. Fraction III 

 was found to retain more of the antineuritic factor (vitamin B) than 

 Fraction II, and to have a more laxative action. 



In discussing their experimental work, the authors advanced the 

 opinion that in the preparation of a vitamin G concentrate, it is prefer- 

 able to remove vitamin B as completely as possible by the method 

 outlined. 



They found that the maximum adsorption of the vitamin G by 

 fuller's earth occurred at pH 0.08, the most acid solution tested. This 

 adsorption decreased gradually to a minimum at pH 6.3, and remained 

 approximately constant to pH 12.07, the most alkaline solution tested. 

 Fuller's earth seemed to be a more efBcient adsorbent for vitamin B 

 than for vitamin G. They pointed out certain discrepancies which they 

 interpret as suggesting that vitamin G may be a composite rather than 

 one substance. (Salmon, Guerrant and Hays, 1928; Salmon, Hays and 

 Guerrant, 1928.) 



Hogan and Hunter (1928) reported that exposure of materials con- 

 taining the vitamin B complex to ultra-violet light apparently does not 

 aflfect the antineuritic properties (vitamin B), but does destroy the 

 activity usually described as growth-promoting (vitamin G). However, 

 Kennedy and Palmer (1929) do not confirm these authors that ultra- 



