64 THE VITAMINS 



has been studied extensively by Salmon, Guerrant and Hays (1928a). 

 In experiments in which they kept the volumes and the amounts of 

 fuller's earth proportional to the weight of the original material, they 

 found the effect of pH upon the antineuritic potency of the "activated 

 solids" by comparing the number of protective doses for pigeons per 

 100 grams adsorbate prepared over a range of pH's from 0.5 to 11.9. 

 Maximum adsorption of vitamin B occurred between pH 3.0 and pH 

 5.5 (equilibrium reaction), with inactivation beginning at pH 6.8 and 

 increasing significantly throughout the alkaline range. Poor adsorption 

 in the alkaline range could not be attributed entirely to inactivation of 

 the vitamin, for a second adsorption of the same solutions adjusted to 

 a favorable pH, removed 10 times as much antineuritic vitamin as had 

 the initial adsorption process. This inactivation emphasizes, however, 

 the importance of using weakly alkaline solutions and a short exposure 

 to alkali when using alkaH to remove the adsorbed substance from 

 fuller's earth. 



The efifect of pH upon adsorption of the antineuritic factor by 

 fuller's earth from maize and yeast extracts seemed to be similar to 

 its effect upon the adsorption of quinine; whereas the effect of pH upon 

 adsorption of the more heat stable factor seemed to be similar to its 

 effect upon the adsorption of glucose. Fuller's earth seemed to be a 

 more efficient adsorbent for vitamin B than for vitamin G. 



From brewers' yeast, 30 milligrams daily of which contained enough 

 vitamin B (Bi) for normal growth, Levene (1928) made a concentrate 

 similar to Osborne and Wakeman's. The wet brewers' yeast was treated 

 with 95 per cent alcohol for 4 hours at 60° C., filtered, and the filtrate 

 concentrated under reduced pressure. The addition of an equal volume 

 of 95 per cent alcohol precipitated foreign material which was removed 

 by centrifuging. To the resulting clear supernatant liquid, sufficient 

 98.5 per cent alcohol was added to bring the final concentration to 80 

 per cent, whereupon most of the vitamin was precipitated. This pre- 

 cipitate was washed with absolute alcohol and extracted with acetone, 

 and served as a starting material for further concentration. 



Fifty grams of this fraction in a 4 liter volume, with the acidity 

 adjusted to pH 3 by hydriodic acid, was treated 6 times successively 

 with silica gel. The filtrate after being neutralized with lithium hydrox- 

 ide, concentrated, and centrifuged to remove foreign material, was 

 brought to an 80 per cent alcohol concentration, upon which treatment 

 a vitamin G (B2) -containing material precipitated out, apparently 

 essentially free from vitamin Bi, and 30 milligrams of which supported 

 growth when vitamin B was supplied. 



