58 THE VITAMINS 



water (in which it was very soluble), reprecipitating by alcohol to 90 

 per cent concentration, digesting under absolute alcohol and drying 

 over sulfuric acid yielded a light-colored friable product equivalent to 

 37 per cent of the solids of the extract or 6.2 per cent of the dried yeast. 

 It contained 7.5 per cent of nitrogen, equal to 4.5 per cent of the nitro- 

 gen of the original yeast, and 10.65 per cent of ash. Numerous feeding 

 experiments showed it to be highly efficient in promoting the growth 

 of young rats when fed as the sole source of water-soluble vitamin and 

 in restoring animals which were declining on a diet lacking in these 

 vitamins. 



Osborne and Wakeman determined the distribution of nitrogen be- 

 tween humus, ammonia, amino, basic, and purine forms in this yeast 

 fraction before and after hydrolysis with results indicating the presence 

 of relatively large proportions of nucleic acid, amino acids, and peptides. 

 An aqueous solution of the fraction was distinctly acid to litmus, re- 

 quiring considerable alkali for neutralization and still more to produce 

 an alkaline reaction. The unneutralized solution gave a heavy precipi- 

 tate with lead acetate, but only slight turbidity with barium chloride 

 or with silver nitrate unless previously neutralized with sodium hy- 

 droxide, when an abundant precipitate formed. Barium hydroxide gave 

 a voluminous precipitate containing about 25 per cent of the solids of 

 the fraction and very little nitrogen. On adding silver nitrate to the 

 filtrate from the barium hydroxide precipitate about 25 per cent more 

 of the fraction was precipitated. This, when thoroughly washed, con- 

 tained nearly one-half of the nitrogen of the fraction. The aqueous 

 solution of Fraction II on acidification with sulfuric acid gave an 

 abundant precipitate with phosphotungstic acid, a precipitate with mer- 

 curic chloride, but none with copper sulfate, and a precipitate with 

 an aqueous or alcoholic solution of picric acid if added in considerable 

 quantity. 



In a further study of this yeast fraction Osborne and Leavenworth 

 (1921) found that its efficiency as a source of vitamin B, as indicated 

 by growth experiments with rats, was only slightly, if appreciably, 

 affected when the material was dissolved in tenth-normal sodium hy- 

 droxide and allowed to stand at a temperature of 20° C. from one-half 

 hour to 18 hours, whereas when such a solution stood for 90 hours 

 at 20° C. its efficiency was very greatly reduced, indicating the destruc- 

 tion of a large proportion of the vitamin present. A still larger pro- 

 portion, if not the whole, of the vitamin present was destroyed when 

 a solution of the same alkalinity after standing for 18 hours at 20° C. 

 was heated for one hour at 90° C. The authors concluded that, in at- 



