126 THE VITAMINS 



of that required to maintain weight and promote growth. The require- 

 ment of this latter factor seemed to be dependent upon the type and 

 proportion of carbohydrate furnished in the basal diet. 



Hunt (1928, 1928a, 1928b) has reported the existence in yeast of 

 three vitamins necessary for the growth of rats. 



Concentration of Vitamin G 



The finding that Peters' antineuritic concentrate made from yeast 

 extract is practically free from vitamin G (Bo) led Chick and Roscoe 

 (1929a) to study at what point the latter is left behind in the process 

 of fractionation, and to attempt a separation of vitamin G (Bo) free 

 from vitamin B (Bi). They found that the vitamin G (Bo) of the 

 acidulated aqueous extract of washed brewers' yeast is precipitated 

 largely by lead acetate, the amount depending upon the acidity, and 

 that most of any remainder was precipitated with the barium hydroxide. 

 At pH 2.6, the lead acetate precipitated about one-half of the vitamin 

 G (B2) ; at pH 4.7, about three- fourths; and in neutral or alkaline 

 medium, practically all. Under these conditions they were unable to 

 separate vitamin G (Bo) from vitamin B (Bi) ; about one-half of the 

 original vitamin B being found in the vitamin G fraction, the amount 

 apparently depending both on the acidity and the relative amounts of 

 the vitamins in the source material. 



These authors found that after an acidified (pH 3) aqueous extract 

 of yeast was dialyzed for 4 days in a refrigerator in a "cellophone" 

 bag against distilled water, the concentration of vitamin G (Bo) was 

 the same on both sides of the membrane. In their experience, ultra- 

 violet irradition inactivates both vitamins B (Bi) and G (Bg), the 

 latter to a greater degree. They confirmed earlier workers in the finding 

 that vitamin G (B2) is insoluble in 83 to 95 per cent alcohol. The pre- 

 cipitate formed when an aqueous (acid) concentrate of this vitamin 

 was slowly added with vigorous stirring to a large volume of 94 per 

 cent alcohol, was much reduced in vitamin potency after repeated wash- 

 ings and shaking with 94 per cent alcohol. This loss appeared not to be 

 due either to mere prolonged contact with air at room temperature in 

 the dry condition, nor could it be explained only on the basis of contact 

 with alcohol of that strength. They suggested that the destructive eflfect 

 of alcohol on vitamin G (B2) may be related to the reaction of the 

 solution. 



Chick (1929) found no diminution of the vitamin B2 (G) potency 

 when the amino nitrogen of the preparation was reduced to one-sixth 

 of the original by the action of nitrous acid. The treatment consisted 



