VITAMIN B (Bt) 109 



Adsorption 



For many years it has been known that vitamin B (as the term 

 lias been heretofore understood) was readily adsorbed on charcoal, 

 fuller's earth and other adsorbing agents as evidenced by the frequent 

 use of this step in the processes of concentration. In the work of 

 Salmon and Guerrant (1928) adsorption of vitamin B from extracts 

 of yeast or maize with fuller's earth or Lloyd's reagent, was found 

 to occur best at about pH 4 (measured after the adsorption process). 

 They considered that vitamin B behaved in adsorption like a basic sub- 

 stance, such as an alkaloid. 



According to Kinnersley and Peters (1928), the other substances 

 present, and perhaps the concentration of the vitamin, determine the 

 pH at which adsorption most effectively occurs. They found that the 

 relations of a highly purified concentrate to charcoal could not be de- 

 fined with certainty, and that successive adsorptions removed no more 

 of the vitamin. They believe that adsorption in the earlier stages is 

 due to the presence of a coadsorbent. When yeast extract had not been 

 treated with mercuric sulfate, adsorption of the vitamin took place at 

 pH 5.0 to 6.0; whereas when so treated it was best adsorbed at pH 

 7.0. Guha and Drummond (1929) confirmed these investigators' find- 

 ings that vitamin Bi is best adsorbed by norite from yeast extract at 

 pH 7, but pointed out that under their conditions it is best adsorbed 

 by norite from an extract from wheat embryo at pH 4 to pH 5. Peters 

 emphasized that the character of an adsorption is exceedingly variable, 

 and that it is dangerous to draw conclusions from one class of mixtures 

 and apply them to another. 



Halliday (1929) made a quantitative comparison of the adsorption 

 of vitamins B and G from "protein-free milk," using varying amounts 

 of Lloyd's reagent (80 grams to 5 grams per liter of solution) with the 

 hydrogen-ion activity of the solution adjusted to pH 4.0 and to pH 3.0. 

 The activated solids were dried at room temperature and fed incor- 

 porated in the basal diet. The filtrates were evaporated to about one- 

 fourth of their volume under reduced pressure, at about 30° to 40° C., 

 neutralized to about pH 5.7, and fed as daily supplements. All portions 

 were fed in quantities corresponding to definite amounts of milk powder 

 or protein- free milk, the initial vitamin content of which had been 

 determined. The results as a whole seem to indicate that equally good 

 adsorption of vitamin B may be expected at hydrogen-ion activities 

 of about pH 3 to pH 5 (measured at equilibrium). The amount of 

 adsorbent may be varied within rather wide limits. The upper limit 

 is governed by the amount which the animal can or will eat in addition 



