THE FOLIC ACID COMPLEX 



was C21H24N7O8. The solubility of the substance in water at pK 3 was 

 approximately 10 /itg. per ml. at 2° C. and 0-5 mg. per ml. at 100° C.^ 

 The factor was insoluble in the common organic solvents, but soluble 

 in glacial acetic acid, phenol and methanol. "^ The extinction co- 

 efficients in o-i N sodium hydroxide were : 



ETcm. 255ni)[i., 565; 282m/i., 350; 365 m/^., 195. 



Fermentation L. casei Factor 



The fermentation L. casei factor differed from the liver factor in 

 its biological activity ; whereas it was 60 to 80 % as active as the liver 

 compound towards L. helveticus, it was only 4 to 6 % as active for 

 S. faecalis R.^ No reliable combustion figures could be obtained for 

 the substance, which clearly had a composition different from that of 

 liver factor, however.® The absorption spectrum was similar to that 

 of the liver factor, but the extinction coefficients were lower, indicating 

 that the fermentation factor had a higher molecular weight.® 



Vitamin Be Conjugate 



Vitamin Be conjugate, prepared from yeast by Pfiffner et al. ^ had a 

 lower nitrogen content than had vitamin Be, and, although the absorp- 

 tion spectra of the two substances were similar, the relative values of 

 the extinction coefficients indicated that the molecule of the conjugate 

 was nearly three times as big as that of vitamin Be. It had practically 

 no growth-promoting action for either L. helveticus or 5. lactis R. 



SLR Factor (Rhizopterine) 



Rhizopterine had the empirical formula, C15H12N6O4, and was 

 highly active towards 5. lactis R, but substantially inactive towards 

 L. helveticus. Unlike the L. casei factors, it did not stimulate growth 

 or haemoglobin formation in chicks, and did not cure granulocytopenia 

 in rats induced by feeding succinylsulphathiazole.^^ 



It was a pale yellow solid which did not melt below 300° C. It 

 was insoluble in the common organic solvents and water, but soluble 

 in mineral acids and alkalis. It was therefore difficult to purify by 

 crystallisation, but yielded a crystalline complex with luteo-ethylene- 

 diaminocobaltic chloride and ammonia ; ^^ treatment of the complex 

 with dilute acetic acid yielded pure rhizopterine. 



Xanthopterine 



Xanthopterine is a yellow solid with a melting-point higher than 

 400° C, and it can be crystallised only with great difficulty. It is very 

 sparingly soluble in organic solvents and cold water, but readily 

 soluble in hot water and in hot ethylene glycol and glycerol. 



478 



