CHEMICAL CONSTITUTION 



spelling, to conform with the recognised convention that the names 

 of organic bases should end in " ine ", and " Riboflavine " is now its 

 official name in the British Pharmacopoeia. Accordingly, riboflavine 

 is the spelling adopted in this book. 



The method of isolation varied somewhat in different laboratories 

 and with the raw materials employed, but nearly all the workers used 

 adsorption on fuller's earth (or in some instances lead sulphide), from 

 a slightly acid aqueous or aqueous -alcoholic extract. The resulting 

 adsorbate was eluted with p3^idine, or pyridine-methanol-water 

 mixture or dilute ammonia, and the eluate, after being concentrated, 

 was treated with a heavy metal, such as silver or thallium, to precipi- 

 tate the flavine in the form of a salt. The free fiavine was recovered 

 from the precipitate by suitable treatment and recrystallised from 

 water, dilute alcohol or dilute acetic acid. One of the most recent 

 methods is that due to R. D. Greene and A. Black.^^ 



The recovery of riboflavine from fermented liquors is discussed on 

 page 152. 



References to Section 2 



1. R. Kuhn, P. Gyorgy and T. Wagner- J auregg, Ber., 1933, 66, 317, 



576 ; Naturwiss., 1933, 21, 560. 



2. P. Ellinger and W. Koschara, Ber., 1933, 66, 315. 



3. O. Warburg and W. Christian, Biochem. Z., 1932, 254, 438 ; 1933, 



266, 377. 



4. L. E. Booher, /. Biol. Chem., 1933, 102, 39 ; 1934, 10'^» 59i- 



5. R. Kuhn, H. Rudy and T. Wagner- Jauregg, Ber., 1933, 66, 1950 ; 



R. Kuhn and H. Kaltschmitt. ibid., 1935, 68, 128. 



6. P. Karrer and K. Schopp, Helv. Chim. Ada, 1934, 17, 735, 771 ; 



1936, 19, E33. 



7. W. Koschara, Ber., 1934, 67, 761. 



8. H. von Euler and E. Adler, Z. physiol. Chem., 1934, 223, 105. • 



9. S. Itter, E. R. Orent and E. V. McCollum, /. Biol. Chem., 1935. 



108, 579. 

 ID. R. D. Greene and A. Black, /. Amer. Chem. Soc, 1937, 59» 1820. 



3. CHE2VUCAL CONSTITUTION OF RIBOFLAVINE 



Riboflavine has the empirical formula, Ci7H2oN40fi. It was 

 found to be reversibly reduced by sodium dithionite solution, by 

 zinc in acid solution, by hydrogen in presence of a catalyst, by titan ous 

 chloride or by hydrogen sulphide in alkaline solution to a leuco- 

 compound, which was re-oxidised to riboflavine on shaking with air.^ 

 It was stable to most oxidising agents, but chromic acid decomposed 

 it with formation of ammonia, carbon dioxide and a nitrogen-free 



135 



