II. cill.MIsi i;v 80.') 



Mcc'toiic. Mild polyliydiic iilcoliols'' liaxc Ih'imi used for clulioii. \'il:miiii li.. 

 is adsorlx'd hy clKircoMl wvy sti'onjily ; liowcxci', rlutioii is diflicult from 

 this adsorhalc. Adsorption occurs furthcrnioro witli lend sulfide, when this 

 is precipitated in a ribofhuin solution; the vitamin can be extracted with 

 hot water from the precipitate. Riboflavin is not adsorbed by kiesclguhr, 

 kaolin, talc, aluminum oxide, or calcium carbonate. 



A combination of precipitation and adsorption methods mostly will be 

 necessary to isolate pure ribofla\in. As examples might be mentioned the 

 isolation of riboflavin from egg white, "^ egg yolk," whey,'^''-'' and urine.''' 

 A general method for the preparation of pure D-riboflavin from natural 

 sources has been described, which is based on adsorption on fuller's earth, 

 fractionation with immiscible solvents and acetone, and crystallization 

 from an acjueous acetone-petroleum ether mixture; aqueous alcohol solu- 

 tions have been used for elution of the adsorbates." 



B. CHEMICAL AND PHYSICAL PROPERTIES 



Ci7lI-2,.X406: molecular weight 376.4; C 54.25%, H 5.36%, N 14.89%. 



Riboflavin crystallizes from 2 A^ acetic acid, alcohol, water, or pyridine 

 in fine orange-yellow needles. The decomposition point is 278 to 282° 

 (darkening at about 240°). Values for the decomposition point between 271 

 and 293° can be found in the literature. The vitamin is odorless and has a 

 bitter taste. 



Riboflavin is soluble in water only to an extent of 10 to 13 mg. in 100 

 ml. at 25 to 27.5°, 19 mg. in 100 ml. at 40°, and 230 mg. in 100 ml. at 100°.i' 

 The vitamin dissolves in ethanol to 4.5 mg. % and is shghtly soluble in amyl 

 alcohol, cyclohexanol, benzyl alcohol, and phenol or amyl acetate. The 

 impure material has a much higher solubility than the pure substance. 

 Alkali dissolves the vitamin w^ell, but these solutions are unstable. There 

 is no solubility in ether, acetone, chloroform, or benzene. Formic acid dis- 

 solves more than 1 % of riboflavin.'^ 



For intravenous administration, sterile, supersaturated solutions of ribo- 

 flavin in normal saline might be employed. By heating to the boihng 



^ S. H. Rul)in and E. De Ritter, /. Biol. Chem. 158, 6.39 (1945); Commercial Solvents 

 Corp., U. S. Pat. 2,34.3,254 (March 7, 1944) [r.yl. 38, .3093 (1944)]. 



i» R. Kiilm, P. Gyorgy, and T. Wagner-Jauregg, Bcr. 66, .570 (1933). 



" P. Karrer, II. Salomon, and K. Schopp, Helv. Chim. Ada 17, 735 (1934). 



'2 R. Kuhn, P. Gyorgy, and T. Wagner-Jauregg, Ber. 66, 10.34, (1933); (b) H. Kului. 

 H. Rudy, and T. Wagner-Jauregg, ibid. 66, 1950 (1933). 



'MV. Koschara, Ber. 67, 761 (19.34). 



" R. D. Greene and A. Black, J. Am. Chem. Soc. 59, 1820 (1937). 



"•C. C. Tzong, J. Fermentation Technol. (Japan) 24, 56, 187 (1946) [C.A. 44, 5975 

 (19.50)]. 



