224 PYRIDOXINE AND RELATED COMPOUNDS 



with aqueous platinic chloride to precipitate impurities. The concentrate 

 was further treated with phosphotungstic acid, and the vitamin was pre- 

 cipitated. From the decomposed phosphotungstate pyridoxine was precipi- 

 tated from alcohohc solution with ether. The vitamin was isolated in crystal- 

 line form, presumably as the free base. 



e. Keresztesy and Stevens 



An eluate of a fuller's earth adsorbate prepared from rice bran extract 

 was hydrolyzed successively with strong hydrochloric acid and sodium hy- 

 droxide in the method used by Keresztesy and Stevens. ^^ After removal of 

 acetone-insoluble impurities, the concentrate was acetylated and the hy- 

 drolyzed acetyl derivatives were fractionated with phosphotungstic acid. 

 The hydrochloride of pyridoxine was recovered from the decomposed phos- 

 photungstates with acetone from alcoholic solution. 



/. Ichiba and Michi 



Isolation was accomplished by Ichiba and Michi^ by removing impurities 

 with lead acetate followed by adsorption on acid clay and charcoal. Frac- 

 tional precipitation of the alcoholic mercuric chloride-soluble fraction re- 

 sulted in crystals which could be fractionated wdth alcohol. 



B. CHEMICAL AND PHYSICAL PROPERTIES 



1. Chemical Properties 



Pyridoxine exhibits the properties of a stable hydroxylated weak nitrogen 

 base. Birch and Gyorgy^ found that it was not precipitated from solution 

 by the heavy metal salts such as those of lead, mercury, silver, or platinum 

 and not by picric acid but was precipitated by phosphotungstic acid. It was 

 not inactivated by nitrous acid. Hydrolytic agents such as mineral acids 

 or ac^ueous alkali, hot or cold, do not affect the vitamin. ^^ It is stable to 

 the action of agents such as ethyl nitrite and Fehling's solution. With fer- 

 ric chloride, pyridoxine reacts as a phenolic substance giving a reddish- 

 brown coloration. In alkaline solution, pyridoxine on treatment with 2,6- 

 dichloroquinone chlorimide gives an immediate blue color fading to 

 reddish-brown. 1^ This last reaction was used as the basis of a color test for 

 the vitamin.^'*' ^^ 



11 J. C. Keresztesy and J. R. Stevens, U. S. Pat. 2,287,042 (1943). 



12 J. C. Keresztesy and J. R. Stevens, J. Am. Chem. Soc. 60, 1267 (1938). 



13 E. T. Stiller, J. C. Keresztesy, and J. R. Stevens, /. Am. Chem. Soc. 61, 1237 (1939). 

 " J. V. Scudi, H. F. Koones, and J. C. Keresztesy, Proc. Soc. Exptl. Biol. Med. 43, 



118 (1940). 

 " J. V. Scudi, J. Biol. Chem. 139, 707 (1941). 



