ii8 THE CARBOHYDRATES 



however, claim that the action of acid on glucose yields a 

 mixture containing gentiobiose in addition to iso-maltose. 



In a study of the reversible nature of enzyme action, 

 Croft Hill,* in attempting to synthesize maltose by the action 

 of maltase upon glucose, obtained some maltose and in addi- 

 tion an unfermentable sugar which he termed revertose, 

 dehberately avoiding the name isomaltose " because this 

 designation has been applied to several differing substances 

 and revertose is different from any of these." Later Arm- 

 strong showed it to be a j8-glucoside and considered it to be 

 identical with Fischer's iso-maltose. 



According to Lintner and Dullf malt diastase acting upon 

 starch produces, in addition to maltose and dextrin, some 

 unfermentable sugar, iso-maltose; this observation was subse- 

 quently confirmed by Ling, but in the opinion of the latter 

 author, Fischer's iso-maltose produced by the action of acid 

 upon starch is not identical with that produced by diastase.|| 



A method for preparing iso-maltose, due to Ling and 

 Nanji,$ consists in allowing a solution of precipitated malt 

 diastase to act upon crude amylopectin, or upon a^-hexa- 

 amylose prepared from it, at 50° until the rotatory power 

 remains constant, and then fermenting away any maltose 

 or glucose ; the mixture is then filtered, evaporated, and 

 extracted with alcohol. 



Thus prepared, iso-maltose is a white, amorphous, hygro- 

 scopic power having aD=+l40°; it forms an osazone, 

 m.p. 150°, which is soluble in hot water or in absolute alcohol. 

 Iso-maltose is not attacked by maltase but is hydrolysed by 

 emulsin and is therefore a j8-glucoside ; it is not fermented 



by yeast. 



It should, however, be noted that Haworth,§ who ex- 

 amined a sample of isomaltose prepared by Ling and Nanji, 

 was unable to observe any structural difference between this 

 sample and maltose itself. 



* Croft Hill : " Ber. deut. chem. Gesells.," 1901, 34. 1384- " J- Chem. 

 Soc," 1903. 83, 580. 



t Lintner and Diill : " Z. angew. Chem.," 1892, 5, 268. 

 + Ling and Nanji : " J. Chem. Soc," 1923. 123, 2681. 

 § Haworth : " J. Soc. Chem. Ind.," 1927, 46, 300 T. 



