THE DISACCHARIDES. 



ii 



Maltose reduces copper, bismuth, and other metallic salts in alkaline 

 solutions, but its reducing power as measured by Fehling's solution is 

 about one-third less than that of dextrose. 1 It does not reduce Barfoed's 

 reagent 2 as dextrose does. It ferments readily with yeast. With 

 phenylhydrazine, phenylmaltosazone is formed (C 24 H 32 N 4 9 ) ; this crystal- 

 lises in yellow needles much broader than those yielded by dextrose or 

 lactose; it melts at 206 C. Unlike phenylglucosazone, it dissolves 

 in seventy-five parts of boiling water, and is still more soluble in hot 

 alcohol (Fig. 2). 



FIG. 2. Crystals of phenylmaltosazone. 



Isomaltose 3 is a sugar formed at the same time as maltose by the 

 action of either diastase, ptyalin, or amylopsin 4 on starch. It is also an 



1 Tenc.c. of Fehling solution corresponds to - 05 grms. of dextrose, levulose, orgalactose, 

 and to 0*07196 of maltose. 



2 13*3 grms. of cupric acetate are dissolved in 200 c.c. of water; to . this solution, 

 6 c.c. of acetic acid containing 38 per cent, of glacial acetic acid are added (Barfoed, 

 "Organic Analysis," p. 254). 



3 Originally described by Fischer, Ber. d. deutsch. diem. Gcsellsch., Berlin, Bd. xxiii. 

 S. 3687. Fischer's observations, which have been called in question by some chemists, have 

 been veiy generally confirmed. In his most recent paper on the subject, ibid., 1896, Bd. 

 xxvii. S. 3024, he shows that isomaltose is not directly fermentable by yeast, and so may be 

 separated from maltose. Its osazone is soluble in four parts of hot water, while that from 

 maltose requires seventy-five parts. 



4 Klilz and Vogel, Ztschr.f. BioL, Miinchen, Bd. xxxi. 



