THE CARBOHYDRATES 67 



splitting enzymes. Commercial dextrin is a sweetish, sticky amorphous 

 powder. It probably consists of many dextrins, of which two may 

 be mentioned erythrodextrin and achroodextrin. It often contain* 

 some reducing sugar. 



Erythrodextrin, or " red dextrin," as its name implies, is so called 

 because it yields a port-wine colour with iodine solution. It is 

 regarded as the first product of the hydrolysis of soluble starch. It is 

 distinguished from glycogen by giving a clear solution in hot water, 

 and requiring 80 to 85 per cent, alcohol to precipitate it from solution. 

 It is also not precipitated by basic lead acetate solutions. It requires 

 full saturation with ammonium sulphate to salt it out (see table, p. 60). 



Achroodextrin, or " colourless " dextrin, gets its name because it 

 gives no colour with iodine solution. It occurs at a later stage in the- 

 hydrolysis of starch; being of smaller molecular weight, 90 per cent, 

 alcohol is required to precipitate it from solution. The dextrins when 

 pure do not give Moore's test, Trommer's, or other reduction tests; 

 these are only given after hydrolysis to sugars has taken place. 



