418 



SMITH'S INTERMEDIATE CHEMISTRY 



The liquid extracted from the yeast cells works as well as does the 

 plant itself. 



Yeast will ferment fructose (fruit sugar, p. 401), with the same 

 result, but more slowly. 



Zymase does not act upon cane- 

 sugar (sucrose C^H^On). But the in- 

 vertase (sucrase), which is also con- 

 tained in the yeast, hydrolyzes the 

 sucrose in the same way as does a dilute 

 acid, giving invert sugar (p. 403). The 

 latter is then decomposed by the zy- 

 mase. Hence cane-sugar in solution is 

 decomposed by yeast into alcohol and 

 carbon dioxide, just as is grape-sugar, 

 only more slowly. 



In the manufacture of wines the glu- 

 FIG. 102 cose contained in the grape juice is fer- 



mented by a species of yeast always found on the skins. 



\ermentation of StarcK^ Barley, which has been allowed 

 to sprout, and is then dried, is called malt. This contains an 

 J enzyme, diastase (or amylase), which is able -to hvdrolyze starch 

 J\jnt maltose C^H^On^ (p. 401). Maltose is further hydrolyzed 

 by another enzyme, maltase, to form glucose, and the latter is 

 then decomposed by zymase into alcohol and carbon dioxide. 



Whisky is made by treating the starch of rye, maize, or barley 

 in the above way, with subsequent distillation. Beer is made 

 similarly from various kinds of grain, particularly barley, except 

 that the fermented liquid is not distilled. 



Industrial^ilcohoL ( AlcohoJJas very extensive uses, apart 

 from its historic value as abeverage. It is employed as a solvent^ 

 in making varnishes for wood and lacquers for metal, as well 

 as for plastics like celluloid, >gollodion and artificial silk (p. 399). 





