FERMENTATION. 269 



and as this air expands, it presses the 

 liquid down, which causes effervescence. 



Q. What produces the FROTH of BOTTLED 

 PORTER ? 



A. The carbonic acid gas, produced 

 by its vinous fermentation; which is 

 absorbed by the liquor so long as the 

 bottle is well corked, but is given off in 

 froth as soon as the pressure of the cork 

 is removed. 



Q. What gives the pleasant ACID taste to soda 

 water, ginger beer, champagne, and cider ? 



A. The presence of carbonic acid,, 

 generated by fermentation, and liberated 

 by effervescence when the pressure of 

 the cork is removed. 



Q. Why does fresh SPRING WATER SPARKLE, 

 when poured from one vessel to another ? 



A. Because fresh spring and pump 

 water contain carbonic acid ; and it is the 

 presence of this gas which makes the 

 water sparkle. - 



Q. What is the FERMENTATION of BEEB and 

 WINE? 



A. The production of carbonic acid 

 gas and al'cohol. 



A a 3 



