LESSONS IN CHEMISTRY. 177 



warmth and moisture and at once the seed becomes a theater 

 of activity. Substances similar to diastase occur in the saliva 

 and other digestive fluids. 



In the manufacture of ale and beer the barley is caused to 

 germinate for a short time and then it is dried at a high tem- 

 perature which stops the germination, forming what is called 

 malt. The malt is ground and heated with water for some 

 hours, during which time the diastase formed, has converted the 

 starch into glucose and the liquid is called the wort. Yeast is 

 then added to the wort, which by the process of fermentation 

 changes some of the glucose to alcohol. 



YEAST is a fungoid plant, made up of minute cells, which con- 

 tain cellulose albuminoid matter and mineral salts. These cells 

 multiply rapidly in solutions of sugar containing albuminoid 

 and mineral substances, changing cane-sugar to grape-sugar, 

 and grape-sugar into alcohol and carbon dioxide. This decom- 

 position is called alcoholic fermentation. The changes may be 

 represented by the following equation: cane-sugar (G 12 H^flii^~ 

 H 2 0=C 12 H 24 ]2 or 2(C 6 H 12 6 ) grape-sugar, and grape-sugar, 

 C 6 H 12 6 =2(C 2 H 6 0) alcohol, +2C0 2 . 



ALCOHOL is the important ingredient in all fermented and dis- 

 tilled liquors, and is obtained from fermented liquors by distilla- 

 tion. Alcohol dissolves resins, oils and other vegetable substances, 

 and is much used in preparing medicines and varnishes. It is used 

 as a fuel and as a preservative fluid, preventing from decay ani- 

 mal or vegetable substances immersed in it. Wood spirit, or 

 methyl alcohol, is often used in place of ordinary alcohol. 



When a mixture of strong sulphuric acid and alcohol is heated 

 in a retort there distills over with water a highly volatile inflam- 

 mable liquid called ether. When ether is inhaled for a few mo- 

 ments it produces insensibility, and is extensively used in surgical 

 operations. 



When a fermented liquor is exposed to the air it gradually 



becomes sour ; the alcohol taking up oxygen is converted into 



acetic acid as follows : C 2 H 6 0-h0 2 =C 2 H 4 2 , acetic acid +H 2 0. 



The chief source of this acid is the destructive distillation of 



L. s. 12 



