FERMENTATION. 159 



"wliich have a strong affinity for water, pure alcohol 

 may be obtained ; it is much lighter than water, and 

 boils at a lower temperature than that liquid. Alco- 

 hol consists of carbon, oxygen, and hydrogen ; but 

 contains in proportion less carbon, and much less 

 oxygen, than starch or sugar do. 



369. In expressing the composition of starch, 

 sugar, and the other principles of plants, the propor- 

 tion of the different elements, per cent., has been 

 given ; for some reasons, however, it is more conveni- 

 ent to calculate the number of equivalents of each 

 constituent ; and this is not difficult to do when the 

 composition of the substance is once known. 



370. For example : ten thousand parts of sugar is 

 found to consist of carbon 4198, hydrogen 643, and 

 oxygen 5159 : now, the equivalents or combining 

 weights of these three elements are respectively 6, 1, 

 and 8. If, then, we divide the numbers just given 

 by these combining weights, we shall obtain 699 

 equivalents of carbon, 643 of hydrogen, and 644 of 

 oxygen ; and on equally reducing these, so as to ob- 

 tain the lowest number of equivalents, preserving this 

 ratio, we shall at last find that sugar consists of 12 

 equivalents of carbon, 11 of hydrogen, and 11 of 

 oxygen. 



371. This mode of stating the composition of a 

 substance, is very convenient in explaining the various 

 transformations which organic matter undergoes. 

 When a solution of sugar begins to ferment, the first 

 thing is, that the cane sugar passes into the state of 



