134 ReEPoRT OF THE CHEMIST OF THE 
the sugar being changed into alcohol and carbon dioxide gas. 
Theoretically, 100 parts of sugar should yield about 51 parts of 
alcohol, but in actual practice losses are experienced, reducing the 
actual yield to 45 to 47 parts of alcohol. The fresh apple juice 
from sound apples contains no alcohol. When apple juice has 
undergone partial or complete alcoholic fermentation, it is com- 
merically known as “ cider.” 
In carrying on the experiments, apple juice was placed in 
casks and also in bottles, and these were kept under different 
conditions, some approximating the conditions commonly em- 
ployed by farmers in the home-manufacture of cider vinegar. 
(1) Relation of time to formation of alcohol_——Under the ordi- 
nary conditions of a cellar temperature, most of the sugar is 
changed into alcohol in five or six months. (2) Relation of tem- 
perature to alcoholic fermentation. In studying the alcoholic 
fermentation at temperatures ranging from 45° F. to 85° F., it 
was found that the change takes place more rapidly at the higher 
temperatures. (3) Adding yeast to apple juice tends to hasten the 
alcoholic fermentation. 
4, Acetic Fermentation of Cider.—Certain forms of bacteria act 
upon the alcohol of cider and convert it into acetic acid, the 
presence of which in sufficient quantity is the object of the maker 
of vinegar. The conditions most necessary for the acetic fermen- 
tation of cider are (a) acetic bacteria, (b) an abundant supply of 
air, and (c) a temperature between 65° F. and 85° F. Theoreti- 
cally, 100 parts of alcohol yield about 130 parts of acetic acid, but 
the actual yield is usually below 120. 
(1) Relation of time to formation of acetic acid.—At cellar 
temperatures, the acetic fermentation takes place slowly, requir- 
ing about 18 months. (2) The relation of temperature to the 
acetic fermentation Under the conditions of our work the forma- 
tion of acetic acid took place most satisfactorily at temperatures 
between 65° F. and 75° F. (3) The addition of vinegar containing 
“mother ” to cider after the completion of the alcoholic fermenta- 
tion increases the rapidity of the formation of acetic acid. (4) 
When the clear portion of cider was separated from the sediment, 
the acetic fermentation appeared to be favored, especially at 
lower temperatures. 
