io The Colorado Experiment Station 
vert only a small part of the sugar into alcohol, while others act 
so slowly that they are impracticable. Inasmuch as the percentage 
of acetic acid in the vinegar depends directly upon the amount of 
alcohol produced, it is very essential to secure as large a yield of 
alcohol as possible from the sugar present. This means convert¬ 
ing all of the sugar into alcohol in the shortest time possible. The 
most satisfactory way of doing this is to add one cake of com¬ 
pressed yeast, stirred up in a little cooled, boiled water, to each 
five gallons of sweet cider. In place of this, one quart of liquid 
wine yeast, propagated from a pure culture, may be used for each 
thirty gallons of cider. 
During the alcoholic fermentation, the cider should be kept 
at a temperature of 65 to 80 degrees F. Here is where many make 
the very serious mistake of putting their fresh cider into a cool 
cellar where the fermentation takes place entirely too slowly. If 
the cider is made in the fall, the barrels should be left out of doors 
for a while on the protected, sunny side of a building and kept 
warm, unless a regular vinegar-cellar, artificially heated, is at hand. 
If yeast is added and the proper temperature is maintained, 
the alcoholic fermentation should be completed in six weeks to 
three months in place of seven to ten months as in the old-fashioned 
way. Experiments along this line have shown that when yeast is 
added and a temperature of 70 degrees F. is held, the cider at the 
end of one month contained 7.25 per cent, of alcohol as against 
.11 per cent, when no yeast was used and the temperature was be¬ 
tween 45 and 55 degrees F. Cider kept in a cellar at 45 to 55 
degrees with no yeast added required seven months to make 6.79 
per cent, of alcohol. 
Temperature, alone, is an important factor as shown by an 
experiment wherein cider to which no yeast was added was held 
for three months at 70 degrees F. and yielded 6.41 per cent, of 
alcohol. 
There is no question but that the time required for completing 
the alcoholic fermentation can be reduced at least one-half by 
adding yeast and by maintaining the proper temperatures. By 
hastening this operation, the loss of alcohol by evaporation is re¬ 
duced, and the acetic fermentation can be started that much sooner. 
Theoretically, 100 parts of sugar should give 51 parts of alco¬ 
hol and 49 parts of carbon dioxide gas. This figure has been 
shown by Browne to be a little high. In actual practice, 45-47 
parts of alcohol from 100 parts of sugar is a fair average. 
But why not add “mother” or vinegar to sweet cider or put 
