A boiling heat instantly stops fermentation, by killing the ferment. To check fermentation we may remove the yeast by filtration. Too much sugar is unfavorable to fermentation, the best strength for the syrup is ten parts of water to one of sugar. In brewing the sacharine matter is extracted from the malt during the mashing. In wine making there is sufficient albuminous matter in the grape to cause fermentation without the use of yeast.
Distillation separates the alcohol in great part from the water.
Alcohol boils at 179 Fahr., and water at 212 . It is not possible, however, to separate entirely alcohol and water by distillation. Weak fermented liquors will become sour on exposure to the air. This change is due to the absorption of the oxygen of the air and is much promoted by the presence of a peculiar plant, the mother of vinegar. It is sometimes called the acetous fermentation.