The killing of yeast occurs very easily when there is no particular pains paid to it; it is a very sensitive plant, and very likely to be destroyed by too much heat or cold, salt, alcohol, sulphur, glycerine, strong acids, or alkalies. Oils are also objectionable to a certain extent, and any kind of beer made with them, like spruce, sarsa-parilla, etc., do not ferment as well as those made from vegetable extracts, and never make as good beer, for they contain nothing but a flavor, whereas in making beer from well-prepared extracts, you get the extractive matter along with the flavor, Which gives the beer substance and body; as, for instance, ale and lager beer from malt and hops, birch and root beer from roots and barks. The more body and substance the beer contains the more easily it ferments and the longer it keeps sweet and lively; and, what is still better, more saleable.

Arresting Fermentation

It is often of the utmost importance to bottlers, brewers, wine merchants, druggists, etc., to be able to lessen the activity of the vinous fermentation, or to stop it altogether. Among the simplest means of effecting this object, and such as admit of easy practical application, may be mentioned exposure to either cold or heat. At a temperature below about 50° F., the acetous fermentation is suspended, and the alcoholic fermentation proceeds with diminished activity as the temperature falls, until at about 38° F. it ceases altogether. In like manner, the rapid increase of the temperature of a fermenting liquid arrests its fermentation, and is preferable to the action of cold, as it is of easier application, and perfectly precipitates the ferment in an inert state. For this purpose a heat of about 180° Fahrenheit is sufficient; but even that of boiling water may be employed with advantage. In practice fluids are commonly raised to their boiling point for this purpose, or they are submitted to the heat of a water-bath (207 1/2o F.). In this way the fermentation of syrups and saccharine solutions is commonly arrested in the bottlers' laboratory.