With respect to minerals properly so called, (that is, excluding such vegetable and animal substances as may have lain long buried in the earth), they are not subject to any Fermentation; at least, that our senses can perceive.
There are three sorts of Fermentation, distinguished from one another by their several productions. The first produces wines and spirituous liquors; for which reason it is called the Vinous or Spirituous Fermentation: the result of the second is an acid liquor; and therefore it is called the Acetous Fermentation: and the third generates an alkaline salt; which, however, differs from the alkaline salts hitherto treated of, in this respect chiefly, that, instead of being fixed, it is extremely volatile: this last sort takes the name of the Putrid or Putrefactive Fermentation. We shall now consider these three sorts of Fermentation and their effects a little more particularly.
These three sorts of Fermentation may take place successively in the same subject; which proves them to be only three different degrees of fermentation, all proceeding from one and the same cause, rather than three distinct fermentations. These degrees of fermentation always follow the order in which we have here placed them.
[CHAP. XIII.]
Of the Spirituous Fermentation.
The juices of almost all fruits, all saccharine vegetable matters, all farinaceous seeds and grains of every kind, being diluted with a sufficient quantity of water, are proper subjects of Spirituous Fermentation. If such liquors be exposed, in vessels slightly stopped, to a moderate degree of heat, they begin in some time to grow turbid; there arises insensibly a small commotion among their parts, attended with a hissing noise; this by little and little increases, till the grosser parts appear, like little seeds or grains, moving to and fro, agitated among themselves, and thrown up to the surface. At the same time some air bubbles rise, and the liquor acquires a pungent, penetrating smell, occasioned by the very subtile vapours which exhale from it.
These vapours have never yet been collected, in order to examine their nature; and they are known only by their noxious effects. They are so actively pernicious, that if a man comes rashly into a close place, where large quantities of liquors are fermenting, he suddenly drops down and expires, as if he were knocked on the head.
When these several phenomena, begin to go off, it is proper to stop the fermentation, if a very spirituous liquor be required: for if it be suffered to continue longer, the liquor will become acid, and from thence proceed to its last stage, that is, to putrefaction. This is done by stopping the containing vessels very close, and removing them into a cooler place. Then the impurities precipitate, and settling at the bottom leave the liquor clear and transparent: and now the palate discovers that the sweet saccharine taste it had before fermentation is changed to an agreeable pungency, which is not acid.
Liquors thus fermented are in general called Wines: for though in common life that word properly signifies the fermented juice of grapes only, and particular names are given to the fermented juices of other vegetable substances; as that obtained from Apples is called Cyder; that made from malt is called Beer: yet in Chymistry it is of use to have one general term denoting every liquor that has undergone this first degree of fermentation.