vegetable substances, and of their decomposition by the action of fire.
FOOTNOTES:
[24] Though this term, red heat, does not indicate any absolutely
determinate degree of temperature, I shall use it sometimes to express a
temperature considerably above that of boiling water.--A.
[25] I must be understood here to speak of vegetables reduced to a
perfectly dry state; and, with respect to oil, I do not mean that which
is procured by expression either in the cold, or in a temperature not
exceeding that of boiling water; I only allude to the empyreumatic oil
procured by distillation with a naked fire, in a heat superior to the
temperature of boiling water; which is the only oil declared to be
produced by the operation of fire. What I have published upon this
subject in the Memoirs of the Academy for 1786 may be consulted.--A.
CHAP. XIII.
_Of the Decomposition of Vegetable Oxyds by the Vinous Fermentation._
The manner in which wine, cyder, mead, and all the liquors formed by the
spiritous fermentation, are produced, is well known to every one. The
juice of grapes or of apples being expressed, and the latter being
diluted with water, they are put into large vats, which are kept in a
temperature of at least 10 (54.5 ) of the thermometer. A rapid
intestine motion, or fermentation, very soon takes place, numerous
globules of gas form in the liquid and burst at the surface; when the
fermentation is at its height, the quantity of gas disengaged is so
great as to make the liquor appear as if boiling violently over a fire.
When this gas is carefully gathered, it is found to be carbonic acid
perfectly pure, and free from admixture with any other species of air or
gas whatever.
When the fermentation is completed, the juice of grapes is changed from
being sweet, and full of sugar, into a vinous liquor which no longer
99