arths Carburet of potash, &c. Unknown.

SECT. X.--_Observations upon Charcoal, and its Combinations with Simple
Substances._

As charcoal has not been hitherto decomposed, it must, in the present
state of our knowledge, be considered as a simple substance. By modern
experiments it appears to exist ready formed in vegetables; and I have
already remarked, that, in these, it is combined with hydrogen,
sometimes with azote and phosphorus, forming compound radicals, which
may be changed into oxyds or acids according to their degree of
oxygenation.

To obtain the charcoal contained in vegetable or animal substances, we
subject them to the action of fire, at first moderate, and afterwards
very strong, on purpose to drive off the last portions of water, which
adhere very obstinately to the charcoal. For chemical purposes, this is
usually done in retorts of stone-ware or porcellain, into which the
wood, or other matter, is introduced, and then placed in a reverberatory
furnace, raised gradually to its greatest heat: The heat volatilizes, or
changes into gas, all the parts of the body susceptible of combining
with caloric into that form, and the charcoal, being more fixed in its
nature, remains in the retort combined with a little earth and some
fixed salts.

In the business of charring wood, this is done by a less expensive
process. The wood is disposed in heaps, and covered with earth, so as to
prevent the access of any more air than is absolutely necessary for
supporting the fire, which is kept up till all the water and oil is
driven off, after which the fire is extinguished by shutting up all the
air-holes.

We may analyse charcoal either by combustion in air, or rather in oxygen
gas, or by means of nitric acid. In either case we convert it into
carbonic acid, and sometimes a little potash and some neutral salts
remain. This analysis has hitherto been but little attended to by
chemists; and we are not even certain if potash exists in charcoal
before combustion, or whether it be formed by means of some unknown
combination during that process.

SECT. XI.--_Observations upon the Muriatic, Fluoric, and Boracic
Radicals, and their Combinations._

As the combinations of these substances, either with each other, or with
the other combustible bodies, are hitherto entirely unknown, we have
not attempted to form any table for their nomenclature. We only know
that these radicals are susceptible of oxygenation, and of fo