_ammoniac_. The results obtained by analysing animal matters, by
different processes, leave no room for doubt with regard to the
constituent elements of ammoniac; whenever the azote has been previously
separated from these substances, no ammoniac is produced; and in all
cases they furnish ammoniac only in proportion to the azote they
contain. This composition of ammoniac is likewise fully proved by Mr
Berthollet, in the Memoirs of the Academy for 1785, p. 316. where he
gives a variety of analytical processes by which ammoniac is decomposed,
and its two elements, azote and hydrogen, procured separately.
I already mentioned in Chap. X. that almost all combustible bodies were
capable of combining with each other; hydrogen gas possesses this
quality in an eminent degree, it dissolves charcoal, sulphur, and
phosphorus, producing the compounds named _carbonated hydrogen gas_,
_sulphurated hydrogen gas_, and _phosphorated hydrogen gas_. The two
latter of these gasses have a peculiarly disagreeable flavour; the
sulphurated hydrogen gas has a strong resemblance to the smell of rotten
eggs, and the phosphorated smells exactly like putrid fish. Ammoniac has
likewise a peculiar odour, not less penetrating, or less disagreeable,
than these other gasses. From the mixture of these different flavours
proceeds the fetor which accompanies the putrefaction of animal
substances. Sometimes ammoniac predominates, which is easily perceived
by its sharpness upon the eyes; sometimes, as in feculent matters, the
sulphurated gas is most prevalent; and sometimes, as in putrid herrings,
the phosphorated hydrogen gas is most abundant.
I long supposed that nothing could derange or interrupt the course of
putrefaction; but Mr Fourcroy and Mr Thouret have observed some peculiar
phenomena in dead bodies, buried at a certain depth, and preserved to a
certain degree, from contact with air; having found the muscular flesh
frequently converted into true animal fat. This must have arisen from
the disengagement of the azote, naturally contained in the animal
substance, by some unknown cause, leaving only the hydrogen and charcoal
remaining, which are the elements proper for producing fat or oil. This
observation upon the possibility of converting animal substances into
fat may some time or other lead to discoveries of great importance to
society. The faeces of animals, and other excrementitious matters, are
chiefly composed of charcoal and hydrogen, and approach considerably to
the nature of oil, of which they furnish a considerable quantity by
distillation with a naked fire; but the intolerable foetor which
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