he volatile oils, containing a just proportion of these
two constituent ingredients, are not liable to be decomposed by that
heat, but, uniting with caloric into the gasseous state, pass over in
distillation unchanged.

In the Memoirs of the Academy for 1784, p. 593. I gave an account of my
experiments upon the composition of oil and alkohol, by the union of
hydrogen with charcoal, and of their combination with oxygen. By these
experiments, it appears that fixed oils combine with oxygen during
combustion, and are thereby converted into water and carbonic acid. By
means of calculation applied to the products of these experiments, we
find that fixed oil is composed of 21 parts, by weight, of hydrogen
combined with 79 parts of charcoal. Perhaps the solid substances of an
oily nature, such as wax, contain a proportion of oxygen, to which they
owe their state of solidity. I am at present engaged in a series of
experiments, which I hope will throw great light upon this subject.

It is worthy of being examined, whether hydrogen in its concrete state,
uncombined with caloric, be susceptible of combination with sulphur,
phosphorus, and the metals. There is nothing that we know of, which, _a
priori_, should render these combinations impossible; for combustible
bodies being in general susceptible of combination with each other,
there is no evident reason for hydrogen being an exception to the rule:
However, no direct experiment as yet establishes either the possibility
or impossibility of this union. Iron and zinc are the most likely, of
all the metals, for entering into combination with hydrogen; but, as
these have the property of decomposing water, and as it is very
difficult to get entirely free from moisture in chemical experiments, it
is hardly possible to determine whether the small portions of hydrogen
gas, obtained in certain experiments with these metals, were previously
combined with the metal in the state of solid hydrogen, or if they were
produced by the decomposition of a minute quantity of water. The more
care we take to prevent the presence of water in these experiments, the
less is the quantity of hydrogen gas procured; and, when very accurate
precautions are employed, even that quantity becomes hardly sensible.

However this inquiry may turn out respecting the power of combustible
bodies, as sulphur, phosphorus, and metals, to absorb hydrogen, we are
certain that they only absorb a very small portion; and that th