a measure of the relative quantities of caloric disengaged. Mr de la
Place and I gave a description of the apparatus employed for this kind
of experiment in the Memoirs of the Academy for 1780, p. 355; and a
description and plate of the same apparatus will be found in the third
part of this work. With this apparatus, phosphorus, charcoal, and
hydrogen gas, gave the following results:
One pound of phosphorus melted 100 libs. of ice.
One pound of charcoal melted 96 libs. 8 oz.
One pound of hydrogen gas melted 295 libs. 9 oz. 3-1/2 gros.
As a concrete acid is formed by the combustion of phosphorus, it is
probable that very little caloric remains in the acid, and,
consequently, that the above experiment gives us very nearly the whole
quantity of caloric contained in the oxygen gas. Even if we suppose the
phosphoric acid to contain a good deal of caloric, yet, as the
phosphorus must have contained nearly an equal quantity before
combustion, the error must be very small, as it will only consist of the
difference between what was contained in the phosphorus before, and in
the phosphoric acid after combustion.
I have already shown in Chap. V. that one pound of phosphorus absorbs
one pound eight ounces of oxygen during combustion; and since, by the
same operation, 100 lib. of ice are melted, it follows, that the
quantity of caloric contained in one pound of oxygen gas is capable of
melting 66 libs. 10 oz. 5 gros 24 grs. of ice.
One pound of charcoal during combustion melts only 96 libs. 8 oz. of
ice, whilst it absorbs 2 libs. 9 oz. 1 gros 10 grs. of oxygen.
By the experiment with phosphorus, this quantity of oxygen gas ought to
disengage a quantity of caloric sufficient to melt 171 libs. 6 oz. 5
gros of ice; consequently, during this experiment, a quantity of
caloric, sufficient to melt 74 libs. 14 oz. 5 gros of ice
disappears. Carbonic acid is not, like phosphoric acid, in a concrete
state after combustion but in the state of gas, and requires to be
united with caloric to enable it to subsist in that state; the quantity
of caloric missing in the last experiment is evidently employed for that
purpose. When we divide that quantity by the weight of carbonic acid,
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