Consequently, the nitrogene in ammoniac is to the hydrogene as 35: 105
in volume: and 13,3 grains of ammoniac are composed of 10,6 nitrogene,
(supposing that 100 cubic inches weigh 30,45 grains) and 2,7 hydrogene.
According to Berthollet, the weight of the nitrogene in ammoniac is to
that of the hydrogene as 121 to 29.[62] The difference between this
estimation and mine is so small as to be almost unworthy of notice, and
arises most probably from the slight difference between the accounts
of Lavoisier and Monge, of the composition of water, and the different
weights assigned to the gases employed.
[62] Journal de Physique, 1786, t. 2, 177.
We may then conclude, that 100 grains of ammoniac are composed of about
80 nitrogene, and 20 hydrogene.
The decomposition of ammoniac by heat, as well as by the electric
spark, was first discovered by Priestley. In an experiment[63] when
aëriform ammoniac was sent through a heated tube from a caustic
solution of ammoniac in water, this great discoverer observed that an
inflammable gas was produced, though in no great quantity, and that a
fluid blackened by matter, probably carbonaceous, likewise came over.
[63] Phil. Trans. vol. 79, page 294.
In my experiments the whole of the ammoniac appeared to be decomposed;
the quantity of gas generated was immense, and not clouded, as is
usually the case with gases generated at high temperatures. It is
possible, that the larger quantity of water carried over in his
experiment, by its strong attraction for ammoniac in the aëriform
state, might have, in some measure, retarded the decomposition. It
is however, more probable to suppose, that a fissure existed in the
earthen tube he employed, through which a certain quantity of gas
escaped, and coaly matter entered.
Priestley found that the metallic oxides when strongly heated,
decomposed ammoniac, the metal being revivified and water and nitrogene
produced.[64] The estimations of the composition of ammoniac that may
be deduced from his experiments on the oxide of lead, differ very
little from those already detailed.
[64] Vol. 2, page 398.