To understand accurately the changes taking place during the
decomposition of nitrate of ammoniac, we must be acquainted with the
specific gravity and composition of nitrous oxide.
90 cubic inches of it, containing about ¹/₃₅ common air, introduced
from the mercurial airholder into an exhausted globe, increased it in
weight 44,75 grains; thermometer being 51°, and atmospheric pressure
30,7.
106 cubic inches, of similar composition, weighed in like manner,
gave at the same temperature and pressure nearly 52,25 grains; and in
another experiment, when the thermometer was 41°, 53 grains.
So that accounting for the small quantity of common air contained in
the gases weighed, we may conclude, that 100 cubic inches of pure
nitrous oxide weigh 50,1 grains at temperature 50°, and atmospheric
pressure 30,7.
I was a little surprised at this great specific gravity, particularly
as I had expected, from Dr. Priestley’s observations, to find it less
heavy than atmospherical air. This philosopher supposed, from some
appearances produced by the mixture of it with aëriform ammoniac, that
it was even of less specific gravity than that gas.[81]
[81] Experiments and Observations, vol. 2, pag. 89. Last Edition.