The nitrous oxide may be analised, either by charcoal or hydrogene;
during the combustion of other bodies in it, small portions of nitrous
acid are generally formed, as will be fully explained hereafter.
The gas that I employed was generated from compact nitrate of ammoniac,
and was in its highest state of purity, as it left a residuum of ¹/₃₈
only, when absorbed by boiled water.
10 cubic inches of it were inserted into a jar graduated to,1 cubic
inches, containing dry mercury. Through this mercury a piece of
charcoal which had been deprived of its hydrogene by long exposure
to heat, weighing about a grain, was introduced, while yet warm. No
perceptible absorption of the gas took place.[82]
[82] A minute quantity, however, must have been absorbed, and given out
again when the charcoal was heated.
Thermometer being 46°, the focus of a lens was thrown on the charcoal,
which instantly took fire, and burnt vividly for about a minute, the
gas being increased in volume. After the vivid combustion had ceased,
the focus was again thrown on the charcoal; it continued to burn for
near ten minutes, when the process stopped.
The gas, when the original pressure and temperature were restored,
filled a space equal to 12,5 cubic inches.
On introducing to it a small quantity of strong solution of
ammoniac[83], white vapor was instantly perceived, and after a short
time the reduction was to about 10,1 cubic inches; so that apparently,
2,4 cubic inches of carbonic acid had been formed. The 10,1 cubic
inches of gas remaining were exposed to water which had been long in
ebullition, and which was introduced whilst boiling, under mercury.
After the absorption of the nitrous oxide by the water, the gas
remaining was equal to 5,3.
[83] Strong solution of ammoniac has no attraction for nitrous oxide.
But on combining a cubic inch of pure nitrous oxide with some of the
same water, which had been received under mercury in a separate vessel,
nearly ¹/₂₂ remained. Consequently we may conclude, that 5,1 of a gas
unabsorbable by water, was produced in the combustion.
This gas extinguished flame, gave no diminution with oxygene, and the
slightest possible with nitrous gas. When an electric spark was passed
through it, mingled with oxygene; no inflammation, or _perceptible_
diminution took place.[84] We may consequently conclude that it was
nitrogene, mingled with a minute portion of common air, expelled from
the water.
[84] The gas was examined by those tests in order to prove that no
water had been decomposed.
The charcoal was diminished in bulk to one half nearly, but the loss of
weight could not be ascertained, as its pores were filled with mercury.
Now 5 cubic inches of nitrous oxide were absorbed by the water,
consequently 5 were decompounded by the charcoal; and these produced
5,1 cubic inches of nitrogene; and by giving their oxygene to the
charcoal, apparently 2,4 of carbonic acid.
But 5 cubic inches of nitrous oxide weigh 2,5 grains, and 5,1 cubic
inches of nitrogene 1,55; then 2,5-1,55 =,95.
So that reasoning from the relative specific gravities of nitrogene and
nitrous oxide, 2,5 grains of the last are composed of 1,55 nitrogene,
and,95 oxygene.
But from many experiments made on the specific gravity of carbonic
acid, in August, 1799, I concluded that 100 cubic inches of it weighed
47,5 grains, thermometer being 60,1°, and barometer 29,5. Consequently,
making the necessary corrections, 2,4 cubic inches of it weigh
1,14 grains; and on Lavoisier’s and Guyton’s[85] estimation of its
composition, these 1,13 grains contain 8,2 of oxygene.
[85] See the curious paper of this excellent philosopher, on the
combustion of the diamond, in which he proves that charcoal is, in
fact, oxide of diamond. Annales de Chimie, xxxi.
So that, drawing conclusions from the quantity of carbonic acid formed
in this experiment, 2,5 grains of nitrous oxide will be composed of,82
oxygene, and 1,68 nitrogene.
The difference between these estimations is considerable, and yet not
more than might have been expected, if we consider the probable sources
of error in the experiment.
1. It is likely that variable minute quantities of hydrogene remain
combined with charcoal, even after it has been long exposed to a red
heat.
2. It is probable that the nitrogene and carbonic acid produced were
capable of dissolving more water than that held in solution by the
nitrous oxide; and if so, they were more condensed than if saturated
with moisture, and hence the quantity of carbonic acid under-rated.
We may consequently suppose the estimation founded on the quantity of
nitrogene evolved, most correct; and making a small allowance for the
difference, conclude, that 100 grains of nitrous oxide are composed of
about 37 oxygene, and 63 nitrogene; existing in a much more condensed
state than when in their simple forms.
The tolerable accuracy of this statement will be hereafter demonstrated
by a number of experiments on the combustion of different bodies in
nitrous oxide, detailed in Research II.