I placed some newly made pyrophorus, about as much as would fill
a quarter of a cubic inch, in a jar filled with dry mercury, and
introduced to it, four cubic inches of nitrous gas, procured from
mercury and nitric acid.
It instantly took fire and burnt with great vividness for some moments.
After the combustion had ceased, the gas was diminished about three
quarters of a cubic inch. The remainder was not examined; for the
diminution appeared to go on for some time, after; in an half hour,
when it was compleat, it was to 2 cubic inches. A taper, introduced
into these, burnt with an enlarged flame, blue at the edges; from
whence it appeared, that they were composed of nitrogene and nitrous
oxide.
I now introduced about half a cubic inch of pyrophorus to two cubic
inches of nitrous gas; the combustion took place, and the gas was
rapidly diminished to one half; and on suffering it to remain five
minutes to one third nearly; which extinguished flame.
Suspecting that this great diminution was owing to the absorption of
some of the nitrogene formed, by the charcoal of the pyrophorus, I
carefully made a quantity of pyrophorus; employing more than two thirds
of alumn, to one third of sugar.
To rather more than half of a cubic inch of this, two cubic inches of
nitrous gas, which contained about ¹/₄₀ nitrogene, were admitted. After
the combustion, the gas remaining, _apparently_ filled a space equal
to 1,2 cubic inches; but, as on account of the burnt pyrophyrus in the
jar, it was impossible to ascertain the volume with nicety, it was
carefully and wholly transferred into another jar. It filled a space
equal to 1,15 cubic inches nearly.
When water was admitted to this gas no absorption took place. It
underwent no diminution with nitrous gas, and a taper plunged into it
was instantly extinguished. We may consequently conclude that it was
nitrogene.
Now 2 cubic inches of nitrous gas weigh,686 grains, and 1,1 of
nitrogene—,05, the quantity previously contained in the gas = to 1,05,
3,19. Hence,686 of nitrous gas would be composed of,367 oxygene, and
,319 nitrogene; and 100 grains would contain 53,4 oxygene, and 46,6
nitrogene.
IV. _Additional observations on the combustion of bodies in Nitrous
Gas, and on its Composition._
Though phosphorus may be fused, and even sublimed, in nitrous gas,
without producing the slightest luminous appearance,[103] yet when it
is introduced into it in a state of active inflammation, it burns
with almost as much vividness as in oxygene.[104] Hence it is evident,
that at the heat of ignition, phosphorus is capable of attracting the
oxygene from the nitrogene of nitrous gas.
[103] No luminous appearance is produced when phosphorus is introduced
into _pure_ nitrous gas. It has been often observed, that phosphorus is
luminous in nitrous gas, that has not been long in contact with water
after its production. This phænomenon, I suspect, depends either on the
decomposition of the nitric acid held in solution by the nitrous gas;
or on the combination of the phosphorus with oxygene loosely adhering
to the binary aëriform compound of nitric acid and nitrous gas. I have
not yet examined if nitrous gas can be converted into nitrous oxide by
long exposure to heated phosphorus: it appears, however, very probable.
[104] Perhaps this fact has been noticed before; I have not, however,
met with it in any chemical work.
I attempted to analise nitrous gas, by introducing into a known
quantity of it, confined by mercury, phosphorus, in a vessel containing
a minute quantity of oxygene.[105] The phosphorus was inflamed with
an ignited iron wire, by which, at the moment of the combustion, the
vessel containing it was raised from the mercury into the nitrous gas.
But after making in this way, five of six unsuccessful experiments, I
desisted. When the communication between the vessels was made before
the oxygene was nearly combined with the phosphorus, nitrous acid
was formed, which instantly destroyed the combustion; when, on the
contrary, the phosphorus was suffered to consume almost the whole
of the oxygene, it was not sufficiently ignited when introduced, to
decompose the nitrous gas.
[105] This mode of inflaming bodies in gases, not capable of supporting
combustion at low temperatures, will be particularly described
hereafter.
In one experiment, indeed, the phosphorus burnt for a moment in the
nitrous gas; the diminution however was slight, and not more than ¼ of
it was decomposed.
Sulphur, introduced in a state of vivid inflammation, into nitrous gas,
was instantly extinguished.
I passed a strong electric shock through equal parts of hydrogene
and nitrous gas, confined by mercury in a detonating tube; but no
inflammation, or perceptible diminution, was produced.
19,2 grain measures of hydrogene were fired by the electric shock,
with 10 of nitrous oxide, and 6 of nitrous gas; the diminution was
to 17; and pale green sulphate of iron admitted to the residuum, was
not discolored. Consequently the nitrous gas was decomposed by the
hydrogene, and as will be hereafter more clearly understood, nearly as
much nitrogene furnished by it, as would have been produced from half
the quantity of nitrous oxide.
Suspecting that phosphorated hydrogene might inflame with nitrous
gas, I passed the electric spark through 1 measure of phosphorated
hydrogene, and 4 of nitrous gas; but no diminution was perceptible. I
likewise passed the electric spark through 1 of nitrous gas, with 2 of
phosphorated hydrogene, without inflammation.
Perhaps if I had tried many other different proportions of the gases, I
should have at last discovered one, in which they would have inflamed;
for, as will be seen hereafter, nitrous oxide cannot be decomposed by
the compound combustible gases, except definite quantities are employed.
From Dr. Priestley’s experiments on iron and pyrophorus, and from the
experiments I have detailed, on charcoal, phosphorus, and hydrogene,
it appears that at certain temperatures, nitrous gas is decomposable
by most of the combustible bodies: even the extinction of sulphur, when
introduced into it in a state of inflammation, depends perhaps, on the
smaller quantity of heat produced by the combustion of this body, than
that of most others.
The analysis of nitrous gas by charcoal, as affording data for
determining immediately the quantities of oxygene and nitrogene,
ought to be considered as most accurate; and correcting it by mean
calculations derived from the decomposition of nitrous gas by
pyrophorus and hydrogene, and its conversion into nitrous oxide, a
process to be described hereafter, we may conclude, that 100 grains
of nitrous gas are composed of 55,95 oxygene, and 44,05 nitrogene; or
taking away decimals, of 56 oxygene, and 44 nitrogene.
This estimation will agree very well with the mean proportions that
would be given from Dr. Priestley’s experiments on the decomposition
of nitrous gas by iron; but as he never ascertained the purity of his
nitrous gas,[106] and probably employed different kinds in different
experiments, it is impossible to fix on any one, from which accurate
conclusions can be drawn.
Lavoisier’s estimation of the quantities of oxygene and nitrogene
entering into the composition of nitrous gas, has been generally
adopted. He supposes 64 parts of nitrous gas to be composed of 43½ of
oxygene, and 20½ of nitrogene.[107]
[106] Elements English Trans. edit. i. pag. 216.
[107] Experiments and Observations, Vol. II. pag. 40, 2d. Ed.
The difference between this account and mine is very great indeed;
but I have already, in Division 1st, pointed out sources of error in
the experiments of this great man, on the decomposition of nitre by
charcoal; which experiments were fundamental, both to his accounts of
the constitution of nitrous acid, and nitrous gas.