The formation and decomposition of volatile alkali in many processes,
was observed by Priestley, Scheele, Bergman, Kirwan, and Higgins; but
to Berthollet we owe the discovery of its constituent parts, and their
proportions to each other. These proportions this excellent philosopher
deduced from an experiment on the decomposition of aëriform ammoniac by
the electric spark:[60] a process in which no apparent source of error
exists.
[60] Journal de Physique, 1786. Tom. 2, pag. 176.
Since, however, his estimations have been made, the proportions of
oxygene and hydrogene in water have been more accurately determined.
This circumstance, as well as the conviction of the impossibility
of too minutely scrutinizing facts, fundamental to a great mass of
reasoning, induced me to make the following experiments.
A porcelain tube was provided, open at both ends, and well glazed
inside and outside, its diameter being about,5 inches. To one end of
this, a glass tube was affixed, curved for the purpose of communicating
with the water apparatus. With the other end a glass retort was
accurately connected, containing a mixture of perfectly caustic slacked
lime, and muriate of ammoniac.
The water in the apparatus for receiving the gases had been previously
boiled, to expel the air it might contain, and during the experiment
was yet warm.
When the tube had been reddened in a furnace adapted to the purpose,
the flame of a spirit lamp was applied to the bottom of the retort. A
great quantity of gas was collected in the water apparatus; of this the
first portions were rejected, and the last transferred to the mercurial
trough.
A small quantity examined, did not at all diminish with nitrous gas,
and burnt with a lambent white flame, in contact with common air.
2¾ of this gas, equal to 110 grain measures, were fired with 2, equal
to 80, of oxygene, in a detonating tube, by the electric spark. They
were reduced to 2¼, or 90. On introducing to the remainder a solution
of strontian, it became slightly clouded on the top, and an absorption
of some grain measures took place.
It was evident, then, that in this experiment, charcoal[61] had been
somehow present in the tube; which being dissolved by the nascent
hydrogene, had rendered it slightly carbonated, and in consequence made
the results inconclusive.
[61] Though the tube had never been used, and was apparently clean and
dry on the inside, it must have contained something in the form of
dust, capable of furnishing either hydrocarbonate, or charcoal.
A tube of thick green glass carefully made clean, was now employed,
inclosed in the porcelain tube. Every other precaution was taken to
prevent the existence of sources of error, and the experiment conducted
as before.
140 grain measures of the gas produced, fired with 120 of oxygene,
left, in two experiments, nearly 110. Solution of strontian placed in
contact with the residuum, did not become clouded, and no absorption
was perceived.
Now 150 measures of gas were destroyed, and if we take Lavoisier’s
and Meusnier’s estimation of the composition of water, and suppose
the weight of oxygene to be 35 grains, and that of hydrogene 2,6 the
hundred cubic inches; the oxygene employed will be to the hydrogene as
243 to 576. Put _x_ for the oxygene, and _y_ for the hydrogene.