It has been noticed by different experimentalists, that the taper burns
with a flame considerably enlarged in nitrous oxide: sometimes with a
vivid light and crackling noise, as in oxygene; at other times with a
white central flame, surrounded by a feeble blue one.
My experiments on the combustion of the taper in nitrous oxide, were
chiefly made with a view to ascertain the cause of the double flame.
When the inflamed taper is introduced into pure nitrous oxide, it burns
at first with a brilliant white light, and sparkles as in oxygene. As
the combustion goes on, the brilliancy of the flame diminishes; it
gradually lengthens, and becomes surrounded with a pale blue cone of
light, from the apex of which much unburnt charcoal is thrown off,
in the form of smoke. The flame continues double to the end of the
process.
When the residual gases are examined after combustion, much nitrous
acid is found suspended in them; and they are composed of carbonic
acid, nitrogene, and about one fourth of undecompounded nitrous oxide.
The double flame depends upon the nitrous acid formed by the ignition;
for it can be produced by plunging the taper into common air containing
nitrous acid vapor, or into a mixture of nitrous oxide and nitrogene,
through which nitrous acid has been diffused. It is never perceived in
the combustion of the taper, till much nitrous acid is formed.
In attempting to respire some residual gas of nitrous oxide, in which
a taper had burnt out, I found it so highly impregnated with nitrous
acid, as to disable me from even taking it into my mouth.
The taper burns in a mixture of equal parts nitrous oxide and
nitrogene, at first with a flame nearly the same as that of a candle in
common air; white. Before its extinction the interior white flame, and
exterior blue flame, are perceived.
The taper is instantly extinguished in a mixture of one fourth nitrous
oxide, and three fourths nitrogene.
In a mixture of equal parts nitrous oxide and nitrous gas, the taper
burns at first with nearly as much brilliancy as in pure nitrous oxide;
gradually the double and feeble flame is produced.