the other hand, when one places a burning candle in the receiver
filled with blood-red vapours, towards the end of the distillation when,
as has been said, the mixture froths strongly, not only will it continue
to burn, but this will take place with a much brighter light than in
ordinary air. The same thing occurs when one attaches, at the close of
the distillation, a receiver which is filled with an air in which fire
will not burn, for, when this has been attached for half an hour, a
candle will likewise continue to burn in the air.

In this case there now arises in the first place the question: Are the
vapours of the acid of nitre naturally red? I beg leave to raise this
question here because I believe there are people who advance the redness
of this acid as a distinguishing characteristic. The colours of the acid
of nitre are accidental. When a few ounces of fuming acid of nitre are
distilled by a very gentle heat, the yellow separates itself from it and
goes into the receiver, and the residuum in the retort becomes white
and colourless like water. This acid has all the chief properties of
acid of nitre, except that the yellow colour is wanting. This I call the
pure acid of nitre; as soon, however, as it comes into contact with an
inflammable substance, it becomes more or less red. This red acid is
more volatile than the pure, hence heat alone can separate them from one
another; and, for exactly the same reason, the volatile spirit must go
over first in the distillation of Glauber's spirit of nitre. When this
has gone over, the colourless acid follows; but why does the acid make
its appearance again so blood-red at the end of the distillation? Why
has not this redness already been driven over at the beginning? Where
does it now obtain its phlogiston? This is the difficulty.

+26.+ I intimated in the preceding paragraph that the candle went out in
the receiver at the beginning of the distillation. The reason is to be
found in the experiment which I have cited in Sec. 13. In this case the
acid of nitre, passing over in vapours, takes to itself the inflammable
substance, whose presence is indicated by the black colour of the oil of
vitriol; as soon as this has taken place it meets with the air, which
again robs the now phlogisticated acid of its inflammable substance; by
this means a part of the air contained in the receiver becomes lost,
hence the fire introduced into it must go out (Sec. 15).

+27.+ The acid of n