lime water into the flask and dealt with it by shaking, as already
explained, and observed that the sixth part of all the air had been lost
in consequence of the combustion. The lime water was not in the least
precipitated in this case, an indication that sulphur gives out no
aerial acid during its combustion, but another substance somewhat
resembling air; this is the volatile acid of sulphur, which occupies
again the empty space produced by the union of the inflammable substance
with air. It is not, as may be seen, a trifling circumstance that
phlogiston, whether it separates itself from substances and enters into
union with air, with or without a fiery motion, still in every case
diminishes the air so considerably in its external bulk.

+24. Experiments which prove that ordinary air, consisting of two kinds
of elastic fluids, can be compounded again after these have been
separated from each other by means of phlogiston.+

I have already stated in Sec. 16 that I was not able to find again the lost
air. One might indeed object, that the lost air still remains in the
residual air which can no more unite with phlogiston; for, since I have
found that it is lighter than ordinary air, it might be believed that
the phlogiston united with this air makes it lighter, as appears to be
known already from other experiments. But since phlogiston is a
substance, which always presupposes some weight, I much doubt whether
such hypothesis has any foundation....

+25.+ How often must not chemists have distilled the fuming acid of
nitre from oil of vitriol and nitre, when it is impossible that they
should not have observed how this acid went over red in the beginning,
white and colourless in the middle of the distillation, but at the end
red again; and indeed so dark-red that one could not see through the
receiver? It is to be noticed here that if the heat is permitted to
increase too much at the end of the distillation, the whole mixture
enters into such frothing that everything goes over into the receiver;
and, what is of the greatest importance, a kind of air goes over during
this frothing which deserves no small attention. If one takes for such
distillation a very black oil of vitriol, not only does the acid go over
at the beginning of a far darker red than when one takes a white oil of
vitriol, but further, when one introduces a burning candle into the
receiver after about an ounce has gone over, this goes out immediately.
On