on the fpecific Gravities , &c. of Saline Subjlances. 227 
from common air, and that the whole diminution is owing to 
its production and abforbtion. Mr. Lavoisier has fet thefe 
points in the cleared: light. He introduced a lighted candle 
into a receiver handing on mercury : the air at firft expanded 
by reafon of the heat, and the candle was fhortly after extin- 
guifhed ; but when all was cold, there was fcarcely any dimi- 
nution. He then introduced, under the receiver, a cauftic 
fixed alkaline liquor : the air was immediately diminifhed, and 
the diminution reached nearly one-ninth of the whole. He 
then introduced a fmall quantity of vitriolic acid ; the alkali 
immediately eftervefced, gave out its fixed air, the mercury re- 
defcended, and the air in the receiver occupied the fame fpace as 
at firft ; fo that this experiment is perfedlly conclufive. He 
alfo lighted a candle in dephlogifticated air, and when it was 
extinguifhed, introduced a cauftic fixed alkaline liquor, and 
then, and only then, this air was diminifhed two-thirds, by 
which it is evident, that two-thirds of it were converted into 
fixed air ; but the remaining third was fo far from being phlo- 
gifticated air, that a candle burned in it as well as ever, and 
after it went out half of this air was, abforbed by a cauftic 
fixed alkali, and the remainder was ftill little worfe than com- 
mon air. Mem. Par. 1777, p. 195, &c. 
Yet Mr. lavoisier thinks, that by the calcination of metals 
fixed air is not produced ; but that the metals abforb the de- 
phlogifticated part of common air, and are thereby converted 
into a calx. And on this is founded his extraordinary opinion 
of the non-exiftence of phlogifton ; whereas it is evident, that 
even mercury affords inflammable air, and confequently contains 
phlogifton, and that it lofes part of this during calcination, and 
confequently fixed air muft be produced, as he himfelf acknow- 
ledges it to be during combuftion, by the union of inflam- 
r G g z mable 
