221 
on the fpecific Gravities , &c. of Saline Subfrances. 
{liver, and filver by gold, from the a&ion of their refpefHve 
menftruums ; and this is the reafon why, in fome phlogiftic 
procefles, the diminution is greater than mothers; and why 
the diminution continues to increafe (lowly for a long time. 
Nor is the fuppofttion, that common air confifts of two 
fluids, one phlogifticated and the other dephlogiflicated, gra- 
tuitous ; it is pointed out hy feveral experiments. If a mix- 
ture be made of three parts phlogifticated air and one of de- 
phlogiflicated air, fl will exadlly perform the fun&ions of 
common air ; a candle will burn in it, an animal will live in it, 
juft as in common air *. Befides, common air may in fome 
meafure be feparated into thefe conftituent parts by lying over 
pure water; for dephlogiflicated air is much more mifcible 
with water than common air, as Mr. fontana remarked, 
Phil Tranf. 1779, p- 443* and 444 and scheele on Fire, 
§ 94. Hence, if common air be fuffered to ftand fome time 
over pure water, it will be diminifhed, the purer part being in 
great meafure abforbed by the water, and the remainder will be- 
found to confift of fo large a proportion of phlogifticated air 
that a candle will not burn in it. 1 pr. 158. 4 pr. 353.' Mr.' 
scheele again expelled that part which the water had abforbed,' 
and found it dephlogiflicated. He alfo found* that phlogifti- - 
cated air is not at all abforbed by water, ibid. 
Hence we fee, why the whole of any quantity of common 
air can never be converted into fixed air; for no part of it will 
unite with phlogifton, but the dephlogiflicated part (which; 
never exceeds one-third of the whole). This .Mr. scheele 
has deciftvely proved by expofing liver of fulphur to a mixture 
I 
* Mem. Par. 1777, p. J 9 r * 
f He informed me, that water takes up one-fourteenth of its bulk of dephlo- 
giftkiated air, and only one-twenty-eighth of common air. 
©1 * 
