214 Continuation of the Experiments and Obfervations 
generated during the procefs that exhibits it ? and if fo, what 
are its conflituent parts ? 
The firfl queflion is eafily anfwered ; for in fuch phlogiflic 
proceffes as are attended with the deflruftion of the fubflances 
that are known to contain fixed air, as thofe of the animal and 
vegetable kingdom, the fixed air may be fuppofed to proceed in 
many .cafes, both from the decompofed fubflance and from the 
refpirable air ; and of this fort are the proceffes of combuflion 
of mofl animal and vegetable fubflances, and fermentation ; 
but the fixed air., that appears in fuch phlogiflic proceffes as 
are performed on fubflances that contain no fixed air, muff be 
deemed to proceed from the refpirable air fingly. And of this 
cafe we have four clear inflances ; the calcination of metals ; 
the decompofition of nitrous air by refpirable air ; the diminu- 
tion of common air by the eledlric fpark ; and, laflly, its 
diminution by amalgamation. 
And firft as to the calcination of metals, Dr. priestley 
has obferved, that by this operation refpirable air (and only 
refpirable air) is diminifhed between one-fourth and one-fifth, 
both in its weight and bulk; but Mr. Lavoisier has demon- 
ftiated, that nothing is loft or efcapes through the veffels (as 
Mr. scheele would have it) ; for the weight and materials 
continue un diminifhed when the operation is performed in 
dole veffels *- That part, therefore, which the air lofes is 
taken up by the metallic calx, which accordingly is found to 
gain the very weight which the air lofes. Now the air con- 
tained in the calx is fixed air; for Mr. Lavoisier alfo ob- 
ferved, that by the calcination of lead, by folar heat, over lime- 
water, the water was rendered {lightly turbid f* It is true, 
* Mem. Par. 1774. 
| 1 lavois. 291 . 
that 
