Acidity, the Comp of: lion of IVatev, and Phlogijlon . i 9 \ 
After this, attending to the water expended in the procefs, I 
found that 1 procured 330 ounce meafures of fixed air with 
the lofs of 160 grains of water. According to this, as the 
air weighed 294. grains, the water in the fixed air mud have 
been 80 parts of 147 of the whole. 
In another experiment, having previoufly found that three 
ounces of the terra ponderofa yielded about 250 ounce meafures 
of fixed air, 1 attended only to the lofs of water in procuring 
it, and I found it to be about one-fifth of an ounce, in two fuc- 
cefiive trials. The quantity of fixed air would weigh 225 
grains, and the water expended about 100 grains j fo that, in 
this experiment alfo, the fixed air mu ft have contained about 
one-half of its weight of water. 
That water enters into the compofition of fixed air, and 
adds confiderably to its weight, is farther probable from the 
folution of terra ponderofa in fpirit of fait. Becaufe when the 
folution is evaporated to drynefs, and the refiduum expofed to 
a red heat, the weight of the air, and of this refiduum, ex- 
ceeds that of the fubftance from which it was procured ; and it 
is probable, that a red heat would expel any marine acid ad- 
hering to it. 
Forty-eight grains of terra ponderofa diflolved in fpirit of 
fait, and then evaporated to drynefs, and expofed to a red 
heat, loft four grains, and yielded eight ounce meafures of 
fixed air, which would weigh 7.2 grains; confequently, three- 
fevenths of the weight of the air was fomething that had 
been gained in the procefs, and therefore probably water. 
The near coincidence of the refults of thefe different expe- 
riments is remarkable, and makes it almoft certain, that no 
marine acid is retained in the terra ponderofa that has been dif- 
folved in it, after expofure to a red heat ; that the generation 
Vol. LXXVIII. X of 
