297 
decompounding fixed Air. 
To afford a still more decisive proof that carbonic acid had 
not been combined, or escaped, in this experiment, but had 
been destroyed, I exposed some of the same parcel of alkali 
which had afforded charcoal to the same degree of heat, in 
tubes, under similar circumstances to those in the above ex- 
periment ; and I found that no carbonic acid, but a little water, 
came over into the air-apparatus ; that the total weight of the 
alkali was diminished, but that a given weight of it, after 
the experiment, afforded rather more carbonic acid, by so- 
lution in acetous acid, than an equal weight of the same 
parcel of alkali not thus subjected to heat. This diminu- 
tion of weight of alkali, and greater proportion of carbonic 
acid, I impute to the water visibly separated in the glass tubes, 
and, perhaps, also absorbed in the earthen ones. Accident 
afforded a still more decisive proof of the decomposition of 
carbonic acid. In the beginning of the experiment, the tubes 
sometimes cracked about four or five inches from the part con- 
taining the phosphorus : on cooling, I found, in the part be- 
low the crack, black alkaline matter, which yielded much less 
carbonic acid than the same weight of alkali before the experi- 
ment ; whereas the alkali above the crack was white, and con- 
tained the same quantity of this elastic fluid that it did before 
it was exposed to heat. 
In the experiment above particularly described, it appears 
that in one part of the alkali there was a deficiency of twenty 
ounce measures of carbonic acid per cent, of alkali ; but a pro- 
duction of rather more than eight grains of charcoal, and of 
as much phosphoric acid as formed about thirty grains of 
phosphoric selenite ; the composition of which may be esti- 
mated to be, of phosphorus, five grains; respirable air, ten 
grains ; and quick -lime, fifteen grains. Now, as it has been 
