on Hepatic Ah'. 147 
felenite, and is feparable from alkalies and earths by all other 
acids. 
That the matter of heat enters into the compofition of this 
air, is evident from the experiments of M. Scheele, who paid 
particular attention to that objeft. Fie found, that acids excite 
much lefs fenfible heat in uniting with liver of fulphur , whe- 
ther alkaline or calcareous, than while uniting with a propor- 
tion of cauftic fixed alkali or lime equal to that which enters 
into the compofition of thofe livers ; whence hejuftly infers, 
that the differences nters into the compofition of the hepatic air 
produced. I ha.ve proved the fame thing another way : for, 
inflead of decompofing an alkaline hepar by marine acid, I 
tried to decompofe it by a faturate folution both of marine 
felenite and marine Epfom. The decompofition indeed took 
place, but no hepatic air was produced : for the acid having 
given out its fpecific heat on uniting to the earths, had none 
to lofe or communicate on uniting to the alkali, and confe- 
quently the fulphur receiving none could not be thrown into 
an aerial ftate. 
It is remarkable, that bodies capable of an aerial form re- 
ceive the latent heat neceffary for that form, much more rea- 
dily from a body that parts with its fpecific heat than by the 
mere application of fenfible heat. Thus aerated barytes can- 
not be decompofed by mere heat, as Dr. Withering has 
fhewn, though its air is eafily feparated from it by an acid ; 
and in the fame manner antimony cannot be defulphurated 
even by vitrefa&ion, though it may by acids : fo liver of ful- 
phur will not give hepatic air by mere heat, though it will 
by the intervention of an acid, even the weakeft. The reafon 
of which feems to be this : the matter of heat has no parti- 
cular affinity with any fubftance, as is evident from its paffing 
U 2 indifferently 
