394 Dr. Crawford's Experiments on the Matter 
fuddenly changed to a deep brown, approaching to black. 
When thefe mixtures were diluted with about twice theic 
weight of diftilled water, the brown tinge of the former en- 
tirely difappeared; but the latter ftill retained its brown colour, 
although it was fomewhat fainter than it had been upon the firfb 
addition of the acid. 
The aerial fluid which was difengaged in the foregoing trials 
from the matter of cancer, by the vitriolic acid, appeared from 
its odour to have a nearer refemblance to hepatic than to any 
other fpecies of air. As it feemed, trom its lenfible qualities, 
to be a very aftive, and probably a deleterious principle, I 
endeavoured more particularly to enquire into its nature, and 
to compare it with common hepatic air. But before I i elate 
the trials which were made with that view, it may not be im- 
proper briefly to mention the characters by which common he- 
patic air is diftinguiftied. 
It has a fmell refembling that of rotten eggs ; it is inflam- 
mable, and during its combuftion in the open air, fulphur is 
depofited; it communicates a black colour to filver and copper, 
and a brownifh tinge to lead and iron ; it is foluble in water, 
and when a folution of nitrated filver is dropped into water 
impregnated with it, the mixture becomes turbid, and a dark- 
coloured precipitate falls to the bottom ; by the addition of 
the nitrated filver, the odour of the hepatic air is rendered 
much fainter; and it is entirely deftroyed by concentrated nir 
trous, or by dephlogifticated marine acid. 
To determine whether the aerial fluid contained in the can- 
cerous matter poflefled thefe properties, a portion of this fub- 
ftance was diffufed through diftilled water. The mixture 
being filtered, a'fmall quantity of nitrated filver was dropped 
into it. In a little time, an afh-coloured cloud was produced. 
