j)r, Crawford’s Experiments on the Matter 
thrice its weight of diftilled water. To this mixture a littie 
vitriolic acid was added; upon which an eftervefcence took 
place, and the air that was difengaged was received iu a 
phial over mercury. When one half of the mercury was 
expelled from the phial, the latter was inverted over diftilled 
water, and the portion of the mercury that remained in it 
being fuffered to defeend, and the water to rife into its place, 
the phial was clofely corked. The air and water were then 
brilkly agitated together, and the phial being a fecond time 
inverted over diftilled water, the cork was removed ; when 
it appeared by the heighth to which the water rofe, that a 
part of the air had been abforbed. The water contained in 
the phial was now found to be ftrongly impregnated with the 
odour of the cancerous matter, and a little nitrated diver being 
dropped into it, a purplifh cloud, inclining to red, was pro- 
duced. It is proper to obferve, that the change of colour upon 
the addition of the nitrated filver, in this experiment, was at 
iirft fcarcely perceptible ; but in the courfe of a few minutes 
it became very diftindh As it might perhaps be doubtful, 
whether this alteration would not be produced in the nitrated 
filver by expofure to the air alone, the colour of the mixture 
was compared with that of a fimilar mixture of nitrated filver 
and of pure diftilled water, which had remained expofed to 
the open air for an equal length of time. Although a flight 
change of colour was produced in the latter inftance, yet it 
was much lefs confiderable than that which took place in tne 
former. 
In the above recited experiment, the air came over mixed with 
the common air that was contained in the proof, i he quantity 
of aerial fluid that can be thus extricated by the addition of 
the acid without the affiftance of heat, is not very confiderable. 
If 
