jc 3 Dr. Crawford’s Experiments on the Matter 
I next endeavoured to determine toe produffs which refult 
from the combuftion of pure air, with animal air, or with the 
compound aerial fluid extricated from the lean of animal fub- 
ftatices by heat. With this intention I expofed the lean of 
frefh mutton, in a fraall coated glals retoit, to a red heat. 
The air which was received over mercury towards the end of 
the diftillation was divided into two feparate portions; one Oi 
which was agitated with water till the foluble part was ab- 
forbed ; the other was not agitated with that fluid. One mea- 
fure of the former was introduced, over mercury, into a ftrong 
,rlafs tube adapted for the purpofe of firing aerial fluids by the 
electric (hock. This was mixed with one meafure and an half 
of pure air. The portion of the tube occupied by the mixture 
was one inch and two-tenths. A fmall (hock being made to 
pafs through it, a violent explofion took place, and the fpace 
occupied by the refidue was nine-tenths of an inch. The 
height of the mercury in the tube, previoufly to the combuftion, 
was 4.8 inches. After the airs were fired, its height was 5.1 
inches. Allowance being made for the difference of expanfion 
produced by this caufe, it appeared, that the volumes of the 
airs, previoufly to the combuftion, and fubfequent to it, were 
as 100 to 75 nearly. The refidue being agitated with water, 
fix-tenths were abforbed ; and the portion which was thus ab- 
forbed was found, by the precipitation which it produced in 
' lime water, to be fixed air. Of the infoluble remainder, five 
parts being mixed with five of nitrous air, a diminution of 
three parts took place ; whence it follows, that one-fifth of 
the infoluble refidue was pure air. 
The pure air which was ufed in this experiment had been 
previoufly agitated with water, to free it entirely from fixed 
a i r and "the, Inflammable air had undergone a fimiiar agitation. 
T f 
