[ 393 ] 
puzzling appearance in chemiftry) admit of a very eafy 
explication by the help of my late experiments. It is 
generally fuppofed, that in this cafe a fulphur is formed, 
by the union of the nitrous acid and the phlogijion of 
the body with which it is detonated ; which fulphur is 
fo inflammable, that it cannot exifl a moment without 
decompofition : and it has been thought, that in the pro- 
cefs of making the clyjfus of nitre, the acid is intirely 
deftroyed or changed. But, in both thefe cafes, I have 
no doubt, that the acid enters into the compofition of 
fome of the kinds of air which are generated upon thofe 
occafions. I once mixed a quantity of the ore of lead 
with fpirit of nitre, and when it was dry, put it into a 
gun-barrel, filled up to the mouth with fand, in order 
to collecSt the air that heat would expel from it, in the 
ufual manner. The produdtion of air was very great 
and rapid ; and when the heat became confiderable, all 
the contents of the gun-barrel were exploded with great 
violence, and a loud report, demolifhing the-vellel which 
I had placed to receive the air. The next time, putting 
the fame materials into a glafs veffel, and difpofing the 
apparatus in fuch a manner as that the explofion could 
not affect the collected air, I found it to be very ftrongly 
nitrous. Such, therefore, I conclude to be the produce 
of the explofion of gun-powder, fince charcoal with fpi- 
rit of nitre yields this kind of air. In the detonation of 
nitre with fubftances that contain little phlogijion^ the 
acid may form common air, or air much purer than 
that. 
Gg g 2 
As 
