Phlogification of Spirit of Nitre* 
When I made the former experiments, I had no fufpicion 
that the air contained in the tube had any concern in the refult 
of them ; and, in thofe which I made in the phials in a mode- 
rate heat, 1 found that the acid received its colour when the 
beft vacuum that I could make with an air pump was over it. 
My friend Mr. Kirwan, however, having always fuf- 
peeled, that the air was a principal agent in the bufinefs, I at 
this time gave particular attention to this eircumftance ; fuppo» 
ling that, if any part of the common air had been imbibed, it 
muft have been the phlogifticated , and that it was the phlo* 
gifton from this kind of air which had phlogifticated the acid. 
The real refult, however, was not fo much in favour of this 
fuppofition as I had expected ; for the principal effedt of the 
procefs was the emiffion of dephlogifticated air, fo that the 
acid feems to become what we call phlogifticated, by parting 
with this ingredient in its compofition. 
I put a fmall quantity of the colourlefs acid into a long glafs 
tube, which befides the acid would have contained 1.23 ounce 
meafures of common air, but that the vapour of the acid ex- 
cluded about one-twentieth of the quantity. Having fealed 
the tube hermetically, I (hut it up in a gun barrel, in the man- 
ner mentioned above, and expofed it to a boiling heat for feve- 
ral hours, and then opening it under w T ater there came out 
of it 2.03 ounce meafures of air, very turbid and white ; and 
when it was examined, it appeared to be of the ftandard of 
1.02, with two equal meafures of nitrous air; when with one 
meafure of the fame nitrous air the ftandard of the common 
air was 1.07. The quantity of phlogifticated air abforbed in 
this experiment I afeertained by the following computation. 
As one meafure of common air, and an equal quantity ot 
nitrous air were reduced to 1.07 m. it is evident, that 0.93 ni. 
X a had 
