JPhlogiJHcation of Spirit of Nitre* 1 43- 
In another procefs, of the fame kind, the glafs tube con- 
tained 0.92 oz. m. of common air, and the air that came cut 
of it after the procefs was one ounce meafure, of the ftandard 
of 1.6 with two meafures of nitrous air, and computing as I 
did before, the phlogifticated air in the tube before the procefs? 
was 0.6072 oz. m., and after the procefs 0.54 oz. m. 
In thefe computations it is fuppofed, that the air emitted by 
the acid was perfe&ly pure, fo that ail the phlogifticated air 
that is found after the procefs is fuppofed to have been con- 
tained in the common air confined in the tube before it was. 
commenced. But I found, that the air emitted by the acid is 
by no means perfectly pure, fo that much of the impurity 
mu ft: be afcribed to this circumftance. 
In order to exclude all air from the contact of the acid, I 
made a quantity of it to boil in the tube, and when the vapour 
had expelled all the air, I fealed it hermetically, in the manner 
in which water hammers are made ; and then expoftng it to 
heat, found that it acquired as high a colour as when air had 
been confined along with it i fo that it is evident, that air is not 
neceffary to this effect. When the tube was opened under wa- 
ter, a quantity of dephlogifticated air ruftied out, exceedingly 
white as before ; but when I examined it, I found it to be of 
the ftandard of only 0.66. When this impurity is confidered, 
it will appear, that when much air is yielded in this procefs* 
fome phlogifticated air may have been imbibed, though, com- 
puting in the manner above mentioned, the phlogifticated air 
after the procefs fhould be in greater quantity than was con- 
tained in the tube before it, as was the cafe in the following 
experiment. 
In a glafs tube which, befides the acid, contained 1.13 oz* 
m. of common air, I expofed colourlefs fpirit of nitre to heat 
6 tilt 
