on the /pacific Gravities > See. of Saline Subfiances. 229 
much phlogifton to common air -as an equal bulk of inflamma- 
ble air does when fired in the fame proportion of common air. 
Now, when inflammable air unites with common air, its 
whole weight unites to it, as it contains nothing elfe but pure 
phlogifton ; fince, therefore, nitrous air phlogifticates common 
air to the fame degree that inflammable air does, it parts with 
a quantity of phlogifton equal to the weight of a volume of 
inflammable air fimilar to that of nitrous air. Now 100 cubic 
inches. of inflammable air weigh 3,5 gr. ; therefore, 10a cubic 
inches of nitrous air part with 3,5 gr. of phlogifton when they 
communicate their phlogifton to as much common air as will 
take it up* 1 lay, that nitrous air parts with as much phlogifton,, 
becaufe it is certain’, that it does not part with the whole of its 
phlogifton to common or dephlogifticated air, for itt contains 
much more, as already fhewn, and* as appears- bv the red co- 
lour, it conftantly affumes when mixed with common or de- 
phlogifticated’ air, which colour belongs to the nitrous acid 
combined with, its remaining phlogifton, and not to the fixed 
air then produced, nor to the phlogifticated air remaining, as 
is very evident. Hence the acid, thus formed, is volatile.. 
4. pr. 267. 
One meafure of tlie pureft dephlogifticated air and two of 
nitrous air occupy but -,4-^th parts of one meafure, as Dr. 
priestley has obferved, vol. IV. p. 245. Suppofe one mea- 
fure to contain 1 00, cubic inches, then the whole very nearly of 
the nitrous air will- difappear, its acid uniting to the water. over 
which the experiment is made, and 97 cubic inches of: the de* 
phlogifticated'air,, which is converted into fixed air by its union. 
\yith the phlogifton of the nitrous air ; therefore 97 cubic 
inches of dephlogifticated air take up all the phlogifton which. 
200 cubic inches of nitrous air will: part with; and this we 
have 
