of Atmospherical Air, Se. 137 
place for several hours: and the iron shall acquire 
weight from 25 to 30 grains, though not made to 
fuse. The cup of the pipe should be slightly cover- 
ed to prevent loss; but room should be left for the 
escape of the air, which is continually circulating 
through the tube. Those who have a furnace with 
a muffle may make this experiment in the most sa- 
tisfactory manner. 
Dr. Priestley next says, that the phlogistication 
of nitric-acid is owing, in some cases, to its imbib- 
ing something; and not always to its parting with - 
something, which the antiphlogistians maintain, 
He dissents from them, because nitrous air being, 
as he terms it, imbibed by nitric acid, the latter be. 
comes phlogisticated.—To this we may reply, that 
part of the oxygen of the nitric acid combines with 
the nitrous air, and forms nitrous acid with it. The 
nitric acid, being thus deprived of a portion of its 
oxygen, thereby becomes nitrous acid, or what has 
been called phlogisticated nitrous acid. The dif. 
ference between the nitric and nitrous acids, consists 
in the proportion between their common basis and 
the principle of acidity. Hence itis plain, that they 
may be transformed into one another; that is to 
say, the proportion of their parts may be altered, 
either by subtraction of the principle of acidity, or 
by addition of the basis, and wice versa. The Doc- 
tor’s objection is therefore merely a dispute about 
words, 
+ VOLLV. S 
