;[s*7 ] 
any kind of air that has been diminifhed, and ren- 
dered noxious by any other procefs ; but when it 
is put to a quantity of nitrous air, it dinii- 
nifties it fo much, that no more than one fourth 
of the original quantity will be left. The effefl 
of this procefs is generally perceived in five or fix 
hours, about which time the vifible effervefcence 
of the mixture begins ; and in a very fhort time 
it advances fo rapidly, that in about an hour almoft 
the whole effedt will have taken place. If it be 
fuffered to hand a day or two longer, the air will 
ftill be diminifhed farther, but only a very little 
farther, in proportion to the firft diminution. The 
glafsjar, in which the air and this mixture have 
been confined, has generally been fo much heated 
in this procefs, that I have not been able to 
touch it. 
Nitrous air thus diminifhed has not the peculiar 
fmell of nitrous air, but fmells juft like common 
air ill which the fame mixture has flood ; and it 
is not capable of being diminifhed any farther, by 
a frefh mixture of iron and brimftone. 
Common air faturated with nitrous air is alfb 
no farther diminifhed by this mixture of iron 
filings and brimftone, though the mixture fer- 
ments with great heat, and fwells very much 
in it. 
Plants die very foon, both in nitrous air, and 
alfo in common air faturated with nitrous air, but 
efpecially in the former. 
Neither nitrous air, nor common air faturated 
with nitrous air, differs in fpecific gravity from 
common air, or, at leaft, fo little, that I could 
Vol. LXII. F f not 
