i Mr. Cavendish's Experiments on Air » 
yet, as fome remained unabforbed, it did not appear for certain. 
Whether that was of the fame nature as the reft or not. For this 
purpofe I diminiflied a fimilar mixture of dephlogifticated and 
common air, in the fame manner as before, till it was reduced to a 
fmall part of its original bulk. I then, in order to decompound 
as much as I could of the phlogifticated air which remained in 
the tube, added fome dephlogifticated air to it, and continued the 
fpark till no further diminution took place. Having by tliefc 
means condenfed as much as I could of the phlogifticated air, I 
let up fome folution of liver of fulphur to abforb the dephlo- 
gifticated air •; after which oniy a fmall bubble of air remained 
unahforbed* which certainly was not more than of the 
bulk of the phlogifticated air let up into the tube; fo that if 
there is any part of the phlogifticated air of our atmofphere 
which differs from the reft, and cannot be reduced to nitrous 
acid, we may fafely conclude* that it is not more than x 4-<? 
part of the whole. 
The foregoing experiments fhew, that the chief caiife of 
the diminution which common, air, or a mixture of common 
and dephlogifticated air-, buffers by the eledtric fpark-, is the 
converfion of the air into nitrous acid ; but yet it feemed not 
Unlikely, that when any liquor, Containing inflammable mat- 
ter, was in contadt with the air in the tube* fome of this 
matter might be burnt by the fpark, and thereby diminifh the 
air, as I fuppofed in the above-mentioned Paper to be the cafe. 
The heft way 'which occurred to me of difeoveting whether 
this happened or not, was to pafs the fpark through dephlogi {tr- 
eated air, included between different liquors': for then, if the 
diminution proceeded folely from the converfion of air into 
nitrous acid, it is plain that-, when the dephlogifticated air was 
perfectly pure, no diminution would take place ; but when it 
contained 
