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From conliderlng the affinity which this vapour 
has with phlogifton, I was induced to try the effedt 
of a mixture of it with nitrous air. Accordingly, to 
two parts of this vapour, I put one part of nitrous 
air, and, in about twenty-four hours, the whole was 
diminiffied to fomething lefs than the original quan- 
tity of the vapour, and was no farther diminiffied by 
the admiffion of water. Holding the flame of a 
candle over this air, the lower part of it burned green, 
but there was no feniible explofion. At different 
times I collected 2 f ounce meafures of this mixture 
of air; but, upon agitating it in rain-water, it was 
prelently diminiffied to i \ ounce meafures. In this 
ftate it effervefced with nitrous air, and was confi- 
derably diminiffied by it, but not fo much as com- 
mon air. Some allowance, no doubt, muff be made 
for the fmall quantities of common air, which lodged 
on the top of my phials, when I raifed the fume from 
the fpirit of fait ; but, from the precautions that I 
made ufe of, I think that very little is to be allowed 
to this circumffance ; and, upon the whole, I am of 
opinion, that this experiment is an approach to the 
generation 0/ common air, or air fit for refpiration. 
I had alfo imagined, that if air diminifiied by the 
proceffes above-mentioned was afte&ed in this man- 
ner, in confequence of its being faturated with phlo- 
gifton, a mixture of this vapour .might imbibe that 
phlogifton, and render it wholefome again ; but I put 
about one fourth of this vapour to a quantity of air 
in which metals had been calcined, without making 
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any feniible alteration in it. I do not, however, in- 
fer from this, that air is not diminifiied by means of 
phlogifton, fince the air, like feme other fubftances, 
I i 2 may 
