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424. Mr, Cavenvisn’s Experiments on Air. 
into nitrous acid. It muft be obferved, that as the vitriolic 
acid produced by the burning fulphur is changed by its union 
with the lime into felenite, which is very little foluble in 
water, a very {mall quantity of nitrous falt, or any other fub- 
ftance which is foluble in water, would have been perceived. 
I alfo tried whether any nitrous acid was produced by phlo- 
gifticating common air with liver of fulphur; for this purpofe 
I made a folution of flowers of fulphur by boiling it with lime, 
and’ put a littie of it into a large receiver, and fhook it fres 
quently, changing now and then the air, till the yellow co- 
lour of the folution was quite gone; a fign that all the fulphur 
was, by the lofs of its phlogifton, turned into vitriolic acid, and 
united to the lime, or precipitated ; the liquor was then filtered 
and evaporated, but it yielded not the leaft nitrous falt. 
The experiment was repeated in nearly the fame manner 
with dephlogifticated air procured from. red precipitate ; but 
not the leaft nitrous acid was obtained.’ 
It is well known that common felenite is very little foluble 
in water ; whereas that procured in the two. laft experiments 
was very foluble, and even cryftallized readily, and was in- 
tenfely bitter; this however appeared to be owing merely’ to 
the acid with which it was formed being very much phlogif- 
ticated; for on evaporating it to drynefs, and expofing it to the 
air fora few days, it became much lefs foluble, fo that on 
adding water to it not much diffolved; and by repeating this 
procefs once or twice, it feemed to become not more foluble than 
{elenite made in the common manner. 
This folubility of the felenite caufed fome trouble.in trying 
the experiment ; for while it continued much foluble it would 
have been impoffible to have diftinguithed ‘a {mall mixture of 
nitrous falt; but by the abovementioned procefs I was able to 
diftinguifh: 
