Mr . CaveN'DISh’-s Experiments on Air. 
fiver, feerned to be perfectly neutralized, as they did not at all 
difcolpur paper tinged with the juice of blue dowers. Being 
■ evaporated to drynefs., they left a fmall quantity of fait, which 
was evidently nitre, as appeared by the manner in which paper, 
impregnated with a folution of it, burned. 
For mote fatisfadion, I tried this experiment -over again on a 
larger fc ale. About five times the former quantity of leap- lees 
were now let up into a tube of a larger bore ; and a mixture of 
dephlogifticated and common air, in the fame proportions as 
before., being introduced by the apparatus rep refen ted in fig. 3. 
the fpark was continued till no more air could be made to difap- 
pear. The liquor, when poured out of the tube, fmelled evidently 
of phlegifiicated nitrous acid, and being evaporated to dryness, 
yielded 1 p s gr. of fait, which is pretty exactly equal in weight to 
the nitre which that quantity of foap-lees wpuld have aftorded if 
faturated with nitrous acid. Thisfak was found, by the man- 
ner in which paper dipped into a folution of it burned, to be 
true nitre. It appeared, by the tell of terra ponderofa Jahta , to 
contain not more vitriolic acid than the foap-lees themfelves 
contained, which was excelfively little ; and there is no reafoii 
to think that any other acid entered into it, except the nitrous. 
A circumftance, however, occurred, which at fir ft feemed 
to Ihew, that this fait contained fome marine acid ; namely, 
an evident precipitation took place when a folution of fiver 
was added to fome of it diflblvedin water,; though the foap- 
lees ufed in its formation were perfectly free from marine acid, 
and though, to prevent all danger of any precipitate being 
formed by an excefs of alkali in it, fome purified nitrous acid 
had been added to it, previous to the addition of the folution 
of fiver, On confideration, however, 1 lufpedted,, that this 
precipitation might arife from the nitrous acid in it being phlo- 
D d d 2 gilt i cat ed ; 
