Mr, Cavendish's Experiments on ^ir^ ^.yy- 



filver, fecmed to be pcrftCdy neutralized, as they did not at all 

 dlfcolour paper tinged with the juice of blue flowers. Being 

 evaporated to dryneis, 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 more fatisfa-^ipn, I tried this experiment over again on a 

 larger fcale. About five times the former quantity of foap-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 reprefented in ng. 3. 

 the fpark was continued till nq more air could be made to difap- 

 pear. The liquor, when poured out of the tube, fmelled evidently 

 of phlogifticated .nitrous acid, and being evaporated to dryne<^, 

 yielded i .V gr. of fait, which is pretty exactly equal in weight to 

 the nitre which that quantity of foap-lees would have afforded if 

 faturated with nitrous acid. This fait was found, by the man- 

 ner in which paper dipped into a folution of it burned, to b? 

 true nitre. It appeared, by the teft of terra potiderofa falitit^ to 

 contain not more vitriolic acid than the foap-lees themfelves 

 contained, which was exceffively little ; and there is no reafon 

 to think that any other acid entered into it, except the nitrpus. 

 . A circumftance, however, occurred, which at firft feeme4 

 to fliew, that this fait contained fome marine acid ; namely^ 

 an evident precipitation took place, when a folution of lilver 

 was added to fome of it diflblved in \yater| though the foap- 

 lees u fed in its formation were perfetflly free from marine. acid, 

 and though, to prevent all danger of any precipitate being 

 formed by an excefs of alkali tn^it, 'fome purified nitrouS' acid - 

 had been added to it, previous to the addition of the folutioii 

 of filver. On confideration, however, 1 fufpe£led,, that this 

 precipitation might arife from the nitrous acid in it being phlo- 



D d d 2 gidicated ; 



