64, 



FUnillCATION OF NtCKEL. 



cor'cllngly, which it would be useless to enumerate, since 

 they led to nothing interesting. 

 Not iheadcJi- ] could not suspect the existence of a substance, whicli, 



tioii ■)( some , • ■ ■ i • i i i i i. • ^i • • • 



foreign sub- when united with nickel and cobalt, occasions their precipi- 



Mance. tatiou by sulphuretted hidrogeu: for, when I redissolved 



these sulphuieis in muriatic acid* mingled with a few drops 



of nitric acid, and I had separated from them nothing but 



sul{»hur, I could no longer precipitate thein again by the 



samereagent.lt must have arisen therefore fioin some circura- 



Experiment stances peculiar to the operation itself: and in consequence,. 

 ■with a smaller • i , • •. -^i i.i i- t u -.i 



quantity. '" order to examine it with more attention, J began with a 



small quantity. The solution was accomplished in the same 

 way by nitric acid diluted with twice its quantity of water 

 Nitric srvlu ton })y nieasure. Tlie residual sulphur. was. separated by^filtra- 

 an^'fiiteied re- tion, and I evaporated the solution gently to one fourth, I 

 peat^idly. let it cool, to crystallize the oxide of arsenic, which was de- 



posited in pretty large quantity. Having filtered the solu- 

 tion a second time, I evaporated it to a sirupy consistence: 

 when in proportion as the excess of acid was carried off, the 

 arsenia»^e of iron was de{>osited, and formed a kind of gela- 

 tinous magma. Again I filtered and evaporated: and this 

 I repeated to the fourth time, drawing off at each a little^ 

 more arid. 

 Different The (list r-ediment obtained by evaporation was arscniate 



precipi ci eo. ^f i,.^,^ ;,j ^j,g form of a white powder : the second was a 

 mixture of arseni^te of cobalt and iron: the third appearejl 

 to be pure avseiuate of cobalt. The last time I evaporated 

 to dryness; and the povtion'that would not redissolve in >va- 

 ter was arscniate of nickel. 



Si'lphuretted ^^ ^^^.^ tiltra^.on I took care to try the fref!i solution with 



h 10/ 'M 



adAedtothe snl;>hnrctted hidrogen, to endeavour to find the jooint at 



soluuons. which the precipitation of the nickel took place; but I al- 



ways obtained a precipitation of orpiruent* The last ah)ne 

 yielded me a copious sediment of a blackish Ijrown, which 

 was found on examination to contain nickel, arsenic,- and no 

 copper. 1 then conceived, that the proportion of acid might 

 t o I still have an inRueuce in this preci[)itation. With this view 1 



a«id. 



* I psr:fi-. ed, that, duiini; this sokuittn, thr murintic acid took up or- 

 j i ; ent ilia state of cotubination, which could be >fj)arutfcJ i'.oin it by 

 ilvii .ddilioi) of wu.er. 



exauiined 



