ON PALLADIUM. 1 cj J 



At (his lime I found it advantageous to neutralize the folution The folutionwa^j 

 with foda, atul to employa folution of green fulphate of iron neutralized with 

 for the precipitation of the gold, of which, I believe, a portion plefenr ^reci'i- 

 may always be obtained from the mixed ore; but I have ob- t.ued by folution 

 ferved in experiments upon any quantities of mere grains of °^^/^^" *"'r"^*^ 

 crude platina carefully fe!e6led, that (he fmallefl: portion of 

 gold could not be detefled as a conftituent part of the ore 

 iifdi; 



Bars of iron were fubfequenlly employed as before for A fecond me- 



recovering the platina that remained diflblved, togetlier ^''"'\F''"'P"^^^ 

 ' , . ^^'is thrown 



with (h<;re fubfiances which I have fmce found to accom- down by iron, 

 pany it. 



The precipitate thus obtained, which I di^inguifn by the 

 name of the fecond metallic precipitate, was- to appearance of 

 a blacker colour than the former, and was a finer powder. 



As I was not at firft prepared to exped^ any new bodies, I 

 proceeded (o treat tlie fecond precipitate, as the former, by fo- 

 lution and precipitation. But I foon obferved appearances 

 whitit I could not explain by fuppofilion of the prefence of any 

 known bodies, and was led (o form conjeiSlures of future difco- 

 verie?, which fubfequent inquiry has fully confirmed. 



Wl)en I atlemoted to diflolve this fecond metallic precipitate "^^'^ was not S 

 in nitro-muriatic acid, I was furprifed to find that a part of it mu"riatic"acid^°' 

 refilled the a^ion of that folvent, notwithflanding any vaji^ 

 tions in the relative proportions or flrength of the acrd^ 

 employed to form the compound, and although the whole of this 

 powder had certainly been twice completely diffolved. 



The folution formed in this cafe was of a peculiarly dark This folution 



colour, and when I endeavoured to precipitate the platina ^^^^^'^^ '^^. 



. . * . '^ and its precipi- 



from it by fal ammoniac, the precipitate obtained was fmall tation byfalam- 



in quantity, and, inftead of being yellow, was of a deep "^""'^'^ ^^^ <^^^? 



' , " .^ ,. . ■ 1 • , T 1- 1 . '■^'^' occafioned 



red colour, anhng from an impurity which 1 did not at that jjy iridium. 



time underdand, but which we fince know, from the experi- 

 ments of Mr. Defcotiis, is occafioned by the metal now called 

 iridium. 



The folution, inflead of being rendered pale by the preci- Precipitation of 

 nitalion of the platina, retained its dark colour in confequence ,,? '^"■«i."?^- 

 of the other metals that remained in folution ; but, as I had by iron, 

 not then learned the means of feparating them from each 

 other, and as the quantity of fluid which accumulated ccca* 

 lioned n-.e fume inconvenience, I decompofed it by iron, as 



in 



