122 ON PALLADIUM. 



in the former inftances and formed a tliird melalllc precipitate, 

 which could more coinmodioufly be referved for fubfequent 

 examination. 

 Much of this In this iail liep I committed an error which afterwards occa- 

 «i"fnlbl'ubuT* ^'""^^ ™^ confiderable difficulty, for I found that a great part 

 of this precipitate confifling of rhodium was unexpededly ren- 

 dered infoluble by ihis treatment, and refembled the refiduum 

 of the fecond metallic precipitate abovementioned. 



As I have already communicated to this fociety, in my Paper 

 upon rhodium, the procefs by which I fubfequenlly avoided 

 this difficulty, I fhall at prefent return to a previous liage 

 of my progrefs, and relate the means by which I firft ob- 

 tained palladium in my attempts to analyze the fecond me- 

 tallic precipitate. 



§ IV. Separalion of Palladium. 



Separation of There was no difficulty in afcertaining the prefence of lead 



palladium. as one of the ingredients of this precipitate, by means of mu- 



,tallic precipitate riatic acid, which dilfolved lead and iron and a fmall quantity 



contained lead, qJ' copper. It was equally eafy to obtain a larger portion of 



copper, and aiio- ^' ,., . ^ •, ., ,.,.,-. /- i 



ther metal pie- copper by dilute nitrous acid, with which it formed as ulual a 

 <ipiuble by cop- blue folution. But when I endeavoured to extract the whole 

 of the copper by a ftronger acid, it was evident, from the dark 

 brown colour of the folution, that fome other metallic ingre- 

 dient had alfo been diflblved. I at firft afcribed this colour 

 to iron ; but, when I confidered that this fubtiance had been 

 more flowly acted upon than copper, I relinquiQied that hy- 

 pothtfi<, and endeavouring to precipitate a portion of it by a 

 clean plate of copper, I obtained a black powder adhering to a 

 furface of platina on which I had placed the folution. As 

 this precipitate was foluble in nitric acid, it evidently conlifted 

 neither of gold nor platina ; as the folution in that acid was of 

 a red colour, the metal could not be either filver or mercury ; 

 and as the precipitation of it by copper excluded the fuppofi- 

 tion of a'l other known metals, I had reafon to fufped the 

 prelence of fome new body, but was not fully fatisfied 

 of its exiftence until I attempted the precipitation of it by 

 mercury. 

 It was feparated For this purpofe I agitated a fmall quantity of mercury in 

 meKurTwIth ^'^*"" "'^''"^'^ fululion previoufly warmed, and obfervtd the mer- 

 thc folution with cur\ to acquire the confidence of an amaig-im. After this 



') amalgam 



