Dr. Wollaston on the Discovery of Palladium. 321 
employed to form the compound, and although the whole of this 
powder had certainly been twice completely dissolved. 
The solution formed in this case was of a peculiarly dark 
colour, and when I endeavoured to precipitate the platina from 
it by sal ammoniac, the precipitate obtained was small in quan- 
tity, and, instead of being yellow, was of a deep red colour, 
arising from an impurity which I did not at that time understand, 
but which we since know, from the experiments of Mr. Des- 
cotils, is occasioned by the metal now called iridium. 
The solution, instead of being rendered pale by the precipita- 
tion of the platina, retained its dark colour in consequence of 
the other metals that remained in solution ; but, as I had not 
then learned the means of separating them from each other, 
and as the quantity of fluid which accumulated occasioned me 
some inconvenience, I decomposed it by iron, as in the former 
instances, and formed a third metallic precipitate, which could 
more commodiously be reserved for subsequent examination. 
In this last step I committed an error which afterwards occa- 
sioned me considerable difficulty, for I found that a great part 
of this precipitate consisting of rhodium was unexpectedly ren- 
dered insoluble by this treatment, and resembled the residuum 
of the second metallic precipitate abovementioned. 
As I have already communicated to this society, in my Paper 
upon rhodium, the process by which I subsequently avoided 
this difficulty, I shall at present return to a previous stage of 
my progress, and relate the means by which I first obtained 
palladium in my attempts to analyze the second metallic pre- 
cipitate. 
MDCCCV. 
Tt 
