PHILOSOPHICAL TRANSACTIONS. 
I. The Bakerian Lecture. — On a method of rendering Platina malleable. 
By William Hyde Wollaston, M.D. F.R.S. Sj’c. 
Read November 20 , 1 828. 
As, from long experience, I probably am better acquainted with the treatment 
of Platina, so as to render it perfectly malleable, than any other member of this 
Society, I will endeavour to describe, as briefly as is consistent with perspicuity, 
the processes which I put in practice for this purpose, during a series of years, 
without seeing any occasion to wish for further improvement. 
The usual means of giving chemical purity to this metal, by solution in aqua 
regia and precipitation with sal ammoniac, are known to every chemist ; but 
I doubt whether sufficient care is usually taken to avoid dissolving the Iridium 
contained in the ore, by due dilution of the solvent. In an account which I 
gave in the Philosophical Transactions for 1804, of a new metal. Rhodium, 
contained in crude platina, I have mentioned this precaution, but omitted to 
state to what degree the acids should be diluted. I now therefore recommend, 
that to every measure of the strongest muriatic acid employed, there be added 
an equal measure of water ; and moreover, that the nitric acid used be what is 
called “ single aquafortis as well for the sake of obtaining a purer result, as 
of economy in the purchase of nitric acid. 
With regard to the proportions in which the acids are to be used, I may 
say, in round numbers, that muriatic acid, equivalent to 150 marble, together 
with nitric acid equivalent to 40 marble, will take 100 of crude platina; but 
in order to avoid waste of acid, and also to render the solution purer, there 
should be in the menstruum a redundance of 20 per cent at least of the ore. 
mdcccxxix. b 
