THE 



PHILOSOPHICAL MAGAZINE 



AND 



ANNALS OF PHILOSOPHY. 



[NEW SERIES.] 



JULY 1829. 



I. The Baker ian Lecture.— Oii a Method of rendering Platina 

 malleable. By William Hyde Wollaston, M.D. F.R.S. 



Sj-c.* 



AS, from long experience, 1 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 en- 

 deavour to describe, as briefly as is consistent with perspi- 

 cuity, 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 lor 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 

 lor the sake of obtaining a purer result, as of occonomy 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 



*T r, ,T * ^''''''"' ''"^ Pli'lo-^ophical Trniisactioiis for lHi.'!>. Part I. 



N. S. Vol. 6. No. 3 1 . Jidi/ 1 829. B lo 



