OF PLATINA IN AVA. 283 



7. The two nitromuriatic solutions were mixed together and treated 

 with muriate of ammonia, which threw down a copious orange precipitate 

 of the triple salt of platina, weighing 21.9 grains, which are equivalent to 

 9.45 of metallic platina, or nearly twenty per cent. 



8. The solutions still retaining their orange red colour were treated 

 with carbonate of potash, which precipitated at first mere oxide of iron 

 and afterwards a bulky gelatinous precipitate of a light yellow colour, 

 which was left unexamined for want of leisure, but which was sup- 

 posed to contain a small portion of some earth mixed with carbonate 

 of iron. 



9. The undissolved residue of A and B, 27.9 grains, was mixed with 

 caustic potash, and heated to redness in a platina crucible, according to the 

 formula of Wollaston, to rid it of silicious matter which prevents the ready 

 solution of the metallic grains. The fused mass was dissolved out of the 

 crucible with weak muriatic acid, and was boiled in the same, imparting 

 to it a bright yellow colour. The black grains remained in deposit, and 

 were but little affected even by repeated boiling in nitromuriatic acid. 

 The process was repeated with the same want of success. 21.82 grains of 

 a fine heavy blue-black powder remained out of the original 28 grains: 

 much of the difference must be attributed to the loss in such an operation 

 upon a fine powder ; — a part, however, is accounted for in the earths and 

 iron taken up by the muriatic acid. 



10. According to the experiments of R. Bingley, Esq., H. M. Assay- 

 Master, at the London Mint, small portions of platina and its companion 

 metals in alloy with gold in;iy be 8{>[)araU"(l i)y the ordinary jiroccss for 

 refining gold, or cpiartation w ilh silver and solution in nitric acid. I there- 

 fore endeavoured to obtain a solution oi' the refractory uiclal by uniting it 

 with gold. 



