284 NOTE ON THE DISCOVERY OF PLATINA IN AVA. 



For this purpose, 2 grains of the black powder were wrapped up in a 

 plate of pure gold weighing 20 grains, which was again enclosed in 50 grains 

 of pure silver, and the whole fused together in a wind furnace. The bead 

 exhibited black specks, as of iron oxide, on parts of its surface, but most 

 of the powder had united with the compound metal. 



On lamination and dissolution in the usual way, the nitric acid did 

 not acquire any peculiar colour, and the gold cornet, when annealed, 

 shewed the same spotted appearance as had been remarked in the button : 

 it had a weight of 21 grains. On solution of this gold in nitromuriatic 

 acid, the liquid took a dirty green colour from the suspension of a very fine 

 dark blue powder, which quickly subsided, and had the same appearance 

 as at first. The powder was placed in a Stourbridge clay crucible and 

 urged in the heat of a forge until the crucible melted, without reduction of 

 the powder to the metallic state ; and it was only upon subjection to the 

 oxihydrogen flame that it was agglutinated into a bright metallic sponge, 

 similar to that of the iridium separated in the analysis of the platina but- 

 ton from Ava, before alluded to. 



From the above imperfect examination, it appears that there is a pre- 

 dominance of iridium in the Ava platina ore to a much larger extent than in 

 the ores from South America ov from the Ural mountains. I hope hereafter 

 to obtain a more copious supply of the mineral, and then to ascertain the 

 presence of oxmium and the other metals which usually accompany pla- 

 tina. The present Note has been drawn up solely with a view to certify 

 the interesting fact of the existence of platina among the gold washings of 

 the Ava rivers ; and in connection with that fact it may be farther stated, 

 that the platina constitutes 20 per cent, of the cleaned ore, and that it 

 is accompanied with about twice its weight of iridium. The remainder 

 appears to be chiefly oxide iron. 



