SOLUTION OF PLATINUM SAND. 61 



borax, and silica, whereby a fusible slag of oxide of lead would 

 result, and might be skimmed from the surface of the gold. 

 Palladium and platinum, not unfrequentlj present in California 

 gold, are likewise removed by the nitric acid in parting silver 

 from gold. Grains of iridosmin have been observed in Ca- 

 lifornia gold, in distinct particles, even after three or more 

 fusions, and seem to have no tendency whatever to enter into 

 an alloy ; but, while casting such gold, these particles collect at 

 the bottom of the pot, from their greater specific gravity, and, 

 by remelting in a small crucible, and carefully casting, they 

 may be obtained mixed with a small quantity of gold. The 

 latter is dissolved by nitromuriatic acid, and the iridosmin 

 obtained pure. — J. C. B. 



8. Platinoid Metals. — Platinum is associated with several 

 other metals in the platinum sand which is found in some 

 gold-districts. They have not been found as a distinct deposit 

 in California, but have been observed in the United States 

 Mint in the operations of assaying and parting. These as- 

 sociated metals are palladium, rhodium, iridium, and osmium, 

 to which we must add the lately discovered metal, ruthenium. 

 They have a sufficient resemblance to be classed together, and 

 are obtained by a similar hydrometallurgic treatment. The 

 grains of iridosmin, alluded to under gold, have been quali- 

 tatively examined and found to contain the new metal ruthe- 

 nium, as was observed by Claus in relation to the iridosmin 

 from other localities. Palladium has been observed, and at 

 times in sufficient quantity to render the gold brittle. The 

 quantities of platinoid metals found in the California gold are 

 small, about l|ft» of iridosmin having been obtained from 

 about 25 tons of the gold, tuo^ootj? but the greater part has, of 

 course, passed into the coin, the coarser grains only being 

 left.—./. C. B. 



Solution of Platinum Sand. — To dissolve it more readily, 

 it is fused with 3 times its weight of zinc, and the brittle mass 

 thus obtained is powdered and sifted. It is digested with 

 dilute sulphuric acid to dissolve most of the zinc and iron, 

 washed with water, and then boiled with nitric acid, which 

 F 



