1913-] HEYL— PLATINUM IN NORTH CAROLINA. 29 



nitric acids. On warming the alcoholic filtrate it turned a deep 

 brown color, again suggesting palladium. From the filtrate 2.7 mg. 

 FcoOs were obtained by precipitation with ammonia. 



The y.j mg. of Pt-Ir sponge was treated with dilute aqua regia 

 until a constant residue was obtained, which weighed 1.8 mg. Add- 

 ing this to the 0.4 mg. previously obtained, we have about 16 per 

 cent. Ir. The Pt figures about 40 per cent, and the Fe 15 per cent., 

 leaving 29 per cent, unaccounted for. No further evidence of Pd 

 could be obtained from the very small amount of material. 



The total recovery of acid-resisting metallic particles by this 

 method was only about 25 per cent, of the assay value of Pt, and 

 undoubtedly comprised only the largest particles. The term largest 

 is to be understood in a relative sense only, as none of the particles 

 could have weighed as much as o.i mg. 



There seems to be no doubt that the platinum exists in the rock 

 in the form of the usual alloy or mixture of the different platinum 

 metals and iron, with probably a greater proportion of iridium than 

 is usual in the Russian variety. It is worthy of note that as far as 

 is shown by the various published analyses of platinum from Amer- 

 ican sources these ores have a greater iridium content than the ores 

 from Siberia. 



As an experiment on a larger scale, half a ton of rock from a 

 locality about two miles distant from the Klondike was smelted in 

 the experimental blast furnace at the IMassachusetts Institute of 

 Technology, and yielded 11 mg. of platinum. A sample of this rock 

 had given an assay value of 0.4 ounces per ton, accompanied by a 

 satisfactory blank. A second assay had yielded nothing. It was 

 customary to make assays on 4 A. T. lots of ore. 



All the foregoing facts are consistent with the hypothesis that 

 the platinum exists in the rock in sparsely scattered granules, so few 

 in number that by no amount of rolling and mixing can we bring 

 the sample into such a state that there will be at least one such granule 

 in each assay ton of the ore. 



As a matter of interest, during the progress of the assaying work 

 on the North Carolina rock, we were led to examine samples of 

 rock from a great many localities for platinum. The curious fact 



