472 



Transactions. 



Let us now compare these results with those obtained by Professor 

 J. F. Kemp, as tabulated in his pamphlet on the " Geological Relations of 

 Platinum" (see Bulletin of U.S. Geological Survey, No. 193). Professor 

 Kemp has here collected the results of forty-two analyses of platinum by 

 various chemists, and has arranged them in a series of curves in which per- 

 centages of platinum form the abscissae and those of other metals the ordi- 

 nates. On examining the table and analyses it will be seen that, generally 

 speaking, there seems to be a kind of rule with regard to the amount of 

 osmiridum present and that of the pure metal present, the one increasing 

 as the other decreases, and vice versa. The same relation seems to hold 

 in the case of the iron present. It will be noticed that on no occasion when 

 the percentage of platinum in the alloy amounts to 70 does the amount of 

 osmiridium exceed 10-5 per cent., and that percentage occurs only in one 

 specimen. Further, where the amount of osmiridium is relatively small 

 the amount of iron is fairly large, but where the osmiridium is in large 

 quantity the iron falls very low. Thus with a percentage of IrOs (iridos- 

 mine) of 6-36 the amount of iron is 15-58, but with 25 per cent, of IrOs 

 the iron falls to 4-30 per cent. 



In looking now at our analysis some remarkable peculiarities are at 

 once evident. In the first place, there is platinum amounting to 75 per 

 cent., yet the amount of osmiridium is very high — 14 per cent. This is a 

 direct contrast to the results of Professor Kemp's conclusion ; indeed, only 

 one analysis at all similar to it has been found. It is given in Dana's 

 " System of Mineralogy," the sample being from British Columbia, and 

 having the following proportions : — 



Per Cent. 

 Platinum . . . . . . . . .. 68-19 



Iron 



Palladium 



Rhodium 



Iridium 



Copper 



Iridosmine 



7-87 

 0-26 

 3-10 

 1-21 

 3-09 

 14-62 



There is another from the same locality having IrOs equal to 10-51 per 

 cent., with platinum 72 per cent. 



Further, in all the analyses where platinum amounts to between 72 

 and 76 per cent, the iron amounts to not less than 10 per cent., whereas 

 in the Orepuki metal it reaches only to 5 per cent. The amount of 

 rhodium present is also high. It will also be seen that a fair amount of 

 gold was shown to be present ; but it must be remembered that this was 

 identified only by loss on treatment with acid, and, as the estimation by 

 loss is not quite reliable with very small quantities, it is probable that the 

 amount is not quite so much. The other constituents are, ho\yever, in very 

 fair accordance with the results got for them by other writers. 



An analysis was also attempted of the osmiridium residue. By Claus's 

 method the percentage of iridium was found to be 59-63. Further sepa- 

 ration was not effected. 



Origin of the Platinum. 



Owing to the interest quite recently awakened with regard to the 

 geological relations of the platinum discoveries, a large number of places 

 — with a more or less technical description of them — where the metal has 



