20 



Analysed. 



Ko iridium. 



palladium. 



No iron, er 

 ibociium. 



A minute per 

 tiou of gold. 



ON PLATINA AND NATIYE PALLADIUU FEO>| BRASIL. 



no polish, and does not appear worn ; but most of the grains 

 seem to be small fragments of a spongy substance; and even 

 those which are yet entire and rounded on all sides rese t a 

 sort of r • ghuess :(.tally different frorii that of t e former, 

 as their surface coijsists of small spherical protuberances 

 close.y coherent to each other, with the interstices extremely 

 fi'lean, and free from any degree of tarnish. 



The first portion that I employed for solution was taken 

 without any ^election, and being digested with a small quan- 

 tity of nitro-muriatic acid, two of the grains were acted oa 

 much more rapidly than is usual with platina, and seemed 

 to give a redder colour than that metal alone. These grains 

 •were consequently taken out, washed, and reserved for se^ 

 parate examination, and the solution was allowed to proceed 

 till the rest were entirely dissolved. By the addition of 

 muriate of ammonia an abundant precipitate was formed of 

 a blight yellow colour. This precipitate was evidently pla^ 

 tina, and its colour satisfied me, that the grains had not 

 been brought into their present state from Peruvian platina 

 by means of arsenic; for where arsenic has been employed, 

 I have observed that the iridium contained in that ore is ren^ 

 dered more soluble than before, and thence communicates 

 its red colour to the precipitate. 



From the grains thus examined, there appeared not to be 

 any iridium dissolved, nor any black powder containing iri- 

 dium undissolved. 



1 next endeavoured, by prussiate of mercury, to ascertain 

 the presence of palladium ; but though a precipitate which 

 occurred indicated a certain quantity, it remained doubtful 

 whether it was derived from the grains of platina themselves, 

 or from the two small fragments that had been in part dis- 

 solved before they were separated from the rest. 



By addition of ammonia to the solution, no iron was pre- 

 cipitated ; and when the solution was afterwards allowed 

 slowly to evaporate, I could discern no crystals or colour that 

 I could ascribe to the presence of rhodium. In short, it 

 seemed that these grains are really native platina nearly 

 pure. 



In order to discover whether the grains themselves con- 

 tained any portion of gold, I selected three of the largest 



weighing 



