On Platina and Native Palladium from BrasiL 165 



or black colour. The Brasilian platina, on the contrary, 

 lias no polish, and does not appear worn j but most of the 

 grains seem to be small fragments of a spongy substance, 

 and even those which are yet entire aud rounded on all 

 sides, present a sort of roughness totally different from that 

 of the former, as their surface consists of small spherical 

 protuberances closely coherent to each other, with the 

 interstices extremely clean, and free from any degree of 

 tarnish. 



The first portion that I employed for solution was taken 

 without any selection, and being digested with a small 

 quantity of nitro muriatic acid, two of the grains were acted 

 on much more rapidly than is usual with platina, and seem- 

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

 grains were consequently taken out, washed, and reserved 

 For separate examination, and the solution was allowed to 

 proceed till the rest were entirely dissolved. By the addi- 

 tion of muriate of ammonia an abundant precipitate was 

 formed of a bright yellow colour. This precipitate was 

 evidently platina, 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 rendered more soluble than before, and hence 

 communicates its red colour to the precipitate. 



From the grains thus examined, there appeared not ta 

 be any iridium dissolved, nor any black pbwder containing 

 iridium undissolved. 



T 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 them- 

 selves, or from the two small fragments that had been in 

 part dissolved before they were separated from the rest. 



By addition of ammonia to the solution, no iron was 

 precipitated 5 and when the solution was afterwards al- 

 lowed slowly to evaporate, 1 could discern no crystals or 

 colour that f could ascribe to the presence of rhodium. In 

 short, it seemed that these grains are really native platma 

 nearly pure. 



In order to discover whether the grains themselves con- 

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

 weighing together eight grains and a half; and after a so- 

 lution and precipitation, as before, by muriate of ammonia, 

 I added a solution of green sulphate of iron, and obtained a 

 precipitate of gold. Il was, however, far too small in quan- 



L 3 tity 



