for procuring pure Platinum. 249 



reddish-coloured solution, there remains a residuum, under the 

 form of a brilliant blackish powder, which consists of an alloy 

 of iridium and osmium. One part of this is a fine powder (see 

 Note to paragraph 1,) and the other forms brilliant spangles. 

 We shall return, in the sequel, to the residuum ; let us employ 

 ourselves at present on the solution. 



9. We have said that all the platinum, rhodium, and palla- 

 dium, were dissolved ; but the acid also dissolves a little 

 iridium and osmium, as well as the iron alloyed with the plati- 

 num grains. During the action of the acid on the ore, at the 

 same time that the nitrous gas and chlorine are evolved, there 

 is volatilized a little water and muriatic acid, which carry over 

 with them a notable quantity of oxide of osmium, which is con- 

 densed in the receiver. 



10. All the successive solutions of the ore of platinum are 

 united and introduced into a retort of proper capacity, to which 

 the receiver containing the former condensed vapours is at- 

 tached. The retort is now heated on a sand-bath, till its contents 

 acquire the consistence of syrup. By this means we drive off all 

 the excess of the acid, which carries along with it into the re- 

 ceiver the whole oxide of osmium which that solution contained. 



11. The product of the last distillation being saturated with 

 lime, we distil over to one-half the volume. The product of 

 this new distillation has an extremely penetraiing odour, on 

 account of the large proportion of oxide of osmium which it 

 contains. It must be preserved in glass bottles, furnished 

 with well-ground stoppers. 



12. The concentrated solution of platinum is to be diluted 

 with from five to six times its weight of water, then filtered. 



13. The black powder which was not acted on by the nitro- 

 muriatic acid, is also to be washed with water, dried, and 

 kept in a phial ; we shall distinguish it by the name of the 

 black -powder. 



14. Into the filtered solution we pour a saturated solution 

 of muriate of ammonia, till this ceases to occasion any pre- 

 cipitate. In this operation there are formed ammonio-muriates 

 of platinum, iridium, rhodium, and palladium. These twQ 



Vo(.. XII. S 



