Intelligence and Miscellaneous Articles. 559 



contains. We had to have recourse to a new process, the accuracy 

 of which appears to be perfect as regards the elimination of iridium, 

 and which succeeds for rhodium on condition of a little of the pla- 

 tinum being carried away with the latter. 



Pure lead, obtained by calcining pure acetate of lead, is the solvent 

 we employed to effect these separations. 



Let us suppose that some thin plates of that complex alloy which 

 is met with in commerce under the name of platinum are fused with 

 from six to ten times their weight of lead. This latter will dissolve 

 the copper, the palladium, a portion of the iron, and a small quan- 

 tity of platinum. These will be dissolved, together with the excess 

 of lead, by pure nitric acid. There will remain an alloy of platinum 

 and lead, which weak aqua regia will dissolve, carrying away some 

 rhodium. The final residue will be a crystallized alloy containing 

 iridium, ruthenium, and iron, insoluble in lead. 



Jf the platinum is rich in rhodium, this, when combined with the . 

 lead, will not be dissolved by concentrated aqua regia, but will be 

 separated from the iridium mixed with iron and ruthenium by 

 boiling concentrated sulphuric acid. 



The platinum will be separated from the rhodium and lead dis- 

 solved with it in the aqua regia by sal ammoniac ; but, to com- 

 pletely eliminate the rhodium, the chloroplatinate of ammonia (or 

 platinum yellow) must be precipitated in powder so fine as to 

 appear amorphous and nearly white. It is to be washed with 

 water acidulated with hydrochloric acid, which removes a small 

 quantity of platinum. This last method was com nunicated to 

 us by M. Stas. 



The platinum is fused, by means of our blowpipe, in a crucible of 

 pure lime, or at least free from iron. When the metallic mass is 

 well liquefied and has undergone the action of the refining-fire, we 

 close briskly the two cocks which admit the illuminr ting-gas and 

 oxygen, and thus solidify the surface of the ingot. The lime, being 

 strongly heated, keeps the lower part in fusion ; and the shrinking 

 takes place on that side, most often so as to permit the cavities 

 which form there to communicate with the exterior. By working 

 thus we have obtained the highest densities, measured upon masses 

 of 200-250 grammes of pure platinum. If we had possessed greater 

 quantities of platinum, we should have cast large ingots and taken 

 specimens of the metal from the centre or the perfectly sound 

 parts of the ingots. On such specimens we intend to investigate the 

 action of cold-beating and annealing — a subject of great interest. 



2. Iridium. — The iridium made use of was extracted from mate- 

 rials belonging to M. Matthey, and prepared by our methods ; we 

 attacked it afresh, to clear it of the last traces of impurity. This 

 iridium, finely pulverized, either in a mortar or by dissolving it in 

 zinc which was afterwards driven off by heat, was fused with lead. 

 The ingot, treated with nitric acid, aqua regia, and boiling sul- 

 phuric acid, left the iridium crystallized and still containing some 

 ruthenium (without a trace of osmium) and a little iron. It was 



