W. Gibbs on the Platinum metals. 355 



The filtrate is to be evaporated and boiled with an excess of 

 strong chlorhydric acid which completely decomposes the double 

 nitrite of iridium and soda, yielding the salt, IrCl^jNaCl, which 

 IS very soluble in water. An excess of a pure and strong solu- 

 tion of chlorid of ammonium is then to be added, the whole 

 evaporated to dryness, and the dry mass washed with cold water 

 and then with a cold and strong solution of the ammonium salt. 

 There remains a mass of pure chloro-iridate of ammonium which 

 Diay be advantageously rubbed to a fine powder, dissolved in 

 boiling water and allowed to crystallize. The resulting salt is 

 chemically pure and the crystals possess an extraordinary beauty 

 and lustre. The mass of mixed sulphida together with the filter 

 are to be treated with strong chlorhydric acid, and nitric acid 

 added in small portions at a time. By the aid of a gentle heat 

 the sulphids are readily oxydized and dissolved. After sufficient 

 dilution the liquid is to be filtered, the pulp of undestroyed filter 

 paper washed, the filtrate evaporated to dryness, the dry mass 

 digested with concentrated chlorhydric acid and again evaporated 

 to dryness. The dry mass of chlorids and sulphates is to be re- 

 dissolved in water and the platinum, ruthenium and rhodium 



brought into the form of double chlorids and the difficulties 

 ^vhich arise from the presence of the sulphates are avoided. 



The mixed double chlorids are to be boiled with nitrite of 

 potash, evaporated to dryness, and the soluble nitrite of ruthe- 

 nium and potassium dissolved out with absolute alcohol in the 

 Planner described in speaking of the separation of platinum 

 from ruthenium. The ruthenium may then be obtained pure by 

 converting it into the double chlorid of mercury and ruthen- 

 diamin already mentioned. 



The mass undissolved by alcohol consists of chlorplatmate of 

 potassium mixed with both the soluble and the insoluble double 

 nitrites of rhodium and potassium. It is to be boiled with dilute 

 chlorhydric acid, neutralized with carbonate of potash, agam 

 evaporated to dryness, after the addition of nitrite of potash, and 

 again boiled with absolute alcohol which sometimes dissolves a 

 ^race of ruthenium. The undissolved i^ass is then to be treated 

 ^'ith hot water and again evaporated to dryness, and this process 

 repeated two or three limes so as to convert the whole of the 

 soluble rhodium salt into the insoluble salt. The chlorplatinate 

 ?f potassium mav then, after reducing the mass to fine powder, 

 '^e dissolved out by boiling water, when the rhodium salt remains 

 Pi^re as a fine orange-yellow crystalline powder. This may be 



^y- Jovn. Scr.-SKcoND Series, Vol. XXXIV, No. 10-2.-Nov.,186S. 



