396 Intelligence and Miscellaneous Articles. 



CONTRIBUTIONS TO THE CHEMISTRY OF THE METALS OF 

 PLATINA. BY M. C. CLAUS. 



On examining the residuum of the treatment of platina by its sol- 

 vent, the author had an opportunity of observing several reactions oc- 

 curring between the metals of platina and their combinations which 

 had not been remarked, but which appeared to him worthy of atten- 

 tion. The following is a sketch of these reactions. 



1. Chloride of Iridium and Nitrate of Silver. — It is well known 

 that the chlorine of the solutions of the various platina metals is not 

 precipitated as pure chloride of silver by the nitrate. In employing 

 chloride of iridium, a compound is also obtained, which, according 

 to the author, is an argento-sesquichloride of iridium, insoluble in 

 water or in acids, and difficultly soluble in ammonia, but from which 

 it may always be obtained in the form of rhomboids, as brilliant as 

 diamonds. M. Claus analysed this saU, and found it to correspond 

 to the formula 3Ag CI, +lr2 CP. 



2. Action of Sulphuric Acid and Sulphite of Potash on the Chlo' 

 ride and double compounds of some of the Platina Metals. — Sulphu- 

 rous acid reduces the higher chlorides of the platina metals to a 

 lower degree; the chloride of platina into protochloride, and the 

 chloride of iridium to sesquichloride, &c. As to the double salts of 

 these chlorides, sulphite of potash gives with them a series of com- 

 pounds of peculiar composition which contain sulphurous acid, com- 

 municating to them properties which are quite peculiar. 



a. Compounds of Iridium — When for the preparation of potassio- 

 sesquichloride of iridium, eight parts of water are poured upon po- 

 tassio-chloride of iridium in fine powder, and sulphurous acid is 

 passed through the liquor till an olive-coloured solution is formed, 

 the chloride is converted into sesquichloride, accompanied with the 

 formation of sulphurous and hydrochloric acids. This salt, the com- 

 position of which is represented by 3K Cl + Ir^ Cl^ + GAq, effloresces 

 readily in warm dry air ; it is opake, and its crystals become covered 

 with a bright green powder. It is insoluble in alcohol, soluble in 

 water, forming an olive-green solution, but by transmitted light it is 

 slightly purple. It has the bitter taste of chloride of iridium ; but 

 it is more permanent, and the solution may be evaporated nearly to 

 dryness without decomposition. The alkalies decompose it with 

 difficulty. Aqua regia converts it readily into chloride, and nitrate 

 of silver immediately precipitates, without any blue reaction, the 

 double salt 3Ag Cl + Ir^ C\\ 



The solution of potassio-chloride of iridium, reduced by sulphurous 

 acid, and from which the greater part of the sesquichloride may be 

 precipitated by carbonate of potash, preserves its olive-green colour 

 at common temperatures ; but if it be heated, it passes after some 

 time to a red colour, and eventually to a bright yellow. 



It forms also several compounds of peculiar composition, which 

 contain sulphurous acid, and which, when mixed together, may be 

 separated, some in the crystalline form and others in that of powder, 

 by evaporations which are of difficult execution. The author sue- 



