232 Litelligejice a)id Miscellaneous Articles. 



>»•'■ ON OSMIUM AND ITS COMPOUNDS. 



M. Claus states, that from fifteen pounds of platina residue he 

 obtained nearly four ounces of metallic osmium. During these ex- 

 periments he states that he discovered previously to M. Fremy the 

 osmite of potash, but it was obtained by a different process. It is a 

 very beautiful salt, which crystallizes in regular octahedrons of a 

 black, garnet, or rose-red colour. The colour depends upon the 

 quickness of their formation. When formed slowly by gradual cool- 

 ing in solutions which are not too much saturated, they are black, 

 the edges being transparent and of a garnet-red colour : if they are 

 quickly deposited from a saturated solution, they are garnet-red ; and 

 if the separation of the salt be effected by agitation, the crystals are 

 pulverulent and of a rose-red colour. When reduced to powder, the 

 salt is almost white ; it is KO -f- OsO^ + Aq-. It dissolves slowly in 

 water, imparting to it the same colour as raanganesiate of potash. 

 The solution is partially decomposed by evaporation ; free osmic acid, 

 OsO'', is disengaged, and black oxide of osmium, OsO'--|-Aq, is pre- 

 cipitated ; the liquor becomes strongly alkaline, and a part of the salt 

 crystallizes without decomposition ; the decomposition occasioned 

 by evaporation may be prevented by adding great excess of potash 

 to the solution of the salt. Acids readily decompose the solution of 

 osmite of potash, yielding oxide of osmium and osmic acid : 2(Os03) 

 produce OsO^ + OsO^; this fact the author also states that he ob- 

 served previously to M, Fremy. The oxide has the remarkable pro- 

 perty of decomposing with slight detonation when it is heated in a 

 glass tube into metallic osmium and osmic acid; 2(Os02) yield 

 Os + OsO* . Osmite of barytes, BaO -f OsO^ -\- Aq, forms fine black 

 crystals with a diamond-like splendour ; this salt is prepared by mix- 

 ing a solution of osmic acid with excess of barytes water ; the yellow 

 liquor deposits crystals at the expiration of a month ; a large quan- 

 tity of the salts of iridium was also obtained among other products 

 of the first fusion with nitre ; among these Avere three ounces of a 

 salt which the author supposed to be a salt of iridium, but which he 

 afterwards found to be chloride of potassium and ruthenium. 



The author then attempted to obtain this new metal from the re- 

 sidue which had been once heated to redness with nitre, and treated 

 with water and acid ; the following process succeeded, and one ounce 

 and a half of the chloride of potassium and ruthenium was obtained 

 by it : — equal parts of the residue and of nitre were heated to white- 

 ness for two hours in a Hessian crucible ; the calcined mass was taken 

 by an iron spatula from the crucible while red-hot, and reduced when 

 cooled to coarse powder. This was treated with distilled water, and 

 the mixture allowed to become clear by standing ; this solution was 

 of a fine deep yellow colour, and water was added as long as it con- 

 tinued to dissolve. This solution contains rutheniate, chromate, and 

 silicate of potash, without any trace of rhodium or iridium, and only 

 a slight one of osmiate of potash. Nitric acid is to be cautiously 

 added to the solution till it ceases to be alkaline ; this precipitates 

 a compound of oxide of ruthenium and potash, and a small quantity 



