Intelligence and Miscellaneous Ai tides. 233 



and osmium, as it is found in the platinum sand in the Urahan 

 mountains, is mixed with chloride of potassium, and a current of 

 chlorine is passed through it ; the whole being heated, a combination 

 takes place: when the solution is evaporated, dark brown, or nearly 

 black octahedrons are deposited. They are composed of 



Iridium 26*6 



Osmium • IS'i 



Chlorine and chloride potassium 60* 100* 



giving the formula Os Ch + 2 Ir Cl^ + 3 K CI*. 



If this salt is mixed with its own weight of dry carbonate of soda 

 and heated in a retort, one portion of the osmium is sublimed in the 

 neck of the retort as a binoxide. By heating the residue in con- 

 tact with the air, a further portion of osmium is sublimed. The re- 

 maining sesquioxide of iridium retains only a small quantity of 

 oxide of osmium, which by digestion in nitro-muriatic acid and 

 heating may be entirely driven off. 



2. — Triple Salts of Chloride of Iridium and Platinum with Muri' 

 ate of Ammonia. — This salt is formed in abundance in the platinum 

 manufactory at St. Petersburg on the evaporation of the solutions 

 from which platinum is precipitated by sal ammoniac. Hitherto it 

 has been considered as a combination of chloride of iridium and 

 muriate of ammonia. It is found however to contain, besides chlo- 

 ride of platinum and ammonia, a small quantity of palladium. 

 100 parts are composed of 31-76 iridium, 

 10*59 platinum, 

 1*25 palladium, 

 56 40 chlorine and muriate of ammonia. 

 It is therefore a combination of 1 atom chloride of platinum, 3 atoms 

 chloride of iridium, and 4 atoms muriate of ammonia, with a small 

 quantity of chloride of palladium and ammonia. 



2).— Triple Salt of Chloride of Iridium and Platinum tvith Chlo. 

 ride of Potassium. — When the sesquioxide of iridium and platinum 

 is digested with muriatic acid, the solution gives off the smell of 

 chlorine; chloride of iridium and chloride of platinum are dissolved 

 by the acid. If nitrate of potash is added to the solution, the yellow 

 colour changes to a wine red, and by the addition of chloride of 

 potassium dark red octahedral crystals are deposited on evapora- 

 tion J this salt is composed of 8-00 iridium, 

 32-00 platinum, 



60'00 chlorine and chloride of potash, 

 giving the formula Ir CI* + 4 PI Cl^ -f 5 K Cl^. 



This action of ::'uriatic acid on a mixture of sesquioxide of iridium 

 with platinum should not be overlooked in the analysis (according to 

 the direction of Berzelius) of platinum sand. Berzelius directs that 

 the mixture of the oxides of platinum, rhodium, and iridium, which re- 

 mains after the precipitation by carbonate of soda of the double al • 

 kaline sails, should be digested with muriatic acid, in order to with- 

 draw a portion of the alkali with which the oxides of rhodium and 

 iridium have combined. By this means iridium and platinum will in 

 every instance be held in solution by the muriatic acid, which is 

 Third Series. Vol. 9. No. 53. Sept. 1836. 2 D 



