PLATINIC COMPOUNDS. C85 



barytes, nitrate of platinum is obtained. One half of its oxide 

 may be precipitated by soda, from the last salt, but when a 

 larger quantity of alkali is added, a subsalt is thrown down. 

 The precipitated oxide is hydrated, very bulky and resembles 

 perfectly peroxide of iron precipitated by ammonia. When 

 heated, it first loses its water, and becomes black, then its 

 oxygen, and leaves metallic platinum. Peroxide of platinum 

 combines with acids, and forms a class of salts, which are either 

 yellow or reddish brown. It has also a decided affinity for bases, 

 and forms insoluble compounds with the alkalies, earths and 

 many metallic oxides. It forms also, like peroxide of gold, a 

 fulminating ammoniacal compound, discovered by Mr. E. Davy. 



Bisulphuret of platinum, Pt S 2 , is formed by adding a solution 

 of bichloride of platinum, drop by drop, to a solution of sul- 

 phuret of potassium. It is dark brown and by desiccation 

 becomes black. When dried in open air, a portion of its 

 sulphur is converted into sulphuric acid, by the absorption of 

 oxygen, and the mass becomes strongly acid. 



Bichloride of platinum, Pt C1 2 , 2119 or 169.78. Is obtained 

 by concentrating the solution of platinum in aqua regia. as a 

 red saline mass, which becomes brown when deprived of its 

 water of crystallization by heat. The solution of this salt when 

 pure, is an intense and unmixed yellow ; the red colour which it 

 usually exhibits being due to iridium or to protochloride of 

 platinum. Bichloride of platinum is soluble in alcohol, and the 

 solution is used to separate potash in the analysis of a salt. 

 The salt being first ignited, to expel ammonia, is dissolved in a 

 minimum of water, and the solution mixed with chloride of 

 platinum, a yellow granular precipitate falls, if the salt contains 

 potash, which may be washed with diluted alcohol, and dried. 

 One hundred parts of this salt are equivalent to 19.33 parts of 

 potash, and to 40.39 of platinum. 



Chloride of platinum and potassium, KC1 -f Pt C1 2 , is the salt 

 which falls on mixing chloride of platinum with chloride of 

 potassium or any other salt of potash. The crystalline grains 

 of which it is composed are regular octohedrons. This salt is 

 soluble to a certain extent in water, but is wholly insoluble in 

 alcohol. It is anhydrous. A very intense bright red-heat is 

 required for its complete decomposition. The double chloride 

 of platinum and sodium, Na Cl + Pt C1 2 + 6HO, crystallizes in 

 beautiful transparent prisms of a bright yellow colour. It is 



