PALLADOUS COMPOUNDS. 68/ 



Protoxide of palladium, Palladous oxide, Pd O, 765.9 or 

 61.36. This oxide is obtained by dissolving palladium in nitric 

 acid, evaporating the solution to dryness, and calcining the 

 nitrate by a gentle heat. It forms a black mass, which dis- 

 solves with difficulty in acids. When carbonate of potash or 

 soda is added in excess to a palladous salt, the hydrated prot- 

 oxide precipitates of a very dark brown colour. This oxide is 

 easily deprived of its water by heat, but a violent calcination 

 is necessary to reduce it to the metallic state. 



Protosulphuret of palladium, Pd S, is obtained by precipita- 

 tion of a palladous salt by sulphuretted hydrogen, and is of a 

 dark brown colour, or is prepared by the direct union of its ele- 

 ments. 



Protochloride of palladium, Pd Cl, is prepared by dissolving 

 palladium in hydrochloric acid, to which a little nitric acid is 

 added, and evaporating the solution to dryness, to expel the 

 excess of acid. The compound is a mass of a dark brown 

 colour, which becomes black when made anhydrous by heat, and 

 may be fused in a glass vessel. When heated in platinum ves- 

 sels it becomes contaminated by the protochloride of that metal. 

 When dissolved with chloride of potassium, it forms a double 

 salt, K Cl + Pd Cl, which is soluble in cold, arid considerably 

 more so in hot water, and crystallizes in four sided prisms, of a 

 dull yellow. Protochloride of palladium also combines with 

 chloride of ammonium and chloride of sodium, and forms double 

 salts, according to Bonsdorff, with most other chlorides. Pro- 

 tochloride of palladium forms two ammoniacal compounds; one 

 of which is insoluble, greenish yellow and anhydrous, PdCl -f- NH 3 . 



Protocyanide of palladium, Pd Cy, is always formed when 

 cyanide of mercury is added to a neutral solution of palladium, 

 as a light coloured precipitate which becomes grey after drying. 

 When the solution of palladium is acid no precipitate is formed, 

 and when the solution contains copper, the precipitate has a 

 green colour. Palladium appears to have a greater affinity for 

 cyanogen than any other metal. The cyanide of mercury even is 

 decomposed when boiled with protoxide of palladium, and cya- 

 nide of palladium formed. When this cyanide is dissolved in 

 ammonia, and the excess of the latter allowed to escape by eva- 

 poration, a precipitate of brilliant, colourless, crystalline plates 

 is formed, which appears to be ammoniacal cyanide of palla- 

 dium. 



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