686 PALLADIUM. 



soluble in alcohol as well as in water. When a solution of 

 this salt in alcohol is distilled till only one-fourth of the liquid 

 remains, the solution when evaporated gives a salt containing 

 the elements of ether, belonging to a class of compounds dis- 

 covered by Professor Zeise, and known as the etherized 

 salts of Zeise. The chloride of platinum and ammonium 

 resembles the double salt of potassium. Bonsdorff has 

 formed a large class of compounds of bichloride of platinum 

 with the alkaline, earthy and metallic chlorides, in all of which 

 the salts are united in single equivalents. The bromides and 

 iodides of platinum have likewise been formed, and classes of 

 double salts derived from them. Peroxide of platinum has also 

 been combined with acids, but none of its salts, with the 

 exception of the oxalate, obtained in a crystalline state. 



SECTION II. 



PALLADIUM. 



Eg. 665.9 or 53.36; Pd. 



This metal was discovered in 1803, by Dr. Wollaston. It 

 is precipitated from the solution of the ore of platinum, after 

 the removal by sal ammoniac of that metal, by a solution of 

 cyanide of mercury, and is gradually deposited as a yellowish 

 white flocculent powder, which is cyanide of palladium, and 

 yields the metal when calcined. 



In external characters, palladium closely resembles platinum. 

 It is nearly as infusible, but can more easily be welded. The 

 density of the fused metal is 11.3; after being laminated 11.8. 

 At a certain temperature, the surface of palladium tarnishes 

 and becomes blue from oxidation, but when more strongly 

 heated, the oxide is reduced. It is very slightly attacked by 

 boiling and concentrated hydrochloric and sulphuric acids. 

 Palladium dissolves in nitric acid, communicating a brownish 

 red colour to the acid, while no gas is evolved if the tempera- 

 ture is low, the nitric acid decomposed being converted into 

 nitrous acid. Palladium dissolves with facility in aqua regia ; 

 its surface is blackened by the tincture of iodine, which has no 

 effect upon platinum. This metal has a considerably greater 

 affinity for oxygen than platinum. It forms two oxides, the 

 protoxide of palladium Pd O, and the peroxide Pd O 2 * 



