272 On Palladium and Rhodium. [Oct. 



succeeded only in fusing it in small quantities upon charcoal, the 

 combustion of which was increased by a jet of oxygen gas.* 



I have observed that if the heat be kept up after it is melted, it 

 enters into ebullition, and burns, throwing out very brilliant sparks. 

 A portion of the metal which has escaped the combustion dissipates, 

 and is condensed on the surface of the charcoal in the form of very 

 small grains. 



Platinum melted in the same manner does not burn like palla- 

 dium, which shows that this last metal is more volatile and more 

 combustible. 1 found the specific gravity of palladium, rolled out 

 into a plate, 12 and a very small fraction. 



VI. 



Solution of Palladium in Nitro-muriatic Acid. 



A gramme (15*444 grains) of palladium placed in contact with 

 six grammes of nitro-muriatic acid, composed of equal parts of the 

 two acids, was speedily attacked without the assistance of heat, and 

 the liquid assumed a reddish brown colour. At first no nitrous gas 

 was disengaged ; but when heat was applied, a great deal of this 

 gas made its escape. This shows that palladium requires a great 

 deal of oxygen in order to dissolve. 



The solution of palladium is of a reddish brown colour, which is 

 the more intense the more acid it contains ; for in proportion as the 

 excess of acid is driven off, the colour diminishes, and a fawn 

 coloured salt is obtained, little soluble in water, and giving that 

 liquid a yellow colour ; but the solution becomes reddish brown on 

 the addition of some drops of muriatic acid. 



Neutral muriate of palladium is but little soluble in water, but 

 very soluble in water acidulated with muriatic acid. The solution 

 does not crystallize regularly. 



Liquid muriate of ammonia put into the acid solution of palladium 

 occasions no precipitate ; but if the liquids are concentrated, there 

 speedily form a great number of needle-form crystals, of a greenish 

 yellow colour, and very remarkable in their appearance. When 

 the crystallization takes place slowly, this salt presents the form of 

 four-sided prisms, or elongated hexagons. It is ammonio-muriate 

 of palladium. If to the solution of this triple salt we add some 

 drops of ammonia to saturate the excess of acid, a very brilliant 

 crystalline precipitate falls, of a fine rose colour, which is the sub- 

 muriate of palladium-ar.d-ammonia already mentioned. 



The solution of potash gives a brown colour to muriate of palla- 

 dium, and separates from it red and brilliant flocks, appearing as if 

 composed of plates. The liquid remains coloured, notwithstanding 

 the excess of alkali; but when heat is applied, the whole of the 

 oxide of palladium is thrown down, and the liquid becomes 

 colourless. The alkaline carbonates produce the same effect. 



* Mr. Ciienevix says that palladium melts in the ordinary licit of our furn.ices; 

 fctit it is probable that what he experimented on was not pure. 



