1814.^ On Palladium and Rhodium. 221 



which I employed to separate the palladium from the rhodium, and 

 the latter from the iron and copper with which it is always mixed. 



I dilute the liquid above described and deprived of most of its 

 platinum with water, and I add muriatic acid, if there be not 

 already a sufficient excess of it. I then gradually add ammonia, 

 but in such quantity as not entirely to saturate the excess of acid. 

 I then agitate the mixture. There immediately appear a g at 

 number of needle-form crystals, very brilliant, and of a fine red 

 colour. 



I allow them to fall to the bottom, and add a few drops of am- 

 monia to a portion of the liquid. If it give crystals as at first, 1 

 add a new portion of that alkali to the liquid, and continue to do 

 so till it ceases to furnish crystals. 



I then decant off the clear liquid, and wash the precipitate, first 

 with cold water, and then with hot water, which may be done 

 without risk, as it is scarcely soluble. If by accident the proper 

 point of saturation has been passed, and some salt of iron or rho- 

 dium is mixed with this precipitate, it is easily freed from it by 

 digesting the precipitate for a few minutes in water acidulated with 

 muriatic acid. This salt is an ammonio-muriate of palladium 

 containing a minimum of acid, the properties of which I shall 

 describe below. To obtain the metal from it, nothing more is 

 necessary than to heat it red-hot. 



Now to obtain the rhodium, I concentrate the liquids from which 

 the palladium has been separated, till they crystallize totally on 

 cooling. I put the crystals aside to drain. They are frequently of 

 two kinds and of two colours. Some have the form of hexahedral 

 plates, and a fine ruby red colour ; while others, fewer in number, 

 are square prisms of a yellowish green colour. These last are 

 ammonio-muriate of palladium. The water which flows from these 

 crystals has a yellowish green colour, owing to copper and iron 

 which it holds in solution. 



The crystals being drained, 1 pound them in a porcelain mortar, 

 and wash them with alcohol of 36°, which I leave over them for 

 24 hours in a close flask, agitating the mixture frequently. When 

 the yellowish green colour which the alcohol acquires does not 

 increase, it is decanted off, and fresh alcohol added ; and this 

 process is continued till the alcohol ceases to acquire any colour, 

 and till it ceases, when examined by re-agents, to exhibit any 

 traces of iron or copper. 



If any portion of palladium remained mixed with the rhodium, 

 it would be dissolved in the alcohol added towards the cud of the 

 process, and this alcohol would yield by spontaneous evaporation 

 very long square prisms of a greenish yellow colour. We sometimes 

 observe among these crystals small ruby red crystals; they consist 

 of ammoriio-muriate of rhodium dissolved by the alcohol. 



The salt of rhodium is then dried in the opeQ air. It is of a 

 fine red colour. As it may still contain some portion of the triple 

 •alt of platinum, it is to be dissolved in a little water, which may 



