27-4 On Palladium and Rhodium. [Oct. 



VIII. Rhodium. 



'Examination of the Ammonio-muriate of Rhodium. 



After having separated the palladium, and having evaporated the 

 liquor containing the muriate of rhodium, to obtain that salt in 

 crystals, the mother water was poured oft", and the crystals allowed 

 to drain. They were then repeatedly washed with alcohol, as has 

 been mentioned before. This liquid dissolves the green matter 

 interspersed through the crystals, which acquire in consequence a 

 very fine ruby red colour. It now requires much more water to 

 dissolve it than before it was treated with alcohol. Its solution does 

 not crystallize, as it did at first, because the alcohol has removed 

 the excess of acid, which was very favourable to its solution and 

 crystallization. 



The solution of muriate of rhodium freed from the copper, iron, 

 and traces of palladium, which might still remain in it, forms with 

 ammonia a precipitate of a fawn yellow colour, granular, and but 

 little soluble in water. It is a submuriate of rhodium-and-am- 

 monia, as is evident from the vapours of sal ammoniac driven off 

 when the salt is heated.* The liquid from which this submuriate 

 had been separated preserves a pretty deep fawn colour, notwith- 

 standing the excess of ammonia. When heated, without being 

 boiled, it furnishes a new quantity of flocky precipitate of a brighter 

 yellow than what fell at first. When evaporated to dryness, and 

 treated with water, it still leaves a small quantity of a similar pre- 

 cipitate. All these precipitates were submuriate of rhodium-and- 

 ammonia. This shows that the salt is to a certain degree soluble 

 in water, and that an excess of ammonia favours the solution. 



Solubility. — Ammonio-muriate of rhodium dissolves very readily 

 in cold water. The solution has a reddish purple colour, similar to 

 that of cochineal, or the fresh juice of currants ; but heat renders 

 the colour brown, and, by keeping, it becomes brown without the 

 application of heat. 



This salt is granular, crystalline, and very brilliant. It is not 

 soft to the touch, like the submuriate of palladium-and-ammonia. 



IX. 



De.com position of Ammonio-muriate of Rhodium hj Potash. 



Two grammes (30-S8 grains) of the salt dissolved in water being 

 mixed with a solution of potash, a rose-coloured precipitate fell, 

 and ammonia \v;ts exhaled. In a short time the quantity of preci- 

 pitate diminished, and the liquid assumed a greenish yellow colour. 

 When heat was applied, the whole precipitate dissolved, the colour 



* This name agrees with it still better on this account, that the salt fiirnUhes 

 50 per cent, of metal when heated 5 while before being precipitated by ammonia, 

 it gave only 28. 



