1814.] On Palladium and Rhodium. 275 



of the liquid became more intense, and much ammonia was disen- 

 gaged. There was an excess of potash in the liquid. 

 ° This solution, left to itself for some days in an open vessel, yielded 

 fawn yellow crystals. They probably consisted of potash-muriate of 

 rhodium dissolved by an excess of alkali. What seems to prove 

 this is that, when the excess of potash is saturated with muriatic 

 acid, a yellowish white precipitate appears, which is but little soluble 

 in water. It is a neutral muriate of rhodium-and-potash. 



X. 



Reduction of the Ammonio-muriate of Rhodium. 



Fifteen grammes of this salt strongly heated in a forge in an 

 earthen crucible yielded 4-2 grammes of a white metal, which had 

 not been melted, but all the parts of which were agglutinated 

 together into one mass. In another experiment ten grammes of the 

 salt yielded nearly three grammes of metal. Hence the salt contains 

 28 or 29 per cent, of metal. 



Desiring to know if this metal could unite to sulphur, and in 

 case it could, how much sulphur was requisite to convert it into a 

 sulphuret, I mixed four grammes of the triple salt with an equal 

 weigbt of sulphur, and exposed the mixture for a few minutes to 

 the heat of a forge. I obtained a button completely melted, of a 

 bluish white colour, and weighing 1 4 gramme. We see here that 

 the rhodium had combined with sulphur. Hence the complete 

 fusion and the uddition of weight, which otherwise would not have 

 been more than 1*12 gramme. Hence the sulphuret of rhodium 

 contains 2G per cent, of sulphur. 



The sulphuret of rhodium, exposed to a strong heat in the open 

 air, exhales sulphurous acid, and becomes rough on the surface. 

 After the process the metal is white, spongy, and brittle, and 

 weighs onlyVl gramme. 



Fusibilky. — Rhodium appears to be the most infusible of all 

 known metals. Half a gramme of this metal, obtained from the 

 Hlbmuriate, decomposed at a moderate heat, and therefore black, 

 was heated fur a long time on charcoal, the combustion of which 

 was supported by oxygen gas ; yet it wai not melted. Its parts only 

 cooglutinated into a single mass, having the colour of silver. I 

 have repeated this process several times with still smaller quantities 

 of metal, without beiog able to melt it completely. This metal 

 then, though brittle, is more difficult to melt than palladium and 

 platinum, which ate easily fused by a lire supported by oxygen gas. 

 This iufuiibility prevented me from determining the speeitic gravity 

 of the metal. 



We may say then that pure rhodium is a metal which has a 

 white colour not much different from that of palladium. It U 

 brittle, and more difficult to melt than any other metal, 



B 2 



