SALTS OF RHODIUM. 695 



double salts. The solution in hydrochloric acid is also pale, 

 although it contains chloride of potassium, while a solution of 

 the double chloride prepared in the way formerly mentioned is 

 a fine red. Hence Berzelius infers that there are two isomeric 

 modifications of this oxide, of which the combinations, when in 

 solution, are respectively yellow and rose coloured. The hy- 

 drated rhodic oxide contains one atom of water, R 2 O 3 -{-HO; 

 two compounds of rhodic oxide with a protoxide of the same 

 metal or rhodous oxide, appear to exist, R 2 O 3 + 3RO and 

 R 2 O 3 + 2RO. The known compounds of rhodium are not iso- 

 morphous with compounds of platinum, but this may arise from 

 these two rnetals affecting combination in different proportions, 

 so that their compounds are not analogous in composition. Their 

 association and resemblance in other respects afford a strong 

 presumption of their being isomorphous bodies. 



Sulphuret of rhodium. Rhodium may be united with sul- 

 phur by either the dry or humid way. The sulphuret of rho- 

 dium was used by Wollaston to obtain the metal in a coherent 

 mass. 



Chloride of rhodium, R 2 C1 3 is obtained from the double chlo- 

 ride of rhodium and potassium, by precipitating the latter metal 

 by fluosilicic acid. The dry salt is of a brown black and not 

 crystalline, it requires a pretty high temperature to decompose 

 it, and then resolves itself at once into chlorine and rhodium. 

 This salt deliquesces in air ; its solution in water is of a beau- 

 tiful red colour. It appears to exist in combination with a 

 protochloride of rhodium, in the rose red powder obtained by 

 heating rhodium in a stream of chlorine, R 2 C1 3 + 2RC1. The 

 double chloride of rhodium and potassium, prepared by the action 

 of chlorine upon a mixture of rhodium and chloride of potas- 

 sium, is 2KC1 + R 2 C1 3 + 2HO. It retains this water at 212, 

 but loses it at a higher temperature, this salt rarely crystallizes 

 well, but its crystals according to Wollaston, are rectangular 

 four sided prisms, terminated by four sided pyramids. The 

 formula of the double chloride of rhodium and sodium is 3Na 

 C1 + R 2 C1 3 +18HO; it forms large prismatic crystals. Their 

 solution is of a beautiful rose colour. 



A sulphate of rhodium is formed when rhodium is ignited 

 with bisulphate of potash, it gives a yellow solution. Another 

 sulphate in combination with sulphate of potash gradually falls 

 as a white powder, when sulphurous acid is added to a solution 



