560 Remarks on M. Baruel's Process 



The separation of the salt of rhodium from those of platinum 

 and palladium, as performed by Dr. WoUaston for the instruc- 

 tion of his scientific friends, is one of the most striking pheno- 

 mena of chemical analysis. He mixes the three triple salts with 

 a little water, in a watch glass, and evaporates to such a degree 

 as leaves the mass apparently dry, yet with as much combined 

 water as would give it the watery fusion at a higher heat. He 

 pours on this a little alcohol, about specific gravity 0.850, and 

 applies a gentle heat. Instantly after fusion, two very distinct 

 and dissimilar fluid strata are formed ; a red-coloured liquid 

 above, and an oily-consistenced liquid below, of a dark-brown 

 colour. The former is to be immediately poured off. The latter 

 after being washed with a little more alcohol, yields a pure soda- 

 muriate of rhodium. 



The plan of separating palladium from its metallic associates 

 lathe platinum ore, originally invented by Dr. Wollaston, is very 

 beautiful, and certainly in no respect inferior to that prescribed by 

 M. Vauquelin. " To a solution of crude platina, whether ren- 

 dered neutral by evaporation of redundant acid, or saturated by 

 addition of potash, of soda, or ammonia, by lime or magnesia, 

 by mercury, by copper or by iron, and also whether the platina 

 has, or has not, been precipitated from the solution by sal- 

 ammoniac, it is merely necessary to add a solution of prussiate 

 of mercury, for the precipitation of the palladium. Generally 

 for a few seconds, and sometimes for a few minutes, there will 

 be no appearance of any precipitate ; but in a short time, the 

 whole solution becomes slightly turbid, and a flocculent precipi- 

 tate is gradually formed, of a pale yellowish-white colour. This 

 precipitate consists wholly of prussiate of palladium, and when 

 heated will be found to yield that metal in a pure state, amount- 

 ing to about four or five tenths per cent, upon the quantity of ore 

 dissolved. 



" The prussiate of mercury is peculiarly adapted to the pre- 

 cipitation of palladium, exclusive of all other metals, on account 

 of the great affinity of mercury for the prussic acid, which in 

 this case prevents the precipitation of iron or copper ; but the 

 proportion of mercury does not by any means influence the 



