1811.] Imperial Institute. 309 



After having precipitated the greatest part of the platinum from 

 the oitro-muriatic acid solution by means of ammonia, he puts into 

 the residue plates of iron, which throw down the other metals. 

 Employing in succession cold nitric and muriatic acid, and then 

 subliming, he separates from the precipitate the greatest part of its 

 copper, mercury, and osmium, and likewise of the iron which is 

 mixed with it. A little of the remaining platinum, of the palla- 

 d'tim, and even of the osmium, is removed by the same acids, 

 because they have precipitated in the state of oxide ; for in the 

 metallic slate they would not have been acted on. On the other 

 hand, some copper and iron still remain, because they are inti- 

 mately united with the other metals, and defended by them. To 

 get rid of all the remains of the platinum, M. Vauquelin dissolves 

 the whole again in nitro-nuniatic acid, and precipitates by ammonia. 

 He obtains a yellow and pure salt of platinum. Evaporating the 

 residue to dryness, and treating it with water, there remains a red 

 salt, consisting chiefly of platinum. Thus the liquid is almost 

 completely freed from that metal. The aqueous solution is then 

 diluted with water, and a little acid added. Some ammonia is then 

 added, but not enough to saturate the acid ; the whole is agitated ; 

 there immediately appear a great number of brilliant and beautiful 

 red needles. They consist of the ammonio-muriate of palladium. 

 When heated to redness, pure palladium is left behind. If a little 

 iron and rhodium should be present, they may be separated by 

 digesting in water slightly acidulated with muriatic acid. The 

 residue of the liquor contains the rhodium, and some remains of 

 palladium, copper, and iron. To obtain the rhodium, the liquid 

 is made to crystallize. The crystals are reduced to powder, and 

 freed from the salts of copper, iron, and palladium, by washing 

 them repeatedly with alcohol. If any salt of platinum remain, it 

 may be separated by means of water slightly acidulated with 

 muriatic acid. Finally, by a last evaporation, the salt of rhodium 

 remains of a magnificent red. When heated to redness, this salt 

 leaves the metal in a state of purity. 



We cannot by a more ingenious or simple method separate so 

 many substances from each other, which are held together by such 

 a powerful attraction. It is founded chiefly upon the insolubility of 

 •mmonio-muriate of palladium in water, even when acidulated with 

 an acid ; upon its precipitating as soon as it forms ; and upon the 

 insolubility of the ammonio muriate of rhodium in alcohol, while 

 that liquid dissolves the muriates of copper and iron. 



W liih M. Viitiqnelin was thus engaged in examining these two 

 metals united to platinum, M. Laugier, his colleague in the 

 Muteam of Natural History was occupied with a third of them, 

 and perhaps the most curious of all, o\miiim, the oxide of which is 

 Volatilized at the heat of boiling water, give- no colour to distilled 

 water, ha- even the same appearance as water to the eye ; but gives 

 out a strong odour, and acts upon the olfactory nerves in mcl) a 

 manner as to alter the tense of smelling for several days. These 

 properties, and several others, made chemist! regret that it was so 



