38 Memoir upon Palladium mid Rhodium. 



riatic acid : this salt is an ammoniacal muriate of palladium at 

 the minirmim of acid, the properties of which will be presently 

 explained : in order to obtain the metal, it is sufficient to make 

 it red hot. 



Now, in order to obtain the rhodium, I evaporate sufficiently 

 the liquors from which the palladium has been separated, in 

 order that they may crystallize in a mass upon cooling : I allow the 

 water to drain off the crystals;, which are sometimes of two forms 

 and two colours ; some are in hexahedral laminae, and of a fine 

 ruby red ; and the others less num(^rous, in square prisms of a 

 yellowish green, which are the ammoniacal muriate of palla- 

 dium. The water which comes from these crystals is also of a 

 greenish-yellow colour, owing- to the copper and the iron. 



The crystals being drained, I pound them in a glass or porce- 

 lain mortar, and wash them with alcohol at 36^, which I leave 

 on them for four-and-twenty honrs, in a close flask^ frecjuently 

 shaking them. When the colour of the alcohol (a greenish 

 yellow) ceases to heighten, it is decanted off, and iVesh quan- 

 tities are applied until the last portions are no longer coloured, 

 or at least until they no longer present to the re-agents traces 

 of copper or iron. 



If some portiotis of palladium still continue with the rhodium, 

 they will be dissolved in the last washings with the alcohol, and 

 then the latter will give by spontaneous evaporation crystals in 

 long square prisms of a greenish-yellow colour. Among these 

 sometimes we may also remark some very minute crystals of a 

 ruby red, which are ammoniacal muriate of rhodium dissolved 

 by alcohol. The salt of rhodium is afterwards dried in the air : 

 it is of a beautiful red ; but as it might still contain some small 

 portions of triple salt of })latina, it may be dissolved in a small 

 quantity of water sliarpeued with a little muriatic acid. The 

 salt of platina, if there be any, will remain at the bottom of the 

 liquor, and it may be separated by decantation or filtration. In 

 order to procure the metallic rhodium, it is then sufficient to 

 evaporate to dryness the solution of its triple salt, and to make 

 it red hot in an earthen crucible : it yields a white metal break- 

 ing into a spongy mass^ the properties of which will presently 

 be shown. 



The above process, which is simpler and more precise than 

 Wollaston's, is founded, as we see, 1st, On the insolubility of 

 the ammoniacal muriate of palladium, even in water slightly 

 acid. 2dly, On the solubility in alcohol of the muriates of 

 copper and iron, and the insolubility of tire ammoniacal muriate 

 of rhodium in the same agent. 



§ IV. Properties of the /leidral ammoniacal Muriate of Pal- 

 ladium, or Submuriate of Palladium, — This salt is of a very 



agreeable 



