Memoir upon Palladium and Rhodium. 37 



cessive action of great quantities of nitric and muriatic acids, 

 each of the above three S'jhitions in the nitro-muriatic acid still 

 contained copper and iron; which proves that these metals in 

 precipitating are united to the platiiia, and to the other metals 

 mixed with it ; and that it is by this union that thev are pro- 

 tected from the action of tlie simple acids, and even from the 

 first portions of nitro-muriatic acid. 



I had alrea'iy observed thcoC phaenomena in a previous ope- 

 ration ; but ao I had calci::ed the precipitate pretty strongly in 

 order to agglutinate its parts, I thought that this had operated 

 betvve?n the metals a commencement of union, which had formed 

 an obstacle to the solution of the iron and copper. But the 

 above result announces that this combination takes place at the 

 moment of precipitation. One thing not less remarkable is the 

 great quantity of iron which is precipitated in the state of oxide, 

 with a portion of platina, palladium, and rhodium, probably in 

 the same state. 



The three solutions of the precipitate were joined, and eva- 

 porated into a syrupy consistence, in order to drive off the ex- 

 cess of acid : afterwards the liquor, sufficiently diluted with water, 

 was precipitated by the muriate of ammonia, when a salt of 

 platina of a pure yellow colour was obtained. 



The liquor once more evaporated, almost to dryness, and the 

 residue taken up by water, left a salt of a red colour, not very 

 soluble in water, and wliich was still mostly formed of platina. 

 We shall account for the colour of this salt by and by. 



The following is the jKocess wliich I adopt for separating the 

 palladium from the rhodium, and the latter from trhe iron and 

 cojjper with v,-hich it is alwavs mixed. 



1 dilute with water the above liquor deprived of the greater 

 part of the platina: I add muriatic acid when there is not 

 enough : afterwards I gradually pour in ammonia, so as not to 

 saturate entirely the excess of acid; I shake it; and instantly a 

 great quantity of salt makes its appearance in the form of fine 

 sparkling needles, and of a beautiftil red colour. 



I allow it to deposit : I try a portion of the clear liquor with 

 some drops of ammonia : if it still yields salt as it did at first, 

 I add fresh quantities of this alkaii until it ceases to furnish 

 any. 



Then I allow the salt to deposit 5 I decant the liquor, and 

 wash the precipitate, first with cold water and afterwards with 

 hot water, which is not injurious, for it is of verv difficult so- 

 lution. If by accident I have exceeded the proper degree of 

 precipitation, and there are deposited with the red salt some 

 particles of iron or of rhodium, it may be easily cleared of it by 

 digesting it a few minutes in Avater slightly acidified with mu- 

 C 3 riatic 



