[ 33 } 



IX. Memoir vpon Palladium and Rhodium. By M. Vau- 



QUELIN*. 



After detailing the histoiy of the discovery of palladium and 

 rhodium, M. '/aucjuelin {jroceeds : 



§ I. Ttie following is Dr. Wollaston's process for sepa- 

 rating tliese. two metals from the solution of platina : he dis- 

 solves 111 the nitro-niuriatic acid two ounces and a half of pla- 

 tina ore, he precipitates the platina by sal ammoniac from a 

 portion of tiils solution, corresponding to 1000 grains of ore; 

 he pluu'.^es in the mother waters and the washings of the salt 

 of platina, united, laminae of zinc for precipitating the metals 

 in question. But as there is in these mother waters, copper, 

 and sometimes lead, which are precipitated by the zinc at the 

 same time with the rhodium and palladium, M. Wollaston takes 

 them up by means of aqua fortis, which does not attack the 

 other metals. 



He dissolves the residue in the nitro-muriatic acid, precipi- 

 tates once more bv sal ammoniac the little platina -vshich is in 

 it, adds to the solution, when thus precipitated, 20 grains of 

 sea-salt, evaporating to dryness, and washes the residue with 

 alcohol imti. the latter comes ofi" colourless. By these means he 

 dissolves tht tripie salt of palladium, and leaves that of rhodium. 



Although M VoUaston caly operated upon 1000 grains of 

 platina ore, an^. had at hh disposal, of each of the metals, 

 only si < or seven grains at most, he nevertheless ascertained 

 their chief properties ; which does infinite honour to his aaga- 

 city, for it seemed almost incredible. 



For my part, I confess that although I employed about sixty 

 marcs (fifteen kilogrammes) of platina ore, I experienced many 

 difficulties in separating exactly the palladium and rhodium 

 from tiie platina and the other metals which are in this ore, 

 and ; articulariy in obtaining them very pure. 



§ Ii. The first condition favourable to the solution of pla- 

 tina in the ore, and its precipitation, relates to the proportion of 

 the acids which ought to compose the solvent : that which ap- 

 peared to be the best is one part of nitric acid to two of mu- 

 riatic acid : this a([ua regia so composed, independently of 

 its dissolving a greater quantity of platina, gives a saving in 

 price of nearly cent, per cent., an object which ought not to be 

 overlooked when large qiunitities of phvana are to be dissolved. 



The second condition refers to tl'.e concentration of the acids: 

 the quantity of nitrc-nmriatic ;.ci(l neces.'^ary for dissolving the 

 platina, does not decrease merely iu the ratio of its concentra- 



* Annalcs de Cfiiiire, tome Ixxxviii. p. 107. 



Vol. 44. No. 195. Jul// 1814. C tion, 



