J74« ACTION OF PLATIffA AND MERCURY, 



^ more rapidly, and the precipitate is more abundant. The pre- 

 cipiUtion of muriate of plalina by nitrate of fiiver, and the 

 combination which enfaes irom it, fuggefted to me an experi- 

 ment which I miift ftate at length, as from the refult of it 

 confequences are dediice<l which modify forae of the experi- 

 ments of my former Paper. 

 Mercury dif- ^ Jt occurred to me that a method of uniting platina^and 

 Smulii'ott^xldl' ^^"^^^U without the intervention of any other metal, orof any 

 tion will fall ina fubflance but the folvents of thefe metals might be accom- 

 triple f.lt with ijQ^^j ^5 jj^ jjjg ^^j-g ^^- ^^j^^^^j. ^^j piatina. I therefore poured 



platir.a without /- , . . , . . 



any addition of 3 folutlon of nitrate of mercury, which folulion being at the 



fulph. iron. minimum of oxidizement, confequently formed an infoluble 



muriate with muriatic acid, into a folutlon of muriate of piatina. 



The refult was a triple fait of piatina and mercury, which 



when the mercury was completely and totally at the minimunx 



of oxidizement was nearly infoluble. To procure it in this 



flate it is fufficie»t to put more metallic mercury into dilute 



DJtric acid than the nitric acid can diffolve, and to boil them 



together. This triple fait of piatina and mercury (hall be pre- 



fcntly examined. From this it is evident than to produce the 



union of piatina and mercury, the latter being at its minimum 



of oxidizement in nitric acid the addition of green fulphate of 



iron is fuperfluous. 



^ot fo if the But if mercury be raifed to its maximum of oxidizement in 



jrasrcury be at tijtric acid the cafe is different, for no precipitation occurs tiU 



the maximum of ri. r ' jiit^ 



oiidizement. l"e green fulphate of iron is added. The molt advanta- 

 geous method for precipitating piatina and mercury hy green 

 fulphate of iron is, I believe, the following. Mix a folution 

 of piatina with a folution of green fulphate of iron, both 

 I *varnn, and add to them a folution of nitrate of mercury 



at the maximum of oxidizement alio warm. It is neceffary 

 to avoid excefs of acid, fplt, &c. in this as in all fuch cafe.'». 

 With due care the precipitation of both metals will then be 

 complete. 

 \Vlieih;r mcr- . By comparing the experiments made with mercury and 

 *^-"^^ 1^ V^t'*. platiiia with thofe made with tilver and piatina, a ftriking 

 h\ green I'llphate refemblance will be found. This induced me to purfue the 

 p! iron ? Se::. analogy, and to examine whether, independently of the aftion 

 of piatina, mercury had not the fame property of being preci- 

 pitated by green fulphate of iron as fllver. Nitrate of lilver is 

 . prerlpltated by green fulphate of iron, but muriate of 61ver is 



not 



