418 OF COBALT, he. 



weight of pure platina in aqua rcgla, with tfie' 

 addition of thirty-four pounds of iterated minr- 

 ntl alkali, alVordcd upon the infuiion of a quanti- 

 \y ofcauilie alkali, thirty. fix pounds of precipi- 

 tate, all hough the utmoll care had been taken to 

 have the folution compleatly faturateit. ft fol- 

 lows therefore, that the other two thirds of the 

 metal were taken up in the neutral fait formed 

 at the precipitation; as the parts of the platina 

 that were diilolved, could not but be of the fame 

 bulk and fupcrficies as thofe which were preci- 

 pitated. 



To afcertain the caufe of this phenomenon 

 more fully, I refolvcd to try tin? fame ex peri- 

 nient on platina with other metals, inlleadofthe 

 alkali which I had uied. I accordingly diilolved 

 an hundred weight of pure platina in aqua regia ; 

 and then poured into the folution, after d ihifiivy; 

 it in diitillcd water, as much zinc in final I thin 

 plates, as it would diilolve. No lefs than 416 

 pounds of the *inc, were diflblved, with a con- 

 ilant ertcrvcfccn.ee, although the menftruumhad 

 hccit previoufly faturated with platina to fitch a 

 degree that it would not duTolve another grain of 

 that metal. 



Meanwhile, as the zinc was diflolving, the 

 black flaky matter fubilded to the bottom of th? 

 veflel. Tliis relidue, when waihed and dried, 

 \vas f(Hind to weigh 77 pounds. And when ex- 

 pofc-d to the blow-pipe, lirit exhaled ah afh-co- 



lourecl 



