121 Experments on Platina, 



Exper. IV. An acid, compofed of 



2 ounces of nitric acid and 



14 ounces of muriatic acid, 



diflolvcd 13 drams and 38 grains of platina. 



Thefe four experiments were made at the fame degree of 

 heat ; that is to fav, in four retorts, difpofed according to 

 my mode on wire grates, and placed on a furnace. That the 

 refults may be more eafily compared, I fhall here give them 

 in the following table: 



Let us now fee the confequences which may be deduced 

 from this table. 



ift. In the three firft experiments it is obferved that the 

 quantity of platina diflblved increafes in proportion to that of 

 the muriatic acid, from which it refults that this acid is the 

 real folvent of platina. 



ad. If we fuppofe that the twelve ounces of muriatic acid, 

 found in the four ounces of nitric acid the quantity of oxy- 

 gen neceflary for difToh'itig the platina, it is feen that a con- 

 fiderable excefs of the latter was ufelefsly expended in the 

 two preceding experiments ; that is to fay, 4 ounces too 

 much in the firft, and 2 in i.he feconcl ; and, by the fame 

 reafon, the folutions of the firft and fecond experiments were 

 more acid than thofe of the third and fourth. 



3d, Acids, the ftrength of which is in a fimilar proportion, 

 or nearly three parts of muriatic acid for one of nitric acid, 

 muft form the propereft proportion for dilTolving crude pla- 

 tina, and confequently purified platina. 



4th, The fourth experiment proves to us that the nitric 

 acid, which was in the proportion of only l-7th of the mu- 

 riatic acid, was not able to furnifh to the latter the quantity 

 of oxygen neceflary to make it charge ilfelf with all the pla- 

 tina which it ought to dilTolve ; hence it refults, that in this 

 laft proportion there is a lefs foKition of platina, and a lo Cs 

 of muriatic acid. 



5th, As 



