\ 



Experiments .oil Plaiina: 1 21 



continuing the fire. Thcfe movements arlfe from the union 

 ot it yellow powder, which as yei is only the pntaflied mu- 

 rsate of platina of which we have jult ipoken, and which it 

 is indifpenfably neceflary to feparate. In regard to the laoll 

 expeditions means of heating a retort which contains 12 or 

 i5 pounds of tr.atter, and of maintaining the heat, a fupport 

 of wire ought to be preferred to fand-baths, which I have lon»- 

 banifncd from my laboratory, even in the preparation of 

 icthcr, the rc6lilication of acids, &c. 



But when it is necrffiiry to operate on a great fcale with a 

 certain number of vedels, it is evident that fand-baths placed 

 in a roiv in a gallery will in this cafe be attended with more 

 certainty. 



XIV. Of the Compojihon of the Nitro-muriatic Acid for the 

 Solid ion of crude Platina, 



No author has find any thing pofitive in regard to the pro- 

 portions uhich will yield the ftrongetl nitro-muriatic acid 

 f«r this kind of labour. This uncertainty, which flopped me 

 during my firft refearches, induced me to endeavour to dif- 

 cover thefe proportions by direft experiments. 



As the ftrength of acids varies in the different manufac- 

 tories, it appeared to me proper to take them at that deoree 

 of concentration at which they are commonly found in the 

 {Imps. I confined myfelf therefore to aquafortis of ^^ de- 

 grees by Baume's areometer, and muriatic acid of 15 de- 

 grees, without giving myfelf any trouble about the nitric acid 

 w hich might be prcfent in the muriitic acid, or the iron and 

 the fidpluiric and fuiphurous acids with which common mu- 

 riatic acid is olten contaminated : for, if I had employed in 

 my rcfcurchcs rectified acids, it is evident that my refults 

 could not be applied but with reftriftion to operations on 

 platina on a large fcale, in which cafe it will always be ne- 

 ccli.iry to employ the acids of commerce. 



K.-eper. i. One pound of nitro-muriatic acid, compofcd of 

 8 ounces of nitric acid and 

 8 ounces of muriatic acid, 

 dilfolved 13 drams of platina out of 24 which I employed. 

 Exper. II. Nitro-muriatic acid, eonipofed of 

 8 ounces of nitric, acid and 

 10 ounces of muriatic acid, 

 dilTdUeJ i^ drams of jilatina. 



Exper. III. An acid, compofcd of 



4 ounces of nitric acid and 



10 oimecs of niurialic acid, 



diffolvcd 17 drams am! 54 grains of platina. 



Expcf. 



