[ 502 ]

tered the liquors twice through double papers, and thenadded by degrees spirit of salt to neutralize the alcali: atfirst: a brownish precipitate fell, and afterwards a white onelike the common precipitated sulphur. A little of thebrown precipitate was heated in a small scorifying dish,and some nitre added to burn oft' the sulphur more effect u-ally: there remained on the diffi several bright particles likeplatina, sprinkled all over its surface, 'she rest of theprecipitate being burnt in like manner, I added some purelead, to collect the dispersed particles of the platina, andafterwards worked off the lead in a cupel: it left a roughbrittle bead, exactly like those obtained in cupelling crudeplatina with lead, of which an account will be given here-after in the seventh section. It seems to follow from theseexperiments, that hepur fulphuris really diffblves platina,though very difficultly, and very sparingly.

XI. Platina ivith earthy bodies.

Certain earthy bodies are found to promote the fusion,not only of some metallic minerals, but in some instances,of the purer metals also : thus forged iron, which couldnot be made to melt in a crucible without addition, wasbrought into fusion by surrounding it with gypsum orplaster-of-paris, a fact which we owe the discovery of toMr. de Reaumur. To see if platina would be anywiseaffected by substances of this kind, I intermixed an ounceof it with gypsum, and urged it with a strong fire in ablast furnace for two hours : the Hessian crucible wascorroded in many parts to the thinness of paper, and hereand there quite through, the matter of the crucible andthe gypsum having in some measure vitrified together;but the platina remained unmelted, and unaltered.

Quicklime, and calcined flint, were likewise made trialof in the same manner, but no change was produced bythem in the platina.