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tina to vitreous bodies at the end of the following section.The matter on which the powdery precipitate was exposedto the focus of the burning concave, might also have con-tributed to the vitrification ; what this matter was, the au-thor does not mention.

The experiments of this section point out some strikingdifferences between platina and gold; not only in thepower of producing, when dissolved, a purple colour withtin, and communicating a like stain to different kinds ofcolourless subjects, a power for which gold is remarkable,and which platina wants; but likewise in properties moreimportantly characteristic, as they afford means of dis-tinguishing and. parting the two metals when blendedtogether;. They have strewn platina separated in partfrom its solutions, by a substance which does not at allseparate gold, to wit,, sal ammoniac; and gold separatedcompletely by substances which do not at all separate pla-tina, viz. the mineral alcali, vinous spirits, essential oilsand æther. It appears likewise from these experiments,that besides the black dust which remains behind in thedissolution of platina, the part dissolved is not pure pla-tina; for the blue colour produced by the Prussian, algal!amounts to a proof that the solution contains iron.

S E C T. IV.

Platina exposed to firong fires, with saline, inflammable ,sulphureous, vitreous and. earthy bodies..

H AVING seen the effects of the purer acids on pla-tina,. and; the general properties of its solutions, we.shall proceed to apply, to it what are commonly calledfiuxesi and dry menstrua^ that is, substances which eitherbarely promote the fusion, of metals without corrodingthem*, ar which corrode and unite with them, when pro-perly