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os platlna so as to form a thin plate oft the bottom of alarge cupel. Much of the lead exudes at first in a vitreousform, and glazes or stains the dish or cupel on which theplate is exposed to the fire; but towards the end it seemsto be forced out only in fume, no visible mark remainingon the vessel: in one experiment, the metal lost about atwenty-fifth part of its weight, after it had ceased to giveany tinge to the cupel.

19. It may be proper to observe, that in most of thecupellations of platina with lead, especially where thequantity of the mixt was considerable, and a pretty strongfire made use of, the cupelled plates appeared of a regularand singular figure on the surface, such as no other metalor metallic mixture I know of assumes in fixing. In themiddle was a broad flat-bottomed depression, with a lip ormargin round it, like a common table plate; and the lipwas frosted as it were with regular transverse rows of pro-minent dots. The smooth parts were in general soft orslippery to the touch.

VII. Cupellation of platina with Bismuth.

Mixtures of platina with bismuth were submitted tothe common processes of cupellation under a muffle, sco-rification in assay crucibles, and testing before the nose of abellows. The general event was nearly the same as whenplatina and lead were treated in the same manner: themixtures, which at first flowed easily, became less and lessfusible in proportion as the bismuth was driven off, and atlength could not be kept fluid in an intense sire, thoughthey appeared, on weighing, to retain a considerable quan-tity of the bismuth. Nor could bismuth, any more thanlead, be worked off clean, by the common process of cu-pellation, from mixtures of platina with fix times itsweight of either gold or silver.

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