520 PHILOSOPHICAL TRANSACTIONS. [aNNO 1754. 



6. A mixture of 1 part of platina and 3 of gold was cupelled with lead, under 

 a muffle. The matter drove well for a considerable time ; at length it collected 

 into a bright hemispherical lump, which by degrees became flatter, dull, and 

 rough. The button, on being weighed, was found to retain a considerable 

 portion of lead. 



The experiment being repeated with a mixture of 1 part of platina and 6 of 

 gold, some part of the lead was still retained. The bead proved rounder and 

 brighter than the foregoing, and of a good golden colour on the outside : it 

 broke easily under the hammer, and appeared inteinally greyish : some of the 

 fragments hung together by the outer golden coat. 



7. Mixtures of platina and silver, submitted to cupellation, retained likewise a 

 considerable quantity of the lead. These, in becoming consistent, formed, not 

 a hemispherical bead, but a flat mass, very rough, and brittle, and of a dull 

 grey colour both internally and externally. 



Cupellation and Scorification of Bismuth with Platina. 



Mixtures of platina with bismuth, a metallic substance, in some respects more 

 active than lead, were cupelled under a muffle, scorified in assay -crucibles, 

 tested before the nose of a bellows. In numerous repetitions of these experi- 

 ments, the event was the same as when lead was made use of. ' The mixtures, 

 which at first flowed easily, became less and less fusible, in proportion as the 

 bismuth was driven off; and at length could not be kept fluid in an intense white 

 heat, though they appeared, on weighing, to retain a considerable proportion of 

 the bismuth. Nor could this semimetal, any more than lead, be entirely sepa- 

 rated, by cupellation, from mixtures of platina with either gold or silver. 



Platina cupelled with bismuth, differed little in appearance from that which 

 had been treated in the same manner with lead. The button was more spongy, 

 and specifically lighter. 



3. Difflation of Regulus of Antimony with Platina, 



A mixture of platina and regulus of antimony was melted, by a strong fire, in 

 a shallow wide crucible, and the nose of a bellows directed obliquely on the sur- 

 face. The matter continued to flow, and fume copiously, for some hours ; at 

 length it became consistent in an intense white heat, and scarcely emitted any 

 more fumes, though strongly blown on. The mass, when become cold, broke 

 easily, appeared very porous, blebby, of a dull grey colour, and weighed consi- 

 derably more than the quantity of platina employed. 



Platina was likewise treated with crude antimony : and the regulus obtained 

 from this mixture, difflated as the foregoing, with the same event ; the platina 

 ■not only resisting the antimonial semimetal, but likewise defending a part of it 

 from the action of the fire and air, and refusing to melt, after a certain quantity 

 had been dissipated. 



