[ 5°5 ]

It does not appear from these experiments, that anypart of the platina was truly vitrified. We may ratherconclude, that the disappearance of the platina in the twolast experiments was owing to its being diffused throughthe mass in a state of powder too subtile to be distinguish-ed : the colour of the glass cannot be ascribed to the pla-tina, since No. 3. afforded colours more considerable,though the grains of platina remained unaltered.

6. In my experiments, No. 1 and 2, particularly in thelatter, the platina, though it had been attenuated by solu-tion and precipitation before its mixture with the vitresci-ble ingredients, separated from the glass in fusion, and wascollected into very sensible particles, some of which wereof considerable magnitude. In an experiment of Mr. Mac-quers, this effect was still more strongly marked. The redprecipitate of platina made by alcaiies was mixed on a por-phyry stone with a flux composed of one dram of calcinedborax, one dram of creme of tartar, and two drams of awhite glass, which he had himself prepared from six partsof white sand and eight parts of borax : the proportion ofthe precipitate of platina to this flux he does not specify.The mixture was urged with the fire of a forge, animatedby several bellowses, for thirty-five minutes, and the matterbeing then in good quiet fusion, it was suffered to cool.The upper part of the mass was a blackish glass : at thebottom of the crucible was found a well collected lump ofplatina, pretty brilliant and smooth on the surface, weigh-ing ninety-six grains. This lump had all the appearanceof a metal that had received a very good fusion : neverthe-less, on trying to extend it under the hammer, it broke intwo pieces, and shewed an oval chamber or cavity in themiddle : the fracture resembled that of large-grained brit-tle iron: in hardness it was nearly equal to forged iron,for it scratched deeply gold, silver, copper, and even iron

itself.