C 678 ] 
kinds of operations. The amalgam, which looked 
very bright, left, upon evaporation, a fpongy mafs, 
of a high colour, which being melted, and poured 
into an ingot, proved very foft, extremely malleable, 
and in all refpedts refembled the pure gold made ufe 
©f, without the lead: appearance of platina. 
Remark. It is greatly to be wilhed, that this me- 
thod of purifying gold from platina may prove fuf- 
ficiently accurate to exactly determine the quantity 
of each in the mixt. The experiments hitherto 
made do not fufficiently clear up this point ; a great 
number are dill neceffiary before it can be fully alcer- 
tained. 
2. With Bifmuth, 
Equal parts of platina and bifmuth, inje&ed into 
a mixture of black flux and common fait, previoufly 
brought into fulion, and urged with a quick fire, 
drongly excited by bellows, melted perfectly in a 
few minutes, and differed very little lofs. Without 
thefe precautions, the bifmuth could fcarce be made 
to take up above one-third its weight j great part of 
which, on an abatement of the heat, fubfided. 
Mixtures of platina with different proportions of 
bifmuth proved dll, like the bifmuth itfelf, extremely 
brittle : One was not remarkably more fo than an- 
other. To the file, they were fcarce harder than 
pure bifmuth. They broke of an irregular furface, 
compofed chiefly of driae, with fome plates. When 
newly broken, they looked bright and fparkling ; ex- 
cept the compofitions with a large proportion of pla- 
tina, which were of a dull greyifh colour, without 
any brightness. They all tarnifhed flowly in the 
air. 
