[ 63 9 ] 
one feparable by fire. The platina remaining a fter 
the feparation of the metals, proves unfufible as at 
firft. 
Platina perfectly refills the deftrudtive power of 
lead and bifmuth, and the rapacious antimonial femi- 
metal; which laft has been hitherto efleemed the 
fevered; teft of gold, fo as to have received the appel- 
lation of balneum J'olius foils , the bath which gold 
alone can fuftain, and in which it is wafhed from all 
kinds of impurities. 
Since therefore platina mixed with gold is not dif- 
coverable by any of the operations by which that 
metal is ufually afiayed or refined, or by the hydro- 
flatic balance ; we hope that thefe papers, which 
contain part of the hiflory of this extraordinary and 
hitherto unknown mineral, and the methods of dif- 
tinguilhing any fophiftications of gold made by its 
means, which might otherwife have pafled undif- 
covered, will be candidly received by this illuftrious 
body, as a means of promoting that kind of know- 
lege, for which the Royal Society has been ever 
eminent, and peculiarly inftituted. 
LXXXVIL 
