C 679 ] 
air, to a dark yellowifh, purplifti or bluifh colour i 
Several acquired in part a fine deep blue, which has 
fuffered no change in above a twelve-month > fome 
parts of the maffes ftill remaining white as at firft, 
and others inclining to purple. 
3. With Zinc. 
Upon an ounce of platina, covered with borax, 
and heated in a blaft furnace to a ftrong white heat, 
was injected an equal quantity of zinc. A violent 
deflagration arofe, and the platina was almoft in- 
stantly diflolved : The matter, immediately poured 
out, was found to have loft near half an ounce. 
Upon feveral times repeating this experiment with 
different proportions of the two metals, both in a 
quick fire, and in one more gradually raifed in a 
wind furnace, the zinc was conftantly found a 
powerful menftruum for platina, but fuffered great 
lofs from the heat requifite for rendering the mixture 
Sufficiently fluid. When fo much of the zinc had 
been diflipated, that the remainder amounted to no 
more than one-fourth of the platina, the compound 
ftill continued fluid enough to run freely into a long 
mould. 
Compositions of platina and zinc differed little in 
appearance from zinc itfelf ; except that where the 
quantity of platina was large, they were of a clofer 
texture, and a duller hue, with rather more of a 
bluifh caft. They did not tarnifh, or change their 
colour, on being expofed for feveral months to the 
air, in a dry room. They were harder to the file 
than the zinc at firft, and fell in pieces under the 
hammer l. 
