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General Remarks. 
Platina melts with equal its weight of each of the- 
metals 5 with one more readily than with another. 
With fome it becomes fluid, if the proportion of the 
platina is not large, in a moderate fire 5 but a ftrong 
one is conftantly requifite for its perfedt folution. 
Compofitions of filver, copper, lead, with about one- 
third their weight of platina, which had flowed thin 
enough to run freely into the mould, and appeared 
to the eye perfedly mixed, on being digefted in aqua 
fortis till the menftruum ceafed to adl, left feveral 
grains of platina in their original form. Upon view- 
ing thefe with a microfcope, fome appeared to have 
fuffered no alteration 5 others exhibited an infinite 
number of minute bright globular protuberances, as 
if they had juft begun to melt. 
Platina hardens and ftiffens all the metals ; one 
more than another, lead the moft. In a moderate 
quantity it diminifhes, and in a large one deftroys, 
the toughnefs of all the malleable metals ; but com- 
municates fome degree of this quality to call iron. 
Tin bears much the lead, and gold and filver the 
greateft quantity, without the lofs of their malleabi- 
lity. 
A very fmall proportion of platina fcarce injures 
the colour of copper and gold : A larger renders both 
pale : A far lefs quantity has this effect upon copper 
than on gold. It debafes and darkens, in proportion 
to its quantity, the colour of the white metals j that 
of filver much the leaf!, and of lead the moft. It 
in good meafure preferves iron and copper from tar- 
nifhing in the air ; fcarce alters gold or filver in this 
reipedt j makes tin tarnifli loon, and lead exceeding 
quickly. 
4 Q - 2 
PAPER 
