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SELECTED ARTICLES. 
350 milligrammes; consequently a capsule with 40 square 
inches of surface, containing about five ounces of water, and 
capable of being used for all chemical purposes, as far as the 
internal surface is concerned, would cost when finished 
but thirty francs at most, while if wholly of platinum, and 
thin as possible, it would cost two hundred at lesast. 
The second process which was employed was the use of 
an amalgam. A similar process has for a long time been 
in use for gilding by means of a mixture of mercury and gold 
and is an operation which succeeds very easily. It was 
therefore natural to try whether an amalgam of platinum 
would afford the same success. After having tried without 
success by several modes to prepare this amalgam, the fol- 
lowing was hit upon. Platinum sponge (made at a low tem- 
perature, so as to be obtained in as minute a state of division 
as possible,) was taken and lightly broken up between the 
fingers; it was then passed through a sieve of silk, and placed 
in a well cleaned iron mortar along with a certain quantity of 
mercury; the bottom of the mortar was then slightly heated, 
and the mixture rubbed up for half an hour without intermis- 
sion, under a chimney with a good draught; the mixture was 
then complete. The proportion which gave the best results 
were 100 of mercury for five of platinum. This mixture 
is heavy, pasty, and easily moulded in the fingers; by 
means of chamois leather we may express part of the mer- 
cury. 
Nevertheless, if we attempt with this amalagam, to cover 
different metals with platinum, it will be found that some ob- 
stinately refuse to receive this amalgam, as for example, iron 
and copper, while silver and brass are easily covered with a 
film of platinum. This operation is, however, very delicate; 
it succeeds tolerably well with the silver of any ancient coins, 
because the impression is shallow, and they can be heated 
with safety. But the platinum deposited in this way is darlo 
porous, hardens with difficulty, does not adhere well when 
the mercury has been driven off by a low heat, and if heated 
still more, it frequently penetrates the substance of the metal 
