1. Silver is a metal of a fine white color, and, in brilliancy,
inferior to none of the metals except steel. In malleability, it is
next to gold, it being capable of reduction into leaves not more than
the 1/160000 of an inch in thickness, and of being drawn into wire
much finer than a human hair.
2. The relative value of silver and gold has varied considerably in
different ages. In the prosperous period of ancient civilization, one
pound of gold was worth twelve of silver. In Great Britain, the
relative value of the two metals is one to fifteen and one-fifth, and,
on the continent of Europe, it is about one to fifteen. In the United
States, the relative value of these two metals has been recently
established by Congress at one to sixteen. In China and Japan, it is
said to be one to nine or ten.
3. There are two methods of separating silver from its various ores,
and these are called _smelting_ and _amalgamation_. In the former
method, the ore and a due proportion of lead are heated together; and
the latter, from its great affinity for silver, unites with it, and
separates it from other substances. The two metals are afterwards
separated from each other, by melting them on a cupel, and then
exposing them to a current of atmospheric air, by which the lead is
converted into an oxyde, while the silver remains untouched. This
process is called _cupellation_.
4. In the other method, the first thing done is to roast the ore, to
expel the sulphur and other volatile parts. It is then reduced to an
impalpable powder by machinery; and having been sifted, it is agitated
sixteen or eighteen hours in barrels, with a quantity of quicksilver,
water, and iron, combined in certain proportions. This agitation
causes the several substances composing the _charge_, to unite
according to their respective affinities.
5. The silver and mercury combine, forming an amalgam, which, having
been put into a leather sack, a part of the latter is separated from
the rest by filtration, still leaving six parts of this metal to one
of the silver. The amalgam is next submitted to the action of heat in
a distilling furnace, by which the mercury is sublimated.
6. The value of the silver annually taken from the mines in all parts
of the world, is supposed to be about $20,000,000, of which Mexico and
South America yield the greater part. The several silver mines of
Europe and Asia produce about two millions and a half.