American citizen. [volume] (Canton, Miss.) 1864-1890, 1874-12-05
Silver.


alone in nature; its richest and most
abundant ore is one in which the noble
silver is held in chemical union with pie
bcian sulphur, the two forming a mineral
with II blacklist dark gray color, contain
ing in every 100 pounds, when pure,
about eighty-seven pounds of silver.
This metal is also the common compan-
ion of lead, and much of the precious
substance is obtained from galena. 1t
is said that when this ore of lead con-
tains as little as two parts of silver in a
thousand of ore the silver can be profita-
bly, extracted.
Much is known concerning the ancient
uses OF silver and gold very little con-
corning the ancient methods of extract
ing them from their ores. But 1t is in
teresting to know that as far as can be
learned, the principles upon which the
ancient process was conducted were not
very different from those employed at
the present time. Advance in this art
seems to have consisted less in the dis
covery of new principles than in the i'm
provement of methods based upon those
already known. Crude and wasteful
presses have been supplanted by others
more elegant, more economic and more
exact.
Not to describe now the processes
adopted where silver is to be reduced
from its ores on a large scale, let our
purpose be to sketch an outline of that
adopted by the chemist when he is called
| upon to decide the value of an ore. 1t is
the assay by fire"
A few grains of the ore finely pow
| dered and mixed with several times its
| weight of pure lead is placed in a re-
| fractory earthen cup already in a fur
mace and glowing with bright red heat
Quickly the lead melts and the ore may
| then<ee~seen floating upon its surface
| \ current of hot air sweeping over the
surface of the bath furnishes an abun-
dance of oxygen, which quickly takes the
place of the sulphur in the ore, and COM
| bines also with a portion of the melted
lead. This new compound of lead and
oxygen vigorously attacks the ore, SEXES
the baser metals which it may contain
but refuses to touch the precious metal
which, being soluble in melted lead, en-
| tiers at once into the glowing bath of that
substance to be seen lying in the center
of the cup. AT the end of this operation
most of the lead, together with nearly all
the baser constituents of the ore, will
constitute liquid Stag while the rest-Of
the lead, with every particle of the
precious metal, will remain as a red-hot
button upon which the lighter Stag is
floating The contents of the cup are
then poured into another dish and al
lowed to cool. A few blows with ham
mer clear away the Stag and few more
shape the metallic button into proper
form for future treatment.
The process Just described is called
specification. 1t leaves the silver of the
ore in the form of an alloy with lead
from which it is next separated by proc
ess called cupellation.
| Very hot oxygen has a strong attrac
| ton for lead but almost none for silver
| This is the very simple principle upor
which the process of cupellation is based
The elegance of the process itself rivals
the simplicity of its principle.
| Ali'IIe porous cup maze of bone ash Il
placed in II furnace and heated to red
ness. The little metallic button being
then introduced quickly melts, while
, current of air passing over its dull rec
surface furnishes oxygen for the chemi
cal action which at once begins. The
oxygen combines with the lead; multi
tudes OF little scales of litharge form
upon the surface of the glowing metal
They cart from the center outward anC
fall upon the cupel-as the little cup il
called--at its circumference, where the,
disappear altogether, being quickly alb
sorbed by the porous bone ash. In thi
way the lead is gradually carried int,
the substance of the cupel, while ever,
particle of the precious metal is left be
hind. AT length the little button sud
denly displays surface over whicl
dance all the beautiful colors of the rain
bow. These tints continue their fasci
mating movements uptil-the suprem
moment having arrived when the las
traces of baser materials have bee
driven into the cupel-the little butto
; of precious metal, with dazzling bright
ness remains in the bottom of the cup
} unmoved by the furnace heat. 1t is the
taken from the fire and carefully cooled
after which it only remains for the al
sayer to consult his balance to learn tn
value of the ore.-Le Roy G. Corley. i
Hearth and Home.