Clinch Valley news. [volume] (Jeffersonville, Va.) 18??-2019, 1893-01-20
IN THE CRUCIBLES.
SEPARATING PURE GOLD AND
SILVER FROM DROSS.
The Interesting Work Done by the
government AssaYcrs-A Deli.
cate Operation, Where Mis-
takes Arc Expensive.


the mines as bullion, besides foreign
coin, old silver plate, jewelry aud masses
of precious metals III all forms and
quantities; this is weighed out in bulk
just as il comes, and is credited to the
one shipping it to the Office at the correct
weight OF the unretncd gold OF silver.
After the value has been determined by
assay the gold is paid for with gold bars
or coin, Mt the option Of the owner, aud
the silver with silver bars only, no value
being fixed upon the latter, owing to the
constant changes in the market price of
silver. No deposits are received of less
than Sl00 in value; and if quantity
comes in of less amount the balance
must be made up in current gold or silver
coin or bullion. Each deposit is first
melted by itself, and, when its value has
been asccitained, goes with the rest
through the melting and refining pro-
cess. There is almost always consider.
able silver and baser metals in the de-
posts classcd as gold; but deposits arc
c.assed as gold or silver according rs the
incness o! either metal predominatcs, no
assays being made except for gold and
silver.
The great value of the goods requires
very correct weights. The great balance
in the receiving office has Il capacity of
700 ounces, and at the same time is
adjusted SO dclicacly that one one.
hundredth OF an ounce will be indicated
by the swaying of the ponderous bal.
aucc, which rests on Il knife. edge above.
From this loom all deposits are taken to
the melting room across the central hall
OF the building. Around this room are
furnaces arranged for the melting Of the
metal; the gold is here melted together
in pots or cruciblcs of black lead set into
furnaces heated by gas Jets.
The silver is melted in larger furnaces
heated with coal. After the metal de-
post has been thoroughly melted and
become orc homogeneous mass by stir.
ring and luxing it is taken out and cast
In bricks of varying sizes, according to
the amount in each deposit When
cooled, il it is all in one brick, a SAM
pic is cut by heavy machine from each
81 the diagonally opposite corners. II
there are several bricks in the deposit
a sample is taken from the first and last
bricks cast. Thus these samples are as
far removed from each other as possible
and consequently are as unlike as any
that could be obtained from the mass.
These bricks are stamped with the
proper stamp and initials and placed in
the vaults. The samples, with tickets
bearing corresponding numbers, arc
taken to two different men for assayipr.
and the exact value of the metal found
In percentage Of gold or silver in 1000
parts. If the results differ by the one
thousandth part the melting is repeated
as it indicates an inequality in the de.
post or imperfect work somewhere in
the operation.
These samples are rolled out, and a
tray containing several compartments
with as many specimens, are taken tc
to one assayer, and another tray of du.
plicates is taken to another assayer.
The work which these men have to do is
very interesting.
They sit at long table on which arc
delicate, glass-inclosed balances. The
assayer takes fragment of the thin
sample strip of metal, and estimates
with prac:iscd hand aud eye the pcr.
centage of gold and alloy; then CAREFUL,
weighing out required proportion o.
this metal, he rolls up small sheet O.
lead foil into cornucopia, and placing
inside the metal weighed out, adds somt
minute disks of pure silver, already pre-
pared, of different fixed weights, so pro
Forthcoming the pure silver and the esti
mated silver alloy in the metal being as
sayed that, combined, it shall be nearl,
equal to twice the weight of gold there
in.
After this mixture of one part gold
and two parts silver, besides base meta
alloys, has been wrapped in the lead fol
a trayful of these prepared specimens i.
taken to tue cupcl furnace, each bearing
its own assay number.
The cupels arc small, porous, burnt
bone cups, or crucibles, manufactured IL
the building by pressing the pure, white
moist bone dust into mold and thcr
allowing the cups to dry for two months
Each dainty package of metal is placed
in cupel, and 4 small, gas furnace
heated to an intense heat, receives
large number of these, arranged in sys
tematic order, covering the bottom o.
the oven. Being melted, the lead sinks
into the porous substance of the cup
carrying with it the base metals ant
leaving mass of pure silver and gold
On removing the cupels this meta
quickly solidifes into bright, rount
button at the bottom.
1t is then removed, tapped light,
with a hammer to free it from any out
side matter, and after being weiehe,
again, is rolled out into a thin strip
coiled up on astick, and basket-lik,
platinum case with many small recepta
Giles is filled with these small specimens
and boiled for ten minutes in nitric acid
this combines chemically with the silver
leaving the gold in gpongy mass, yer,
pure, but dark and unacceptable i,
color. This pure gold is then weighed
by the assayer, and the ratio between
this and the weight of samples used il
the test shows the proportion OF golt
and silver in the metal deposited. Thi
process'is for ascertaininp the nronort,o,