Vermont watchman and State journal. [volume] (Montpelier, Vt.) 1836-1883, 1857-08-21

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MELTING. AssAYING, REFINING AND COINAGE
or Bu1IroN.
/ A dcposito of gold bullion having been reg
ularly received by the Treasurer Of the Mint
/ is removed TO the deposit melting room in
locked pans, "a duplicate key of which is in
the possession Of the foreman of the depart
ment) where it undergoes.the necessary melt
ing preparatory 20 the assay process The
object Of melting is two-fold FIRST. TO sepa-
rate from the metal all the earthly matter and
second, 20 obtain homogeneous mass from
any part Of which a small chip may be cut
for an assay piece. To accomplish this end
the bullion is mixed with borax. which az a
high heat forms a chemical combination with
the earthly impurities. and this. in the form OF
vitreous compound, is readily separated. be-
ing lighter than the fused metal. Tholatter
is now cast into convenient moulds and care
fully numbered, and reserved until the report
of the Assayer enables the Treasurer TO de-
torminc its exact value.
The gold assay slips, properly marked and
numbered TO prevent any possibility Of intor-
change, pass 60 the Assaye-'s department. and
are each separately assayed. This process is
one Of the most carefully conducted Of chem
ical analysis. The first part of it is the
weighing Of the assay slips on beam of great
susceptibility, the weights used being dem
igramma and its decimal divisions to one ten
thousandth part of a unit. After the slip is
weighed, it is enclosed with the proper pro-
portion of pure silver. in a small piece of lead
pressed in a bullet form. and is then ready
for the laboratory process This consists first.
in the cupellation or separation of the oxyd-
able metals, which is conducted i'm a small
furnace brought to proper heat and in small
cups. called cupels, prepared from calcincd
bones, in which tho loaden ball with its con-
tents is placed, and by which the base metals
in state Of oxydation and fuidty. are alb
sorbed. Lead possesses the property of OK
idizing and vitrifying under the action of heat
aud az the same time promoting the oxidation
Of all other base metals
When the cupclotion is finished, the disc
or hutton, being pure gold and silver, ia de-
tachod from the cupcl and by series of man
ipulations, is rolled into a thin slip in order
to give surface for the action of nitric acid, TO
which il is next subjected to separate the gold
from the silver Tho slip thus rolled out is
placed in a glass mattrass or bottle, contain
ing the necessary quantity of acid, to which
heat is applied by gass apparatus. The ac-
id dissolves all the silver, leaving the gold
pure IN the form Of a spongy brittle mass,
which is returned to the balance. where the
loss is oscertained, and the precise proportion
OF pure gold accurately determined. This is
reported to che Treasurer. and is the basis for
calculating the value Of the deposit represen-
ted by the assay slip.
The assay Of silver may be conducted by
tine cupellation process, but is more delicately
determined by the humid assay, which is based
on the well known property Of a solution of
common salt precipitating the silver from its
solution in the form Of the chloride, the ulti-
mate PARTICLES being thrown down by pre-
pared decimal solution, and the ineness de-
tormincd bv q table corresponding TO the
nutnorr OF chart,rs used In rreeffsItatfn,s ri,o
chloride.
The bullion having been thus assayed, is
then delivered to the meltor and reiner, to be
refined and made of the legal standard for
coinage
Native gold being moro or less alloyed with
silver and the latter metal being almost un-
necessary in gold coin, it is customary to free
the gold from the greater part of it. This
operation is termed refining. California gold
contains ON an average per cent silver
the covering power, however, of gold is such
that nitric acid. ready solvent of silver, will
only remove the smallest fraction of it. One
pound of gold is therefore melted up with
two pounds of pure silver, which being thor
oughly mixed, is ladled out into cold water,
whereby the mixed metal is divided into
small pieces, termed granulations. Each par
ticlo of gold is thus surrounded by two par
ticles of silver, so that when heated in por-
celain jars with nitric acid, all the silver, OK
cept about one per ceut., is dissolved out Of
the gold. The nitric acid, holding the silver
in solution, is then drawn off from the pots
by large gold syphon. and passed into a
large vat, partly filled with a strong solution
salt, when the silver falls down as white
powder, called chloride Of silver, insoluble
in water It is next run on filters, which hold
the chloride, and let the liquid pass through.
The chloride, after being washed for many
hours by hot water until perfectly clean, is
thrown into leaden lined watts together with
granulated metallic zinc, where a violent ac-
tion takes place, the zinc forcibly seizng the
chlorine, and making solution Of chloride of
zinc, while metallic silver is left in the form Of
a gray powder, which after being washed and
filtered, is pressed into large cakes by hy-
draulc press dried by fire, and is again used
to refine more gold.
The pure gold transferred from the bottom
Of the porcelain pots to a filter, is orough-
ly washed from every trace of nitrate of sill
yer, and from its state of fine division, has no
metallic appearance, but closely resembles
mahogany sawdust. II is then pressed. dried,
melted with a sufficient amount Of copper to
bring it to the legal standard, and cast into
ingots or bars, suitable for the manufacture
of coin
The ingots are then passed to the coming