The Manitowoc pilot. [volume] (Manitowoc, Wis.) 1859-1932, 1861-11-22
The Assay of Gold.

for November, Waldo Abbott takes US to
the New York Assay Office, gets US to
deposit little bullion. shows US how Un
Gle Sans men run it into bars, and then
gives US a description of the way in which
DR.. Torrey, the head Assayer, finds out
HOW MUCH We ARE WORTH. 4
Two small bits, called assay slips" are
cut from different parts Of the bar of each
deposit These are taken to the labora
tory of the Assayer. where they are ham.
mered, rolled into slips so thin that they
can be easily Gu, by scissors. These slips
marked SO as TO show TO what deposit they
belong, are given to an. assayer,- who has
before him. enclosed in glass case,
pair Of scales, with weights so delicate
that they will indicate the half millonth
part Of an ounce the smallest weight re
Sembling bit of horse hair the eighth of
an inch long. The operator cuts from the
slip piece weighing exactly half a
gramme Qhe gramme being French
weight, equivalent to about the thirlieth
part Of an ounce J to this he adds
granme Of pure silver, and eneloses them
in wrapper Of lead foil, weighing about
ten times as much as both gold and silver.
This is rolled into little ball and taken
to an adjoining room, where it uDdergoes
two operations, one Of which removes the
base metals, and the other separates the
silver from the gold.
The first of hose operations is called
"cupella,ion," and depends upon the prin
ciple that base metals, when melted and
raised 10 high temperature, combine
with the oxygen of the air and become OK:
ydized, while gold and silver ars not af-
fec;ed. This operation is performed in
'Muffle Furnace" which contains an oven
large enough to hold about dozen small
crucibles, called cupels. These are made
Of cacined bone dust, aad are about the
size Of large pill box, with shallow de
preston to hold the metal. The cupel
being heated red hot, the little ball is
dropped into ore of them. 1t melts i'm
medateiy, forming bright globule, which
boils and spins around. The surface rap.
Idly oxyoizes, and the oxyd runs down the
sides Of tue globule ard sinks into the
pores Of the cupel. Lead forms very
liquid oxyd which washes away, as it were
The ox,ds Of the other metals: and is
added for this purpose. In about ten
minutes The scum disappears and lie little
gIobuIe suddenly brighteus up; the cupe
! i> removed from the furnace, and the meta!
/ forming little button about the size Of a
buck SLOT, is taken out. THIS contains
only gold and silver; all base metals hav
ing disappeared.
This button is hammered and rolled
out thin, and then formed into a coil about
as large rs pencil; this is called a cor
net, and is to be subjected to the second
process, for separating the silver from the
gold This is based on the fact that nj
,rc acid will dissolve silver, while it will
Tot act upon gold. Bat the proportion OF
silver in ordinary bullion is so small that
each particle is surrounded and protected
by the gold. The silver was added by the
Assayer in order TO dffuse the gold, and
enable the nitric acid to come at the sill
yer.
The corne. is put into "mattrass," a
vial with a broad base aud long neck
Into this is poured about sn ounce of dilu-
led nitric acid, which is boiled by placin =
the vial in bed Of hot sand. Bright red
fumes soon arise, showing that the action
Of the acid upon the silver has begun. In
about ten minutes the acid is poured off,
and quantity of less dilution is poured
in 10 dissolve out tie last traces Of the sil-
yer. The silver and nitric acid uniting
have formed lhs nitrate of silver, and the
remainder of tie cornet is pure gold. II
is a fragile roll looking very like the brown
finder left in burning writing paper. This
is taken out, washed in distilled water,
and melted in crucible, when it at once
resumes It's metallic appearance. 1t is
carefully weighed in the operators delicate
scales, the result showing The fneness o,
the bullion !; or how large portion Of il
WAS gold or how large alloy. The value
of an ounce of any fneness being already
known, the whole value of the gold in oul
deposit is readily ascer,alnei.
The volcano Of ChiIian, in The An1e.
has recently broken out in active eruption
The craier is abou. II 900 feet above ths