The Birmingham age-herald., 1913-02-02

detail here. Suffice it to say that the
process is based upon the fact that from
an alloy of gold and silver in which
silver predominates in the ratio of about
three to one it is possible to dissolve
the silver by nitric acid. leaving the pure
gold behind. To a weighed portion of
the bullion is added an amount of sill
yer which will bring the proportion up
TO three to one, IL it is rich in gold,
or, If it is rich in silver, sufficient gold
to bring 1t up TO this proportion. This
sample weighs one thousand gold-weight,
or one-half gramme; very nearly seven
and seven-tenths grains. 1t is rolled up
within piece of pure lead foil weighing
about two grammes An exact duplicate
is made. as are also two similar samples
from the opposite side of the bar Two
other samples are prepared of a weighed
amount of absolutely pure, or proof
gold, and silver called the proof samples.
fourth set OF samples is made from
| one-thousand gold weight of the bullion,
which is likewise increased in lead.
These samples are then placed in GU
pefs, in furnace which has been heated
to bright red. A cupel is small dish,
little more than an inch in diameter,
made of boneash, and boneash is pull
verified calcned animal bones. GU
| pei has the property of absorbing oxides
| of lead and other base metals when these
What occurs in the furnace is practical
ly this: the lead and other metals melt,
and as the air passes over this molten
mass the lead and base metals oxfdize
! rather rapidly. A portion of these oxides
are absorbed by the cupel and other por-
| tions pass off in the form of vapor. The
| final result of the process is a slobnle of
| gold and silver The first three sets of
samples dhe top, bottom and proofs
which contain the proper proportion of
gold and silver for parting as the nitric
acid treatment is known. are rolled out
| thin and placed in small cups of plat-
mum. These cups fit neatly into a basket
iof the same material and the whole IS
| then suspended in a platinum cup con-
| tanning boiling nitric acid which dis
solves the silver. leaving pure gold In the
cup. This is very carefully dried ut
| slow heat, placed In the furnace TO be
momentarily heated to a cherry red. re-
moving the last possible trace OF mols-
ture and weighed on the scales upon
| which the samples were originally pre-
| pared This weight shows the amount
i OF gold in the bullion, after making the
necessary corrections indicated by the
proof samples gain or loss during tho
| process. The fourth set of samples,
| composed of gold and silver the base
metal having been driven off during the
cupellation, are weighed without any
further preliminaries. Their loss in
weight indicates the amount of base
metal which was in the bullion Having
determined gold and base metal the
difference is reckoned as silver.
The Scales
The scales used by the assayer in his
work are the most delicate of the appli-
ances used in the assay office, although
the large balances upon which the de-
posits are weighed are themselves of eX-
treme accuracy. But the assayer's scales
take the palm. They are sensitive to one
two-hundreth millgramme. Fearing that
1t will not be realized what this means
it will be explained further. These
scales will weigh a lead pencil mark
Sometime when you are in the assay
office deposting the hypothetical gold
from the hypothetical mine ask the as
sayer to weigh piece of paper an inch
square. After he has done this make a
mark across the paper with a soft lead
pencil and you will be surprised to sec
that 1t is possible to weigh this mark
1t will weigh anywhere from one to
three one-hundredths of milligramme,
depending upon the softness of the
pencil and the breadth of the mark, of
course
The assayer having completed his
work, reports the fineness of the bar
and the clerical force gets busy on the
calculation Of its value. knowing the
weight OF the bar and the proportions OF
gold and silver it is mere matter of
figures to arrive at its value This
done you are given either a check or
United States coin upon surrendering the
receipt which was given you when YOU
deposited your bullion.