Rock Island daily Argus. (Rock Island, Ill.) 1886-1893, 1892-10-05
ASSAYING FINE GOLD.
HOW IMPURITIES ARE DETECTED
IN A SOLID GOLD BRICK.
FOLLOWING Insot Gold Through Several
esages - Extracting Silver from the
Precious notwithstanding Steps in a
Chemist's Laboratory.

Chemists Laboratory.
About O'Clock in the morning two men
entered the Mitchell building, and getting
into the elevator mounted to the sixth
floor and went straight to the rooms of the
United States assay office One of them
carried in his hand a bundle the size of
thin brick, wrapped in paper. He laid it
down on the counter in the office and slow
ly unwrapped the bundle. 1t was a gold
brick The clerk took the bullion. and
stepping across the floor placed it in one of
the pans of large pair of scales. Then he
closed the Office windows and placed some
weights in the other. When it balanced
nicely he went to his desk, took out a
blank form and wrote to the effect that
400 ounces of gold bullion had been re-
ceived from the St. Louis Smelling and
Refining works at the United States as
say Office, to be assayed. This was signed
by E. c. Jewett, the assayer in charge, and
the men went away. This is the first step
the government takes toward obtaining
precious metal for coming purposes.
1t is extremely interesting to follow this
process of assaying through all the steps
until the value of the gold is determined
and the governments check given for it.
While Clerk Rex was filling out the re-
celpt Mr.. Jewett explained the marvellous
dehcacy OF the scales Their weighing ca
pacity is 5000 ounces, and it is possible to
indicate by them difference in weight of
one gram. To illustrate so that this may
be easily grasped, two heavy men could be
placed In one of the pans, and by removing
pin from the coat of one of them the bal
ance would be changed. Still it would be
difficult to obtain the exact weight of the
men, owing to the constant change in the
mems bodies by perspiration and other
causes
After the billions weight was deter
mined on these scales it was taken to the
furnace room and placed in blacklead
cruclble. This was set on friedrich rest
ing on CRATE and a fire built around it.
/ The fuel used is a mixture of anthracite
coal and charcoal After an hours melt
ing, during which time it was frequently
stirred with a plumbago poker, to which
goId does not cling, sample of the metal
was dipped out with an ordinary clay pipe
and poured into small mold. The assay
IS made from this, as it takes so much
longer for the larger quantity to cool. A
piece of the sample was cut off, pounded
and then rolled through a roller of tool
steel, looking something like a clothes
wrinEer, to make it thin. When this was
| done, Herman, the German who aids the
assayer in his work, handed the thin
| golden strip to him and then went back to
the furnace room TO pour out the molten
thousands into the big mold.
Mr.. Jewett cut the strip into small
pieces, and then, forming little lead cornu-
| copias OF uniform weight, dropped into
two of them $50 milliCrams5one sixteenth
| OF an ounce of accurately weighed gold TO
| be assayed. Into two others he put the
same quantity of absolutely pure gold
Enough silver was then added 10 make the
| proportion of silver to gold two TO one as
| this proportion Is necessary in order that
the gold should separate from the silver
when boiled III nitric acid
There is in all gold certain amount of
silver, and it is owing to its presence and
| certain other foreign substances that the
color OF gold varies. The idea that gold
| found in California or Australia is of such
| a color because found there is q mistaken
| one.
After the silver had been added the
leaden cornucopias were squeezed up and
each one placed in what is called a cupel
| A cupcl is a Little cup made of sheep bones
| burned to ashes, ground fine, moistened
and nodded into mold an inch long, an
inch in diameter, with a cup shaped de-
preston at one end. The cupels were
placed in a small furnace with a tempera-
ture of about 100 dogs. centigrade, and
when heated to n white heat the little
metal chunks were laid by the aid of tongs
one in each cupel. They melted, sputtcred
and dubbed, and then began to grow
| smaller. In about ten minutes they were
taken out and all the lead and foreign sub
| stances had been absorbed by the cupel
| leaving only the noble metals in little
| round balls. When these were boiled in
nitric acid the silver passed into nitrate of
| silver and the gold was left in its pure
state. By this was found the ratio of pure
| gold in the bullion.
The weighings of pure gold are used as a
check to any particular conditions of heat
etc. The assayer knows the constitution
weight and specific gravity of the pure
gold used When it is weighed after the
heating process, if it has changed its
weight, it is fair to suppose that it is ow-
ing to the conditions of heat or strength of
| acid, and that the same influences have
been at work on the assay gold. By al
lowing for this in the assay gold true re-
suit is reached.
The next step was to find the weight of
the gold and silver together The lead
cornucopias were again filed with certain
weights of the pure and assay gold, but no
silver added. When melted in the cupels
the baser metals disappeared as before,
and the gold and silver were left to-