Evening star. [volume] (Washington, D.C.) 1854-1972, 1894-10-20
A PURE GOLD BAR.
Il VIII Serve as q Standard for Miats
and Assay Omces.

~ w ht SCfNS ~ - ttoA4aEa k0f
and Assay Onices.
Uncle Sam Is preparing a standard OF
pure gold. 1t will take the form OF a bar
Weighing 30 ounces. This bar will be cut
into several pieces. one Of which will be
given to each of the United States mints
and assay Offices. A slice will also be sent
to England for comparison with the British
standard of pure gold.
1t seems that no absolutely pure gold has
ever been produced In this country-at all
events none OF which there can be certain
ty. The standards now possessed by the
various minis differ somewhat; not one OF
them is surely free from impurity. For
the purpose of exactness in assay work
IT Is desired to have a standard that is
as Caesars wife should be-beyond sus-
picion.
The bar that Is to Be Is now a liquid
The 80 ounces Of gold are In a chemical
solution at the mint in Philadelphia. The
yellow metal thus dissolved was extra fine
to begin with, having only one-tenth of
per cent of impurity. The impurity was
chiefly silver. This gold was rolled to very
thin sheets and put put into a tank Of
aqua regia and hydrochloric acid.
The solution of gold made in this way
was diluted with 70 gallons of distilled
water. In that condition 1t now remains.
a thin but precious liquor. Under the &C
ton OF the acid the silver falls down to
the bottom Of the tank In a white cloud.
| will be drawn OF carefully into TASKS.
without stirring, to leave the silver
| impurity behind. Sulphurous acid gas will
| then be passed through the solution, caus-
ing 1t to throw down the pure metallic
| gold.
But many processes have yet to be gone
through before the gold will be considered
chemically pure. 1t will be washed with
acid, dissolved ia aqua regia, evaporated
almost to dryness. diluted with water and
freclpiiatec in metallic form by oxalic acid.
All this VIII then be repeated Finally the
| gold will be collected, melted in a porcelain
orucible and made into a bar The piece of
the bar that is sent to each mint will be
| compared by chemical tests with the STAN
dard OF pure gold now used at that mint.
Obtaining the Coin Gold.
Uncle Sam maintains many chemical labo-
ratories. There are a dozen in Washing
ton. attached to the various departments
| The mints do much chemical work incl
dentaily to the assaying and refining of
| metals for coinage. The gold is refined by
melting IT with three times its weight Of
| silver and placing IL in kettles with sui
| phUric acid. The acid dissolves the silver
and other metals that are mixed with the
gold, but does not affect the gold itself
which is left at the bottom of the tank in
| the shape OF brown powder. The solution
| or silver, etc, being drawn Oft the pure
| gold Is washed with water and melted into
bars. The silver is recovered from the So
| iutioH ny iiiliIltTSluB IN the latter large in
| gots of copper, on which the silver is de-
posted by the acid. The metallic silver
| Is then washed OF Of the bars and melted
| into bricks.
silver are got from the raw bullion for
making the coins of the realm At the
treasury in Washington is q laboratory
where sample coins taken from each batch
turned out at the minis are tested for
weight and fneaess. They are rolled out
INTO thin strips. and then bits taken from
each piece are subjected to analysis Other
! metals which commonly are found as i'm
puritfes with gold are platinum, conner
lead and iron. In order that not a trace
q any Of these shall remain in the STAN
oard par no chemical precautions must be
neglected.
Analysing Rocks.
Some Of the most interesting chemical
work of the government is performed in
the laboratory of the geological survey
There rocks and minerals are analy:ed
One way to analyze a rock is to grind il
line, pass the powder through a sieve dis
solve weighed portions of II in acid, sepa-
rate the ingredients by different reagents,
dry them and weigh them. The object of
this work is to identify minerals and rocks;
also to explain the alterations which GER
tain rocks undergo in nature. For instance,
one mineral In the earth's crust Is slowly
transformed by percolating water into an
other mineral. The problem is to find out
Why. Not long ago the laboratory made
al eldDOrate investigation OF the geySer
waters of Yellowstone Park, which were
found to be very remarkable chemically,
some or them containing borax, others ar
senfc and yet others ammonia i'm large
quantities. None of them has any medic
inal value.
In charge of this laboratory is the ia
nous chemist, DR. Clarke His chief as
sistant is DR.. Hildebrand, who first dis
covered nitrogen in the primitive crust of
the globe. 1t was found in a mineral called
uranianite- Previously nitrogen was only
known as occurring in secondary products,
such as deposits of nitrate of soda The
question, where did nitrogen originally
come from? is still unanswered The air
Is mixture of oxygen and nitrogen. Do
they represent a residuum left over after
the solid sphere of the earth was made?
LII not, where do they come from? People
commonly think of the air as one gas a
chemical mixture of oxygen and nitrogen.
On the contrary 1t is two gases mechani-
cally mingled, the molecules of nitrogen
floating about among the molecules of
oxygen. A chemical mixture of the two
| l. e., oxide of nitrogen, can only be formed
IN very small quantities by means of the
electric spark.