The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1869-12-24

This second acid is then also poured on, ana
another equal charge OF acid OF the strength Is
introduced in which the gold is kept for ten minutes
longer
It is then presumed that the whole of the silver
has been removed, and the gold is taken out washed
In pure water, and exposed I'm a crucible to q red
heat, for the purpose OF dryDg, strengthening and
annealingi IT.
Lastly, the cornet of fine gold thus formed is placed
in the assay balance, and the number OF thousandths
which it weighs expresses the 1neness OF the gold
assayed, In thousandths.
- The silver Assay.
The silver is melted in black lead crucible, with
the addition OF fine charcoal within the pot to pre-
vent oxidation and to allow OF dipping out After
stirring small portion OF the nuid metal is poured
quickly into water, producing granulation, from
which the portion for assay is taken. As this diners
from the mode pursued with gold, 1t must be speci-
ally noted that in the case OF silver aoyed with
copper there is separation to greater or less de-
gree, between the two metals In the act OF gradual
solidincation. Thus an ingot cooled in mould, or
any single coin cut out OF such ngot though really
900 thousandths fine on the average will show such
variations according to the place OF cutting, as
might even exceed the limits allowed by law. This
fact has been established by many experiments, both
in this Mint and the Mint OF Paris since the enact
ment OF Mint law and it possesses the stubborn
ness Of a law of chemistry. But the sudden chill
produced by throwing the liquid metal into water
yields granulation OF entirely homogeneous mix
ture, and 1t can be proved that the same hneness
results whether by assaying single granule, or
part OF one, or number together.
From this sample the weight OF 1115 thousandths
is taken; which is dissolved in glass bottle, with
nitric acid.
Into this solution the large pipettefu of standard
solution OF salt is introduced and it produces mme-
dately white precptate, which is chloride OF sill
ver and which contains, of the metallic silver, 1000
parts.
To make this chloride subside to the bottom OF the
vessel and leave the liquid clear IL IL necessary that
1t be violently shaken in the bottle and this is
accordingly done, by a mechanical arrangement, for
the necessary time.
Unless the pieces have chanced to be below the
allowable limit Of standard, the liquid will still con-
tain silver In solution, and accordingly portion OF
the decimal solution is introduced, from the small
pipette, capable OF precipitating q thousandth OF
silver, and white cloud OF chloride will show itself
More doses added, If the indications require it.
The liquid is again shaken, and cleared ard the
process is thus repeated, until the addition OF the
salt water shows only faint trace OF the chloride
below the upper surface OF the liquid.
Let US suppose, for the sake OF an example, that
three measures OF the decimal solution have been
used with effect. This will show that the 1115 parts
OF the piece contained 1908 OF pure silver and thus
the proportion OF pure silver in the whole aloyed
metal is ascertained.
After passing from the assay rooms and down the
stairs, we to the southeast corner OF the
building. Here is the general business office of the
Chief ConeT. In this room the gold and silver coins
are weighed and counted before being transferred
to the Treasurer. This department is provided with
| three large vaults, all fire and burglar proof.
The Cellar.
Advancing toward the coming room, we reach a
stairway leading to the cellar. Passing down, we
find numerous vaults, used for different purposes,
ranging along the hall fronting on Chestnut street
Now we pass on into the main cellar.
In the centre is large space, the same size as the
yard above. In this space are six large boilers,
which generate the steam for the different engines,
and to heat portions OF the building
On the right is the blacksmith, carpenter, and
paint shops. In the OF this is the meda.strik-
ing department. The process of striking a medal
differs from that of coin. They are struck with a
screw-press, worked by hand
The ''sweeps.o
On the west side of the cellar s the Sweep Grind
ing Room" Into this room all the dirt and sweepngs
OF the Mint are conveyed and ground up into fine
powder, and after the best has been selected it is
taken to the melting room, and all the metal eX-
tracted. The residue is sold
The Wells.
In this vicinity also the wells, wherein all the
water that is used in washing out the different
rooms, as well as that which comes from the differ
ent portions OF the building in time OF ran is re-
ceived and filtered. They are cleaned out every few
years, and the dirt disposed of in the Of the
'sweepings."
or late years the sweepings, ETC., have been OF
comparatively little value.
General Remarks.
Owing to the immense amount of precious metal
which is constantly in of transition from
form to another, and the and watchfulness ne
cessary to correct transaction OF business visitors
are not permitted to visit Of the departments.
These are OF little interest to the unscien1c, and
are described under their proper heads
Everything is weighed 80 nicely and so often that
the purlonng Of the slightest particle would be de-
tected within few moments after the act had been
| perpetrated.
The building is constructed almost entirely OF
stone and iron, and is therefore lre-proof.
Deposits Of less than hundred dollars in value
| are not received by the Mint.