The Providence news. (Providence [R.I.]) 1891-1906, 1899-01-04
Interesting Method Employed For The Sep
aration Of Gold From Silver.
SILVER DISSOLVED BY NITRIC ACID.
Gold Remains Untouched Parting Acid Used For
Driving Out Any Remaining Traces Of The
White Msial-Ths Weighing Process.

many climates--Siboria or Africa Klon-
dixie or Australia, California or India.
Situate your mine where you will. So long
as IL be gold mine the procedure Of as
sayingis is the same all the wide world over
Select mass of orc weighing, perhaps, 80
pounds and smash IL up DO not expect
TO see any gold I'm II because the precious
metal Is probably so thinly and uniformly
scattered through the quartz that il Is i'm :
possible to spot grain together. Continue
grinding the orc till IL Is i'm the form of
powder. This powder is heaped into cone,
which Is divided into four parts of which
the sampler takes two whose angles are
opposite to one another Mix these two
parts thoroughly and again divide into
four; take two portions again, and so on
till n sampie Of convenient bulk is obtain
ed BY this logical method the sample
yielded is, on any ordinary calculation of
probability, certain to represent accurately
tho originGl mass taken.
A certain quantity Of this sample Is now
weighed out, two equal amounts being
taken as checks upon each other. The
weighing may bc done in denominational
values Of either grams or assay tons. Tho
assay IN Is most convenient inven-
tion and is very simply explained. The
ordinary ton contains 32, 666.6 ounces; IL,
then, we make unit tan assay toni weigh
ing 32.6G07 grams, each .00l of gram
will equal ono ounce per ton. Thus, no
calculation is needed at oil to estimate the
gold richness Of an ore per ton.
Say we weigh out, then, two separate
portions of tho ore Of one assay ton "a. Il. }
each, With each mix thoroughly bicarbon-
ate Of soda, llthargc, borax, glass and
flour In varying proportions; when thor
oughly uniform in color empty the mix
turesAin fire clay crucibles and strew on the
top alhia layer of salt Put on the lids of
the two crucibles and surround them with
living coal, coke or burning vaporized
benzoline In n acrucible furnace The cruel
bles are heated till tho masses of ore and
huyes are in state Of tranquil fusion
that is, not bubbling or boiling. Tho white
hot fluid is then poured into iron molds
and allowed To cool
Determination, after cooling, the fused
4. masses will be found to consist of: I)
A layer If white substance, which is salt.
: (2) A Stag This is usually dark In color,
often resembling malaohite, and Is formed
by the fusion OF the borax and soda with
the worthless or earthly matter (gangue)
in the ore. CD A lead button, produced
mixed I'm the charge.
This lead button contains all the silver
and gold in the ore. The heat OF the fur
mace drives off from the lead oxide It's oxy
gen. SO that pure lead is left; this, in vir-
tue of it's weight, percolates downward
through tho Stag during the heating I'm
tho furnace, collecting all the gold and sill
yer present, and eventually forms but
nv nf nttr
has been added originally, about 10 to 90
grams The -four has the effect OF vary
ing the size Of lead button produced and
Is said to possess a reducing action.
The next step I'm the process Is TO get rid
of the lead without also losing the gold
and silver. This is done by an operation
known as cupollatlon The cupel is "a small
round, bone ash cup, which Is placed in n
sort of fire clay tunnel with one end closed
up, known as mufile Tho muflle is heat
ed from the outside, either by burying it
with Goals or by playing burning gas on
every part Of It, When the cupel has at
tained the heat Of tho interior OF the muf
fio, the lead button is placed In it and the
door Of the mufflc shut, so as 10 procure
tho greatest amount Of heat possible.
Whom tho losl is seen to be melted and
fumirfh, tho uufflo door is opened To admit
the air, " hich Ia sucked in by the intense
heht.
The oxygen contained in the air oxy-
dies tho lead into lead oxide, and tho bone
ash cupel absorbs lead oxide like sponge.
but refuses to absorb the gold and silver,
so that ut length there Is left in the cupel
only n button OF tho two precious metals.
1t Is to 10 supposed that two ore samples
havo been treated similarly both In the
crucibles ard cupcls, but for the sake OF
convenience II is better TO explain the
treatment CT one only The bead OF gold
and silver obtained weighs, let us say,
,00l6 Of n gram. This IL noted down.
The bead after weighing Is flattened out
In ilatthg mill, so as to expose as large
q surface rs possible 10 tho nitric acid
which Is then added TO IL. On heating the
silver is dissolved, but, of course the gold
is untouched by the action of any single
acid The remaining pure gold Is treated
with stronger acid, called parting acid.
10 drive off any suspected trace of silver.
and then washed with winter.
II tho parting" Of the gold from the
silver has been successful, tho gold Is left
% a thin, small sheet. From this all mois
ture Is driven OF by heat On weighing,
the gold mny be as heavy rs .0007 of n
gram. Then as II hns previously been
noted that tho total gold and silver bead
had weighed .00l6 OF a gram, the
weight of silver present must have been
.0009 of gram-.hat Is 20 say, In one
assay ton OF e.Ge67 grams there are
.O0o7 gram of gold and .0O09 gram II
silver It has been stated at the com
moncement of this article that in an assay
ton each .0Ol OF n gram represents In
real tone ono ounce. Therefore we have
seven .tcnths of en- ounce Of gold-that is
IA pcnnywsights GO dwt. equal OH
and pine-ter.hs ~ an ounce Of silver-that
IL, Is pennyweights--to the ton. Quod
s-at faciendum.
Many minor processes, such as roasting
scorificstion and inquariation, entcr Into
tho. work done in an assay but u has
been desirable 10 mako the procoss Ne clear
And free froni catppliratiou A. rOssih bic