Eureka daily sentinel. [volume] (Eureka, Nev.) 1871-1887, 1880-11-19
AssAYING.
A Correspondents MethOd-Though
the subject IL old, Our Readers
May Gather n New Idea.

h subject Ii old, Our Readers
May tsather n New Idea.
The subject Of assaying ores is almost
always new in every district. The ores be-
ing of a different order and carrying differ
ent properties, necessarily require achange
Of operation to ascertain the real value Of
the crock" under treatment. In an east
ern paper We often see the idess of this one
and that one, who happen to be located in
a particular locality, advanced as the only
and proper way to test.
For o general idea, pehaps the following
is as good as any. At any rate. below is
advanced a system which generally holds
good
The ore is pulverized sufficiently fine to
pass through a sixty sieve; which means
that there are sixty meshes in q linear
inch Of the wire screen constituting the
sieve. In this condition the ore is called
pulp. The quantity that we shall use in
ounce.) To this we will add 500 grains Of
powdered litharge (oxide of lead). $50
grains of b~icarbonate Of soda, 100 grains
of borax, 20 g~rainsof carbon usually pull
verified charcoal, and often instead OF char
coal 40 grains of fiour.) These ingredients
are thoroughly mixed; when, If the pres
ence of sulphur is suspected in the ore, q
small piece Of iron is added usually an
eight penny nail.)
The mixture is put into a crucible about
six inches in height and three inches inter-
! nal diameter, and that is placed in a fur
mace, burning charcoal or coke, and the
heat rapidly raised while hot.
After the contents are in fusion, the cru
chile is allowed 10 remain in the fire fifteen
minutes. when effervescence having ceased,
it is Withdrawn from the fire and placed in
a vertical position and allowed to remain
until quite cold. The crucible is then
broken, and il no complication due to
arsenic, anthony, copper or other base
metals have arisen for which there is q
remedy, the result Of this feature in the
assay will be found in the bottom Of the
crucible in the shape of a lead button, Gre
ated by the reconversion Of the litharge in
to metallic lead, and all the metals con-
tanned in the ore, being heavier than the
liquid mass OF matter in the crucible. will
sink to the bottom OF the vessel, and will
be found amalgsmated with the molten
lead. The fused matter remaining in
scoria or Stag and often exhibits the most
beautiful coloring Of an infinite variety
and exquisite delicacy Of shades, due to the
presence of different combinations Of min
eral matter in the ore, the soda and silica
making a glass which is stained by it.
The lead having gathered by amalgama-
ton the gold and silver, with whatever
base metals may have existed in the ore,
must now be separated from the noble
metals by another fiery process known as
-, va1latsn Tkn Lad Ix,ttop 10 ON p1anaI
in a cnpel. Cupel is a French word, mean
ing cup, which cup is made of bone ash.
ashes Of burnt bones. Placing the cupel
containing the lead button in an oven,
this oven is called a mufle) in the furnace
heated nearly white hot, cupellation pro-
ceeds slowly by the oxidation or burning
of all the base metals away from the noble.
Lazily arising from the molten surface Of
the lead in the cupel now are seen fumes of
a reddish brown color. This is a volatile
oxide. and its inhalation is poisonous. A
LIQUID oxidation of the base metals takes
place at the same time, and this liquid OK
ide or litharge. is absorbed by the sponge
like property Of the cnpel. Gradually
the button Of molten lead burns and
subsidies. growing smaller and small
err until nothing is left but a
bright bead-Iike globnle, glistening with
an entirely different light than pertained
to the larger mass, and standing upright
and firm upon a small segment Of its
spheroid shape. II its color is yellow. the
metal is unquesiionably gold. since gold is
the only yellow metal which remains after
qnpellation. A yellow button is a rare oc-
currence in the process of cnpellatiop, for
gold is almost ALWAYS fonnd alleged with
silver. in which event, unless the proper
tion Of silver is very small, the globule
will exhibit a silvery color.
1t now remains to decide the amount
per tor that has been yielded by the as
saved sample of ore. To do this a scale
for weighing the button obtained so deli
cate az to register with perfect accuracy
the weight of q hair of my head an inch
long ia used, and when such Q hair Is
weighed upon such an instrument no more
doubt as to the correctness OF its registry
would occur than wonld attach to the
record Of the stock-yard scales in st. Louis
when two carloads of hogs are weighed.
The weight OF a gold button having
been ascertained it then becomes a matter
Of simple multiplication to ascertain. If
half an ounce yields SO much god, how
much would a ton of the same ore yield,
the sample being an average of the ore.
II the button is an alloy Of gold and sill
yer, the button, as it first came from the
cupel. is first weighed; it is then boiled in
nitric acid. The acid having a strong af-
inity for silver, unites with it, forming
nitrate of silver, leaving the gold chemical
lypure. This is then placed In an annealing
cup, which is put into the muller and
heated to a cherry red, when the purplish
color il had when it came from the nitric
acid, gives place to the bright yellow color
Of annealed gold. This is then weighed
and its weight subtracted from that Of
the original alloyed button rs it came from
the cupel. The difference will represent
the amount Of silver yielded by the sample
assayed.