Idaho County free press. [volume] (Grangeville, Idaho Territory) 1886-current, 1890-07-04
Roasting for suiphuration..

1or the complete reduction Of iron TX
ides 10 the degree requisite for the di-
rect formation of this slag-silicaie is, for
sefqui-oxide.=32 Per cent, and for mag
netic oxide, to 2.50 per cent of the
weight OF the respective oxides.
In addition to the amount of coal
which is needed for the above purpose
and which, in practice, will be a varIa-
Bile factor, and one which is dependent,
as already indicated, upon the quantity
anu character OF the fluxing oxides and
upon the uncertain gains and losses in
ihe conduct of the process--in addition
to This amount. we Will require a further
quantity of coal sufficient to reduce
metal enough to combine with the bal
ance Which is left from the sulphur lib
Grated from the raw ore; deducting, for
such balance, from the whole quantity
of sulphur so liberated, the inevitable
irdste and the amount required for sui.
pbufizng the Originally metallic particles,
as contained before treatment in the ore
The amount of pure carbon* which is
theoretically required for the reduction
of metals from the lower oxides, in
quantity sufficient to appropriate all the
sulphur liberated from raw ryrites by
fusion, is=1-20, or 5 per cent OF the net
weight of the true pyrite contained in
the ore used. For black oxide of cop
per, copper slicates and carbonates, and
lead snphate, twice the above amount;
and for sulphate of COPPER and sulphate
ofsilver four times this amount of car
bon will he equired-These sulphates,
under the conditions Of practice, being
reduced to metal and sulphur dioxide.
Allowance, according to the above
should be made for the proportions of
sulphur which are appropriated, sew
eraly, by the different portions Of metal
from such several quantities of these
compounds as may he estimated to be
present in the ores. Lime and other
alkaline matter will appropriate sui
phur, but will give most of 1t up again
in order TO combine with silica when
enough of the latter is present. The
Flag which is TO be made should be
slightly "aeid" to prevent loss Of both
sulphur and metal.
Sulphur which is in combination with
arsenic OF antimony may be estimated,
in part, as free sulphur; for these ele-
ments will be set free, and, in great
measure, may be voatilized without
resulpluration. II may be found, how
ever. that the prevention of the forna-
tion of considerable proportion Of
''speiss" is matter of difficulty. Mag
netic pyrtes," or pyIhotite. also con-
tains some surplus sulphur, if the form
ula, Fe7, O8, given by Remsen be correct.
1t may be taken as cqnal in this respect,
to 10 per cent. or nearly ! of its own
weight Of true pyrites Copper pyiites,"
or chalcopy rite, Gu Fe 50, parts with
of its sulphur on fusion, and is equal to
of its weight of true pyrtes.
The sulphurizing roast should be con
Quoted with fame as nearly neutral to
sulphur az possible. There should be
no excess of air in the process. A por
ton OF the iron oxide. or ore containing
it, should be reserved, from the initial
charge in the rooster, and added near
the close of the roasting process. All
the ingredients which may be necessary
for fluxing the whole charge should be
present before the last heating. A small
portion of crushed Stag should be added
TO start the fritting or incipient fu.ion
The pres ence of a quantity of mono
sulphide OF iron sufficient to thoroughly
saturate the whole charge is necessary
for the complete and perfect sulphur
alton OF the valuable metals. The sub
stitution of any other metal which has a
less degree of sulphur affinity than that
of iron for the latter, in any particle OF
this sulphide, can only be effected by
direct chemical contact of the particles
of the metal and the sulphide at the
time of the oxidation of the iron, and
any copper. lead or silver sulphides,
which may have been previously form
ed, and which may not have come in
contact with the iron compound, to be
dissolved by it, will be reduced to metal
ON contact with the magnetic oxide of
iron IN presence of silica at fluxing
temperature. and SO will require result
phuTation. The amount of the iron
sulphide necessary for such saturation
Of the charge may be equal TO ten per
gent of its weight. or possibly, more.
When the matte product, from the
smelter, does not otherwise reach this
amount, a part of such matte may, con-
tnually, be crushed and returned to the
roasting charge after the addition of the
pyritous portion. If necessary for ma
king up the deficiency, one half of the
whole output may be thus returned.
The complete saturation Of the charge
with sulphides and the final presence OF
aquantity of magnetic oxide is necessary
even wien complete sulphuration of
the valuable metals has previously been
accomplished; for when any particle of
the valuable sulphides are exposed 10
the air, or other oxidizng infiuen ce.
before their collection by the ron sui
phide, such PARTICLES will then be redu-
ced to metal, or possibly, oxidized, and
the metallic particles SO formed will re-
quire re-sulphurizing. And further, as