IMPROVEMENTS IN HYDRO-METALLURGY AND IN OBTAINING VALUABLE PRODUCTS THEREBY, ALSO IN APPARATUS USED FOR THESE PURPOSES
Year: 1876

page_text: LETTERS PATENT to Henry Hutchinson, of No. 116, Palmerston Buildings,
Old Broad Street, in the City of London, for the Invention of "IMPROVEMENTS
IN HYDRO-METALLURGY AND IN OBTAINING VALUABLE PRODUCTS THEREBY,
ALSO IN APPARATUS USED FOR THESE PURPOSES."
Sealed the 16th June 1876, and dated 1st January 1876.
PROVISIONAL SPECIFICATION left by the said Henry Hutchinson at the
Office of the Commissioners of Patents, on the 1st January 1876.
"6
HENRY HUTCHINSON, of No. 116, Palmerston Buildings, Old Broad Street, in the
City of London. IMPROVEMENTS IN HYDRO-METALLURGY AND IN OBTAINING
VALUABLE PRODUCTS THEREBY, ALSO IN APPARATUS USED FOR THESE PURPOSES."
This Invention has for its objects,―
First. Improvements in apparatus and mode of manufacturing sulphate of
Boda, sulphate of potash, sulphates of the alkaline earths, bydrochloric acid, and
chlorine.
Secondly. The treatment of metallic sulphides, with a view to extract and
separate from each other their metallic contents. The manufacture of metallic
sulphates, viz., sulphates of magnesia, alumina, iron, zinc, cobalt, nickel, copper,
silver, and lead. The separation of gold, the utilization of sulphurous acid gas in
the fabrication of the above chlorides and sulphates, and the concentration of
metals by a chemical method of treatment.
To obtain the alkaline sulphates
by the methods now in use recourse is had to decomposition of the alkaline
chlorides, and in some cases the chlorides of the alkaline earths, first, by means of
sulphuric acid; secondly, according to a more recent method by passing red-hot
sulphurous acid fumes over common salt, alone, or a mixture of common salt and
oxide of iron, or other oxide, or chloride of potassium moulded into various shapes,
such as bricks, perforated bricks, balls, squares and lumps, mixed with spent oxide
of iron and clay placed on perforated shelves in suitable decomposing chambers,
the object being to expose as large a surface as possible to the action of the sul-
phurous acid steam and air, and thus to produce sulphates of the alkalies without
first converting the sulphur into sulphuric acid at an immense cost in the erection
of leaden vitriol chambers.
Thirdly. By roasting a mixture of alkaline chorides and metallic sulphides in

page_text: reverberatory furnaces, the result being in each case the sulphate of the alkalies
or alkaline earths, and in this latter case the chloride of the heavy metals and
hydrochloric acid.
The object of the improvements by the present Invention is to avoid the costly
methods now in use by the introduction of a more economical and more perfect
mode of preparing the aforesaid chemical compounds by exposing alkaline chlorides,
or in some cases the chlorides of the alkaline earths mixed with metallic sulphides,
or a mixture of sulphide and oxide of iron, or sulphur or sulphurous acid fumes, or
any raw or artificial sulphides of the heavy metals in such a way as to give a much
larger oxidising and sulphating surface than is at present obtained.
The process may be conducted,-
First. By dropping or showering down a tower, shaft, or rotating cylindrical
furnace, or by projecting a blast of air and steam heated to redness across a finely
powdered mixture of alkaline chlorides, chloride of sodium, or chloride of potassium
with metallic sulphides, sulphur, or a mixture of sulphide and oxide of iron,
manganese, or zinc, which thus meets a current of red-hot air or steam, or red-hot
air, steam, and furnace gases, containing sufficient air to oxidise or convert the whole
of the sulphur of the sulphides into sulphuric acid, which, thus generated in the
descent decomposes the alkaline chlorides, converting the materials into alkaline
sulphates and the metals into chlorides or sulphates, and evolving hydrochloric acid
and chlorine as gas, which may be condensed in any convenient way and used as
herein-after stated. The fused mass, containing the alkaline sulphates and chlorides
of the heavy metals on the hearth of the furnace is raked out into suitable
lixiviating vats containing solvents (generated by this process), and the solution
obtained contains the alkaline sulphates and the chlorides of the heavy metals..
The insoluble matter contains the oxides of the heavy metals and gangue which
are separated by the methods hereafter referred to, and the alkaline solution is
crystallised or converted into black ash, or soda, as the case may be.
Secondly. The sulphurous acid gas, generated in the preliminary roasting of
native metallic sulphides in metallurgical works (which is now allowed to go to
waste, and become a source of loss and a nuisance to the neighbourhood in which it
is evolved), can be utilized and made available by the present Invention as a means
to extract metals and other useful products, which is accomplished in the following
way, namely, by allowing a finely powdered shower of the alkaline chlorides, or a
mixture of alkaline chlorides and oxide of iron, manganese, zinc, or other oxide,
to meet a red-hot current of sulphurous acid gas, air, and steam. The alkaline
chlorides thus exposed to an immense oxidising and sulphating surface are converted
into the sulphates of the said alkalies, namely, sulphate of soda and potash and
soluble chlorides of the metals, the oxides, hydrochloric acid, and chlorine, which
are evolved.
Thirdly. Sulphur, natural or artificial, may be utilized in the production of the
sulphates of the alkalies, by allowing powdered sulphur mixed with alkaline
chlorides or alkaline chlorides and oxide of iron, or other oxide, to shower down
(a shaft, tower, or other furnace heated to redness and meeting a current of red-hot
gases, steam, and air), or the sulphur may be first converted by burning into sul-
phurous acid gas, and then treated as already described.
The final results in either case are the same, viz., sulphates of the alkalies and
hydrochloric acid and chlorine evolved. The sulphates of the alkalies may be
dissolved out and crystallised, or if the product required be the sulphate of soda
in the form known under the name of salt cake, it may be raked out at once and
allowed to cool.
I now proceed to describe in detail the various methods I use for separating the
metallic contents of ores prepared by the said first part of this Invention.
The mixed sulphated and chlorodised ash obtained by the first treatment on the
hearth of the furnace may be supposed to contain the sulphates, chlorides, oxides,
and gangue of all the more commonly occuring metals, precious and base, viz.,
silver, gold, copper, lead, tin, bismuth, cadmium, antimony, arsenic, iron, manganese,

page_text: nickell, cobalt, zinc, alumina, chromium, magnesium, lime, magnesia, with the soluble
sulphates of soda and potash and salt used in excess of that required by the sulphur
to form sulphuric acid. The red-hot mass is now raked out into an iron tram car
with a sliding door in the bottom and at once conveyed to the lixiviating tanks
containing water, acid and water, or mother liquor and acid, or with the restored
hydrochloric acid from the condensing tower, or metallic solutions containing acids
restored by the use of sulphuretted hydrogen, the sliding door opened and the hot
sulphated ores allowed to drop slowly into the (if cold) liquor; by this mode of
working a large amount of heat is utilized and the tanks brought to the boiling
point. The sulphated mass is kept at the boiling temperature until the whole of
the soluble matters are extracted. The now saturated solution of the metallio
sulphates and chlorides is allowed to settle, next conveyed to the precipitation plant,
leaving the insoluble matters which are reserved for subsequent treatment.
I will now proceed to explain the separation of the metals from the metallic
solution thus obtained, and the utilisation of the products formed during the said
separation.
First. The solution is next precipitated in a novel way by allowing a shower of
the said metallic solution from a tank placed on the top of a tower arrangement
(containing flints or coke) to meet an upward current of sulphuretted hydrogen.
By manipulation in this way an immense surface is exposed to chemical action in
the shortest possible time, resulting in the perfect precipitation of the metals in the
state of metallic sulphides. The solution freed from the metals precipitated by the
aforesaid agent is filtered and allowed to settle, and the solution boiled by injecting
steam into the liquid, which blows off the last trace of sulphuretted hydrogen gas,
leaving for future use a liquid containing all the acid originally combined with the
said metals which were precipitated by the sulphuretted hydrogen, also the reduced
iron salts and the metals which cannot be precipitated by sulphuretted hydrogen,
namely, zinc, cobalt, nickel, alumina, magnesia, and sulphates and chlorides of the
alkalies (soda and potash). The insoluble matter left from the lixiviation of the
sulphated and chlorodised mass may now be treated with the acid solution restored
by the use of sulphuretted hydrogen, or by whatever method obtained, which is
effected by digesting the said insoluble matters at a boiling temperature. By this
treatment with acid liquid the whole of the remaining metals are extracted (that
is, in the event of acid or acid mother liquor not having been used in the first
lixiviation). The liquor obtained by the second lixiviation is again subjected to
the same treatment as the first (that is, with sulphuretted hydrogen), and if acid
with acid iron salts is again regenerated it is used over and over again as a
solvent, until sufficiently saturated with metal or metals and sulphate of the
alkalies or earths to crystallize on cooling, and to be found worth separating.
Secondly. The aforesaid metals are separated and concentrated from their
solutions without the use of sulphuretted hydrogen, and in some cases, when zinc
ores are under treatment, from iron, cobalt, nickel, and alumina.
The principal of the novelty of this part of the Invention consists in taking
advantage of the difference of affinity for sulphur shown by the metals when in
solution under suitable conditions.
The aforesaid separation may be accomplished, as well as the preparation of pure
solutions of zinc, from which pure oxide of zine may be made, and, if required, salts
of zinc or pure zinc, first, by carefully precipitating a portion of the solution under
treatment with an alkaline sulphide, or a sulphide of an alkaline earth, in sufficient
quantity to precipitate only the aforesaid metals (leaving, in the case of a zinc ore,
the whole of the zinc in solution); or by a second method, when zinc ores are the
subject of treatment, and the separation of the aforesaid metals is necessary, it is
preferred to precipitate a stock of pulpy sulphide of zinc (or sulphuretts of the
other metals if required for displacing) by an alkaline sulphide or a sulphide of an
alkaline earth. The mixed pulpy greyish black sulphides thus obtained are used
as a special reagent for the separation of silver, gold, copper, bismuth, lead,
cadmium, antimony, arsenic, platinum, iron, cobalt, and nickel from zinc or other
12

page_text: ores by adding the zinc sulphide to the solution of metals to be separated, assisted
by agitation and boiling. The zinc sulphide thus exposed in the presence of metals
having a greater affinity for sulphur than the zinc, &c., parts with its sulphur in
exchange with the aforesaid metals previously in solution, and are sulphuretted
and converted into the insoluble form and are separated, leaving a solution of zinc
freed from the other metals (which prevent the preparation of pure zinc) and the
salts of the alkalies and the alkaline earths.
A third method, designated the "silver and gold concentration method," also
based on the aforesaid difference of affinity for sulphur by these metals, is effected
by adding a very small amount of the pulpy sulphide of either zinc, iron, or copper
to the solution to be separated if zinc, iron, and copper ores are the ores to be
treated, or by the sulphide of the metal from which it is desired to displace others
from solution. The silver and gold are separated by this treatment, and the
remaining metals (copper group) finally precipitated by a further addition of a
metallic sulphide, in sufficient quantity so as to leave the zinc in solution.
zine may now be precitated by adding calcined magnesium, limestone, magnesia,
or carbonate of magnesia, or hydrate of lime in the form of milk of lime; or if
pure sulphide of zinc is required, by an alkaline or earthy sulphide, zinc is separated,
leaving in solution the chlorides of the alkaline earths and alkaline sulphates.
The
The solution obtained from the last separation is now evaporated to dryness.
During the said evaporation the sulphate of soda crystallises or salts out from
solution, and is constantly raked out and allowed to drain, and washed with a
saturated solution of sulphate of soda to wash out or displace the soluble chlorides
of the alkaline earths which adhere to the crystals of sulphate of soda. The
remaining solution now contains the chloride of magnesium, or chloride of calcium,
if magnesia or lime have been used to separate zinc. To restore the acid from this
compound and render available the said magnesia or lime for the precipitation of
metals, the solution is evaporated and heated to redness in a muffle furnace in
presence of steam and air, hydrochloric acid is obtained, which may be con-
densed, and magnesia remains, the acid volatilising and may be economically
condensed and used for lixiviating ores, prepared by the aforesaid first part of the
present Invention, by passing the said hydrochloric acid gas into a condensing
tower, meeting a shower of water (or if chlorides of any metal are required to be
made in an economical way), a mixture of water and oxide carbonate or silicate of
the metal, the chloride of which it is desired to make. If lime has been the
precipitant the chloride of calcium is more effectually decomposed by heat and
steam if previously mixed with a portion of the insoluble residue left after
extracting the metals, &c., by the aforesaid methods, namely, the oxide of iron,
alumina, and silicious gangue.
For the precipitation of the pulpy sulphides, the use of which has already been
described, a portion of the sulphate of soda obtained during the treatment of
metallic ores by the present Invention may be converted into sulphide of sodium by
heating to redness a mixture of the said sulphate of soda and coal or charcoal, or
by dropping the said mixture down a tower or shaft furnace (claim by this
Invention) in a reducing atmosphere. For use, the porous mass of coke and sodium
sulphide may be lixiviated with water and the solution used as claimed by this
Invention.
The sulphuretted hydrogen required by the present Invention may be made in
an economical and novel way in a clay retort or oven, by the distillation of a
mixture of metallic sulphides and bituminous coal, the latter in excess of the
sulphur contained in the sulphide used or (to prevent the formation of sulphide of
carbon) lignite, peat, wood, pitch, or any liquid, solid, or gaseous body, yielding
hydrocarbons when distilled at a red heat. Sulphuretted hydrogen and illumi-
nating gases are evolved which are conveyed to the precipitating tower to be used
as already described, and the illuminating gases used as a source of beat by
supplying the said gas through gas mains connected with the precipitating tower to
the furnaces.

page_text: Fourthly. Methods of separating the precious metals.The residue left in the
retort resulting from the generation of sulphuretted hydrogen may be utilised in
the concentration and separation of the precious and other metals (precipitated by
sulphuretted hydrogen) by mixing the said residue with the solutions obtained by
the aforesaid treatment. The sulphide of iron left in the residue is dissolved and
the sulphuretted hydrogen evolved.
Another novelty of the present Invention is in using the proto-sulphide of iron
to concentrate and separate the following metals, silver, gold, platinum, copper,
bismuth, lead, cadmium, antimony, and arsenic, by mixing the said proto-sulphide
of iron with solution of metals required to be separated, assisted by agitation and
boiling, the sulphides of the aforesaid metals are precipitated and the iron dissolves,
leaving zinc, nickel, cobalt, and the alkaline sulphates and chlorides in solution.
Sulphide of iron for this purpose may be prepared by distilling off half the sulphur
contained in iron pyrites, or, better, by dropping down the tower furnace a mixture
of iron pyrites and charcoal, or coal heated to redness in a reducing atmosphere;
the residue in either case is used for the separation of the metals, as already
described.
The following are examples of a number of cases wherein this new method of
separation of metals may be applied. The metals in solution under treatment being
in the form of chlorides or sulphates.
If a solution of sulphate of iron containing silver, gold, copper, bismuth, cadmium,
also nickel, cobalt, alumina, is to be separated, mix then with pulpy sulphide of iron
in quantities sufficient to separate alone the aforesaid metals, or with an alkaline
sulphide assisted by agitation and boiling; the clear solution contains purified
sulphate; the precipitate, the above named metals.
If a sulphate of copper solution containing some of the above, say silver and
gold, then add pulpy sulphide of copper, and silver and gold are separated.
If a zinc solution, then add pulpy zinc sulphide, and all the aforesaid metals are
displaced and concentrated along with the cobalt, nickel, iron, alumina, and
magnesia; the purified solution will contain the zinc, the precipate the iron and
other metals.
If a solution of manganese containing iron, cobalt, nickel, then add pulpy
sulphide of manganese, the aforesaid metals are precipitated and a purified solution
of manganese remains.
If a solution of cobalt with the aforesaid metals, then precipitate with pulpy
sulphide of cobalt, pure solution of cobalt remains.
If a solution of nickel, then add pulpy sulphide of nickel, the other metals are
separated.
If a silver solution, then add pulpy silver sulphide, the copper and others are
separated.
If a gold solution, then add pulpy sulphide of gold, silver, copper, &c., are sepa-
rated, and pure solution of gold remains.
The chlorine evolved during the decomposition of the secondary products
obtained by this Invention, or by whatever method obtained, may be by a novel
method utilised for the separation of gold and the preparation of the soluble
hypochlorites of magnesia, lime, soda, or potash. To effect the said preparation a
shower of the said magnesia, lime, soda, or potash is allowed to meet an ascending
current of the said chlorine. The solution of soluble hypochlorites thus obtained
is now used to dissolve out the free gold from the gold bearing ores, sulphurets, or
gold residues resulting from the aforesaid 1st. or 2nd. part of this Invention, to
extract the baser metals and sulphur and gold existing in the ore as sulphuret of
gold. The small amount of gold is thus exposed to an immense chlorinating
surface which dissolves the said gold; the solution of gold thus obtained (con-
taining insoluble matters, viz., oxide of iron and silica) is now allowed to separate
and the gold precipitated by sulphate of iron or sulphurous acid gas. If the latter
method be used, a novel way to effect the said separation of gold is to shower
down the tower arrangement (already described in another part) the said solution

page_text: of gold (however obtained) to meet an ascending current of sulphurous acid gas.
The precipitated gold is now allowed to collect by subsidence, drained, dried, and
melted, and the solution of perchloride of iron obtained as a secondary pro.luct (if
sulphate of iron has been used as a precipitant) evaporated to dryness, then
mixed with oxide of iron, or oxide of manganese and sand, and decomposed in the
presence of a current of red hot air and steam into hydrochloric acid and oxide
of iron, or by a second method into chlorine and oxide of iron, by treating the
aforesaid mixture at a red heat in the presence of red hot dry air, by using the
furnaces claimed by this Invention.
By another method the ore or residue containing gold (obtained from any
source) may first be mixed with a certain portion of oxide, manganese, and water,
and allowed to drop down the condensing tower arrangement, meeting an ascending
current of hydrochloric acid gas, chlorine is liberated by the action of the man-
ganese on the hydrochloric acid, and the gold is dissolved. The gold solution is
treated to separate the gold, as alredy described.
The second part of the present Invention has for its object the manufacture of
sulphates of the useful metals, and the treatment of ores with a view to extract
their metallic contents. To obtain commercially the sulphates enumerated in the
preamble to this Invention by the method now in use consists,-
Firstly. In acting upon the oxide, carbonate, silicate, chloride, phosphate, and
nitrate, by strong or weak sulphuric acid. The said sulphuric acid having first to
be made by the use of the well-known and costly leaden vitriol chambers.
Secondly. Without the use of vitriol chambers by carefully roasting the native
or artificial metallic sulphide, or a mixture of the sulphide and oxide of the metals
to be sulphated in the presence of air and steam, the same object being accom-
plished by the copperas maker by the well-known weathering process of sulphating
coal brasses or iron pyrites when exposed to slow oxidation in the presence of air
and moisture. The result being in each case the formation of soluble metallic
sulphates, insoluble oxide of iron, and undecomposed sulphides in uncertain and
varying proportion.
The novelty of the second part of the present Invention consists in avoiding the
now costly treatment by sulphuric acid, and the uncertain methods by sulphating
by oxidation in roasting by means of reverberatory and other imperfect furnaces
now in use by the introduction of sulphating furnaces better adapted to accom-
plish the objects stated in the second part of this Invention and well adapted for
general chemical purposes.
To give an illustration of the application of the improved method of sulphating
ores and extracting metals claimed by this part of the Invention, the ores to be
treated may be supposed to contain one or all the commonly occuring metallic sul-
phides, or if desired to extract or sulphate the metals in non-sulphurous ores, such
as the native or artificial oxides, carbonates, or silicates of the metallic base by the
present Invention; then mix the said oxide, carbonate, or silicate with an excess
of native or artificial metallic sulphides in such proportion as to yield an excess
of sulphuric acid when submitted to the sulphating process to combine with the
metallic bases under treatment.
The ores in all cases when treated by this method to be finally powdered, the
success of this system of treatment depending on the said fineness (it is found from
practice 1,600 holes to the square inch is the best size for the sieve). The ores
thus prepared are now submitted to the sulphating process which is accomplished
substantially as is described in the first part of this Invention, and is effected by
showering the said sulphides, or a mixture of oxide, silicate, carbonate, chloride, or
phosphate with an excess of sulphide down the shaft or tower capable of receiving
the said ore or mixture of ores, to meet a current of red-hot air and steam, or
red-hot air, steam, and furnace gases containing sufficient air to convert the
sulphur of the metallic sulphides into sulphuric acid and the base into oxides.
The acid generated in its descent combines with the aforesaid metallic bases, con-
verting the said bases into a mixture of one or more of soluble and insoluble

page_text: sulphates, oxides, gangue, and if an excess of sulphide has been used, a trace of
sulphurous acid which can be utilised in another way.
The chlorides of magnesium and calcium (by whatever method obtained) may
be in an economical way decomposed, and converted into sulphate of magnesia
(Epsom salts) and sulphate of lime (gypsum), by the methods set forth in the first
part of the present Invention, by dropping down the shaft furnace a mixture of
the said dry chlorides and iron pyrites or zinc blend, meeting red-hot air and
steam; the sulphates and hydrochloric acid are the result. The latter may be con-
densed or utilised in the production of chlorides by the improved tower condenser
arrangement, as already set forth; or thirdly, by allowing the dry chlorides to
meet an ascending current of red-hot sulphurous acid, gas, air, and steam,
the result is the same as the aforesaid, viz., sulphate of magnesia, which may be
separated by lixiviation from the oxide of iron and crystallised; if sulphate of lime
and oxide of iron it may be either dried and calcined for "Venetion red," or sus-
pended in boiling water and mixed with finely powdered magnesium limestone, the
sulphate of lime is decomposed and converted into carbonate of lime, and the
sulphuric acid is taken up by the magnesia giving in solution Epsom salts, and an
insoluble residue of oxide of iron and carbonate of lime, which may be dried and
calcined to improve colour.
If the sulphurous acid process has been used then it is only required to dissolve
the resulting sulphate in water and crystallise. The sulphurous acid gas may be
also utilised in a novel way in the preparation of the hyposulphites of alkalies and
alkaline earths required by this system of extracting metals.
The hyposulphites of magnesia and lime are made by showering down the tower
apparatus a mixture of water, lime, magnesia, calcined limestone, and sulphide of
calcium, meeting an upward current of sulphurous acid gas; the soluble hypo-
sulphites are formed.
The sulphites and bisulphites of calcium and magnesia are made by using
water, and the lime or magnesium alone meeting a current of sulphurous acid gas.
If hyposulphite of soda is required, treat a mixture of lime or magnesia, sulphide
of lime, and sulphate of soda to the current of hot sulphurous acid gas, hyposulphite
of soda and insoluble gypsum is the result, and may be lixiviated and evaporated for
the solid compound or used in the liquid state.
If rich silver ores have been treated by the first part of this Invention, a large
part of the chloride of silver formed remains in the residue to make a perfect
separation, then treat with bisulphite and sulphite of the alkalies or alkaline earths
(made in the utilisation of sulphurous acid gas), the silver is dissolved and may be
precipitated by boiling or with sulphide of lime.
Secondly. The hyposulphites of calcium and magnesia may be used to extract the
chloride of silver from the residue, the silver precipitated by sulphide of lime, the
sulphide then roasted in a reverberatory furnace lined with a thick brasque
composed of charcoal and oxide of iron, the silver is reduced and cast into ingots.
Rich lead sulphide obtained during the treatment of ore by any of the concentration
methods may also be smelted along with spongy iron as above.
If spongy iron has been used to precipitate the copper obtained in solutions by
these methods, the resulting solution of chloride or sulphate of iron is utilised by
treating ores of copper, lead, zinc, and in the state of oxides, carbonates, or silicates,
with the said chloride and sulphate evaporating the mixture, until the whole of the
iron is converted into insoluble red oxide, and the acid combines with the aforesaid
metals or other metals, or by another method decompose by heat into ferric oxide
and chlorine, as already referred to.
Chloride and sulphate of lead may also be separated in the same way from the
insoluble residue by the use of the hyposulphite of lime and magnesia when
treating rich ores of lead, the solution obtained may then be precipitated with
sulphide of lime.
If the manufacture of sulphate of iron from iron pyrites (copperas) be made the
starting point of the improvement claimed by this Invention, then the manu-

page_text: facturing and metallurgical chemist has in his power a method (by secondary
reaction) of the fabrication of most of the useful sulphates already named.
1st. Sulphate of iron is made by showering down the shaft furnace finely
divided iron pyrites, meeting red hot air and steam or a mixture of iron pyrites and
oxide of iron.
'
2nd. Sulphate of zinc, by the same method, using zinc blend or zinc blend and
previously roast zinc blend, by the same furnace.
3rd. The oxides, silicate, and carbonate of zinc may be sulphated by first mixing
the above with iron pyrites in excess and treated as aforesaid
4th. Copper pyrites and regulus may be sulphated by the aforesaid treatment or
by dry air alone into oxide of copper and iron.
5th. Oxide, carbonate, silicate, phosphate, arseniate, and native oxychloride of
copper may be sulphated by using an excess of iron pyrites, as aforesaid.
6th. Sulphate of alumina may be made by showering down the shaft or tower
furnace a mixture of iron pyrites, clay, kaolin, or aluminous shale, found in the coal
measures, meeting red hot air and steam, or by the other method already described,
namely, a mixture of aluminous material, &c., and burnt iron pyrites or oxide of
iron, meeting red hot sulphurous acid gas, steam, and air, or the roasted aluminous
material may be mixed with water and boiled to dryness with the sulphate of iron
generated by No. 1 (above), until the sulphate of iron is decomposed into insoluble
red oxide of iron and soluble sulphate of alumina, and if alum is the ultimate object,
mix with sulphate of ammonia.
The application of the aforesaid furnaces and methods to the treatment of
arsenical ores containing gold, silver, copper, bismuth, lead, tin, cobalt, nickel, zinc,
iron, and gangue.
The methods now in use for the treatment of the aforesaid metals consists in
roasting the ores rich in arsenic and sulphur in the ordinary mundic kilns, the said
arsenic and sulphur supplying the fuel necessary to complete the roasting; or second,
by a reverberatory furnace when the arsenic and sulphur are insufficient for
combustion.
The products obtained from the "mundic kiln roasting," namely, arsenious acid
which is condensed, and sulphurous acid gas (which is allowed to escape and pollute
the air) are free from coal soot (but it is a slow method).
The volatile products obtained from the roasting of arsenical ores, when assisted
by coal are contaminated with coal soot and require to be re-sublimed. By either
of these methods the roastings are very slow and uncertain.
By adopting the furnaces and methods herein already described in the aforesaid
part of this Specification, a much larger quantity of ore may be roasted per day
than has hitherto been accomplished, and at the same time, effecting a more perfect
calcination with less fuel (if poor in arsenic and sulphur), and producing a
practically pure arsenious acid by one calcination at a considerable saving of fuel
and time.
The arsenical ores under treatment are first powdered fine enough to pass
through a sieve (it is found 1600 holes to the square inch a suitable size). This
may be easily done by the well known Blake's crusher, and "Carrs' distintegrator."
The finely powdered ore is showered down the furnaces, the principle of which has
already been described, meeting red-hot air or red-hot furnace gases and air;
intense and perfect combustion is the result (burning with scintillations like
ignited rockets), arsenious acid, sulphurous acid gas, and the oxides of metals,
present are formed. The arsenious acid is condensed in dust chambers forming
part of the apparatus attached to the furnaces, and the sulphurous acid gas is
allowed to escape into the condensing towers (already described), meeting a shower
of milk of lime, milk of magnesium, calcined limestone, or other alkaline earths and
alkalies; the result in this case is the economical production of the hyposulphites
(the use of which has already been claimed), or it may be used for extracting the
metals, gold, silver, copper, and lead, from the residues of arsenical ores; or secondly,
if the arsenical ores are deficient in combustible elements, mix with iron pyrites,

page_text: copper pyrites, zinc blend, or in some cases with powdered coal, and if it is desired
at one and the same calcination to sulphate some of the aforesaid metals, viz.,
copper, silver, zinc, then allow steam to mingle (which is superheated in its ascent
through the furnace) with the said mixture, soluble sulphates may be then
extracted by water from the residue.
I now proceed to explain in detail the improved method of extracting the metals
from the residue left from the calcination of arsenical ores.
The general or preparatory treatment may be thus accomplished.
1st. The calcined residue is mixed with sufficient iron pyrites (or in fact worked
along with other pyrites by the second part of this Invention, viz, sulphating) to
yield enough sulphuric acid when submitted to the said furnaces to combine with
the metals to form soluble sulphates when lixiviated with water or acid solutions.
The insoluble residue will be found to contain the gold, tin, oxide of iron, and
gangue, and may be reserved for subsequent treatment.
By a second treatment of the residues, which is based on the economical
fabrication of sulphate of soda, mix the calcined residue with sufficient metallic
sulphides (in preference, iron pyrites, copper pyrites, or zinc blend) containing
sufficient sulphur to decompose and combine with the amount of salt required to
convert the metals into chlorides and the salt into sulphate, dropping the said
mixture down the aforesaid furnace under conditions already described, sulphates
are first formed, which are in their turn converted by the decomposition of the sult
into chlorides (hydrochloric acid and chlorine escaping if iron oxides have been
generated during the calcination by excessive heat). The acid may be utilised as
set forth for the better extraction of metals from insoluble residues, or the
hydrochloric acid gas is allowed to mingle by vaporisation with a descending
shower of calcined residue under conditions already set forth, or the residue may
be allowed to shower down the condensing tower mixed with water; the acid gas
converts the oxides into chlorides of the metals, the greater part of the oxide of
iron remaining in the insoluble condition along with the gold, tin, and gangue.
A third novel way of decomposing arsenical ores containing more sulphur than
arsenic (poor ore inay first be mixed with pyrites) by showering down the tower
furnace the said ore, or mixture of ores and powdered coal, meeting in this case a
reducing atmosphere, volatile combustible hydrocarbon gases, sulphur and sulphide
of arsenic are the result, and an insoluble residue of metallic sulphides and gangue
freed from arsenic deposited.
The inflammable gases, sulphur and sulphide of arsenic (after depositing any
metallic sulphides mechanically carried over into the dust chambers) are best
utilised by making the said inflammable mixture a source of heat, and for this
purpose can be burnt with air and used to boil down the weak liquid obtained
during any of the aforesaid operations, the products resulting from the said
burning mixture then convey to the arsenical chambers to deposit the arsenious
acid, and the sulphurous acid is converted into useful compounds as already set
forth. The residue from this third method (sulphides and gangue) may be either
converted into chlorides, or sulphates, or oxides in the manner set forth.
By another novel method arsenical residues and iron ores, irony gossans, or any
other irony residues containing gold, silver, or copper, worth extracting, or which
have been found not to pay by the methods of extraction now in use, may
be treated (by a method found to pay) by converting the said irony ores, &c.
'spongy iron" (by whatever method obtained), or by the furnace herein
recommended.
into "
The gold, silver, copper, are extracted and the iron utilised as follows:-
1st. By using the said spongy iron to precipitate metals from metallic solutions,
the gold, silver, and copper are separated and concentrated along with the metals
to be precipitated, the iron is dissolved.
Secondly. The spongy iron is dissolved in dilute sulphuric acid, allowing a little
of the said spongy iron to remain undissolved, or mixed with a little sulphide of
iron, sulphuretted hydrogen is evolved. The residue will contain the gold, silver,

page_text: copper, &c. and the solution the sulphate of iron (copperas), and may be crystallised
or utilised by any of the other methods already described by secondary reaction.
Thirdly. Dissolving in hydrochloric acid allowing a little to remain in the
residue which will contain gold, silver, copper, and the solution chloride of iron.
The said spongy iron is claimed in making pyrolignite of iron by digesting in
crude or refined pyroligneous acid, the said spongy iron leaving a little undissolved.
The residue will contain the gold, silver, and copper; the solution the pyrolignite
of iron.
By another novel method the irony, arsenical, or other residue containing gold,
silver, copper, and tin (if only gold it may be ground fine and then concentrated
by washing), the gold extracted by amalgamation, and the tin from the residue by
smelting.
By another novel way, when the arsenical or irony residue contains gold and
tin, and the iron oxide has been separated by washing, which is based on the
fabrication of carbonate of soda, and the utilising of sulphate of soda. For this
purpose the gold and tin bearing residue is mixed with dry sulphate of soda, small
coal, anthracite or charcoal, and fluxed in a furnace. Sulphide of sodium is formed,
and the gold, tin, and tungsten converted into soluble sulphides, this alkaline
sulphuretted matt may be treated,-
1st. By placing the said sulphuretted matt on perforated shelves in a room
through which passing carbonic acid gas with steam.
2nd. The matt is lixiviated with boiling water, and the clear solution obtained
allowed to shower down the condensing tower, meeting a current of carbonic acid
gas. The result in each case is the same, namely, carbonate of soda, sulphuretted
hydrogen evolved, and gold and tin precipitated. The tin may then be separated
from the gold by dissolving in hydrochloric acid; the tin dissolves and the gold
remains. The solution of carbonate of soda may then be crystallised, and the
evolved sulphuretted hydrogen used to precipitate metals from solutions obtained
during any part of these processes.
By another method in which sulphurous acid gas is utilised allowing a shower of
the alkaline solution of sulphides of gold and tin to meet an upward current of
sulphurous acid gas, hyposulphite of soda is formed, and the solution of gold and
tin is then boiled, the gold and tin are precipitated, or the solution may be mixed
with sulphide of calcium or sodium, and the gold and tin are separated.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Henry Hutchinson in the Great Seal Patent Office on the 1st July
1876.
HENRY HUTCHINSON, of No. 116, Palmerston Buildings, Old Broad Street, in the
City of London. "IMPROVEMENTS IN HYDRO-METALLURGY AND IN OBTAINING
VALUABLE PRODUCTS THEREBY, ALSO IN APPARATUS USED FOR THESE PURPOSES."
This Invention has for its objects,-
First. Improvements in apparatus and mode of manufacturing sulphate of soda,
sulphate of potash, sulphates of the alkaline earths, hydrochloric acid, and
chlorine.
Secondly. The treatment of metallic sulphides with a view to extract and
separate from each other their metallic contents. The manufacture of metallic
sulphates, viz., sulphates of magnesia, alumina, iron, zinc, cobalt, nickel, copper,
silver, and lead, the separation of gold, the utilisation of sulphurous acid gas in the
fabrication of the above chlorides and sulphates, and the concentration of metals by
a chemical method of treatment. To obtain the alkaline sulphates by the methods
now in use, recourse is had to the decomposition of the alkaline chlorides, and in
some cases the chlorides of the alkaline earths, first, by means of sulphuric acid;

page_text: secondly, according to a more recent method by passing red-hot sulphurous acid
fumes over common salt alone, or a mixture of common salt and oxide of iron, or
other oxide or chloride of potassium moulded into various shapes, such as bricks,
perforated bricks, balls, squares and lumps, mixed with spent oxide of iron, and
clay placed on perforated shelves in suitable decomposing chambers, the object being
to expose as large a surface as possible to the action of the sulphurous acid, steam,
and air, and thus to produce sulphates of the alkalies without first converting the
sulphur into sulphuric acid at an immense cost in the erection of leaden vitriol
chambers.
Thirdly. By roasting a mixture of alkaline chlorides and metallic sulphides in
reverberatory furnaces, the result being in each case the sulphate of the alkalies or
alkaline earths, and in this latter case the chloride of the heavy metals and hydro-
chloric acid.
The object of the improvements by the present Invention is to avoid the costly
methods now in use by the introduction of a more economical and more perfect
mode of preparing the aforesaid chemical compounds by exposing alkaline chlorides
or in some cases the chlorides of the alkaline earths mixed with metallic sulphides,
or a mixture of sulphide and oxide of iron, or sulphur, or sulphurous acid fumes,
or any raw or artificial sulphide of the heavy metals in such a way as to give a
much larger oxidizing and sulphating surface than is at present obtained.
The process may be conducted,—
First. By dropping or showering down a tower, shaft, or rotating cylindrical
furnace, or by projecting a blast of air and steam heated to redness across a finely
powdered mixture of alkaline chlorides, chloride of sodium, or chloride of potassium,
with metallic sulphides, sulphur, or a mixture of sulphide and oxide of iron,
manganese, or zinc, which thus meets a current of red-hot air or steam, or red-hot
air, steam, and furnace gases, containing sufficient air to oxidise or convert the
whole of the sulphur of the sulphides into sulphuric acid, which thus generated in
the descent decomposes the alkaline chlorides, converting the materials into alkaline
sulphates, and the metals into chlorides or sulphates, and evolving hydrochloric acid
and chlorine as gas which may be condensed in any convenient way and used as
herein-after stated. The fused mass containing the alkaline sulphates and chlorides
of the heavy metals on the hearth of the furnace is raked out into suitable lixi-
viating vats containing solvents (generated by this process), and the solution
obtained contains the alkaline sulphates and the chlorides of the heavy metals.
The insoluble matter contains the oxides of the heavy metals and gangue, which
are separated by the methods hereafter referred to, and the alkaline solution is
crystallised or converted into black ash or soda, as the case may be.
Secondly. The sulphurous acid gas generated in the preliminary roasting of
native metallic sulphides in metallurgical works (which is now allowed to go to
waste and become a source of loss and a nuisance to the neighbourhood in which it
is evolved) can be utilized and made available by the present Invention as a means
to extract metals and other useful products, which is accomplished in the following
way, namely, by allowing a finely powdered shower of the alkaline chlorides, or a
mixture of alkaline chlorides and oxide of iron, manganese, zinc, copper, or other
oxide to meet a red-hot current of sulphurous acid gas, air, and steam. The
alkaline chlorides thus exposed to an immense oxidizing and sulphating surface are
converted into the sulphates of the said alkalies, namely, sulphate of soda and
potash, and soluble chlorides of the metals, the oxides, hydrochloric acid and
chlorine, which are evolved.
Thirdly. Sulphur, natural or artificial, may be utilised in the production of the
sulphates of the alkalies by allowing powdered sulphur mixed with alkaline
chlorides, or alkaline chlorides and oxide of iron, or other oxide to shower down
(a shaft, tower, or other furnace heated to redness, and meeting a current of red-
hot gases, steam, and air), or the sulphur may be first converted, by burning, into.
sulphurous acid gas, and then treated as already described.
The final results in either case are the same, viz., sulphates of the alkalies and _

page_text: hydrochloric acid and chlorine evolved. The sulphates of the alkalies may be
dissolved out and crystallised, or if the product required be the sulphate of soda, in
the form 'known under the name of salt cake, it may be raked out at once and
allowed to cool.
Before proceeding to describe in detail the various methods I use for separating
the metallic contents of ores prepared by the said first part of this Invention, I will
describe in detail my tower furnaces, which are shewn in the Drawings hereunto
annexed.
DRAWING No. 1.
Represents one of the tower furnaces claimed by this Invention.
"A" is the top
of the furnace showing the sifter, which is worked by appropriate machinery (not
shown). The furnace is heated by placing fuel in the gas producers, marked "B."
The fire-bars H on which the fuel rests are hollow pipes pierced with holes to
admit a current of steam and air, which keeps the bars cool and also superheats
the steam and air before its entrance, and mixes with the fuel
The ash-pit also contains hot-air passages, in which are placed another set of
superheating steam pipes which also injects a stream of hot air along with the
steam, marked I. The same hot-air passages, shown at "J," burn the hydrocarbon
gases from the producer. A portion of the evolved gases pass up through the arch
of the furnace, marked "K," and also mingle with the hot air and supherheated steam
when required for sulphating and chloridising ores.
The fuel boxes "G" are used when a reducing atmosphere is required when making
spongy metals. "L" are air conveyances passages, not only serving for the purpose of
heating the air gas before its entrance to the furnace, but also acts as expansion
spaces, allowing the brickwork to contract and expand without falling to pieces,
which if not made so would result in the structure cracking in every direction.
The said spaces also allow of the steam and air, when newly built, to escape.
The gas inlets E are for heating the furnace without the use of the gas producers
at the bottom. The gas required for this purpose may be made by an independent
gas producer, and on its entrance to the furnace may be before ignition allowed to
mingle with the hot air in the hot-air space "I." "F" are gas jet holes. Cold air
may be let in from the outside air holes "M."
When it is found convenient to heat the furnace without the gas producers at the
bottom of the furnace, gas from another source may be let in at the bottom forming
the ash-pit, marked " gas inlet." "N" is the outlet for the calcined materials, and
when accumulated sufficiently may be dropped out into an iron tram car, run
under the arch bottom, and conveyed to lixiviating for after treament, &c.

page_text: on. The steam in its entrance to the furnace draws cold air "D" through the various
airways shown, and is superheated and brought to the same heat as the furnace.
If the furnace is required to calcine regulus, sulphuretts, calamine, or blend, then
use the furnace without steam, and admit as much air as possible. Gas may be let
into the furnace from other gas generators through E, which will take fire at F.
The ore in dropping through this intense red-hot flame containing an excess of red-
hot air will be completely oxidised, and the sulphur, &c., driven off.
If it be desired to sulphate and chloridise, as has already been described, then
turn on the superheated steam mixed with excess of air. The compounds will be
sulphated or chloridised.
If a reducing atmosphere is required for the production of spongy metals, such as
spongy copper, spongy iron, and spongy zinc, then stop off the airways and steam
(getting the furnace up to temperature previously); next mix the compound desired
to reduce with coal, charcoal, or anthracite coal, and drop it down the tower by the
aid of the sifter; then open the F air holes. The ascending reducing gas from the
gas producer is then heated to intense whiteness, also the mixture of ore and
carbon. As soon as the mixture passes the combustion holes it meets a reducing
atmosphere, and by the time the mixture reaches the bottom of the furnace is
reduced to metals. Additional fuel may be sifted by the fuel boxes G.
In making sulphuretted hydrogen by this furnace the air holes will not be
required, but in its stead a little steam.
No. 3.
No. 3 is a tower or shower furnace, which I also claim, heated by gas alone from
an independent gas producer placed in any position. The principle of the action of
this furnace is the reverse of Nos. 1 and 2. The draught, instead of going upwards,
travels downwards. The heating gas is let in at "B," and in its ascent through air
spaces makes its way out at the gas jets, and is then mixed with sufficient air for
combustion, and ignited, and makes its way downwards to the flue and dust
chamber "D," "D," "D." The substances to be treated are then allowed to drop from
the sifter, and be mingled and carried down by the ignited gases, steam and air.
The pipes and series of holes marked E, E, may be used for the introduction of
sulphurous acid gas when it is desired to decompose common salt by sulphurous
acid gas and make sulphate of soda or any of the sulphates already named, and for
that purpose may be allowed first to mix with red-hot air in the hot air spaces.
The salt, &c., is then sifted down.

page_text: being, the same as in L, to superheat steam and air. The steam and air jets drive
the charged ore or materials into the red-hot chamber "J" to the dust chamber, and
is there collected. H shows a section of the steam fire-bar. Of course any of the
air holes or passages can be stopped up at will by suitably made stoppers.
The sifting tower with the gas generator and steam and air apparatus may be
used by adapting the said parts to a revolving cylinder lined with fire-bricks, and
may be attached to the part K. There may be used the usual fire-place, if required,
at the opposite end, below which the ore falls into the ore chamber.
I will now describe in detail the various methods I use for separating the
metallic contents of ores prepared by the first part of this Invention.
The mixed sulphated and chloridised ash obtained by the first treatment on the
hearth of the furnace may be supposed to contain the sulphates, chlorides, oxides,
and gangue of all the more commonly occurring metals, precious and base, viz.,
silver, gold, copper, lead, tin, bismuth, cadmium, antimony, arsenic, iron, manganese,
nickel, cobalt, zinc, alumina, chromium, magnesium, lime, magnesia, with the
soluble sulphates of soda, and potash, and salt used in excess of that required by the
sulphur to form sulphuric acid. The red-hot mass is now raked out into an iron
tram car with a sliding door in the bottom, and at once conveyed to the lixiviating
tanks, containing water, acid and water, or mother liquor and acid, or with the
restored hydrochloric acid from the condensing tower, or metallic solutions con-
taining acids restored by the use of sulphuretted hydrogen, the sliding door opened,
and the hot sulphated ores allowed to drop slowly into the (if cold) liquor. By this
mode of working a large amount of heat is utilized, and the tanks brought to the
boiling point. The sulphated mass is kept at the boiling temperature until the
whole of the soluble matters are extracted. The now saturated solution of the
metallic sulphates and chlorides is allowed to settle, next conveyed to the preci-
pitation plant, leaving the insoluble matters, which are reserved for subsequent
treatment.
I will now proceed to explain the separation of the metals from the metallic
solution thus obtained, and the utilization of the products formed during the said
separation.
First. The solution is next precipitated in a novel way by allowing a shower of
the said metallic solution from a tank placed on the top of a tower arrangement
(containing flints or coke) to meet an upward current of sulphuretted hydrogen.
By manipulation in this way an immense surface is exposed to chemical action in
the shortest possible time, resulting in the perfect precipitation of the metals in the
state of metallic sulphides. The solution freed from the metals precipitated by the
aforesaid agent is filtered or allowed to settle, and the solution boiled by injecting
steam into the liquid, which blows off the last trace of sulphuretted hydrogen gas,
leaving for future use a liquid containing all the acid originally combined with the
said metals, which were precipitated by the sulphuretted hydrogen, also the reduced
iron salts and the metals which cannot be precipitated by sulphuretted hydrogen,
namely, zinc, cobalt, nickel, alumina, magnesia, and sulphates, and chlorides of the
alkalies (soda and potash). The insoluble matter left from the lixiviation of the
sulphated and chloridised mass may now be treated with the acid solution, restored
by the use of sulphuretted hydrogen or by whatever method obtained, which is
effected by digesting the said insoluble matters at a boiling temperature. By this
treatment with acid liquid the whole of the remaining metals are extracted (that is
in the event of acid or acid mother liquor not having been used in the first
lixiviation). The liquor obtained by the second lixiviation is again subjected to
the same treatment as the first (that is with sulphuretted hydrogen), and if acid
with acid iron salts is again regenerated it is used over and over again as a solvent
until sufficiently saturated with metal or metals, and sulphate of the alkalies or
earths to crystallise on cooling and to be found worth separating.
Secondly. The aforesaid metals are separated and concentrated from their
solutions without the use of sulphuretted hydrogen, and in some cases when zinc
ores are under treatment from iron, cobalt, nickel, and alumina,

page_text: The principle of the novelty of this part of the Invention consists in taking
advantage of the difference of affinity for sulphur shown by the metals when in
solution under suitable conditions.
The aforesaid separation may be accomplished as well as the preparation of pure
solutions of zinc, from which pure oxide of zinc may be made, and if required salts
of zinc or pure zinc, first, by carefully precipitating a portion of the solution under
treatment with an alkaline sulphide or a sulphide and oxide of alkaline earth in
sufficient quantity to precipitate only the aforesaid metals (leaving in the case of a
zinc ore the whole of the zinc in solution) or by a second method when zinc ores
are the subject of treatment, and the separation of the aforesaid metals is necessary
it is preferred to precipitate a stock of pulpy sulphide of zinc, or a mixture of
sulphide and oxide (or sulphuretts of the other metals if required for displacing) by
an alkaline sulphide or an oxide and sulphide of an alkaline earth. The mixed
pulpy greyish black sulphides, &c., thus obtained are used as a special reagent for
the separation of silver, gold, copper, bismuth, lead, cadmium, antimony, arsenic,
platinum, iron, cobalt, and nickel, from zinc or other ores by adding the said zinc
sulphide, to the solution of metals to be separated assisted by agitation and
boiling. The zinc sulphide, &c., thus exposed in the presence of metals having a
greater affinity for sulphur than the zinc parts with its sulphur in exchange with
the aforesaid metals previously in solution, and are. sulphuretted and converted
into the insoluble form and are separated, leaving a solution of zinc (in the case of
a zinc being treated) freed from the other metals (which prevent the preparation
of pure zinc) and the salts of the alkalies and alkaline earths.
A third method designated the "silver and gold concentration method" also
based on the aforesaid difference of affinity for sulphur by these metals, is effected
by adding a very small amount of the pulpy sulphide of either zinc, iron, or copper
to the solution to be separated. If zinc, iron, and copper ores are the ores to be
treated, or by the sulphide of the metal from which it is desired to displace others
from solution. The silver and gold are separated by this treatment, and the
remaining metals (copper group) finally precipitated by a further addition of a
metallic sulphide in sufficient quantity, so as to leave the zinc and other metals in
solution. The zine may now be finally precipitated by adding calcined magnesium,
limestone, magnesia, or carbonate of magnesia, or hydrate of lime in the form of
milk of lime, or if pure sulphide of zinc is required by an alkaline or earthy
sulphide zinc is separated, leaving in solution the chlorides of the alkaline earths
and alkaline sulphates.
The solution obtained from the last separation is now evaporated to dryness;
during the said evaporation the sulphate of soda crystallises or salts out from
solution, and is constantly raked out, allowed to drain, and washed with a saturated
solution of sulphate of soda to displace or wash out the soluble chlorides of the
alkaline earths which adhere to the crystals of sulphate of soda. The remaining
solution now contains the chloride of magnesium or chloride of calcium if magnesia
or lime have been used to separate zinc. To restore the acid from this compound
and render available the said magnesia or lime for the precipitation of metals, the
solution is evaporated and treated to redness in a muffle furnace in presence of steam
and air. Hydrochloric acid is obtained, which may be condensed, and magnesia
remains, the acid volatilizing, and may be economically condensed and used for
lixiviating ores prepared by the aforesaid first part of the present Invention, by
passing the said hydrochloric acid gas into a condensing tower, meeting a shower
of water (or if chlorides of any metal are required to be made in an economical
way) a mixture of water and oxide carbonate or silicate of the metal, the chloride
of which it is desired to make. If lime has been the precipitant the chloride of
calcium is more effectually decomposed by heat and steam if previously mixed
with a portion of the insoluble residue left after extracting the metals, &c. by the
aforesaid methods, namely, the oxide of iron, alumina, and silicious gangue.
For the precipitation of the pulpy sulphides the use of which has already been
described, a portion of the sulphate of soda obtained during the treatment of

page_text: metallic ores by the present Invention may be converted into sulphide of sodium
by heating to redness a mixture of the said sulphate of soda, and coal (or charcoal
or by dropping the said mixture down a tower or shaft furnace (claim by this
Invention) in a reducing atmosphere. For use the porous mass of coke and sodium
sulphide may be lixiviated with water, and the solution used as claimed by this
Invention.
The sulphuretted hydrogen required by the present Invention may be made in
an economical and novel way in a clay retort or oven by the distillation of a
mixture of metallic sulphides and bituminous coal, the latter in excess of the
sulphur contained in the sulphide used (or to prevent the formation of sulphide of
carbon) lignite, peat, wood, pitch, or any liquid, solid or gaseous body yielding
hydrocarbons when distilled at a red heat. Sulphuretted hydrogen and a mixture
of heating and illuminating gases are evolved, which are conveyed to the precipi-
tating tower to be used as already described, and the heating and illuminating
gases used as a source of heat by supplying the said gas through gas mains
connected with the precipitating tower to the furnaces.
Fourthly. Methods of separating the precious metals.-The residue left in the
retort resulting from the generation of sulphuretted hydrogen may be utilized in
the concentration and separation of the precious and other metals (precipitated by
sulphuretted hydrogen) by mixing the said residue with the solutions obtained by
the aforesaid treatment. The sulphide of iron left in the residue is dissolved and
the sulphuretted hydrogen evolved effectually precipitating the aforesaid group of
metals.
Another novelty of the present Invention is in using the proto-sulphide of iron
to concentrate and separate the following metals:-Silver, gold, platinum, copper,
bismuth, lead, cadmium, antimony, and arsenic, by mixing the said proto-sulphide
of iron with acid solutions of metals required to be separated, assisted by agitation
and boiling, the sulphides of the aforesaid metals are precipitated, and the iron
dissolves, leaving zinc, nickel, cobalt, and the alkaline sulphates and chlorides in
solution. Sulphide of iron for this purpose may be prepared by distilling off half
the sulphur contained in iron pyrites, or better, by dropping down the tower
furnace a mixture of iron pyrites and charcoal or coal heated to redness in a
reducing atmosphere; the residue in either case is used for the separation of the
metals, as already described.
The following are examples of a number of cases wherein this new method of
separation of metals may be applied. The metals in solution under treatment
being in the form of chlorides or sulphates.
If a solution of sulphate of iron containing silver, gold, copper, bismuth,
cadmium; also nickel, cobalt, alumina, is to be separated, mix them with pulpy
sulphide of iron in quantities sufficient to separate alone the aforesaid metals, or
with an alkaline sulphide, assisted by agitation and boiling. The clear solution
contains purified sulphate. The precipitate the above named metals.
If a sulphate of copper solution containing some of the above, say silver and
gold, then add pulpy sulphide of copper, and silver and gold are separated.
If a zinc solution, then add pulpy zinc sulphide, and all the aforesaid metals are
displaced and concentrated along with the cobalt, nickel, iron, alumina, and
magnesia. The purified solution will contain the zinc. The precipitate the iron
and other metals.
If a solution of manganese, containing iron, cobalt, nickel, then add pulpy
sulphide of manganese. The aforesaid metals are precipitated and a purified
solution of manganese remains.
If a solution of cobalt, with the aforesaid metals, then precipitate with pulpy
sulphide of cobalt. Pure solution of cobalt remains.
If a solution of nickel, then add pulpy sulphide of nickel. The other metals
are separated.
If a silver solution, then add pulpy silver sulphide. The copper and others are
separated.

page_text: If a gold solution, then add pulpy sulphide of gold; silver, copper, &c., are
separated, and pure solution of gold remains.
The chlorine evolved during the decomposition of the secondary products
obtained by this Invention, or by whatever method obtained, may be by a novel
method utilised for the separation of gold and the preparation of the soluble
hypochlorites of magnesia, lime, soda, or potash. To effect the said preparation a
shower of the said magnesia, lime, soda, or potash is allowed to meet an ascending
current of the said chlorine. The solution of soluble hypochlorites thus obtained
is now used to dissolve out the free gold from the gold bearing ores, sulphurets, or
gold residues resulting from the aforesaid first or second part of this Invention to
extract the baser metals and sulphur and gold existing in the ore as sulphuret of
gold. The small amount of gold is thus exposed to an immense chlorinating
surface which dissolves the said gold, the solution of gold thus obtained (containing
insoluble matters, viz., oxide of iron and silica) is now allowed to separate and the
gold precipitated by sulphate of iron or sulphurous acid gas. If the latter method
be used a novel way to effect the said separation of gold is to shower down the
tower arrangement (already described in another part) the said solution of gold
(however obtained) to meet an ascending current of sulphurous acid gas. The
precipitated gold is now allowed to collect by subsidence, drained, dried, and
melted, and the solution of perchloride of iron obtained as a secondary product (if
sulphate of iron has been used as a precipitant) evaporated to dryness, then mixed
with oxide of iron or oxide of manganese and sand, and decomposed in the
presence of a current of red-hot air and steam into hydrochloric acid and oxide of
iron, or by a second method into chlorine and oxide of iron, by treating the
aforesaid mixture at a red heat in the presence of red-hot dry air by using the
furnaces claimed by this Invention.
By another method the ore or residue containing gold (obtained from any
source) may first be mixed with a certain portion of oxide manganese and water
and allowed to drop down the condensing tower arrangement, meeting an ascending
current of hydrochloric acid gas. Chlorine is liberated by the action of the
manganese on the hydrochloric acid and the gold is dissolved. The gold solution
is treated to separate the gold, as already described.
The second part of the present Invention has for its object the manufacture of
sulphates of the useful metals and the treatment of ores with a view to extract
their metallic contents. To obtain commercially the sulphates enumerated in the
preamble to this Invention by the method now in use consists,-
Firstly. In acting upon the oxide, carbonate, silicate, chloride, phosphate, and
nitrate by strong or weak sulphuric acid, the said sulphuric acid having first to
be made by the use of the well-known and costly leaden vitriol chambers.
Secondly. Without the use of vitriol chambers by carefully roasting the native
or artificial metallic sulphide or a mixture of the sulphide and oxide of the metals
to be sulphated in the presence of air and steam. The same object being
accomplished by the copperas maker by the well-known weathering process of
sulphating coal, brasses, or iron pyrites when exposed to slow oxidation in the
presence of air and moisture. The result being in each case the formation of
soluble metallic sulphates, insoluble oxide of iron, and undecomposed sulphides in
uncertain and varying proportion.
The novelty of the second part of the present Invention consists in avoiding the
now costly treatment by sulphuric acid, and the uncertain methods of sulphating
by oxidation in roasting by means of reverberatory and other imperfect furnaces
now in use, by the introduction of sulphating furnaces better adapted to accomplish
the objects stated in the second part of this Invention, and well adapted for general
chemical purposes.
To give an illustration of the application of the improved method of sulphating
ores and extracting metals claimed by this part of the Invention. The ores to be
treated may be supposed to contain one or all the commonly occurring metallic
sulphides, or if desired to extract or sulphate the metals in non-sulphurous ores,.

page_text: such as the native or artificial oxides, carbonates, or silicates of the metallic base by
the present Invention. Then mix the said oxide, carbonate, or silicate with an
excess of native or artificial metallic sulphides in such proportion as to yield an
excess of sulphuric acid, when submitted to the sulphating process to combine with
the metallic bases under treatment.
The ores in all cases when treated by this method to be finely powdered, the
success of this system of treatment depending on the said fineness (it is found from
practice that 1600 holes to the square inch is the best size for the sieve). The ores
thus prepared are now submitted to the sulphating process which is accomplished
substantially as is described in the first part of this Invention, and is effected by
showering the said sulphides or a mixture of oxide, silicate, carbonate, chloride, or
phosphate with an excess of sulphide down the shaft or tower capable of receiving
the said ore or mixture of ores to meet, a current of red-hot air and steam, or red-
hot air, steam, and furnace gases containing sufficient air to convert the sulphur of
the metallic sulphides into sulphuric acid, and the base into oxides.
The acid generated in its descent combines with the aforesaid metallic bases,
converting the said bases into a mixture of one or more of soluble and insoluble
sulphates, oxides, gangue, and if an excess of sulphide has been used a trace of
sulphurous acid which can be utilised in another way.
The chlorides of magnesium and calcium (by whatever method obtained) may be
an economical way decomposed and converted into sulphate of magnesia (Epsom
salts), and sulphate of lime (gypsum) by the methods set forth in the first part of
the present Invention; by dropping down the shaft furnace a mixture of the said
dry chlorides and iron pyrites or zinc blend meeting red-hot air and steam, the
sulphates and hydrochloric acid are the result. The latter may be condensed or
utilized in the production of chlorides by the improved tower condenser arrange-
ment as already set forth; or thirdly, by allowing the dry chlorides to meet an
ascending current of red-hot sulphurous acid gas, air, and steam, the result is the
same as the aforesaid, viz., sulphate of magnesia which may be separated by
lixiviation from the oxide of iron and crystallised, if sulphate of lime and oxide of
iron it may be either dried and calcined for "Venetian red," or suspended in boiling
water and mixed with finely powdered magnesium limestone, the sulphate of lime
is decomposed and converted into carbonate of lime, and the sulphuric acid is taken
up by the magnesia giving in solution Epsom salts, and an insoluble residue of
oxide of iron and carbonate of lime which may be dried and calcined to improve
colour.
If the sulphurous acid process has been used then it is only required to dissolve
the resulting sulphate in water and crystallise. The sulphurous acid gas may be
also utilised in a novel way in the preparation of the hyposulphites of alkalies, and
alkaline earths required by this system of extracting metals.
The hyposulphites of magnesia and lime are made by showering down the tower
apparatus a mixture of water, lime, magnesia, calcined limestone, and sulphide of
calcium meeting an upward current of sulphurous acid gas. The soluble hypo-
sulphites are formed.
The sulphites and bisulphites of calcium and magnesia are made by using water,
and the lime or magnesium alone meeting a current of sulphurous acid gas.
If hyposulphite of soda is required treat a mixture of lime or magnesia, sulphide
of lime and sulphate of soda to the current of hot sulphurous acid gas. Hypo-
sulphite of soda and insoluble gypsum is the result, and may be lixiviated and
evaporated for the solid compound or used in the liquid state.
If rich silver ores have been treated by the first part of this Invention, a large
part of the chloride of silver formed remains in the residue to make a perfect
separation, then treat with bisulphite and sulphite of the alkalies or alkaline earths
(made in the utilization of sulphurous acid gas), the silver is dissolved and may be
precipitated by boiling or with sulphide of lime.
Secondly. The hyposulphites of calcium and magnesia may be used to extract the
chloride of silver from the residue, the silver precipitated by sulphide of lime, the

page_text: sulphide then roasted in a reverberatory furnace lined with a thick brasque com-
posed of charcoal and oxide of iron, the silver is reduced and cast into ingots. Rich
lead sulphide obtained during the treatment of ore by any of the concentration
methods herein named may also be smelted along with spongy iron obtained by the
use of the furnaces claimed by this Invention, as above.
If spongy iron has been used to precipitate the copper obtained in solutions by
these methods the resulting solution of chloride or sulphate of iron is utilised by
treating ores of copper, zinc, lead, and in the state of oxides, carbonates, or silicates,
with the said chloride and sulphate, evaporating the mixture until the whole of the
iron is converted into insoluble red oxide, and the acid combines with the aforesaid
metals or other metals, or by another method decompose by heat into ferric oxide
and chlorine, as already referred to.
Chloride and sulphate of lead may also be separated in the same way from
insoluble residues by the use of the hyposulphite of lime and magnesia, when
treating rich ores of lead, the solution obtained may then be precipitated with
sulphide of lime and boiling.
If the manufacture of sulphate of iron from iron pyrites (copperas) be made the
starting point of the improvement claimed by this Invention, then the manu-
facturing and metallurgical chemist has in his power a method (by secondary
reaction) of the fabrication of most of the useful sulphates already named.
First. Sulphate of iron is made by showering down the shaft furnace finely
divided iron pyrites, meeting red-hot air and steam, or a mixture of iron pyrites
and oxide of iron.
Second. Sulphate of zinc by the same method using zinc blend, and sulphate of
iron or zinc blend and previously roast zinc blend and sulphate of iron by the
same furnace.
Third. The oxides, silicate, and carbonate of zinc may be sulphated by first mixing
the above with iron pyrites in excess, and treated as aforesaid.
Fourth. Copper pyrites and regulus may be sulphated by the aforesaid treatment
(or by dry air alone into oxide of copper and iron).
Fifth. Oxide, carbonate, silicate, phosphate, arseniate, and native oxychloride or
copper may be sulphated by using an excess of iron pyrites as aforesaid or sulphate
of iron, and roasting the mixture as aforesaid until the sulphate is decomposed into
red oxide of iron, and the copper into sulphate of copper.
Sixth. Sulphate of alumina may be made by showering down the shaft or tower
furnace a mixture of iron pyrites, clay, kaolin, or aluminous shale found in the coal
measures, meeting red-hot air and steam, or by the other method already described,
namely, a mixture of aluminous material, &c., and burnt iron pyrites or oxide of
iron melting red-hot sulphurous acid gas, steam, and air, or the roasted aluminous
material may be mixed with water and boiled to dryness with the sulphate of iron
generated by No. 1 (above), until the sulphate of iron is decomposed into insoluble
red oxide of iron and soluble sulphate of alumina, and if alum is the ultimate object
mix with sulphate of ammonia.
The application of the aforesaid furnaces and methods to the treatment of
arsenical ores containing gold, silver, copper, bismuth, lead, tin, cobalt, nickel, zinc,
iron, and gangue.
The methods now in use for the treatment of the aforesaid metals consists in
roasting the ores rich in arsenic and sulphur in the ordinary mundic kilns; the
said arsenic and sulphur supplying the fuel necessary to complete the roasting; or
second, by a reverberatory furnace when the arsenic and sulphur are insufficient
for combustion.
The products obtained from the "mundic kiln roasting," namely, arsenious acid,
which is condensed, and sulphurous acid gas (which is allowed to escape and polute
the air) are free from coal soot (but it is a slow method).
The volatile products obtained from the roasting of arsenical ores when assisted
by coal are contaminated with coal soot, and require to be resublimed. By either
of these methods the roastings are very slow and uncertain.

page_text: By adopting the furnaces and methods herein already described in the aforesaid
part of this Specification, a much larger quantity of ore may be roasted per day
than has hitherto been accomplished, and at the same time effecting a more
perfect calcination with less fuel (if poor in arsenic and sulphur), and producing a
practically pure arsenious acid by one calcination at a considerable saving of fuel
and time.
The arsenical ores under treatment are first powdered fine enough to pass through
a sieve (it is found 1600 holes to the square inch a suitable size); this may be
easily done by the well-known Blake's crusher and " Carr's disintegrator." The
finely powdered ore is showered down the furnaces, the principle of which has
already been described, meeting red-hot air or red-hot furnace gases and air;
intense and perfect combustion is the result (burning with scintillations like
ignited rockets); arsenious acid, sulphurous acid gas, and the oxides of metals
present are formed. The arsenious acid is condensed in dust chambers forming
part of the apparatus attached to the furnaces, and the sulphurous acid gas is
allowed to escape into the condensing towers (already described), meeting a shower.
of milk of lime, milk of magnesium, calcined limestone, or other alkaline earths
and alkalies; the result in this case is the economical production of sulphites and
hyposulphites (the use of which has already been claimed); or it may be used for
extracting the metals, gold, silver, copper, and lead, from the residues of arsenical
ores; or secondly, if the arsenical ores are deficient in combustible elements, mix
with iron pyrites, copper pyrites, zinc blend, or in some cases with powdered coal,
and if it is desired at one and the same calcination to sulphate some of the afore-
said metals, viz., copper, silver, zinc, then allow steam to mingle (which is super-
heated in its ascent through the furnace) with the said mixture; soluble sulphates
may be then extracted by water from the residue.
I now proceed to explain in detail the improved method of extracting the metals
from the residue left from the calcination of arsenical ores.
The general or preparatory treatment may be thus accomplished:-
First. The calcined residue is mixed with sufficient iron pyrites (or in fact
worked along with other pyrites by the second part of this Invention, viz., sul-
phating) to yield enough sulphuric acid, when submitted to the said furnaces, to
combine with the metals to form soluble sulphates when lixivated with water or
acid solutions. The insoluble residue will be found to contain the gold, tin, oxide
of iron, and gangue, and may be reserved for subsequent treatment.
By a second treatment of the residues which is based on the economical fabrica-
tion of sulphate of soda (by the first part of this Patent), mix the calcined residue
with sufficient metallic sulphides (in preference iron pyrites, copper pyrites, or zinc
blend), containing sufficient sulphur to decompose and combine with the amount
of salt required to convert the metals into chlorides and the salt into sulphate,
dropping the said mixture down the aforesaid furnace under conditions already
described. Sulphates are first formed which are in their turn converted by the
decomposition of the salt into chlorides (hydrochloric acid and chlorine escaping if
iron oxides have been generated during the calcination by excessive heat). The
acid may be utilised, as set forth, for the better extraction of metals from insoluble
residues, or the hydrochloric acid gas is allowed to mingle by vaporisation with a
descending shower of calcined residue, under conditions already set forth, or the
residue may be allowed to shower down the condensing tower mixed with water; the
acid gas converts the oxides into chlorides of the metals, the greater part of the oxide
of iron remaining in the insoluble condition along with the gold, tin, and gangue.
A third novel way of decomposing arsenical ores containing more sulphur than
arsenic (poor ore may first be mixed with pyrites) by showering down the tower
furnace the said ore or mixture of ores and powdered coal, meeting in this case a
reducing atmosphere. Volatile combustible hydrocarbon gases, sulphur, and
sulphide of arsenic are the result, and an insoluble residue of metallic sulphides and
gangue freed from arsenic deposited.
The inflammable gases, sulphur and sulphide of arsenic (after depositing any

page_text: metallic sulphides mechanically carried over into the dust chambers) are best
utilised by making the said inflammable mixture a source of heat, and for this
purpose can be burnt with air and used to boil down the weak liquid obtained
during any of the aforesaid operations; the products resulting from the said
burning mixture then convey to the arsenical chambers to deposit the arsenious
acid, and the sulphurous acid is converted into useful compounds, as already set
forth. The residue from this third method (sulphides and gangue) may be eithor
converted into chlorides, or sulphates, or oxides, in the manner set forth.
By another novel method arsenical residues and iron ores, irony gossans, or any
other irony residues containing gold, silver, or copper worth extracting, or which
have been found not to pay by the ordinary methods of extraction now in use, may
be treated (by a method found to pay) by converting the said irony ores, &c. into
spongy iron"
(by whatever method obtained), or by the furnace herein
recommended.
"
The gold, silver, copper are extracted, and the iron utilised as follows:-
First. By using the said spongy iron to precipitate metals from metallic solutions
the gold, silver, and copper are separated and concentrated along with the metals
to be precipitated; the iron is dissolved.
Secondly. The spongy iron is dissolved in dilute sulphuric acid, allowing a little
of the said spong iron to remain undissolved or mixed with a little sulphide of
iron; sulphuretted hydrogen is evolved. The residue will contain the gold, silver,
copper, &c., and the solution the sulphate of iron (copperas), and may be crystallised
or utilised by any of the other methods already described by secondary reaction.
Thirdly. Dissolving in hydrochloric acid, allowing a little to remain in the
residue, which will contain gold, silver, copper, and the solution chloride of iron.
The said spong iron is claimed in making pyrolignite of iron by digesting in crude
or refined pyroligenous acid the said spongy iron, leaving a little undissolved. The
residue will contain the gold, silver, and copper; the solution, the pyrolignite of
iron.
By another novel method the irony, arsenical, or other residue containing gold,
silver, copper, and tin (if only free gold it may be ground fine and then con-
centrated by washing), the gold extracted by amalgamation, and the tin from the
residue by smelting.
By another novel way when the arsenical or irony residue contains gold and tin,
and the iron oxide has been separated by washing, which is based on the fabrication
of carbonate of soda and the utilising of sulphate of soda. For this purpose the
gold and tin bearing residue is mixed with dry sulphate of soda, small coal,
anthracite, or charcoal, and fluxed in a furnace. Sulphide of sodium is formed,
and the gold, tin, and tungsten converted into soluble sulphides. This alkaline
sulphuretted matt may be treated,-
First. By placing the said sulphuretted matt on perforated shelves in a room
or tower arrangement through which is passing carbonic acid gas with steam.
Second. The matt is lixiviated with boiling water, and the clear solution
obtained allowed to shower down the condensing tower, meeting a current of
carbonic acid gas. The result in each case is the same, namely, carbonate of soda,
sulphuretted hydrogen evolved, and gold and tin precipitated. The tin may then
be separated from the gold by dissolving in hydrochloric acid; the tin dissolves and
the gold remains. The solution of carbonate of soda may then be crystallised, and
the evolved sulphuretted hydrogen used to precipitate metals from solutions
obtained during any parts of these processes.
By another method in which sulphurous acid gas is utilised, allowing a shower of
the alkaline solution of sulphides of gold and tin to meet an upward current of
sulphurous acid gas, hyposulphite of soda is formed, and the solution of gold and
tin is then boiled, the gold and tin are precipitated, or the solution may be mixed
with sulphide of calcium or sodium and the solution boiled; gold and tin are
separated.

page_text: Having thus described the nature of my Invention, and the manner of performing
the same, I would have it understood that I claim, the processes, and apparatus,
and mode of use of the same, substantially as herein-before described.
In witness whereof, I, the said Henry Hutchinson, have hereunto set my
hand and seal, this Thirtieth day of June, in the year of our Lord One
thousand eight hundred and seventy-six.