CERTAIN IMPROVEMENTS IN THE TREATMENT OF ALUMINOUS EARTH, HAVING FOR THEIR OBJECT THE REMOVAL OF IRON THEREFROM
Year: 1877

page_text: LETTERS PATENT to Henry Bollmann Condy, of Battersea, in the County of
Surrey, for the Invention of "CERTAIN IMPROVEMENTS IN THE TREATMENT
OF ALUMINOUS EARTH, HAVING FOR THEIR OBJECT THE REMOVAL OF IRON
THEREFROM."
Sealed the 4th June 1878, and dated the 6th December 1877.
PROVISIONAL SPECIFICATION left by the said Henry Bollmann Condy at the
Office of the Commissioners of Patents on the 6th December 1877.
HENRY BOLLMANN CONDY, of Battersea, in the County of Surrey.
" CERTAIN
IMPROVEMENTS IN THE TREATMENT OF ALUMINOUS EARTH, HAVING FOR THEIR
OBJECT THE REMOVAL OF IRON THEREFROM."
These improvements have for their object the removal wholly or nearly wholly
of iron as it exists in aluminous earth, china or other clay, or other substances
employed to furnish alumina for the manufacture of alum, of any salt of alumina,
or of china, or any substance for which alumina, freo from iron may be required.
It is well known that in aluminous earth the iron exists in the state of an
oxide or salt of iron which is in a very insoluble condition, and has not hitherto
been separated from the alumina; and I separate the iron from the alumina by
effecting the reduction of the former from its difficultly soluble condition to a
state in which it becomes soluble in mineral acids. I accomplish this by means of
a suitable reducing agent or substance, such as carbon, sulphur, or the like, used in
a dry state, and heated with the clay; or by passing gases which have a reducing
property, such as sulphuretted hydrogen, carbonic oxide, or other gases having the
same property, through the clay, heated in a close furnace; or by treating the
aluminous earth with sulphuretted bydrogen, or sulphides of alkali, or alkaline
earth metals, or other analogous suitable compounds, cold or heated, with or without
pressure, with or without the addition of acid in combination with water; or I
employ for this same purpose of reducing iron to a soluble condition, hydrogen,
or sulphuretted hydrogen, or other substances having this reducing property,
employed in the nascent state.

page_text: When this treatment of aluminous earth is effected in a dry state, the sulphur
intended to reduce the oxide of iron is introduced in the shape of sulphide of sodium,
sulphide of calcium, or other suitable sulphide; or, in lieu of using the foregoing
sulphides, I generate any of these substances by adding to the aluminous earth
sulphate of soda, sulphate of line, or other suitable sulphate, together with carbon
or small coal, and heating the whole in a retort or closed furnace, which has the
same effect.
I may use the reducing agent in the nascent condition, such as nascent hydrogen
or nascent hydrogen in combination By nascent hydrogen in combination I mean
hydrogen compounds such as those of which sulphuretted hydrogen may be taken as
the type, employed in the nascent state.
By these means the oxide is reduced to protoxide or other oxide, sulphide, or salt
or iron soluble in acid.
As an illustration of my process I will proceed to describe a method of removing
oxide of iron from alumina or aluminous earth by means of nascent sulphuretted
hydrogen and mineral acid.
Having first ascertained by analysis the per-contage of oxido of iron, either free
or combined, existing in the material to be treated, I estimate the full quantity of
sulphuretted hydrogen for each unit of oxide of iron will be furnished by one and a
half times its weight of sulphide of sodium, from which it should be liberated by
means of an acid, such as hydrochloric acid, added in equivalent proportions, or in
about the proportion of one hundred-weight of hydrochloric acid of the specific
gravity of 1.160 to 40 pounds (lbs.) of sulphide of sodium, and I prefer to divide
the aluminous earth into two parts, to one of which I add the whole of the sulphide
of sodium required by the two parts, thoroughly incorporating the two substances,
and to the other half I add the whole of the hydrochloric acid, and thoroughly
incorporate these two substances. I then intimately mix these two previously divided
portions, first adding a small quantity of water. The mixture is then left to stand
a length of time sufficient to convert all the oxide of iron into sulphide of iron,
which I then dissolve out in very dilute hydrochloric or sulphuric acid, cmployed in
sufficient quantities to dissolve all the iron reckoned as oxide.
Before determining the requisite quantity of hydrochloric acid which is to be
added in the first place to that half of the material intended to bo so treated, it will
be necessary to ascertain if the earth or other substance contains lime or any other
basc capable of neutralizing any part of the hydrochloric acid intended to bo
employed to liberate sulphuretted hydrogen, and if so an addition must be made to
the quantity of hydrochloric acid which may be sufficient to neutralize the lime or
baso referred to.
I would wish it to be understood that I do not confine myself to the production
of sulphuretted hydrogen in the manner herein described, as the feature of my
Invention consists essentially in the method I adopt for the reduction of insoluble
iron or oxide of iron to the condition of oxide of iron or salt of iron soluble in acids
by means of hydrogen, sulphuretted hydrogen, or deoxidizing substances.
I would further remark that the process of reducing iron herein described is also
applicable to other substances or minerals containing oxide of iron which may bo
desirable to remove.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Henry Bollmann Condy in the Great Seal Patent Office on the 6th
June 1878.
23
HENRY BOLLMANN CONDY, of Battersea, in the County of Surrey. CERTAIN
IMPROVEMENTS IN THE TREATMENT OF ALUMINOUS EARTH, HAVING FOR THEIR
OBJECT THE REMOVAL OF IRON THEREFROM."
These improvements have for their object the removal wholly or nearly wholly
of iron as it exists in aluminiferous earth, china or other clay, or minerals employed
to furnish alumina for the manufacture of alum, or any salt of alumina, or of china,
or any substance for which alumina free from iron may be required.
In aluminiferous earth and clay the iron exists as in iron ore in the form of
peroxide, or hydrated peroxide, or protoxide combined with silica, titanic acid, or
other acids. It is in a state difficult to dissolve in mineral acids unless the acids are
applied concentrated at a boiling temperature or under pressure. When so treated
alumina will dissolve likewise, therefore no separation of the two substances can be
founded on the use of acids alone; but when the aluminiferous earth or mineral
containing the said substance is subjected to a preliminary treatment by which the
iron is rendered easily soluble in dilute mineral acids, its complete or partial reduc-
tion and subsequent separation from the alumina can be effected.
This treatment can be so modified that the alumina itself is brought to a condition
soluble in water, while the iron remains insoluble. I accomplish this by the use of
the same chemicals, but in much larger quantities, as herein-after described.
I carry into effect either of these modifications by the use of a suitable reducing
agent, such as sulphide of sodium, or other alcaline, or alcaline-earth sulphide used
in a dry state, and heated with the earth or substance to be treated in a closo
furnace; or by treating the aluminiferous earth in the wet state with sulphuretted
hydrogen, or sulphide of an alcali, or alcaline earth, or other analogous suitable com-
pound, mixed with or dissolved in water, cold or hot, and with or without
pressure.
When this treatment of aluminiferous earth is effected in the dry state, the sulphur
intended to reduce the oxide of iron is introduced in the shape of sulphide of sodium,
sulphide of potassium or calcium, or other suitable sulphide; or, in lieu of using the
foregoing sulphides, I generate any of them by adding to the aluminiferous earth
sulphate of soda, sulphate of potash, sulphate of lime, or other suitable sulphate,
together with carbon or small coal, and heat the mixture in a retort, or closed
vessel, or furnace to such a temperature as reduces the sulphate to the state of
sulphide; or, as a modification of the foregoing, I employ a soluble sulphide, such as
sulphide of sodium or potassium, heated in the dry state, with aluminiferous carth
employed in such quantity as is sufficient to form a compound, out of which I
dissolve the alumina, and at the same time I find the oxide of iron reduced to the
state of sulphide.
By these means I find in practice that a compound is formed consisting of sulphur,
sodium, and alumina, which is soluble in water, and of sulphido of iron, which is
insoluble in a solution of this salt, and can therefore be separated from it.
The soluble portion of this compound, which I designate as "sulpho-aluminate of
soda" or "sulpho-aluminate of potash, is then to be treated with acid, such as car-
bonic or acetic acid, which expels the sulphuretted hydrogen, combines with the
soda or potash, and precipitates the alumina in a pure state.
When treating the aluminiferous carth with sulphide of sodium or potassium with
the view of separating the alumina as "sulpho-aluminate of soda" or potash, I
employ a sufficient quantity of either of the sulphides to form a sulpho-aluminate
of soda or potash containing either one, two, or three atoms of base, that is, of
sulphide of sodium or potassium, as may be preferred, and I regulate the quantity
thus:-For fifty-one parts of alumina I employ thirty-nine parts of sulphide of

page_text: sodium to make a sulpho-aluminate of soda with one atom of base, soventy-eight
parts of sulphide of sodium to make the salt with two atoms of base, and one
hundred and seventeen parts of sulphide of sodium to make a salt containing three
atoms of base; for each thirty-nine parts of sulphur of sodium I use fifty-five parts
of sulphide of potassium to make a sulpho-aluminate of potash; or I employ an
equivalent quantity of sulphate of soda mixed with carbon, in which case, in lieu of
thirty-nine parts of sulphide of sodium, I use seventy-one parts of sulphate of soda
and twenty-four parts of small coal or other suitable form of carbon.
I may use as a reducing agent nascent hydrogen or nascent hydrogen in com-
bination. By nascent hydrogen in combination I mean hydrogen compounds such
as those of which sulphuretted hydrogen may be taken as the type, in the nascent
state.
By either of these means the oxide of iron is reduced to protoxide, sulphide, or a
salt of iron readily soluble in mineral acid.
After treating the clay or aluminiferous earth by any of the before-mentioned
methods with the object of reducing and rendering soluble the iron, but not obtaining
the "sulpho-aluminate of soda," I mix it with a quantity of water together with a
mineral acid, by preference hydrochloric acid, and heat it in order to dissolve and
remove the iron which has been rendered soluble. This solution I separate from the
alumina which remains undissolved by decantation or filteration, and repeat this
operation of adding water, agitating and decanting or filtering so long as the filterato
or decanted portion indicates pressence of iron in solution.
When my treatment of aluminiferous carth is to be effected in the wet state, I add
to the powdered mineral a suitable sulphide, preferably sulphide of sodium, either
dry, dissolved in or mixed with water, and well mix them together, adding if
necessary more water, whilst keeping the whole well agitated, in order to effect an
intimate, mixture. After this I heat the mixture (by preference under pressure of
steam) for about the space of two hours, during which time it is kept well agitated.
I then allow the earth or mineral to subside, and decant the supernatant liquor;
after which I wash the residue once or twice with water, and then digest it warın
with a mineral acid, by preferenco hydrochloric acid.
The offect of the foregoing treatment is as follows:-The oxide of iron, or the
greater part of the oxide of iron contained in the earth is brought to the condition
of sulphide of iron, and is then dissolved out by the warm dilute hydrochloric acid,
and removed by washing and filtration.
The proportions of sulphide (say sulphide of sodium) and of hydrochloric acid to
be employed will depend on the per-centage of iron contained in the aluminiferous
earth, and I have found in practice that it is the best to use them in the following
relative quantities, namely:-For each unit of metallic iron calculated from the
oxide of iron found by analysis, at least one and a half units or more of sulphide of
sodium (or about two units of sulphido of potassium), and after washing out most of
the excess of the same, to digest the earth with dilute hydrochloric acid, used in
sufficient quantity to dissolve out the iron and any remaining sulphide of sodium
which may be present, as well as other substances or constituents contained in the
earth, such as lime, magnesia, or alkalis which are easily soluble in acid, and which
it may be desirable to remove from the earth or clay, and to separate from the
alumina.
The solution I decant or filter, and wash the residual matter with water so long
as the decanted or filtered portion indicates the presence of iron.
I would remark that the process of reducing iron as herein described, though
specially adapted for the treatment of such minerals as bauxite, diaspore, and the
various kinds of clay extensively used in the arts, and herein referred to, is also
generally applicable to other substances or minerals containing oxide of iron which
it may be desirable to remove and soparate therefrom.
I would further remark that since filing my Provisional Specification it has come
to my knowledge that it has been proposed to purify bauxite by mixing it with coal
or other carbonaceous matters, and heating the mixture to bright redness for the

page_text: purpose of reducing the oxides of iron to a lower state of oxidation; or to heat the
bauxite to bright redness, and pass through the mass a current of hydrogen, car-
bonic oxide, or other reducing gases, after either of which treatments the bauxite
was to be treated with hydrochloric acid; but as this process was set forth and
described in my Provisional Specification in ignorance then of the fact that the samo
had been previously published, I make no claim thereto, but what I do claim as new
and as of my Invention is,-
First. Treating aluminiferous substances containing iron oxide with sulphuretted
hydrogen, sulphide of sodium or other suitable sulphide, or with nascent hydrogen,
for the purpose of subsequently separating the iron from the alumina, or vice versa.
Second. Separating the iron so rendered soluble from the alumina.
Third Dissolving by water the sulpho-aluminate of soda obtained by the before-
mentioned treatment, whereby the alumina becomes separated from the iron.
And, Fourth. Using the alumina so purified and freed from iron by these means
for the manufacture of pure alumina, its salts and compounds, all as herein-before
substantially described.
In witness whereof, I, the said Henry Bollmann Condy, have hereunto set my
hand and scal, this Fourth day of June, in the year of our Lord One thousand
eight hundred and seventy-eight
Witness,
THOMAS WRIGLEY,
Chancery Lane.
HENRY BOLLMANN CONDY. (LS.)