An Improved Process for the Extraction of Alumina from Bauxite and other substances.
Year: 1892

page_text: Date of Application, 13th Aug., 1892
Complete Specification Left, 10th May, 1893-Accepted, 10th June, 1893
PROVISIONAL SPECIFICATION.
An Improved Process for the Extraction of Alumina from Bauxite
and other substances.
Doctor ADOLF HAND, of Nieder Schönweide, Chemist, and Doctor HUGO
KUNHEIM, of 32, Dorotheenstrasse, Berlin, both in the Empire of Germany, do
hereby declare the nature of this invention to be as follows:-
The industrial extraction of alumina is generally effected by first producing
from the alumina material to be treated, more especially bauxite, an aluminate of the
alkalies or alkaline earths, and then working this aluminate to obtain alumina.
The alumina thus produced, however, always contains such quantities of silicic
acid (for 100 parts of Al,O, about 1 to 3 parts of SiO,) that it is unsuitable for
the manufacture of aluminium.
To prevent this quantity of silicic acid being contained in the alumina is the
object of the present invention, which is based upon the known behaviour of silicic
acid, of separating in the microcosmic salt-bead. The process forming the subject
of this invention comprises the addition of phosphoric acid to the ordinary molten
bauxite mass, produced particularly with alkalies or earthy alkalies, such as soda,
caustic soda, baryta as a material forming an aluminate, and the precipitation of
phosphoric acid in a subsequent stage of the process.
This addition of phosphoric acid, which may be used for this purpose either in
the free or combined state, can be made in the combined state in the form of
alkaline phosphate as well as by any other phosphate which is transformed by soda
into sodium phosphate. Thus I can smelt 1 equivalent of Al2O3 + Fe₂O, in bauxite
with 1 equivalent of sodium carbonate (Al,O, in slight excess) with addition of
sodium phosphate or a phosphate which has the above-mentioned property.
In these circumstances the quantity of the phosphate to be added depends on
the quantity of silicic acid which is usually contained in the aluminate liquors
without further addition in the smelting process. It has been found practical to
use for 1 equivalent of the silicic acid, which would be contained in the liquors
without the addition of phosphoric acid or phosphate, and the quantity of which
can be determined by a trial, 1 equivalents of phosphoric acid.
After being subjected to the action of the phosphoric acid, the aluminate liquors
generally contain but slight traces of silicic acid, although nearly the whole quantity
of the phosphoric acid is quantitatively separated by appropriate precipitating
agents, for instance by earth alkalies such as caustic lime.
Besides a small quantity of calcium aluminate, such quantities of silicic acid as
still remain in the aluminate liquors, are almost quantitatively precipitated at the
same time; the latter occurrence may even serve, as has also been found, for
almost completely freeing aluminate liquors containing silicic acid and obtained in
any desired manner, from the quantity of silicic acid they contain, by the addition
of a suitable quantity of soluble phosphate and by further treatment in the
prescribed manner. From the liquors separated by filtration from the phosphate
precipitate, the alumina is finally separated in the ordinary manner by precipitation
by means of carbonic acid.
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicants.

page_text: COMPLETE SPECIFICATION.
An Improved Process for the Extraction of Alumina from Bauxite
and other substances.
We, Doctor ADOLF HAND, of Nieder Schönweide, Chemist, and Doctor HUGO
KUNHEIM, of 32 Dorotheenstrasse, Berlin, both in the Empire of Germany, do
hereby declare the nature of this invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:-
The industrial extraction of alumina is generally effected by first producing from
the alumina material to be treated, more especially bauxite, an aluminate of the
alkalies or alkaline earths, and then working this aluminate to obtain alumina.
The alumina thus produced, however, always contains such quantities of silicic
unsuitable for the
acid (for 100 parts of Al,0), about 1 to 3 parts of SiO2) that it
manufacture of aluminium.
To prevent this quantity of silicic acid being contained in the alumina is the
object of the present invention, which is based upon the known behaviour of
silicic acid of separating in the microcosmic salt-bead. The process forming the
subject of this invention comprises the addition of phosphoric acid to the ordinary
molten bauxite mass, produced particularly with alkalies or earthy alkalies such
as soda, caustic soda or baryta, as a material for forming an aluminate, and the
precipitation of phosphoric acid in a subsequent stage of the process.
This addition of phosphoric acid, which may be used for this purpose either in
the free or combined state, can be made in the combined state in the form of
alkaline phosphate, as well as by any other phosphate which is transformed by soda
into sodium phosphate. Thus we can smelt equivalent of Al₂O + Fе,O, in
bauxite with 1 equivalent of sodium carbonate (Al,O, in slight excess) with the
addition of sodium phosphate or a phosphate which has the above-mentioned
property.
In these circumstances, the quantity of the phosphate to be added depends on
the quantity of silicic acid which is usually contained in the aluminate liquors
without further addition in the smelting process. It has been found practical to
use for 1 equivalent of the silicic acid, which would be contained in the liquors
without the addition of phosphoric acid or phosphate, and the quantity of which
can be determined by a trial, 1 equivalents of phosphoric acid.
After being subjected to the action of the phosphoric acid, the aluminate
liquors generally contain but slight traces of silicic acid, although nearly the whole
quantity of the phosphoric acid is quantitatively separated by appropriate
precipitating agents, for instance by earth alkalies, such as caustic lime.
Besides a small quantity of calcium aluminate, such quantities of silicic acid as
still remain in the aluminate liquors, are almost quantitatively precipitated at the
same time; the latter occurrence may even serve, as has also been found, for almost
completely freeing aluminate liquors containing silicic acid and obtained in any
desired manner, from the quantity of silicic acid they contain, by the addition of
a suitable quantity of phosphoric acid or soluble phosphate and by further treat-
ment in the prescribed manner. From the liquors separated by filtration from the
phosphate precipitate, the alumina is finally separated in the ordinary manner by
precipitation by means of carbonic acid.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is—
A process for the extraction of alumina practically free from silicic acid, by the
action of phosphoric acid, free or combined, either upon the decomposing mixture

page_text: containing the alumina materials, or upon aluminate liquors containing silicic acid,
and the precipitation of the dissolved phosphoric acid, the silicic acid still present
being precipitated at the same time.
1000
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicants.