IMPROVEMENTS IN THE MANUFACTURE OF SUL- PHATE OF ALUMINA
Year: 1878

page_text: LETTERS PATENT to Alexander Angus Croll, of Coleman Street, in the City of
London, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF SUL-
PHATE OF ALUMINA."
Sealed the 4th February 1879, and dated the 20th August 1878.
PROVISIONAL SPECIFICATION left by the said Alexander Angus Croll at the
Office of the Commissioners of Patents on the 20th August 1878.
ALEXANDER ANGUS CROLL, of Coleman Street, in the City of London. "IM-
PROVEMENTS IN THE MANUFACTURE OF SULPHATE OF ALUMINA.'
The object of the present Invention is to obtain various qualities of sulphate of
alumina from one and the same batch or manufacture of the salt when proceeding
according to the Invention for which Letters Patent were granted to me, bearing
date the 28th day of July 1877, No. 2884, and in a form or condition in which the
sulphate of alumina may be more readily and economically reduced to a divided
state for commercial purposes.
For this purpose I employ several saturating or combining vessels, in all of which
the like process is proceeding at or nearly the same time. Each of these vessels I
find it convenient to form of dimensions such as to operate on as large a charge in
each as convenient, but one of these vessels is however sufficiently large to contain
the matter not only of one charge, but is also in addition capable of containing the
contents of the other vessels, and these others are so placed in position that their
contents may be readily discharged into the larger vessel. Each of these vessels is
by preference surrounded by non-conducting material so as to prevent as much as
possible the escape of the heat therefrom.
When the whole of the clay intended for each vessel has been added to the acid
therein I cover such vessels with wood supporting a layer of charcoal, or with other
suitable non-conducting material. When rapid ebulition has ceased in the
respective saturating vessels I discharge the contents of each of the smaller ones
Prine A71

page_text: into the larger one. This larger vessel with its combined mass is maintained at its
highest point of heat, or as nearly so as possible, for several days by means of a
surrounding non-conducting jacket or medium of charcoal, or woollen or similarly
non-conducting material, and by a wooden or other suitable non-conducting cover
for the purpose of maintaining the fluidity of the mass to admit of the settlement
or subsidence of the insoluble substances contained therein. This settlement is
generally effected in a few days, upon which I proceed to tap the vessel at three or
four differant points in its height, the uppermost being at about one-fourth from
the top, and from these I allow the sulphate of alumina to flow out in succession,
commencing with the highest, in a stream or jet, or streams or jets, with the force
due to the head or upper pressure of the contained sulphate, which may then when
cooled be collected in a flaked or layered condition favorable to its ready and cheap
reduction to small pieces suitable for commerce.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Angus Croll in the Great Seal Patent Office on the 20th
February 1879.
ALEXANDER ANGUS CROLL, of Coleman Street, in the City of London.
PROVEMENTS IN THE MANUFACTURE OF SULPHATE OF ALUMINA,"
" IM-
The object of the present Invention is to obtain various qualities of sulphate of
alumina.from one and the same batch or manufacture of the salt when proceeding
according to the Invention for which Letters Patent were granted to me, bearing
date the 28th day of July 1877, No. 2884, and in a form or condition in which the
sulphate of alumina may be more readily and economically reduced to a divided
state for commercial purposes.
For this purpose I employ several saturating or combining vessels, in all of which
the like process is proceeding at or nearly the same time. Each of these vessels I
find it convenient to form of dimensions such as to operate on as large a charge in
each as convenient, but one of these vessels is however sufficiently large to contain
the matter not only of one charge, but is also in addition capable of containing the
contents of the other vessels, and these others are so placed in position that their
contents may be readily discharged into the larger vessel. Each of these vessels is
by preference surrounded by non-conducting material so as to prevent as much as
possible the escape of the heat therefrom.
When the whole of the clay intended for each vessel has been added to the acid
therein I cover such vessels with wood supporting a layer of charcoal, or with other
suitable non-conducting material. When, or even before, rapid ebullition has
ceased in the respective saturating vessels I discharge the contents of each of the
smaller ones into the larger one, care being taken to avoid the escape of the
material by ebullition from the larger vessel. This larger vessel with its combined
mass is maintained at its highest point of heat, or as nearly so as possible, for
several hours by means of a surrounding non-conducting jacket, or medium of
charcoal, or woollen or similarly non-conducting material, and by a wooden or
other suitable non-conducting cover for the purpose of maintaining the fluidity of
the mass. Supposing the quantity of material at any one time under operation
to be about 15 tons, the desired operation is generally effected in about twelve
hours, upon which I proceed to open sluices in the vessel at three or four or other
number of different points in the height of the material therein, and at about equal
distances apart in such height. From these openings I allow the sulphate of
alumina to flow, or it is drawn out in succession, commencing with the highest, and
it is then when cooled collected in a condition favorable to its ready and cheap
reduction to small pieces suitable for commerce.
The time during which such heat is maintained will vary with the quantity. of
material for the time under operation, the object being to maintain a high degree
of heat so as to secure the desired fluidity of the material as long as possible.
I would also state that although I prefer to employ several vessels in which the
operation is simultaneously proceeding I do not confine myself to such use, as one
large vessel might be employed.
Having thus described my Invention and means I adopt in carrying the same
into effect, I would have it understood that what I claim is, the improvements in
the manufacture of sulphate of alumina, whereby I am enabled to obtain various
qualities thereof from the same batch or manufacture, and in a form or condition in

page_text: which such sulphate of alumina may be more readily and economically reduced to
a divided state for commercial purposes, substantially as described.
In witness whereof, I, the said Alexander Angus Croll, have hereunto set my
hand and seal, this 18th day of February, in the year of our Lord One
thousand eight hundred and seventy-nine.