Improvements in the Manufacture of Potash Alum and Alumina
Year: 1893

page_text: Date of Application, 31st Jan., 1893-Accepted, 4th Mar., 1893
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Potash Alum and Alumina,
I JOSEPH HEIBLING of 21 Boulevard Poissonniere Paris in the Republic of
France Chemist 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 :-
This invention relates to the manufacture of potash alum by exposing a mixturo
of clay sulphate of ammonia and sulphate of potash to a temperature of about
300 degrees centigrade and obtaining alumina by treating the said potash alum with
a lye as hereinafter described.
In carrying out this invention in practice the operations are conducted as next
hereinafter described but I do not limit myself to the details which may be modified
according to circumstances without affecting the principle of my invention.
A clay is employed containing a known percentage or proportion of alum and in
proportion to the alum therein three molecular proportions of sulphate of ammonia
and one molecular proportion of sulphate of potash are mixed therewith. These
materials are first stirred or kneaded and afterwards made up or moulded in the
form of hollow bricks or blocks in a suitable brick making machine for example.
The hollow blocks thus obtained may be piled in a receptacle which can be mado
of sheet iron coated with tar or pitch and carried upon a truck running on rails or
they may be piled directly on the truck if preferred according to the construction
of the furnace.
When the blocks are placed in receptacles carried upon trucks the latter
are placed in a furnace or heating chamber maintained at a temperature of from about
275 to 300 degrees centigrade each receptacle being placed in communication with
the exterior by means of a discharge pipe.
In case the blocks are placed directly upon the trucks the latter are taken
directly into a chamber maintained at the aforesaid temperature the said chamber
being closed and communicating with the exterior through a discharge pipe.
At the temperature specified the sulphate of ammonia is decomposed; the
ammonia escapes through the discharge pipes and can be collected in an ordinary
ammonia condenser. The sulphuric acid of the sulphate of ammonia passes at
first to the sulphate of potash which becomes acid sulphate of potash and the latter
in the presence of the alumina in the clay at the specified temperature becomes
neutralised by the alumina and forms a double sulphate of alumina and potash or
potash alum.
The operation may occupy from about two to four hours according to the thickness
of the mass and the division or arrangement of the hollow blocks. It is known to
be terminated when the escape of ammonia ceases.
The truck is then removed from the furnace and its contents are discharged into
a trough or basin containing a sufficient quantity of water the temperature of which
is raised by the presence of the heated mass of materials. On stirring the blocks
crumble and the potash alum enters into solution.
The liquid is treated in a centrifugal machine acting as a filter and is collected
in a clear condition along with the washing water in a second basin or trough in
which the iron is eliminated in the form of Prussian blue by adding yellow prussiate
of potash.
b
The materials being treated in a centrifugal machine the prussiate of potash is
regenerated by treating the residue of Prussian blue with alkaline carbonate in the
usual way.
The clear liquid free from iron is delivered from the centrifugal machine into a
third basin or receptacle in which the whole of the ammonia given off' in the distilling

page_text: process is added to it. The result of this treatment is that the whole of the alumina
is precipitated. After treatment in the centrifugal machine it is dried or in case
the sulphate is to be obtained, it is placed in sulphuric acid.
The liquid remaining contains the whole of the regenerated sulphate of ammonia
and sulphate of potash employed in the operation. This liquid is treated in an
evaporating apparatus with triple effect of the Picard or other system in order to
reduce its volume as much as possible and can be used again for treating a fresh
supply of the clay.
The alkaline carbonate employed to regenerate the prussiate of potash is recovered
in the form of a useful sulphate.
The residue of the clay consists of almost pure silica and can be used for making
highly refractory bricks for Siemens furnaces and metallurgical purposes.
Acid sulphate of potash obtained in the first place either by heating a mixture
of the two salts aforesaid or otherwise may be employed in place of the mixture of
the two sulphates but is less advantageous.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The manufacture of potash alum by mixing clay with an acid sulphate of
potash or sulphate of alumina and sulphate of potash, moulding this mixture into
blooks and exposing these blocks to a temperature of from about 275 to 300 degrees
centigrade substantially as hereinbefore described.
2. The manufacture of alumina by preparing blocks of clay and an acid sulphate
of potash or sulphate of ammonia and sulphate of potash and heating them to a
temperature of from about 275 to 300 degrees centigrade to obtain potash alum and
Bubsequently treating the said blocks with a lye in order to obtain alumina all sub-
stantially as hereinbaforo described.
Dated this 81st day of
1000
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.