Improvements in the Manufacture of Soda Alum.
Year: 1889

page_text: Date of Application, 27th July, 1889
Complete Specification Left, 24th May, 1890-Accepted, 28th June, 1890
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Soda Alum.
I, EUGÈNE AUGE of Montpellier in the Republic of France Chemist do hereby
declare the nature of this Invention to be as follows:-
When a solution containing sulphate of alumina and sulphate of soda in suitable
proportions for forming alum is heated to ebullition it loses the property of crystal-
lizing. To overcome this difficulty the evaporation has been conducted in vacuo at
temperatures not exceeding 60 degrees Centigrade. This method of proceeding is
correct in theory but in order to obtain a good result in practice there are certain
other essential conditions to be complied with. Not only must the temperature bo
kept below the boiling point but it is also most important not to exceed a certain
degree of concentration of the solution which for a temperature of 50 degrees Centi-
When this degree.
grade for example must correspond with a density of about 1.35.
of concentration is exceeded little or no alum is obtained and the solution assumes:
the appearance of a white paste which crystallises slightly or not at all. The.
improved process of manufacture forming the object of my present Invention.is
based on the discovery and application of this property and enables the manufacture
to be carried on in a far more practical and advantageous manner than by the processes.
heretofore employed.
It
In carrying out my Invention in practice I employ a lead lined vessel provided
with a steam coil or worm likewise made of or protected by lead and in this vessel'
I place a solution of sulphate of alumina as free as possible from iron which I heat to
and maintain at a temperature of between about 50 and 60 degrees Centigrade. This
solution of sulphate of alumina must be of a density of from about 1.30 to 1.31.
(or from about 33 to 34 degrees Bauiné). In this condition and at the temperature
above mentioned it contains about 675 grammes of sulphate of alumina per litre.
is possible but is less economical to employ sulphate of alumina in a solid state and
dissolve it in the water so as to obtain a solution of from about 33 to 34 degrees
Baumé at a temperature of 50 degrees Centigrade. To the solution of sulphate of
alumina add a corresponding quantity of anhydrous sulphate of soda in sinall
fragments or pieces and as pure as possible being in the proportion of about
146 grammes per litre of solution. This sulphate of soda is placed in a box perforated
with a number of small holes. This box is dipped or immersed in the solution.
When all the.
of sulphate of alumina until the contents are completely dissolved.
sulphate of soda is dissolved the density of the solution at the temperature of from,
about 50 to 60 degrees Centigrade attains a degree of concentration equal to from.
about 37 to 37.50 Baumé or a density of about 15. If the density is less it must
be brought up to these limits by adding in suitable proportions solid anhydrous.
sulphate of soda and sulphate of alumina and if the density be too great water must.
be added.
When the required density is obtained at the temperature of from about 50 to 60
degrees Centigrade the solution is poured into the crystallizing vessels in which the
crystals form in cooling in a few days. These crystals are washed preferably in a
centrifugal apparatus and packed without delay.
The mother liquor whose density at atmospheric temperature is from about 1-28
to 1.33 (or 32 to 36 Baumé) when cooled or used with a fresh quantity of sulphate
of alumina in the form of a concentrated solution and a fresh quantity of anhydrous
sulphate of soda in fragments so as to bring up the density to the required limits.
The solution thus obtained is poured into the crystallizing vessels as before and
the mother liquor reutilized as herein before described.
In hot and dry countries the evaporating operations may be performed by exposing.
the solution at a density of 1.35 in large shallow basins in the open air or the operation

page_text: may be conducted at ordinary temperature by bringing the solution of the two sulphates
in suitable proportions to a density of from about 38 to 38.5 Baumé (or say about 1.36
to 1365) by adding the two sulphates until the required density is attained as
herein before described.
1-1
21-301-
+
i 1000
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, Agents.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, Agents.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Soda Alum.
I, EUGENE AUGÉ of Montpellier 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:―
The processes heretofore patented or published make known the fact that when a
solution of sulphate of alumina and of sulphate of soda in suitable proportions for
forming alum has been heated to ebullition it loses the property of crystallising. In
consequence these processes relate mainly to the employment of evaporation in vacuo
with directions to not exceed a temperature of 60 degrees Centigrade.
The fact made known is correct but it represents part only of the necessary
conditions. Not only must the temperature be kept below the boiling point but also
and above all a certain degree of concentration of the solution corresponding at a tem-
perature of 50 degrees Centigrade, with a density of 1.35 must not be exceeded. This limit
of 1.35 if not absolute is at least very approximate. When this degree of concen-
tration is exceeded little or no alum is obtained and the solution assumes the
appearance of a white paste which crystallises slightly or not at all. The improved
process of manufacture forming the object of my present Invention is based on my
discovery and application of this fact and enables the manufacture to be carried on in
a far more practical and advantageous manner than by any of the processes heretofore
suggested or employed.
In carrying out my Invention in practice I employ a lead lined vessel provided
with a steam coil or worm likewise made of or protected by lead and in this vessel I
place a solution of sulphate of alumina, as free as possible from iron, which I heat to
and maintain at a temperature of between 50 and 60 degrees Centigrade. This solution
of sulphate of alumina must be of a density of from 1:30 to 1.31 (or from 33 to 34
degrees Baumé). In this condition and at the temperature above mentioned it contains
about 675 grammes of sulphate of alumina per litre. It is possible, but is less
economical to employ sulphate of alumina in a solid state and dissolve it in the water
so as to obtain a solution of from 33 to 34 degrees Baumé at a temperature of 50 degrees
Centigrade. To this solution of sulphate of alumina I add a corresponding quantity
of anhydrous sulphate of soda in small fragments or pieces and as pure as possible
being in the proportion of about 146 grammes per litre of solution. This sulphate
of soda is enclosed in a box or case perforated with a number of small holes which
is dipped or immersed in the solution of sulphate of alumina until the contents are
completely dissolved. When all the sulphate of soda is dissolved the density of the
solution always at the temperature of from 5 to 60 degrees Centigrade attains a
degree of concentration of from 37 to 37-50 Baumé or a density of about 1.35. It
is of the greatest importance to attain and not to exceed this density if the density is
perceptibly less the production of alum crystals would be proportionately diminished;
on the other hand if this density be perceptibly exceeded the white paste herein before
referred to would be produced and little or no crystallised alum would be obtained.
If the density is less than 135 a mixture containing in suitable proportions anhydrous
sulphate of soda and sulphate of alumina both in the solid condition must be added
to the solution. If on the other hand the density exceeds 1.35 water must be added
so as to restore this degree of density.

page_text: It must he observed however that in case this degree of density is exceeded to any
great extent the operation is irredeemably ruined the white paste being formed even
when water has been added.
When this required density of 1.35 is properly obtained always at the temperature
of from 50 to 60 degrees Centigrade the solution is poured into the crystallising
vessels in which the crystals form on cooling at the end of a few days. These
crystals are washed preferably in a centrifugal apparatus and packed immediately.
The mother liquor whose density when cooled is between 1.28 to 1-33 (or 32
to 36 degrees Baumé) according to the atmospheric temperature receive the addition
of a fresh quantity of sulphate of alumina in the form of a concentrated solution and
a fresh quantity of anhydrous sulphate of soda in fragments so as to bring up the
density to 135 after their total volume, which must be made the same as in the initial
operation, has been brought up to a temperature of from 50 to 60 degrees Contigrade.
The solution thus obtained is poured into the crystallising vessels as before the
crystals are collected and the mother liquor reutilised as herein before described.
In hot and dry climates the solution at a density of 1.35 may in summer time be
exposed in large flat or shallow basins so as to obtain the alum by spontaneous
evaporation in the open air. The operation may also be conducted at ordinary tem-
perature, for this purpose it suffices to raise the density of the solution of the two
sulphates in suitable proportions to from 38 to 38-5 degrees Baumé (or from 1.36
to 1365 degrees of density) by proceeding as herein before indicated that is to say
by adding to the solution the two sulphates in the solid state in sufficient quantity to
obtain the density of from 136 to 1-365.
Having now particularly described and ascertained the nature of my said Invon-
tion and in what manner the same is to be performed I declare that what I
claim is:-
The process of manufacturing crystallised soda alum as hereinbefore described and
in particular by regulating the temperature and density of the materials as hereinbefore
directed.
Dated this 24th day of May 1890
J. H. JOHNSON & Co.,
Agents.