Improvements in the Manufacture and Production of Salts or Compounds of Alumina or Aluminium.
Year: 1893

page_text: Date of Application, 7th Feb., 1893
Complete Specification Left, 26th Oct., 1893-Accepted, 2nd Dec., 1893
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture and Production of Salts or
Compounds of Alumina or Aluminium.
I, JACQUES LOUIS KESSLER of Clermont-Ferrand in the Republic of France,
Chemical Engineer, do hereby declare the nature of this invention to be as
follows:-
The iron contained in salts of alumina is productive of disadvantages which are
not satisfactorily remedied by the methods heretofore employed.
The following examples are given in order to explain the nature of my invention
but I do not limit myself as to the details.
According to my invention I add to the salts of alumina, soluble phosphoric
compounds such as phosphoric acid in any of its soluble and cheap forms. With
this object the solution of the salt of alumina (which must be acid) may be boiled
with phosphate of lime for example. The quantity of phosphate of lime is known
In place of
to be sufficient when the oxide of aluminium precipitated is white.
solid phosphate of lime dissolved phosphate of lime may be employed or bi-
phosphate or phosphate of alumina (natural or artificial) and if the effect of the
sulphate of lime formed by the reaction is objectionable phosphate of soda and a
small quantity of phosphoric acid may be added, these latter may be added in the
final product only. For sizing paper the sulphate of alumina thus treated yields
products which are as white as those which are free from iron.
In order to obviate the disadvantages resulting from the presence of iron in the
salts of alumina employed in certain manufactures the iron may be eliminated or
removed by facilitating the crystallization of soda alum as hereinafter explained.
The preparation of this salt when conducted according to the methods heretofore
employed cannot be performed in summer or in warm climates, it does not produce
crystals by simple cooling and the product cannot be crystallized in order to
deprive it of iron except by converting it again into a paste which requires to be
stirred and turned over for several days in succession and must be treated in a
centrifugal machine (Augè's process described in the Specification annexed to his
French Patent No. 201440) or requires to be crystrallized in a vacuum (Laur's
Patent).
On carefully examining this salt I have now ascertained the causes of these
disadvantages and have succeeded in removing them.
When a solution of soda alum is too highly concentrated that is to say when its
density at the temperature of 45 degrees centigrade is more than 40 degrees
Baumé the alum is precipitated therefrom in the dehydrated form being opaque
and opalescent during the cooling, the transparent crystals of soda alum become
dehydrated spontaneously and change into an opaque paste. At lower degrees of
density and especially when the solution of soda alum has been primed with
crystals of soda alum at a temperature of 45 degrees centigrade it yields trans-
parent crystals of true or pure alum on cooling. A solution of soda alum saturated
with this salt at 45 degrees centigrade may be further heated and caused to boil
without preventing it from yielding good crystals on cooling provided that the loss
of water by evaporation is made good. On the other hand it produces an opaque
pasty salt when more highly concentrated and notwithstanding that the solution
was clear or limpid when boiling but when water or a solution of soda alum at a
degree of saturation below 40 degrees Baumé is poured over the pasty salt it
ohanges into transparent crystals. The conversion of the paste into crystals is
effected by the agency of the water and air and of the mother water which drains
from this paste enriched with water by the separation of the crystals.

page_text: By proceeding in accordance with these data it is possible to obtain very rapidly
and at all seasons of the year good crystals of soda alum which are permanent and
begin to form even at 50 degrees centigrade in the body of the liquid of the proper
density.
The following are given merely as examples of the processes employed in carrying
out this part of my invention.
The first method of operating consist in mixing directly with a soda alum paste
such as that obtained according to the Angé process hereinbefore referred to an
approximately equal or greater quantity of the drainage water of a salt resulting
from a previous operation to which crystals have been added in order to prime it,
the conversion proceeds very rapidly and the crystals increase in size the iron
remaining in the mother water.
A second method consists in pouring into a concentrated solution of sulphate of
alumina at say about 52 degrees density when boiling, being cooled if necessary
until it is about to stiffen (about 90 degrees) a sufficient quantity of cold mother
water from a preceding cystallization of soda alum to lower its temperature to
about 40 degrees centigrade and cause its richness in salt or degree of density to
stand at about 40 degrees Baumé. Crystals of sulphate of soda in the proportion
of about 40 per cent. of the weight of the sulphate of alumina and 52 degrees Baumé
are then dissolved therein. Under these conditions crystallization takes place and
an abundant yield of transparent salt is obtained on cooling the iron being left in
the mother water. The crystals are washed in the usual way. If it be desired to
obtain a salt still more free from iron they are redissolved without exceeding a
temperature of from 45 to 55 degrees centigrade and the solution standing above
the crystals is cooled. This solution produces salts cf great purity. Salts of still
greater purity may be obtained therefrom by again treating these salts in like
manner.
A third method consists in pouring a more concentrated and highly heated or
even boiling solution into a vessel in which there has been already obtained by a
previous crystallization of soda alum a proportion such that the temperature of the
mixture with the mother water standing above the crystals does not exceed from
about 45 to 55 degrees centigrade and the degree of density at these temperatures
does not exceed from about 35 to 40 degrees Baumé.
A fourth method consists in evaporating the liquid in the same vessel in which it
is crystallized either continuously or intermittently. This is readily done by
heating the liquid on the surface only by means of a coil filled with steam or hot
water suspended in the upper part of the vessel slightly below the level of the
liquid or by means of hot air such as the air from a stove in such a manner that the
temperature of the crystals does not exceed that at which they are changed into
paste (from about 40 to 50 degrees centigrade).
A fifth method consists in pouring into the said liquid (pure water or alum
solution) in a cold condition and alternately so that the temperature does not
exceed that herein before referred to at which the pasty salt is formed, first a
concentrated solution of sulphate of alumina and then a saturated solution of
sulphate of soda or crystals of this salt in such a manner that the proportions of
these two salts cause the soda alum alone to crystallize.
Another improvement consists in preparing hydrochlorate of alumina and causing
it to crystallize in order to separate the iron which is more easily done that when
dealing with sulphate of alumina when it is combined with an alkaline chloride.
With this object in place of employing sulphate of soda for mixing with the
sulphate of alumina sea salt or a chloride of potassium or of ammonium is employed.
Soda alum, potash alum or ammonia alum are thereby caused to crystallize in the
first place and there remains in the mother water along with the iron double
chlorides of aluminium and sodium potassium or ammonium which are very
economically obtained. They are separated from the iron by known means and
employed for other salts of alumina (successive crystallization and separation &c.)
or the iron may be neutralized by means of phosphoric acid as explained under the

page_text: first improvement or both operations may be performed. Chloride of ammonium is
less advantageous for the preparation of the ammoniacal double chloride owing to
the relatively high price of ammonia and salammoniac. When sea salt is employed
it may be used in excess. It renders the soda alum more susceptible of dehydration
and may lower the point at which this dehydration takes place to below 30 degrees.
Baumé but as at the same time it renders the double sulphate less soluble when
cold this disadvantage is counterbalanced and the yield of crystals is increased
rather than diminished.
By these means I obtain chlorides of aluminium free from iron and containing a
certain proportion of alkaline chlorides and sulphates.
Dated this 7th day of February 1893.
COMPLETE SPECIFICATION.
Improvements in the Manufacture and Production of Salts or
Compounds of Alumina or Aluminium.
I JACQUES LOUIS KESSLER of Clermont-Ferrand in the Republic of France,
Chemical Engineer 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 iron contained in salts of alumina is productive of disadvantages which are
not satisfactorily remedied by the methods of treatment heretofore employed.
It has been successfully eliminated from the sulphate of alumina by causing it to
combine with sulphate of potash or sulphate of ammonia but these two salts being
useless for the ulterior purposes for which the product is destined cause this method
of purifying to be attended with considerable expense. The processes employed
with a view to replacing them by the much cheaper sulphate of soda again cause
a loss owing to the increased cost of manufacture which absorbs a great part of the
saving effected by this exchange.
The only commercially successful process which has been employed for obtaining
soda alum namely Auge's process described in his French Patent No. 201,440 does
not enable this salt to be produced in a crystalline form except by converting it by
cooling it from a concentrated solution into a cheesy magma which is exposed to
the air being spread upon tables where it requires to be frequently turned over
for several days until it is converted into crystals which are dried in a centrifugal
machine. Even then it is necessary in the first place (in order to provide against
an imperfect removal of the iron contained in the small quantity of liquid which is
separated) to previously eliminate the greater part of the iron from the crude
materials by long and expensive treatment.
After a long investigation of the nature and properties of soda alum I have drawn
the following conclusions which form the basis of the improved processes for the
elimination of iron from sulphate of alumina by causing the latter to crystallise in
combination with sulphate of soda (soda alum).
It is known that the difficulty encountered in effecting this crystallization results
from the formation of a white opaque magma which is produced when a sufficiently
concentrated solution of soda alum is allowed to cool in order to separate the salt
at a low temperature. This magma simply consists of soda alum in combination
with less water than when it takes the form of transparent crystals. Although
apparently amorphous it is composed in fact of minute or microscopic particles with
a bacreous reflection. Under about 25 degrees centigrade it is transformed into
transparent crystals and this transformation takes place more rapidly in proportion
as it is brought into more intimate contact with transparent crystals previously
formed. Above this temperature and in proportion as the temperature rises it tends
on the contrary to form more and more and when transparent crystals are present in

page_text: the surrounding liquid to increase whilst the said crystals dissolve so that it may be
said that according to circumstances and at temperatures comprised between 28
and 35 degrees centigrade one salt when in excess consumes the other.
With regard to the transparent crystals they may be formed at temperatures of
from about fifty degrees centigrade to 25 or 28 degrees when the liquid is not
primed with particles of this destructive magma.
Below this temperature a solution of alum yields transparent crystals only as the
magma itself disappears in producing them.
These investigations have led me to make the discovery that in the Augé
process the transformation of the magma into crystals results from the fact that by
the evaporation of the mother water leaving the magma and the cold resulting
therefrom transparent crystals are formed at the surface which become gradually
incorporated therewith and increase in size therein as they consume it.
This enabled me to save a considerable amount of labour and of room occupied
by incorporating crystals ready formed with the magma beforehand thus enabling.
it to be left to transform itself entirely into crystals without either touching or
turning it over. A solution of soda alum has a strong tendency to remain in a
condition of supersaturation with this salt so long as it is not in contact with ready
formed crystals. In fact a supersaturated solution at 60 degrees centigrade which
in presence of crystals or magma could not evaporate without producing a deposit
increasing in abundance to such a degree as even to prevent ebullition, can when
very pure and not contaminated with magma be evaporated even beyond the degree
of losing all the water of crystallization necessary for forming transparent crystals
with or without ebullition without producing any deposit and without losing its
transparency. At from fifty to thirty degrees centigrade a supersaturated solution
of this description at 40 degrees Baumé is capable of yielding as required either
transparent salt or magma according as the salt added to it is in the former or latter
condition or a mixture of the two when a portion of the two kinds is introduced.
But when once contaminated with a small quantity of magma it is no longer
possible to raise its temperature to near 30 degrees without causing it to separate
from this excess of salt in this form.
The act of dissolving the crystals of soda alum produces cold to the point that
a large proportion of boiling solution of the same salt may be incorporated with it
without transforming them into magma by the heat. Inversely the magma produces
heat in crystallizing.
In the technical applications of the invention as hereinafter set forth these
discoveries are utilised to facilitate the operations of manufacture as hereinafter
described under the letters a b c d e f g h i j k l m.
a. In place of exposing the magma to the air and stirring it frequently upon
tables as in the Augé process I mix it before-hand with a certain quantity of
crystals and leave it to itself to become transformed in a chamber or box with an
inclined bottom without stirring it, the more crystals are added the quicker the
transformation is accomplised. The mother water is conducted by the inclination
of the bottom to a receptacle from which it is withdrawn.
The addition of crystals may be dispensed with or when they are added the
transformation may be caused to take place more rapidly by leaving less water in
the magma by evaporating the solution of alum for example until it attains a
temperature of from 107 to 110 degrees centigrade.
When the salt is sufficiently pure it may be concentrated sufficiently to transform
it into dry crystals being immediately poured into the barrels for transport.
When the first layer has cooled in these receptacles a layer of crystals may be
spread upon it over which another layer of the salt is poured in, these operations
being repeated until the receptacle is filled. When in this compact form the salt
is less subject to efflorescence. Its manufacture in this form which constitutes one
of the features of this invention may also be effected by the means hereinafter
described under j.
ib. I succeed. in passing the zone of temperature situated above 30 degrees

page_text: entigrade at which the magma is produced by forming the soda alum at a low
emperature by alternate additions of each of its two components namely sulphate
f alumina and sulphate of soda in the proportions in which they are contained
n alum.
As it is easy in this operation to avoid any priming with magma the temperature
t which it tends to be produced may even be exceeded without any magma being
formed. For example, into a boiling solution of sulphate of alumina at 52 degrees
Baumé cooled if necessary until it ready to set (near 90 degrees centigrade) may
be poured a sufficient quantity of cold mother water resulting from a preceding
operation or a sufficient quantity of cold saturated solution of soda alum to lower
ts temperature to 40 degrees centigrade and its richness in salt or density to
10 degrees Baumé measured at this temperature afterwards spreading over it
crystals of sulphate of soda in sufficient quantity to form soda alum (about
10 per cent. of the weight of sulphate of alumina at 52 degrees Baumé). The
solution of the sulphate producing cold the dangerous point is passed and after
complete cooling a large quantity of alum in transparent crystals is withdrawn.
The mother water is employed in a subsequent similar operation until it becomes
too rich in iron.
c. The zone of dangerous temperature may be passed in another way without the
production of magma by evaporating the solution of alum to about 34 or 35 degrees
Baume (even causing it to boil) so that it is rendered uncontaminated with magma
as far as possible and with this object it is desirable to cover it, then when the
temperature has fallen to from forty to sixty degrees centigrade pouring it slowly
into a vessel containing a considerable quantity of transparent crystals of alum
and stirring and mixing the two somewhat quickly so that it is cooled with sufficient
rapidity below the dangerous temperature.
When the agitation producing the mixture is rapid the boiling solution may be
poured upon the crystals. The boiling solution may also be allowed to partly
cool in an intermediate vessel before mixing it with the crystals.
A more concentrated solution at 45 degrees Baumé for example in a boiling
condition may be poured upon the crystals on the condition that the surfaces of
contact are so rapidly renewed that all parts of the mixture remain below the
dangerous temperature.
It is then advantageous to place the crystals in a kneading or mixing apparatus
cooled externally with water such as the apparatus employed in the saccharification
of grain by malt and which must be lined with copper or lead or lead plated with
antimony.
When the temperature has reached a minimum the mass is partially withdrawn
and the operation is recommenced with the remainder. The operation may be
easily rendered continuous by causing the mixture to run off through an overflow
opening or otherwise. In order to economise cold water an apparatus such as is
employed for boiling granular sugar in a vacuum provided with an internal agitator
may be used for the mixing operation. The cold produced by the evaporation
obviates an excess of heat. It may be employed at the same time for crystallisation
and concentration at low temperature.
d. I have succeeded in rapidly evaporating the solution of alum exposed to the
air in the same vessel in which it parts with its crystals.
This is easily accomplished by heating the liquid at the surface only by the aid
of a coil of lead pipe immersed at the under part but sufficiently elevated above
O the bottom of the vessel which is likewise of lead. A hot fluid is caused to
circulate in the coil and the action (being intermittent if preferred) must be so
regulated that the temperature which may be as high as from about 50 to 60 degrees
centigrade or upwards at the surface of the bath does not at the bottom of the
liquid where the crystals are deposited, attain the dangerous temperatures of
from 24 to 25 degrees centigrade and upwards. The surface may be heated by
other known means such as stoves or natural or artificial draughts of air under a
cover or by means of any other suitable apparatus.

page_text: e. I also employ according to circumstances other known means for evaporating
liquids at low temperature in order to pass the limit of dangerous temperature
without producing any magma.
For example I project or spray the hot and concentrated solution of alum in the
air by the aid of jets or nozzles such as are employed for sulphurising vine plants
for example and allow it to fall in a cold condition into a lead tank arranged under-
neath and the bottom of which may or may not be covered with cold mother water.
The salt is deposited therein in the form of a powder composed of transparent
crystals or it remains dissolved until it crystallizes. The solution may be hotter in
proportion as the atmosphere is colder and the fall longer and vice versa.
The
solution may be heated to boiling.
In some cases I inject a current of cold air into a solution of alum maintained
at a temperature below 25 or 28 degrees centigrade or a current of hot air may
be injected into a cold solution so that it evaporates without rising above this
degree of temperature.
9. Again I may spray the liquid by means of a horizontal agitator which projects
it in a tangential direction into a passage traversed by a current of air (the said air
being cold in case the liquid is heated or hot in case the liquid is cold) the
temperature being always maintained below from 25 to 30 degrees centigrade.
These methods of operating described under def and g enable the work to be
carried on in summer it not having heretofore been possible to perform the
operations sufficiently quickly to enable this to be done.
h. (Purification). The crystals obtained by these methods of, operating are
impure and charged with iron when the solution is in the crude condition or is
formed with mother water. When allowed to drain they still remain wet and
contaminated with this impurity. Washing dissolves too much of the salt. The
cleansing is effected according to my invention by the employment of continuous
washing by processes of displacement or clarification such as were formerly
employed in the manufacture of sugar and are now employed in the lixiviation of
crude soda beet husks or refuse and the like.
The salt is placed in a vessel with a double bottom and sprinkled with clean
water or water saturated with purified salt or, at the commencement, with water
drained from a vessel previously employed for a similar operation, the water taken
being that which runs off at the end of the operation.
By arranging the displacing vessels in a series or cycle the operation may be
carried on in a continuous manner. Each vessel is emptied when the liquid running
off is found to be sufficiently free from iron.
It is evident that in order to obtain purer salts the purified salt must be
redissolved and again subjected to the same treatment. The methods of treatment
hereinbefore described under a and d are well suited for this second treatment.
i. (Acting on the aluminous matter). 1 effect a considerable saving by acting
on the aluminous matter with bisulphate of soda and an excess of sulphuric acid.
The facility with which I expel the iron admits of this substitution notwithstanding
the excess of iron which it causes in the products.
There is nothing peculiar in the operation. The bisulphate may be dissolved in
the acid or in a portion of the acid or in pure water according as may be found
most convenient. The proportions of acid, of bisulphate and of crude aluminous
material to be mixed together must be so regulated as to enable the latter to
thoroughly saturate all the free acid and that the total proportion of acid (free or
in combination) is four times the quantity capable of neutralising the soda in the
bisulphate employed.
The method of acting on the aluminous matter especially bauxite with sulphuric
acid concentrated to about 50 or 60 degrees Baumé constitutes an important part
of my invention the mixture being run off when the action is fairly commenced
either into a hole or into moulds capable of being taken to pieces like the moulds
in which potash alum is crystallised in which the action continues and is completed
at about 140 or 160 degrees centigrade. The mass is dissolved and the solution is

page_text: treated by known meaus and afterwards by those hereinbefore described in order
to purify it.
When the soda alum has been purified and obtained as herein before described
it can be placed on the market in a more dehydrated or more compact form than
usual by treating it as next hereinafter described. With this object I evaporate
its solution thoroughly deprived of opaque salt in a leaden vessel in which it is
heated to boiling by a coil made of thick lead and traversed by steam under
pressure. It may thus continue to boil and remain transparent whilst the
temperature rises to 115 degrees centigrade and upwards. If run out at this
temperature it yields a translucid porcelain like salt containing 13% of alumina
and upwards and not subject to efflorescence.
An analogous salt can be obtained by expressing the salt in the magma and
principally that which is deposited hot in the granular state in a solution into which
a small quantity acting as priming has been introduced. It is very easily expressed,
the drying may be completed in a stove.
k. A salt may be obtained in the form of blocks and more or less dehydrated by
melting or dissolving it in its water of crystallization or by heating the crystals in
order to agglomerate them by adhesion and compression. Under a I have described
another manner of obtaining soda alumn in transparent or translucid blocks.
1. I reserve the preparation and sale of a salt enriched with aluminium by yet
another means. In order to prepare this salt I cool to under 10 degrees centigrade
the solution of soda alum sufficiently diluted with water to allow the sulphate of
alumina in its composition to remain dissolved whilst the sulphate of soda separates
in the form of crystals which are removed..
The salt rich in sulphate of alumina being drained is evaporated in the manner
and in the forms customary for sulphate of alumina. The sulphate of alumina may
be prevented from crystallizing and even from remaining combined with the
sulphate of soda by rendering it basic by the addition of alumina.
When once the sulphate of soda has been eliminated by congelation the alumina
in excess may be recovered by diluting the salt with water and using the alumina for
the saturation of another portion of alum.
Sulphate of alumina containing less sulphate of soda may be obtained by these
means. It is evaporated and poured off in the usual manner. The sulphate of soda
is employed for making another quantity of alum.
I prepare the sulphate of alumina or soda alum in the form of a more or less dry
powder by pulverizing or spraying them exposed to the air by known means for
example by the aid of a current of superheated gas or air discharged horizontally
from a nozzle so as to act upon a stream of hot liquid falling vertically or at right
angles to the jet or stream of hot air or gas which blows away or scatters the liquid
in the form of spray forming the salt in the condition of powder.
m. Salts of alumina in general however little iron they may contain are
liable to turn brown at the surface owing to the salt of iron drying at this part.
This disadvantage may be remedied by adding an excess of sulphuric acid. Such
excess is however objectionable in certain cases. I obviate both these disadvantages
by adding to the salts a very small quantity from 1 to 5 per cent. for example of
free or combined phosphoric acid in a soluble form. With this object it is sufficient
to boil the solution of the salt of alumina with mono bi or tri basic phosphate of
lime or with phosphate of alumina or wavellite or any other soluble phosphate or to
add phosphate of lime. Sulphate of alumina and the soda alum manufactured with
natural phosphate of alumina and still containing phosphoric acid forms a novel
product obtained or manufactured according to my invention.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The improvements in the manufacture of salts or compounds of alumina or
aluminium consisting in regulating and proportioning the degrees of temperature

page_text: and density of the materials employed in the said manufacture and allowing them
to react upon one another in the manner and for the purpose substantially as
herein before set forth.
2. In the manufacture of the salts or compounds referred to in the preceding
claiming clause the several methods of conducting the process of manufacture in
practice and purifying the product substantially as hereinbefore described under the
a b c d e f g h i j k l & m.
3. As new articles of manufacture salts or compounds of alumina or aluminium
obtained by the improved methods of treatment substantially as hereinbefore
described.
T
T
1000
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.