IMPROVEMENTS IN THE MANUFACTURE OF ALUM AND OTHER ALUMINOUS COMPOUNDS
Year: 1868

page_text: LETTERS PATENT to Charles Denton Abel, of No. 20, Southampton
Buildings, Chancery Lane, in the County of Middlesex, Patent
Agent, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
ALUM AND OTHER ALUMINOUS COMPOUNDS." -A communication from
abroad by Henry Pemberton, of Allegheny City, Pennsylvania,
United States of America.
Sealed the 13th November 1868, and dated the 1st June 1868.
PROVISIONAL SPECIFICATION left by the said Charles Denton Abel
at the Office of the Commissioners of Patents, with his Petition,
on the 1st June 1868.
I, CHARLES DENTON ABEL, of No. 20, Southampton Buildings,
Chancery Lane, in the County of Middlesex, Patent Agent, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN THE MANU-
FACTURE OF ALUM AND OTHER ALUMINOUS COMPOUNDS," to be as follows:-
This Invention consists in a new and useful process for the manu-
facture of alum and other aluminous compounds which obviates some
serious difficulties incident to the method heretofore practised.
The ordinary process of making the sulphate or other salts of alumina

page_text: as heretofore in use is to add the hydrate of alumina to a boiling dilute
solution of sulphuric acid until a quantity of alumina dissolved in the
dilute acid is sufficient to form a neutral or slightly basic salt of alumina,
an excess of alumina being necessary to insure the perfect neutralization
of the acid. This process requires the mixture to be kept constantly
boiling for many consecutive hours or days. The solution thus formed
containing then from 20 to 30 per cent. of sulphate of alumina is allowed
to settle, the clear liquor is decanted from the sediment, and then
evaporated to the proper consistence in copper or leaden vessels from
which it is ladled out into moulds to cool.
This process is liable to the following serious objections:-1st, there is
great danger of forming the basic sulphate of alumina (A1203+SO3)
instead of the neutral sulphate (Al 203 +3803), the former being an
insoluble compound which is always formed in greater or less proportions
when dilute solutions of the neutral sulphate are boiled with an excess
of hydrate of alumina and the basic sulphate once formed is not
re-dissolved by dilute acid, but only by very hot concentrated acid;
2nd, the serious loss of both alumina and sulphuric acid by the formation
of the useless basic sulphate of alumina; 3rd, the neutral sulphate
of alumina formed by this old process is exceedingly dense and hard
so as to be with difficulty attacked and dissolved by water when sub-
sequently required for use; 4th, there is a great amount of fuel, time,
and labour expended in the boiling of the mixture of hydrate of alumina
and dilute acid, and also in the subsequent evaporation of the resulting
liquor to produce the solid neutral sulphato.
The present Invention consists in the following process:-Hydrate
of alumina (which is obtained from kryolite or other minerals by
the decomposition of the aluminate of soda by an acid) is mixed
with sulphuric acid and water in the requisite atomic proportions
necessary to form the neutral (or slightly basic) sulphate of alumina
(Al 203+3803+18 HO), taking care to employ a quantity of water
only enough or but little more than enough to afford the water of
crystallization required. The proportions found convenient for use are, say,
300 lbs. avoirdupoids of wet alumina containing 38 per cent. of hydrate,
and 400 lbs. of sulphuric acid of 58 degrees Beaumé. This will produce
from 650 to 680 lbs. of sulphate. A considerable portion of the water
escapes in the form of steam during the process. A powerful chemical
reaction then takes place attended by a great evolution of heat, and

page_text: the escape of carbonic acid resulting from the decomposition of traces
of carbonate of soda retained in chemical combination by the alumina
prepared as above stated from the aluminate of soda. As soon as this
chemical action ceases the mass, which at first is perfectly fluid and.
in a state of froth or foam, begins rapidly to harden, and in a few
minutes is converted into a white porous mass. This substance thus
procured is a neutral (or slightly basic) sulphate of alumina, and is
alnost instantly and (with the exception of traces of alumina in combin-
ation with silica, phosphoric acid, &c., amounting in all to less than one
per cent.) entirely soluble in water.
If in the process described the quantity of water present in the
hydrate of alumina and acid together is just sufficient to form the
compound above described, the mass will be dry enough to pack
as soon as it is cold, or it may if preferred be first ground to a fine
powder, and in that state be packed for sale and use. If, however,
there should have been a slight excess of water beyond what was
requisite for crystallization the mass on cooling will be found to be
slightly damp, and should be placed for a day or two in a warm room
which will dry out the excess of moisture.
It will be observed that this improved process entirely dispenses with
the employment of artificial heat for the boiling of the mixture or its
subsequent evaporation of the water. The sulphate of alumina thus
produced contains from 15 to 19 per cent. of alumina in the soluble'
state, and is applicable to all the purposes for which either ordinary
alum or the sulphate of alumina as commonly prepared are used.
When this process is carried on as above described with large
quantities of materials, say 500 lbs. or more at a single operation, the
chemical action is so violent that the heat evolved raises the temperature
of the mass much above the actual boiling point of the concentrated
solution produced. The consequence is that the mixture becomes so
exceedingly fluid, and the ebullition is protracted so long, as to drive
off all or nearly all of the gases resulting from the decomposition, and the
result is that the mass ou cooling and solidifying may not have the
porosity which it would otherwise possess when the process is practised
on a smaller scale. In order therefore to increase the porosity the
mixture may be stirred until it becomes cooler and begins to thicken,
when a small quantity of bicarbonate of soda in fine powder in the
proportion of about 1 lb. of the bicarbonate to 1,000 lbs. of the alum may

page_text: be sprinkled on the surface of the mass and rapidly stirred in so as to
become intimately mixed therewith. The decomposition of the soda
causes the formation of gas which penetrates the mass and renders it
sufficiently porous, so that when discharged into the proper vessels to
cool it is found when hardened to be vesicular, as above described. In
manufacturing ordinary alums (the double sulphates of alumina and
either potassa or ammonia) the improved process of preparing the
sulphate of alumina is practised as above described. The resulting
sulphate can then be dissolved in water, and its solution mixed with
that of the sulphate of potassa or ammonia in the usual manner.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Charles Denton Abel in the Great Seal Patent
Office on the 30th November 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
DENTON ABEL, of No. 20, Southampton Buildings, Chancery Lane, iu
the County of Middlesex, Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of June, in the year
of our Lord One thousand eight hundred and sixty sixty-eight, in the
thirty-first year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said Charles Denton Abel,
Her special licence that I, the said Charles Denton Abel, my exc-
cutors, administrators, and assigns, or such others as I, the said Charles
Denton Abel, my executors, administrators, and assigns, should at
any tinic agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVEMENTS IN THE MANUFACTURE OF ALUM AND OTHER ALUMINOUS
COMPOUNDS," a communication to me from abroad by Henry Pemberton,
of Allegheny City, Pennsylvania, United States of America, upon
the condition (amongst others) that I, the said Charles Denton Abel,
my executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe and
ascertain the nature of the said Invention, and in what manner the

page_text: same was to be performed, and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately
after the date of the said Letters Patent.
NOW KNOW YE, that the said Charles Denton Abel, do hereby
declare the nature of the said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained
in and by the following statement thereof, that is to say:-
This Invention consists in a new and useful process for the manu-
facture of alum and other aluminous compounds which obviates some
serious difficulties incident to the method heretofore practised.
The ordinary process of making the sulphate or other salts of alumina
as heretofore in use is to add the hydrate of alumina to a boiling dilute
solution of sulphuric acid until a quantity of alumina dissolved in the
dilute acid is sufficient to form a neutral or slightly basic salt of alumina,
an excess of alumina being necessary to insure the perfect neutralization of
the acid. This process requires the mixture to be kept constantly boiling
for many consecutive hours or days. The solution thus formed containing
then from 20 to 30 per cent. of sulphate of alumina is allowed to settle,
the clear liquor is decanted from the sediment, and then evaporated to the
proper consistence in copper or leaden vessels, from which it is ladled out
into moulds to cool.
This process is liable to the following serious objections:-1st, there is
great danger of forming the basic sulphate of alumina (Al 203+S03),
instead of the neutral sulphate (Al 203+3 SO 3), the former being an
insoluble compound which is always formed in greater or less proportions
when dilute solutions of the neutral sulphate are boiled with an excess
of hydrate of alumina, and the basic sulphate once formed is not
re-dissolved by dilute acid but only by very hot concentrated acid; 2nd,
the serious loss of both alumina and sulphuric acid by the formation of
the useless basic sulphate of alumina; 3rd, the neutral sulphate of
alumina formed by this old process is exceedingly dense and hard so as
to be with difficulty attacked and dissolved by water when subsequently
required for use; 4th, there is a great amount of fuel, time, and labour
expended in the boiling of the mixture of hydrate of alumina and dilute
acid, and also in the subsequent evaporation of the resulting liquor to
produce the solid neutral sulphate.
The present Invention consists in the following process: -Hydrate

page_text: of alumina (which is obtained from kryolite or other minerals by
the decomposition of the aluminate of soda by an acid) is mixed
with sulphuric acid and water in the requisite atomic proportions
necessary to form the neutral (or slightly basic) sulphate of alumina
(A1203+3 S03+18 HO), taking care to employ a quantity of water only
enough or but little more than enough to afford the water of crystallization
required. The proportions found convenient for use are, say, 300 lbs. avoir-
dupoids of wet alumina containing 38 per cent. of hydrate, and 400 lbs. of
sulphuric acid of 58 degrees Beaumé. This will produce from 650 to
680 lbs. of sulphate. A considerable portion of the water escapes in the
form of steam during the process, a powerful chemical reaction then
takes place attended by a great evolution of heat, and the escape of car-
bonic acid resulting from the decomposition of traces of carbonate of soda
retained in chemical combination by the alumina prepared as above stated
from the aluminate of soda. As soon as this chemical action ceases the
mass which at first is perfectly fluid and in a state of froth or foam begins
rapidly to harden, and in a few minutes is converted into a white
porous
mass. This substance thus procured is a neutral (or slightly basic)
sulphate of alumina, and is almost instantly and (with the exception
of traces of alumina in combination with silica, phosphoric acid, &c.,
amounting in all to less than one per cent.) entirely soluble in water.
If in the process described the quantity of water present in the hydrate
of alumina and acid together is just sufficient to form the compound
above described the mass will be dry enough to pack as soon as it is
cold, or it may if preferred be first ground to a fine powder and in that
state be packed for sale and use. If, however, there should have been
a slight excess of water beyond what was requisite for crystallization
the mass on cooling will be found to be slightly damp, and should be
placed for a day or two in a warm room which will dry out the excess
of moisture.
It will be observed that this improved process entirely dispenses
with the employment of artificial heat for the boiling of the mixture or
the subsequent evaporation of the water. The sulphate of alumina thus
produced contains from 15 to 19 per cent. of alumina in the soluble
state, and is applicable to all the purposes for which either ordinary
alum or the sulphate of alumina as commonly prepared are used.
When this process is carried on as above described with large
quantities of materials, say 500 lbs. or more at a single operation, the

page_text: chemical action is so violent that the heat evolved raises the temperature
of the mass much above the actual boiling point of the concentrated
solution produced. The consequence is that the mixture becomes so
exceedingly fluid, and the ebullition is protracted so long, as to drive off
all or nearly all of the gases resulting from the decomposition, and the
result is that the mass on cooling and solidifying may not have the
porosity which it would otherwise possess when the process is practised
on a smaller scale. In order therefore to increase the porosity the
mixture may be stirred until it becomes cooler and begins to thicken,
when a small quantity of bicarbonate of soda in fine powder in the
proportion of about 1lb. of the bicarbonate to 1,000 lbs. of the alum
may be sprinkled on the surface of the mass and rapidly stirred in
so as to become intimately mixed therewith. When cool the resulting
product is sulphate of alumina of visicular or porous structure, as
described before. The decomposition of the soda causes the formation
of gas which penetrates the mass and renders it sufficiently porous, so
that when discharged into the proper vessels to cool it is found when
hardened to be visicular as above described. In manufacturing ordinary
alums (the double sulphates of alumina and either potassa or ammonia)
the improved process of preparing the sulphate of alumina is practised as
above described. The resulting sulphate can then be dissolved in water,
and its solution mixed with that of the sulphate of potassa or ammonia
in the usual manner.
The advantages of this Invention over the processes heretofore known
and used are chiefly the following, viz. :—The procuring of the sulphate
in a form capable of dissolving rapidly and easily in water as compared
with the product of the old process, which owing to its greater solidity
and impermeability is only slowly soluble, the great reduction in cost
of manufacture by dispensing with the tedious and expensive operations
of boiling and evaporation of the solution, and the avoidance of the pro-
duction of the insoluble basic sulphate instead of the neutral sulphate of
alumina.
Having thus described the nature of this Invention, and in what
manner the same is to be performed, as communicated to me by my
foreign correspondent, what I claim is,―
First. The employment in the manufacture of the sulphate and other.
salts of alumina of the process herein-before described, either with or

page_text: without the use of bicarbonate of soda, substantially as and for the
purpose set forth.
Second. Producing sulphate and other salts of alumina in a porous
and soluble state, substantially as herein-before set forth.
In witness whereof, I, the said Charles Denton Abel, have here-
unto set my hand and seal, this Thirtieth day of November,
in the year of our Lord One thousand eight hundred and sixty-
eight
CHAS. D. ABEL. (L.S.)