IMPROVEMENTS IN THE TREATMENT OF ALUNITE OR OF NATURAL PRODUCTS CONTAINING THE SAME SO AS TO OBTAIN ALUMINOUS COMPOUNDS THEREFROM.
Year: 1875

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields,
"
in the County of Middlesex, Gentleman, for the Invention of
** IMPROVEMENTS IN THE TREATMENT OF ALUNITE OR OF NATURAL PRODUCTS
CONTAINING THE SAME SO AS TO OBTAIN ALUMINOUS COMPOUNDS THEREFROM.
-A communication from abroad by La Société Financière de
Paris. of Paris, in the Republic of France.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition,
on the 25th February 1875.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN THE TREATMENT OF ALUNITE OR OF
NATURAL PRODUCTS CONTAINING THE SAME SO AS TO OBTAIN ALUMINOUS COMPOUNDS
THEREFROM," a communication to me from abroad by La Société Financière
de Paris, of Paris, in the Republic of France, to be as follows:-
This Invention relates to, a process of treating alunite or natural
products containing the same in order to obtain therefrom alum or

page_text: "
aluminous compounds in larger quantities, and of greater purity than
are now obtained by the processes employed.
Alunite is as is well known the result of the action of the gaseous
vapours emanating from volcanoes in activity upon trachytes and lavas.
The alumina of these is thus transformed either wholly or partially into
sulphate of alumina, in the latter case sulphate and hydrate of alumina
are formed, but as lavas and volcanic rocks also contain considerable
quantities of potash this base becomes also converted into sulphate
which together with the sulphate of alumina yields alum.
It has been found that the action of a certain temperature causes this
mineral substance to undergo a modification, and that water is capable
of dissolving a portion of it.
Alunite being considered as composed of anhydrous alum and of
hydrate of alumina, it is evident that by eliminating the water by a
suitable process of calcination nothing should remain but anhydrous
alum and anhydrous alumina, and that it would suffice to treat the
product of the calcination with water in order to obtain the alum in
solution and the hydrate of alumina as an insoluble residuum; but it is
found in practice that by this operation a small portion only of the alum
originally present is obtained.
Hydrated alumina is insoluble in pure water, but it is perceptibly
soluble in a solution of alum, and alumina does not combine directly
with water, but it may be combined with it by entrainement, and this is
what actually takes place.
When dehydrated alunite is treated with water the alum in this
product is in the anhydrous condition, and in order to crystallize or
become dissolved it requires to take 24 equivalents of water, that is to
say, to be hydrated.
In order to separate the iron from alum a moderately concentrated
solution of alum is employed, say about one part of alum to 3 or 4 times
its weight of water, and the solution is maintained at a temperature near
the boiling point, to it a solution of hydrate of potash is poured, alumina
is precipitated which redissolves. This operation is continued until the
moment when the alumina commences to dissolve with difficulty, or
when some flakes remain permanent, the solution still maintaining an
acid reaction.
If alum containing iron be saturated with hydrate of potash or with
the calcined aluminous material, not only will neutrality be arrived at

page_text: but the solution of hydrate of alumina will be effected, and there will be
obtained a precipitate of basic alum and of hydrate of alumina containing
the oxide of iron, and alum almost free from iron in solution and
perfectly neutral will be obtained.
Now in order to obtain from the alunite or products containing the
same the whole of the alum it is capable of yielding, and to convert a
large portion of the anhydrous alumina which it contains into sulphate
of alumina, at the same time effecting the solution of as small a quantity
as possible of the iron contained in the alunite, a solution of alum or
of sulphuric acid or mixtures of the same is employed so as to effect
the solution of the alumina contained in the alunite.
In carrying out this Invention about 100 parts by weight of calcined
alunite (or alunite in powder) are treated with about 1,500 parts by
weight of water containing in solution 70 parts by weight of sulphuric
acid at 50 degrees centigrade, and after the whole has been maintained
during an hour at near the boiling temperature the liquid is clarified and
evaporated to crystallization. The residuum is still a product rich in
alumina, of which it contains about 35 per cent, but as it contains nearly
all the iron originally existing in the primary substance it will be under-
stood that by attacking it energetically with sulphuric acid a very
impure result would be obtained, but as the alumina is suceptible of being
acted on by alkaline solutions the best treatment is to submit it to such
provided that the iron be insoluble in alkaline solutions, by such a
process a very pure aluminate will then be obtained, which on being
treated with carbonic acid will furnish pure hydrate of alumina, from
which pure sulphate of alumina can be obtained.
The solution of sulphate of alumina obtained as before mentioned may
he converted into alum by the addition of sulphate of notash
0
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Henry Johnson in the Great Seal Patent
Office on the 2nd August 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman, send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fifth day of February, in the
year of our Lord One thousand eight hundred and seventy-five, in
the thirty-eighth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said John Henry Johnson, Her
special license that I, the said John Henry Johnson, my executors,
administrators, and assigns, or such others as I, the said John Henry
Johnson, my executors, administrators, or assigns, should at any
time 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 TREATMENT OF ALUNITE OR OF NATURAL
PRODUCTS CONTAINING THE SAME SO AS TO OBTAIN ALUMINOUS COMPOUNDS THERE-
FROM," a communication to me from abroad by La Société Financière
de Paris, of Paris, in the Republic of France, upon the condition
(amongst others) that I, the said John Henry Johnson, my executors
or administrators, by an instrument in writing under my hand and
seal, should particularly describe and ascertain the nature of the said
Invention, and in what manner the 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 I, the said John Henry Johnson, 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, that is to say:-
The said Invention relates to a novel process for treating alunite
rocks in order to obtain therefrom potassic alum in larger quantities
than has hitherto been obtained by the processes ordinarly employed,
and also of greater purity and without admixture of salts of iron.
The processes hitherto proposed or employed for the separation of the
alum are based upon the preliminary calcination of the alunite rocks and
the treatment of the calcined matter with water which only practically
permits of the extraction of a minute portion of the alum contained in
the alunite.
Alunite is the result of the action of the gaseous vapours emanating
from volcanoes in activity or regarded as extinct, upon trachytes and

page_text: lavas. The alumina of these rocks is thus converted either wholly or
partially into sulphate; in the latter case sulphate and hydrate of alumina.
are formed, but as lavas and volcanic rocks also contain considerable
quantities of potash this base becomes also converted into sulphate.
The sulphate of alumina in its anhydrous state combines with the
sulphate of potash and forms anhydrous alum which combines with
hydrate of alumina to form the mineral substance designated by the
name of alunite.
Alunite being considered as composed of anhydrous alum and of hydrate
of alumina is a compound not easily attacked by chemical agents.
It has been found that the action of a certain temperature causes this
mineral substance to undergo a modification, and that water is then
capable of dissolving a portion of it, and that the solution possesses
astringent properties.
Considering the composition of alunite it is evident that by eliminating
the water by a suitable process of calcination nothing will remain but
anhydrous alum and anhydrous alumina, and it would appear that it
would suffice to treat the product of the calcination with water in order
to obtain the alum in solution and the hydrate of alumina as an insoluble
residuum; but it is found in practice that by this operation only one-
third of the alum originally present is obtained.
If alunite deprived of its water of hydration by a well conducted
calcination be treated with water and the solution obtained be filtered,
the soluble portion of the alunite will be obtained. If the resulting
solution be then divided into two parts of equal volume or weight, and
one of these parts be submitted to evaporation so as to obtain the con-
centration required in order that the bodies in solution become
crystallized, there will be collected say about thirty-five per cent. of pure
and neutral alum, and a white deposit corresponding to about fifteen per
cent. of the material employed; this deposit will be found on examina-
tion to be composed of artificial alunite and hydrate of alumina.
Hydrated alumina is insoluble in pure water, but it has been found
that it is soluble in a solution of alum.
In the treatment of dehydrated alum with the water there is produced,
5 first, one-third of the alum; second, a precipate of basic alum. Taking
now the other half of the filtered liquid resulting from the washing of the

page_text: :
calcined alunite it will suffice to saturate it with sulphuric acid in order
to avoid the reformation of basic alum, and that alum and sulphate of
alumina shall be obtained by evaporation. By this treatment which
forms an essential feature of this Invention an increased yield of alum is
obtained, thus from about sixty-eight to seventy per cent of pure alum is
obtained instead of thirty-five per cent, whilst in the mother waters there
is found a quantity of sulphate of alumina sufficient to yield a further
fifteen per cent. of pure alum by the addition of sulphate of potashı.
If alum containing iron be treated with hydrate of potash or with the
calcined aluminous material, not only will neutrality be arrived at, but
in the latter case the solution of the hydrate of alumina will be effected.
No exchange of base will however have taken place between the salt of
iron and the hydrate of alumina. In order to effect this it will be
necessary to bring the whole to dryness and then to redissolve in water,
and it is when the modified hydrate of alumina is precipitated that the 1
exchange of bases takes place, and a precipitate of basic alum and of
hydrate of alumina containing the oxide of iron results, and a solution
of alum neutral and free from iron will be obtained.
Now according to this Invention in order to obtain from the alunite
the whole of the alum it is capable of yielding and to convert a large 2
portion of the anhydrous alumina which it contains into sulphate. of
alumina, whilst at the same time dissolving as small a portion as possible
of the iron contained in the alunite the dissolving action of alum and
dilute sulphuric acid upon hydrate of alumina is employed.
If one hundred parts by weight of calcined alunite or alunite in 2
powder be treated with about one thousand five hundred parts by weight
of water containing in solution, seventy parts by weight of sulphuric
acid at fifty degrees, and after the whole has been maintained for a
period of about one hour at a temperature approaching the boiling
point, the liquid is then clarified and evaporated in order to effect a
crystallization, there will be obtained,―
First. About ninety-five parts of alum perceptibly pure.
Second. About one hundred and nineteen parts of sulphate of alumina
with about 12.5 per cent. of alumina.
Third. About thirty-five per cent. of residuum containing nearly all a
the iron originally present in the alunite. The residuum is still a product
rich in alumina, of which it contains about thirty-five per cent., but as it

page_text: contains nearly all the iron originally existing in the primary substance
it will be understood that if it be operated upon with sulphuric acid
a very impure result will be obtained.
The resulting product may if desired be purified by the means herein-
before described, but it is preferred to subject it to the action of alkaline
solutions provided that the oxide of iron be in a state insoluble in alkaline
solutions. By this means a very pure aluminate will then be obtained,
which on being treated with carbonic acid with furnish pure hydrate of
alumina from which pure sulphate of alumina may be obtained.
Having now described and particularly ascertained the nature of the
said Invention, and the manner in which the same is or may be used or
carried into effect, I would observe in conclusion that what I consider
to be novel and original and therefore claim as the Invention _secured
to me by the herein-before in part recited Letters Patent is,-
First. The treatment of alunite so as to obtain alum therefrom by
firstly submitting the same to calcination and then to the action of
sulphuric acid, as herein-before described.
Second. Obtaining sulphate of alumina from alunite in the manner
herein-before described.
Third. Obtaining an increased proportion of alum from alunite by the
addition of sulphate of potash to the solution of sulphate of alumina, as
herein-before described.
Fourth. Obtaining pure alum or alum free from iron, from alunite, or
from impure alums, in the manner herein-before described.
In witness whereof, I, the said John Henry Johnson, have to this
my Specification set my hand and seal, the Thirty-first day of
J. HENRY JOHNSON. (L.S.)