IMPROVEMENTS IN THE MANUFACTURE OF ALUM AND CERTAIN ALUMINO-FERRIC COMPOUNDS
Year: 1877

page_text: LETTERS PATENT to Peter Spence, of Manchester, in the County of Lancaster,..
Manufacturing Chemist, and Francis Mudie Spence, of the same Place, Manu-
facturing Chemist, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE
OF ALUM AND CERTAIN ALUMINO-FERRIC COMPOUNDS."
Sealed the 29th December 1877, and dated the 4th July 1877.
PROVISIONAL SPECIFICATION left by the said Peter Spence and Francis
Mudie Spence at the Office of the Commissioners of Patents on the 4th July
1877.
PETER SPENCE, of Manchester, in the County of Lancaster, Manufacturing
Chemist, and FRANCIS MUDIE SPENCE, of the same Place, Manufacturing Chemist.
"IMPROVEMENTS IN THE MANUFACTURE OF ALUM AND CERTAIN ALUMINO-FERRIC
COMPOUNDS."
Our Invention consists in treating shale for the production of alum by adding
the requisite quantity of acid at once to a charge of the said shale, and subsequently
transferring it successively to other charges. Thus we use three vessels, to which
shale is supplied, and add to the first the whole quantity of acid to constitute an
equivalent for all the alumina and other bases than can be extracted from a full
charge. After this has been boiled for a sufficient time the solution is removed and
transferred to the second vessel containing shale, and, after digestion, to the third
vessel; and, after digestion therein, the liquor is run off for the manufacture of
alum.
The first vessel having been emptied is again filled, and the second of the series
has now a full charge of acid boiled upon the shale therein, the solution being then
transferred to the vessel from which the finished liquor has been run. After boiling
here it is transferred to the refilled vessel, which now becomes the third of the
series, and thus the process goes on, the pan which has been for digestion with the
fresh charge of acid being the one to be emptied and refilled. Thus the fresh acid
is digested upon the partially exhausted shale, and extracts as much as possible of
its alumina, while the partially saturated acid is digested upon the fresh shale, and
is thus all or nearly all taken up.

page_text: We have above spoken of the use of three vessels, but two may be employed; or,
if the solution is desired to be entirely neutral or "sweet," then, if it should prove
necessary, more than three may be used. In like manner we use the series of
digestions above described for the production of the ordinary and basic alumnino-
ferric compounds from bauxite or shale, or from both..
SPECIFICATION' in pursuance of the conditions of the Letters Patent filed by
the said Peter Spence and Francis Mudie Spence in the Great Seal Patent
Office on the 4th January 1878.
PETER SPENCE, of Manchester, in the County of Lancaster, Manufacturing
Chemist, and FRANCIS MUDIE SPENCE, of the same Place, Manufacturing Chemist.
IMPROVEMENTS IN THE MANUFACTURE OF ALUM AND CERTAIN ALUMINO-FERRIC
COMPOUNDS."
..
Our-Invention consists, firstly, in treating shale for the production of alum by
adding the requisite quantity of acid at once to a charge of the said shale, and
subsequently transferring it; as hereafter to be described, successively to other
charges, whereby we are enabled by such transferring process to digest the fresh
acid upon partially exhausted shale, while the partially saturated acid is digested
upon fresh shale, whereby all or nearly all-of-the acid-is taken up.
In describing a method of carrying out our said Invention I shall refer to certain
diagrams for clearness of explanation, and as a description of the process constituting
our Invention necessarily assumes certain operations to have taken place before the
improvement really commences, I shall, in the first place, point out certain
preparatory operations which lead to the real commencement of the working of our
Invention.
Referring, then, to the diagram A, a, b, c, represent three pans of any ordinary
construction for digesting shale with sulphuric acid, each of the said pans being
provided with equal charges of shale. Into the first pan a is introduced in, the
form of dilute acid (oil of vitriol) about equal weight to the shale therein, and the
contents are then digested with heat in the usual manner for the requisite time.
After this the liquor is transferred to the pan b, when digestion again takes place,
and then the liquor is transferred to the pan c for further digestion, after whicli it
is run off for the manufacture of alum.
The above operations are all preliminary in order to bring the contents of the
series of pans into condition for the operations of our Invention, and which now
commence; but it will be necessary, in the first place, to point out the effect of those
operations which have taken place.
The pan a having had the full charge of fresh acid added to it the shale therein
is nearly exhausted, the pan & less so, and the pan è still less; and this having been
accomplished, the spent or partially spent shale, after having been washed as usual,
is removed from the vessel a, and a fresh charge placed therein; and diagram B will
then represent the conditions, the number 15 being used to indicate the normal
strength of alumina in the shale, 5 of vessel b, the reduced strength thereof owing
to the acid having been digested thereon, as described in reference to A'; and 10;
the value of the alumina after it has been digested with the still more saturated
acid: These numbers, however, it must be understood; do not in any way represent

page_text: real proportions, they are perfectly arbitrary, and may be any others and in any
proportions, provided the same order of smaller and larger numbers are maintained,
they being simply used for facility of explanation.
The above being the conditions of the pans in diagram B, a charge of fresh acid
is added to the partly exhausted and weakest shale in the pan b, and digestion
having then taken place the liquor is transferred to pan c for further digestion, and
finally the liquor is transferred to the fresh charge of shale in pan a, and after
digestion is drawn off for the manufacture of alum. These operations having taken
place in the three pans, that shewn at b is now washed and emptied, and a fresh
charge of shale placed therein, the supposed value of the alumina in the pans a, c,
being now respectively 10, 5, and a fresh charge of acid is supplied to the pan c,
from whence it is transferred to the pan a, and subsequently to that shewn at b,
from whence the liquor is drawn off. The pan c is now washed and emptied, and a
fresh charge of schale placed therein, and the third series of operations to be described
by diagram D takes place, the numbers, as before, indicating the supposed value of
the alumina in each pan. The fresh acid is now supplied to the pan a, from whence
it is transferred to b, and subsequently to c, to be drawn therefrom, the necessary
digestion in all cases having taken place after each transference.
A set of changes
will now have taken place through the series of pans a, b, c, and a fresh charge of
shale having been supplied to the pan a the whole will be restored to the conditions
denoted at diagram B ready for a series of operations, the same as those above
described, and so on; and it will have been observed that the fresh charges of acid
are supplied to the most exhausted shale, while the most saturated acid is delivered
to the richest shale to be drawn off therefrom.
In the above description I have not referred to quantities of material as they may
be varied, but in practice we use a charge of fifteen tons of calcined shale, and
dilute sulphuric acid equal to fifteen tons of oil of vitriol; and we effect the
digestions by boiling in the usual manner for twenty-four hours.
I have above referred to a series of three digestions, but the same principle may
be carried out by employing two only; or, if desired, more than three inay be used.
Second. We employ the process substantially as described for the production of
alumino-ferric and basic aluininous compounds from bauxite containing a consider.
able amount of silica.
Having thus described and ascertained the nature of our said Invention and the
manner in which the same is to be performed, I desire it to be understood that we
claim as secured to us under the above in part recited Letters Patent and for the
purposes above set forth, the use of the series of digestions, substantially as
described, whereby the fresh acid is supplied to an exhausted or partially exhausted
charge of shale or bauxite, and the saturated or partially saturated acid is supplied
to a fresh charge of shale or bauxite.
In witness whereof, I, the said Francis Mudie Spence, have hereunto set my
hand and seal, this Third day of January, in the year of our Lord One
thousand eight hundred and seventy-eight.
F. M. SPENCE. (LS.)