Improvements in the Manufacture of Alum.
Year: 1890

page_text: Date of Application, 10th Jan., 1890
Complete Specification Left, 10th Oct., 1890-Accepted, 6th Dec., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Alum.
We, FRANCIS MUDIE SPENCE and DAVID DICK SPENCE, both of the Manchester
Alum Works, Manchester, in the County of Lancaster, Manufacturing Chemists, and
ALEXANDER ESILMAN, of the same place, Analytical Chemist in the employ of the
said Francis Mudie Spence and David Dick Spence, do hereby declare the nature
of this invention to be as follows :-
There are serious practical difficulties in the production of soda-alum which are
well known to manufacturers of aluminous compounds.
A boiling solution of potash-alum or ammonia-alum of about 1-3 specific gravity
gives on cooling a large crop of bold, well-defined crystals, but a boiling solution of
soda-alum of the same strength yields on cooling practically no crystals, and a solution
of it of much higher density instead of giving on cooling a crop of crystals from
which the "mother liquor" containing the impurities originally present in the hot
strong solution may readily be separated is transformed on cooling into a white,
viscid, cheesy and apparently homogeneous magna.
According to our present invention we take a hot strong solution of soda alum
prepared from sulphate of soda and sulphate of alumina or from sulphate of soda and
alumino ferric. A strength of solution of about 1-45 specific gravity at the boiling
temperature answers very well for the purpose of our invention.
This solution we stir and cool or allow to cool sufficiently to transform it into the
cheesy magna. This stirring is not essential to our process but as it exposes the
solution more, it cools it more quickly and thus hastens the formation of the cheesy
magma.
Now if this cheesy magma (produced from a solution of the strength named, that is
to say 145 specific gravity, or thereabouts) were left to itself it would, even after it
is cooled throughout, remain in the cheesy magma condition for an impracticably
long time.
We
We have found however, that if the cheesy magma is stirred and also allowed to cool,
it is in a comparatively short time transformed into good crystals of soda-alum.
find that if the stirring is excessive the crystals produced are small and difficult to
free from "mother liquor." We therefore give the minimum amount of stirring
necessary to ensure the speedy transformation of the cheesy magina and at the same
time to produce large and well-draining crystals.
After the cheesy magma has been thus transformed into good crystals, we separate
the impure "mother liquor" from the crystals by well known means and we utilise
the "mother liquor" according as its degree of purity may indicate, either (a) by
concentrating it to about the density previously named that is to say 1.45 specific
gravity and obtaining from it by the process already described another crop of crystals
of soda-alum or (b) by converting its soda-alum into potash-alum or ammonia-alum
by means of potash salts or ammonia salts, or (c) by employing it for the purification
of sewage or other impure waters.
We apply the principle of our present invention also to the treatment of a
mixture of hot strong solution of soda-alum and cold saturated solution of the
same.
The said mixture is treated exactly in the same way as the hot strong solution alone,
except that in the case of the mixed liquids, we do not remove all the "mother liquor."
resulting from the process after crystallization, as we do in the case of the hot strong
22 as is
solution alone. We remove only such a proportion of the "mother liquor
equivalent to the quantity introduced into the mixed liquids by the hot strong solution.
The remainder we keep for mixing with new quantities of hot strong solution. The

page_text: "mother liquor" which is removed we utilise in the same way as that produced when
operating with the hot strong solution alone.
It is obvious that in the case of the mixed liquid, it is the hot strong solution only
which gives the crop of alum and that therefore a larger total volume of liquid and
consequently larger crystallizing vessels are required to yield a given weight of
crystals, than when operating with the hot strong solution alone. On the other hand
the cheesy magma produced in the case of the mixed liquids is softer and thus easier
to manipulate than in the case of the hot solution alone.
Dated this Ninth day of January 1890.
W. T. CHEETHAM,
Manchester, Agent to the Applicants.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Alum.
We, FRANCIS MUDIE SPENCE and DAVID DICK SPENCE, both of the Manchester
Alum Works, Manchester, in the County of Lancaster, Manufacturing Chemists, and
ALEXANDER ESILMAN, of the same place, Analytical Chemist, in the employ of the
said Francis Mudie Spence and David Dick Spence, 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 :-
There are serious practical difficulties in the production of good crystals of soda
alum which are well known to manufacturers of aluminous compounds.
In the Specification filed in respect of the application of the before mentioned Francis
Mudie Spence and David Dick Spence for a Patent No. 17,888 dated November 9th,
1889 is particularly described a method of obtaining good crystals of soda alum by the
mixture of suitable hot and cold solutions and the treatment of what may be termed
the cheesy magma produced from such mixture.
According to our present invention which is founded on that which is the subject
of the said application for Patent No. 17,888 of 1889, we prepare from ordinary
sulphate of alumina and sulphate of soda or from alumino ferric and sulphate of soda
in about the proportions necessary to form soda alum a hot concentrated solution of
soda alum from which we in the manner hereinafter described produce a magma and
from the magma good crystals of soda alum.
We find that it is practically more economical to use alumino ferric than the purer
but dearer sulphates of alumina. We do not recommend the employment of what is
known as aluminous cake as it contains a large quantity of silica which would produce
a sediment, requiring a separating operation to be performed before sufficiently pure
crystals of soda alum could be obtained.
We take a boiling solution of alumino ferric of a strength not exceeding 1.3 specific
gravity and we dissolve in this the requisite quantity of ordinary commercial salt cake
the proportions used being about five parts by weight of alumino ferric cake to about
one part by weight of salt cake. We perform the operation in the lead-lined steam
dissolving box used by alum manufacturers.
While steam is being blown into this box we run into the box by means of a lead
pipe a stream of the alumino ferric solution and at the same time we shovel the salt
cake into the box till the whole of it has been dissolved by the alumino ferric solution
passing into and out of the box. The solution thus obtained is allowed to flow into a
lead-lined tank which as soon as all the charge is in is tightly covered. In this tank
we allow it to stand until practically all the suspended impurities have settled to the
bottom. We find that about twenty hours is sufficient for the purpose.
The clear liquid we then run off into a lead-lined evaporator fitted with coils of steam
pipe containing high pressure steam and by means of the coils we evaporate the solu-
tion till it attains a strength of about 1450 specific gravity. A strength much higher
than this would be found to yield on cooling a magna too stiff to be turned over with-
out difficulty. If instead of alumino ferric a much purer sulphate of alumina is

page_text: employed we evaporate the solution till it is about 1-425 specific gravity instead of
1-450. We then run the liquid through a fine copper sieve into a lead-lined cooler of
such a depth as will allow the magma that is to be produced to be turned over without
difficulty by means of a wooden shovel. We find that six inches depth of magma may
be turned over without difficulty, but we prefer a less depth because it can be cooled
more quickly. We then by means of a wooden rake agitate and cool the liquid till
the magma has formed, and we then by means of a wooden shovel turn the magma
over at intervals until it has been brought down to ordinary atmospheric temperature,
and becomes transformed into or produces good crystals of soda alum. The agitation
of the liquid necessarily tends to cool it more quickly and thus to hasten the formation
of the magma, but if the liquid is allowed to cool without agitation the magma pro-
duced may then be turned over as above described until it is transformed into or
produces good crystals. If the magma were not stirred or turned over at all it would
remain virtually unchanged for an impracticably long time, and would probably never
produce good crystals.
We find that if the stirring or turning over is excessive the crystals produced are
small and difficult to free from mother liquor. We therefore give the minimum
amount of stirring or turning over necessary to ensure the speedy transformation of
the magina, and at the same time to produce large and well-draining crystals. We
find that stirring or turning over at intervals of about two hours is quite suitable for
the purpose.
We find that a six inch depth of liquor is in this way changed into
magma, and the magma into crystals and mother liquor in from two to three days
according to the temperature of the surrounding air and that a less depth of liquor
is changed into magira and the magma into crystals and mother liquor in much
less time.
After the magma has been transformed we separate the impure mother liquor from
The quantity
the crystals by a centrifugal machine or by other suitable means.
of soda alum we obtain by the above described process is equal to or greater than the
weight of the alumino ferric cake employed to produce it, and is of course very much
freer from iron. We utilise the mother liquor from the crystals either (a) by con-
centrating it to about the density previously named that is to say to about 145 specific
gravity and obtaining from it by the process. already described another but more impure
crop of crystals of soda alum, or (b) by converting its soda aluin into potash alumn or
ammonia-alum, the alumina being readily crystallized out of the solution as potash alum or
ammonia alum on the addition to the heated solution of the proper potash of ammonia
salt, or (c) by employing it for the purification of sewage or other impure waters.
It is obvious that the treatment of the hot strong solution which is described in our
present Specification involves smaller vessels and a less amount of manipulation for
the production of a given weight of soda alum than is required by the treatment of
the hot and cold solutions described in Specification No. 17,888 dated November 9th,
1889. On the other hand the magma produced from the mixed liquids is softer and
thus easier to manipulate than that produced from the hot solution alone.
Should it be desired to produce a still purer soda alum than that yielded by the
crystals above referred to we adopt both in the case of the crystals produced by our
present invention and that of those produced by the method described in the Specifica-
tion of November 9th, 1889 a process analogous to that in general use for the purification
of ordinary crystallizable salts, viz. :-that of dissolving the crystals and re-crystallizing
but in the case of soda alum it is obvious that the solution of first crystals must
be brought through the above described magna stage before the purer second crystals
can be obtained. As in the case of the re-crystallization of other salts the mother
liquor of the second crystallization may however be used to wash the first crystals
after they have been well drained or otherwise freed as far as practicable from
their mother liquor. In this way purer second crystals can be obtained than can
be produced by dissolving and re-crystallizing unwashed first crystals. The liquor
which has washed the first crystals may be added to the new charges of alumino
ferric and salt cake solution or sulphate of alumina and salt cake solution as the
case may be which have been prepared for the production of new quantities of
.

page_text: first crystals and the whole may then be evaporated to the proper density for
producing first crystals.
It has already been pointed out when referring to the production of soda alum from
salt cake and a purer sulphate of alumina than alumino ferric that the purer solution
should be evaporated to about 1-425 specific gravity instead of about 145 as in the
case of the solution of salt cake and alumino ferrie. Similarly when the first crystals
of soda alum have been dissolved and a purer solution has thus been produced the
solution should be evaporated to a specific gravity of about 1-425 before producing
the magma which is to yield the second crystals.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
The manufacture of crystals of soda alum by the hereinbefore described process in
which a hot strong solution of sulphate of alumina and sulphate of soda in about the
proportions necessary to form soda alum is treated and the resulting magina is caused
to produce crystals, substantially as hereinbefore described.
Dated this 9th day of October 1890.
W. T. CHEETHAM,
Manchester, Agent to the Applicants.