Improvements in the Manufacture of Alum.
Year: 1889

page_text: Date of Application, 9th Nov., 1889
Complete Specification Left, 11th Aug., 1890-Accepted, 18th Oct., 1890
PROYIS.
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 do
hereby declare the nature of this invention to be as follows:-
The practical difficulties in the way of the economical production of soda-alum are
well known to alum manufacturers.
Unlike the solution of potash or ammonia-alum, a boiling solution of soda-alum of
density of about 60° of Twaddell's hydrometer or 1-3 specific gravity gives on
cooling scarcely any or no crystals and one which is much above this density instead
of yielding on cooling a crop of well defined crystals from which the impure" mother
liquor" may readily be drained out, resolves itself into an opaque, viscid or cheesy
magma.
In the Specification of Patent No. 5650 dated 24th December 1881 granted to
Peter Spence and the above named Francis Mudie Spence for "Improvements in the
manufacture of alum" this difficulty was overcome by running the hot strong solution
of soda-alam under prescribed conditions into a cold saturated solution of soda-alum,
good crystals free from the cheesy magma described being obtained in this way.
It has been found however in actual working that the quantity of cold saturated
solution of soda-alum required for this purpose is relatively so largo as to inako it
difficult by ordinary means to cool down the whole to the required temperature to
obtain the crop of crystals and thus the process is rendered unremunerative.
The Specification referred to states that if the magma should happen to be formed
it could be made to crystallize by running in more cold liquor and stirring, as it had
been found that the most solid magna if pounded up and mixed with a sufficiency of
the cold saturated solution will gradually change into crystals but that it is profernble
to avoid this mode of working as inconvenient.
By our present invention we prepare in the usual way from ordinary sulphate of
alumina and sulphate of soda or from aluminoferric and sulphate of soda a hot highly
concentrated solution of soda-alum and we mix with this a sufficiently small pro-
portion of cold saturated solution of soda-alum to yield, on cooling a magma not too
stiff to be freely stirred or turned over. We then by any suitable means agitato and
cool the mixed liquids till the magma has formed and we then by any suitable means
cool and at the same time turn the magma over and over till it has been brought down
to ordinary atmospheric temperature and till it has been transformed into good
crystals of soda-alum. Wo find that by these means the magma is converted within a
comparatively short time into good soda-alum crystals from which the impure "mother
liquor" may be readily drained out or separated by well-known moans and we are
thus enabled to obtain in the form of good crystals as large a crop of soda-alum as is
obtained by the process specified in the Specification of the Patent referred to without
the serious practical disadvantage which that process involves.
"
"
From the resultant "mother liquor we remove a sufficient proportion to withdraw
all or practically all the iron that was introduced by the hot concentrated solution and
we reserve the remainder of the "mother liquor "for addition to new increments of
hot concentrated solution as already described. The proportion of "mother liquor
withdrawn we utilize either for conversion into potash-aluin or ammonia-alum by well-
known means or we use it either in the liquid form or in the form of a cake for the
purification of sewage or other impure walers or for any purpose for which impure
aluminous compounds may be employed.
1000

page_text: 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, 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 practical difficulties in the way of the economical production of soda-alum
suitable for the leading use of ordinary alum viz. the sizing of paper are well known
to alum manufacturers.
Unlike the solution of potash or ammonia-alum a boiling solution of soda-alumi
of a density of about 60 degrees of Twaddell's hydrometer or 13 specific gravity
gives on cooling scarcely any or no crystals, and one which is much above this
density instead of yielding on cooling a crop of well defined crystals from which
the impure "mother liquor may readily be drained out resolves itself into an
opaque viscid, or cheesy magma.
13
In the Specification of Patent No. 5650 dated 24th December 1881 granted to
Peter Spence and the above named Francis Mudie Spence for "Improvements in the
manufacture of alum" this difficulty was overcome by running the hot strong solution
of soda-alum under prescribed conditions into a cold saturated solution of soda-alum,
good crystals free from the cheesy magma described being obtained in this way.
It has been found however in actual working that the quantity of cold saturated
solution of soda-alum required for this purpose is relatively so large as to make it.
difficult by ordinary means to cool down the whole to the required temperature to
obtain the crop of crystals and thus the process is rendered unremunerative.
The Specification referred to states that if the magma should happen to be formed
it could be made to crystallise by running in more cold liquor and stirring as it had
been found that the most solid magna if pounded up and mixed with a sufficiency of
the cold saturated solution will gradually change into crystals but that it is preferable
to avoid this mode of working as inconvenient.
By our present invention we prepare in the usual way from ordinary sulphate of
alumina and sulphate of soda or from alumino-ferric and sulphate of soda a hot highly
concentrated solution of soda-alum and we mix with this a sufficiently small pro-
portion of cold saturated solution of soda-alum to yield on cooling a magma not too
stiff to be freely stirred or turned over.
We find that it is practically more economical to use alumino-ferric than a purer
sulphate of alumina. We take a solution of alumino-ferric of a strength not
exceeding 60 degrees Twaddell and we dissolvo in this the requisite quantity of
ordinary commercial salt cake containing the usual percentage of sulphate of soda
the proportions used being about 5 parts by weight of alumino-ferric cake to 1 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
through the box a stream of the alumino-ferric solution and at the same time we shovel
in the salt cake, till the whole of it has been dissolved by the alumino-ferric solution.
The solution thus obtained is allowed to flow into a tightly covered lead-lined tank in
which we allow it to stand until the suspended impurities have been settled out. We
allow it to stand about twenty hours. The clear liquid we then run off into a lead-
lined evaporator fitted with a coil of lead pipes containing high pressure steam and by
means of this coil we boil down the solution until it attains a strength of about
90 degrees Twaddell.
We then run this boiling liquid into a cold saturated solution of soda-alum prepared
in the mode that will be presently described. We run about two parts by volume of
the hot solution into about one part by volume of the cold liquid, taking care to
thoroughly mix the two liquids by means of a suitable stirrer. We then run the
mixed liquids into a lead-lined cooler, of such a depth as will allow the magma that is

page_text: to be produced to be easily turned over by means of a wooden shovel. We then by
means of a wooden rake agitate and cool the mixed liquids 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 till it has been
transformed into good crystals of soda-alum.
The agitation of the mixed liquids necessarily tends to cool them more quickly and
thus to hasten the formation of the magma but if the mixed liquids are allowed to cool
without agitation the magma produced may then be turned over as above described
until it is transformed into good crystals.
We find that by these means the magma is converted within a comparatively short
time into good soda-alum crystals from which the impure "mother liquor" may
be
readily drained out by any well-known means or may be separated by a centrifugal
machine. We are thus enabled to obtain in the form of good crystals as largo a crop
of soda-alum as is obtained by the process specified in the Specification of the Patent
referred to without the serious practical disadvantage which that process involves.
We obtain in this way a crop of soda-alum crystals equal to or greater than the weight
of the alumino-ferric cake employed to produce it.
From the resultant mother liquor we remove such proportion as will together with
the small portion of iron removed by the alum itself withdraw all or practically all
the iron that was introduced by the hot concentrated solution, and we reserve the
remainder of the mother liquor which is the "cold saturated solution" already
referred to for mixing with new increments of hot concentrated solution as already
described. The proportion of "mother liquor" withdrawn wo utilize either (a) for
conversion into potash-alum or ammonia-alum by well known means the alumina
being readily crystallized out of the solution as potash-alum or ammonia-alum on the
addition of the proper potash or ammonia salts or (b) we use it either in the liquid
form or in the form of a cake for the purification of sewage or other impure waters or
for any purpose for which impuro aluminous compounds may be employed.
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
claim is :-
we
For obtaining crystals of soda alum the hereinbefore described process which
consists in treating (a) a mixture of a hot strong solution of sulphate of alumina and
sulphate of soda in about the proportions necessary to form soda-alum and a cold
saturated solution of the same and (6) the magma produced from such mixture
substantially as herein before described.
Dated this Ninth day of Au 1800