IMPROVEMENTS IN THE MANUFACTURE OF ALUM
Year: 1881

page_text: LETTERS PATENT to Peter Spence and Francis Mudio Spence, both of
Manchester, in the County of Lancaster, Manufacturing Chemists, for an
:
PROVISIONAL SPECIFICATION left by the said Peter Spence and Francis
Mudio Spence at the Office of the Commissioners of Patents on tho
24th December 1881.
PETER SPENCE and FRANCIS MUDIE SPENCE both of Manchester in the County
of Lancaster, Manufacturing Chemists. "IMPROVEMENTS IN THE MANUFACTURE
OF ALUM."
It is well known that soda alum if it could be economically made, would be
applicable to most of the purposes for which ammonia, and potash-alum, have
hitherto been used. Soda-alum, however, unlike potash and aminonia-alum, is so
largely soluble in the cold that a moderately strong hot solution of it say of 1-2
specific gravity will, on cooling yield no crystals at all, but if hot solutions of say
1-35 specific gravity are cooled, they become a magma with no distinct crystal-
lization; if this magma remains soft and pasty and is allowed to stand from threo
days to a fortnight, the greater part of it will crystallize into soda alum, but if
the hot solution was of specific gravity 1.42 the amorphous mass continues a hard
dry cake and no crystals are formed.
The crystals forined from the pasty magma are impure, and generally dirty, and
if again dissolved in water for purification by recrystallization the same difficulties
are met with, and render the process impracticable. In consequence of these
difliculties soda-alum has not been made on the large scale, and has not been
available for manufacturing purposes, and is only known as a chemical re-agent in
the laboratory.
The improvements which constitute our Invention consist in a mode or series of
operations by which all the difficulties existing as above set forth are overcome,
and by which soda-alumn of comparative purity can be manufactured with certainty
and economy.

page_text: In carrying out this our Invention we proceed as follows; we make a solution of
sulphate of alumina by any of the usual modes which are well known, but as
nearly free from sulphuric acid uncombined and also from sulphate of iron, as can
be conveniently obtained; but it is not essential that the solution should be quite
free from these matters.
In this solution, while being made or subsequently, we dissolve the requisite
quantity of sulphate of soda (or the materials necessary to form it) which will
combine with all the sulphate of alumina to produce soda-alum.
This compound solution clarified by settlement we boil up to a strength or
density of 110 "Twaddle" or 155 specific gravity at the boiling point. Were
we to allow this hot solution to cool it would form a dense, hard dry cake.
We now prepare a cold solution of soda-alum in water, of the density of
60 degrees "Twaddle," or thereabouts; this solution after the first operation will be
replaced by the mother liquor as will be shown; the solution is placed in a lead-
lined cooler, and we then run into it about one half of its bulk of the hot solution
at 110 Twaddle, stirring the contents of the cooler all the time, and when we
find the mixture has risen to a temperature of 95 to 100 degrees Fahrenheit, we
add no more hot liquor, but continue the stirring till the heat has gone down to
between 65 and 60 degrees Fahrenheit.
The liquor or mother liquor, as it is now called, may now be run or baled into
another lead cooler and is then ready for another batch of the hot solution being
added to it, with constant stirring as before. In the bottom of the first cooler
there will now be found a large deposit of soda alum in small crystals, and these
we now hoist up into deep draining tanks-lined-with-lead,-where_they_wil drain so
as to be nearly dry and of a white color, or they may be put through a centrifugal
machine as ordinarily used for expelling liquor from crystals, and by these means
or other drying process if needful, the crystals are made ready for use, and may be
packed in casks or bags, and sent into the market.
As the mother liquor will regularly increase in quantity we may use the surplus
by running it into the ordinary coolers where potash alum is being made, thus
economising the sulphate of alumina in the soda-alum solution so taken away.

page_text: 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 24th June 1882.
PETER SPENCE and FRANCIS MUDIE SPENCE both of Manchester in the County
of Lancaster, Manufacturing Chemists. "IMPROVEMENTS IN THE MANUFACTURE
OF ALUM."
It is well known that soda alum if it could be economically made would bo
applicable to most of the purposes for which ammonia and potash alum have
hitherto been used soda alum however unlike potash and ammonia alum is so
largely soluble in the cold that a moderately strong hot solution of it say of 1.2
specific gravity will on cooling yield no crystals at all, but if hot solutions of say
135 specific gravity are cooled they become a magma with no distinct crystalli-
zation, if the magına remain soft and pasty and is allowed to stand for a time
varying from three days to a fortnight the greater part of it will crystallize into
soda alum but if the hot solution was of specific gravity, 1.42 the amorphous mass
forms and continues a hard dry cake and no crystals are formed. The crystals
formed from the pasty mass are impure and generally dirty and if again dissolved
in water for purification by recrystallization the same difficulties are met with and
render the process impracticable. In consequence of these difficulties soda alum
has not been made on the large scale and has only been known as a chemical
re-agent in the laboratory. By means of our Invention we are enabled to manu-
facture soda alum with facility on a large commercial scale which has hitherto been
impracticable. In carrying out our said Invention we first form a solution of
sulphate of alumina by any of the ordinary methods taking care that the solution
is as nearly free from dissolved oxide of iron as it can conveniently be got and
that it is almost free from uncombined sulphuric acid, to this solution we add as
much sulphate of soda as is required to convert all the sulphate of alumina into
soda alum. The sulphate of soda may be added either while the solution is being
made or after it is formed by acting upon calcined china clay, shale bauxite or
other suitable aluminous matters with dilute or strong sulphuric acid as is well
known, and the solution thus formed and containing the sulphate of soda (which
however may preferably be subsequently added) we now reduce in density if
needful by adding water or the weak washings of the mud to be subsequently
referred to till it is about 50 degrees of Twaddle's hydrometer at the boiling point
or 1.25 specific gravity we then run the solution into a deep settling tank lined
with lead in which the liquor settles or becomes bright and free from mud which
falls to the bottom and is afterwards removed and washed. Part of this settled
liquor which must contain the sulphate of soda is now run into one of the lead
coolers where the soda alum is to be made or crystallized and there it is allowed
to cool but it will yield scarcely any crystals. The remainder of the clear liquor
and all subsequently made is run as required into an evaporating vessel where by
any suitable mode of boiling it is brought up to the strength of 110 degrees of
Twaddle's hydrometer or specific gravity 1.55 when this is reached the evaporation
is stopped and this now strong liquor is gradually run into the cooler amongst the
weaker and cold liquor previously mentioned, the contents of the cooler must be
continuously stirred during this addition and this stirring must be continued until
the mixture is cooled down to 65 to 60 degrees Fahrenheit, we would here point
out that while the mixture is being made the heat of the mixed liquors inust
frequently be ascertained and when the temperature rises to 100 to 105 degrees
Fahrenheit no more hot liquor should be added, if the mixed liquors on cooling run
into the magma or cheesy form more cold solution run in and stirred will ensure

page_text: perfect crystallization, for we have found that the most solid magma if pounded
up and mixed with a sufficiency of the cold solution will gradually change into
crystals but we prefer to avoid that mode of working as inconvenient. When the
mixed liquor has been stirred till cool enough it may then be run or baled out
into another similar cooler where a further quantity of hot liquor of high density
as before can be added to it and treated as before described and so on: In the
bottom of the first cooler before named will now be found a large deposit of
crystals of soda alum and these we now place in deep draining hoppers or funnels
of any convenient size lined with lead, a size we have found useful is about seven
and a half feet in depth, four feet diameter at the top and three feet at the bottom
provided with a loose and perforated bottom to allow the liquor to drain from the
said crystals, after remaining in the aforesaid draining funnels from twelve to
twenty four hours the soda alum crystals will have drained so as to be sufficiently
dry to be packed in casks or bags to be sent out for use. In place of the previously
described method of drying the crystals above referred to they may be dried by
means of a centrifugal machine as commonly used for draining or drying sugar in
crystals. The mother liquor which is thus used over and over again as a cold
solution of soda alum increases in quantity part of it must therefore be periodically
removed and we find it convenient to use such removed liquor in the coolers where
potash alum is being made and thus economise the sulphate of alumina it contains
by converting such sulphate of alumina into potash alum and thus the mother
liquor is to some extent periodically removed and prevented from becoming foul.
We may here state that in practice we find it useful to mix about three parts of
the cold solution or mother-liquor-with-one of the hot and strong liquor of specific
gravity of 155 as described. Having thus described the nature of our said
Invention and the manner in which the same is to be performed we desire it to be
understood that we claim as secured to us under the above in part recited Letters
Patent. The manufacture of soda alum substantially as before described by
mixing cold saturated solutions of said alum with stronger solutions of a higher
temperature as set forth and so preventing the tendency of such solutions to
solidify without crystallization or if solidified to change the solid into the
crystalline form by said mixture with the cold solution, and we also claim tho use
of such soda alum so made for the various purposes for which it is fitted and can
be used in industrial or manufacturing operations instead of potash or ammonia
alum. In witness whereof we the said Peter Spence and Francis Mudie Spence
have hereunto set our hands and seals this Twenty third day of June in the year
of our Lord One thousand eight hundred and eighty two.
Signed sealed and delivered by the
within named Peter Spence and
Francis Mudie Spence in the
presence of
W. T. CHEETHAM,
Patent Agent,
18, St. Ann's St.,
Manchester.
PETER SPENCE.
(L.S.)
FRANCIS MUDIE SPENCE. (L.S.)