IMPROVEMENTS IN THE MANU- FACTURE OF SODA AND POTASH
Year: 1862

page_text: LETTERS PATENT to William Gossage, of Widnes, in the County of
Lancaster, Chemist, for the Invention of "IMPROVEMENTS IN THE MANU-
FACTURE OF SODA AND POTASH."
Sealed the 12th September 1862, and dated the 17th March 1862.
PROVISIONAL SPECIFICATION left by the said William Gossage at
the Office of the Commissioners of Patents, with his Petition, on the
17th March 1862.
I, WILLIAM GOSSAGE, of Widnes, in the County of Lancaster, Chemist, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN THE
MANUFACTURE OF SODA AND POTASH," to be as follows:-
My improvements apply to the manufacture of the alkalies "soda and potash,"
in their caustic state or uncombined with carbonic acid. These alkalies in
their caustic state are usually manufactured by decomposing their carbonates
by the action of caustic lime, such decomposition being effected by mixing the
lime in a state of fine division with a solution of the carbonated alkali employed,
and agitating these well together, the action being usually assisted by the
injection of steam into the mixture. When the decomposition of the carbonated
alkali, has been thus effected, the mixture is allowed to remain quiescent,
carbonate of lime becomes deposited and caustic alkali in solution is run
off for use. The deposited carbonate of lime retains a large proportion of

page_text: alkali in solution mixed with it, which is afterwards imperfectly abstracted
from it by repeated washings with water. By these means a large quantity of
weak solutions of alkali are unavoidably obtained, which are objectionable for
use, and the deposited carbonate of lime still retains a valuable quantity of
alkali. When the caustic alkali is required in a solid state, the solutions are
evaporated until they become sufficiently concentrated to solidify on cooling.
I have found that the manufacture of caustic soda and caustic potash, by
decomposing carbonates of these alkalies by means of lime, is effected more
beneficially by causing solutions of the same to be filtered through slaked lime
mixed with small pieces of coal or of coke, or with some other suitable
material to give it porosity, the mixture being placed in proper vessels, arranged
for the purpose of filtration. I thus obtain a much smaller proportionate
quantity of weak solutions of caustic alkali, and I effect a more complete
abstraction of alkali from the carbonate of lime produced by the operation.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Gossage in the Great Seal Patent Office on the
17th September 1862.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
GOSSAGE, of Widnes, in the County of Lancaster, Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventeenth day of March, in the year of our Lord One
thousand eight hundred and sixty-two, in the twenty-fifth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
William Gossage, Her special license that I, the said William Gossage, my
executors, administrators, and assigns, or such others as I, the said William
Gossage, my executors, administrators, and 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 MANU
FACTURE OF SODA AND POTASH," upon the condition (amongst others) that I, the
said William Gossage, 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.
.
.:

page_text: NOW KNOW YE, that I, the said William Gossage, do hereby declare
the nature of my 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 :-
My improvements apply to the manufacture of the alkalies "soda and
potash in their caustic state or uncombined with carbonic acid. These
alkalies, in their caustic state are usually manufactured by decomposing their
carbonates by the action of caústic lime, such decomposition being effected by
mixing the lime in a state of fine division with a solution of the carbonated
alkali employed, and agitating these well together, the action being usually
assisted by the injection of steam into the mixture. When the decomposition
of the carbonated alkali has been thus effected, the mixture is allowed to
remain quiescent, carbonate of lime becomes deposited, and caustic alkali
in solution is run off for use. The deposited carbonate of lime retains a large
proportion of alkali in solution mixed with it, which is afterwards imperfectly
abstracted by repeated washings with water. By these means a large quantity
of weak solutions of alkali are unavoidably obtained, which are objectionable
for use, and the deposited carbonate of lime still retains a valuable quantity
of alkali. When the caustic alkali is required in a solid state, the solutions
are evaporated until they become sufficiently concentrated to solidify on
cooling.
I have found that the manufacture of caustic soda and caustic potash by
decomposing carbonates of these alkalies by means of lime is effected more
beneficially by causing solutions of the same to be. filtered through slaked
lime mixed with some suitable material to give it porosity, the mixture being
placed in proper vessels arranged for the purpose of filtration. I thus obtain
a much smaller proportionate quantity of weak solutions of caustic alkali, and
I effect a more complete abstraction of alkali from the carbonate of lime
produced by the operation.
I will describe the means by which I prefer to effect my Invention.
I provide a series of vats (say six in number), each about six feet square,
and five feet deep, and each having a perforated false bottom, supported at a.
height of about nine inches from the true bottom; I arrange these vats with
regard to their communication with each other in the same manner as a series
of vats is ordinarily arranged for the purpose of lixiviating rough alkali or
black ash in the manufacture of soda by the process well known as "continuous
filtration." In this arrangement provision is made whereby the liquor which.
has filtered through the contents of one vat ascends through a pipe from the
lower part of such vat, and flows into the next adjoining vat, and so on

page_text: consecutively through the whole or some part of the series of vats employed.
Each ascending pipe is provided with a plug to stop the passage through it
when required. I also adapt to each vat of the series a pipe extending from
the lower part of the same to the level of the upper part, such pipe having two.
branches at its upper part, each furnished with a stop-cock, through which
liquor may be conducted into the same vat again or into another vat of the
same series. I adapt also to each vat, just below its false bottom, a pipe
connected with an air pump, by means of which I can cause pressure of air to
be applied on the surface of the liquor contained in the lower part of the vat,
and thus occasion such liquor to be elevated through the pipe provided with
stop-cocks (as above mentioned), and to return into the upper part of the
same vat or to flow into another of the series. I also provide a steam pipe to
each vat for heating its contents by injection of steam therein, and an aperture
at the bottom of each vat (provided with a stop-cock) for running off liquor
from the same. I prepare caustic lime in powder by causing lumps of burned
lime to be slaked with water, and I mix such slaked lime with about an equal
bulk of small pieces of coke or of some other suitable material (such as lime-
stone) to give porosity to the mixture. I cover the false bottom of each vat
with a thin layer of small pieces of coke, and upon this-I place the mixture of
slaked lime and coke or other material until the vat is filled within about one
foot of the top. When I have a series of say three vats in regular operation
preparing caustic soda or potash by filtration according to my Invention, the
contents of one of these will have been treated by filtration (say for six hours)
with solution containing carbonated alkali (I will call this vat number one)
a second vat will have been treated by filtration (say for three hours) with
solution containing much caustic alkali and less carbonate (I will call this vat
number two) and a third will be freshly charged with the mixture of slaked
lime and coke, or other material (I will call this vat number three). Under
these conditions I cause the liquid contents of vat number two to be transferred
by pressure of air into vat number three, and the liquid contents of vat
number one into vat number two, and having prepared a hot solution of
carbonate of soda or of carbonate of potash (as the case may be) having a
specific gravity of about one thousand one hundred and fifty, I introduce this
solution into vat number one until the upper part of such vat is nearly filled
with liquor. Under these circumstances the solution in the upper part of each
vat filters slowly through the mixture of slaked lime and other material, and
accumulates in the lower part of the vat. I then cause pressure of air to be
applied (by the means herein-before explained) on the surface of the liquor,
which is thereby caused, to ascend through the pipe before mentioned, and

page_text: flows into the upper part of the vat when the pressure of air is stopped off, 'and
the liquor again filters through the slaked lime and other material into the.
lower part of the vat. This circulation is repeated at frequent intervals, say
for a period of three hours or until the liquor contained in vat number three.
is found to be sufficiently deprived of carbonic acid to be suitable for use as
caustic soda or caustic potash (as the case may be). During this time steam.
is injected into each of the vats to keep up the temperature of the liquors, and
this occasions dilution of the same, so that the liquor contained in vat number.
three will have a specific gravity of about one thousand one hundred. The
liquor in vat number three is now run off for use as caustic soda or potash (as
the case may be) when the liquor. contained in vat number two is transferred
by pressure of air into vat previously called number three, which now becomes
number two of the series, and the liquor in vat number one is transferred into
vat previously called number two, which now becomes number one of the
series, and the vat previously called number one becomes number three of
what I call the washing, portion of the series, of. vats. At this period a vat
which had been previously number one of the washing portion of the series is
emptied, and then filled with the mixture of slaked lime and coke, and it then
becomes vat number three of the alkali portion of the series. By this
arrangement it is provided that the fresh solution of carbonated alkali in the
first instance filters through slaked lime, through which two other portions of
solution of carbonated alkali have been previously filtered, and the greater
part of which slaked lime has consequently become converted into carbonate
of lime. The. solution of carbonated alkali loses a portion of its carbonic acid
during such filtration through vat number one, and is then transferred to vat
number two, where it filters through slaked lime, through which only one other
portion of solution has been previously filtered, and which slaked lime contains
a smaller proportion of carbonate of lime, and it is then transferred into vat
number three, wherein it filters through slaked lime, through which no solution
has been previously filtered, and it therein becomes converted into caustic.
soda or potash (as the case may be). The arrangement of vats is such that
each vat consecutively becomes number one, number two, and number three of
that portion of the series which is supplied with solution of carbonated alkali,
also becomes consecutively number one, number two, and number three of
that portion of the series which is supplied with water for washing out the
alkali previously retained by the slaked lime. Thus three of the series of vats
are used for the production of caustic soda or potash from carbonates of these
alkalies, and three of the series of vats are used for washing out the alkali
retained by the lime. In these last-mentioned vats the operation of washing

page_text: out the alkali by water is conducted in the same manner as alkali is washed
out from rough soda or black ash, water being supplied to vat number one of
that portion of the series used for washing, and flowing from, thence through
vats number two and three of this portion of the series, the liquor thus obtained
being mixed with the solution of carbonated alkali proposed to be converted
into caustic soda or potash.
have herein described the means which I consider best adapted for
effecting my "Improvements in the Manufacture of Soda and Potash," but
I do not confine myself in effecting my Invention to the precise means herein
described, as these may be varied to some extent.
I claim as my Invention, secured to me by the herein-before in part recited
Letters Patent, the manufacture, of soda and potash in a caustic state by
causing carbonate of soda or carbonate of potash in a state of solution to
become filtered through slaked lime in the manner herein-before described, or
some modification thereof.
In witness whereof, I, the said William Gossage; have hereunto set my
hand and seal, this Fifteenth day of September, in the year of our Lord
One thousand eight hundred and sixty-two.
WILL. GOSSAGE. (L.B.)