IMPROVEMENTS IN THE MANUFACTURE OF CAUSTIC SODA AND CAUSTIC POTASH
Year: 1863

page_text: LETTERS PATENT to James Shanks, of Saint Helens, in the County of.
Lancaster, Manufacturing Chemist, for the Invention of "IMPROVEMENTS
IN THE MANUFACTURE OF CAUSTIC SODA AND CAUSTIC POTASH."
Sealed the 31st May 1864, and dated the 22nd December 1863.
PROVISIONAL SPECIFICATION left by the said James Shanks at the
Office of the Commissioners of Patents, with his Petition, on the
22nd December 1863.
I, JAMES SHANKS, of Saint Helens, in the County of Lancaster, Manu-
facturing Chemist, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF CAUSTIC SODA AND CAUSTIC POTASH," to
be as follows:-
My improvements apply to the manufacture of caustic soda and caustic
potash from the carbonates of these alkaline bases. This manufacture has
hitherto been effected by causing carbonate of soda or carbonate of potash (as
the case may be) in solution to be boiled or otherwise mixed with caustic
lime, which by its superior affinity (under certain circumstances) for carbonic
acid as compared with the affinity of such alkaline bases for the same acid,
decomposed the alkaline carbonates, thereby producing the corresponding
alkalies in the caustic state. It is well known that to effect such decom..
position perfectly (under such circumstances) it is necessary to employ the
solution of alkaline carbonate (which is being decomposed) at such a low
specific gravity that the caustic solutions obtained therefrom have not a

page_text: higher specific gravity than 1.100. As a consequence of this, the caustic
alkali is obtained mixed with a large proportion of water, which proportion is
greatly increased by subsequent washings of the residual carbonate of lime to
extract the alkali mixed therewith.
In ascertaining the nature of my Invention, I will describe the mode in
which I carry the same into effect when I am manufacturing caustic soda
from solutions of carbonate of soda, the same details apply to the manufacture
of caustic potash from solutions of carbonate of potash.
Solutions of carbonate of soda can either be made by dissolving carbonate
of soda in water, or such solutions can be used, for the purposes of my
Invention, as occur in the ordinary manufacture of soda, and are known as
"black ash liquors" or "red liquors." The two last-named liquors contain (as
is well known) some caustic soda already formed, also some sulphide of
sodium. If such liquors are not already in a state of saturation, or nearly so,
I cause such liquors to be concentrated by evaporation of water therefrom
until I find that some carbonate of soda in the state of salts begins to be
thrown out of solution. I take a portion of such solution as I am about to
employ, and I ascertain the total quantity of carbonate of soda present therein;
I then add thereto forty-two parts of caustic lime for each fifty-four parts of
carbonate of soda present; a violent reaction takes place, and the mixture
becomes a pasty mass. I transfer such pasty mass into a furnace such as is
ordinarily employed for desiccating and oxidizing soda salts for the production
of soda ash. By the application of heat together with atmospheric air, I
cause such pasty mass to become desiccated, and any sulphide of sodium
present therein to become oxidized, so as to produce sulphite or sulphate of
soda. When I find, by testing, that this oxidation has become sufficiently
effected, I withdraw from the furnace the dry powder thus obtained; I mix
this dry powder with water or with weak solution of caustic soda from former
processes, and by injection of steam therein, together with thorough agitation,
I reduce the mixture to the consistence of cream. The mixture is now a
solution of caustic soda mixed with carbonate of lime and some caustic lime;
I transfer this mixture on to a filtering bed, under which I cause a partial
vacuum to be formed, by which means I cause atmospheric pressure to be
exerted on the surface of the mixture, and thus greatly expedite the filtration.
When the filtration has proceeded to such an extent that the solid matter is
no longer covered with supernatant fluid, I cause water to flow into the
filtering vessel so as to keep the solid matter continually covered, and I
continue such addition of water until I find the solution running off is free or
nearly free from caustic soda. By these means I obtain solutions of caustic

page_text: alkali at a much higher specific gravity than the solutions hitherto obtained
from mixtures of lime and carbonated alkalies, whereby I effect a great
economy in the concentration of such liquids for the production of caustic
alkalies in a solid state. I also effect much economy in the expenses of con-
ducting the manufacture of caustic soda and caustic potash.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said James Shanks in the Great Seal Patent Office on the
4th June 1864.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
SHANKS, of Saint Helens, in the County of Lancaster, Manufacturing Chemist,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-second day of December, in the year of our
Lord One thousand eight hundred and sixty-three, in the twenty-seventh year
of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said James Shanks, Her special licence that I, the said
James Shanks, my executors, administrators, and assigns, or such others
as I, the said James Shanks, 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 MANUFACTURE OF CAUSTIC SODA AND CAUSTIC
POTASH," upon the condition (amongst others) that I, the said James Shanks,
my executors or administrators, by an instrument in writing under my, or
their, or one of their hands and seals; 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.
NOW KNOW YE, that I, the said James Shanks, 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:-
My improvements apply to the manufacture of caustic soda and caustic
potash from the carbonates of these alkaline bases. This manufacture has

page_text: hitherto been effected by causing carbonate of soda, or carbonate of potash (as
the case may be), in solution to be boiled or otherwise mixed with caustic
lime, by which its superior afinity (under certain circumstances) for carbonic
acid, as compared with the affinity of such alkaline bases for the same acid
decomposed the alkaline carbonates, thereby producing the corresponding alkalies
in the caustic state. It is well known that to effect such decomposition perfectly
(under such circumstances) it is necessary to employ the solution of alkaline
carbonate (which is being decomposed) at such a low specific gravity that the
.caustic solutions obtained therefrom have not a higher specific gravity than
1.100. As a consequence of this the caustic alkali is obtained mixed with a
large proportion of water, which proportion is greatly increased by subsequent
washings of the residual carbonate of lime to extract the alkali mixed
'therewith.
In ascertaining the nature of my Invention, I will describe the mode in
which I carry the same into effect when I am manufacturing caustic soda
from solutions of carbonate of soda, the same details apply to the manufacture
of caustic potash from solutions of carbonate of potash.
Solutions of carbonate of soda can either be made by dissolving carbonate
of soda in water, or each solutions can be used (for the purposes of my
Invention) as occur in the ordinary manufacture of soda, and are known
as "black ash liquors" or "red liquors." The two last named liquors contain
(as is well known) some caustic soda already formed, also some sulphide of
sodium. If such liquors are not already in a state of saturation, or nearly so,
I cause such liquors to be concentrated by evaporation of water thereof until
I find that some carbonate of soda in the state of salt begins to be thrown
out of solution. I introduce into an iron vessel a portion of such solution as
I am about to employ, and I ascertain by testing a sample thereof the total
quantity of carbonate of soda present therein, I then add to the solution about
forty-two parts of caustic lime for each fifty-four parts of carbonate of soda
present therein, and I cause these to be well mixed together. (In working
with solutions of carbonate of potash for the production of caustic potash, I
'employ about forty-two parts of caustic lime for each seventy parts of carbonate
of potash contained in such solution; a violent reaction takes place and the
mixture speedily becomes a pasty mass. I transfer such pasty mass into a
reverberatory furnace (such as is ordinarily employed for desiccating and s
oxidizing soda salts for the production of soda ash). By the application of
heat thereto, together with atmospheric air, and by working such mass in the
same manner as soda salts are worked in finishing soda ash, I cause such pasty
mass to become desiccated, and any sulphide of sodium present. therein to

page_text: become oxidized so as to convert such sulphide into sulphite of soda, and I
thereby obtain a product in a state favorable for the separation of the soluble
caustic soda from the insoluble compounds of lime by liviviation and filtration as
herein-after described. When I find by testing the product that this oxidation
has become sufficiently effected, or in other words the product no longer shews
the presence of sulphide, I withdraw from the furnace the dry powder thus
obtained. I mix this dry powder in a suitable vessel with water or with weak
solution of caustic soda (resulting from former processes) and by injection of
steam therein, together with thorough agitation, I reduce the mixture to the
consistence of cream, and I continue such agitation until I find by filtering a
portion of the mixture and testing the clear solution (thus obtained) with acid,
that neutralization takes place without giving off carbonic acid gas. The
mixture is now a solution of caustic soda together with carbonate of lime and
some caustic lime. I transfer this mixture on to a filtering bed, under which
I cause a partial vacuum to be formed, by which means I cause atmospheric
pressure to be exerted on the surface of the mixture, and thus greatly expedite
the filtration. When the filtration has proceeded to such an extent that the
solid matter is no longer covered with supernatant fluid, I cause water to flow
into the filtering vessel, so as to keep the solid matter constantly covered with
liquid, and continue such addition of water until I find the solution running
off is free or nearly free from caustic soda.
I have found that a filtering bed constructed in the following manner is well
adapted for effecting such filtration. I provide a vessel of iron of any convenient
shape, preferring an oblong form, about four or five feet deep and about eight
feet wide and ten feet long. I cause strong bearers of iron to be supported
across the vessel about one foot from the bottom, and upon these I place
perforated iron plates so as to form a perforated false bottom; I cover
such plates with a sheet or webbing of iron wire gauze of about a quarter
inch mesh, and I cover such gauze with a thick sheet of cotton cloth of strong
open texture, and upon this place another sheet of iron wire gauze. Previously
to introducing the liquid mixture on to the filtering bed, I apply a paste of
stiff lime (resulting from a former operation) around the edges of the filtering
bed to prevent the liquid mixture passing such edges. I connect the lower
part of such filtering vessel with an exhausting air pump, and I thereby cause
a partial vacuum to be formed in such lower part, and atmospheric pressure
to be exerted on the surface of the liquid mixture contained in such apparatus,
or in place of using an air pump I can obtain the same object by connecting
the lower part of the filtering vessel with a vessel which can be alternately

page_text: filled with steam, and used as a condenser, also thus producing a partial
vacuum.
By these means I obtain solutions of caustic alkali at a much higher
specific gravity than the solutions hitherto obtained by decomposing carbonated
alkalies by means of lime, whereby I effect a great economy in the concentration
of such liquids for the subsequent production of caustic alkalies in a solid state.
I also effect much economy in the expenses of conducting the manufacture of
caustic soda and caustic potash from the carbonates of these alkalies.
I have herein-before described and ascertained the means which I consider
to be most suitable for effecting the objects of my Invention of "I Improve-
ments in the Manufacture of Caustic Soda and Caustic Potash," also the
proportions of materials I prefer to employ for such purpose; but I do not
confine myself to the precise means or proportions herein-before indicated, as
the same may be varied to some extent without deviating from the nature of
my Invention. I claim as my Invention secured to me by the herein-before
in part recited Letters Patent,
Firstly, the desiccation and oxydation (when such oxydation is required) of
a mixture of caustic lime with solution of carbonate of soda, or of carbonate
of potash (as the case may be), by heating the same in a reverberatory
furnace, or other suitable apparatus, with access of air, and thus producing a
dry compound in a state favorable for the abstraction of caustic soda or caustic
potash therefrom by liviviation and filtration.
Secondly, the abstraction of solutions of caustic soda or of caustic potash from
such disiccated compound by liviviation and filtration, such solutions being
thereby obtained at higher gravities than similar solutions have heretofore been
obtained from mixtures of solutions of carbonate of soda or of carbonate of
potash with lime.
In witness whereof, I, the said James Shanks, have hereunto set my
hand and seal, this Third day of June, in the year of our Lord One
thousand eight hundred and sixty-four.
JAMES SHANKS. (L.S.)