IMPROVEMENTS IN OBTAINING AND PURIFYING OXALATE OF SODA, WHICH
Year: 1856

page_text: LETTERS PATENT to Thomas Roberts and John Dale, both of Manchester,
in the County of Lancaster, Manufacturing Chemists, and John Daniell
Pritchard, of Warrington, in the said County, Chemist, for the Invention
of "IMPROVEMENTS IN OBTAINING AND PURIFYING OXALATE OF SODA, WHICH
Sealed the 28th April 1857, and dated the 21st November 1856.
PROVISIONAL SPECIFICATION left by the said Thomas Roberts, John
Dale, and John Daniell Pritchard at the Office of the Commissioners of
Patents, with their Petition, on the 21st November 1856.
We, THOMAS ROBERTS and JOHN DALE, both of Manchester, in the County
of Lancaster, Manufacturing Chemists, and JOHN DANIELL PRITCHARD, of
Warrington, in the said County, Chemist, do hereby declare the nature of the
Invention for "IMPROVEMENTS IN OBTAINING AND PURIFYING OXALATE OP SODA,
WHICH IMPROVEMENTS ABE ALSO APPLICABLE TO THE MANUFACTURE OF OXALIC ACID,"
to be as follows:-
Before describing our Invention it is necessary to state that it has been
long known that oxalate of potash can be produced by submitting woody
fibre and other organic substances to the action of caustic potash at certain
temperatures, and it has also been stated that the same result can be obtained
by employing caustic soda in the place of caustic potash. In practice, however,
we find the amount of oxalate produced by the action of caustic soda alone

page_text: to be so small as to be entirely useless for any purposes of manufacture,
whilst the expense attending the use of caustic potash renders the process
unremunerative.
Now, our Invention consists in submitting woody fibre or other organic
substances to the combined action of caustic soda and caustic potash at a
temperature of 350° to 400° Fahrenheit, whereby oxalate of soda in con-
siderable amount is obtained mixed with carbonate of soda and potash, as
also with a small quantity of these alkalies in the caustic state.
We purify
the crude oxalate of soda thus obtained from the caustic and carbonated
alkalies with which it is mixed by the process herein-after described. But
it is necessary first to stato that the ordinary method of separating two soluble
salts by a process of solution and crystallization is inapplicable to this mixture,
owing to the slight solubility of oxalate of soda, and the exceedingly minute
state of division in which this latter salt exists when obtained by the ordinary
process of crystallization, its complete separation by this method being thus
rendered impossible.
Now, our improved process for purifying the crude salt consists in placing
the mixture of oxalate of soda and caustic and carbonated alkalies when
perfectly cold in tanks, and submitting it to the action of cold or warm water,
and this we prefer doing by the use of a series of tanks, whereby the partially
saturated solution in the first tank shall flow over the salt in the second, and
so on, according to the method known as continuous lixiviation as adopted in
soda-ash making. In this way the potash and other foreign substances are
dissolved away from the oxalate of soda, which is thus obtained in a pure or
nearly pure state, suitable for the manufacture of oxalic acid. By ovaporating
the wash water the potash is recovered, so that it may be again used.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Roberts, John Dale, and John Daniell Pritchard in
the Great Seal Patent Office on the 20th May 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, THOMAS S
ROBERTS and JOHN DALE, both of Manchester, in the County of Lancaster,
Manufacturing Chemists, and JonN DANIELL PRITCHARD, of Warrington, in
the said County, Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters-
Patent, bearing date the Twenty-first day of November, in the year of our 35
Lord One thousand eight hundred and fifty-six, in the twentieth year of Her

page_text: reign, did, for Herself, Her heirs and successors, give and grant unto us, the
said Thomas Roberts, John Dale, and John Daniel Pritchard, Her special
licence that we, the said Thomas Roberts, John Dale, and John Daniell
Pritchard, our executors, administrators, and assigns, or such others as we,
the said Thomas Roberts, John Dale, and John Daniell Pritchard, our
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 OBTAINING
AND PURIFYING OXALATE OF SODA, WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO
THE MANUFACTURE OF OXALIC ACID," upon the condition (amongst others) that
we, the said Thomas Roberts, John Dale, and John Daniell Pritchard, our
executors or administrators, by an instrument in writing under our or their
hands and seals, or under the hand and seal of one of us or them, 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 we, the said Thomas Roberts, John Dale, and
John Daniell Pritchard, do hereby declare the nature of the said Invention,
and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statenient thereof, that is to say :-
Before describing our Invention it is necessary to state that it has long
been known that the oxalate of potash can be produced by submitting woody
fibre and other organic substances to the action of caustic potash at certain
temperatures, and it has also been stated that the same result can be obtained
by employing caustic soda in the place of caustic potash. In practice, however,
we find the amount of oxalate produced by the action of caustic soda alone
to be so small as to be entirely useless for any purposes of manufacture,
whilst the expense. attending the use of caustic potash renders the process
unremunerative.
Now, our Invention consists. in submitting woody fibre or other organic
substances to the combined action of caustic soda and caustic potash at a
temperature of 350° to 400° Fahrenheit, whereby oxalate of soda in con-
siderable amount is obtained mixed with carbonates of soda and potash, as also
with a small quantity of these alkalies in the caustic state. We purify the
crude oxalate of soda thus obtained from the caustic and carbonated alkalies
used, which is mixed by the process herein-after described. But it is necessary

page_text: first to state that the ordinary method of separating two soluble salts by a
process of solution and crystallization is inapplicable to this mixture, owing to
the slight solubility of oxalate of soda, and the exceedingly minute state of
division in which this latter salt exists when obtained by the ordinary process
of crystallization, its complete separation by this method being thus rendered
impossible.
Now, our improved process for purifying the crude salt consists in placing
the mixture of oxalate of soda and caustic and carbonated alkalies when
perfectly cold in tanks, and submitting it to the action of cold or warm water,
and this we prefer doing by the use of a series of tanks, whereby the partially
saturated solution in the first tank shall flow over the salt in the second, and
so on, according to the method known as continuous lixiviation, as adopted in
soda-ash making.
In this way potash and other foreign substances are dissolved away from the
oxalate of soda, which is thus obtained in a pure or nearly pure state, suitable
for tho manufacture of oxalic acid. By evaporating the wash water the potash
is recovered, so that it may be again used.
And in order that our said Invention may be most fully understood and
readily carried into effect, we will proceed to describe the method in which we
prefer to conduct the manufacture.
We take a mixture of two equivalents of potash and threo equivalents of
soda, and after having causticised or partially causticised these alkalies we pro-
ceed to concentrate by evaporation until the same shall have reached a specific
gravity of 1950; but this point of concentration is not material, as these
alkalies may be used either continuously above or below this point.
Woody fibre or other organic substances (but the material we use is saw-
dust) is now mixed with the alkalino mixture of soda and potash, previously
described, the proportions we use being for every 100 parts of real alkali
contained in the concentrated solution 30 to 40 parts of sawdust or woody
fibre. The sawdust is spread upon plates of iron, and the alkali, in the pro-
portion described, is gradually and completely mixed with it, and care is taken
to spread the mixture evenly over the plate by the use of an iron rako or by
other means. So soon as this mixture shall have been effected, the temperature
is raised by heated flues underneath the plates, and this heating of the mixture
is continued during a period of from 4 to 6 hours, or thereabouts. The first
effect of the application of heat is the evaporation of the water contained in
the mixture, and after the expulsion of the water the heat is continued with
constant stirring of the mixture until it shall have reached a temperature of
from 350° to 400 Fahrenheit, at which temperature it must be carefully

page_text: maintained with constant stirring, until on inspection the woody fibre or saw-
dust is found to have disappeared. This having been effected, the operation is
complete, and the material produced will be found to contain a considerable
amount of oxalate of soda combined or mixed with other products. This
material we call crude oxalate.
To purify the crude oxalate, we place it when perfectly cold in iron tanks or
other vessels, and submit it to the action of cold or warm water; and this we
prefer doing by the use of a series of tanks so arranged, that the partially
saturated solution from the first tank, or that containing the already partially
washed salt, into the second, or that containing a salt more recently subjected
to the washing process, and so on, according to the method known as con-
tinuous lixiviation, as adopted in soda-ash making. The affusion of cold water
is continued on the oxalate until the liquor flowing from the vessel shall mark
a specific gravity of 1.030; there will then remain in the tank in almost a
state of purity the oxalate of soda contained in the crude oxalate, and which
oxalate may afterwards be converted into binoxalate of soda, or used for the
manufacture of oxalic acid.
In witness whereof, we, the said Thomas Roberts, John Dale, and John
Daniell Pritchard, havo hereunto set our hands and seals, this Twelfth
day of May, in the year of our Lord One thousand eight hundred and
fifty-seven.
THOMAS ROBERTS.
JOHN DALE.
(L.S.)
(L.S.)
JOHN DANIELL PRITCHARD (L.s.)
5 Witness,
JOHN MORRIS,
116, Gt. Ducio St., Manchester.