Ix- PROVEMENTS IN THE MANUFACTURE OF CARBONATE OF SODA."
Year: 1872

page_text: LETTERS PATENT to Alexander Robertson Arrott, of Saint Helens,
in the County of Lancaster, Chemist, for the Invention of "Ix-
PROVEMENTS IN THE MANUFACTURE OF CARBONATE OF SODA."
PROVISIONAL SPECIFICATION left by the said Alexander Robertson
Arrott at the Office of the Commissioners of Patents, with his
Petition, on the 16th August 1872.
I, ALEXANDER ROBERTSON ARROTT, of Saint Helens, in the County of
Lancaster, Chemist, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN THE MANUFACTURE OF CARBONATE OF SODA," to be as
follows:-
This Invention has for its object improvements in the manufacture of
carbonate of soda. For this purpose triphosphate of soda containing
three equivalents of soda to one of phosphoric acid is carbonated to
convert one equivalent of soda into carbonate of soda. The carbonate
of soda is then separated from the phosphate which is left, containing
two equivalents of soda to one of phosphoric acid. This diphosphate is
then again transformed into triphosphate and is again carbonated, and
so on continuously.

page_text: The manner in which I proceed is as follows:-I mix one equivalent
of phosphate of soda containing two equivalents of soda to one of phos-
phoric acid with one equivalent or rather more of common salt (a small
portion of common salt being volatilized during the process), and fuse
this mixture in a reverberatory or other suitable furnace, admitting
steam at the same time if necessary; the common salt is decomposed into
soda and hydrochloric acid; the acid is evolved, and the soda combines
with the phosphate to produce a phosphate containing three equivalents
of soda to one of phosphoric acid or triphosphate.
When the decomposition is complete I remove the triphosphate from
the furnace, I dissolve it in water, and expose it to the action of carbonic
acid, by which the third equivalent of soda is converted into carbonate
of soda. Or I add bicarbonate of soda in such quantity that the second
equivalent of carbonic acid will convert the third equivalent of soda in
the triphosphate into carbonate of soda. I then evaporate the solution
and separate the phosphate of soda from the carbonate by crystallization.
Or I moisten the triphosphate of soda and expose it to the action of car-
bonic acid; carbonate of soda is produced, and this I separate from the
phosphate by washing with cold water.
The phosphate of soda separated from the carbonate contains two
equivalents of soda to one of phosphoric acid, and this I use again for
the decomposition of common salt.
In place of mixing the diphosphate with the common salt I also
obtain triphosphate by exposing diphosphate of soda at a bright red heat
in a reverberatory or other suitable furnace to vapour of common salt
and steam, and this I treat as before mentioned for the production of
carbonate of soda.

page_text: -
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixteenth day of August, in the year.
of our Lord One thousand eight hundred and seventy-two, in the thirty-.
sixth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Alexander Robertson Arrott; Her special
license that I, the said Alexander Robertson Arrott, my executors,
administrators, and assigns, or such others as I, the said Alexander
Robertson Arrott, 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, sliould and lawfully might
make, use, exercise, and vend within the United Kingdom of Great Britain
and Ireland, theo Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF CARBONATE OF SODA," upon 'thic con- '
dition (amongst others) that I, the said Alexander Robertson Arrott, 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 tho
date of the said Letters Patent.
M
NOW KNOW YE, that I, the said Alexander Robertson Arrott;,
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 statement thereof,, that is to.:
say:
This Invention has for its object improvements in the manufacture of
carbonate of soda. For this purpose triphosphate of soda containing..
three equivalents of soda to one of phosphoric acid is carbonated. to
convert one equivalent of soda into carbonate of soda. The carbonate:
of soda is then separated. from the phosphate which is left, containing
two equivalents of soda to one of phosphoric acid. This diphosphate is
then again transformed into triphosphate and is again carbonated, and so
on continuously.
The manner in which I proceed is as follows:-I mix one equivalent
of phosphate of soda, containing two equivalents of soda to one of
-phosphoric acid, with one equivalent or rather more of common salt (a.
small portion of common salt being volatilised during the process), and.

page_text: fuse this mixture in a reverberatory or other suitable furnace, admitting
steam at the same time if necessary; the common salt is decomposed
into soda and hydrochloric acid, the acid is evolved, and the soda com-
bines with the phosphate to produce a phosphate containing three
equivalents of soda to one of phosphoric acid or triphosphate.
When the decomposition is complete I remove the triphosphate from
the furnace, I dissolve it in water and expose it to the action of car-
bonic acid, by which the third equivalent of soda is converted into
carbonate of soda; or I add bicarbonate of soda in such quantity that
the second equivalent of carbonic acid will convert the third equivalent
of soda in the triphosphate into carbonate of soda. I then evaporate the
solution and separate the phosphate of soda from the carbonate by
crystallization. Or I moisten the triphosphate of soda and expose it
to the action of carbonic acid; carbonate of soda is produced, and this I
separate from the phosphate by washing with cold water.
The phosphate of soda separated from the carbonate contains two
equivalents of soda to one of phosphoric acid, and this I use again for
the decomposition of common salt.
In place of mixing the diphosphate with the common salt I also
obtain triphosphate by exposing diphosphate of soda at a bright red
heat in a reverberatory or other suitable furnace to vapour of common
salt and steam, and this I treat as before mentioned for the production
of carbonate of soda..
Thus it will be seen that the means of operating may be varied, but
in carrying out my Invention I prefer to proceed as follows, and this
method I believe will generally be found most convenient :-I mix the
diphosphate and common salt and fuse the mixture in a reverberatory
furnace, admitting steam in order to facilitate the decomposition; the
mixture at first fuses casily, but as the formation of triphosphate
proceeds it becomes less fusible and sustains a full red or incipient
white heat without fusing, and in this state is turned over with a
paddle or rake so as to expose fresh surfaces and facilitate the
decomposition.
When the decomposition of the salt is complete, as shown by the
mixture ceasing to evolve hydrochloric acid, I remove the mass from
the furnace; I dissolve in water and expose the solution to the action of

page_text: "
carbonic acid by passing it through a tower containing coke, through
which carbonic acid is passed in the same manner as is extensively used
at present for carbonating soda ash. I then evaporate the carbonated
solution and allow it to cool, when diphosphate of soda crystallizes and
carbonate of soda remains in solution. I find it most advantageous to
evaporate the liquor to such a strength that on cooling crystallization
begins at about 110° Fahrenheit. If the whole of the diphosphate has
not separated I concentrate a second time and allow the solution to cool.
The solution of carbonate I dry up into soda ash or crystallize as soda
crystals; a very small quantity of diphosphate remains mixed with the
carbonate, and this loss must be replaced by adding small portions of
diphosphate so as to keep up the original quantity.
Having thus described the nature of my said Invention, and the
manner of performing the same, I would have it understood that I
claim the method of manufacturing carbonate of soda by successively
carbonating the triphosphate and then reconverting the diphosphate,
which together with the carbonate is so obtained back into triphosphato
ready to be again carbonated, substantially as described.
In witness whereof, I, the said Alexander Robertson Arrott, have
hereunto set my hand and scal, this Twelfth day of February, in
the year of our Lord One thousand eight hundred and seventy-
threc.