IMPROVEMENTS IN PRODUCING CAUSTIC SODA AND CAUSTIC POTASH
Year: 1870

page_text: LETTERS PATENT to Thomas James Smith, of the Firm of Robertson,
Brooman, and Company, of 166, Fleet Street, in the City of London,
Patent Agents, for the Invention of “IMPROVEMENTS IN PRODUCING
CAUSTIC SODA AND CAUSTIC POTASH."-A communication from abroad
by Cyprien Marie Tessié du Motay, of Paris, France, Chemist.
Sealed the 15th November 1870, and dated the 17th June 1870.
PROVISIONAL SPECIFICATION left by the said Thomas James Smith
at the Office of the Commissioners of Patents, with his Petition,
on the 17th June 1870.
I, THOMAS JAMES SMITH, of the Firm of Robertson, Brooman, and
3 Company, of 166, Fleet Street, in the City of London, Patent Agents,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
PRODUCING CAUSTIC SODA AND CAUSTIC POTASH," to be as follows:-
This Invention is based upon the transformation of sulphuret of
sodium into caustic soda or of sulphuret of potassium into caustic potashi

page_text: by means of one or the other of two chemical reactions in which this
Invention consists; these two reactions give rise to two processes, one of
which may be called dry and the other wet, and which I proceed to
describe.
The Dry Process.-The inventor has found that an equivalent of
snlphuret of sodium put in the presence of and melted with an equivalent
of hydrate of soda or hydrate of lime and an equivalent of cast iron or iron
at a red heat is transformed into caustic soda and sulphuret of iron. The
reaction which brings about this transformation results from a galvanic
action, which I may explain as follows:-The water of the hydrate of
soda or of the hydrate of lime is decomposed by the iron, which passes
into the state of oxide of iron, and the latter in setting the hydrogen free
gives up oxide of sodium and sulphuret of iron. This operation may be
performed for commercial purposes upon the sole plate of a reverberatory
furnace in which the materials above enumerated have been placed.
The soda obtained after the fusion is dissolved in warm filtered water in
order to separate it from the sulphuret of iron, and is then concentrated
by the ordinary methods.
The Wet Process.-The reaction which is the base of the this process
is as follows:-Taking the acid phosphate of lime the inventor causes
one of the equivalents of the phosphate to react upon two equivalents of
sulphuret of sodium; it separates from the sulphohydric acid, and the
lime is precipitated in the state of basic phosphate of lime, at the same
time forming a basic phosphate of soda. Instead and in place of one of
the two equivalents of sulphuret of sodium I may add an equivalent of
sulphate of soda, which will transform the acid phosphate of lime into
acid phosphate of soda and into sulphate of lime, which precipitates.
The acid phosphate of soda put in the presence of sulphurct of sodium
becomes transformed into basic phosphate of soda. It is this basic
phosphate of soda which the inventor decomposes by the caustic lime,
which leaves the soda bare and becomes itself transformed into basic
phosphate of lime. The two insoluble residues of basic phosphate of
lime are reunited and treated subsequently with sulphuric acid, which
again transforms them into acid phosphate of lime, which will serve for
fresh operations. The operations just described are effected either cold
or under the influence of heat in vessels of iron or wood provided with
double bottoms and serpentine pipes permitting, if thought desirable, of

page_text: their being heated by steam. The soda produced is separated by
decantation and concentrated according to the methods now employed.
Although I have described them as used for the production of caustic
soda, these methods are applicable for the production of caustic potash
and its salts.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas James Smith in the Great Seal Patent
Office on the 17th December 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
JAMES SMITH, of the Firm of Robertson, Brooman, and Company, of
166, Fleet Street, in the City of London, Patent Agents, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventeenth day of June, in the year of
our Lord One thousand eight hundred and seventy, in the thirty-third year
of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said Thomas James Smith, Her special licence that I, the
said Thomas James Smith, my executors, administrators, and assigns,
or such others as I, the said Thomas James Smith, 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
PRODUCING CAUSTIC SODA AND CAUSTIC POTASH," (communicated to me from
abroad by Cyprien Mario Tessié du Motay, of Paris, France, Chemist,)
upon the condition (amongst others) that I, the said Thomas James
Smith, 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
Scal Patent Office within six calendar months next and immediately
after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Thomas James Smith, do hereby
declare the nature of the said Invention, and in what manner the same

page_text: is to be performed, to be particularly described and ascertained in and
by the following statement, that is to say :-
This Invention is based upon the transformation of sulphuret of sodium
into caustic soda, or of sulphuret of potassium into caustic potash, by
means of one or the other of two chemical reactions in which this
Invention consists,―
These two reactions give rise to two processes, one of which may be
called dry, the other wet, and which I proceed to describe.
The Dry Process.-The Inventor has found that an equivalent of
sulphuret of sodium put in the presence of and melted with an equivalent
of hydrate of soda or hydrate of lime, and an equivalent of cast iron
or iron at a red heat is transformed into caustic soda and sulphuret of
iron. The reaction which brings about this transformation results from
a galvanic action which I may explain as follows:-
The water of the hydrate of soda or of the hydrate of lime is decom-
posed by the iron which passes into the state of oxide of iron, and the
latter in setting the hydrogen free gives up oxide of sodium and sulphuret
of iron. This operation may be performed for commercial purposes
upon the sole plate of a reverberatory furnace in which the materials
above enumerated have been placed. The soda obtained after the fusion
is dissolved in warm filtered water in order to separate it from the
sulphuret of iron, and is then concentrated by the ordinary methods.
The Wet Process.-The reaction which is the base of this process is
as follows: Taking the acid phosphate of lime the Inventor causes
one of the equivalents of the phosphate to react upon two equivalents
of sulphuret of sodium. It separates from the sulphohydric acid, and
the lime is precipitated in the state of basic phosphate of lime at the
same time forming a basic phosphate of soda. Instead and in place of
one of the two equivalents of sulphuret of sodium I may add an equiva-
lent of sulphate of soda, which will transform tho acid phosphate of lime
into acid phosphate of soda, and into sulphate of lime which pre-
cipitates. The acid phosphate of soda put in the presence of sulphuret
of sodium becomes transformed into basic phosphate of soda. It is this
basic phosphate of soda which the inventor decomposes by the caustic
lime which leaves the soda bare and becomes itself transformed into basic
phosphate of lime.

page_text: The two insoluble residues of basic phosphate of lime are reunited
and treated subsequently with sulphuric acid which again transforms
them into acid phosphate of lime which will serve for fresh operations.
The operations just described are effected either cold or under the
influence of heat in vessels of iron or wood provided with double bottoms
and serpentine pipes, permitting, if thought desirable, of their being
heated by steam. The soda produced is separated by decantation and
concentrated according to the methods now employed.
Although I have described them as used for the production of caustic
soda, these methods are applicable for the production of caustic potash
and its salts.
And having now described the nature of the said Invention and in
what manner the same is to be performed, I declare that I claim,―
The production of caustic soda from sulphuret of sodium, and of
caustic potash from sulphuret of potassium, by means of the two chemical
reactions giving rise to the processes respectively called the dry and wet
process, as above described.
In witness whereof, I, the said Thomas James Smith, have here-
unto set my hand and seal, this Sixteenth day of December One
thousand eight hundred and seventy.