AN IMPROVED PROCESS FOR OBTAINING CAUSTIC SODA for AND CHLORINE BY THE DECOMPOSITION OF SALINE SOLUTIONS
Year: 1882

page_text: LETTERS PATENT to John Berger Spence of Lombard Street in the City of
London and Alexander Watt of Charlton in the County of Kent, Chemist,
invention of "AN IMPROVED PROCESS FOR OBTAINING CAUSTIC SODA
for en
PROVISIONAL SPECIFICATION left by the said John Berger Spence and
Alexander Watt at the Office of the Commissioners of Patents on the
4th April 1882.
JOHN BERGER SPENCE of Lombard Street in the City of London and ALEXANDER
WATT of Charlton in the County of Kent, Chemist,
"AN IMPROVED PROCESS
FOR OBTAINING CAUSTIC SODA AND CHLORINE BY THE DECOMPOSITION OF SALINE
SOLUTIONS
"
The object of this invention is to produce caustic soda, and chlorine by the
electro-chemical decomposition of solutions of common salt (chloride of sodium) in
a more satisfactory and economical manner than heretofore.
Various attempts have been made to decompose saline solutions by means of
electric currents for the purpose of separating their component parts, but up to the
present time the proposed methods or processes have been commercially
unsuccessful, owing to the difficulty in obtaining electricity at a sufficiently cheap
rate.
According to the present invention the electrical power is obtained at a
comparatively nominal cost by utilizing the hydrogen gas evolved during the
decomposition, in ordinary gas-engines instead of coal gas, which has hitherto been
employed; and since the evolved hydrogen may be considered a waste product in
the electro-decomposition of saline solutions, its employment as a motive force for
gas engines employed as motors for dynamo-electric machines and other electric
generators dependent upon power, is of the utmost importance in economizing the
cost of electricity in electro-chemical decompositions.

page_text: In carrying out our Invention, we place concentrated solutions of common salt
previously heated to about 120 degrees Fahrenheit in large tanks or chambers divided
into compartments by suitable porous partitions which may be made of the clay
usually employed for making "porous cells" and battery partitions, plaster of Paris,
or other porous material not acted upon by chlorine or caustic soda. At the bottom
of each compartment is placed a quantity of broken fragments of ordinary gas-
carbon, piled up in a heap in such a manner that all the fragments shall be in
actual contact with each other; and with a carbon electrode in connection with a
dynamo-electric machine, or other source of electric power. These carbon electrodes
should be of sufficient thickness to convey a powerful current of electricity, and,
to render them less liable to injury by breaking. a stout coating of copper is
deposited upon them by the ordinary electro-type process. The upper part of the
tank, or decomposition chamber, is closed by a lid, or cover, securely luted to
prevent escape of the generated gases. The lid or cover is provided with pipes to
carry off the liberated gases to proper receptacles. The chlorine gas generated
may be passed into a chamber containing fresh lime which thus becomes converted
into chloride of lime, or bleaching powder. The hydrogen gas evolved during the
decomposition may be collected in an ordinary gas-holder or gasometer, to be used
in gas engines employed to drive dynamo-electric machines or other suitable
apparatus employed to generate the electricity to be used in the decomposition of
other charges of saline solutions. When the hydrogen gas evolved during the
process of decomposing solutions of common salt for the production of caustic
soda is in excess of that required for working gas engines as motors for dynamo-
electric machines, the excess may be employed for heating evaporating pans to
concentrate the saline solutions which have been subjected to the electrolytic action
aforesaid.
The decomposition chamber or tank is furnished with a feeder at its upper
surface, through which fresh charges of saline solutions are conveyed to the several
compartments of the tank, and the decomposed solution is drawn off by means of
taps or plugs fitted to the lower ends of the tank.
The decomposition tank may be made of slate, wood, lined with cement, or
concrete lined with cement..
It will thus be seen that by the use of this process, the power requisite to carry
on the process may be derived from the carrying out of the process itself.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Berger Spence and Alexander Watt in the Great Seal Patent
Office on the 4th October 1882.
JOHN BERGER SPENCE of Lombard Street in the City of London and ALEXANDER
WATT of Charlton in the County of Kent Chemist "AN IMPROVED PROCESS
FOR OBTAINING CAUSTIC SODA AND CHLORINE BY THE DECOMPOSITION OF SALINE
SOLUTIONS
"
The object of this Invention is to produce caustic soda and chlorine by the electro
chemical decomposition of solutions of common salt (chloride of sodium) in a more
satisfactory and economical manner than heretofore.
The decomposition of saline solutions by means of electric currents for the
purpose of separating their component parts is well known in theory to Chemists
but up to the present time the methods or processes employed have been
commercially unsuccessful owing to the difficulty of obtaining electricity at a
sufficiently cheap rate.
According to the present Invention the electrical power is obtained at a
comparatively nominal cost by utilizing the hydrogen gas evolved during the
decomposition, as a motor for driving explosive or gas engines. As the hydrogen
evolved in the electro chemical decomposition of saline solutions may be considered
as a waste product its employment to drive Gas engines for working dynamo
electric machines and other electric generators dependent upon power, will greatly
economise the cost of producing electricity for electro chemical decompositious.
In carrying out our Invention we place a concentrated solution of common salt
previously heated to about 120° Fahrenheit in a large tank or chamber which is
divided into two or more compartiments as desired by suitable porous partitions.
These partitions may be made of the clay usually employed for making "porous
cells" and battery partitions, Plaster of Paris or other porous material not acted
upon by chlorine or caustic soda. At the bottom of each compartment we place a
number of lumps of gas carbon or other suitable conducting material which are so
arranged as to ensure contact with each other and with a carbon electrode in
connection with a dynamo electric machine or other source of electric power.
These carbon electrodes may be made in the same manner as "carbons" for electric
lamps are prepared but they should be of sufficient thickness to convey a powerful
current of electricity and also to render them less liable to breakage. These
electrodes are inserted through the walls of the tank or chamber and in order to
protect their outer ends a stout coating of copper is deposited thereon by the
ordinary electrotype process. Suitable binding screws or clamps are provided
by means of which the wires from the generator are connected to the electrodes..
Each compartment of the tank or decomposition chamber is closed by a lid or
covered securely luted to prevent the escape of the generated gases. Each lid or
cover is provided with a pipe to carry off to proper receptacles the gas liberated in
each compartment. As is well known to Chemists the action of electricity on the
saline solution is to produce at the positive pole chlorine gas and at the negative
pole hydrogen gas; a solution of caustic soda being formed in the compartment
containing the negative electrode.-The chlorine gas generated we pass into a
chamber containing fresh lime with which the gas combines, converting it into
chloride of lime or bleaching powder. The lime we prefer to place on tiers of
trays or shelves arranged in the chamber so that the combustion may be effected
more readily.
Instead of employing the chlorine gas to form chloride of Lime as above
mentioned it may be collected in a suitable receptacle for use in any other desired

page_text: manner.
The hydrogen gas evolved during the decomposition we collect in a gas
holder to be used as the motive force in the gas engines employed to drive the
dynamo electric machines or other suitable apparatus for generating the electricity
required for the decomposition of the charges of saline solution-When the
hydrogen gas evolved during the process of decomposing solutions of common salt
for the production of caustic Soda is in excess of that required for driving the gas
engines to work the dynamo electric machines, the excess may be employed for
heating evaporating pans to concentrate the saline solutions which are to be
subjected to the electrolytic action aforesaid; or it may be employed to drive gas
engines to work pumps for filling and emptying the tanks.-The caustic soda
solution we from time to time remove and evaporate and the caustic soda when
dried we pack in casks or other receptacles for the market.
The decomposition chamber or tank may if desired be furnished with a feed pipe
at its upper part through which fresh charges of saline solution may be conveyed
to the several compartments of the tank and the waste liquor may be drawn off by
means of taps placed near the bottom of the tank.
The tank or chamber will of course be made of some material which is not
affected by electricity or by the products of the decomposition such as slate, wood
lined with cement, or concrete lined with cement.
In commencing to work the process the Gas Engine may be supplied with
ordinary coal gas until sufficient hydrogen gas for continuing the work has been
generated when the coal gas will be turned off and the engine will be worked by
the hydrogen gas. It will thus be seen that by the use of this process the power
requisite to carry on the work will be derived from the process itself.
"
and
Having now described the nature of our Invention of "An improved process for
obtaining caustic soda and chlorine by the decomposition of saline solutions
explained the manner of carrying the same into effect we wish it to be understood
that we claim
Obtaining Caustic Soda and Chlorine from the decomposition of saline solutions
produced by electricity such electricity being generated by the employment of the
hydrogen gas evolved during such manufacture as herein described.
In witness whereof we the said John Berger Spence and Alexander Watt have
hereunto set our hands and seals the fourth day of October in the year
of our Lord One thousand eight hundred and eighty two.