Abstract: A method for controlling chlorates in an aqueous alkali metal hydroxide liquor produced by an ion exchange membrane electrolysis is provided, which comprises adding a reducing agent to brine to keep the concentration of chlorates to a specified value or less. The present invention provides an alkali metal hydroxide liquor with low content of chlorates.

Abstract: Disclosed is an electrolysis process which is characterized by carrying out the electrolysis of an aqueous alkali metal halide solution while supplying a cathode liquor into a cathode compartment formed between a cation exchange membrane positioned substantially horizontal and a cathode plate of gas-liquid impermeability, with which the membrane is wetted, then a mixed stream of the cathode liquor and cathode gas being removed from the cathode compartment.Also disclosed is an electrolytic cell which is comprised of an upper anode compartment and a lower cathode compartment partitioned by a cation exchange membrane positioned substantially horizontal, said anode compartment having therein substantially horizontal anodes and an anolyte solution inlet and outlet, and said cathode compartment having a cathode plate with gas-liquid impermeability and a cathode liquor inlet and an outlet of a mixed stream of the cathode liquor and cathode gas.

Abstract: Disclosed is an electrolytic process using a horizontal type cation exchange membrane electrolytic cell in which catholyte liquor is supplied into a cathode compartment with initial linear velocity of at least 8 cm/sec and gas content of at most 0.6 at a catholyte liquor outlet. Also disclosed is an electrolytic cell used for the foregoing process. The invention enables not only conversion of a mercury electrolytic cell to a cation exchange membrane electrolytic cell with low cost, but the long-term and stable operation.

Abstract: Disclosed is a vertical type electrolytic cell partitioned by an ion exchange membrane into an anode compartment and a cathode compartment, the cathode compartment being divided by a non-perforated cathode plate into a cathode gas generation room and a cathode gas separation room. Also disclosed is an electrolytic process using the electrolytic cell wherein the catholyte is circulated between the two rooms as a result of a gas lift effect produced by the cathode gas.

Abstract: An electrolytic process using a horizontal electrolytic cell partitioned by a cation exchange membrane into an anode compartment and a cathode compartment is disclosed which is characterized by supplying into the cathode compartment catholyte liquor at a flow rate satisfying the equation;Y.gtoreq.9 log.sub.10 X+11wherein Y is initial linear velocity (cm/sec) of the catholyte liquor containing no cathode gas or containing cathode gas in an extremely small amount, and X is length (m) of a passageway of the catholyte liquor in the cathode compartment.

Abstract: An electrolytic cell is disclosed comprising an upper anode compartment and a lower cathode compartment partitioned by a cation exchange membrane, in which partitioning spacers are provided on a cathode plate in order to eliminate the troubles owing to non-uniform flow of catholyte liquor, non-uniformity of anode-cathode gap, coarse surface of the cathode plate and the like.

Abstract: Disclosed is a method for preventing a low hydrogen overvoltage cathode from degradation in activity characterized by adding a reducing agent to a cathode compartment of an electrolytic cell which electrolysis an aqueous alkali metal halide solution. According to the invention, no degradation takes place even after repeated shutdown of operation.

Abstract: Disclosed is a vertical and monopolar box type electrolytic cell for the electrolysis of an aqueous alkali metal chloride solution providing a cation exchange membrane as a separator between anodes and cathodes, which comprises an anode compartment having at least one anode solution inlet, at least one anode solution outlet and at least one anode gas outlet, respectively, and a cathode compartment having at least one cathode solution inlet, at least one cathode solution outlet and at least one cathode gas outlet, respectively, said anode solution outlet is positioned in such a manner that the ratio of height of anode solution level to that of cathode solution level is more than one and the product of a difference in height between the cathode solution level and the anode solution level and an apparent specific gravity of the anode solution is less than the sum total of an anode compartment inside pressure in the positive numerical value of a given negative pressure value and a cathode compartment inside press

Abstract: A finger type electrolytic cell providing a cation exchange membrane for electrolysing an aqueous alkali metal chloride solution is disclosed. The cell is comprised of a cell top cover whose surface is coated with a chlorine-resistant material containing no polymetallic ions, and further a blanket which is made of or covered with said material, so that no hindrance resulting from polymetallic ions occurs.

Abstract: Disclosed is an electrolytic process of an aqueous alkali metal chloride solution using a cation exchange membrane as a separator of an electrolytic cell, which comprises effecting the electrolysis while utilizing impact resilience of springs positioned at anodes and exerting positive pressure on a cathode compartment of the cell. Not only is stable operation at low cell voltage for a prolonged period of time enabled, but also high purity alkali metal hydroxide containing a reduced amount of sodium chloride is produced.

Abstract: A separator electrolytic cell is disclosed which comprises a first electrode compartment surrounded with a releasable wall plate and a glove-shaped finger and a second electrode compartment surrounded with remaining cell walls, a cell top cover and the glove-shaped finger. A sheet-like separator is immediately installed to the cell without any peculiar processing and the cell facilitates assembly and disassembly and provides tight sealing.

Abstract: An electrolytic process is provided for the electrolysis of an aqueous alkali metal halide solution, which comprises effecting the electrolysis in a cell being separated by a cation exchange membrane into an anode compartment and a cathode compartment, wherein washing liquid is supplied into a liquid seal pot provided at a cathode gas outlet of a cathode compartment and cathode gas evolved from the cell is contacted with the washing liquid in the liquid seal pot.

Abstract: A membrane for electrolyzing an alkali metal chloride solution using a finger type electrolytic cell equipped with a cation exchange membrane, wherein areas of said membrane not facing the effective electrolytic surface of the anode have a higher stiffness and a lower anion permeability than the areas of said membrane facing the effective electrolytic surface of the anode, thus reducing the alkali metal chloride content in the alkali metal hydroxide aqueous solution obtained from the cathodic chamber.

Abstract: A cylindrical cation exchange membrane is described for use in electrolysis of an aqueous alkali metal chloride solution in a finger type electrolytic cell, wherein the equivalent weight of the area not facing the effective electrolytic surface of anode is greater than the equivalent weight of the areas facing the effective electrolytic surface, thus permitting a reduction of the alkali metal chloride content of an effluent from a cathodic chamber.

Abstract: Process for the electrolysis of an aqueous alkali metal chloride solution using a cation exchange membrane, wherein the gas-liquid interface, at which halogen gas is separated, is maintained larger than the sum total of the cross section area of the unit anode chambers opposing to cathodes, and further, higher than the upper end of the cation exchange membrane. The invention has numerous advantages including substantial absence of halogen gas, operation at a low voltage, a high pure product, simplification of operation control and the like.

Abstract: Apparatus for the electrolysis of an aqueous alkali metal chloride solution using a cation exchange membrane, wherein the apparatus is designed so that gas-liquid interface, at which halogen gas is separated, is maintained larger than the sum total of the cross section area of the unit anode chambers opposing to cathodes, and further, higher than the upper end of the cation exchange membrane. The invention has numerous advantages including substantial absence of halogen gas, operation at a low voltage, a high pure product, simplification of operation control and the like.

Abstract: Method and apparatus of installation of a membrane to a finger type electrolytic cell are provided, which comprise covering the horizontal surfaces of a cathode not opposing an anode with a membrane installation frame having a collar, positioning the membrane substantially parallel to the vertical surfaces of the cathode, and installing and securing the membrane to the collar by clipping. Not only is operation efficiency for the membrane installation to the electrolytic cell markedly improved, but also, in the case of an ion exchange membrane, an alkali metal hydroxide liquor hardly containing an alkali metal chloride is produced. According to the invention, a conventional asbestos diaphragm finger type electrolytic cell is advantageously converted to an ion exchange membrane electrolytic cell.

Abstract: Method for electrolysis of an aqueous alkali metal chloride solution is provided, wherein an aqueous alkali metal chloride solution is electrolyzed by maintaining a temperature of an aqueous alkali metal hydroxide liquor in a cathode compartment lower than that of the aqueous alkali metal chloride solution in an anode compartment, using an electrolytic cell which is separated by a cation exchange membrane into the anode compartment and the cathode compartment. Not only is current efficiency improved without adverse effects on voltage, thus enabling a long period operation with low electric power consumption, but also high purity alkali metal hydroxide containing a reduced amount of chloride ion is produced.