Abstract: In a process for the electrolysis of an aqueous sodium chloride solution comprising, in combination, a diaphragm process and a cation exchange membrane process, the sodium chloride obtained from the diaphragm process is dissolved in the weak saline solution obtained from the cation exchange membrane process to obtain a saline solution, which, in turn, is supplied to the anode chamber of the diaphragm process. By the present process, there can be obtained sodium hydroxide of which the impurities content is extremely low, with high efficiency.

Abstract: High purity aqueous alkali hydroxide solutions containing predetermined, low concentrations of alkali metal halide are obtained in the anode compartment of an electrolytic cell using a cationic ion exchange membrane by conducting the electrolysis under controlled conditions such that the difference between the concentration of alkali metal halide in the anode compartment and the limiting concentration of alkali metal halide in the anode compartment is within a defined range.

Abstract: In a system for the electrolysis of sodium chloride in an electrolytic cell divided by a cation exchange membrane into the anode and cathode chambers, hydrogen chloride gas is synthesized from the chlorine gas and the hydrogen gas generated in said electrolytic cell, the hydrogen chloride gas synthesized is directly absorbed in the aqueous sodium chloride solution fed into the anode chamber to neutralize the hydroxyl ions in the anolyte migrated from the cathode chamber and the reaction heat as well as the absorption heat of the hydrogen chloride gas are also utilized for concentration of the dilute aqueous sodium chloride solution and/or the aqueous sodium hydroxide solution produced in the cathode chamber.

Abstract: In a process for electrolysis of sodium chloride in an electrolytic cell divided into the anode chamber and the cathode chamber by a cation exchange membrane, well brine is used as the starting material for the electrolysis and the dilute aqueous sodium chloride solution formed as the result of the electrolysis is subjected to concentration for re-use as the starting material.

Abstract: A sodium chloride feed solution containing an iron cyanide complex is subjected to purification to reduce the content of iron cyanide complex to not more than 0.5 ppm before it is fed as anolyte into an ion-exchange membrane electrolytic cell. The iron cyanide complex is preferably converted by oxidative decomposition to iron ions for removal. By use of such a purified sodium chloride as starting material, electrolysis of sodium chloride using an ion-exchange membrane can be performed for a long term at a constant electrolysis voltage.

Abstract: An aqueous sodium chloride solution for use in production of caustic soda in an electrolytic cell having a cation exchange membrane is purified by adding to said solution a chemical reagent for precipitation separation of impurities remove silica through co-precipitation with a slurry of the precipitates of impurities which are circulated through said solution.

Abstract: A method and apparatus in which the effects in multiple effect evaporation systems are separated into successive stages and the vapors in the stages of one effect are utilized as a heat source for the liquid in stages of a subsequent effect.

Abstract: A bipolar system electrolytic cell having a partition wall made of explosion-bonded titanium plate and iron plate which is electrically connected to anode of titanium substrate at its titanium side and to cathode of iron at its iron side, space is preferably given between anode and the partition wall and also between cathode and the partition wall. An assembly having a number of such unit cells arranged in series is useful for electrolysis of sodium chloride which can be performed under a low voltage per unit cell.

Abstract: In an electrolytic cell having cation exchange membrane as diaphragm to partition said cell into cathode and anode chambers, electrolysis of an electrolyte aqueous solution is conducted while generating gas from anode by keeping the inner pressure in cathode chamber higher than that in anode chamber. Some disadvantages caused in the case of electrolyzing an aqueous alkali metal halide solution to form alkali metal hydroxide in cathode chamber are overcome by adjusting the anolyte at pH <3.5. The electrolytic cell preferably employable for the present process is also disclosed.

Abstract: In carrying out electrolysis of alkali halide in an electrolytic cell having anode and cathode chambers separated by a cation exchange membrane by feeding an aqueous alkali halide solution into the anode chamber to produce halogen gas in the anode chamber and caustic alkali and hydrogen gas in the cathode chamber, the electrolytic cell is pressurized at higher than atmospheric pressure to obtain various improved results.

Abstract: Heated substances, e.g. electrolytes or gases from electrodes, formed during electrolysis of an alkali halide in an electrolytic cell using a cation exchange membrane to separate anode and cathode chambers are used effectively as heat source for heating an aqueous caustic alkali solution to be concentrated in an evaporator.

Abstract: An isocyanate prepolymer represented by the formula ##STR1## wherein n is an integer of 1 to 6, R', R" and R'", which may be the same or different, each represents a divalent aliphatic, araliphatic, aromatic or acyclic group which may contain a ##STR2## bond, and R" and R'" may contain a ##STR3## bond, and a process for producing the same.

Abstract: A solventless polyurethane coating composition having a low viscosity suitable for coating, which comprises (a) an aliphatic or alicyclic polyisocyanate containing at least 3 isocyanate groups, (b) at least 1/3 equivalent, based on the isocyanate groups, of a monohydric alcohol, and (c) a low-molecular-weight polyhydric alcohol having at least 3 active hydrogen atoms. The composition provides coatings having superior properties such as good hardness, weatherability and intimate adhesion to a substrate.

Abstract: A solid solution of a noble metal oxide, titanium oxide and zirconium oxide, containing 1 to 50 mol % of titanium oxide and zirconium oxide as the total content, is coated on an anti-corrosive substrate, e.g. titanium metal to give an electrode which is excellent in low oxygen content in chlorine gas, low electrode consumption and low chlorine overvoltage when it is used as anode for electrolysis of an aqueous sodium chloride solution.

Abstract: A process for precipitating a crystalline diamine dicarboxylate which comprises dissolving the corresponding dicarboxylic acid in the aqueous liquid containing diamine dicarboxylate and adding the sufficient amount of the corresponding diamine to precipitate the desired product by neutralization.