Abstract: An aqueous solution comprising alkali metal hydrosulfite and hydroxide ions in an amount to provide a residual alkalinity of at least 0.25 moles per liter results in the decomposition of thiosulfate ions present and inhibits their formation during storage. These solutions can be used, for example, in the bleaching of mechanical pulp.

Abstract: A process for electrolyzing an aqueous catholyte solution comprising an alkali meal bisulfite to produce an alkali metal hydrosulfite in an electrolytic membrane cell having a cation exchange membrane separating a cathode compartment from an anode compartment, a porous cathode having a face adjacent the membrane, a back opposite, and a porous structure conjoining the face and the back, and a cathode-membrane gap between the porous cathode and the cation exchange membrane. The process comprises directing at least 50 percent of the volume of the aqueous alkali metal bisulfite catholyte through the porous cathode and transverse to the face and back of the cathode, the porous cathode having a ratio of total surface area to the projected surface area of at least about 30:1.High purity solutions of alkali metal hydrosulfites, such as sodium hydrosulfite having concentrations of at least 120 grams per liter, are produced at current densities in the range of 1.0 to 4.5 KA/m.sup.2 and at reduced cell voltages.

Abstract: A process for the electrochemical production of an alkali metal hydrosulfite by the reduction of an alkali metal bisulfite component of a circulated aqueous catholyte solution in an electrolytic membrane cell having a cathode compartment, a porous cathode in the cathode compartment, an anode compartment and a cation exchange membrane separating the cathode compartment from the anode compartment, which comprises passing at least 30 percent by volume of the aqueous catholyte through the pores of the porous cathode in the cathode compartment.High purity solutions of alkali metal hydrosulfites, such as sodium hydrosulfite having concentrations of at least 120 grams per liter, are produced at current densities in the range of 1.0 to 4.5 KA/m.sup.2 and at reduced cell voltages. The thiosulfate impurity concentration is from 0 to about 10 percent by weight of the hydrosulfite.

Abstract: A separator for use in an electrolytic cell between the anode and a cation exchange membrane is provided to prevent the membrane from touching the anode, the separator having a central mesh portion that is hydrophilic and a surrounding peripheral frame portion.

Abstract: Cationic contaminants are removed from an alkali metal chloride brine in a process which comprises contacting the brine with solid particles of a magnesium-containing silicate having a mole ratio of silicon to magnesium of at least about 1:1. The cationic contaminants in the brine adhere to the magnesium-containing silicate particles and the concentration of the cationic contaminants are thereby reduced. A purified brine is obtained by removing the magnesium-containing silicate having cationic contaminants adhering thereto.Elements of Groups VIII, IV, and II can readily be removed from brines used in electrolytic processes such as the production of chlorine and alkali metal hydroxides or alkali metal chlorates.