Abstract: An electrodialysis method using a bipolar membrane (BP) for regenerating acids, wherein a series of base (B), acid (A) and salt (S) compartments are provided between a positive electrode (anode) and a negative electrode (cathode), said compartments being defined by a series of membranes: cationic, bipolar, anionic, cationic, bipolar and so forth, and a solution being circulated through each compartment. An additional anionic membrane (10) is applied to the anionic side (11) of the bipolar membrane (BP) with no discernible gap therebetween so that contamination of the acid compartment by cations is reduced.

Abstract: This invention relates to improvement to a process for the preparation of mercaptoalcohols containing, more particularly, up to 24 carbon atoms and, preferably, more than 3 carbon atoms, by reaction of the corresponding vicinal epoxides with hydrogen sulphide.The process comprises incorporating into the reaction mixture a catalyst comprising a guanidine and/or of organic derivatives of a guanidine, and/or of guanidine salts, in particular of guanidine salts. The catalyst can be either in liquid and/or solid form, depending on the nature of the catalyst and its solubility in the reaction mixture, or fixed and/or impregnated into various solid materials. The materials can be organic in nature such as neutral and/or basic polymer resins, polymers or copolymers, or can be inorganic in nature such as alumninas, silicas, aluminosilicates, zeolites, active charcoals, oxides and/or metal salts.

Abstract: Process for the synthesis of a mercaptan from an olefin, by the action of hydrogen sulphide thereon, in the presence of a catalyst comprising a cation exchange resin, characterized in that this resin is dry and that the reaction is effected at a temperature ranging between 45.degree. and 75.degree. C.

Abstract: Improvement in the photoinitiated synthesis of mercaptans, in which an ethylenic compound is treated with hydrogen sulphide, preferably under pressure, in the presence of ultraviolet radiation and a photoinitiator involves the use of a xanthenic compound, possibly substituted, as the initiator. Preferably, the xanthenic compounds is employed in conjunction with an organic compound of an element of Group V A of the Periodic Classification of the Elements.