Abstract: In accordance with the present invention, there is now provided a process for the production an anhydrous magnesium chloride-containing melt or electrolyte containing very low levels of MgO, typically less than 0.2% by weight MgO, directly from hydrated magnesium chloride feeds. More specifically, the process comprises the steps of a) feeding hydrated magnesium chloride in a furnace containing molten electrolyte from a magnesium electrolysis cell to produce a melt, the temperature in the furnace being maintained between 450.degree. and 65.degree. C.; b) simultaneously injecting an anhydrous hydrogen chloride-containing gas into the melt in an amount below the stoichiometric requirement of 2 moles of HCl per mole of magnesium chloride produced from hydrated magnesium chloride, and agitating the melt to keep any magnesium oxide in suspension in them melt, to dehydrate the magnesium chloride and react with the MgO in the melt so that the melt contains not more than 0.

Abstract: This invention relates a method for the selective removal of alkali metal salts of sulphate (SO.sub.4.sup.2-), and thiosulphate (S.sub.2 O.sub.3.sup.2-) from hydrogen sulphide (H.sub.2 S) scrubber solutions of the liquid redox type using an electrodialysis system. In the process of this invention the H.sub.2 S scrubber solution is directed to the diluting compartments within an electrodialysis stack, while a collecting solution with a minimal initial salt content is directed to the concentrating compartments. With the application of a direct current a portion of the alkali metal salts of sulphate and thiosulphate present in the scrubber solution are transported through ion selective membranes into the collecting solution. Essentially all of the metal organic chelate reagents and carbonate ions initially present in the scrubber solution are retained in the desalted solution and can be recycled to the H.sub.2 S scrubbing process.