Abstract: The disclosure describes the recovery of sulfuric acid from industrial liquors containing the same. A selective liquid-liquid extraction of said liquors is carried out under conditions producing an organic phase containing the sulfuric acid and an aqueous phase eventually containing impurities. The organic phase is treated with a base, such as gaseous NH.sub.3, in order to separate the sulfuric acid. This process is simple, non-polluting, and requires little energy.

Abstract: The recovery of substantially pure magnesium and/or nickel sulphite which is present in a solid starting meterial. The latter is treated with gaseous SO.sub.2 in water, the solution obtained is treated by a liquid-liquid extraction, to give an aqueous phase and an organic phase and the magnesium and/or nickel sulphite is recovered from the aqueous phase. With this process, it is possible to obtain a magnesium salt of high purity.

Abstract: Lithium carbonate is derived from a calcined lithium-bearing silicate in a continuous cyclic process in which the silicate is decomposed in aqueous medium with sodium carbonate at a selected temperature and pressure, the resulting slurry is cooled and leached with carbon dioxide, and the resulting lithium bicarbonate-bearing soluton is heated to derive lithium carbonate and a mother liquor, which is recycled to the decomposition step. The amount of aqueous liquid used in the decomposition step is reduced to a minimum and the leaching accomplished without further dilution. This results in contamination of the recycled mother liquor with bicarbonate ions, which normally act to inhibit a high yield of lithium carbonate. The process conditions are controlled to reduce this inhibiting effect. Preferably, this control is effected by selecting a relatively low reaction temperature accompanied by neutralizing the mother liquor.