Tartaric acid is produced by epoxidizing acid calcium maleate with aqueous hydrogen peroxide in the presence of a tungstic acid-containing catalyst to produce sparingly soluble acid calcium cis-epoxysuccinic acid, which is suspended in a solvent medium comprising an organic solvent or a mixture of organic solvent and water and treated with sulphuric acid. Calcium sulphate is formed and separated and the liberated organic acids consisting essentially of epoxysuccinic acid are then hydrolyzed in an aqueous medium to form tartaric acid. The organic solvent may be one in which epoxysuccinic acid is soluble and may be immiscible or miscible with water. If the solvent is imiscible with water the epoxysuccinic acid may be transferred to the aqueous medium in which it is hydrolyzed by liquid-liquid extraction. The epoxysuccinic acid may be crystallized out of the solvent medium and thereafter dissolved in water for the hydrolysis, or, if the organic solvent is miscible with water and the solvent medium comprises water, the organic solvent may be distilled off to leave the epoxysuccinic acid in the aqueous medium in which hydrolysis can be effected. Various organic solvents are disclosed as suitable.
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