Abstract: Process for the preparation of a purified solution of phosphoric acid, which may be partially neutralized, from wet process phosphoric acid, by liquid-liquid extraction by means of a substantially water-immiscible organic solvent. The phosphoric acid is treated in the selected solvent, preferably isobutyl alcohol, in the presence of sulphuric acid, by means of an aqueous solution containing phosphate ions and calcium ions in solution, the sulphate ions are precipitated in the form of calcium sulphate, and suspended in said aqueous solution which is separated from the phosphoric solution. The process is advantageously employed for the continuous preparation of concentrated solutions of monosodium phosphate.