Phosphorous acid is made by a continuous recycling process from a mixture of phosphorous and hydrochloric acids, comprising:(i) continuously recycling the mixture in a loop apparatus;(ii) adding water to and passing phosphorus trichloride into said recycling mixture so as to generate a condition of turbulent flow at the point of contact of the phosphorus trichloride and the recycling mixture, whereby a reaction product, comprising an aqueous solution of phosphorous and hydrochloric acids as a continuous liquid phase and gaseous hydrogen chloride as gas bubbles of disperse phase, is produced;(iii) separating said gaseous hydrogen chloride;(iv) cooling said reaction product; and(v) recycling at least a portion of said reaction product and repeating steps (ii), (iii) and (iv) thereon to produce a more highly concentrated solution of phosphorus acid.