Method of pickling iron and recovering pickling agent

Claim 1

IN A PROCESS FOR PICKLING FERROUS METAL INCLUDING THE STEPS OF IMMERSING SAID METAL IN AN AQUEOUS PICKLING BATH OF AMMONIUM ACID SULPHATE TO YIELD FERROUS AMMONIUM SULPHATE IN AQUEOUS SOLUTION, THEN BY A PROCESS INCLUDING THE STEPS OF OXIDATION AND RAISING THE PH TO AT LEAST 7 WITH AN AMMONIA-CONTAINING FLUID, THEREBY CONVERTING SAID FERROUS AMMONIUM SULPHATE TO OXIDE OF IRON AND DI-AMMONIUM SULPHATE, RECOVERING DI-AMMONIUM SULPHATE FROM THE RESULTING SOLUTION,HEATING SAID DI-AMMONIUM SULPHATE TO CONVERT IT TO AMMONIUM ACID SULPHATE AND RETURNING SAID AMMONIUM ACID SULPHATE TO THE PICKLING OPERAION, THE IMPROVEMENT WHICH COMPRISES SEPARATING FERROUS AMMONIUM SUPLHATE FROM THE SPENT AQUEOUS PICKLING SOLUTION CONTAINING SAID FERROUS AMMONIUM SULPHATE AND ANY UNREACTED AMMONIUM ACID SULPHATE, AND SUBJECTING A WATER SOLUTION OF THE FERROUS AMMONIUM SULPHATE THIS RECOVERED TO SAID PROCESS INCLUDING THE STEPS OF OXIDATION AND RAISING THE PH TO AT LEAST 7 AND THE STEPS FOLLOWING SAID LATTER PROCESS AS AFORESAID.