Manufacture of red hydrous ferric oxide

Claim 1

A PROCESS FOR THE PRODUCTION OF RED TO PURPLE FERRIC OXIDE PIGMENTS FROM METALLIC IRON AS THE PRIMARY SOURCE WHICH COMPRISES DISSOLVING AN IRON SALT IN WATER, INTRODUCING OXYGEN INTO THE RESULTING AQUEOUS IRON SALT SOLUTION HAVING AN ION CONCENTRATION ON ONE SIDE OF NEUTRALITY, UNTIL OXIDATION SUBSTANTIALLY CEASES, CHANGING THE ION CONCENTRATION OF THE REACTION MASS OF THE OTHER SIDE OF NEUA TRALITY, AGAIN INTRODUCING OXYGEN INTO THE REACTION MASS UNTIL OXIDATION SUBSTANTIALLY CEASES, AGAIN CHANGING THE ION CONCENTRATION OF THE REACTION MASS BACK TO A PH VALUE ON THE ORIGINAL SIDE OF NEUTRALITY, AGAIN INTRODUCING OXYGEN INTO THE REACTION MASS UNTIL OXIDATION SUBSTANTIALLY CEASES, THE ALTERATION OF THE ION CONCENTRATION BEING EFFECTED ON THE ONE HANB BY THE ADDITION OF AN ALKALI AND ON THE OTHER HAND BY THE ADDITION OF A SOLUBLE IRON SALT, THEREBY FORMING A HYDRATED FERRIC OXIDE SEED IN THE REACTON SOLUTION, CONTACTING THE RESULTING SEED IN AN IRON SALT SOLUTION WITH METALLIC IRON AND INTRODUCING OXYGEN INTO THE SOLUTION DURING SAID CONTACT WHEREBY SAID IRON IS OXIDIZED AND A RED IRON OXIDE IS OBTAINED, DISCONTINUING THE OXIDATION WHEN THE DESIRED SHADE OF RED TO PURPLE IS OBTAINED AND SEPARATING SAID IRON OXIDE FROM THE LIQUID MASS AND ANY REMAINING METAL, THEREBY OBTAINING AN IRON OXIDE OF THE SAID RANGE OF COLOR OF PIGMENT GRADE.