Method of making iron oxide pigment

Claim 1

A METHOD FOR THE PRODUCTION OF HYDROHEMATITIC IRON OXIDE PIGMENTS HAVING A HEXAGONAL RHOMBOHEDRAL CRYSTAL STRUCTURE CONTAINING NOT MORE THAN 8% CHEMICALLY COMBINED WATER, IN THE FORM OF DRY POWDER OF HUES VARYING FROM ORANGE TO RED COMPRISING, FORMING AN AQUEOUS MASS CONTAINING (1) BROWN PRECIPITATED FERRIC HYDROXIDE AND, IN SOLUTION, BOTH (2) A FERROUS SALT AND (3) A CATALYST WHICH IS AN IONIZABLE COMPOUND OF A METAL SELECTED FROM THE GROUP CONSISTING OF ZINC AND COPPER, SAID CATALYST BEING PRESENT IN A RATIO OF AT LEAST ONE MOL TO 10 MOLS OF FERROUS SALT PRESENT MAINTAINING THE MASS AT A TEMPERATURE OF AT LEAST 65* C. UNTIL A HYDRO-HEMATITIC IRON OXIDE OF A HUE WITHIN THE SAID COLOR RANGE IS OBTAINED, SEPARATING THE SAID OXIDE FROM THE LIQUID OF THE MASS CONTAINING THE CATALYST AND REMOVING THE FREE SURFACE MOISTURE FROM THE SAID OXIDE BY DRYING, THEREBY DIRECTLY PROVIDING A PIGMENT OF THE INDICATED COLOR WITHOUT RESORT TO ROASTING.

Claim 2

A METHOD FOR THE PRODUCTION OF HYDROHEMATITIC IRON OXIDE PIGMENTS HAVING A HEXAGONAL RHOMBOHEDRAL CRYSTAL STRUCTURE CONTAINING NOT MORE THAN 8% CHEMICALLY COMBINED WATER, IN THE FORM OF DRY POWDER OF HUES VARYING FROM ORANGE TO RED COMPRISING, FORMING AN AQUEOUS MASS CONTAINING (1) BROWN PRECIPITATED FERRIC HYDROXIDE AND, IN SOLUTION, BOTH (2) A FERROUS SALT AND (3) A CATALYST WHICH IS AN IONIZABLE COMPOUND OF A METAL SELECTED FROM THE GROUP CONSISTING OF ZINC AND COPPER, SAID CATALYST BEING PRESENT IN A RATIO OF AT LEAST ONE MOL TO 10 MOLS OF FERROUS SALT PRESENT MAINTAINING THE MASS AT A TEMPERATURE OF AT LEAST 65* C. UNTIL A HYDRO-HEMATITIC IRON OXIDE OF A HUE WITHIN THE SAID COLOR RANGE IS OBTAINED, SEPARATING THE SAID OXIDE FROM THE LIQUID OF THE MASS CONTAINING THE CATALYST AND REMOVING THE FREE SURFACE MOISTURE FROM THE SAID OXIDE BY DRYING, THEREBY DIRECTLY PROVIDING A PIGMENT OF THE INDICATED COLOR WITHOUT RESORT TO ROASTING.