Thann Et Mulhouse, Corp.

Daniel A Hoffner

Pierre Portes

Jean M Trautmann

Jean-Marie C Trautmann

Pigmentary red iron oxide particulates essentially devoid of manganese impurities and ranging in shade from the orange-reds to the purplish reds, are conveniently prepared by (1) calcining, even at higher temperatures, an intimate admixture of (i) a ferrous sulfate hydrate containing contaminating amounts of manganese values, e.g., a by-product stream of ferrous sulfate, and (ii) an alkali metal compound, said admixture comprising from 0.08 to 1 gram-atom of alkali metal per mole of Fe.sub.2 O.sub.3 produced, (2) washing the calcined admixture with water to remove essentially all water-soluble manganese values therefrom, and advantageously (3) drying and (4) grinding the calcined and washed admixture.

Preparation of pigmentary red iron oxides

Pigment grade Fe.sub.2 O.sub.3 is prepared from ferrous sulphate by a roasting process. The ferrous sulphate, partly dehydrated and granulated, is partially converted to the oxide by roasting. After elimination of soluble constituents by washing with water, the oxide is subjected to pigmentary calcination and then crushed and optionally micronized. This process makes it possible to prepare red pigments of excellent quality characterized particularly by pure tints ranging from orange-red to purplish-red. The oil absorptions are especially low. Low toxic impurity concentrations permit the use of these pigments in foodstuffs.

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Thann, France

Daniel A Hoffner