Abstract: Highly-coercive isometric iron oxide useful in magnetic toners for electrostatic photo-copying processes or for magnetic printers is produced by(a) subjecting Fe.sub.3 O.sub.4 pigment produced in a wet process to oxidation and(b) subsequently reducing the oxidized pigment from (a) to produce highly-coercive Fe.sub.3 O.sub.4 pigment.

Abstract: Needle shaped alloy pigment powders consisting essentially of iron, silicon and aluminum, with up to 1.0% by weight of chromium and one or both of cobalt or tin in amounts from 0.3 to 3% by weight of cobalt and from 0.1 to 5.0% by weight of tin, based in each case on the iron, are useful as the magnetic powders used in magnetic recording devices.

Abstract: Magnetic iron oxide pigments useful in magnetic signal recordings having a dependence of coercivity on temperature in the temperature range of from 76K to 298K of less than 0.13 kA/mK and having a coercivity on powder compressed to 0.9 g/cm.sup.3 of greater than 51 kA/m are prepared by coating a magnetic iron oxide core material having the composition FeO.sub.x where x is a number from 1.33 to 1.5 in a first step with a compound containing divalent and trivalent iron having a ratio of Fe(III): Fe(II) from 0.01 to less than 2, and then in a second step coating the pre-coated core with a second coating of a cobalt compound.

Abstract: Magnetic iron oxide pigments having a monomolecular coating of a cobalt compound useful in magnetic signal recordings having a dependence of coercivity on temperature in the temperature range of from 76 K to 298 K of less than 0.13 kA/mK and having a coercivity on powder compressed to 0.9 g/cm.sup.3 of greater than 51 kA/m are prepared applying a preliminary coating of Fe.sub.3 O.sub.4 or a bertholloid compound to a magnetic iron oxide core material having the composition FeO.sub.x where x is a number from 1.33 to 1.55 and then covering the preliminary coating with a cobalt compound.

Abstract: In a rotary tubular kiln for carrying out gas-solids reactions, comprising an indirectly heated, rotatable reaction tube with inner baffles which is provided with charging and removing devices for solid and gas inlet and outlet lines, the improvement which comprises forming the baffles as a central tube which is sealed on both sides and runs along the total length of the kiln, and a spiral which is tightly connected to the central tube and also to the outer rotatable tube. Lifting blades are uniformly distributed along the inner periphery of the rotatable tube. The kiln is suitable for carrying out oxidation, reduction, chlorination, roasting, decomposition, catalytic, annealling and/or cooling processes, e.g. the conversion of hematite to magnetite or goethite to iron.

Abstract: Sensitive magnetic pigment particles enclosed in about 0.1 to 5% by weight of a polymeric material thereby preserving the pigment magnetic properties. Advantageously, the polymer, which serves as a packing, is at least one member selected from the group consisting of polycarbonates, polyacrylates, polymethacrylates, polyesters, polyethers, polyurethanes, polyvinyl compounds, polyvinylidene compounds and cellulose compounds. These are compatible with the matrices used to make magnetic tapes.

Abstract: In a rotary tubular kiln for carrying out gas-solids reactions, comprising an indirectly heated, rotatable reaction tube with inner baffles which is provided with charging and removing devices for solid and gas inlet and outlet lines, the improvement which comprises forming the baffles as a central tube which is sealed on both sides and runs along the total length of the kiln, and a spiral which is tightly connected to the central tube and also to the outer rotatable tube. Lifting blades are uniformly distributed along the inner periphery of the rotatable tube. The kiln is suitable for carrying out oxidation, reduction, chlorination, roasting, decomposition, catalytic, annealing and/or cooling processes, e.g. the conversion of hematite to magnetite or goethite to iron.

Abstract: An inorganically after-treated TiO.sub.2 pigment with a coating of hydrophobicizing and hydrophilicizing organic substances, which pigment comprises more than about 95% by weight of TiO.sub.2, shows a loss on annealing of less than about 0.8% (after subtraction of the carbon content) and has a grindometer value smaller than about 30, corresponding to a value of more than about 5.6 on the Hegman scale, is produced by micronizing a mixture of an inorganically after-treated TiO.sub.2 pigment, an untreated TiO.sub.2 pigment and hydrophobicizing and hydrophilicizing organic substances, the after-treated pigment being employed in about 1 to 40% by weight of total TiO.sub.2 pigment and the hydrophobicing and hydrophilicizing substances being employed in about 0.3 to 5% by weight of TiO.sub.2 pigment. The pigments are readily dispersible which simplifies their use in pigmenting lacquers, plastics and paper.

Abstract: In an aqueous fluid dispersible filler or pigment suspension containing a dispersion aid, the improvement which comprises employing as the dispersion aid about 0.01 to 1% by weight, based on solids, of a phosphonocarboxylic acid or a salt thereof. The pigment may be TiO.sub.2 and be present in from 30 to 80% concentration. The dispersion aid may be phosphonobutane-1, 2,4-tricarboxylic acid or a salt, and an amine or alkanolamine may also be present.

Abstract: Process for producing ferromagnetic iron oxides whereby a solution of a ferrous salt is oxidized in the presence of .alpha.-FeO(OH) seed, a basic precipitant, and phosphoric acid or a water soluble salt thereof to form .alpha.-FeO(OH), which can be dehydrated, optionally tempered, reduced and re-oxidized to needle-shaped .gamma.-Fe.sub.2 O.sub.3. The resulting product has high coercive force values which make it especially useful for magnetic impulse recording and reproduction.