Clean color shade, yellow-tinged red iron oxide pigments, and a process for their manufacture, and their use

A construction industry material dyed with a clean color shade, yellow-tinged red iron oxide pigment having a loss on ignition of less than about 1% by weight, a P content of 0.13 to 0.50% by weight, a lightness (L*)of 50-60 CIELAB units, a chroma (C*) of more than 43.5 CIELAB units, a red value (a*) of more than 25 CIELAB units, and a yellow value (b*) of more than 25 CIELAB units as measured in a barite pellet.

Brown iron oxide blends which contain a clean color shade, yellow-tinged red iron oxide pigment having a loss on ignition of less than about 1% by weight, a P content of 0.13 to 0.50% by weight, a lightness (L*) of 50-60 CIELAB units, a chroma (C*) of more than 43.5 CIELAB units, a red value (a*) of more than 25 CIELAB units, and a yellow value (b*) of more than 25 CIELAB units as measured in a barite pellet.

A process for producing a clean color shade, yellow-tinged red iron oxide pigment by calcination of magnetite, wherein the magnetite is produced by the oxidation of iron with nitrobenzene in an acid medium in the presence of phosphorous compounds, and the quantity of phosphorous used, relative to the quantity of metallic iron, is 1000-5000 ppm.