Abstract: A method for producing hexagonal, laminar, alpha aluminum oxide monocrystals having a grain size of about 16 to about 250 microns, and a diameter to thickness ratio of about 3:1 to about 7:1. Aluminum hydroxide of particle size greater than 60 microns is calcined in the presence of a fluorine-containing mineralizer at a temperature of greater than 1200.degree. C. but no more than 1450.degree. C., and the desired grain size is separated from the calcinate.

Abstract: Red mud from the production of alumina from bauxite by the Bayer process is converted to a flocculating agent by reaction with sulfuric acid and drying the reaction product by direct heat transfer thereto by contact with hot solid bodies and by contact with hot gases. The resulting solid product is a mixture of water-soluble sulfates of iron and aluminum with minor proportions of other water-soluble metal sulfates in the form of free-flowing discrete particles.

Abstract: In the manufacture of phosphoric acid by treatment of phosphate ores with excess phosphoric acid and precipitation of calcium ions as calcium sulfate, the purity and quality of the byproduct calcium sulfate is substantially improved by subjecting the monocalcium phosphate extract of the ore before precipitation of calcium sulfate to one or more preliminary treatments, whereby contaminent ions are substantially and preferentially removed from the extract while the calcium remains substantially in solution. These preliminary treatments may include separation of fluoride by reaction with silicon compounds, separation of radium by reaction with barium compounds in the presence of sulfate ions, and separation of strontium as strontium sulfate.