Abstract: Rare earth values are recovered from gypsum starting material by (i) dissolving such gypsum in water and separating therefrom the water-insoluble fractions which contain the rare earth elements (ii) treating such insoluble fractions with a solution of carbonate ions, (iii) next digesting the insoluble fractions thus treated with a mineral acid and converting at least the rear earth values into water-soluble salts thereof, and (iv) recovering such rear earth values from the medium of digestion.

Abstract: Chromium oxide green in the form of donut-shaped, ring-shaped or tire-shaped particles having an internal diameter of from 0.01 to 0.5 mm and an external diameter of from 0.05 to 1.0 mm is prepared by spraying an aqueous chromium oxide green suspension through a liquid pressure nozzle into a spray dryer such that the suspension entering the drying space of the spray dryer is rotating.

Abstract: An improved dilute phase chlorination procedure characterized by providing extremely finely divided oxygen-containing metallic material and a carbonaceous material co-milled together to a particle size size of less than 20 microns. The finely divided charge material is introduced into a tubular reaction zone, preferably at the bottom, with the gaseous chlorination agent where reaction occurs at a temperature above 800.degree. C. for a period of time sufficient to fully react the chlorinating agent in a single pass. Metal chloride is recovered from the tubular reactor and, most advantageously, there is little or no need to separate any dusty unreacted solid material from the off-gases for recycle to the chlorination zone.

Abstract: Gallium is purified by washing organic solutions containing hydroxamic acid complexes of gallium with aqueous solutions, individually or in series, especially amine or ammonia solutions, and dilute acid solutions. The method is applicable to a variety of gallium sources, and capable of producing gallium of extremely high purity, especially with a repetitive procedure.

Abstract: The invention relates to a method for the preparation of particulate pigmentary titanium dioxide. The method comprises reacting, in solution, a precursor titanium tetrahalide with sulfuric acid to produce an intermediate titanyl sulfate product. Following crystallization and recovery of this intermediate product from solution the crystallized intermediate is redissolved in an aqueous solvent medium and hydrolyzed at elevated temperatures to provide a particulate amorphous titanium dioxide intermediate product. After separation from the aqueous solvent medium, this intermediate product then is subjected to calcination at elevated temperatures to produce the desired particulate titanium dioxide end product.

Abstract: The present invention concerns a process for obtaining a ceric oxide, and, more precisely, a process for increasing and stabilizing at high temperature the specific surface area of a ceric oxide. The invention process, which consists of the preparation of a ceric oxide by calcination of a ceric hydroxide, is characterized by the fact that the ceric hydroxide is subjected to solvothermal treatment before calcination.

Abstract: Potassium manganate is produced by mixing finely ground manganese ore with a solution of potassium hydroxide (having a concentration of about 50% W/V) in a mole ratio KOH/MnO.sub.2 between 2 and 3. The resulting suspension is fed continuously to an atomization dryer and then to a plate dryer.

Abstract: There is provided a method of producing titanium-oxides which comprises: admixing an aqueous solution of titanium tetrachloride with sulfuric acid in amounts of at least 0.5 times is moles as the titanium tetrachloride; adding an alkali to the resultant solution to produce titanium hydroxide; and drying and calcining the titanium hydroxide. A further method is provided which comprises: adding a solution of an alkali to an aqueous solution of titanium tetrachloride having a concentration of not more than 2.5 moles/l at temperatures of not less than 50.degree. C., thereby to substantially thermally hydrolyze the titanium tetrachloride and to produce titanium hydroxide; and drying and calcining the titanium hydroxide.

Abstract: Process for purifying TiO.sub.2 ore consisting essentially of subjecting the ore to two or more leaching treatments, said leaching treatments alternating between use of an aqueous solution of a mineral acid and an aqueous solution of an alkali metal compound selected from the group consisting essentially of alkali metal carbonates, hydroxides or mixtures thereof.

Abstract: A titanium dioxide composition useful as the opacifier agent for vitreous enamels and fusion enamels comprises TiO.sub.2 predominantly in the form of isometric primary particles from 0.5 to 5.0 .mu.m in size, which are aggregated to predominantly spherolithic particles 1 to 100 .mu.m in diameter, with a BET surface of 1 to 4.5 m.sup.2 /g and an apparent density of 0.2 to 1.3 kg/l, is prepared by subjecting titanium dioxide hydrate having a BET surface of from 50 to 500 m.sup.2 /g to accelerated calcination at temperatures of 800.degree. to 1600.degree. C.

Abstract: A process is disclosed for purifying molybdenum containing arsenic and phosphorus which involves leaching molybdenum trioxide in an acid at a temperature of above about 70.degree. C.