Abstract: The invention relates to an improved process for the production of alumina according to the Bayer technology, of bauxites containing goethite and especially of boehmitic or diasporic bauxites, for the acceleration of the digestion process, for the transformation of goethite into hematite, for the increase of alumina yield and for the reduction of the caustic soda losses, the essence of which consists in carrying out the digestion in the presence of 2-6% CaO and 0.2-2.0% Mg.sup.++, Fe.sup.++, Mn.sup.++ Co.sup.++ ions based on the weight of the dry bauxite or of compounds or ores containing these ions in the indicated quantities.

Abstract: Displacement slurry pump equipped with known piston-rod drive, in which on a piston rod expediently three pistons are arranged at a distance of at least one stroke length, they are a liquid piston moving the auxiliary liquid free of solid matter, and on both sides thereof a slurry piston each moving on one side the slurry, on the other side, however, the auxiliary liquid. The liquid piston fits sealed to the liquid cylinder provided with liquid suction valves, whereas the two slurry pistons fit by slot to the slurry cylinders provided with slurry suction valves and slurry delivery valves. The effective section of the liquid cylinder is larger than the effective section of a slurry cylinder each. The slurry pump may be of single-operation or of double-operation, of one-cylinder or two-cylinder or three-cylinder construction.

Abstract: A container adapted to thoroughly mix fluid material, especially suspensions, comprising a tank provided with a vertical mixing pipe, a vertical air lifting pipe, a gas collecting chamber located at the upper end of the mixing pipe, and a connecting pipe affixed at one end to the collecting chamber and communicating therewith and affixed at its other end to the bottom of the air lifting pipe and communicating therewith.

Abstract: A method for processing bauxites according to the Bayer technology, with an increased yield in Al.sub.2 O.sub.3 and with decreased caustic soda losses, starting particularly from goethite bauxites of boehmite and/or diaspore type and carrying out the digestion at 180.degree.C to 300.degree.C using an aluminate liquor containing Na.sub.2 O.sub.caustic in a concentration of 80 to 300 g./l. The digestion is carried out in the presence of a calcium compound in an amount corresponding to 2 to 6 % of CaO calculated for the dry weight of bauxite and of a sulfate salt in an amount corresponding to 1.0 to 7.0 g./l. of sulfate ion concentration, whereby the goethite content of the bauxite is converted into hematite. The process provides advantageous conditions for the complete dissolution of the boehmite and diaspore content of bauxite in the vicinity of the equilibrium molar ratio, and enables to recover efficiently the caustic soda losses in the Bayer process itself, requiring no supplementary operation.