Abstract: A composition comprising .alpha.-alumina in a concentration of at least 99.95 weight percent and process for producing such .alpha.-alumina wherein alumina having an alkali metal content between 0.05 and 0.60 weight percent and Al.sub.2 O.sub.3 content of more than 95 weight percent is electrically fused with silica and additional alkali, if desired, in an electric arc furnace, the heated composition is cooled, comminuted and the so-formed glass phase is removed from an alumina containing phase by mechanical or chemical means.

Abstract: A process for the manufacture of granular abrasives having improved grain toughness from refractory, inorganic hard substances which comprises crushing a lump or block of said refractory inorganic substance, thereafter subjecting the resultant grains to a grind sorting process such that substantially only the porous grains, grains containing flaws or coarsely crystalline grains are comminuted and separating them in the ground condition from the balance of the material.

Abstract: An electrical heating element composition comprising crystals of fused magnesium oxide improved by the inclusion of 0.05 to 5% by weight, based on the weight of said fused magnesium oxide, of an additive composition which has excellent lubricating properties in respect of the magnesium oxide crystals and reacts at 800.degree. to 1050.degree. C with active conductivity centers at the surface of one or more adjacent magnesium oxide crystals; an improvement in the preparation of an electrical heating element wherein a granular fused magnesium oxide composition is subjected to mechanical shaping and calcination which comprises employing as the electrical heating element composition a composition comprising crystals of fused magnesium oxide and 0.05 to 5% by weight, based on the weight of said fused magnesium oxide, of an additive composition which has excellent lubricating properties in respect of the magnesium oxide crystals and reacts at 800.degree. to 1050.degree.