Abstract: Electrothermal fluidized bed furnace useful particularly for chlorination of oxide of zirconium and the like utilizes graphite reactor tube longitudinally divided into a plurality of separate sectors by a corresponding number of longitudinal slits which are filled with insulating and refractory material. The reactor tube sectors are physically and electrically united at one end of the tube so that one or more pairs of opposite sectors are electroresistively heated while the intervening opposite sectors are left electrothermally unactivated for preventing short circuits which would otherwise result due to carbon fed together with the oxide. Owing to such electrothermal system, the furnace wall can be fluid-tightly sealed with use of metallic material for preventing harmful chlorine gas from leaking. Owing to such construction, the life of the graphite tube can be prolonged.

Abstract: A process for thermally treating synthetic diamond grains to eliminate magnetism thereof and a diamond grain product obtained by the process, which is suitable for manufacturing electrodeposited diamond tools.