Portable electric heaters, components for use in electric heaters, furnaces and melting furnaces; heat diffusion plates made of ultra pure aluminum oxide used as backings during thermal processes to prevent contact reactions in furnaces and melting furnaces

[ OXIDE CERAMIC MASSES FOR THE PRODUCTION OF SINTERED OXIDE CERAMICS, ] OXIDE [ CERAMIC ] TUBES, ROD AND PLATES, ALL FOR GENERAL USE IN THE INDUSTRIAL ARTS