34 EXOTHERMIC MATERIAL CONSISTING OF MIXED METALLIC OXIDES IN FINELY DIVIDED FORM OR IN A PREFORMED SHAPE, USABLE FOR HEATING, JOINING TUBES, PIPES AND THE LIKE BY BRAZING; AND THE COMPLETE KIT CONSISTING OF SHAPED EXOTHERMIC SLEEVES, BRAZING RINGS, IGNITION PASTE AND FASTENERS FOR HOLDING THE SLEEVES IN PLACE