Chemistry of the Incandescent Lamp

Abstract Halogen lamps have been on the market for some time; they are replacing the conventional lamp in many fields except general service (domestic) applications. Their relatively small bulbs contain small amounts of halogen is addition to an inert gas. The mode of action of the iodine lamp, which depends on the presence of traces of oxypgen, has been elucidated. Tungsten evaporating from the filament is returned to it by a cyclic process involving a tungsten oxide and WO2I2. No tungsten is ever deposited on the bulb wall of such a lamp. A regenerative cycle in which the vaporized tungsten is deposited on the hottest (and hence most vulnerable) parts of the filament can, in principle, be realized by the use of fluorine compounds.