But if you add the gas to fill the bulb with a gas, such as iodine, everything will change completely. The volatile tungsten atoms will combine with iodine atoms, forming tungsten iodine, which will not be deposited on the wall of the bulb. Decompose on the hot surface of the filament, returning the tungsten to the filament and steam. iodine back bulb. But here’s the thing: the wall’s temperature must be quite high – around 250 ° C. Personalized custom name Dog this is my couch go sit over there pillow. That’s why halogen bulbs are so compact and very hot, of course. Halogen lamps, due to the high temperature of the filament, give a whiter light and have a longer lifespan than conventional incandescent lamps.