History
A carbon filament lamp using chlorine to prevent darkening of the envelope was patented in 1882, and chlorine-filled "NoVak" lamps were marketed in 1892. The use of iodine was proposed in a 1933 patent, which also described the cyclic redeposition of tungsten back on the filament. In 1959 General Electric patented a practical lamp using iodine.
Read more about this topic: Halogen Lamp
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