Wolfram (tungsten) filament high-intensity incandescent lamp
containing iodine in a quartz envelope.
Used primarily as a source of visible
In halogen lamps, the quartz envelope is closer to the filament than the glass used
in conventional light bulbs. Heating the filament to a high temperature causes the tungsten
(wolfram) atoms to evaporate and combine with the halogen gas. These heavier molecules are then
deposited back on the filament surface. This recycling process increases the life of the tungsten
(wolfram) filament and enables the lamp to produce more light per unit of input energy. Consequently,
halogen lamps are used in a variety of applications, including automobile headlights.
Halogens other than iodine may be used in these lamps.
PAC, 2007, 79, 293
(Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006))
on page 407
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook