|MadSci Network: Chemistry|
Iodine is one of those solid elements that sublime (that is go directly from the solid phase to the gaseous phase) rather than melt and boil when heated under atmospheric conditions. The purple vapor is simply iodine in the gaseous phase. Bromine (red) and chlorine (green-yellow) are other halogens that are colored in the gaseous phase, although these are liquids that boil normally when heated.
Admin note: The vapors of iodine and other halogens are quite toxic, and should only be handled in facilities where the vapors can be adequately contained.
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