October 31 - November 3, 2004
Element of the Day
Wednesday, November 3
Greek.
iodes: violet. Iodine, a
halogen, occurs sparingly in the form of iodides in sea water from which it is
assimilated by seaweeds, Chilean saltpeter, nitrate-bearing earth (known as
caliche), brines from old sea deposits, and in brackish waters from oil and salt
wells
Discovered by: Courtois in 1811
Uses: Iodine compounds are important in organic chemistry and very useful in medicine. Iodides, and thyroxine which contains iodine, are used internally in medicine, and as a solution of KI and iodine in alcohol is used for external wounds. Potassium iodide finds use in photography. The deep blue color with starch solution is characteristic of the free element.
The picture shows the result of touching nitrogen triiodide (NI3)! Nitrogen triiodide is percussion sensitive.