Iodine

Iodine
Properties
Atomic symbol	I
Atomic number	53
Classification	Halogen
Atomic mass	126.90447 amu
Number of Stable Isotopes	1
Density (grams per cc)	4.93 g/cm^3
Other Information
Date of discovery	1811
Name of discoverer	Barnard Courtois
Name origin	Greek 'iodes', violet
Uses	Pharmaceuticals, food supplements, dyes, catalysts.
Obtained from	Brine, seaweed.

Iodine (Pronounced eye-o-dyne or eye-o-dean) is a chemical element. A trace element, it is required by humans for the synthesis of the thyroid hormone thyroxin. People who do not get enough iodine in their diet can suffer from goiter, a disease of the thyroid. This is rarely a problem; but to make sure, iodine is often added to salt ("iodized salt".)

Iodine is a solid which sublimes at room temperature—it slowly evaporates directly into the gaseous vapor phase, without going through a liquid phase.

It was discovered by accident in 1811, while Barnard Courtois was treating seaweed ash (which contains a significant amount of iodine) with sulfuric acid.

For a long time a substance called "iodine" has been used as a household treatment/disinfectant for cuts and scrapes. That is actually tincture of iodine, a dilute solution of potassium iodide in alcohol.