Appearance
Chlorine is a greenish yellow, dense gas with a sharp smell.

Source
Chlorine is not found free in nature but combined chiefly with Sodium as Sodium chloride in common salt and the minerals Carnalite and Sylvite. Chlorine is produced commercially by the electrolysis of Sodium chloride.

Uses
Chlorine is widely used in many different areas. It is used in the production of safe drinking water and many consumer products such as paper, dyestuffs, textiles, petroleum products, medicines, antiseptics, insecticides, foodstuffs, solvents, paints and plastics. It is also used to produce chlorates, chloroform, Carbon tetrachloride and Bromine. A further substantial use for Chlorine is in organic chemistry, both as an oxidising agent and in substitution reactions.

General Information
The chloride ion is essential to life. Chlorine gas, however, is a respiratory irritant, which can be fatal after a few deep breaths. It was used during World War I as a poisonous gas. Chlorine liquid burns the skin.