1,3,5,7 Boiling point 239.1 Stable isotopes 2 Heat of vapor. Back Chlorine Chlorine is the most common of the halogens. It is not as chemically active as fluorine, but is still very active and forms compounds with most elements. In pure form, it is a greenish-yellow gas with a sharp, irritating odor. It is manufactured on a large scale by electrolysis of concentrated solutions of sodium chloride.
Chlorine is a strong oxidizing agent and as a result is effective in killing bacteria.
This has led to widespread use in the sterilization of drinking water, for swimming pools, etc. Hydrogen chloride, HCl, is a gas with a sharp unpleasant odor. The gas dissolves readily in water with the liberation of heat. This forms hydrochloric acid, a very strong acid. Reference Pauling Ch.