When you think of chlorine, the first thing that comes to your mind is the stuff you put in pools. Well that is one of the uses, but there is many, many more. Chlorine protects organisms ranging from the Ecuadorian tree frog, to wood rotting fungi. Chlorine is also surprisingly more plentiful than carbon. Believe it or not chlorine was the first substance used as a poisonous gas in World War I.
             Chlorine, symbol Cl, is a greenish-yellow gaseous element. In the group 17 of the periodic table, chlorine is one of the halogens. The atomic number of chlorine is 17. Elementary chlorine was first isolated in 1774 by the Swedish chemist Carl Wilhelm Scheele, who thought that gas was a compound of oxygen. It was not until 1810 that the British chemist Sir Humphry Davy proved that chlorine was an element and gave it its present name.
             At ordinary temperatures, chlorine is a greenish-yellow gas that can readily be liquefied under pressure of 6.8 atmospheres, at 20 degrees Celsius (68 degrees pharenhit). The gas has an irritating odor and can sometimes be dangerous. Chlorine does not occur in nature, but its compounds are common minerals, and it is the 20th most abundant element in the earth's crust. Cl has a specific gravity of 1.41 at -35 degrees Celsius (-31 degrees pharnehit). The atomic weight of the element is 35.453.
             Chlorine is an active element, reacting with water, organic compounds, and many metals. Chlorine will not burn in air, but will support the combustion of many substances. An ordinary paraffin candle, for example, will burn chlorine with a smoky flame. Chlorine and hydrogen can be kept together in the dark, but react explosively in the presence of light. Chlorine solutions in water are familiar in the home as bleaching agents.
             Most chlorine is produced by the electrolysis of ordinary salt solution, with sodium hydroxide as a by-product. Because the demand for chlorine exceeds that for sodium hydro...