III.

Uses and Production

Chlorine is an active element, reacting with water, organic compounds, and many metals. Four oxides have been prepared: Cl₂O, ClO₂, Cl ₂O₆, and Cl₂O₇. Chlorine will not burn in air, but it will support the combustion of many substances; an ordinary paraffin candle, for example, will burn in 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, or in weaker solutions as a sterilizing agent, for example in swimming pools and public water systems. A few parts per million of chlorine can be added to drinking water to kill bacteria, and the chlorine then removed with sodium sulphite prior to distribution to homes.

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 hydroxide, some industrial chlorine is produced by treating salt with nitrogen oxides or by oxidizing hydrogen chloride. Chlorine is shipped as a liquid in steel bottles. It is used for bleaching paper pulp and other organic materials, destroying germ life in water, and preparing bromine, tetraethyl lead, and other important products.