5. Chlorine

5.1 Introduction

Chlorine has been the world's most widely used disinfectant since its first applications in water treatment around 1897 in Europe.

This oxidizing agent has made it possible to achieve a major technological breakthrough, making it possible to reach a level of hygiene and quality that has put a stop to major waterborne epidemics, at low cost and with formidable effectiveness. It can be used in :

• chlorine gas Cl ₂ (liquefied in bottles or tanks, used by direct sampling in the gas phase, or in the liquid phase via an evaporator, and introduced into the water after dosing and dissolving in a device called a chlorometer);

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