19 November 2021 Bulletin

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Chlorine dioxide

Chlorine dioxide is a chemical compound with the formula ClO₂. [1] It is a synthetic, green-yellowish gas with a chlorine-like, irritating odour. Chlorine dioxide is a neutral chlorine compound, which is very different from elementary chlorine, both in its chemical structure as in its behaviour. Chlorine dioxide is a small, volatile and very strong molecule. In diluted, watery solutions it is a free radical. At high concentrations it reacts strongly with reducing agents. Chlorine dioxide is an unstable gas that dissociates into chlorine gas (Cl₂), oxygen gas (O₂) and heat. When it is photo-oxidised by sunlight, it falls apart. The end products of chlorine dioxide reactions are chloride (Cl-), chlorite (ClO-) and chlorate (ClO_3-). At –59°C, solid chlorine dioxide becomes a reddish liquid. At 11°C chlorine dioxide turns into gas. It is 2 - 4 times denser than air. As a liquid, chlorine dioxide has a bigger density than water. One of the most important qualities of chlorine dioxide is its high water solubility, especially in cold water. It does not hydrolyse when it enters water; it remains a dissolved gas in solution. Chlorine dioxide is approximately 10 times more soluble in water than chlorine. Chlorine dioxide can be removed by aeration or carbon dioxide. [2]

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