https://doi.org/10.15255/KUI.2021.012
Published: Kem. Ind. 70 (7-8) (2021) 429–436
Paper reference number: KUI-12/2021
Paper type: Review / Chemistry in Teaching
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Chlorine in Water – An Example of Chemical Equilibria and Reactivity

N. Raos

Abstract

Chlorine water is not, simply, chlorine gas dissolved in water, but a complex solution of chlorine, Cl₂(aq), hydrochloric (HCl), and hypochlorous acid (HOCl), containing also Cl₃− ions as well as NaCl from original electrolyte. All of these components are in mutual equilibria. In this paper a short history of chlorine chemistry and technology is presented, as well as reversible and free-radical reactions in its aqueous solution. Properties of HOCl as a disinfectant and its physiological effects are also discussed. Diluted, 50–100 ppm HOCl solutions, named “electrochemically activated water” (ECA), or similar, have recently become popular disinfectants. Despite the advantage of its simple preparation, by electrolysis of NaCl solutions, ECA is very unstable, so the utmost care must paid to its preparation and protection from light. Diluted chlorine water, if properly prepared and stored, could be stable for months.

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Keywords

chemistry education, history of chemistry and chemical technology, hypochlorous acid, disinfectants, reactions of chlorine