What is the difference between hypochlorous acid (HOCl) and chlorine dioxide (ClO2)?

Chlorine dioxide is a compound of chlorine (Cl) and oxygen (O2). The names and scientific formulas of hypochlorous acid and chlorine dioxide are similar, but they are two extremely different substances. The main difference is seen in effectiveness: it takes much more chlorine dioxide to have the same anti-microbe power as HOCl.

See also the table below for a more detailed overview of the differences:

	Hypochlorous Acid	Chloordioxide
Scientific Formula	HOCl	ClO2
Production	Electrolysis of water and salt	Door een chemische reactie van natriumchloriet met natriumbisulfaat
Kleur	Transparent	Yellow
Efficacy	Uiterst effectief tegen: Bacteriën Virussen Schimmels/gisten	Lagere effectiviteit dan HOCl in dezelfde concentraties, met name tegen gisten/schimmels
Bijeffecten	Hypoallergenic and gentle to the skin	Toxic if inhaled, explosive
Warning Symbols	N/A

Equilibrium chart: chlorine in solution

The graph above shows how the composition of chlorine changes in relation to pH in three phases of Cl2, HOCl and OCl-. A lot of HOCl can be made when the pH of the water is between 4.0 and 7.0.

Because HOCl has proven to be an approximately 100 times stronger disinfectant than ClO2, it can be extremely effective when the chlorine concentration is only a few ppm. Chlorine dioxide does not have this broad efficacy, requiring much more agent to be used to aquire the same result. (OR to achieve the same result).