PRODUCTION & STABILITY

Hypochlorous acid can be made from chlorine bleach by dilution however there are limitations. Hypochlorous acid is almost nonexistent in a free chlorine solution with a pH above 9. Chlorine bleach has a pH above 13. By diluting chlorine bleach, the pH can be lowered however the concentration of free chlorine will also be lowered. Upon diluting chlorine bleach to pH 8.5, the percent of the free chlorine that is hypochlorous acid is less than 5%. More dilution will dilute the free available chlorine concentration to unuseful levels. Trying to lower the pH with acidifiers will not help either because chlorine bleach will react violently and the free available chlorine product will be lost as chlorine gas. Therefore, electrolysis is the only safe method for generating high concentrations of acidic-to-neutral pH free chlorine solutions that are dominated by hypochlorous acid. At pH 5, the percent of free chlorine that is hypochlorous acid is above 99%.

Hypochlorous acid is a strong oxidant that is seeking to steal electrons from another molecule. Synthetic surfaces are difficult to steal electrons from however organic matter, microbial pathogens, or oxygen in the air is easy to steal electrons from. Once hypochlorous acid steals an electron, it either binds to that molecule and forms a new molecule, reverts back to hypochlorite, or it turns back into saline.

Hypochlorous acid is made through a process called electrolysis. By passing a sodium chloride solution (NaCl) through an electrolysis cell containing an anode and a cathode, electrolyzed water is generated. There are two commonly used electrolysis methods for generating hypochlorous acid, membrane cell electrolysis and single cell electrolysis. Membrane cell electrolysis converts a saltwater brine into two solutions, a strongly acidic anolyte of hypochlorous acid and a strongly alkaline catholyte of sodium hydroxide. Single cell electrolysis converts a saltwater brine into one solution, a slightly acidic-to-neutral anolyte of hypochlorous acid.

Depending on the process used to generate the hypochlorous acid, the solution can be stable. Membrane cell electrolysis generates two streams with opposing oxidation-reduction potentials and opposite pH. This is done by forcing positively charged sodium ions across a membrane toward the cathode side. On the anode side, a very high concentration of anolyte is generated that is strongly acidic (~ pH 3). Generating hypochlorous acid by this method is not as stable as that generated by single cell technology. Single cell technology uses an acidified brine and only one stream of solution is generated in the pH range of 5-7. When generating hypochlorous acid through a single cell, no high pressures are used and no ions are forced across a membrane. The hypochlorous acid generated is stable, not seeking a new equilibrium like the anolyte generated from membrane cell systems.

The shelf-life can be 3-6 months if stored in a closed container protected from the oxygen in the air and at a temperature lower than 25 Deg C (77 Deg F). Containers that block out UV light may have a small effect on extending shelf-life.

PRODUCTION & STABILITY

Hypochlorous acid can be made from chlorine bleach by dilution however there are limitations. Hypochlorous acid is almost nonexistent in a free chlorine solution with a pH above 9. Chlorine bleach has a pH above 13. By diluting chlorine bleach, the pH can be lowered however the concentration of free chlorine will also be lowered. Upon diluting chlorine bleach to pH 8.5, the percent of the free chlorine that is hypochlorous acid is less than 5%. More dilution will dilute the free available chlorine concentration to unuseful levels. Trying to lower the pH with acidifiers will not help either because chlorine bleach will react violently and the free available chlorine product will be lost as chlorine gas. Therefore, electrolysis is the only safe method for generating high concentrations of acidic-to-neutral pH free chlorine solutions that are dominated by hypochlorous acid. At pH 5, the percent of free chlorine that is hypochlorous acid is above 99%.

Hypochlorous acid is a strong oxidant that is seeking to steal electrons from another molecule. Synthetic surfaces are difficult to steal electrons from however organic matter, microbial pathogens, or oxygen in the air is easy to steal electrons from. Once hypochlorous acid steals an electron, it either binds to that molecule and forms a new molecule, reverts back to hypochlorite, or it turns back into saline.

Hypochlorous acid is made through a process called electrolysis. By passing a sodium chloride solution (NaCl) through an electrolysis cell containing an anode and a cathode, electrolyzed water is generated. There are two commonly used electrolysis methods for generating hypochlorous acid, membrane cell electrolysis and single cell electrolysis. Membrane cell electrolysis converts a saltwater brine into two solutions, a strongly acidic anolyte of hypochlorous acid and a strongly alkaline catholyte of sodium hydroxide. Single cell electrolysis converts a saltwater brine into one solution, a slightly acidic-to-neutral anolyte of hypochlorous acid.

Depending on the process used to generate the hypochlorous acid, the solution can be stable. Membrane cell electrolysis generates two streams with opposing oxidation-reduction potentials and opposite pH. This is done by forcing positively charged sodium ions across a membrane toward the cathode side. On the anode side, a very high concentration of anolyte is generated that is strongly acidic (~ pH 3). Generating hypochlorous acid by this method is not as stable as that generated by single cell technology. Single cell technology uses an acidified brine and only one stream of solution is generated in the pH range of 5-7. When generating hypochlorous acid through a single cell, no high pressures are used and no ions are forced across a membrane. The hypochlorous acid generated is stable, not seeking a new equilibrium like the anolyte generated from membrane cell systems.

The shelf-life can be 3-6 months if stored in a closed container protected from the oxygen in the air and at a temperature lower than 25 Deg C (77 Deg F). Containers that block out UV light may have a small effect on extending shelf-life.