What is the Difference Between Sodium Hypochlorite and Hypochlorous Acid?

Sodium hypochlorite and hypochlorous acid are both chlorine-based disinfectants, but they have different chemical formulas and properties. The main differences between them are:

1. Chemical Formula: Sodium hypochlorite has the formula NaOCl, while hypochlorous acid has the formula HOCl.
2. pH: Hypochlorous acid has a near-neutral pH, ranging between 5-7, while sodium hypochlorite (bleach) has a highly alkaline pH of 8-13.
3. Disinfection Efficacy: Hypochlorous acid is 80 to 120 times more effective at killing germs than sodium hypochlorite. The germ-killing properties of bleach come from hypochlorous acid, but at a high pH, most of the hypochlorous acid in bleach is converted to hypochlorite, which is a less effective disinfectant.
4. Penetration: Hypochlorous acid can penetrate the cell walls of pathogens more effectively than hypochlorite or bleach, which has a negative charge and struggles to penetrate the cell walls of many pathogens.
5. Mildness: Hypochlorous acid is milder than sodium hypochlorite, with a lower pH, salt content, and parts per million of chlorine.

In summary, while both sodium hypochlorite and hypochlorous acid are effective disinfectants, hypochlorous acid is generally considered the superior choice due to its higher efficacy, near-neutral pH, and ability to penetrate pathogens more effectively. However, to maximize its disinfection power, surfaces should be pre-cleaned with soap and water before applying hypochlorous acid.

Comparative Table: Sodium Hypochlorite vs Hypochlorous Acid

Here is a table comparing the differences between sodium hypochlorite and hypochlorous acid:

Both sodium hypochlorite and hypochlorous acid are inorganic ionic compounds containing oxides of chlorine. The key difference between the two is that sodium hypochlorite contains a sodium cation (Na+), while hypochlorous acid contains a hydrogen cation (H+). Sodium hypochlorite is a salt, whereas hypochlorous acid is a molecular compound. The pH of sodium hypochlorite is highly alkaline (8-13), while hypochlorous acid has a near-neutral pH (5-7). Hypochlorous acid is generally considered to be more effective as a disinfectant due to its neutral pH.