Overview

Sodium hypochlorite is an inorganic compound usually encountered as a pale greenish, alkaline solution with the chemical formula NaClO (sometimes written NaOCl). In aqueous form it exists as a mixture of the sodium cation and the hypochlorite anion; see sodium ion and hypochlorite ion. The solution is more stable than the isolated solid, although it slowly decomposes under heat, light and in the presence of certain metal catalysts; for further context on its behavior in solution see compound stability.

Chemical behavior and properties

In water sodium hypochlorite is in equilibrium with hypochlorous acid (HOCl) and the hypochlorite ion (OCl–); the balance between these species depends on pH. At the moderately high pH of common household solutions the hypochlorite ion predominates. Sodium hypochlorite is classified as a strong oxidizing agent and can accept electrons from a variety of organic and inorganic substances, which is the basis for its disinfecting and bleaching action. Laboratory and industrial descriptions often highlight its oxidizing character; see oxidizing agent.

Production and historical notes

Commercial sodium hypochlorite is typically produced by reacting chlorine gas with sodium hydroxide, a reaction that yields a mixture including sodium chloride and sodium hypochlorite. Modern methods also include electrolytic processes that generate hypochlorite solutions directly. The liquid bleach historically called "Eau de Javel" was developed in the late 18th century and popularized the compound's use for bleaching and sanitation.

Uses and applications

The most familiar use of sodium hypochlorite is as a household bleach and surface disinfectant. It is used to remove stains from fabrics, sanitize hard surfaces, disinfect drinking-water supplies and swimming pools, and in industrial processes such as pulp bleaching. In organic chemistry it serves as a convenient oxidant in some reactions. Commercial formulations often contain additional ingredients such as stabilizers and surplus sodium hydroxide to slow decomposition and maintain alkalinity. For consumer guidance, manufacturers label such products as a bleach and disinfectant.

Safety, handling and reactions

Sodium hypochlorite solutions are corrosive and can irritate skin, eyes and mucous membranes. They should never be mixed with acids because the reaction produces chlorine gas, a dangerous respiratory irritant; mixing with acids is described further at reaction with acids producing chlorine. Combining hypochlorite with ammonia or many organic compounds can release toxic chloramine or other chlorinated by-products. Textile damage can occur because alkaline components may weaken natural fibers, especially cotton, and prolonged exposure will degrade materials.

Practical precautions

  • Avoid mixing bleach with acids or ammonia; use only in well-ventilated areas.
  • Store solutions in opaque, cool containers to reduce decomposition.
  • Wear protective gloves and eye protection when handling concentrated solutions.
  • Dispose of small amounts according to local guidelines; large discharges can harm aquatic life.

Despite its useful disinfectant and bleaching properties, sodium hypochlorite must be handled with caution and respect for its chemical reactivity and potential environmental effects.