Sodium hypochlorite, commonly known as bleach, is a compound widely used as a disinfectant and bleaching agent. Here we take a deep dive into understanding this chemical compound – its history, composition, uses, safety measures and more.
Composition and History
Sodium hypochlorite is formed by bubbling chlorine gas through a solution of sodium hydroxide or sodium carbonate. Wilhelm Mulert first synthesized sodium hypochlorite in the 1830s while experimenting with chlorine and alkalis. The compound was initially used for bleaching textiles, but its strong disinfecting properties were soon discovered. During World War I, sodium hypochlorite was used on a large scale to disinfect medical equipment and surgical instruments. Since then, it has remained an important disinfectant in various commercial and domestic applications.
Chemical properties and Formula
The molecular formula of Sodium Hypochlorite is NaClO. It exists as a pale yellowish liquid or white powder at room temperature. Sodium hypochlorite contains hypochlorous acid (HOCl), which is responsible for its disinfecting abilities. HOCl readily decomposes to form sodium chloride (table salt) and oxygen. The decomposition becomes more rapid with increase in temperature or exposure to light. This instability is the reason for sodium hypochlorite solutions needing to be freshly prepared. Commercially available bleaches contain 5-15% available chlorine content.
Uses of Sodium Hypochlorite
Some key areas where sodium hypochlorite finds widespread application are:
– Water treatment: It is commonly used as a disinfectant in municipal water treatment plants to kill microbes. Sodium hypochlorite makes tap water potable for human consumption.
– Swimming pools: Regular addition of sodium hypochlorite to pools keeps the water sanitized and prevents algal and bacterial growth.
– Bleaching: Low concentrations help remove stains and whiten clothes during laundering. It is also used industrially for bleaching wood pulp and textiles.
– Household cleaning: Diluted solutions effectively kill germs on surfaces, making it a popular ingredient in multi-purpose cleaners and disinfectants.
– Food processing: Some concentrations are approved for use in washing, peeling and disinfecting fruits and vegetables. It removes natural waxes, dirt and microbes.
– Healthcare: Due to its broad-spectrum disinfection activity against bacteria, viruses and fungi, sodium hypochlorite finds application in sanitizing medical equipment, disinfecting wounds, sterilizing hospital surfaces, etc.
Disinfection Mechanism
The bactericidal properties of sodium hypochlorite come from hypochlorous acid, which readily penetrates the cell wall and membrane of microbes. Once inside the cell, HOCl disrupts protein synthesis and causes lipid peroxidation – damaging cellular membranes and proteins beyond repair. This rupture of cell integrity ultimately leads to cell death. HOCl is also highly reactive, so it readily breaks down into chloride (Cl-) and oxygen (O2) ions, which don’t allow revived microbial growth post-treatment.
Safety Measures with Sodium Hypochlorite
While an effective disinfectant, sodium hypochlorite solutions can cause irritation, burns or toxicity in high concentrations or improper use. Some important safety measures include:
– Avoid ingestion or inhalation of the solution. If accidental contact occurs, immediately flush with water and seek medical attention.
– Store in a cool, dry place away from direct sunlight and heat sources. Higher temperatures cause it to decompose faster, generating toxic chlorine gas.
– Always add the hypochlorite solution to water, not vice versa, to avoid violent splattering.
– Make fresh dilutions daily for maximum efficacy and safety, as chemical stability decreases with time.
– Wear protective gloves, clothes and eyewear while handling the compound directly.
– Rinse all surfaces with ample water after application to remove residual hypochlorite ions.
In summary, sodium hypochlorite is an indispensable chemical with multiple commercial and domestic uses owing to its powerful antimicrobial properties. With proper precautions during storage, handling and use, it remains an affordable and effective household cleaner and disinfectant. Further research continues to expand our understanding and applications of this chemical compound.
