Sodium hypochlorite may not occur naturally in stable form, but it has become one of the most widely used chemicals in modern life. Best known as the active ingredient in household bleach, it is in a number of everyday household cleaning products, such as laundry detergent.
Beyond the home, its industrial applications are far-reaching, from treating drinking water and wastewater to supporting food safety, healthcare, textiles, and even disaster response.
In this post:
Key Takeaways
Sodium hypochlorite is used in homes, hospitals, and industries to kill harmful microorganisms
It helps keep drinking water and wastewater safe and clean
It is a vital part of various industrial processes, including recycling, textile production, and papercrafting
The chemical provides rapid, effective water disinfection during disasters
What is Sodium Hypochlorite?
The chemical formula for the anhydrous compound can be written as either NaOCl or NaClO. Its hydrous crystalline form has a chemical formula that can be written as either NaOCl·5H2O or 2NaOCl·10H2O.
This substance exists both as a solid and as a liquid or aqueous solution.
In solid form, it can either be an anhydrous (doesn’t contain water) or hydrous (contains water) compound.
The hydrous form is light greenish-yellow in colour, and has an orthorhombic crystal structure, which is about 44% sodium hypochlorite by weight. Its melting point is between 25-27°C in one atmosphere.
Although an aqueous solution of sodium hypochlorite is a weak base, it’s considered as a salt of hypochlorous acid. The hypochlorite ions are the ones that oxidise, or remove electrons from substances, including the protective membranes of bacteria and viruses. This is how this chemical acts as a disinfectant.
Just like other hypochlorite compounds, anhydrous sodium hypochlorite is potentially explosive. It’s so unstable, in fact, that even a small amount of heat or friction could ignite it. Even in hydrous and aqueous form, sodium hypochlorite decomposes over time.
How Safe is Sodium Hypochlorite?
When left in the open air at room temperature, anhydrous sodium hypochlorite decomposes more rapidly because of exposure to carbon dioxide in the air. This is why it must be kept refrigerated.
Indeed, lower temperatures make sodium hypochlorite much more stable, with the optimum temperature being 7°C. At this temperature, only about 1% of the compound decomposes in the course of a year.
Meanwhile, high temperatures aid in the decomposition of sodium hypochlorite. In solid, crystalline pentahydrate form, the chemical decomposes at 101°C, which is also its boiling point.
In an aqueous solution, high temperatures cause it to decompose into sodium chloride and sodium chlorate:
3 NaOCl (aq) → 2 NaCl (aq) + NaClO3 (aq)
To some extent, an aqueous solution of sodium hypochlorite is in dynamic equilibrium. This is because although it continues to decompose over time, its ions tend to continuously react and balance the equations.
For example, the hypochlorite component of the compound is in dynamic equilibrium with water in aqueous solution, as shown in the balanced equation below:
OCl− + H2O ⇌ HOCl + OH−
As you can see, the reaction between the hypochlorite ions and a molecule of water forms hypochlorous acid and a hydroxide ion. This is a relatively weak acid. Therefore, overall, the solution maintains its alkalinity.
What is Sodium Hypochlorite Found in?
Sodium hypochlorite is present in a wide range of products and processes, from everyday household cleaners to large-scale industrial applications.
Its strong oxidising and disinfecting properties make it a versatile compound, allowing it to be used in cleaning products, water treatment, food processing, healthcare, textiles, and more.
Household and Domestic Uses of Sodium Hypochlorite
In the home, you’ll likely have heard of sodium hypochlorite as the active ingredient in bleach.
It is used to whiten clothes, remove stains, clean kitchen and bathroom surfaces, and kill harmful bacteria. Its strong disinfecting power makes it a household staple for everyday cleaning.
Sodium Hypochlorite in Industrial Cleaning and Sanitation Applications
Beyond domestic use, sodium hypochlorite is widely applied in industrial cleaning.
Factories, warehouses, and commercial kitchens rely on it to sanitise equipment, floors, and production lines. Its ability to break down organic matter and neutralise pathogens makes it indispensable for maintaining hygiene on a large scale.
Sodium Hypochlorite in the Food and Beverage Industry
Food processors and beverage manufacturers rely on sodium hypochlorite to sanitise equipment, conveyor belts, and surfaces that come into contact with food.
It helps maintain strict hygiene standards, ensuring products remain safe for consumers.
Sodium Hypochlorite in the Pulp and Paper Industry
In paper production, sodium hypochlorite is commonly used as a bleaching agent. It helps remove colour from recycled fibres and brightens paper products, making them suitable for printing and packaging.
Sodium Hypochlorite in Textile Production and Bleaching
The textile industry uses sodium hypochlorite to bleach fabrics, particularly cotton and synthetic fibres. Its oxidising properties help remove natural pigments, producing bright and uniform textiles.
Sodium Hypochlorite in Agriculture and Farming
Farmers use sodium hypochlorite solutions to disinfect equipment, animal housing, and irrigation systems. It helps prevent the spread of plant diseases and reduces the risk of infections in livestock.
Sodium Hypochlorite in Medical and Healthcare Settings
Hospitals and clinics use sodium hypochlorite as a powerful disinfectant for medical equipment, surfaces, and patient-care areas. It is also used in diluted form for wound irrigation and infection control, making it vital in healthcare environments.
Sodium Hypochlorite in Swimming Pools and Recreational Water Treatment
The use of sodium hypochlorite in swimming pools stops the growth of pathogenic bacteria. In the UK, this substance is used as a swimming pool disinfectant at a concentration range of 1.5-3.0 mg/l or parts per million. The pH level is maintained at either neutral or slightly basic level of 7.6.
Sodium Hypochlorite in Emergency and Disaster Response Applications
In emergency situations such as natural disasters, sodium hypochlorite is used to quickly disinfect water supplies as a water treatment chemical, and helps prevent the outbreak of disease.
Relief organisations often distribute it as a simple, effective water treatment option.
Sodium Hypochlorite in Laboratory and Chemical Manufacturing
In laboratories, sodium hypochlorite serves as a cleaning and sterilising agent for equipment and surfaces. It is also used as a raw material in the production of other chemicals, showcasing its versatility beyond simple disinfection.
Conclusion
Sodium hypochlorite is far more than just a household cleaning ingredient. Its versatility as a disinfectant, bleaching agent, and sanitiser makes it essential in industries ranging from water treatment to healthcare. While it must be handled carefully due to its reactive nature, its ability to protect public health, ensure hygiene, and support critical infrastructure highlights just how important this compound is in both daily life and industrial operations.
