What is Sodium Hypochlorite?

Sodium hypochlorite is a chemical compound with the formula NaClO. It is a pale yellow or greenish-yellow liquid with a chlorine odor. It is produced by the reaction of chlorine gas (Cl₂) with sodium hydroxide (NaOH) solution, according to the following equation:

Cl₂ (g) + 2 NaOH (aq) → NaClO (aq) + NaCl (aq) + H₂O (l)

In this reaction, chlorine gas reacts with hydroxide ions (OH⁻) from sodium hydroxide to form hypochlorite ions (ClO⁻) and chloride ions (Cl⁻). Sodium hypochlorite is produced in large quantities by this process for use in various applications.

properties of sodium hypochlorite

Physical Properties:

• Color: Colorless or slightly yellow liquid (solution) or pale greenish-yellow solid (pentahydrate form)
• Odor: Disagreeable, chlorine-like odor
• Boiling Point: 111°C (in solution) or 18°C (pentahydrate)
• Melting Point: 18°C (pentahydrate)
• Solubility: Highly soluble in water (29.3 g/100 g at 0°C)
• Density: 1.093 g/mL (5% solution) to 1.21 g/mL (14% solution)

Chemical Properties:

• Strong Oxidizing Agent: Decomposes to release chlorine, which disinfects and bleaches.
• Unstable: Decomposes over time, especially in warm temperatures and sunlight, releasing chlorine gas.
• Basic Solution: Aqueous solutions have a pH of 11 or higher due to the formation of hypochlorous acid (a weak acid).
• Reacts with Acids: Can form chlorine gas or hypochlorous acid depending on the acid.

VARIOUS GRADES OF sodium hypochlorite

• Reagent Grade: Boasts the highest purity, typically ranging from 10-15% available chlorine. Due to its reliable composition, this grade finds use in laboratories for analytical procedures and scientific research.
• Technical Grade: As the name suggests, this grade is suited for industrial applications. Technical grade sodium hypochlorite has a slightly lower purity than reagent grade, typically containing 10-13% available chlorine. It’s commonly used in various industrial processes like textile bleaching, pulp and paper manufacturing, and water treatment facilities.
• Food Grade: This specialized grade adheres to strict regulations for safe use in food processing, typically containing 10-15% available chlorine. Food grade sodium hypochlorite plays a crucial role in sanitizing food contact surfaces and ensuring the hygienic washing of fruits and vegetables.
• Swimming Pool Grade: This is the most widely encountered form, containing the lowest concentration of available chlorine, typically ranging from 3-8%. Due to its lower concentration, swimming pool grade sodium hypochlorite is generally considered safe for household applications like disinfecting swimming pools and general sanitation tasks.
• Available Chlorine: This term refers to the percentage of chlorine readily available to perform disinfection or bleaching. It’s a critical factor when choosing the appropriate grade for your needs. For instance, higher available chlorine concentrations provide a stronger disinfection effect but may require more careful handling due to increased reactivity.

Application and uses of Sodium hypochlorite

Disinfection:

• Healthcare: Sodium hypochlorite is a workhorse disinfectant in hospitals and medical facilities. It effectively sterilizes surfaces, equipment, and instruments, playing a vital role in preventing the spread of infections and maintaining hygiene in patient care areas. Its efficacy against a broad spectrum of bacteria, viruses, and fungi makes it a valuable tool for healthcare professionals.
• Water Treatment: Municipal water treatment plants rely on sodium hypochlorite as a primary disinfectant to eliminate harmful microorganisms from drinking water supplies. It’s particularly effective against bacteria like E. coli that can cause waterborne illnesses. The controlled application of sodium hypochlorite ensures safe and clean drinking water for communities.
• Food Processing: Food safety is paramount, and food processing facilities utilize food-grade sodium hypochlorite to sanitize food contact surfaces and wash fruits and vegetables. This helps prevent contamination and the spread of foodborne pathogens that can cause illness. Regulations govern the use of sodium hypochlorite in food processing to ensure safe application within specified concentration limits.

Bleaching:

• Textile Industry: Sodium hypochlorite plays a significant role in the textile industry for bleaching fabrics and textiles, achieving a brighter and whiter appearance. It breaks down colored pigments within the fabric, allowing for a more uniform and aesthetically pleasing look. The specific concentration and application method used depend on the desired level of whiteness and the type of fabric being treated.
• Pulp and Paper Manufacturing: In pulp and paper manufacturing, NaClO is a key bleaching agent for wood pulp. It lightens the color of the pulp, creating a base material suitable for paper production. The bleaching process helps to achieve the desired brightness and opacity of the final paper product.

Other Applications:

• Swimming Pool Sanitation: Household bleach, a diluted form of sodium hypochlorite, is a familiar sight for pool owners. Regular application helps maintain swimming pool hygiene by killing bacteria and algae that can cloud the water, cause odors, and irritate swimmers’ skin. The appropriate amount of chlorine needs to be maintained to ensure swimmer safety and prevent excessive irritation.
• Deodorizing: Due to its oxidizing properties, NaClO can be used as a deodorizer to eliminate some odors. It breaks down odor-causing compounds, although proper ventilation is crucial when using it for this purpose. However, it’s important to note that it may not be effective for all types of odors, and other odor-eliminating solutions might be more suitable in certain situations.
• Wastewater Treatment: Municipal wastewater treatment facilities often utilize NaClO as a disinfectant during the treatment process. It helps to inactivate harmful pathogens before the treated wastewater is released into the environment. Regulations and best practices guide the use of sodium hypochlorite in wastewater treatment to ensure effective disinfection while minimizing environmental impact.

SAFETY tips of Sodium hypochlorite

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• Personal Protective Equipment (PPE): Always wear gloves, eye protection (safety goggles or a face shield), and long sleeves when handling sodium hypochlorite. This minimizes the risk of skin and eye irritation from splashes or accidental contact.
• Ventilation: Ensure adequate ventilation in the workspace. Open windows and doors or use exhaust fans to prevent inhaling chlorine fumes, which can irritate the respiratory system.
• Never Mix with Other Chemicals: can react violently with certain chemicals, such as acids or ammonia, releasing toxic fumes. Always store and use NaClO away from other cleaning products.
• Labeling and Storage: Keep sodium hypochlorite in its original, labeled container. Store it in a cool, dark place out of reach of children and pets. Never transfer bleach to unmarked containers, as accidental ingestion can be dangerous.
• Spills and Leaks: If a spill occurs, clean it up promptly. Wear gloves and eye protection. For small spills, dilute the bleach with water and absorb it with a paper towel. For larger spills, you may need to consult safety data sheets (SDS) for specific cleanup procedures.
• Disposal: Don’t pour leftover sodium hypochlorite down the drain. Most communities have guidelines for proper disposal of household hazardous waste. Dilute small amounts with water before disposal according to local regulations.
• Concentrations: Be mindful of the concentration of sodium hypochlorite you’re using. Higher concentrations require more caution due to increased reactivity. Follow recommended dilution ratios for specific applications.
• Don’t mix concentrated solutions: Never mix concentrated bleach solutions together. This can generate excessive heat and toxic fumes.

Sodium hypochlorite Packing

High-Density Polyethylene (HDPE) Containers: This is the industry standard for commercial bleach. HDPE is a strong, non-reactive plastic that resists corrosion from sodium hypochlorite. Containers range in size from small bottles to large drums and IBC totes (Intermediate Bulk Containers).

 

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