Chemical & Physical Properties
The compound presents as a white to grayish granular solid with a characteristic chlorine odour. It has a density of 2.35 g/cm³ at 20°C and decomposes at 100°C. Solubility in water is approximately 21 g/100 mL at 25°C, though dissolution is relatively slow and decreases in hard water due to calcium and magnesium ions. Aqueous solutions are highly alkaline, with pH typically ranging from 10 to 12.
What distinguishes calcium hypochlorite from its primary liquid counterpart, sodium hypochlorite (NaOCl), is thermodynamic stability in the solid state. This enables commercial formulations with available chlorine content ranging from 65% to 73% by weight, compared to just 5–13% for standard sodium hypochlorite solutions. In practical terms, one gram of 65% strength calcium hypochlorite delivers oxidizing capability equivalent to 0.65 grams of chlorine gas.
Manufacturing Process
Commercial production typically involves the chlorination of an aqueous slurry of lime (calcium hydroxide) with chlorine gas. The reaction produces calcium hypochlorite crystals in a hypochlorite mother liquor, which are then recovered, washed, and dried. Two primary manufacturing routes exist: the sodium process, which currently dominates with approximately 77.65% of market share due to cost efficiency and suitability for large-scale production, and the calcium process, which produces a more stable dry product.
Key Applications
Water Treatment: Calcium hypochlorite serves as a primary disinfectant for potable water, particularly in smaller treatment plants and emergency response scenarios. Typical doses range from 1 to 5 mg/L as available chlorine. Studies have demonstrated its efficacy against a broad spectrum of bacterial pathogens, including E. coli, Staphylococcus aureus, and Klebsiella pneumoniae.
Swimming Pool Sanitation: The compound is widely used for pool disinfection and algae control. It can be applied as granular broadcast treatment or via tablets placed in skimmers or dissolving baskets. Shock dosing is employed when visible algae blooms occur.
Industrial Bleaching: In the pulp and paper industry, calcium hypochlorite bleaches wood pulp. In textiles, it is used to bleach cotton, hemp, and silk fibres.
Wastewater and Industrial Effluent: The compound disinfects treated effluent prior to discharge.
Market Dynamics
The global calcium hypochlorite market was valued at approximately USD 814.2 million in 2025 and is projected to reach USD 1,317.3 million by 2034, representing a CAGR of 5.50%. Asia-Pacific currently dominates with roughly 39–44% of global market share, driven by strong demand from water treatment infrastructure and industrial applications. Major industry players include Olin Corporation, Tosoh Corporation, Lonza Group, Nippon Soda, and Aditya Birla Chemicals.
Transportation & Classification
Calcium hypochlorite is classified as a Division 5.1 oxidizing substance under the IMDG Code. Depending on available chlorine content and moisture levels, it is assigned to one of nine UN entries, the most common being UN 1748 (dry, >39% available chlorine), UN 2208 (mixture, 10–39% available chlorine), and UN 2880 (hydrated, 5.5–16% water). Cargoes should be carried on deck only, out of direct sunlight and clear of living quarters. The primary HS code is 2828100000.
Storage & Handling
Under normal dry storage conditions, calcium hypochlorite loses approximately 0.013% of its strength per day. When stored dry at 23°C ± 2, the product remains stable for at least 24 months with ≤5% degradation. However, decomposition accelerates with exposure to heat, moisture, and sunlight. The compound reacts vigorously with acids to release toxic chlorine gas and is incompatible with organic materials, ammonia, amines, and finely divided metals.
Conclusion
Calcium hypochlorite remains an indispensable chemical across water treatment, sanitation, and industrial processing sectors. Its high available chlorine content, solid-state stability, and cost-effectiveness ensure continued demand, particularly as global water quality regulations tighten and infrastructure expansion accelerates across developing economies.
