Sodium dichloroisocyanurate dihydrate
[CAS# 51580-86-0]

Identification

• Classification: Chemical reagent >> Organic reagent >> Cyanate ester / isocyanate
• Name: Sodium dichloroisocyanurate dihydrate
• Synonyms: Dichloroisocyanuric acid sodium salt dihydrate; 1,3-Dichloro-1,3,5-triazine-2,4,6(1H,3H,5H)-trione sodium salt dihydrate
• Molecular Formula: C₃Cl₂N₃NaO₃^.2(H₂O)
• Molecular Weight: 255.98
• CAS Registry Number: 51580-86-0
• EC Number: 610-700-3
• SMILES: C1(=NC(=O)N(C(=O)N1Cl)Cl)[O-].O.O.[Na+]

Safety Data

• Hazard Symbols: GHS07;GHS09 Warning
• Hazard Statements: H302-H319-H335-H400-H410
• Precautionary Statements: P261-P264-P264+P265-P270-P271-P273-P280-P301+P317-P304+P340-P305+P351+P338-P319-P330-P337+P317-P391-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H302
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Specific target organ toxicity - single exposure	STOT SE	3	H335

• Transport Information: UN 3077

Discovory and Applicatios

Sodium dichloroisocyanurate dihydrate is an oxidizing disinfectant compound widely used for water treatment, sanitation, and hygiene applications. It is the hydrated form of sodium dichloroisocyanurate (NaDCC), containing two molecules of water per molecule of the active ingredient. The compound belongs to the class of chlorinated isocyanurates, which release free available chlorine upon dissolution in water, functioning as a strong antimicrobial and oxidizing agent. Its disinfecting action is primarily due to the formation of hypochlorous acid (HOCl), which penetrates microbial cell walls and disrupts vital enzymatic and structural functions, leading to cell death.

The development of chlorinated isocyanurates as stable, solid sources of chlorine began in the mid-20th century as a response to the instability and handling difficulties of liquid sodium hypochlorite. Sodium dichloroisocyanurate was introduced as a more stable, concentrated, and transportable alternative to bleach, with the dihydrate form being preferred in certain applications for its improved handling characteristics and reduced dust generation. The hydrated form also shows slightly slower dissolution in water compared to the anhydrous form, which can be advantageous in some controlled-release disinfection processes.

Sodium dichloroisocyanurate dihydrate is widely used in the disinfection of potable water, including emergency water purification in disaster relief and military field operations. Its compact, tablet or granular forms enable easy dosing without specialized equipment, making it suitable for decentralized and low-resource environments. In swimming pool maintenance, it is used to control microbial contamination, prevent algal growth, and maintain residual chlorine levels without the instability issues associated with liquid chlorine solutions. In industrial and institutional cleaning, it is employed for surface disinfection in food processing plants, hospitals, and public facilities, where its broad-spectrum antimicrobial activity helps to control bacteria, viruses, and fungi.

In healthcare and veterinary settings, sodium dichloroisocyanurate dihydrate has been adopted for the safe and effective disinfection of medical instruments, laundry, and surfaces contaminated with blood or other bodily fluids. Its activity against high-risk pathogens, including enveloped and non-enveloped viruses, makes it valuable in outbreak control situations. In household cleaning products, it is incorporated into formulations for kitchen and bathroom sanitation, often as a powdered bleach component that is activated upon contact with water.

An additional area of application is in the food industry, where the compound is used for sanitizing equipment, utensils, and food contact surfaces. In such cases, it is favored for its efficacy at relatively low concentrations, minimal corrosion potential compared to some other oxidizing agents, and reduced formation of chlorinated organic by-products when used under controlled conditions. In agriculture, it is sometimes used to sanitize irrigation systems, greenhouse equipment, and post-harvest washing systems for fruits and vegetables.

From a handling and storage perspective, sodium dichloroisocyanurate dihydrate is considered more stable than sodium hypochlorite, retaining its chlorine content for extended periods when stored in a cool, dry environment. However, it remains an oxidizing substance and should be kept away from organic materials, reducing agents, and sources of heat to prevent decomposition and potential fire hazards. Upon dissolution in water, it gradually decomposes to cyanuric acid and sodium chloride, with the cyanuric acid acting as a chlorine stabilizer, especially in sunlight-exposed applications like swimming pools.

Environmental considerations in the use of sodium dichloroisocyanurate dihydrate include the management of residual chlorine to avoid harmful effects on aquatic life. While it is highly effective in pathogen control, discharge of chlorinated water into natural ecosystems must be regulated to prevent ecological impact. Its solid, stable form and controlled release characteristics continue to make it a preferred choice in many disinfection protocols where portability, storage stability, and ease of use are critical factors.

References

2010. Bathroom Greywater Characterization and Potential Treatments for Reuse. Water, Air, & Soil Pollution, 216(1-4).
DOI: 10.1007/s11270-010-0454-5

1981. Formulation of household automatic dishwasher detergents. Journal of the American Oil Chemists' Society, 58(4).
DOI: 10.1007/bf02541583

1974. Abstracts. Journal of the American Oil Chemists� Society, 51(8).
DOI: 10.1007/bf00000008