SDIC (Sodium Dichloroisocyanurate) is a widely used chlorine-based disinfectant and bleaching agent. Its main components and key properties are as follows:
1. Primary Active Ingredient
- Sodium Dichloroisocyanurate (C₃Cl₂N₃NaO₃)
- Chemical Structure: A stabilized chlorine compound containing two active chlorine atoms.
- Available Chlorine: ~60–62% (higher than bleach or calcium hypochlorite).
- Forms:
- Anhydrous powder (most common).
- Dihydrate (SDIC·2H₂O): Slower dissolution, used in tablets.
2. Secondary Components (Additives)
| Component | Function |
|---|---|
| Sodium chloride (NaCl) | Common filler to standardize chlorine content. |
| Sodium carbonate (Na₂CO₃) | Stabilizes pH (~6–7) to reduce corrosion and chlorine loss. |
| Boric acid (H₃BO₃) | Enhances stability in humid conditions (prevents caking). |
| Lubricants (e.g., Mg stearate) | Used in tablet forms for slow dissolution. |
3. Key Chemical Reactions
- Disinfection Mechanism: Releases hypochlorous acid (HOCl) in water:C₃Cl₂N₃NaO₃+H₂O→HOCl+Cyanuric Acid+Na+
- HOCl kills bacteria/viruses by oxidizing cell membranes.
- Cyanuric Acid Byproduct: Acts as a stabilizer in outdoor pools (but excess can reduce efficacy).
4. Technical Specifications
| Parameter | Typical Value | Test Method |
|---|---|---|
| Active Chlorine | ≥55–60% (anhydrous) | GB/T 10666 (iodometric titration) |
| pH (1% solution) | 5.5–7.0 | pH meter (ISO 4316) |
| Solubility | ~25 g/100 mL (20°C) | Gravimetric method |
| Moisture | ≤1.0% (anhydrous) | Karl Fischer titration |
5. Major Applications
- Water Treatment:
- Drinking water, swimming pools, wastewater disinfection.
- Household/Industrial Cleaning:
- Bleaching agent in detergents, mildew removers.
- Agriculture:
- Sterilizing livestock farms, seed treatment.
- Food Industry:
- Surface sanitization (low-concentration rinses).
6. Safety & Handling
- Storage: Keep dry (hygroscopic) and away from acids/ammonia (toxic chlorine gas risk).
- Decomposition: Avoid heat (>250°C) to prevent release of cyanogen chloride (ClCN).
- Regulations:
- WHO approves SDIC for drinking water (<5 mg/L free chlorine residual).
- FDA 21 CFR §178.1010 permits food-contact surface sanitization.
Comparison with Other Chlorine Agents
| Agent | Active Cl% | Stability | pH Impact | Typical Use |
|---|---|---|---|---|
| SDIC | 55–60% | High | Neutral | Pools, drinking water |
| Calcium Hypochlorite | 65–70% | Moderate | Alkaline | Large-scale water treatment |
| Sodium Hypochlorite (Bleach) | 5–12% | Low | Alkaline | Household disinfection |
Conclusion
SDIC’s high chlorine content, stability, and neutral pH make it superior for controlled disinfection. Its tablet form is popular for pool maintenance, while powdered SDIC is used in industrial sanitation. Always follow dosage guidelines (e.g., 2–10 mg/L for drinking water) to avoid over-chlorination.