Sodium Dichloroisocyanurate (SDIC)

Sodium Dichloroisocyanurate (SDIC), also known as Sodium Troclosene or NaDCC, is a broad-spectrum, stable, fast-acting oxidizing biocide and disinfectant. It is widely used in water treatment, industrial biocidal control, sanitation, and textile bleaching.

Chemical & Physical Properties

Chemical Formula: C3Cl2N3NaO3

CAS Number: 2893-78-9 (Anhydrous), 51580-86-0 (Dihydrate)

Available Chlorine Content: 56% – 60% (Anhydrous) or 55% (Dihydrate)

Solubility in Water: High (30 g/100mL at 25°C)

pH (1% aqueous solution): 5.5 – 7.0 (near-neutral, making it significantly less corrosive and gentler on equipment than sodium hypochlorite)

Mechanism of Action

High Efficacy: Hypochlorous acid (HClO) is up to 80 times more effective at cell membrane penetration and oxidation than hypochlorite ions (ClO-).

Self-Stabilizing Effect: The cyanuric acid byproduct acts as a stabilizer, shielding free chlorine from rapid UV degradation under direct sunlight.

Key Applications

Field Typical Use & Function

Industrial Water Treatment Controls algae, bacteria, and bio-slime in recirculating cooling towers and industrial process water systems.

Disinfection & Sanitation Emergency drinking water purification, swimming pool disinfection, and hospital/surface sterilization.

Textile Industry Used as an anti-shrink treatment agent for wool and a mild, high-efficiency oxidative bleaching agent.

Agriculture & Aquaculture Disease control in fish farms, poultry farm sanitation, and seed disinfection.

Comparison: SDIC vs. Liquid Bleach (Sodium Hypochlorite)

Stability & Shelf Life: Solid SDIC (powder/granules/tablets) maintains active chlorine levels for years, whereas liquid sodium hypochlorite degrades rapidly during storage.

pH Control: Dissolved SDIC yields a nearly neutral solution (~pH 6.0–6.5), maximizing active HClO concentration without requiring heavy acid dosing to lower the pH.

Handling Safety: Lower shipping bulk, safer handling, and non-corrosive storage compared to bulk liquid hypochlorite.

Storage & Handling Warning: Store in a cool, dry, well-ventilated area away from direct sunlight, moisture, and organic materials. Do not mix with acids, ammonia compounds, or h3 reducing agents, as doing so releases toxic chlorine gas ($\text{Cl}_2$).