WHAT IS IT?
Sodium silicate (Na₂SiO₃), commonly called water glass, is a compound of sodium oxide and silica. It exists as a colourless glass-like solid or in aqueous solution as a viscous, alkaline liquid. The ratio of SiO₂ to Na₂O (the modulus) determines the properties and application.
GRADES BY SiO₂:Na₂O MODULUS
Low modulus (1.6–2.0): More alkaline. Detergent and soap manufacturing.
Medium modulus (2.0–3.0): General industrial use. Adhesives, paper, foundry.
High modulus (3.0–3.5): Less alkaline, more siliceous. Silica gel production, catalysts.
FORMS
Liquid sodium silicate (40–55° Baumé): Most common traded form. Aqueous solution.
Anhydrous solid: Glassy chunks, less common.
Powder (spray-dried): Used in powder detergents.
KEY USES
Detergents: Builder in laundry and dishwasher powders — corrosion inhibitor, alkalinity source
Paper and board: Sizing agent, coating, pulp defibration
Adhesives: Corrugated board, tube winding, labelling
Foundry binders: Sand casting moulds
Construction: Waterproofing concrete, soil stabilisation, fire protection
Silica production: Precipitated silica for tyre rubber and toothpaste
Pigment carrier and catalyst support
TRADE CORRIDORS
Major producers: China (dominant), PQ Corporation (USA), Occidental Chemical
Major buyers: Southeast Asia, Middle East, Africa
Tetra relevance: China → SEA/East Africa corridor. Detergent industry growth in East Africa drives demand.
SPECIFICATIONS (Liquid, Medium Modulus)
SiO₂: 27–30%
Na₂O: 9–11%
Modulus ratio: ~2.5–2.8
Density: 1.38–1.40 g/cm³
Colour: clear to slightly hazy
Iron: max 50 ppm
PACKAGING
ISO tanks or bulk tankers for liquid. Drums (200L) for smaller quantities. Must be kept sealed — CO₂ in air causes surface carbonation.