Sodium silicate: Characteristics
The silica-to-soda ratio that decides every grade
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.Sodium silicate is specified by its weight ratio of SiO2 to Na2O, solids content and viscosity. High-ratio (3.2-3.4) neutral grades suit precipitated silica, paper and binders; low-ratio (1.6-2.5) alkaline grades suit detergents and cleaners. Iron content sets colour and suitability for clear products.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Weight ratio SiO2:Na2O | about 1.6-3.5; neutral grades about 3.2-3.4 (indicative) | Sets alkalinity, reactivity and end use | Industry grades (indicative) |
| Solids content | solutions about 35-50% (indicative) | Freight and viscosity | Indicative |
| Viscosity | from about 100 to over 1,000 mPa.s depending on ratio and solids (indicative) | Handling and dosing | Indicative |
| Iron content | typically under about 0.05% Fe2O3 for clear grades (indicative) | Colour of silica and detergents | Indicative |
Commercial grades
- Neutral liquid (ratio about 3.3) for precipitated silica and paper
- Alkaline liquid (ratio about 2) for detergents
- Glass lumps
- Spray-dried powder
- Sodium metasilicate pentahydrate and anhydrous