Description
Sodium metasilicate (Na2SiO3) is a type of sodium silicate with a specific chemical composition where the molar ratio of sodium oxide (Na2O) to silicon dioxide (SiO2) is 1:1. It is a highly alkaline, inorganic compound sold as an anhydrous (water-free) powder or in hydrated forms (e.g., pentahydrate and nonahydrate) as a granular solid. It is also a key component in commercial “water glass” solutions.
Key Properties
| Property | Details |
| Chemical Name | Sodium Metasilicate |
| Chemical Formula | Na₂SiO₃ (anhydrous form) |
| CAS Number | 6834-92-0 (pentahydrate) / 10213-79-3 (anhydrous) |
| Molecular Weight | ~122.06 g/mol (anhydrous), ~212.14 g/mol (pentahydrate) |
| Physical State | Solid (powder/granular) or aqueous solution |
| Appearance | White, crystalline powder or colorless solution |
| Odor | Odorless |
| Solubility in Water | Highly soluble |
| pH (1% solution) | ~12.4 – 13.2 (strongly alkaline) |
| Melting Point | ~1,088°C (anhydrous) |
| Boiling Point | Decomposes before boiling |
| Density | ~2.4 g/cm³ (solid) |
| Reactivity | Reacts with acids to form silica and salt; can corrode aluminum, zinc, etc. |
| Corrosiveness | Corrosive to skin, eyes, and mucous membranes |
| Toxicity | Low acute toxicity but causes severe irritation or burns |
| Stability | Stable under normal conditions; avoid contact with acids |
Common Uses
Sodium metasilicate is a versatile and powerful industrial chemical used in a variety of applications, primarily in cleaning and manufacturing.
Detergents and Cleaners: This is its most common application. It acts as a builder in laundry detergents, dishwashing detergents, and industrial cleaners. It enhances the cleaning power of surfactants by inactivating hard water minerals and provides a buffering action to maintain an alkaline pH.
Pulp and Paper: It’s used in the de-inking process for recycled paper and as a bleaching aid.
Adhesives: It serves as a low-cost, strong adhesive in some industrial applications.
Ceramics: In ceramics, it’s used as a deflocculant to improve the fluidity of clay slips.
Metal Cleaning: Due to its strong alkaline nature and corrosion inhibition properties, it is used in formulations for cleaning and degreasing metal surfaces.
Grades of sodium metasilicate:
Anhydrous Sodium Metasilicate : Anhydrous means “without water.” This grade is a pure, water-free form of sodium metasilicate.
Sodium Metasilicate Pentahydrate This is a hydrated form of sodium metasilicate, containing five water molecules for every one molecule of sodium metasilicate.
Sodium Metasilicate Nonahydrate This is another hydrated form, containing nine water molecules per molecule of sodium metasilicate. It is less common than the pentahydrate form but offers even faster dissolution.
Purity Grades In addition to the hydration-based grades, sodium metasilicate is also categorized by its purity for different applications:
Technical/Industrial Grade: The most common grade, with a purity suitable for general industrial uses like detergents, paper de-inking, and water treatment.
Reagent Grade: A higher-purity grade for laboratory and analytical applications, with a certified chemical assay and specified low levels of impurities.
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