Overview
Sodium metasilicate (CAS 6834-92-0 ), also sold under the E-number E550 , is an inorganic alkali salt used across industrial cleaning, water treatment, and surface processing operations.
It functions primarily as a builder, pH regulator, and corrosion inhibitor in formulated products and process chemicals. In industrial and institutional cleaning, it acts as a detergent builder.
This chemical boosts alkalinity, sequesters hardness ions, and improves soil removal in heavy-duty formulations. Textile and leather processors use it to prepare fiber surfaces and control bath pH.
It is also utilized during scouring and dyeing to improve dye uptake consistency. Water treatment operations apply it as a corrosion inhibitor for metal pipelines to protect iron and steel surfaces.
The compound forms a protective silicate film on these surfaces to prevent degradation. Pulp and paper producers incorporate it into bleaching and sizing processes to stabilize peroxide bleach.
It is also used to control effluent pH in paper manufacturing. Sodium metasilicate is supplied as an anhydrous powder or pentahydrate granules, with the pentahydrate form being the most common.
Technical grade is the standard offering for industrial use, with food-grade material available under the E550 designation for indirect contact or food-processing applications.
Bulk supply is typically available in bags or bulk sacks. The product is specified by its silica-to-sodium oxide ratio and total alkalinity content for various industrial requirements.
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Physical Properties
| Melting Point | 1089 °C |
| Density | 2.614 g/cm³ |
| Appearance | White, granular powder. Soluble in water; p H of 1% solution 12.7. Noncombustible. |
| Color | White |
| Form | powder |
| Water Solubility | Soluble in cold water. Hydrolyzes in hot water. Insoluble in acids, alcohol and salt solutions. |
| Refractive Index | nD25 (glass) 1.520 |
| pH | 11(1 mM solution);11.91(10 mM solution);12.62(100 mM solution) |
Safety & Handling
Danger GHS05 GHS07 GHS08 Hazard Statements H314 Causes severe skin burns and eye damage [Danger Skin corrosion/irritation] H335 May cause respiratory irritation [Warning Specific target organ toxicity, single exposure; Respiratory tract irritation] H302 Harmful if swallowed [Warning Acute toxicity, oral] H318 Causes serious eye damage [Danger Serious eye damage/eye irritation] H371 May cause damage to organs [Warning Specific target organ toxicity, single exposure]
Trade & Regulatory
| HS Code | 28391910 |
| UN Number | 3253 |
| ADR Class | 8 |
| Packing Group | III |
| Storage Class | 8B - Non-combustible corrosive hazardous materials |
| WGK (Germany) | 1 |
Other Names
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Chemical Properties
- CAS Number
- 6834-92-0
- EC Number
- 229-912-9
- Mol. Weight
- 122.063
- HS Code
- 28391910
- Category
- Alkalis & Bases