Sodium Metasilicate

Sodium metasilicate (Na_2SiO_3) is a silicate compound produced by the reaction of silicon dioxide and sodium carbonate at high temperatures. Products based on this compound are widely used in industry due to their pronounced alkaline, detergent, and binding properties.

The key difference between the main forms of sodium metasilicate lies in the presence or absence of water of crystallization. This directly affects the physicochemical characteristics of the material and its fields of application. At STEKLOLUX, we take these differences into account when selecting the right product for our customers' specific technological requirements.

1.1. Structure and Composition
Sodium Metasilicate Pentahydrate (Na_2SiO_3 \cdot 5H_2O)
This is a crystalline hydrate in which water molecules are tightly bound within the crystal lattice. The mass fraction of water is approximately 44.5%. This structure ensures stability during storage and transportation. The material maintains its physical form up to temperatures of around +48 °C, at which point the crystals begin to melt.
Anhydrous Sodium Metasilicate (Na_2SiO_3)
This is an amorphous powder free of water of crystallization. It is highly hygroscopic (up to 32%), which requires strict adherence to storage conditions. Its melting point reaches 1088 °C, making the material suitable for use in high-temperature technological processes.
1.2. Reactivity
The forms of sodium metasilicate behave differently when interacting with water:

• Pentahydrate form: Dissolves faster, forming stable solutions with a pH of 12–13. Solubility at 20 °C reaches 160 g per 100 ml of water.
• Anhydrous form: Upon contact with water, it undergoes an exothermic hydration reaction. Dissolution occurs more slowly; however, the resulting alkalinity of the solution is higher, with a pH of 13–14.

2.1. Sodium Metasilicate Pentahydrate
Primary fields of application:

• Household and Industrial Chemicals: Used as a key ingredient in laundry powders and detergents. Its crystalline structure significantly reduces dust formation during the packaging process.
• Textile Industry: Employed to stabilize pH levels during bleaching and fabric treatment. It offers excellent shelf life without caking.
• Metal Surface Treatment: Utilized in priming and pretreatment compounds. The presence of hydration water helps mitigate the risk of corrosion in aluminum alloys.

Limitations:

• Not recommended for technological processes where minimal moisture content is critical.

2.2. Anhydrous Sodium Metasilicate
Key application areas:

• Construction Materials: Acts as a hardening accelerator and activator in acid-resistant concretes and dry building mixes.
• Ceramics Industry: Used as a flux to lower firing temperatures (down to ~800 °C), preventing the deformation of ceramic workpieces.
• Pulp and Paper Industry: Employed in the delignification of pulp, enhancing the efficiency of the alkaline pulping process.

Technical Requirements:

• Strict protection from moisture is mandatory during all stages of storage and transportation.

When to choose pentahydrate metasilicate

• Production of liquid detergents
• Processes at temperatures up to 45 °C
• Working with non-ferrous metals
• Manual dosing and packaging

When anhydrous metasilicate is preferred

• Dry chemical compositions
• High-temperature processes
• Systems with controlled humidity
• Formulations with minimal water content

STEKLOLUX approach
STEKLOLUX selects the form and characteristics of sodium metasilicate according to the customer's specific technological conditions, taking into account the industry, temperature regimes, humidity requirements, and compatibility with other components.