Sodium Hexafluoro Silicate, Sodium Hexafluorosilicate, Disodium Hexafluoro Silicate, Sodium Hexafluorosilicate, 16893-85-9

Sodium Hexafluorosilicate (Na₂SiF₆)

Basic Identification:

• Chemical Name: Sodium Hexafluorosilicate

• Molecular Formula: Na₂SiF₆

• Molecular Weight: 188.055 g/mol

• CAS Number: 16893-85-9

• Synonyms:

  • Sodium Silicofluoride

  • Sodium Silica Fluoride

  • Disodium Hexafluorosilicate

  • Sodium Fluorosilicate

  • Natrium Hexafluorosilicate

Production Method

Sodium Hexafluorosilicate is produced by neutralizing Fluorosilicic Acid (H₂SiF₆) with a sodium source such as:

• Sodium Hydroxide (NaOH – caustic soda)

• Sodium Carbonate (Na₂CO₃)

• Alternatively, Sodium Chloride (NaCl)

Process Note: Raw material ratios must be carefully controlled to prevent excess fluoride formation.

Physical and Chemical Properties

• Appearance: White granular or hexagonal crystalline solid

• Odor: Odorless

• Density: 2.68–2.70 g/cm³

• Solubility:

  • In water (20 °C): 0.76–0.78 g/100 ml (low solubility)

  • Insoluble in alcohol

  • Soluble in ether

  • Higher solubility in acids compared to water

• Thermal Behavior:

  • Decomposition at 210 °C (melting point)

  • At 300 °C → decomposes into Sodium Fluoride (NaF) and Silicon Tetrafluoride (SiF₄)

• pH Behavior:

  • Aqueous solution is acidic (pH ≈ 3) due to hydrolysis producing Hydrofluoric Acid (HF)

  • At pH 8–8.5 → complete hydrolysis, forming silica gel precipitate

• Hazards on Heating: Releases toxic Hydrogen Fluoride (HF) and Disodium Oxide (Na₂O) fumes

Applications

• Metallurgy:

  • Smelting of beryllium

  • Alloying processes and oxygen-sensitive metal applications

  • Optical industry applications

• Ceramics & Glass:

  • Frits for porcelain and enamel coatings

  • Opal glass production as a corrosion agent

• Refractory Materials:

  • Coagulant in water glass binders

  • Improves density and strength of hardened products

• Chemical Industry:

  • Intermediate in fluoride salt production

  • Additive in zinc, nickel, and iron plating processes

• Polymers & Latex:

  • Coagulant in natural latex production

• Wood & Leather:

  • Preservative agent in protective formulations

• Construction:

  • Moisture absorber in acid-resistant cement production

Safety & Handling

• Hazards: Toxic fumes (HF, Na₂O) upon heating; acidic aqueous solutions

• Storage: Keep in a dry, cool, well-ventilated area; protect from moisture

• Packaging: 25 kg bags

Summary:

Sodium Hexafluorosilicate (Na₂SiF₆) is a versatile inorganic compound with low solubility, high stability, and broad industrial applications. It serves as a silica source, coagulant, and corrosion agent, making it essential in metallurgy, ceramics, glass, construction, and chemical processing. Its dual role as both a hardening agent and silica gel precursor makes it particularly valuable in water glass binder systems.

Sectoral Usage and Application Table – Sodium Hexafluorosilicate (Na₂SiF₆)

Comparison of Alternatives to Sodium Hexafluorosilicate

Key Considerations

• Metallurgy: Aluminum Fluoride and Calcium Fluoride are the closest substitutes.

• Ceramics & Glass: Calcium Fluoride and Hydrofluorosilicic Acid can replace Na₂SiF₆ depending on process.

• Water Treatment: Sodium Fluoride and Hydrofluorosilicic Acid are more common alternatives.

• Latex/Polymer Coagulation: Ammonium Fluorosilicate can serve as a substitute but is less widely used.

Documents

•  
• Betakim COA for Sodium Silicofluoride.pdf
• Sodium Hexafluorosilicate COA.pdf
•