Sodium silicofluoride grades fall into three practical categories—technical, water-treatment (commonly specified to NSF/ANSI/CAN 60 and AWWA B703), and ceramic/enamel grade—differentiated mainly by purity, particle size control, and the standard a producer certifies against. Buyers selecting a grade should match the certification requirement of the end application, not just the assay number on the certificate of analysis.
What Is Sodium Silicofluoride?
Sodium silicofluoride (sodium fluorosilicate, Na2SiF6, CAS 16893-85-9) is a white, odourless crystalline powder with limited water solubility (roughly 0.44 g per 100 mL at 25°C, rising modestly with temperature). It is produced as a co-product of fluorosilicic acid recovered from phosphate fertiliser processing, reacted with a sodium source to precipitate the fluorosilicate salt. The material is thermally unstable above roughly 500°C, decomposing to release silicon tetrafluoride and sodium fluoride, and it reacts with strong acids to liberate hydrogen fluoride and silicon tetrafluoride gas — a property that governs most of its handling precautions.
Sodium Silicofluoride Grades, Specifications and Standards
Across the three commercial grades, the defining differences are purity floor, particle size distribution, and the external standard a batch is certified against. Water-treatment grade is the most tightly controlled because it enters potable water supply chains and is typically supplied with batch-specific NSF/ANSI/CAN 60 certification documentation and conformance to AWWA B703 compositional limits. Technical grade serves non-potable industrial uses where a tighter external standard is unnecessary. Ceramic and enamel grade is distinguished less by chemical purity and more by a controlled, fine particle size suited to opacifying glaze and frit formulations.
| Grade | Typical Na2SiF6 Purity | Standard / Specification | Primary Use |
|---|---|---|---|
| Technical Grade | ≥98% | Producer technical specification | Wood preservation, textile laundry souring, concrete surface hardeners |
| Water Treatment Grade | ≥98.5% | NSF/ANSI/CAN 60; AWWA B703 | Municipal drinking-water fluoridation |
| Ceramic / Enamel Grade | ≥98%, controlled mesh size | Producer internal particle-size specification | Opacifier in vitreous enamels and ceramic frits |
Applications Across Industries
In municipal water treatment, sodium silicofluoride is metered into supply systems as a fluoridating agent, dosed via saturator systems because of its limited solubility. In ceramics and metal finishing, it functions as an opacifying agent in vitreous enamel frits and glazes, contributing opacity and surface hardness to fired coatings. In wood treatment it acts as a preservative additive protecting against fungal and insect attack in structural timber. Textile and laundry operations use it as a souring agent to neutralise residual alkalinity after bleaching or mercerising steps. It also appears as a hardening additive in concrete floor treatments, where it reacts with free lime at the surface to densify the wear layer.
Handling, Storage and Processing Notes
Sodium silicofluoride should be stored in a dry, well-ventilated area, segregated from strong acids and from heat sources, since both acid contact and elevated temperature can liberate hazardous fluorine-containing gases. Standard industrial packaging is 25 kg or 50 kg multi-wall paper or woven PP bags with a polyethylene liner; bulk users commonly source 500–1,000 kg FIBC bulk bags to reduce per-unit handling. Dust control (local exhaust, respiratory protection) is standard practice during bag opening and transfer, and operators should avoid conditions that generate airborne fines. Because the salt is only slightly soluble, dissolution and dosing equipment for water treatment applications is typically designed around saturator tanks rather than simple in-line mixing.
QA Documentation and Sourcing Considerations
Buyers should request a certificate of analysis confirming Na2SiF6 assay, free acidity, heavy-metal and arsenic limits where applicable, and particle size data for ceramic-grade material. For water-treatment grade, batch-specific NSF/ANSI/CAN 60 certification and conformance to AWWA B703 limits are the documents typically requested by municipal buyers and their engineering consultants. Lot traceability back to the production batch, along with a current safety data sheet, supports both regulatory audits and internal quality systems. Because the raw material stream originates from phosphate processing by-products, buyers sourcing larger volumes should qualify more than one supplier to maintain continuity of specification across the production chain.
FAQ
What is the difference between technical grade and water treatment grade sodium silicofluoride?
Water treatment grade is produced and certified to meet NSF/ANSI/CAN 60 and AWWA B703 requirements for potable water additives, with batch-level documentation. Technical grade meets a producer's internal specification for non-potable industrial applications and does not carry potable-water certification.
How is sodium silicofluoride typically packaged for shipment?
Standard packaging is 25 kg or 50 kg multi-wall bags with a polyethylene liner; larger-volume buyers commonly order 500–1,000 kg FIBC bulk bags to reduce handling and packaging costs per tonne.
Why does sodium silicofluoride need to be kept away from acids during storage?
Contact with strong acids, or exposure to high heat, can decompose the salt and release silicon tetrafluoride and hydrogen fluoride gases, both of which require controlled ventilation and appropriate handling procedures.
How DIC Supports This
DIC maintains regional stock of sodium silicofluoride across technical and water-treatment grades, with documentation packages — certificates of analysis, safety data sheets, and lot traceability records — prepared to match the certification level each application requires. Vendor-managed inventory programs are available for buyers with steady, recurring consumption, helping maintain continuity of supply specification across production runs.
