Industrial chemicals · Taylor, TXTechnical Data Sheet
Technical Data Sheet
Hydrofluorosilicic Acid 23% (HFS)
Technical · 23%
- CAS number
- 16961-83-4
- UN number
- UN1778
- Hazard class · packing group
- 8 · PG II
- Structure
Structure · PubChem - Grade
- Technical · 23%
- Signal word
- Danger
- Hazards
- Proper shipping name
- Fluorosilicic acid
Last reviewed 2026-07-17 by Andre Taki, Chief Commercial Officer.
Identity & Composition
- Product Name
- Hydrofluorosilicic Acid 23% (HFS)
- Alliance Code
- hydrofluorosilicic-acid-23-hfs
- Grade
- Technical
- Concentration
- 23%
- CAS Number
- 16961-83-4PubChem
- Formula
- H2SiF6Adjudicated
- Molecular Weight
- 144.09 g/molAdjudicated
- Product Type
- Solution
Specifications
| Test | Specification | Typical | Method | Source |
|---|---|---|---|---|
| Assay (H2SiF6) | 23.0 % min. | 23.8 % | — | Interpreted |
| Free acid (HF) | 1.0 maximum % | 0.31 % | — | Interpreted |
| Heavy Metals (as lead, Pb) | <0.02% | 0.00064 % | — | Interpreted |
| Suspended matter | clean and free of visible suspended matter | Passes test | — | Interpreted |
| Arsenic (As) | 10 mg/kg maximum | 1.3 mg/kg | ICP-MS | Interpreted |
| Sulfate (SO4) | 0.5 % maximum | 0.17 % | Ion chromatography / gravimetric (BaSO4) | Interpreted |
Values are reproduced from the current product reference. Source labels do not by themselves establish a supplier guarantee or a test result for your lot. Confirm applicable acceptance limits and request lot-specific documentation.
Available GradesSame CAS, alternate grades and concentrations
| Grade | Concentration | Typical Assay | SKU | TDS |
|---|---|---|---|---|
| This grade Technical | 23% | — | current | current |
| ACS Grade | 23% | — | hydrofluorosilicic-acid-23-acs | View TDS → |
Typical assay shown is the rolling-window mean from the sibling product's most recent lots. Grade selection drives downstream end-use — verify the sibling grade matches your specification before substitution.
Physical & Chemical Properties
| Property | Value | Source |
|---|---|---|
| Appearance | Colorless, fuming liquid | Adjudicated |
| Form | Liquid | Published reference |
| Color | water white to straw yellow | Interpreted |
| Odor | Pungent, acrid | Adjudicated |
| pH | Below 1 as supplied (strong acid); 1.5–2 as a 10% solution | Adjudicated |
| Specific Gravity | 1.185–1.215 at 15.6 °C (water = 1) | Adjudicated |
| Density | 1.19 (23% w/w aqueous solution, 20 °C) | Published reference |
| Boiling Point | Approx. 106–108 °C (223–227 °F); decomposes | Adjudicated |
| Melting Point | -20 to -16 °C (-4 to 3 °F), freezing point (aqueous solution) | Adjudicated |
| Flash Point | Not applicable | Adjudicated |
| Vapor Pressure | 17–24 mmHg at 20–25 °C | Adjudicated |
| Solubility (water) | Completely miscible with water | Adjudicated |
Strong acid — density and vapor-pressure values shown are at 20 °C; values shift markedly with concentration and temperature. Reference concentration-temperature curves before specifying equipment.
Materials of Construction
| Material | Rating | Conditions | Source |
|---|---|---|---|
| polyethylene | Compatible | — | s3.amazonaws.com |
| cross-linked high-density polyethylene (with UV stabilizer) | Compatible | polyethylene must be high-density, cross-linked, with a minimum of 0.25 percent ultraviolet stabilizer | s3.amazonaws.com |
| rubber-lined steel | Compatible | — | s3.amazonaws.com |
| glass | Not recommended | — | s3.amazonaws.com |
| ceramics | Not recommended | — | s3.amazonaws.com |
| steel (unlined) | Not recommended | — | s3.amazonaws.com |
| concrete | Not recommended | — | s3.amazonaws.com |
| wood | Not recommended | — | s3.amazonaws.com |
| rubber lining / saran | Compatible | source product is a 23-25 % H2SiF6 aqueous solution (TDS typical analysis 23.5 %) | cdn-contenu.quebec.ca |
| polyethylene shipping containers (vs. glass carboys) | Compatible | 23-25 % H2SiF6 aqueous solution per the TDS typical analysis | cdn-contenu.quebec.ca |
| high-density, cross-linked polyethylene | Compatible | — | s3.amazonaws.com |
| unlined steel | Not recommended | — | s3.amazonaws.com |
Compatibility is drawn from published manufacturer and supplier documentation for this product; each rating is sourced. Confirm against your specific duty cycle before equipment selection.
Regulatory & Transport
DOT / 49 CFR
- UN Number
- UN177849 CFR 172.101
- Hazard Class
- 8Adjudicated
- Packing Group
- IIAdjudicated
- Proper Shipping Name
- Fluorosilicic acidAdjudicated
GHS / OSHA HCS 2024
- Signal Word
- DangerAdjudicated
- H-Codes (Hazard Statements)
- H290, H302, H311, H314, H332Adjudicated
- P-Codes (Precautionary Statements)
- P234, P260, P262, P264, P270, P271, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P362, P363, P390, P405, P406, P501Adjudicated
Occupational Exposure Limits
- OSHA PEL (29 CFR 1910.1000)
- 2.5 mg/m³ TWA (F)Adjudicated
- ACGIH TLV
- 2.5 mg/m³ TWA (fluorides, as F); hydrogen fluoride 0.5 ppm TWA, 2 ppm ceiling (as F)Adjudicated
- NIOSH REL
- 2.5 mg/m³ TWA (F)Adjudicated
- NIOSH IDLH
- 250 mg/m³ (F)Adjudicated
Transport descriptions reflect 49 CFR 172.101 lookup at time of publication. Sourced data: NIOSH Pocket Guide for REL/IDLH, OSHA Z-Tables for PEL. Always verify against the latest regulatory text before shipment-critical decisions.
Health & Fire Hazard
Acute Toxicology
- LD₅₀ Oral (rat)
- 125–430 mg/kg (fluorosilicic acid); product ATE about 390–500 mg/kgAdjudicated
- LD₅₀ Dermal (rabbit)
- Product ATE (dermal) about 375–500 mg/kgAdjudicated
- LC₅₀ Inhalation (rat, 4 h)
- 1.11 mg/L (fluorosilicic acid, 1 h); product ATE (mist) about 3.6–3.8 mg/LAdjudicated
Acute toxicology values from SDS Section 11 or NIOSH RTECS.
Supplier Qualification Packet
One zipped download containing the TDS, SDS, latest lot COA (when available), and a fresh Letter of Continuing Guaranty for Hydrofluorosilicic Acid 23% (HFS). Every file included is SHA-256 hashed and listed in a manifest your QA team can audit.
Applications
- Fluoridation of public drinking water supplies (NSF/ANSI 60-certified, AWWA B703 water-treatment grade material)cdn-contenu.quebec.ca
- Dosed to a water supply to reach about one part per million total fluoride for reduction of tooth decaycdn-contenu.quebec.ca
- Fed undiluted into water with liquid-feeding devices and metering pumps in water treatment plantss3.amazonaws.com
- Raw material for the production of silicofluoride saltss3.amazonaws.com
- Used in the ceramic, brewing, paint and metallurgical industriess3.amazonaws.com
- Used as the principal raw material in the production of silicofluoride salts.s3.amazonaws.com
Applications are drawn from published manufacturer and supplier documentation; each is sourced. Suitability for a specific use is the buyer's to confirm.
Storage & Handling
- Recommended Storage
- Store in tightly closed polyethylene or other acid-resistant plastic containers — never glass or metal. Keep cool and ventilated, away from bases, metals and oxidizers, with corrosion-resistant secondary containment.Adjudicated
- Handling Precautions
- Use full PPE including face shield, acid-resistant gloves and apron. Add acid to water slowly with stirring; never reverse. Ventilation required.Class-level guidance — not product-specific; the SDS controls.
- Incompatibilities
- Metals (releases flammable hydrogen gas); glass, ceramics and stoneware (etched); bases and alkalis (violent reaction); strong oxidizers; concentrated acids (release hydrogen fluoride and silicon tetrafluoride).Adjudicated
- Shelf Life
- Consult Technical Services for product-specific shelf life
For full hazard, PPE, and emergency response guidance, refer to the Safety Data Sheet (SDS) for this product. The SDS controls in all cases where guidance differs.
Packaging & Logistics
Shipping Description (US DOT)
UN1778, Fluorosilicic acid, 8, PG II
Sourced from 49 CFR 172.101. Confirm against shipping documents and carrier requirements before tender.
NMFC Class
60
Placard
Corrosive
Packing Group
PG II
Revision History
Last reviewed 2026-07-17 by Andre Taki, Chief Commercial Officer, DOT Hazmat–certified (49 CFR 172.704).
| Version | Date | Change | Trigger |
|---|---|---|---|
| 1.7 | 2026-10-08 | Canonical data updated: 25 fields changed via the provenance/adjudication pipeline.
| canonical_change |
| 1.6 | 2026-10-07 | Canonical data updated: 3 fields changed via the provenance/adjudication pipeline.
| canonical_change |
| 1.5 | 2026-10-05 | Canonical data updated: 3 fields changed via the provenance/adjudication pipeline.
| canonical_change |
| 1.4 | 2026-09-30 | Canonical data updated: 2 fields changed via the provenance/adjudication pipeline.
| canonical_change |
| 1.3 | 2026-08-05 | Canonical data updated: 4 fields changed via the provenance/adjudication pipeline.
| canonical_change |
| 1.2 | 2026-07-22 | Canonical data updated: 1 field changed via the provenance/adjudication pipeline.
| canonical_change |
| 1.1 | 2026-07-17 | Canonical data re-verified: 6 fields updated against independent vendor SDSs, CLP Annex VI, 49 CFR, and OSHA HazCom 2024 (GHS classification, hazard/precautionary codes, signal word, physical properties as applicable).
| canonical_change |
| 1.0 | 2026-05-20 | Initial URL-first TDS published from canonical chemistry registry. | initial |
This Technical Data Sheet is provided for technical reference. The Safety Data Sheet (SDS) controls in all cases where guidance differs. Values reflect Alliance Chemical canonical data at time of generation; subsequent revisions are recorded in the Revision History above.