Overview
Hexafluorosilicic acid (CAS 16961-83-4 ), also known as fluorosilicic acid, is a strong inorganic acid supplied primarily as an aqueous solution. It is produced as a byproduct of phosphate fertilizer manufacturing.
This chemical serves as a cost-effective source of fluoride and silicon across several industrial sectors. In municipal water treatment, it is the most commonly used chemical for drinking water fluoridation.
The acid is dosed to regulated concentration targets to ensure safety and efficacy. The construction and concrete industry uses it to harden and densify cementitious surfaces by reacting with calcium compounds.
This reaction forms insoluble silicates that reduce porosity and improve wear resistance. In metal surface treatment, it functions as an etchant and adhesion promoter for preparing various substrates.
It is frequently used prior to coating or plating operations to ensure quality. Mining operations use it in ore processing and as a pH-regulating agent in leaching circuits for mineral extraction.
Fluorosilicic acid is supplied as an aqueous solution, with 20–25% and 23% w/w concentrations being the most commercially standard. These concentrations are ideal for water treatment applications.
Higher-concentration solutions up to approximately 35% are available for industrial uses. Technical grade is the predominant market specification for most large-scale manufacturing and processing needs.
Product quality is typically referenced against water treatment authority standards or regional regulatory requirements. This ensures the material meets the necessary safety profiles for public infrastructure.
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Physical Properties
| Boiling Point | 115.4 °C |
| Density | 1.22 g/mL at 25 °C |
| Flash Point | 108-109°C |
| Appearance | colourless liquid; often supplied as a colourless solution in water |
| Color | Clear colorless |
| Form | Liquid |
| Water Solubility | Miscible with water. |
| Vapor Pressure | 23hPa at 19.85℃ |
| Refractive Index | 1.3500 |
Safety & Handling
Danger GHS05 GHS06 GHS07 GHS08 Hazard Statements H290 May be corrosive to metals H302 Harmful if swallowed H311 Toxic in contact with skin H314 Causes severe skin burns and eye damage H318 Causes serious eye damage H332 Harmful if inhaled H335 May cause respiratory irritation H371 May cause damage to organs H372 Causes damage to organs through prolonged or repeated exposure H373 May causes damage to organs through prolonged or repeated exposure H402 Harmful to aquatic life H412 Harmful to aquatic life with long lasting effects Precautionary Statements P234 Keep only in original packaging. P260 Do not breathe dust/fume/gas/mist/vapours/spray. P261 Avoid breathing dust/fume/gas/mist/vapours/spray. P262 Do not get in eyes, on skin, or on clothing. P264 Wash … thoroughly after handling. P270 Do not eat, drink or smoke when using this product. P271 Use only outdoors or in a well-ventilated area. P273 Avoid release to the environment. P280 Wear protective gloves/protective clothing/eye protection/face protection. P316 Get emergency medical help immediately. P317 Get emergency medical help. P319 Get medical advice/attention if you feel unwell. P321 Specific treatment (see … on this label). P330 Rinse mouth. P363 Wash contaminated clothing before reuse. P390 Absorb spillage to prevent material damage. P405 Store locked up. P406 Store in a corrosion-resistant/… container with a resistant inner liner. P501 Dispose of contents/container in accordance with local regulations. P264+P265 Wash … thoroughly after handling. P301+P317 Get emergency medical help. P302+P352 IF ON SKIN: Wash with plenty of water. P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing. P308+P316 Get emergency medical help immediately. P361+P364 Take off immediately all contaminated clothing and wash it before reuse. P403+P233 Store in a well-ventilated place. Keep container tightly closed. P301+P330+P331 Rinse mouth. Do NOT induce vomiting. P302+P361+P354 IF ON SKIN: Take off immediately all contaminated clothing. Rinse skin with water/shower. P305+P354+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
Trade & Regulatory
| HS Code | 28111990 |
| UN Number | 1778 |
| ADR Class | 8 |
| Packing Group | II |
| Storage Class | 6.1D - Non-combustible acute toxic Cat.3 toxic hazardous materials or hazardous materials causing chronic effects |
| WGK (Germany) | 3 |
Other Names
Related Products
Chemical Properties
- CAS Number
- 16961-83-4
- EC Number
- -
- Mol. Weight
- 144.091
- HS Code
- 28111990
- Category
- Chelating Agents