Substance profile
Fluorosilicic acid
Fluorosilicic acid is a transparent, colorless, fuming liquid with a sour, pungent odor.
01 · Identification
What Fluorosilicic acid is
Fluorosilicic acid is a transparent, colorless, fuming liquid with a sour, pungent odor. Its molecular formula is F6H2Si and its molecular weight is 144.091 g/mol. It boils at 100 °C, melts at -20 °C.
Under the GHS it carries the signal word Danger. It is classed as corrosives.
02 · Identifiers
Fluorosilicic acid identifiers and molecular data
Fluorosilicic acid CAS number and EC number
Fluorosilicic acid molecular formula and molecular weight
Other names for Fluorosilicic acid
- fluorosilicic acid ... %
03 · GHS classification
Fluorosilicic acid hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Fluorosilicic acid pictograms and signal word
Fluorosilicic acid hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Skin corrosion/irritation GHS chapter 3.2 | Category 1A or 1B or 1C | H314 | GHS05 |
Where two values are shown with “or”, the hazard statement is shared by more than one category or by more than one class, and the code alone does not say which. H272, for example, belongs to oxidising liquids and to oxidising solids — the physical state decides. The binding answer for a specific entry is in the CLP Annex VI table itself.
Fluorosilicic acid hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H314 | Causes severe skin burns and eye damage. |
This page lists only the codes assigned to Fluorosilicic acid. The full reference lives on the hazard statements hub, the precautionary statements hub and the GHS pictograms hub.
Safety Data Sheet
Getting an SDS for Fluorosilicic acid
A Safety Data Sheet is written for a product, not for a substance: the supplier of the grade you actually buy issues it, so two suppliers of Fluorosilicic acid issue two different sheets. That is why there is no single authoritative SDS for a substance to download — what there is, is the job of collecting the sheets for the products you hold and keeping them current as suppliers revise them.
04 · Precautionary statements
Fluorosilicic acid precautionary statements
CLP Annex VI assigns 5 precautionary statements to Fluorosilicic acid. They are grouped the way a label groups them: what to do before handling, what to do when something has already happened, how to store it and how to dispose of it.
Prevention
What to do before and during handling so the hazard never happens.
Response
What to do once exposure, spillage or fire has already happened.
Reading the notation. … is a blank the supplier fills in — not a truncated sentence.· [square brackets] mark a part printed only when it applies.
05 · Names in the regulation
Fluorosilicic acid name in 23 EU languages
CLP Annex VI Part 3 is published in every language edition of the regulation, and the identification column is written out in each of them. Nothing below is translated by us: each line is the name as that edition prints it. Under Art. 18(2) the substance name from Annex VI is a lawful product identifier, so this is the wording to put on a label going to that market — and where the cell lists several designations, any one of them qualifies.
| Language | Name in CLP Annex VI Part 3 |
|---|---|
| Bulgarian български | флуоросилициева киселина … % |
| Spanish español | Ácido fluorosilícico al … % |
| Czech čeština | kyselina hexafluorokřemičitá … % |
| Danish dansk | hydrogensilicimhexafluorid … %, fluskiselsyre … % % |
| German Deutsch | Hexafluorokieselsäure … % Kieselfluorwasserstoffsäure … % |
| Estonian eesti | fluororänihape … % |
| Greek ελληνικά | φθοροπυριτικό οξύ … % |
| English English | fluorosilicic acid … % |
| French français | acide fluorosilicique à … % |
| Croatian hrvatski | fluorosilicijska kiselina … % |
| Italian italiano | acido fluosilicico …% |
| Latvian latviešu | fluorsilīcijskābe … % |
| Lithuanian lietuvių | … % fluorsilicio rūgštis |
| Hungarian magyar | fluorkovasav … % |
| Maltese Malti | aċidu fluworosiliċiku … % |
| Dutch Nederlands | hexafluorkiezelzuur … % |
| Polish polski | kwas heksafluorokrzemowy … % |
| Portuguese português | ácido fluorossilícico a ... % |
| Romanian română | acid fluorosilicic ... % |
| Slovak slovenčina | kyselina hexafluorokremičitá ... % |
| Slovenian slovenščina | fluorosilicijeva kislina ... % |
| Finnish suomi | fluoripiihappo… % |
| Swedish svenska | fluorkiselsyra ... % |
All 23 language editions of Annex VI carry this entry. Irish is the twenty-fourth official EU language and has no line here for a different reason: no consolidated CLP text has ever been published in Irish, so there is no Irish edition of Annex VI to quote a name from. Source: consolidated CLP, CELEX 02008R1272, language editions. © European Union, https://eur-lex.europa.eu — only the electronic Official Journal of the European Union is authentic.
06 · Label elements
Fluorosilicic acid GHS label elements
Everything CLP Annex VI fixes for Fluorosilicic acid, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Fluorosilicic acid
- Causes severe skin burns and eye damage.
- Do not breathe dust/fume/gas/mist/vapours/spray.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- Immediately call a POISON CENTER/doctor/…
- Do NOT induce vomiting.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Fluorosilicic acid in the GHS label constructor →
07 · Health hazards
Fluorosilicic acid health hazards and exposure limits
Fluorosilicic acid hazard summary
Corrosive to skin; [Quick CPC] High inhalation exposure may cause pulmonary edema; Potential for fluorosis after chronic ingestion or inhalation of aerosol; [ICSC] Marketed strictly as an aqueous solution; Anhydrous form dissociates almost instantly into silicon tetrafluoride and hydrofluoric acid; 60-70% solutions solidify at about 19 deg C, forming a crystalline dihydrate; [Merck Index] Fumes in air; Evolves heat and corrosive fumes on mixing with water; [CAMEO] Causes burns to eyes and skin (second-degree after contact of several minutes); Chronic exposure hazards include osteofluorosis, respiratory impairment, and injury to liver and kidneys; [CHRIS] Chronic exposure may cause changes in bone, corrosion of mucous membranes, coughing, shock, pulmonary edema, fluorosis, coma, and death; [NTP] Causes burns; Inhalation may cause corrosive injuries to upper respiratory tract and lungs; Toxic by ingestion; [Aldrich MSDS] See FLUORIDES.
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
Fluorosilicic acid occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 2.5 [mg/m3], as F | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 250.0 [mg/m3], as F | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
These are United States values. The European Union sets its own indicative and binding limits, and the figure that applies at a given workplace is the one in the local regulation — not the one shown here.
08 · Physical and chemical properties
Fluorosilicic acid properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
Fluorosilicic acid boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 100 °C (212 °F) | at 760 mmHg | CAMEO |
| Decomposes. (USCG, 1999) | decomposes | CAMEO |
Fluorosilicic acid melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -20 °C (-4 °F) | CAMEO |
Fluorosilicic acid density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 1.25 g/cm³ | CAMEO | |
| 1.4634 g/cm³ | at 25 °C | HSDB | |
| 1.3 g/cm³ | at 25 °C, approx. | CAMEO |
Fluorosilicic acid solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | DECOMP AT MP; DELIQUESCENT; WHITE CRYSTALS; SOL IN ALKALI; SOL IN COLD AND HOT WATER | DIHYDRATE | HSDB |
| SOL IN COLD & HOT WATER; SLIGHTLY IN ALKALI | HSDB | ||
| Solubility in water: miscible | ICSC |
Fluorosilicic acid corrosivity
| Property | Value | Conditions | Source |
|---|---|---|---|
| Corrosivity | Attacks glass and stoneware | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Handling and storage
Fluorosilicic acid storage and handling
Fluorosilicic acid safe storage
Separated from strong bases and food and feedstuffs. Well closed.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Fluorosilicic acid storage conditions
The more concentrated solution (but not the anhydrous liquid) can be stored in glass, although some etching will take place around the surface. Usually stored in iron containers.
Source: Hazardous Substances Data Bank (HSDB)
Fluorosilicic acid incompatible materials
Will react with water or steam to produce toxic and corrosive fumes.
Source: Hazardous Substances Data Bank (HSDB)
Planning storage for a mix of chemicals? Check Fluorosilicic acid in the storage compatibility matrix →
10 · Transport
Fluorosilicic acid UN number and transport classification
Transport classification is a separate system from the GHS classification above. It decides how a package is marked and how a load may be carried; it does not follow from the workplace label, and the workplace label does not follow from it. The entries below are linked by CAS number, never by name.
Fluorosilicic acid under UN 1778 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| FLUOROSILICIC ACID | 8 | C1 | II | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 8 is “Corrosive substances” (ADR 2.1.1.1).
United States · 49 CFR 172.101 Hazardous Materials Table
| Proper shipping name (column 2) | Class or division | PG | Labels (column 6) |
|---|---|---|---|
| Fluorosilicic acid | 8 | II | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 8 is “Corrosive material” (49 CFR 173.2).
11 · Questions
Fluorosilicic acid — frequently asked questions
What is the CAS number of Fluorosilicic acid?
The CAS number of Fluorosilicic acid is 16961-83-4. Its EC number is 241-034-8.
What is the chemical formula of Fluorosilicic acid?
The molecular formula of Fluorosilicic acid is F6H2Si and its molecular weight is 144.091 g/mol.
What does a Fluorosilicic acid label have to show?
Under CLP Annex VI the label for Fluorosilicic acid carries the pictogram Corrosion and the signal word is Danger.
Is Fluorosilicic acid flammable?
CLP Annex VI assigns Fluorosilicic acid no flammability hazard class. That is not a statement that it cannot burn: the harmonised list only records the hazards that were assessed for it.
Is Fluorosilicic acid a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Fluorosilicic acid. Annex VI is a list of agreed classifications, not a list of substances found safe, so this is an absence of a classification rather than a clean bill of health.
What is the exposure limit for Fluorosilicic acid?
The US occupational exposure limit reported for Fluorosilicic acid is 2.5 [mg/m3], as F (Haz-Map, Information on Hazardous Chemicals and Occupational Diseases). Limits differ by country: the EU sets its own indicative and binding values, and the figure that applies at a given workplace is the one in the local regulation.
What is the boiling point of Fluorosilicic acid?
The boiling point reported for Fluorosilicic acid is 100 °C (212 °F), at 760 mmHg (CAMEO).
What is the melting point of Fluorosilicic acid?
The melting point reported for Fluorosilicic acid is -20 °C (-4 °F) (CAMEO).
How should Fluorosilicic acid be stored?
The more concentrated solution (but not the anhydrous liquid) can be stored in glass, although some etching will take place around the surface. Usually stored in iron containers. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Fluorosilicic acid
Keep going: substances starting with F, or search the whole database by name, CAS number, pictogram or signal word.