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What it is. This hydrofluoric acid is the concentrated 49% ACS reagent grade, assaying 48.0 to 51.0% hydrogen fluoride in water, supplied in a 500 mL size. It is a clear, colorless, fuming liquid and the standard starting strength for HF etching, digestion, and dilution.
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What ACS grade guarantees. ACS reagent hydrofluoric acid limits fluosilicic acid to 0.01%, residue after ignition to 5 ppm, chloride and sulfate-plus-sulfite to 5 ppm each, phosphate and iron to 1 ppm, heavy metals to 0.5 ppm, copper to 0.1 ppm, and arsenic to 0.05 ppm. Those limits make it suitable for trace-metal digestion and semiconductor-related work.
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How concentrated it is. With a density of about 1.15 g/cm³, 49% hydrofluoric acid contains roughly 560 g of HF per liter, about 28 M (calculated). It boils near 106 °C, melts near -35 °C, and releases highly toxic hydrogen fluoride vapor.
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Why HF dissolves glass and silicates. Hydrofluoric acid reacts with silicon dioxide to form soluble silicon fluorides, so it dissolves glass, quartz, and silicate minerals that other acids cannot attack. That reaction underlies its use in oxide etching, glass frosting, and silicate digestion for analysis.
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Why it is so dangerous. HF is a weak acid by dissociation, but the fluoride ion penetrates skin, binds calcium and magnesium in tissue and blood, and can cause deep, delayed burns and fatal systemic poisoning. Burns from dilute acid may not hurt for hours, which delays treatment.
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Preparing working solutions. Most HF work uses diluted acid. Prepare dilutions in polyethylene or fluoropolymer labware inside a fume hood, adding acid to water. Lab Pro also supplies ready-made dilutions, including Hydrofluoric Acid 10% Solution and Hydrofluoric Acid 1:20 in DI Water, which avoid handling concentrate.
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First aid readiness. Every lab using HF needs calcium gluconate gel within reach, a written response plan, and trained users. After skin contact, rinse with water, apply calcium gluconate gel immediately, and seek emergency care. Lab Pro offers Calgonate 2.5% Calcium Gluconate Gel.
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Where it is used. Concentrated hydrofluoric acid is used to etch silicon dioxide in semiconductor fabrication, etch glass and quartz, digest silicate rocks and soils for trace-element analysis, pickle stainless steel and titanium, and synthesize fluorine compounds.
Technical Specifications
| Chemical Name |
Hydrofluoric acid, aqueous solution |
| CAS Numbers |
7664-39-3 (hydrogen fluoride); 7732-18-5 (water) |
| EC Number (HF) |
231-634-8 |
| Synonyms |
Hydrogen fluoride solution, fluoric acid, HF |
| Formula (active) |
HF |
| Molecular Weight (active) |
20.01 g/mol |
| Grade |
ACS reagent |
| Assay (HF) |
48.0 to 51.0% |
| Density |
About 1.15 g/cm³ |
| Approximate Molarity |
About 28 M (calculated) |
| Boiling Point |
About 106 °C |
| Melting Point |
About -35 °C |
| Fluosilicic Acid (H2SiF6) |
0.01% max |
| Residue after Ignition |
5 ppm max |
| Chloride (Cl) |
5 ppm max |
| Sulfate and Sulfite (as SO4) |
5 ppm max |
| Phosphate (PO4) |
1 ppm max |
| Iron (Fe) |
1 ppm max |
| Heavy Metals (as Pb) |
0.5 ppm max |
| Copper (Cu) |
0.1 ppm max |
| Arsenic (As) |
0.05 ppm max |
| Hazard Statements |
H300 + H310 + H330 (fatal if swallowed, in contact with skin, or inhaled); H314 |
| DOT |
UN1790, Hydrofluoric acid, Class 8 (6.1), PG II |
| Package Size |
500 mL |
Applications / Common Uses
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Semiconductor oxide etching: Removes silicon dioxide from wafers and devices.
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Trace-metal digestion: Dissolves silicate samples with low impurity background.
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Glass and quartz etching: Frosts and patterns silicate surfaces.
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Metal pickling: Cleans stainless steel and titanium surfaces.
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Fluorine chemistry: Supplies HF for fluoride synthesis.
Storage, Handling & Shipping
Caution: Hydrofluoric acid is acutely toxic and corrosive. Skin contact may cause delayed, deep tissue injury and potentially fatal systemic fluoride poisoning, sometimes without immediate pain. Handle only in a fume hood with HF-rated gloves, a face shield, goggles, and an apron, and keep calcium gluconate gel within reach.
Store tightly closed in polyethylene, polypropylene, or fluoropolymer containers in a cool, ventilated, locked corrosives area, away from glass, ceramics, metals, bases, and oxidizers. Restrict access to trained users, and keep calcium gluconate gel and an HF-specific spill kit nearby.
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Incompatible materials: Glass, ceramics, concrete, metals, bases, and oxidizers.
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Exposure limits (hydrogen fluoride): OSHA PEL 3 ppm TWA; NIOSH REL 3 ppm TWA, 6 ppm ceiling (15 min).
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Spill response: Evacuate, ventilate, and use an HF-specific spill kit or calcium-based absorbent. Do not use silica-based absorbents.
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First aid: Skin: rinse with water, apply calcium gluconate gel, and seek emergency care. Eyes: flush for 15 minutes and seek immediate care.
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