Hydrofluoric acid

General
Name	Hydrogen fluoride
Chemical formula	H F
Appearance	Colorless gas
Physical properties
Formula weight	20.1 amu
Melting point	190 K (-83 °C)
Boiling point	294 K (19.5 °C)
Density	0.97 ×10³ kg/m³ (liquid)
Solubility	miscible with water
Thermochemistry
Δ_fH⁰_gas	? kJ/mol
Δ_fH⁰_liquid	? kJ/mol
Δ_fH⁰_solid	? kJ/mol
S⁰_{gas, 1 bar}	? J/mol·K
S⁰_{liquid, 1 bar}	? J/mol·K
S⁰_solid	? J/mol·K
Safety
Ingestion	Toxic, can be fatal.
Inhalation	Highly toxic, can result in pulmonary edema.
Skin	Causes severe burns. Absorbs through skin to cause nerve, bone and organ damage.
Eyes	Extremely dangerous.
SI units were used where possible. Unless otherwise stated, standard conditions were used. Disclaimer and references

Hydrofluoric acid is a highly corrosive solution of the chemical compound hydrogen fluoride in water. Pure hydrogen fluoride is often called anhydrous hydrofluoric acid. While hydrofluoric acid is a weak acid, it has the unique ability to dissolve almost all inorganic oxides, and so it is nonetheless very corrosive towards glass and must be stored in metal or plastic containers. In the human body, hydrofluoric acid reacts with calcium and damages nerves, bone, and several organs including the heart and kidneys. As such, exposure to hydrofluoric acid requires immediate and specific medical attention.

Table of contents

1 Production
2 Uses
3 Safety

Production

Industrially, hydrofluoric acid is produced from the mineral fluorspar, also known as calcium fluoride (chemical formula CaF₂) and concentrated sulfuric acid. When combined at 250°C, these two substances react to produce hydrogen fluoride according to the chemical equation

CaF₂ + H₂SO₄ → 2 HF + CaSO₄

The vapors from this reaction are a mixture of hydrogen fluoride, sulfuric acid, and a few minor byproducts, from which hydrogen fluoride can be isolated by distillation.

Uses

Hydrofluoric acid's ability to dissolve oxides makes it important in the purification of both aluminum and uranium. It is also used to etch glass, to remove surface oxides from silicon in the semiconductor industry, and to remove oxide impurities from stainless steel in a process called pickling.

Hydrofluoric acid is also used in the synthesis of many fluorine-containing organic compounds, including teflon and refrigerants such as freon.

Safety

In the body, hydrofluoric acid reacts with calcium and magnesium ions and can disable organs whose proper function depends on these metals. Exposure to hydrofluoric acid may not be initially painful, and symptoms may not occur until several hours later, when the acid begins to react with calcium in the bones. If left untreated, hydrofluoric acid exposure can result in severe or even lethal damage to the heart, liver, kidneys, and nerves.

First aid for hydrofluoric acid exposure consists of rubbing a calcium gluoconate gel into the exposed area of the body. In more severe cases, a calcium-containing solution may be injected into the affected region. In all cases, hydrofluoric acid exposure requires immediate professional medical attention.

Exposure of less than 10% of the body can be fatal, even with immediate medical treatment. [1]