Hydrofluoric acid is a colourless solution of hydrogen fluoride in water. It acts as a precursor in almost all the fluorine compounds. It is highly corrosive and can dissolve many materials (especially oxides).
Because it is highly reactive towards glass & moderate activity towards many metals, it is generally stored in plastic containers. Hydrogen fluoride gas and concentrated acid is highly toxic and can lead to cardiac arrest and fatality.
A common concentration is 49% (48-52%) but there are also stronger solutions (e.g. 70%) and pure HF has a boiling point near room temperature.
It is used to make most fluorine-containing compounds; examples include the commonly used pharmaceutical antidepressant medication fluoxetine (Prozac) and the material PTFE (Teflon). Elemental fluorine is produced from it. It is commonly used to etch glass and silicon wafers.
Uses of Hydrofluoric Acid
Here are some important uses/applications of hydrofluoric acid:
#1. Oil refining.
It is used as an acid catalyst in a standard oil refinery process.
#2. In production of organofluorine compounds.
Hydrofluoric acid is highly used in organofluorine chemistry. It acts as a fluorine source in the production of organofluorine compounds such as Teflon, fluorocarbons, fluoropolymers and refrigerants like freon.
#3. In production of fluorides.
Hydrofluoric acid is used for producing most of the high-volume inorganic fluoride compounds such as cryolite, aluminium trifluoride, etc.
#4. Pickling and cleaning agent.
In metalworking, it acts as a pickling agent to remove oxides and other impurities from carbon steels and stainless steel. A dilute solution of hydrofluoric acid acts as a household rust stain remover.
#5. Niche applications.
Hydrofluoric acid is useful to dissolve rock samples (generally powdered) because of its ability to dissolve most of the silicates and the oxides.
What Makes Hydrochloric Acid So Dangerous?
Unlike other inorganic acids like hydrochloric (HCl), sulfuric (H2SO4), nitric (HNO3), or phosphoric (H3PO4) acid, hydrofluoric (HF) acid is highly lipophilic and readily penetrates through the skin into deeper tissue.
Once absorbed, the fluoride ion – which has an extremely strong affinity for cations – combines with the calcium (Ca2+) and magnesium (Mg2+) in the blood to form insoluble salts. This, in turn, reduces the amount of calcium and magnesium leading to hypocalcemia and hypomagnesemia. This electrolyte imbalance can result in cardiac arrhythmia and cardiac arrest
Depending on the concentration of acid that one is exposed to, symptoms of exposure which include pain, discoloration or discomfort can vary significantly.
Solutions < 7% HF may take several hours before onset of symptoms, resulting in delayed presentation, deeper penetration of the undissociated HF, and a more severe burn.
Solutions of 12% HF may take up to one hour to produce symptoms. HF solutions > 14.5% immediately produce symptoms including redness, swelling, and blistering.
How you could be exposed to hydrogen fluoride
In a natural disaster, you could be exposed to high levels of hydrogen fluoride when storage facilities or containers are damaged and the chemical is released. This release could occur at an industrial site or even a retail location.
You could be exposed to hydrogen fluoride if it is used as a chemical terrorism agent. If you work in an occupation that uses hydrogen fluoride, you may be exposed to this chemical in the workplace. You may be exposed to hydrogen fluoride as part of a hobby.
Immediate signs and symptoms of exposure to hydrogen fluoride
Swallowing only a small amount of highly concentrated hydrogen fluoride will affect major internal organs and may be fatal.
Hydrogen fluoride gas, even at low levels, can irritate the eyes, nose, and respiratory tract. Breathing in hydrogen fluoride at high levels or in combination with skin contact can cause death from an irregular heartbeat or from fluid buildup in the lungs.
Even small splashes of high-concentration hydrogen fluoride products on the skin can be fatal. Skin contact with hydrogen fluoride may not cause immediate pain or visible skin damage(signs of exposure).
Often, patients exposed to low concentrations of hydrogen fluoride on the skin do not show effects or experience pain immediately. And, severe pain at the exposure site may be the only symptom for several hours. Visible damage may not appear until 12 to 24 hours after the exposure.
Depending on the concentration of the chemical and the length of time of exposure, skin contact with hydrogen fluoride may cause severe pain at the point of contact; a rash; and deep, slow-healing burns. Severe pain can occur even if no burns can be seen.
Showing these signs and symptoms does not necessarily mean that a person has been exposed to hydrogen fluoride. Other chemicals also can cause these effects.
Exposure to hydrogen fluoride can result in severe electrolyte problems.