Hydrofluoric acid is the weakest of the hydrohalic acids, having a pKa of 3.2 at 25 °C.
It is a volatile liquid due to the presence of hydrogen bonding (while the other hydrohalic acids are gases).
It is able to attack glass, concrete, metals, organic matter.

Hydrofluoric acid is a contact poison with greater hazards than many strong acids like sulfuric acid even though it is weak: it remains neutral in aqueous solution and thus penetrates tissue faster, whether through inhalation, ingestion or the skin, and at least nine U.S. workers died in such accidents from 1984 to 1994.
It reacts with calcium and magnesium in the blood leading to hypocalcemia and possible death through cardiac arrhythmia.
Insoluble calcium fluoride formation triggers strong pain and burns larger than 160 cm² (25 in²) can cause serious systemic toxicity.

Exposure may not be evident for eight hours for 50% HF, rising to 24 hours for lower concentrations, and a burn may initially be painless as hydrogen fluoride affects nerve function.
If skin has been exposed to HF, damage can be reduced by rinsing it under a jet of water for 10–15 minutes and removing contaminated clothing.
Calcium gluconate is often applied next, providing calcium ions to bind with fluoride; skin burns can be treated with 2.5% calcium gluconate gel or special rinsing solutions.
Hydrofluoric acid absorption requires further medical treatment; calcium gluconate may be injected or administered intravenously.
Using calcium chloride – a common laboratory reagent – in lieu of calcium gluconate is contraindicated, and may lead to severe complications.
Excision or amputation of affected parts may be required.
Hydrofluoric acid is the weakest of the hydrohalic acids, having a pKa of 3.2 at 25 °C. It is a volatile liquid due to the presence of hydrogen bonding (while the other hydrohalic acids are gases). It is able to attack glass, concrete, metals, organic matter.
Hydrofluoric acid is a contact poison with greater hazards than many strong acids like sulfuric acid even though it is weak: it remains neutral in aqueous solution and thus penetrates tissue faster, whether through inhalation, ingestion or the skin, and at least nine U.S. workers died in such accidents from 1984 to 1994. It reacts with calcium and magnesium in the blood leading to hypocalcemia and possible death through cardiac arrhythmia. Insoluble calcium fluoride formation triggers strong pain and burns larger than 160 cm² (25 in²) can cause serious systemic toxicity.
Exposure may not be evident for eight hours for 50% HF, rising to 24 hours for lower concentrations, and a burn may initially be painless as hydrogen fluoride affects nerve function. If skin has been exposed to HF, damage can be reduced by rinsing it under a jet of water for 10–15 minutes and removing contaminated clothing. Calcium gluconate is often applied next, providing calcium ions to bind with fluoride; skin burns can be treated with 2.5% calcium gluconate gel or special rinsing solutions. Hydrofluoric acid absorption requires further medical treatment; calcium gluconate may be injected or administered intravenously. Using calcium chloride – a common laboratory reagent – in lieu of calcium gluconate is contraindicated, and may lead to severe complications. Excision or amputation of affected parts may be required.
Fluorine