hydrofluoric

Hydrofluoric, in chemical contexts, commonly refers to hydrofluoric acid, the aqueous solution of hydrogen fluoride (HF). HF is present as a colorless liquid at room temperature, with unusually strong corrosivity toward glass and many metals. In water, it behaves as a weak acid with a dissociation constant (pKa) of about 3.17, but the fluoride ion generated is highly reactive and can interfere with calcium and magnesium in tissues, leading to serious injury.

HF is highly corrosive and capable of penetrating skin and bone, producing deep tissue burns that may be delayed in onset. Concentrated solutions release corrosive vapors; exposure requires immediate decontamination and medical assessment. HF reacts with silica to form silicon tetrafluoride and hexafluorosilicate, which underpins its use in glass etching and laboratory cleaning.

Industrial production of hydrofluoric acid typically involves reacting fluorite (CaF2) with sulfuric acid to liberate hydrogen fluoride gas, which is absorbed in water to form HF solution. It is also produced in some fluorochemical processes and recycled from other fluorides.

Applications include glass etching, metal surface treatment, and the semiconductor industry, where HF is used to pattern silicon dioxide layers. It serves as a fluorinating agent and flux in ceramic and metal finishing. Solutions vary from concentrated liquids to dilute aqueous mixtures used in laboratories.

Safety and handling require training and appropriate protective equipment, including neoprene or nitrile gloves, eye protection, face shield, and chemical-resistant cabinets. HF containers are usually made of specialized plastics or Teflon; glass is avoided. In case of exposure, calcium gluconate gel is used topically, and severe cases require professional medical management to address hypocalcemia and electrolyte disturbances.

See also: hydrofluoric acid, fluoride, silicon tetrafluoride.