Hydrofluoric acid is an aqueous solution of hydrogen fluoride gas. It is a clear, colorless, smoky corrosive liquid with a strong irritating odor. Melting point - 83.3 C, boiling point 112.2 C, density 0.888 g/cm. It is soluble in water and ethanol and slightly soluble in ether. Because the binding ability between hydrogen atom and fluorine atom is relatively strong, the hydrofluoric acid can not be completely ionized in water, so theoretically low concentration hydrofluoric acid is a weak acid (according to its ionization constant in fact belongs to medium strong acid). It is highly corrosive and can strongly corrode metals, glass and silicon-containing objects. Inhalation of vapor or contact with skin can cause irreparable burns. Laboratories generally use fluorite (mainly composed of calcium fluoride) and concentrated sulfuric acid to make, need to be sealed in plastic bottles, and stored in a cool place.

Pathogenic principle

Hydrogen fluoride can stimulate and corrode the clothing, skin, eyes, respiratory tract and digestive tract mucosa. Fluoride ions enter the blood or tissues and can bind with calcium and magnesium ions, making them insoluble or slightly soluble calcium fluoride and magnesium fluoride. Large amounts of hydrogen fluoride can directly block blood vessels, directly or indirectly affect the functions of central nervous system and cardiovascular system, leading to hypocalcemia and hypomagnesia syndrome. Fluoride ion can also combine with hemoglobin to form fluoroheme, inhibit succinate dehydrogenase, and then decrease the oxygenation, affecting cell respiratory function. In addition, hydrofluoric acid can cause obvious burns at contact sites, dehydrate and dissolve tissue proteins, penetrate the cuticle quickly, penetrate deep tissues, dissolve cell membranes, and cause tissue liquefaction. In severe cases, it can reach the periosteum and bone, and make bones become calcium fluoride, forming ulcers with slow healing. Inhalation of high concentration steam or percutaneous absorption can cause pulmonary edema in patients with chemical pneumonia.

purpose

Hydrofluoric acid plays an important role in the purification of aluminium and uranium due to its ability to dissolve oxides. Hydrofluoric acid is also used to etch glass and engrave patterns, markings and texts; it is used by the semiconductor industry to remove oxides on silicon surfaces; it can be used as a catalyst for alkylation of isobutane and n-butene in refineries; and hydrofluoric acid is also used in the 'acid dipping' process to remove oxygen-containing impurities on stainless steel surfaces. Hydrofluoric acid is also used in the synthesis of a variety of fluorinated organic compounds, such as Teflon (polytetrafluoroethylene) and refrigerants such as Freon.