248 Hydrogen fluoride HF can refer to both hydrogen fluoride (gas) and hydrofluoric acid. Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. It is a precursor to almost all fluorine compounds, including pharmaceuticals such as fluoxetine (Prozac), surface coatings such as PTFE (Teflon), and elemental fluorine itself. Hydrofluoric acid is classified as a weak acid because of its lower dissociation constant compared to the strong acids. Hydrofluoric acid is produced by treatment of the mineral fluorite (CaF2) with concentrated sulfuric acid. When combined at 265 °C, these two substances react to produce hydrogen fluoride and calcium sulfate. HF is used in oil refining, the production of organofluorines, fluorides and glass etching. Hydrofluoric acid is also used for dissolving rock samples (usually powdered) prior to analysis. 7664-39-3 14917 FH 20.006230 -83.36°C 0.922 mg/mL at 0 °C [DEAN,JA (1985)] Oral (A116) ; inhalation (A116) ; dermal (A116) In addition to being a highly corrosive liquid, hydrofluoric acid is also a contact poison. As with most acids HF can cause tissue burns through the denaturation of proteins and partial hydrolysis of proteins. Most proteins denature at pH values of less than 3-4. The large-scale denaturation of proteins, de-esterification of lipids and subsequent desiccation of tissues leads to chemical burns. Owing to its low acid dissociation constant, HF as a neutral lipid-soluble molecule penetrates tissue more rapidly than typical mineral acids. Because of the ability of hydrofluoric acid to penetrate tissue, poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed. HF also interferes with nerve function, meaning that burns may not initially be painful. In the body, hydrofluoric acid reacts with the ubiquitous biologically important ions Ca2+ and Mg2+. Formation of insoluble calcium fluoride is proposed as the etiology for both precipitous fall in serum calcium and the severe pain associated with tissue toxicity. In some cases, exposures can lead to hypocalcemia. Inorganic fluoride inhibits adenylate cyclase activity required for antidiuretic hormone effect on the distal convoluted tubule of the kidney. Fluoride also stimulates intrarenal vasodilation, leading to increased medullary blood flow, which interferes with the counter current mechanism in the kidney required for concentration of urine. Fluoride ions are incorporated into bone by substituting for hydroxyl groups in the carbonate-apatite structure to produce hydroxyfluorapatite, thus altering the mineral structure of the bone. Alteration in mineralization increases hardness and bone mass, but also decreases mechanical strength. A portion of the circulating inorganic fluoride acts as an enzyme inhibitor because it forms metalfluoride-phosphate complexes that interfere with the activity of those enzymes requiring a metal ion cofactor. In addition, fluoride may interact directly with the enzyme or the substrate. It is a general inhibitor of the energy production system of the cell. Fluorine may bind calcium and decrease its concentration. This is thought to indirectly inhibit amelogeninase activity, resulting in altered crystal growth and subsequently causing dental fluorosis. (L963) LC50: 500 ppm over 1 hours (Inhalation, Mouse) (T50) 50 to 250 ppm over 5 minutes (Inhalation) or 1.5 grams (Oral) for an adult human. (T37, A289) No indication of carcinogenicity to humans (not listed by IARC). Hydrofluoric acid is used mainly for etching glass. It is also used in oil refining and as a precursor to other fluoride compounds. (L963) Hydrogen fluoride is extremely corrosive. It may penetrate the skin and weaken the bones, as well as interfere with nerve function and react with blood calcium, causing cardiac arrest. (L968) Hydrogen fluoride is very irritating to the skin, eyes, and respiratory tract. (L963) Hydrofluoric acid exposure is often treated with calcium gluconate, a source of Ca2+ that sequesters the fluoride ions. HF chemical burns can be treated with a water wash and 2.5% calcium gluconate gel or special rinsing solutions. However, because it is absorbed, medical treatment is necessary; rinsing off is usually not enough. Intra-arterial infusions of calcium chloride have also shown great effectiveness in treating burns. 2009-03-06T18:58:22Z 2014-12-24T20:21:24Z http://en.wikipedia.org/wiki/Hydrogen fluoride C16487 29228 D006858 Hydrogen fluoride 7949 true F FH InChI=1S/FH/h1H InChIKey=KRHYYFGTRYWZRS-UHFFFAOYSA-N 20.0063 20.006228237 Exogenous Gas CHEMBL1232767 14214