<P> The principal use of hydrofluoric acid is in organofluorine chemistry . Many organofluorine compounds are prepared using HF as the fluorine source, including Teflon, fluoropolymers, fluorocarbons, and refrigerants such as freon . </P> <P> Most high - volume inorganic fluoride compounds are prepared from hydrofluoric acid . Foremost are Na AlF, cryolite, and AlF, aluminium trifluoride . A molten mixture of these solids serves as a high - temperature solvent for the production of metallic aluminium . Given concerns about fluorides in the environment, alternative technologies are being sought . Other inorganic fluorides prepared from hydrofluoric acid include sodium fluoride and uranium hexafluoride . </P> <P> In metalworking, hydrofluoric acid is used as a pickling agent to remove oxides and other impurities from stainless and carbon steels because of its limited ability to dissolve steel . It is used in the semiconductor industry as a major component of Wright Etch and buffered oxide etch, which are used to clean silicon wafers . In a similar manner it is also used to etch glass by reacting with silicon dioxide to form gaseous or water - soluble silicon fluorides . It can also be used to polish and frost glass . </P> <Dl> <Dd> SiO + 4 HF → SiF (g) + 2 H O </Dd> <Dd> SiO + 6 HF → H SiF + 2 H O </Dd> </Dl>

Which acid is used to write on glass