<?xml version="1.0" encoding="utf-8"?><mads xmlns="http://www.loc.gov/mads/" xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/mads/
mads.xsd"><authority><topic authority="http://AATesaurus.cultura.gencat.cat/aat/getty_en">hydrogen fluoride</topic></authority><related type="broader"><topic>acid</topic></related><related type="broader"><topic>fluoride</topic></related><variant type="other"><topic>anhydrous hydrofluoric acid</topic></variant><variant type="other"><topic>fluoride, hydrogen</topic></variant><variant type="other"><topic>hydrofluoric acid gas</topic></variant> <note xml:lang="en"><![CDATA[ A colorless corrosive gas, the hydride of fluorine and an extremely powerful halogen acid, hydrogen fluoride is used as a catalyst and a fluorinating agent. Its chief use is in making fluorine-containing refrigerants such as freons. In a conservation context, hydrogen fluoride is considered as an atmospheric pollutant which damages metal structures, and buildings or monuments made of limestone. ]]></note></mads>