What is Selenium dioxide?
{{Unreferenced|date=June 2023}} [[File:Selenium dioxide.jpg|thumb|Selenium dioxide]] '''Selenium dioxide''', also known as '''selenious oxide''', '''selenous oxide''', or '''selenium(IV) oxide''', is a [[chemical compound]]. Its [[chemical formula]] is SeO<sub>2</sub>. It contains [[selenium]] in its +4 [[oxidation state]]. It also contains [[oxide]] [[ion]]s. It is toxic. ==Properties== Selenium dioxide is a white [[solid]]. It dissolves in water to make [[selenous acid]]. It easily evaporates. The vapor smells like horseradish sauce. It can burn the nose. It reacts with [[base (chemistry)|bases]] to make [[selenite]]s. ==Preparation== Selenium dioxide can be made by burning selenium in air. It can also be made by reacting selenium with [[nitric acid]] or [[hydrogen peroxide]]. Another way to make it is to heat selenous acid. ==Occurrence== Selenium dioxide is very rare as a mineral. It only is in places where coal caught on fire and the [[selenide]]s were [[oxidation|oxidized]] to selenium dioxide. ==Uses== Selenium dioxide is used in making [[organic chemistry|organic]] compounds. Selenium dioxide is used as a coloring in glass. [[Cobalt]] in glass makes a blue color. When a little selenium dioxide is added, the glass becomes colorless. When more selenium dioxide is added, the glass becomes ruby red. ==Safety== Selenium dioxide can dissolve in water to make toxic selenium compounds. Swallowing any more than a very tiny amount can cause selenium poisoning. Selenium dioxide is a weak [[oxidizing agent]] and does not catch things on fire. ==Related pages== *[[Selenium trioxide]] *[[Selenic acid]] [[Category:Selenium compounds]] [[Category:Oxides]]