The major use is in protecting and changing the color of steel, especially steel parts on firearms. The so-called cold-bluing process uses<unk> , copper(II) nitrate, and nitric<unk>  to change the color of the steel from silver-grey to blue-grey or black. Alternative procedures use copper sulfate and phosphoric<unk>  instead. This process deposits a coating of copper selenide and is fundamentally different from other bluing processes which generate black iron oxide. Some older razor blades were also made of blued steel. Another use for<unk>  is the chemical darkening and patination of copper, brass and bronze, producing a rich dark brown color that can be further enhanced with mechanical abrasion. It is used in organic synthesis as an oxidizing agent for the synthesis of 1,2-dicarbonyl compounds, e.g. in laboratory preparation of glyoxal (ethane-1,2-dione) from acetaldehyde.<unk>  is a key component of the Mecke reagent used for drug checking. Medical<unk>  can supply the trace element indicated in people as a source of selenium.
Selenous acid
Hydrogen fluoride
Carbonated water
Biotin
Dichloroacetic acid
Selenium disulfide
Trace amine
Sucrosomial iron