Selenocyanic acid is a chemical compound with the formula HSeCN. This colorless liquid is a powerful oxidizing agent and a reactive precursor to several selenium-containing compounds. Some synonyms for selenocyanic acid include hydrogen selenocyanate, selenium isocyanide, and selenium cyanide hydrate. Selenocyanic acid is commonly used for the preparation of selenocyanate salts, which have various industrial applications. These salts can be used as precursors for manufacturing semiconductors, as additives in electroplating, and in the production of certain pharmaceuticals. Despite its usefulness, selenocyanic acid should be handled with care, as it is a highly toxic and corrosive substance.