How It’s Used Hydrogen cyanide (aka prussic acid, if in aqueous solution; and formonitrile) is a highly volatile, colorless, and extremely poisonous liquid (boiling point at just above room temperature). Its application as a poison is well known, represented in gas chambers and infamously in Zyklon B, used by the Nazis. While these methods of … Continue reading Hydrogen Cyanide—and Hydrogen Cyanide Monitoring Instrumentation