Prussic acid, also known as hydrocyanic acid, is called prussic acid because it was first obtained from a dark blue solid substance called Prussian blue . The pure acid is a clear liquid. It has a low boiling point and evaporates quickly at room temperature. The acid has a faint odor of bitter almonds. It interferes with the body’s ability to use oxygen and is one of the most poisonous substances known. Hydrocyanic acid gas has been used to execute condemned criminals. The gas is created when lumps of sodium or potassium cyanide are dropped into sulfuric acid. Hydrocyanic acid is also used to control the scale insect on orange trees. The acid’s chemical formula is HCN. The salts of this acid have many industrial uses.
