lunar caustic: see silver nitrate.

caustic soda: see sodium hydroxide.

caustic potash: see potassium hydroxide.

caustic lime: see calcium oxide.

caustic, any strongly corrosive chemical substance, especially one that attacks organic matter. A caustic alkali is a metal hydroxide, especially that of an alkali metal; caustic soda is sodium hydroxide, and caustic potash is potassium hydroxide. Silver nitrate is another caustic substance; it is sometimes called lunar caustic. Most inorganic acids, e.g., sulfuric acid, are caustic, especially when concentrated.

Inorganic compound (AgNO₃), colourless, transparent crystals with a bitter, caustic, metallic taste. The most important silver compound, it is used to prepare other silver salts, to silver mirrors, and as a reagent in analysis. It is very soluble in water; dilute solutions are effective against gonococcal bacteria and may be applied to newborns' eyes to prevent blindness from gonorrhea. Ingesting silver nitrate causes violent abdominal pain and gastroenteritis.

Learn more about silver nitrate with a free trial on Britannica.com.