In chemistry, an anhydride is a compound that can be considered as derived from another compound by subtracting the molecules of water. For example: » 2 NaOH - H2O → Na2O H2SO4 - H2O → SO3 Thus sodium oxide is an anhydride of sodium hydroxide, and sulfur trioxide is an anhydride of sulfuric acid. In organic chemistry, the compounds most commonly involved are carboxylic acids. » 2 CH3COOH - H2O → (CH3CO)2O Compounds involved are often acids or bases; in such cases, the anhy… (More on Anhydride)