Anhydride, << an HY dryd, >> is a chemical substance that forms acids or bases when combined with water. For example, water and acetic anhydride, an acid anhydride, make acetic acid. Water and calcium oxide, a basic anhydride, make basic calcium hydroxide. Anhydrides can be formed by dehydrating (removing the water from) compounds or by synthesizing (making) them directly from other substances. Anhydrides are used in the manufacture of artificial fibers, plastics, photographic films, and medicines. See also Acid ; Base .
