Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate and a weak acid. The base and acid are prevented from reacting prematurely by the inclusion of a buffer such as cornstarch. Baking powder is used to increase the volume and lighten the texture of baked goods. It works by releasing carbon dioxide gas into a batter or dough through an acid–base reaction, causing bubbles in the wet mixture to expand and thus leavening the mixture. The first single-acting baking powder was developed by food manufacturer Alfred Bird in England in 1843. The first double-acting baking powder was developed by Eben Norton Horsford in the United States of America in the 1860s.