Also known as bicarbonate of soda, baking soda is used as a leavener in baked goods. When combined with an acid ingredient such as buttermilk, yoghourt or molasses, baking soda produces carbon dioxide gas bubbles, thereby causing a dough or batter to rise. Because it reacts immediately when moistened, it should always be mixed with the other dry ingredients before adding any liquid; the resulting batter should be placed in the oven immediately. At one time, baking soda was used in the cooking water of green vegetables to preserve their color. That practise was discontinued, however, when it was discovered that baking soda destroys the vitamin C content of vegetables.