Baking soda is a type of baking powder that consists of sodium bicarbonate, an alkaline salt. It is used as a leavening agent in baking to make cakes and breads rise. Baking powder also contains an acidic salt, such as cream of tartar, which reacts with the baking soda to produce carbon dioxide gas. This gas causes the dough or batter to rise when it is baked. Some people claim that baking soda is also a source of citric acid, but this is not true. Citric acid is a sour-tasting compound found in citrus fruits and other foods. It has a number of uses, including as a preservative, flavor enhancer and antioxidant. Baking soda does not contain citric acid and cannot be used as a substitute for it. However, you can use baking soda to make your own citric acid. All you need is lemon juice and baking soda. The lemon juice will provide the acidic salt needed to react with the baking soda and produce carbon dioxide gas. Simply mix together equal parts of lemon juice and baking soda, and you will have a powerful cleaning agent that can also be used in cooking and baking. Citric acid is also available in powder or crystal form from most health food stores.