The active ingredients in baking powder are sodium bicarbonate and cream of tartar. Cream of tartar is a dry acid that is also known as sodium aluminum sulfate.
Baking powder is inactive in its dry form, but mixing it with a liquid causes a chemical reaction that forms carbon dioxide gas. This gas forms small bubbles in the liquid. Baking powder is a convenient leavening agent for baked goods because it works instantly and has a long shelf life. It is the bubbles, formed by the release of carbon dioxide, that cause dough and bread to rise.
Sodium bicarbonate is useful for extinguishing small fires and is a popular alternative to commercial cleaners for many jobs around the home. It is also useful in skin care and personal hygiene and for relieving indigestion.