What is baking soda made out of?

Baking soda, as defined by ChemicalFormula.org, is a white powder comprised of sodium bicarbonate, also known as sodium hydrogen carbonate. The chemical symbol for sodium bicarbonate is NaHCO3.

Sodium bicarbonate is used in baking as a leavening agent. It reacts with acidic ingredients such as vinegar, buttermilk and yogurt to produce carbon dioxide bubbles, which in turn, provide lift to baking goods while neutralizing the acid. Used in accordance with a manufacturer's directions, its ability to neutralize acid makes it useful as a stomach antacid for countering heartburn or upset stomach. It is also used as a mild cleaning agent and deodorizer and is often used as an ingredient in toothpaste.