Sodium bicarbonate, commonly known as the active ingredient in baking soda, is useful medicinally to relieve heartburn and acid indigestion; as a leavening agent in cooking; as a cleaning agent to help with scrubbing and in toothpaste for personal hygiene. In addition, it is also useful to absorb musty smells and can be added to pools, spas and garden ponds to raise pH levels.
Sodium bicarbonate acts as a leavening agent by reacting with the acidic components in batter, releasing carbon dioxide and causing the batter to expand. Ancient Egyptians used it as a cleaning agent as well. In addition, the novel "Captains Courageous" by Rudyard Kipling mentions its extensive use during the 1800s in commercial fishing to prevent freshly caught fish from spoiling.
Sodium bicarbonate is naturally found dissolved in mineral springs. It is also produced in pure form from sodium carbonate, water and carbon dioxide or by reacting carbon dioxide with an aqueous solution of sodium hydroxide. Baking powder contains sodium bicarbonate, but it also contains a powdered acid and cornstarch. This is done to neutralize the metallic taste that baking soda creates during the baking process, which is due to its chemical change into sodium carbonate.