<P> The most common salt of the bicarbonate ion is sodium bicarbonate, NaHCO, which is commonly known as baking soda . When heated or exposed to an acid such as acetic acid (vinegar), sodium bicarbonate releases carbon dioxide . This is used as a leavening agent in baking . </P> <P> The flow of bicarbonate ions from rocks weathered by the carbonic acid in rainwater is an important part of the carbon cycle . </P> <P> Bicarbonate also serves much in the digestive system . It raises the internal pH of the stomach, after highly acidic digestive juices have finished in their digestion of food . Ammonium bicarbonate is used in digestive biscuit manufacture . </P> <P> In diagnostic medicine, the blood value of bicarbonate is one of several indicators of the state of acid--base physiology in the body . It is measured, along with carbon dioxide, chloride, potassium, and sodium, to assess electrolyte levels in an electrolyte panel test (which has Current Procedural Terminology, CPT, code 80051). </P>

What is the conjugate base of the bicarbonate ion hco3-