Good Eats Baking Soda is a gluten free baking aid used as a leavening agent • It releases carbon dioxide when it reacts with acid or heat • Baking soda is an alkaline compound that, when combined with an acid, will produce carbon dioxide gas • The small bubbles of carbon dioxide gas become trapped in batter, causing it to inflate, or rise • Common acids used to cause this reaction include vinegar, lemon juice, buttermilk, yogurt, and cream of tartar