Baking powder is used in baking recipes (to aerate & make them light) that don't have acidic ingredients like Molasses, buttermilk or vinegar. It helps baked goods rise while baking soda is an even more powerful leavener & also neutralizes acidic ingredients. So, for example, a smidge of baking soda in your tomato sauce can lower that acidic taste ... Here's how you can substitute one for the other if you don't have both on hand .... | Alex Guarnaschelli