A mixture of powdered compounds added to dough or cake mixture to make it rise in cooking. It is used as a substitute for yeast in bread-making. Baking powders consist of a source of carbon dioxide, such as sodium hydrogencarbonate or ammonium hydrogencarbonate, and an acidic substance such as calcium hydrogenphosphate, potassium hydrogentartrate (cream of tartar), or sodium hydrogenphosphate. In the hot wet mixture, the acid releases bubbles of carbon dioxide gas from the hydrogencarbonate, which make the mixture rise.