Sodium acid pyrophosphate (SAPP) is an important component of double acting baking powder as well as self rising flour. SAPP reacts in stages and is desirable in baking applications for its slow action. SAPP has Chemical formula: Na2H2P2O7 and Molecular Weight: 221.94.
it is White crystalline powder or granules and Soluble in water
Initially, when moisture is added to form a dough, SAPP reacts with baking soda (sodium bicarbonate) to produce carbon dioxide gas. In fact, 22-40% of gas is released during this initial two minute mix. The remaining gas, over 50%, is released when heat is applied during the baking process.