Disodium pyrophosphate or sodium acid pyrophosphate is an inorganic compound consisting of sodium cations and pyrophosphate anion. It is a white, water-soluble solid that serves as a buffering and chelating agent, with many applications in the food industry. When crystallised from water, it forms a hexahydrate, but it dehydrates above room temperature.

Disodium pyrophosphate is a popular leavening agent found in baking powders. It combines with sodium bicarbonate to release carbon dioxide:

Na₂H₂P₂O₇ + NaHCO₃ → Na₃HP₂O₇ + CO₂ + H₂O

t is available in a variety of grades that affect the speed of its action. Because the resulting phosphate residue has an off-taste, SAPP is usually used in very sweet cakes which mask the off-taste

It is an acid source for reaction with baking soda to leaven baked goods.In baking powder, it is often labeled as food additive E450. Disodium pyrophosphate is also found in frozen hash browns and other potato products, where it is used to keep the color of the potatoes from darkening.

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