酸式焦磷酸钠，化学式Na₂H₂P₂O₇。

酸式焦磷酸钠是一种白色单斜结晶性粉末或熔融状固体，溶于水，不溶于乙醇。稍有吸湿性，吸水后形成六水合物。水溶液用稀酸加热则水解成磷酸。加热至220°C以上时分解生成偏磷酸钠。

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. Pyrophosphate is a polyvalent anion with a high affinity for polyvalent cations, e.g. Ca.