Have a stable I-type and sub-stable type Ⅱ. White crystal or crystalline powder. Into a chain molecular structure. Six objects are hygroscopic water. Soluble in water, weakly alkaline aqueous solution gradually decomposes sodium ion, pyrophosphate ion and phosphate ions. Heated to 622 ℃ melt, resulting in sodium pyrophosphate. Used in meat processing, synthetic detergent formulations (with synergies), textile dyeing, also used as a dispersing agent, to help solvent. By the member, and two molecules of sodium dihydrogen phosphate, disodium hydrogen phosphate fully mixed, heated to 110 ℃ dehydration, continue heated to 540-580 ℃ dehydration made-I. And then heated to 620 ℃ and above melting, reduce temperature to 550 ℃, in the air cooling, which collapse into a powder type Ⅱ. In the aqueous solution by adding anhydrous ethanol, the availability of six water objects.