Traits: colorless, transparent crystalline columnar. Weathering in the air easily. 1.52.35.1 ℃ relative density for melting and crystallization of water molecules from 5. 100 ℃ water and salt into a free, 300 ℃ generated when the decomposition of sodium pyrophosphate. Soluble in water, insoluble in alcohol. Aqueous solution was basic. Uses: used as analytical reagent, such as the PH value of the standard configuration and the buffer solution. Fabrics and wood is also used in fire prevention drug agents and the preparation of drought.