The density is 1.949/cm. The melting point is 60°C. There are three types: anhydrous, monohydrate and dihydrate. The anhydrate is a white crystalline powder, slightly hygroscopic, and easily soluble in water. Anhydrous, colorless orthorhombic crystals, easily soluble in water, the aqueous solution is acidic (PH=4.5), insoluble in alcohol, slightly soluble in chloroform. The dihydrate is also very soluble in water, easy to agglomerate in humid air, dehydrated to anhydrous at 100℃, sodium pyrophosphate at 190-210℃, and sodium metaphosphate at 280-300℃. The aqueous solutions are acidic. At present, the main product is dihydrate. Under a certain pH value, it is prepared by the reaction of sodium carbonate and phosphoric acid or by the reaction of disodium hydrogen phosphate and a certain proportion of phosphoric acid, which is easy to agglomerate in humid air.
Uses: used in boiler water treatment, electroplating, tanning, baking powder, fuel additives, detergent, mica, acid retardant, etc. It is also a raw material for preparing sodium hexametaphosphate and polycondensation salt.
