Characteristic

 

Disodium phosphate (DSP), or sodium hydrogen phosphate, or sodium phosphate dibasic, is the inorganic compound with the formula Na₂HPO₄. It is one of several sodium phosphates. The salt is known in anhydrous form as well as forms with 2, 7, 8, and 12 hydrates. All are water-soluble white powders; the anhydrous salt being hygroscopic.

Chemical formula:Na₂HPO₄

Molar mass:141.96 g/mol (anhydrous);177.99 g/mol (dihydrate);268.07 g/mol (heptahydrate)

Appearance:White crystalline solid

Odor:odorless

Density:1.7 g/cm³

Melting point:250 °C (482 °F; 523 K) decomposes

Solubility in water:7.7 g/100 ml (20 °C);11.8 g/100 mL (25 °C, heptahydrate)

Solubility:insoluble in alcohol

log P:-5.8

Acidity (pKa):2.15, 6.82, 12.35

Magnetic susceptibility (χ):−56.6·10⁻⁶ cm³/mol

Refractive index (nD):1.35644..1.35717 at 20°C

 

Application

 

Sodium hydrogen phosphate is widely used in detergents and cleaning agents. Combined with trisodium phosphate, it is employed in the food industry to adjust the pH and in water treatment to prevent calcium scale formation. It is utilized as a saline laxative to clean the bowel before a colonoscopy. It prevents the coagulation of condensed milk. It is also utilized as anti-caking additive in powdered products. It enhances the cook time and used as thickening agent in desserts and puddings.