Disodium phosphate (DSP), or disodium hydrogen phosphate, or sodium phosphate dibasic, is the

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemis ...

with the formula Na₂HPO₄. It is one of several

sodium phosphates Sodium phosphate is a generic term for a variety of salts of sodium (Na+) and phosphate (PO43−). Phosphate also forms families or condensed anions including di-, tri-, tetra-, and polyphosphates. Most of these salts are known in both anhydrou ...

. 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 Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance' ...

. The pH of disodium hydrogen phosphate water solution is between 8.0 and 11.0, meaning it is moderately basic: :HPO₄²⁻ + H₂O H₂PO₄⁻ + OH⁻

Production and reactions

It can be generated by neutralization of phosphoric acid with sodium hydroxide: :H₃PO₄ + 2 NaOH → Na₂HPO₄ + 2 H₂O Industrially It is prepared in a two-step process by treating dicalcium phosphate with

sodium bisulfate Sodium bisulfate, also known as sodium hydrogen sulfate, is the sodium salt of the bisulfate anion, with the molecular formula NaHSO4. Sodium bisulfate is an acid salt formed by partial neutralization of sulfuric acid by an equivalent of sodium ...

, which precipitates calcium sulfate:Klaus Schrödter, Gerhard Bettermann, Thomas Staffel, Friedrich Wahl, Thomas Klein, Thomas Hofmann "Phosphoric Acid and Phosphates" in ''Ullmann’s Encyclopedia of Industrial Chemistry'' 2008, Wiley-VCH, Weinheim. :CaHPO₄ + NaHSO₄ → NaH₂PO₄ + CaSO₄ In the second step, the resulting solution of monosodium phosphate is partially neutralized: :NaH₂PO₄ + NaOH → Na₂HPO₄ + H₂O

Uses

It is used in conjunction with trisodium phosphate in foods and water softening treatment. In foods, it is used to adjust pH. Its presence prevents coagulation in the preparation of condensed milk. Similarly, it is used as an anti-caking additive in powdered products. It is used in desserts and puddings, e.g. Cream of Wheat to quicken cook time, and Jell-O Instant Pudding for thickening. In water treatment, it retards calcium scale formation. It is also found in some detergents and cleaning agents. Heating solid disodium phosphate gives the useful compound

tetrasodium pyrophosphate Tetrasodium pyrophosphate, also called sodium pyrophosphate, tetrasodium phosphate or TSPP, is an inorganic compound with the formula Na4P2O7. As a salt, it is a white, water-soluble solid. It is composed of pyrophosphate anion and sodium ions. ...

: :2 Na₂HPO₄ → Na₄P₂O₇ + H₂O

Laxative

Monobasic and dibasic sodium phosphate are used as a

saline laxative Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation. Laxatives vary as to how they work and the side effects they may have. Certain stimulant, lub ...

to treat

constipation Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the bowel moveme ...

or to clean the bowel before a

colonoscopy Colonoscopy () or coloscopy () is the endoscopic examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It can provide a visual diagnosis ('' ...

References

External links

* solubility in Prophylaxis alcohol {{Sodium compounds Sodium compounds Phosphates Edible thickening agents