Products
Sodium dihydrogen phosphate is available as a pure substance in pharmacies and drugstores. It is included as an active ingredient and excipient in pharmaceuticals.
Structure and properties
The pharmacopoeia defines sodium dihydrogen phosphate dihydrate (NaH2PO4 – 2 H2O, Mr = 156.0 g/mol). It exists as a white powder or colorless crystals and is very soluble in water. It is the monosodium salt of phosphoric acid. Sodium dihydrogen phosphate is also used as anhydrate and monohydrate. Sodium dihydrogen phosphate can be prepared from phosphoric acid using sodium hydroxide:
- H3PO4 (phosphoric acid) + NaOH (sodium hydroxide) NaH2PO4 (sodium dihydrogen phosphate) + H2O (water)
Effects
Sodium dihydrogen phosphate reacts weakly acidic in water:
- NaH2PO4 (sodium dihydrogen phosphate) + H2O (water) NaHPO4-1 + H3O+
Conversely, sodium monohydrogen phosphate (Na2HPO4) as a weak base.
Fields of application
- For the treatment of hypophosphatemia, together with sodium monohydrogen phosphate.
- Sodium dihydrogen phosphate, together with sodium hydrogen carbonate, is contained in suppositories, which are used as laxatives. In the rectum, the substances form carbon dioxide (CO2), which triggers the defecation reflex (lecicarbon).
- As a pharmaceutical excipient, especially for liquid dosage forms such as injection solutions and eye drops. For the preparation of a phosphate buffer, usually together with sodium monohydrogen phosphate and an acid or base.
- As a food additive, as an acidity regulator and complexing agent.
