Description
Disodium phosphate (DSP), is a versatile inorganic compound available in several grades, with the primary distinction being the level of purity and hydration. The two most common forms are anhydrous (Na2HPO4) and various hydrates, such as the dihydrate, heptahydrate, and dodecahydrate, which contain water molecules in their crystal structure.
Chemical Properties
| Property | Description / Value |
| Chemical name | Disodium Phosphate |
| Synonyms | Sodium phosphate dibasic |
| Chemical formula | Na₂HPO₄ (commonly hydrated: Na₂HPO₄·xH₂O) |
| Molecular weight | 141.96 g/mol (anhydrous) |
| Chemical class | Inorganic phosphate salt |
| Appearance | White crystalline powder or granules |
| Odor | Odorless |
| Taste | Saline / slightly alkaline (do not taste in practice) |
| pH (1% aqueous solution, 25 °C) | 8.5 – 9.5 |
| Solubility in water | Freely soluble |
| Solubility in alcohol | Insoluble |
| Hygroscopic nature | Slightly hygroscopic |
| Thermal behavior | Decomposes on strong heating |
| Decomposition products | Sodium oxides, phosphorus oxides |
| Acid–base nature | Mildly alkaline |
| Buffering capacity | Good buffering agent |
| Oxidizing/reducing nature | Neither oxidizing nor reducing |
| Ionic nature | Ionic compound |
| Stability | Stable under normal storage conditions |
| Incompatibilities | Strong acids, strong oxidizing agents |
Common Grades and Purity Levels
Food Grade: This grade is “Generally Recognized as Safe” (GRAS) by regulatory bodies like the FDA for use as a food additive. It must meet stringent purity specifications, with minimum assay (purity) typically ranging from 98% to over 99%. Food-grade DSP is used as an emulsifier, buffering agent, and stabilizer in products like processed cheeses, evaporated milk, and instant puddings.
Pharmaceutical Grade: This is a high-purity grade that meets the standards of pharmacopoeias such as the United States Pharmacopeia (USP) or British Pharmacopoeia (BP). It’s used as a pH buffering agent in medications and as a laxative. The purity of this grade is generally 98% to 101% (on a dried basis) and has very low levels of impurities like heavy metals, sulfates, and chlorides.
Technical/Industrial Grade: With a typical purity of 98% or more, this grade is used for industrial applications where strict purity isn’t required. It serves as a scale inhibitor in water treatment, a pH regulator in industrial processes, and a component in detergents and metal cleaners.
Laboratory/Reagent Grade: This grade, like the ACS (American Chemical Society) grade, is used in laboratory settings for analytical and research purposes. It has a high purity level, often over 99%, with defined and very low levels of specific impurities to ensure consistent and reliable results in chemical reactions and experiments.
Reviews
There are no reviews yet.