CID 24506 (7778-77-0) Physical and Chemical Properties
CID 24506
Potassium dihydrogen phosphate is an inorganic monobasic phosphate salt commonly used as a buffering agent and source of phosphate ions in formulation, analytical and process chemistry applications.
| CAS Number | 7778-77-0 |
| Family | Inorganic phosphate salts |
| Typical Form | Powder or crystalline solid |
| Common Grades | EP |
Potassium dihydrogen phosphate is an inorganic, monobasic phosphate salt consisting of a potassium cation and a dihydrogenphosphate anion. Structurally it contains a tetrahedral phosphorus(V) center bonded to four oxygen atoms, two of which bear hydrogen (–OH) and one of which carries the formal negative charge in the anionic form; the solid exists as an ionic lattice of \(K^+\) and \(H_2PO_4^{-}\). The anion shows extensive resonance stabilization of the P–O bonds and multiple hydrogen-bonding sites, producing high polarity and a substantial topological polar surface area for a small inorganic salt.
As an ionic, non-volatile solid, the compound exhibits classical salt behavior: strong electrolyte character in aqueous solution, good water solubility (see note below), and acidifying behavior because the dihydrogenphosphate anion is the protonated form of the phosphate system. Molecular-level properties include multiple hydrogen-bond donors/acceptors associated with the dihydrogenphosphate anion, no rotatable covalent bonds in the discrete covalent fragment, and a formal net neutral composition as the salt. Industrially and pharmaceutically, this salt is widely used where a soluble source of both potassium and phosphate is required and where mildly acidic buffering is desired; it appears frequently as a component in electrolyte and pharmaceutical formulations.
Common commercial grades reported for this substance include: EP.
Basic Physical Properties
Density
No experimentally established value for this property is available in the current data context.
Melting or Decomposition Point
No experimentally established value for this property is available in the current data context.
Solubility in Water
No experimentally established value for this property is available in the current data context.
Solution pH (Qualitative Behavior)
Aqueous solutions are characteristically acidic to mildly acidic because the dihydrogenphosphate anion (\(H_2PO_4^{-}\)) can act as a Brønsted acid, donating a proton to generate hydrogen phosphate (\(HPO_4^{2-}\)). In practical use the salt is selected to yield acidic buffer systems when combined with its conjugate base; the bulk solution pH depends on concentration and the presence of additional buffering salts. No numeric dissociation constants are provided in the current data context.
Chemical Properties
Acid–Base Behavior
Potassium dihydrogen phosphate is the monobasic member of the potassium phosphate series. The dihydrogenphosphate anion functions as a monoprotic acid relative to the phosphate system: it can donate one proton to form \(HPO_4^{2-}\) and act as a buffer component in the phosphate buffering range. In formulations it serves both as a potassium source and as an acidifying/buffering agent. Explicit pKa values are not included in the present data.
Reactivity and Stability
As an inorganic ionic solid the compound is generally chemically stable under normal storage and handling conditions. It is non-flammable and non-volatile. It will react with strong bases to convert to higher-basicity phosphate salts (e.g., dibasic or tribasic phosphates) and can participate in typical salt metathesis reactions. Thermal decomposition can occur on strong heating, producing condensed phosphate species and oxides at elevated temperatures; no decomposition temperature is specified here. The material’s multiple hydrogen-bonding sites make it hygroscopic under humid conditions in some preparations, so moisture control is relevant for long-term stability.
Molecular and Ionic Parameters
Formula and Molecular Weight
- Molecular formula: H2KO4P
- Molecular weight: \(136.086\,\mathrm{g}\,\mathrm{mol}^{-1}\)
Constituent Ions
- Potassium: \(K^+\) (inorganic cation)
- Dihydrogenphosphate: \(H_2PO_4^{-}\) (monobasic phosphate anion)
The salt is the neutral combination of these ions and dissociates in aqueous media to yield the listed ions.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS number: 7778-77-0
- InChIKey: GNSKLFRGEWLPPA-UHFFFAOYSA-M
- InChI: InChI=1S/K.H3O4P/c;1-5(2,3)4/h;(H3,1,2,3,4)/q+1;/p-1
- SMILES: OP(=O)(O)[O-].[K+]
- Other identifiers: HMDB0303429 (HMDB ID); J43.942H (Nikkaji number); Q415049 (Wikidata)
Synonyms and Common Names
- potassium dihydrogen phosphate
- Monobasic potassium phosphate (preferred)
- Nutrol
Industrial and Commercial Applications
Functional Roles and Use Sectors
Potassium dihydrogen phosphate is used where a soluble source of phosphate and potassium is required and where mildly acidic buffering is desirable. It is commonly employed as a buffering agent and electrolyte component in pharmaceutical and parenteral formulations, in veterinary medicines, and in various multicomponent electrolyte preparations. Laboratory and production uses include preparation of phosphate buffers and use as a reagent in chemical and biochemical protocols.
Typical Application Examples
Typical applications include incorporation into electrolyte solutions and multicomponent pharmaceutical formulations as a potassium and phosphate source and as a pH-control agent; use in buffer preparation for biochemical and analytical procedures; and inclusion in veterinary and human pharmaceutical formulations where controlled provision of phosphate and potassium ions is required. No concise list of proprietary product formulations is provided here.
Safety and Handling Overview
Health and Environmental Hazards
As a simple inorganic phosphate salt, acute toxicity is generally low compared with organic toxicants; however, solid dust or concentrated solutions may cause irritation to eyes, skin, and respiratory mucosa. Ingestion of large amounts may produce gastrointestinal irritation. Environmentally, dissolved phosphate contributes to nutrient loading and can promote eutrophication in aquatic systems if released in significant quantities; discharge should be managed to limit environmental impact. For specific hazard classifications and exposure limits consult product-specific safety documentation.
Storage and Handling Considerations
Store in a cool, dry, well-ventilated area in tightly closed containers to minimize moisture uptake. Avoid generating dust; use local exhaust or other engineering controls when handling powders. Standard personal protective equipment (PPE) such as gloves and eye protection is recommended for routine handling; respiratory protection may be necessary for dusty operations. Avoid mixing with incompatible materials without process review (e.g., strong bases in concentrated form will convert the salt to other phosphate species). For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
Appendix — Selected computed molecular descriptors (from compound characterization): Exact mass \(135.93277702\,\mathrm{Da}\); Monoisotopic mass \(135.93277702\,\mathrm{Da}\); Topological polar surface area \(80.6\,\text{Å}^2\); Hydrogen bond donor count 2; Hydrogen bond acceptor count 4; Rotatable bond count 0; Heavy atom count 6; Formal charge 0; Complexity 49.
