Monopotassium phosphate
Monopotassium phosphate (MKP) (also, potassium dihydrogen phosphate, KDP, or monobasic potassium phosphate) is the inorganic compound with the formula KH2PO4. Together with dipotassium phosphate (K2HPO4.(H2O)x) it is often used as a fertilizer, food additive, and buffering agent. The salt often cocrystallizes with the dipotassium salt as well as with phosphoric acid.
Two unit cells of MKP viewed close to the b axis | |
Names | |
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IUPAC names
Potassium dihydrogen phosphate | |
Other names
Potassium phosphate monobasic; Phosphoric acid, monopotassium salt; Potassium biphosphate | |
Identifiers | |
3D model (JSmol) |
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ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.029.012 |
EC Number |
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E number | E340(i) (antioxidants, ...) |
PubChem CID |
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RTECS number |
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UNII | |
CompTox Dashboard (EPA) |
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Properties | |
KH 2PO 4 | |
Molar mass | 136.086 g/mol |
Appearance | Colourless crystals or white granular or crystalline powder |
Odor | Odorless |
Density | 2.338 g/cm3 |
Melting point | 252.6 °C (486.7 °F; 525.8 K) |
Boiling point | 400 °C (752 °F; 673 K) , decomposes |
22.6 g/100 mL (20 °C) 83.5 g/100 mL (90 °C) | |
Solubility | Slightly soluble in ethanol |
Acidity (pKa) | 6.86 |
Basicity (pKb) | 11.9 |
Refractive index (nD) |
1.4864 |
Structure | |
Tetragonal | |
I42d | |
a = 0.744 nm, b = 0.744 nm, c = 0.697 nm | |
Hazards | |
GHS labelling: | |
Warning | |
H315, H319 | |
P264, P280, P305+P351+P338, P321, P332+P313, P337+P313 | |
NFPA 704 (fire diamond) | |
Flash point | Non-flammable |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose) |
3200 mg/kg (rat, oral) |
Safety data sheet (SDS) | External MSDS |
Related compounds | |
Other cations |
Monosodium phosphate Monoammonium phosphate |
Related compounds |
Dipotassium phosphate Tripotassium phosphate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references |
Single crystals are paraelectric at room temperature. At temperatures below −150 °C (−238 °F), they become ferroelectric.
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