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.

Monopotassium phosphate

Two unit cells of MKP viewed close to the b axis
Names
IUPAC names
Potassium dihydrogen phosphate
Other names
Potassium phosphate monobasic;
Phosphoric acid, monopotassium salt;
Potassium biphosphate
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.029.012
EC Number
  • 231-913-4
E number E340(i) (antioxidants, ...)
RTECS number
  • TC6615500
UNII
  • InChI=1S/3K.H3O4P/c;;;1-5(2,3)4/h;;;(H3,1,2,3,4)/q3*+1;/p-3 Y
    Key: LWIHDJKSTIGBAC-UHFFFAOYSA-K Y
  • InChI=1/3K.H3O4P/c;;;1-5(2,3)4/h;;;(H3,1,2,3,4)/q3*+1;/p-3
    Key: LWIHDJKSTIGBAC-DFZHHIFOAX
  • [K+].OP(O)([O-])=O
Properties
KH
2
PO
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/100mL (20 °C)
83.5 g/100mL (90 °C)
Solubility Slightly soluble in ethanol
Acidity (pKa) 6.86
Basicity (pKb) 11.9
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)
1
0
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
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).
N verify (what is YN ?)
Infobox references

Single crystals are paraelectric at room temperature. At temperatures below −150 °C (−238 °F), they become ferroelectric.

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