Potassium dihydrogen phosphate

Potassium dihydrogen phosphate

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Monopotassium phosphate
Identifiers
CAS number 7778-77-0 YesY
PubChem 516951
ChemSpider 22914 N
UNII 4J9FJ0HL51 YesY
RTECS number TC6615500
Jmol-3D images Image 1
Properties
Molecular formula KH2PO4
Molar mass 136.086 g/mol
Appearance White powder
deliquescent
Odor odorless
Density 2.338 g/cm3
Melting point

252.6 °C

Boiling point

400 °C, dec

Solubility in water 22 g/100 mL (25 °C)
Solubility slightly soluble in ethanol
Acidity (pKa) 7.2
Basicity (pKb) 11.9
Refractive index (nD) 1.4864
Structure
Crystal structure tetragonal
Hazards
MSDS External MSDS
EU Index Not listed
NFPA 704
0
1
0
Flash point Non-flammable
Related compounds
Other cations Monosodium phosphate
Monoammonium phosphate
Related compounds Dipotassium phosphate
Tripotassium phosphate
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Monopotassium phosphate (also potassium dihydrogen phosphate, KDP, or monobasic potassium phosphate, MKP) -- KH2PO4 -- is a soluble salt which is used as a fertilizer, a food additive and a fungicide. It is a source of phosphorus and potassium. It is also a buffering agent. When used in fertilizer mixtures with urea and ammonium phosphates, it minimizes escape of ammonia by keeping the pH at a relatively low level.

Fertilizer grade MKP contains the equivalent of 52% P2O5 and 34% K2O, and is labeled 0-52-34. MKP is often used as a nutrient source in the greenhouse trade and in hydroponics.

It is one of the components of Gatorade (used as both an emulsifier and pH buffer) and is used as an additive in cigarettes.

At 400 °C, 752 °F it decomposes, by loss of water, to potassium metaphosphate (KPO3)

Nonlinear optics use

As a crystal, it is noted for its non-linear optical properties. Used in optical modulators and for non-linear optics such as SHG (second-harmonic generation).

Also to be noted is KD*P, Potassium dideuterium phosphate, with slightly different properties. Highly deuterated KDP is used in nonlinear frequency conversion of laser light instead of protonated (regular) KDP due to the fact that the replacement of protons with deuterons in the crystal shifts the third overtone of the strong OH molecular stretch to longer wavelengths, moving it mostly out of the range of the fundamental line at ~1,064 nm of neodymium-based lasers. Regular KDP has absorbances at this wavelength of around 4.7-6.3%/cm of thickness while highly deuterated KDP has absorbances of typically less than .8%/cm.

Gallery

References

External links

  • International Chemical Safety Card 1608
  • EPA: Potassium dihydrogen phosphate Fact Sheet
  • Potassium Phosphate – a Hydroculture Salt