Monopotassium phosphate
IUPAC name	Potassium dihydrogenphosphate
Other names	Monopotassium phosphate; Potassium phosphate monobasic; Phosphoric acid, monopotassium salt
Identifiers
CAS number	7778-77-0
Properties
Molecular formula	KH2PO4
Molar mass	136.09 g/mol
Appearance	White powder
Density	2.34 g/cm3, solid
Melting point	235°C
Boiling point	400°C, dec
Solubility in water	22 g/100 ml
Hazards
MSDS	[http://www.jtbaker.com/msds/englishhtml/p6038.htm
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, and is 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 52% P₂O₅ and 34% K₂O, and is labeled 0-52-34. Although the words in the preceding sentence are often used in this way by laymen, both substances are not present in the fertilizer. On the other hand, the fertilizer contains the same amount of potassium and phosphorus as would be present in the mentioned amounts of K₂O and P₂O₅. Monopotassium phosphate is often used as a nutrient source in the greenhouse trade and in hydroponics.

It is one of the components of Gatorade and is used as an additive in cigarettes.

At 400°C 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 ~1,064nm 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

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External links

• EPA: Potassium dihydrogen phosphate Fact Sheet
• Potassium Phosphate - a Hydroculture Salt