Monopotassium phosphate

Monopotassium phosphate
IUPAC name Potassium dihydrogen phosphate
Other names Potassium phosphate monobasic Phosphoric acid, monopotassium salt
Identifiers
CAS number	7778-77-0 Y
PubChem	516951
ChemSpider	22914 N
UNII	4J9FJ0HL51 Y
RTECS number	TC6615500
Jmol-3D images	Image 1
SMILES [K+].[K+].[K+].[O-]P([O-])([O-])=O
InChI InChI=1S/3K.H3O4P/c;;;1-5(2,3)4/h;;;(H3,1,2,3,4)/q3*+1;/p-3 N Key: LWIHDJKSTIGBAC-UHFFFAOYSA-K NInChI=1/3K.H3O4P/c;;;1-5(2,3)4/h;;;(H3,1,2,3,4)/q3*+1;/p-3 Key: LWIHDJKSTIGBAC-DFZHHIFOAX
Properties
Molecular formula	KH2PO4
Molar mass	136.086 g/mol
Appearance	White powder deliquescent
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	insoluble in alcohol
Acidity (pKa)	7.2
Basicity (pKb)	11.9
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 phosphate (verify) (what is: Y/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^{[citation needed]}.

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 ~1,064 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