Potassium Phosphate - Monobasic: Potassium biphosphate or acid phosphate; potassium dihydrogen phosphate; monopotassium phosphate. KH2PO4; mol. wt. 136.09. Colorless crystals or white, granular powder; permanent in air; at 400° loses H2O, forming metaphosphate. d. 2.34. Soluble in about 4.5 parts water; insoluble in alcohol. pH: 4.4-4.7.
Use: Monopotassium phosphate is used in buffers for determination of pH.
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.
Monopotassium phosphate 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)
Also to be noted is KDP, 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. EPA: Potassium dihydrogen phosphate Fact Sheet
