Potassium Phosphate - Monobasic: Potassium biphosphate or acid phosphate; potassium dihydrogen phosphate; mono potassium 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: 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.
MKP 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.
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Di Potassium Phosphate |
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Appearance |
Fine White |
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Purity |
96% min |
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pH 1% |
8.7 - 9.3
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Sulphate |
0.02% max |
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Heavy Metals |
10 ppm max |
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Arsenic |
4 ppm max |
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Moisture |
5% max |
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Insolubles |
0.1% max |
Di potassium phosphate DKP (K2HPO4) - also phosphoric acid, di potassium salt; di potassium hydrogen orthophosphate; potassium phosphate dibasic - is a highly water-soluble salt which is often used as a fertilizer, food additive and buffering agent. DKP is a common source of phosphorus and potassium.
Di potassium hydrogen phosphate. K2HPO4; mol. wt 174.18. White, somewhat hygroscopic granules. Very soluble in water, slightly in alcohol. Converted into pyrophosphate by ignition. The aq. soln. is slightly alkaline to phenolphthalein.
Tri potassium phosphate TKP TPP is a water-soluble ionic salt which has the chemical formula K3PO4. It is used as a food additive for its properties as an emulsifier, foaming agent and whipping agent. In combination with fatty acids, it is a potential antimicrobial agent in poultry processing. As a fertilizer, its proportions of N, P2O5, and K2O are 0-33-67, making it one of the few fertilizer compounds in which the nutrient percentages have a total of 100%.
TKP K3PO4; mol. wt. 212.27. Usually contains about one mol. H2O (9%) and small amount of carbonate. White, deliquesce, granular powder. m. 1340°. Very soluble in water; insoluble in alcohol. The aq. soln. is strongly alkanne. Keep well closed.
