Potassium dihydrogen orthophosphate

Химические свойства

White powder

Физические свойства

Colorless crystals or white granular powder; tetragonal structure; deliquesces; density 2.338 g/cm³; melts at 252.6°C; soluble in water 33 g/100mL at 25°C; pH 4.4-4.7; insoluble in alcohol.

Использование

Potassium Dihydrogen is a buffer, neutralizing agent, and sequestrant. It is mildly acid, with a ph of 4.5, and fairly soluble in water, with a solubility of 25 g in 100 ml at 25°c. It is used in whole eggs for color preservation and is also used in low-sodium products, milk products, and meat products. Typical usage ranges from 0.1 to 0.5%. It is also termed monopotassium phosphate or thophosphate, potassium phosphate monobasic, and monopotassium monophosphate.

Подготовка

Monopotassium phosphate may be prepared by partial neutralization of phosphoric acid with potassium hydroxide in equimolar amounts:H₃PO₄+ KOH →KH₂PO₄+ H₂O.

Общее описание

Monobasic potassium phosphate crystals are colorless, soluble in water and hygroscopic in nature.Upon heating through 187°C, phase transition occurs in KH₂PO₄, crystal system changes from tetragonal to monoclinic, lattice parameters at 195°C are α=7.47?, b =7.33?, c =14.49?, α=?=90° and γ=92.2.

Растворимость в органика

Insoluble to slightly soluble in ethanol, insoluble in alcohol.

Методы очистки

Dissolve it in boiling distilled water (2mL/g), keep on a boiling water-bath for several hours, then filter it through paper pulp to remove any turbidity. Cool rapidly with constant stirring, and the crystals are collected on to hardened filter paper, using suction, washed twice with ice-cold water, once with 50% EtOH, and dried at 105o. Alternative crystallisations are from water, then 50% EtOH, and again water, or from concentrated aqueous solution by addition of EtOH. It is freed from traces of Cu by extracting its aqueous solution with diphenylthiocarbazone in CCl4, followed by repeated extraction with CCl4 to remove traces of diphenylthiocarbazone.