KH2PO4

Potassium dihydrogen phosphate (KH2PO4), commonly known as monobasic potassium phosphate, is the potassium salt of phosphoric acid. It consists of a potassium cation and the dihydrogen phosphate anion (H2PO4−). It is a colorless, crystalline solid that is highly soluble in water and commonly encountered as a crystalline, hygroscopic material.

KH2PO4 solutions are mildly acidic, with a pH around 4 at moderate concentrations. In solid form it is stable under normal storage conditions but is hygroscopic and can absorb moisture from the air. It can crystallize from aqueous solutions and forms the basis for related phosphate salts used in buffers and fertilizers.

Preparation of KH2PO4 typically involves partial neutralization of phosphoric acid with potassium bases, for example H3PO4 + KOH → KH2PO4 + H2O. The compound is then crystallized from solution and dried. It serves as a convenient source of both potassium and phosphorus in various chemical applications, and it can be converted into other phosphate derivatives.

Applications include use as a buffering agent in biochemical and molecular biology procedures, where KH2PO4 helps maintain stable pH in phosphate-buffered solutions. It is also employed as a nutrient source in agriculture and animal feeds, providing potassium and phosphorus. In industry, KH2PO4 is a precursor for the preparation of potassium dihydrogen phosphate crystals (KDP) used in nonlinear optical materials and laser technologies.

Safety considerations are modest; KH2PO4 is of relatively low toxicity but dust can irritate eyes, skin, and the respiratory tract. Appropriate handling includes avoiding inhalation of dust, using eye and skin protection, and storing in a cool, dry place away from incompatible materials.