Potassium dihydrogen phosphate (chemical formula: KH2PO4) is sealed and stored in air. It is stable in the air and loses water at 400°C. It turns into metaphosphate. It is used to prepare buffers for the determination of arsenic, antimony, phosphorus, aluminum and iron and to prepare a standard solution of phosphorus. The culture medium was prepared and the inorganic phosphorus and alkaline phosphatase activities in serum were measured.