Name: Dipotassium phosphate CAS Registry Number: 7758-11-4 Dipotassium phosphate (K2HPO4) - also phosphoric acid, dipotassium salt; dipotassium hydrogen orthophosphate; potassium phosphate, dibasic - is a highly water-soluble salt which is often used as a fertilizer, food additive and buffering agent. It is a common source of phosphorus and potassium.