Wikipedia
Monosodium phosphate
Monosodium phosphate (MSP), also known as anhydrous monobasic sodium phosphate and sodium dihydrogen phosphate, is an inorganic compound of sodium with dihydrogen phosphate (HPO) anion. One of many sodium phosphates(such as NaPO3), it is a common industrial chemical. It exists as an anhydrous salt, as well as mono- and dihydrates.