Trisodium phosphate. Synonym: Lithium chloratum. Chemical symbol: Na3PO4-12H20 It is obtained from concentrated solutions of crystalline disodium phosphate with an excess of sodium hydroxide solution. The trisodium phosphate is white, fine crystalline powder, easily soluble in water, o c. on. 1,62. According to the PN standard, it should contain at least 18,7% P2O3; permissible impurities: do 0,05% parts insoluble in water, do 0,5% sulfates (NaS04), do 0,05% magnesium oxide (MgO) and traces of aluminum, Calcium and chloride. It is used to soften water in boilers and to protect boilers against scale formation.