in water byproducts: HCl; heating H3PO4 and NaCl until formation of HCl is finished, concg. of melt with H2O (150-250°C, 7-14 atm); addn. of Ca(OH)2 to the filtarte until a ratio of Na2P:P2O5=2;1 is reached, evapn. of filtrate, heating to ca. 550° for 45-60 min;;
