Conveniently prepd from NaPO3 + Na2S: Zintl, Bertram, Z. Anorg. Allg. Chem. 245, 16 (1940); from PSCl3 + NaOH: Tridot, Tudo, Bull. Soc. Chim. Fr. 1960, 1231. Several alternate routes, e.g. from P2S5 and NaOH, see Klement in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 569-570.