Prepd by treating white phosphorus with barium hydroxide: 8P + 3Ba(OH)2.8H2O + H2O → 3Ba(H2PO 2)2.H2O + 2PH3: Rose, Pogg. Ann. 9, 370 (1827); Klement in Handbook of Preparative Inorganic Chemistry Vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) p 557.