Phosphorus Selenophosphates

By treating melts of the composition P₂Se₅ and P₂Se₃ with concentrated KOH greenish to colourless crystals of an octahedral habit are obtained having a composition corresponding to K₂HPSe₃O + 2½H₂O. When a solution of K₂S is substituted for KOH a thioselenophosphite is crystallised, 2K₂S.P₂Se₃ + 5H₂O. When NaOH is used instead of KOH long greenish prisms of Na₃PSe₃O + 10H₂O are obtained.