P4→OH- PH3+H2PO2-. Equivalent Weight of Phosphorous in the reaction is (M= molar mass of Phosphorous)

P04→H2P+1O2-                                                                      P04→P-3H3                                                                 increase in ox.state/atom of 'P' = 1                   decrease in ox.state/atom of 'P' = 3increase in ox.state/mole of 'P' =4(1)                 decrease in ox.state/mole of 'P'=4(3)                                              E.W of Phosphorous=M4+M12