Barium Dihydrohypophosphite, Ba(H₂PO₂)₂

Barium Dihydrohypophosphite, Ba(H₂PO₂)₂, is obtained by heating barium hydroxide or barium sulphide solution with phosphorus. It is also formed by the action of water on barium phosphide, or by the action of phosphoretted hydrogen on barium hydroxide solution. It forms flexible monoclinic needles of the monohydrate, Ba(H₂PO₂)₂.H₂O, which are unchanged in air at ordinary temperatures, and lose water at 100° C. It is soluble to the extent of 1 part in 3.5 of cold and 3 of boiling water, but is insoluble in alcohol. Nitric acid transforms it quantitatively into the metaphosphate, and it is decomposed by potassium hydroxide solution, liberating hydrogen and forming barium and potassium phosphites. When strongly heated it forms the pyro- and meta-phosphate in the molecular proportions of 6:1.