| Potassium Tetramolybdate, Potassium Metamolybdate, K2Mo4O13.7H2O or K6H4[H2(Mo2O7)6].18H2O, is obtained as a heavy microcrystalline precipitate on warming a solution of sodium octamolybdate with potassium chloride. It forms transparent prismatic crystals, slightly soluble in water. On boiling with water it yields the trimolybdate. The tetramolybdate is also formed in solution when molybdic acid (4 molecules) is treated with potassium carbonate (1 molecule); the reacting mixture must be kept cool or the trimolybdate is obtained. |