| Calcium Octamolybdate, CaMo8O25.18H2O, or Ca3H14[H2(Mo2O7)6]2.22H2O, separates in prismatic crystals when a solution of the normal molybdate in hydrochloric acid (containing 1 molecule CaMoO4 to 1.75 molecule HCl) is allowed to evaporate. The crystals dissolve readily in hot water. On heating, water is given up, and the residue fuses. An octamolybdate, of composition CaMo8O25.17H2O, separates as an amorphous powder when aqueous solutions containing calcium chloride and sodium tetramolybdate in equivalent proportions are mixed. The precipitate is only slightly soluble in hot water. A dodecamolybdate, CaMo12O37.23H2O, has also been described. |