Tetra-aqua-bis-(2,3-di-hydro-1,4-benzodioxine-2-carboxyl-ato)calcium(II).

The acid-base reaction of 1,4-benzodioxane 2-carb-oxy-lic acid with calcium carbonate furnished the centrosymmetric title compound, [Ca(C 9 H 7 O 4 ) 2 (H 2 O) 4 ], in which the metal ion is octa-hedrally coordinated by two monodentate 1,4-benzodioxane 2-carboxyl-ate ligands and four water mol-ecules. In the crystal, O-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules into a three-dimensional network.