Diaqua-bis-(hydrogen tartrato)cobalt(II) dihydrate.

The title complex, [Co(C(4)H(5)O(6))(2)(H(2)O)(2)]·2H(2)O, contains a Co(II) ion, two single deprotonated tartrate anions, two coordinated water mol-ecules and two lattice water mol-ecules. The coordination geometry of the Co(II) ion is a distorted octa-hedron with two O atoms from two coordinated water mol-ecules occupying cis positions in the equatorial plane and four O atoms from two hydrogen tartrate ions occupying the remaining positions. In the crystal, inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into a three-dimensional network.