The 4,4'-bipyridine molecules in the title compound, C10H8N2. 2H(2)O, are s
tacked in the direction of the crystallographic b axis. These stacks are co
nnected via O-H . . .N and O-H . . .O hydrogen bonds to form sheets which l
ie parallel to (100). Chains of O-H . . .O hydrogen-bonded water molecules
are located between the bipyridine stacks. Altogether, four crystallographi
cally independent water molecules and two crystallographically independent
bipyridine molecules are involved.