Cover illustration: Interpenetrating supramolecular lattices in 4,4'-bipyridine-2,3,5,6-tetrahydroxy-1,4-benzoquinone (3/2). The molecules of the title adduct are shown with 50% probability displacement ellipsoids. The dashed lines indicate hydrogen bonds. See Cowan, Howard & Leechn [Acta Cryst. (2001), C57, 1196-1198].
From a single crystal, the molecular and crystal structures of the high-temperature phase of nitric acid dihydrate have been determined, and indicate a three-dimensional hydrogen-bond network involving NO3− and H5O2+ ionic groups.