July 2006 issue
Cover illustration: The monoclinic polymorph of the 1:1 adduct of sulfathiazole with pyridine is unstable in air, losing pyridine to give sulfathiazole. After its discovery it could not be obtained again, only the tetragonal polymorph whose structure is also reported in this issue. Thus it would appear that the monoclinic form belongs to the interesting class of disappearing polymorphs. See Drebushchak, Mikhailenko, Boldyreva & Shakhtshneider [Acta Cryst. (2006), E62, o2707-o2709].