Elucidation of the elusive structure and formula of the active pharmaceutical ingredient bismuth subgallate by continuous rotation electron diffraction.

Bismuth subgallate has been used in wound and gastrointestinal therapy for over a century. The combination of continuous rotation electron diffraction and sample cooling finally revealed its structure as a coordination polymer. The structure provides insight regarding its formula, poor solubility, acid resistance and previously unreported gas sorption properties.