Chiral resolution of racemic etiracetam was achieved via co-crystallization with ZnCl₂. Depending on the amount of ZnCl₂ either a stable racemic compound or a stable conglomerate can be obtained. Excess ZnCl₂ triggers the quantitative conversion of the racemate into the conglomerate solid; this unprecedented behaviour was investigated through a racetam/ZnCl₂/solvent phase diagram.