On the Polymorphism of Aspirin: Crystalline Aspirin as Intergrowths of Two “Polymorphic” Domains

Aspirin: No end to the headaches? The two known crystalline arrangements of aspirin are so closely related that aspirin crystals form intergrowth structures containing domains of form I and domains of form II. The ratio and distribution of the domains is variable among aspirin samples, raising questions for the definition of the term polymorph in this case.