Can identical crystals melt into two distinct liquids?

Seemingly identical molecular crystals of acetaldehyde phenylhydrazone (APH), C8H10N2, are reported to melt to liquids with distinctly different structures, and with different melting points of between 60 and 100 C. The low- or high-melting forms can be reliably prepared by exposure of crystals to trace acid or base (as little as 1/1000th molar equivalent) respectively, with no detectable change to the crystal structure. Although rare, this remarkable and strange behavior demands further investigation. It has implications for our fundamental understanding of phase transitions (kinetics and thermodynamics), the structure of liquids and relaxation phenomena in general. This experiment will provide new information on the intermolecular interactions at play, possible temperature dependence of the isomer ratio and the purported E-isomer crystal form.