Hydrogen bonds are ubiquitous in materials across the chemical spectrum, from inorganic to biological. They influence the structure, the functionality, and therefore the potential applications of materials in which they are present. Of particular interest are short strong hydrogen bonds. Their presence can lead to interesting phenomena, such as proton migration and proton order-disorder transitions. We propose to carry out a variable pressure experiment on 3,5-pyridinedicarboxylic acid and its fully deuterated derivative (35PDCA). This material contains one of the shortest N-H¿O hydrogen bonds reported and temperature-induced proton migration has been observed in both forms. A variable pressure experiment will enable us to separate the lattice expansion and phonon activation effects on proton/deuteron migration and will thus provide valuable new insight into this phenomenon.