Our previous work on sulfuric acid tetrahydrate (SAT) identified a monoclinic high-pressure polymorph, which forms at 5.35 kbar when the tetragonal low-pressure phase is warmed above 235 K. The objective of this proposed experiment is to further investigate the high-pressure polymorphism of SAT using the Paris-Edinburgh cell on PEARL/HiPr. We will first pressure-freeze the liquid phase at room temperature, contraining the high-P melting curve and identifying the liquidus phase under these conditions. Secondly, we will carry out a low-temperature study to form the previously seen monoclinic phase and investigate its behaviour at higher pressures than we could achieve in the gas cell.