The design of processes using cryogenic fluid mixtures requires fluid property data, which is unavailable today. In particular, this data is crucial to develop cryogenic mixed-refrigerant cycles for high-temperature superconductor (HTS) applications and to further optimize hydrogen liquefaction processes. CryoPHAEQTS, which is currently being built at KIT, will provide physical property data for fluid mixtures in a temperature range of 15–300K and at pressures up to 15 MPa, including also mixtures with either flammable or oxidizing components (e.g. hydrogen, deuterium, oxygen). By direct sampling from an equilibrium cell, vapor-liquid equilibria (VLE) and vapor-liquid-liquid equilibria (VLLE) can be determined using gas chromatography. Solid-liquid equilibria (SLE) are measured using a calorimetric method. The measurement of heat capacities is implemented by combining two different flow measurement principles. In addition, the test stand offers optical access for a future upgrade with an optical measurement system that allows in-equilibrium measurements of both bulk transport properties by dynamic light scattering (DLS) and surface tension by surface light scattering (SLS).