Schematic of experimental procedure. Step 1: mix hydrocarbons in gaseous phase using the 0.5-liter mixing chamber. Step 2: deposit hydrocarbon mixture into the precooled 90 K thick cell, where it condenses into liquid. Step 3: if 85 K experiment, cool the cell and mixture to 85 K, and then pressurize with N₂ in 0.1-bar increments; if 90 K experiment, start adding N₂. Repeat N₂ additions until a phase change occurs or pressure reaches 3.0 bars.