Complex phase equilibrium phenomena in fluid mixtures up to 2 GPa-cosvolency, holes, windows, closed loops, high-pressure immiscibility, barotropy, and related effects

First, the most important experimental techniques are briefly reviewed, inc luding the diamond anvil cell (DAC) technique. As a first example, it is de monstrated that carefully selected type III carbon dioxide binaries exhibit ing gas-gas-like fluid phase behavior can be combined to give a ternary sys tem, which might show large cosolvency effects and, as a consequence, two-p hase holes in the three-phase liquid-liquid-gas sm face and/or one-phase mi scibility windows surrounded by heterogeneous states (e.g., carbon dioxide + 1-decanol + tetradecane). As a second example, type VI binary systems exh ibiting closed immiscibility loops in isobaric temperature (composition) di agrams are considered. With increasing pressure, such closed loops can shri nk or even disappear completely (e.g., tetrahydrofuran + water); have a tub e-like shape, often with a narrowing at medium pressures (e.g., 3-aminopent ane + water); or even appear at high pressures only (so-called "high-pressu re immiscibility", e.g., tetra-n-butylammonium bromide + water). Finally, i sopycnic and barotropic effects are discussed in relation to the phenomena described above.