Fluid mixtures at high pressures V. Phase separation and critical phenomena in 18 binary mixtures containing either pyridine or ethanoic acid

Critical p(T) curves have been measured for the nine mixtures methane+, ethane+, ethene+, propane+, butane+, hexane+, octane+, decane+, and carbon dioxide + pyridine, and for the eight mixtures methane+, ethane+, ethene+, propane+, butane+, hexane+, octane+, and carbon dioxide + ethanoic acid. (Methane + ethanoic acid) and (methane or ethane or ethene + pyridine) exhibit an interrupted critical curve. The (liquid + liquid + gas) (llg) three-phase curve for (ethene + pyridine) extends over only a small temperature interval, namely ΔT = 7.2 K, between a lower (LCEP) and an upper critical end point (UCEP), both of which lie above the critical temperature of pure ethene. The p(T) projections of the (solid + liquid + gas) (slg) freezing-temperature depression curves were measured on hydrogen+, methane+, ethane+, ethene+, and carbon dioxide + ethanoic acid. The slg freezing-temperature depression curve for (methane + ethanoic acid) intersects the critical curve, which starts at the critical point of ethanoic acid, at a UCEP of 295.6 K and 102.5 MPa.