Critical phenomena and three-liquid-phase equilibrium in the four-component system water – nitromethane – o-xylene – n-heptane
Svetlana I Sinegubova, Ekaterina Danilenko
The composition tetrahedron section of the system water – nitromethane – o-xylene – n-heptane, corresponding to 15 wt% of the latter component, has been studied. It cuts across the three-liquid-phase state region extending from the side water – nitromethane – n-heptane to the side o-xylene – nitromethane – n-heptane. The region mentioned is shown to reduce with increasing temperature, and the critical tie-lines l1K23 and l3K12 converge and shorten. It has been established that the region of critical nodes being shrunk into the tricritical point K123 corresponds to the proportion approx. 33 : 67 between water and nitromethane (by mass), approx 9 wt% of o-xylene, and 125 °C.