The experimental determination of equilibrium curves

The phase equilibria of binary and multicomponent mixtures are essential for the determination of the plate number required for a separation and of other distillation requirements. 

The vapour-liquid equilibria published up to 1933 have been collected in the book of Landolt and Bornstein [99]. Equilibrium data are also to be found in books by Perry [100], Yu Chin Chu [101] and Chu, Wang, Levy and Paul [102]. 

One of the most extensive compilations of phase equilibrium data at normal pressure was published by Hala et al. [106] in 1969. PPDS, which is intended to be a long-term project, will be able to provide distillation data on a large scale [106a]. It is noteworthy that Renonhas edited an international journal entitled Fluid-Phase Equilibria since April 1977, which is published by the Elsevier Publishing Company. 

It is particularly important to know the course of the equilibrium curve accurately near its beginning and end for this reason as many points as possible should be determined between 0 and 10 mol% and between 90 and 100 niol%. In general the equilibrium vapour concentration y is measured at the following compositions of the liquid  

The number of points depends, of course, on the nature of the mixture and the use to which the data are to be put in the case of ideal mixtures, intermediate points in the central region may be omitted. 

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