FIG. 13-17 Effect of mixture composition upon K value for n-pentane at 104°C (220°F). K values are shown for various values of W, weight fraction propane on a methane-free basis for the methane-propane-pentane system. [Hadden, Chem. Eng. Prog. Symp. Sec. 7, 49, 58 (1953).]
lerazums exceed values of approximately 7.5, the van Laar equation erroneously predicts phase splitting.
Tables 13-1, 13-2, and 13-4 include data on formic acid and acetic acid, two substances that tend to dimerize in the vapor phase according to the chemical-equilibrium expression
where KD is the chemical-equilibrium constant for dimerization, PD and PM are partial pressures of dimer and monomer respectively in torr, and T is in K. Values of A and B for the first four normal aliphatic acids are:
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