Document Type


Date of Award


Degree Name

Master of Science in Chemical Engineering - (M.S.)


Chemical Engineering

First Advisor

Joseph Joffe

Second Advisor

C. L. Mantell

Third Advisor

George C. Keeffe


The theory of vapor phase activity coefficients for binary mixtures has been developed. The equations, calculation procedures and sample calculations are presented using two recently proposed methods of Joffe. These methods are then compared to the three methods presented by Engleman.

These two methods have been employed to calculate activity coefficients for 236 experimental points. The deviations of calculated values from experimental values were also determined. The systems considered are Argon - Ethylene, hydrogen - Nitrogen, Methane - Ethane, Methane - n - Butane evaluated over wide ranges of pressure, temperature and mol fraction.

From analysis of the time required by the various methods, limitations of the basic equations and comparison of the calculated % deviations, the specific and general advantages of the individual methods have been evaluated.

Engleman previously determined that the method of Medlich et al. is of greatest all-round utility. The Method of Edmister and Ruby is much less time-consuming but limited to light hydrocarbons. Its accuracy is generally comparable to that of Redlich's Method. The earlier Method of Joffe is more time--consuming than Redlich et al. and seldom as accurate as is the Method of Edmister and Ruby.

The previously proposed Methods of Joffe both appear to be a compromise between the general utility and accuracy of the Method of Redlich et al. and the time economy of Edmister and Ruby. The second recently proposed Method of Joffe is more accurate but more time-consuming than the first recently proposed method; the difference being that the second method involves the calculation of the pseudo-critical properties of the gaseous mixture.



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