Activity coefficients and excess Gibbs energy of binary mixtures of N,N-dimethyl formamide with selected compounds at 95.5 kPa
Introduction
N,N-Dimethyl formamide is a widely used aprotic solvent and reagent in organic synthesis and chemical analysis. The uses of the other components chosen for this study as solvents and in other applications needs no fresh mention. Information leading to the vapor–liquid equilibrium of the binary mixtures of N,N-dimethyl formamide with the selected compounds is expected to be of use in the design and operation of the separation processes for the compounds contained in the mixtures. This investigation, on the bubble point temperatures of the binary mixtures noted in the abstract, is a continuation of our recent studies on the phase equilibrium of the binary mixtures containing hydrocarbons or alcohols [1], [2]. We could not locate any phase equilibrium data on the selected mixtures for comparison.
Section snippets
Methods
A Swietoslawski-type ebulliometer, very similar to the one described by Hala et al. [3] is used for this experimental investigation. Connection of the ebulliometer to a good vacuum system and dry nitrogen gas cylinder helped in the creation and maintenance of the chosen pressure within ±0.05 kPa of the selected value of 95.5 kPa. An open end manometer, provided in line, is read frequently and the needed corrective action of – adjusting the opening of the needle valve attached to the gas cylinder
Results and discussion
The experimental liquid phase composition (x1) versus temperature (T) data, summarized in
Table 2, are fitted to the Wilson [5] equation:wherewhere and are the liquid molar volumes of the pure components and λ ‘s are the energies of interaction between the molecules designated by the subscripts. It is assumed that the interaction energies λ12 and λ21
Conclusion
Phase equilibria in the binary mixtures of N,N-dimethyl formamide with: acetophenone, aniline, bromobenzene, chlorobenzene and N,N-dimethyl acetamide have been investigated. The observed values of the liquid phase mole fraction versus bubble point on all the mixtures investigated could be well represented by the Wilson model. Among the mixtures investigated, the mixtures with bromobenzene, chlorobenzene and N,N-dimethyl acetamide show positive values for excess Gibbs energy while the mixtures
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