The authors have designed an equilibrium still with dual circulation of vapor and liquid phases and tested the still with water-acetic acid binary

system. The obtained data were compared with available data in literature and the results are found satisfactory. With the said still

vapor-liquid equilibrium data were measured for three binary systems i. e

methyl iodide-methyl acetate

methyl iodide-methanol

methyl iodide-acetic acid at 760mm Hg pressure. The first two binary systems exibit a minimum azeotrope and the third has no azeotropic behavior. Data were correlated through Wilson

NRTL and WFH equations. Optimum parameters were evaluated by means of damping and nonlinear least square method.