Abstract: Vapor-liquid equilibrium data on benzene-ethyl alcohol binary system at 760 mmHg were secured from modified Rose equilibrium still. It was found out that the data obtained accorded with the themodynamic consistency. Then pure α -pinene and limonene were prepared at the pressure of 50mmHg by a high efficiency fractionating column.Using this modified Rose equilibrium still, vapor-liquid equilibrium data on α= pinene - limonene binary system at 111 mmHg were also collected which showed that this binary system is a perfect system which follows Raoult’s law.