Vapour Liquid Equilibrium

1) Prepare a calibration chart of composition vs refractive index (R.I) or density, for the two pure components A and B and their mixtures with X_A varying from 0 to 1. Prepare the mixture of various compositions and determine the R.I. or density.

2) Prepare about 200 ml of mixture of A and B. The experiment should be started with the mixture richer in more volatile component (say 160 ml of A and 40 ml of B) so that in subsequent readings temperature increases. This mixture should be filled in the still through either of the limbs.

3) Check carefully that the electrical coil is completely submerged in the liquid ( to avoid ignition) and the mixture is more than 2/3 rd level in the vaporizer. Switch on the power and slowly increase the power input in slow steps. Heating should be regulated so that there is no entrainment or foaming of the mixture from vaporizer to the flash chamber.

4) The circulation of vapour and liquid will soon get established. Allow the system to approach equilibrium. This will be indicated by constant temperature of the thermometer at least for five minutes.

5) Take the liquid and vapour samples and determine the refractive index (or density). Also record the temperature and from R.I. (or density), determine X_A and Y_A.

6) Drain out about 40ml of mixture from the still and add about 40ml of less volatile component. Repeat steps (1) to (5) and record the composition and temperature readings. Take at least six samples, covering whole range of compositions.