1. INTRODUCTIONSeparating two components in a liquid solution through distillation depends on the distribution of these components between a vapor phase and a liquid phase. The driving force for this kind of separation is the relative volatilities of the two components in the liquid solution (Geankoplis, 2003). Distillation is one of the most widely used separation process used in various industries. (Coulson & Richardson, 1996).Phase creation is the underlying mechanism of the separation through distillation. During the distillation, the components are distributed between vapor phase and a liquid phase where the vapor phase is created from the liquid phase by vaporization at the boiling point [Geankoplis, 2003]. It takes advantage of the differences in volatility between the components of a liquid mixture. The more volatile component is progressively transferred to the vapor phase and the less volatile condenses out in the liquid resulting to an increase in concentration of the more volatile component in the vapor and a decrease in concentration of the less volatile component in the liquid or the bottoms (Foust et al., 1980).There many ways distillation can be done. It can be done in batch or continuous process, and either with or without reflux involved. The distillation process in this experiment is operate in batch with rectification. In this experiment, the feed is boiled sloly and th vapors are withdrawn as rapidly as they are form to a condenser, where the condensed vapor or distillate is collected (Geankoplis, 2003). The composition in the still pot and vapor changes continuously with time. The first portion of distillate will be richest in the more volatile component and it would become leaner in the volatile component as time progresses (along is the decrease in the composition of the component in the still pot). Figure 1 shows a simple still of a batch distillation column. Figure 1. Simple Batch or Differential Distillation

Rayleigh equation is used in a batch distillation calculations, which is derived from the material balance on A for a binary mixture of A and B. Originally, a charge of L1 moles of components A and B with a composition of x1 mole fraction of A is placed in the still. At any given time, there are L2 moles of liquid left in the still with composition x2, and the composition of the vapor leaving in equilibrium is y where it is assumed that dL is the small amount that is vaporized.Upon relating the total moles of feed at the beginning and at the end, the equation (1) (Rayleigh equation) is obtained from the material balance over the component in a batch Equation 1

The integration of equation (1) can be done graphically by plotting against x or by calculating values of numerically. The total area under the curve is calculated from x1 to x2 and consequently the L2 moles of liquid left in the still is obtained. Figure 2. Graphical Integration

The average composition of the total distillate, yAV, can be obtained through material balance as shown in equation (2).Equation 2

In the experiment, the process involves the use of reflux. Since batch distillation does not give good separation unless the relative volatility is very high, a rectifying column with reflux is used in many cases to improve the performance of the batch still [McCabe et al., 1993]. Constant reflux ratio is used since varying the reflux ratio is difficult to perform and impractical. Reflux ratio (R) is defined as the ratio of the quantity of liquid returned per (LR) unit quantity of product removed from the process unit (D) as given in equation (3) below.Equation 3