Liquid-Liquid Equilibria in Partially- Miscible Systems: Nicotine-water - QS Study
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Liquid-Liquid Equilibria in Partially- Miscible Systems: Nicotine-water

There are pairs of substances which are liquids at ordinary temperatures or whose melting points are low or are known to have limited mutual solubility within certain temperature limits. They are said to be partly miscible in the temperature limits and their solubility curves form an interesting aspect of the application of the phase rule. These substances become completely miscible beyond the temperature limits. These limits are sometimes attained on raising the temperature or sometimes on lowering the temperature. In some systems there are two limits, one higher and the other lower. In this section an attempt will be made to discuss Nicotine-water systems.

Nicotine-water: The system nicotine-water gives an interesting phase diagram which is a completely closed curve as can be seen in Figure. There are two critical solution temperatures one at 2080C and the other at 610C. Within these temperature and concentration ranges shown in the figure partial miscibility persists and there are two liquid phases shown as L1 and L2. Outside these ranges complete miscibility results. This curve looks like the combination of Figures which represent phenol-water and triethylamine-water respectively. Several other pairs are known to behave like nicotine-water.

Figure: diagram of water- nicotine

In several cases the consolute temperature cannot be attained. This happens due to disappearance of one of the phases as vapour above the critical temperature or as solid below the freezing point. Theoretically their consolute temperatures lie either above the critical temperature or shell below the freezing point of one of the components. Water-chloroform is an example of the first type because before the CST is attained the critical temperature of chloroform is reached Water and ether is an example of the second type. Water freezes to ice before the lower consolute temperature can be attained.