Immiscible solvents distillations traps

During operation, the apparatus shown in Fig. 2 requires attention beyond occasional draining of the water trap. It is suitable for a number of preparations in which water is removed by distillation with an immiscible solvent it functions only when the condensate separates into two phases, of which water is the more dense. 

This method, specimens and water are heated in a steam distillation apparatus, once the water is boiled, volatile constituents will be carried along with the water vapour and then condensed in to a trap containing water and an immiscible solvent. Water and the solvent will separate into two phases. The volatile oils is dissolved in the solvent. A standard method described in British Pharmacopoeia (BP) 2010, Essential oil in Herbal Drugs, is very useful in determining the total content of volatile oils in herbs. The volatile distillate thus obtained can be used for determination of the constituents either qualitatively or quantitatively. 

The sample is heated under reflux conditions with a water immiscible solvent which co-distills with the water in the sample. Condensed solvent and water are continuously separated in a trap—the water settles in the graduated section of the trap, and the solvent returns to the distillation flask. 

The technique involves placing the sample in a flask and then adding benzene, toluene, or some other low-boiling solvent that is immiscible with water. Heat is applied, and the solvent and the water in the sample both distill. The material is collected in a Dean-Stark, Bidwell-Stirling, or Barrett trap, or some modification of them. The water settles to the bottom, and the solvent drains back into the sample flask to be reused. The water can be drained off and its amount measured. The traces of solvent can be evaporated from the sample, and the dry sample is ready for further analyses. This is a separation method for large amounts of water and is particularly useful for food samples that would be quite large unless the water is removed. 

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