Question

extration of caffeine.

a.Magnesium sulfate is the drying agent used in this experiment. Why is it necessary to use a drying agent before removing the organic solvent on the rotary evaporator?

b. Adding sodium chloride can often help cause emulsions to breakdown and separate in to distinct layers. Use the principles of solubility to explain why this works.

Answer 1

a. After separation of organic layer from the aqueous layer in the extraction of caffeine, a small quantity of water may remain with the organic layer. So we make use of a drying agent like Magnesium sulphate to absorb the water from the organic layer before evaporating the organic solvent on the rotary evaporator.

b. We know that sodium chloride is an ionic compound and it is soluble in water which is a polar solvent (like dissolves like) and not soluble in organic solvents. So a solution of sodium chloride is able to take out the water from the organic phase thereby causing an emulsion to break down and separate into distinct layers. (Emulsions contain one liquid dispersed in another liquid, these liquids are immiscible with each other).