One mercury-filled open ended manometer with quick disconnect on hose
Filter flask (500 mL) with rubber stopper configured with rubber septa (see figure) and quick disconnect
Several 35 mL plastic hypodermic syringes with needles
Several 100 mL beakers
100 mL samples of carbon tetrachloride and water

Figure. Apparatus for Demonstrating Solution Vapor Pressure

This demonstration should accompany lectures on solutions and solution vapor pressures. It provides a good contrast to the experiment with a homogeneous solution (Demo-016). When two liquids are not mutually soluble (immiscible), the vapor pressure of the mixture is the sum of the vapor pressures of the components.

Begin by setting up one vapor pressure apparatus and injecting it with 10-15 mL of carbon tetrachloride. Point out to the class that this solvent does not dissolve water, the two liquids form separate layers when mixed. Ask what they think might happen to the vapor pressure in this case. When water is injected into the vessel containing carbon tetrachloride, will the pressure go up or go down? Discuss the reasons for the possible results. When water is injected into the vessel, the total pressure registered by the manometer will increase.

When two liquids are not miscible, the vapor pressure of the mixture (not a solution) is equal to the sum of the vapor pressures of the components. There is no weighting for mole fraction or concentration, just the simple sum. You may remember the separation of organic substances by the process of steam distillation, which operates on this principle.

Don't stab yourself with the hypodermic needles! Do not dispose of carbon tetrachloride by pouring down the drain! It is not soluble in water and will not disappear by dilution.