Some oil is extracted from orange peel by dry ice.
name: Supercritical extraction with CO2 is applied to plant material.
Wear eye protection goggles. Due to the high pressure generated during the course of this experiment, there is some risk of vessel rupture. The recommended vessels should be used.
Always follow general safety
recommendations. Please note that conducting chemistry
experiments you must comply with the relevant legal procedures in
Limonene is a component of orange essential oil. The experiment under consideration shows a way to extract it from orange peel using dry ice. Liquid CO2 plays the role of a “green” solvent. As a rule organic solvents or high temperatures are used to separate natural compounds from the plant material. From this point of view liquid CO2 has a great advantage since it is not flammable, nontoxic and has low environment impact.
What properties of CO2 make it applicable for the extraction? The answer to this question will become clear if we look at the CO2 phase diagram. Unlike other gases relatively low temperatures and pressures can be used to achieve liquid and supercritical state of CO2. The triple point of CO2 where solid, liquid and gas phases coexist in equilibrium is achieved at 5.2 atm. and 56.6 °C. In this region of temperatures and pressures liquid CO2 is formed. With the increase of pressure and temperature we move toward the critical point of CO2 (73.8 atm. and 31°C). At this point CO2 adopts properties of both gas and liquid. When we place the test tube with orange peel and dry ice into warm water we move through the triple and critical points of CO2. CO2 behave itself like a gas and readily expands filling all the test-tube volume. The following expansion creates very high pressure. But at the same time the fluid phase in the test tube is dense like a liquid.