Organic solvents with densities greater than and less than that of the aqueous solution are used to extract the iodine.
The aqueous solution of food color is blue. Iodine in water is yellow, and when added to the food color the result is a green solution. When this aqueous solution is extracted with organic solvents (hexane and dichloromethane), the iodine is drawn into the organic layer, leaving a blue aqueous layer and turning the organic layer purple. The hexane layer (d=0.66g/mL) will float on top of the aqueous, while the dichloromethane (d=1.33g/mL) will settle beneath the aqueous.
To Conduct Demonstration:
Take care not to get solutions on skin. Gloves are suggested, but will not keep out dichloromethane. Release pressure often during extractions.