Introduction

The technique of extraction is used to separate an aqueous solution of copper (II) chloride and iodine.  Organic solvents with densities greater than and less than that of the aqueous solution are used to extract the iodine. 

Aqueous solutions of CuCl2 are turquoise.  Iodine in water is yellow, and when added to the copper solution 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 turquoise 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.

Prior to Lecture

  1. Prepare 1M CuCl2 (cupric chloride).  Reserve one quarter of the solution and add a few iodine crystals to the remaining 3/4.  Stir until the solution is green.  Decant from any excess iodine solid. ( 134.44g CuCl2/1L) 
  2.  Prepare small bottles of hexane and dichloromethane
  3. Assemble the following equipment:
        •             a.         lighted test tube rack
        •             b.         four 200mm test tube
        •             c.         two rubber stoppers
        •             d.         two corks
        •             e.         gloves
        •             f.          goggles

To Conduct Demonstration:  

  1.  Pour 1M CuCl2 into one test tube to a depth of 2".
  2. Pour the CuCl2/I2 mixture into three test tubes to depths of 2" each.
  3. To one of the tubes containing the mixture, add two inches of hexane.  Stopper with a cork and shake to mix.
  4. To one of the tubes containing the mixture, add two inches of dichloromethane.  Stopper with a cork and shake to mix.
  5. Place the test tubes in a lighted rack.  Compare the colors and identify the layers.

Safety 

Take care not to get solutions on skin.  Gloves are suggested, but will not keep out dichloromethane.  Release pressure often during extractions.