In the Classroom edited by
Tested Demonstrations
Ed Vitz Kutztown University Kutztown, PA 19530
Solvent Extraction Using Safe and Commonly Available Materials To Demonstrate the Difference in Solubility of Two Mixed Solutes submitted by:
Dante Gilbert L. De Leon and Armando M. Guidote, Jr.* Department of Chemistry, Ateneo de Manila University, Loyola Heights, Quezon City, Philippines 1108; *
[email protected] checked by:
Kimberly L. Kostka Department of Chemistry, University of Wisconsin–Rock County, Janesville, WI 53546 Fred Juergens Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706 Ed Vitz Department of Chemistry, Kutztown University, Kutztown, PA 19530
There exists a growing concern over safety in the chemical laboratory. Many situations in the chemistry laboratory are potentially harmful and may be sources of difficulty for teachers as well as for school administrators. There are several aspects of laboratory safety that should be addressed. These are facilities, equipment, laboratory security, materials safety, protective equipment, and teacher competence (1). Of these, materials safety is increasingly seen as a weak link. Many materials are classified as being corrosive, flammable, toxic, or carcinogenic. Thus, we propose a modification of materials used in a procedure by Love (2). These “new” materials are relatively safer and readily available. Materials Copper(II) sulfate pentahydrate, 4.0 g Sudan III (CAS # 85-86-9), 0.002 g Distilled water, 100 mL 95% Ethanol in water, 100 mL
Kerosene, 30 mL, is added into the test tube containing the purple solution. The characteristic colors of solutions A and B reappear after extraction and shaking, though the colors are less intense due to dilution to twice the volume for both copper(II) sulfate and sudan III. Also, some solid copper sulfate may appear after the extraction. Added Notes The remaining amounts of solutions A and B can be kept for later demonstrations. Vegetable oil, mineral oil, or hexanes may also be used as substitutes for kerosene. The procedure is easily scaled-up depending on the class size. Sudan III is used in coloring oils, spirit lacquers, and as a stain for zoological, pathological, and vegetable objects and is approved by the FDA for external use (3). This activity can thus be used to show the significance of the use of sudan III in biological staining where only lipophilic regions are stained.
Kerosene, vegetable oil, mineral oil, or hexanes, 30 mL
Procedure Solution A is a blue, aqueous solution of copper(II) sulfate and is prepared by dissolving 4.0 g of copper(II) sulfate pentahydrate in 100 mL of water. The red solution, B, is prepared by mixing 0.002 g of sudan III (corresponding to the very tip of a spatula) with 100 mL of 95% ethanol in water. It should be apparent at this point that solution B is saturated, as evidenced by a minuscule amount of nondissolved sudan III at the bottom of the beaker. Solutions A and B, 15 mL of each, are mixed in a 25 × 200-mm test tube resulting in a purple color. Students see that the resulting mixture clearly does not have the characteristic color of either solution A or B. This can be done by juxtaposition of the mixture in the test tube and the remaining amounts of solutions A and B. 436
Hazards Sudan III is an irritant according to the label and thus, for this activity, the use of safety goggles and chemical-resistant gloves, is recommended (4). Literature Cited 1. Richardson, M. D.; Gentry, L. R.; Lane, K. E.; Vanderkum, D. W. J. Chem. Educ. 1994, 71, 689–690. 2. Love, B. J. Chem. Educ. 1994, 71, 517–518. 3. The Merck Index, 12th Ed.; Budavari, S., Ed.; Merck and Co. Inc.: Whitehouse Station, NJ, 1996. 4. Aldrich Chemical Co., Inc., Material Safety Data Sheet. h t t p : / / w w w. s i g m a a l d r i c h . c o m / Te c h n i c a l _ L i b r a r y / Technical_Library_Home.html (accessed Jan 2003).
Journal of Chemical Education • Vol. 80 No. 4 April 2003 • JChemEd.chem.wisc.edu
