action does not quite go to wmpletion in the presence of SDS (11,12). This demonstration nicely illustrates the inhibiting effect that a surfactant can have on a chemical reaction. Finally, it should be mentioned that the 2.5 x 10-3 M SDS concentration used in this demonstration is well above the critical micelle concentration of SDS in aqueous solutions of high ionic strength (13). Literature Cited Rujimefhabhas, M.: Wi1airat.P J. C k m . Educ. 1818,66,342. Ablun. E. B.; Lissi,E.A. J. Chom. Educ. 19% 69,340. Corsam,G.J C h e m E d u c 1973,50,575. C o r m , G.:Smith,J. K . J. Cham. Educ. 1976,53,589. Corsam, G. J Chem Educ 1980.57.226. RevlsbomughV. C.;Rabinsrm,B.H. J Chem.Edue 1981,68,586. 7 Rncssler N. .l Chem Educ 1919.56675,
1. 2. 3. 4. 5. 6.
11. Duynstee, E. F. J.; h w a l d , E. J Amer Cham. Soc 1959,81,4540. 12. Baumrucker. J.: Cshsdills. M.: Corder. E. H . Rawtion Kinetics in M i e l k : Cordea, E. H., Ed.: ~le"um:New~ork,1972; pp 2&51. M.L.;Hankins, W. D. J. Amer C h . Sor 1947,69,683. 13. Co-,
Kinetic Art through Chemistry Walter H. Corkern, L. H. Holmes, Jr., and N. A. Higginbotham Southeastern Louisiana University Hammond, LA 70402
People who are not interested in chemistry oRen have the misconception that it is hard, boring, and dull. We have found a number of demonstrations that show it also can be beautiful and fascinating. The demonstrations are observed easily by large groups using a n overhead projector or a video camera. A Demonstration That Pleases The demonstration that offers greatest aesthetic pleasure uses a solution of 60% ethanol40% water (by volume) as solvent. APetri dish is placed on a n overhead projector and half filled with the solvent. One drop of l-heptanol with a small amount of dissolved crystal violet dye is dropped onto the solvent in the Petri dish. The rapid motion that occurs forms patterns similar to fractals. After
Presented in part at the 65th Annual Meeting of the Louisiana Academy of Sciences, Feb. 8,1991.
the drop of heptanol has dissolved, geometric patterns continue to form over the next minute or so. If one prefers the color red, l-heptanol with a small amount of 0ii Red EGN dye (Matheson Coleman & Bell) can be used for similar effects. Several drops of the l-heptanol-dye mixture added in rapid succession to the solvent also yields pleasant results. If one uses 40% ethanol40% water (bv volume) as solvent, one can observe the stirring action-that takes place as l-he~tanol(containing Oil Red EGN) dissolves. A shallow layer of the solveni about 3-4 mm deep should be added to the Petri dish. You may have to try this one several times to be able to judge the depth of solvent needed. To the solvent add a small amount of acid-washed, 80190 mesh Chromport A (a small amount on the tip of a spatula, containing 40-80 particles, works well). Then add a drop of the l-heptanol-dye mixture to the surface of the solvent above the Chromport A particles. The particles are moved around bv the currents in the solvent. ao~arentlvcaused by the siution process. As the drop ;ea& ampfete solution, the stirring streams have sometimes been observed to become directed in space (5 equally spaced streams of the oarticles a ~ ~ e a r i star n e shaped). Then.." iust . orior to complete solution, the five streams tend to become four equally spaced streams (in the shape of a cross or plus). Using a solvent of 30% ethanol-70% water by volume and several samples of l-heptanol, each containing a different dye (oil red, crystal violet, basic fuchsin, malachite green, sudan 111, etc.), moving art can be produced. Fill the Petri dish half full of solvent, and add as many drops of each l-heptanol-dye mixture as you wish. The drops move around slowly with currents that can be observed. The drops tend to remain separated, however, and they form circles or lines of drops. A.
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Demonstrationsthat Titillate Young and Older, Alike The demonstrations described above have been shown to elementary, junior high, and college students, to wllege teachers, and to senior citizen groups. Every group responded with excitement and numerous questions, especiallv the elementarv and iunior high students. A ;ideotape of these demonstra
