going beyond. going further Exponents Experiments that are reviewed in this section have appeared in a recent issue of THIS JOURNAL. Specific suggestions on how these experiments might be adapted into research projects for students are presented below. Lavallee, D. K., Daugherty, N. A. J. Chem. Educ. 1979,56, 353. An experiment stressing the basic principles and applications of electrophoresis, a widely used separation technique, is discussed. The experiment, which is designed to separate two azo dyes, is both practical and feasible since i t can he carried out in a typical high school chemistry lah using relatively inexpensive materials. In order to adapt the lecture demonstration successfully for student "research" several procedural modifications must be made. (It is advisable to look a t the original article before reading the following recommendations. I t should also be noted that there is an error in the original article. Figure 3 on page 353 should read "Separated indicators after electrophoresis. From LEFT to RIGHT: . . . etc. . . ." (This error was discovered by David Todd of the Worcester Polytechnic Institute, and, upon his contacting Daugherty the error was confirmed.) Instead of using 18-gauge nichrome wire for the electrodes, i t is less expensive and just as effective to use 18-gauge solid copper wire. The copper electodes should be cleaned after every two or three runs, since salts tend to build up on the wire while it is in contact with alkaline buffer solution. With regard to the huffer itself, it is preferable to use asolution of pH 10 rather than pH 11, since it was found that pH 10 buffer can produce a more distinct separation of the dyes. Results may also be improved by increasing the voltage to 200 V and letting the separation run for 30 min rather than the 10 to 15 min specified in the lecture demonstration. Extreme c a r e must be exercised when using voltages of this magnitude. As a final Droceduralnote, standard glass crystallizing dishes should be used instead of freezer cartons as containers for the buffer solution. Several optional projects may be pursued. One suggestion is to make a time lapse video recording of the actual separation. Such documentation may prove very valuable during a presentation on the theory and mechanics of electrophoresis. Another possible project is t o investigate how electrophoresis is used in the medical field asan effective diagnostic tool for heart disease and other illnesses?
edited by N. H. ETTINGER
George Washinan High Schwl Bustleton Ave. and Verree Road Philadelphia. PA 19116
tropy) may be elucidated. A spectrophotometer (290 nm) and a good water bath are needed. Other compounds that may lend themselves to such analysis are also mentioned. Armstrong, Daniel W.; Khanh, H. Bui; Barry, Regina M. J. Chem. Educ. 1984,61,457. The article illustrates the use of TLC without noxious, carcinogenic compounds. Micelles are formed by using a cationic or anionic surfacant. While the authors state that the separation of such compounds as those found in plants do not lend themselves readily t o such separation, I feel that PLC (pseudophase TLC) should be explored-the benefits possibly far outweighing the difficulties. Spears, L. Gene, Jr.; Spears, Larry G. J. Chem. Educ. 1984, 61,252. A technique for possible storage of solar energy using an endothermic complexing reaction is discussed. The explanation is vivid and easily followed. The suggestion that other hydrated salt systems in anhydrous solvents could be examined is well taken. A spectrophotometer is needed (visihle range). Ozog, J. Z.; Morrison, J. A. J. Chem. Educ. 1983,60,72. An understanding of mole fractions and how they apply to activity coefficients from an experimental view is depicted. The apparatus is somewhat crude, but suggestions are offered to modify and upgrade the hardware. Systems and concepts for further study may include 1) ApplicationstoRaoult's Law and Henry's Law via the presented experimental procedure and from the data graphs offered. 2) AG values which may also be calculated. 3) Some other systems-both electrolyte and noneleetrolytecould be tested. 4) Mathematical correlations that may exist among the various graphical presentations could be determined. 5) Determining if the solutions must be azeotropic to yield successful results. Note: Care must be exercised when handlingcarbon tetrachloride because of itssuspecled carcinogenic properties. Roth contract and inhalation must be avoided. 6) Evaluation of AGE, fl, and ASE from temperature dependance of 7. 71 1)ererminatiunof AII%f mixing ( = AllM)via the variation of acri\,itycwfficirnrs with temperature studies. Thia gives All" from the plot
John Paul Rieck
Vineland High Schwl Vineland, NJ Adams, K. R.; Meyers, M. B. J. Chem. Educ. 1985,62, p 86. The authors make a point that, in the determination of activation energies with enzyme-catalyzed and acid-catalyzed hvdrolvsis . . reactions using a modification of the Arrhenius equation, with a little h i t h e r work the parameters of thermodynamics (i.e., Cibb's free energy enrhalpy and en-
or from
' Daugherty, N. A. J. Chem. Educ. 1979, 56,442. Volume 63
Number 7
July 1986
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