Chemical Education Today
Editorial: Using a Living Textbook Effectively An early editor of this Journal characterized it as a living textbook of chemistry. Presumably this was intended to mean that, like a textbook, the Journal contains a wealth of information that has been carefully checked for accuracy. A living textbook, like a living organism, grows and matures, constantly updating and modernizing the information it contains. The Journal’s role as a living textbook was brought home to me most emphatically as the editorial staff prepared this issue, because that is exactly how we used it. At the JCE booth at the recent ChemEd ’97 meeting in Minneapolis we handed out lots of copies of the first JCE Classroom Activity sheet (see last month’s issue) together with small refrigerator magnets that could be used to carry out the activity. Reaction of the teachers at the meeting was so positive, and so many said they would like an activity sheet in every issue, that we changed our plans and decided to do one for this issue as well. But what to do? And how to do it? The modern incarnation of the living textbook of chemistry came to the rescue. Since we had a paper by Dana Barry (page 1175) about chemistry and trees, and since it is fall, we thought that the color of fall foliage would make a good activity. Knowing that anthocyanins are responsible for many of the fall colors, we immediately thought of red cabbage as an acidbase indicator, but decided that many, if not most, readers would already be aware of the many chemistry activities based on red cabbage (1). At this point we turned to JCE Online and the Journal’s online index. In a few seconds a search was done to find all titles that contained “pigment”. There were 28. Another search was done for titles that contained both “acid-base” and “indicator” (9 hits), and another for titles that contained “anthocyanin” (2 hits, both very recent and one with its abstract online). I certainly commend this index to you. It is available free via JCE Online (http://jchemed.chem.wisc.edu/). Follow the links to Journal and JCE Index. In less than 10 minutes I had found more than a dozen directly applicable references and more than a half dozen more that were relevant, but, because of potential hazards, not useful for a hands-on investigation that could be used as a take-home activity. Kudos and thanks are due Paul Schatz and Jon Holmes for making this excellent resource available via the web 24 hours a day, seven days a week. Every author, or potential author, of a Journal paper should consult the index before starting to write. My search gave me all the information I needed. I discovered that in the twenties Ernest H. Huntress of MIT had published three papers on the chemistry of red and blue pigments of flowers and plants (2). From these papers I learned that Willstätter’s Nobel Prize was largely due to his work with plant pigments and that the mass percent of anthocyanins in flower petals varies from about 2% in purple delphinium to as much as 33% in dark blueblack pansies. The Journal revisited this subject in a Report of the New England Association of Chemistry
Teachers in 1946 that also dealt with other leaf pigments, chlorophylls and carotenoids. In 1949 a paper on plant pigments and photosynthesis immediately preceded one by Melvin Calvin on photosynthesis. Another review of pigment chemistry appeared in 1982, and there have been seven papers on different chromatographic separations of plant pigments. (You’ll have to use JCE Index to find these, as I haven’t space to list everything I found.) Because chlorophylls and carotenoids are not water soluble, their separation requires flammable solvents, and for a take-home activity we turned to other sources. An excellent review on indicators by Szabadváry (3) had an interesting section on natural indicators, and a paper by Forster (4) provides lots of good ideas for using red-cabbage indicator, some of which we applied to flower-pigment indicators. In 1985 Mebane and Rybolt wrote on “Edible AcidBase Indicators” (5), listing pH–color behavior of 14 fruit and vegetable extracts. Finally, a collaboration of high school and college teachers has recently provided excellent information on anthocyanins (6). These papers formed the basis for developing this month’s JCE Classroom Activity sheet (pages 1176 A and B). JCE Index even provided ideas for expansion of the activity. Kimbrough (7) has described a column chromatographic separation of leaf pigments that requires only household chemicals (albeit mineral spirits is used), and Mewaldt, Rodolph, and Sady (8) have devised an inexpensive and quick chromatographic separation. Combining these two could lead to another more advanced activity using fall leaves. I was personally fascinated by what I found in this Journal on the subject of plant pigments, and I think any teacher would be. The willingness of chemistry teachers to share their ideas and information, the good judgment of previous editors who published their work, and Schatz and Holmes’s JCE Index, which makes it possible to find all these papers in a very short time, combine to make this Journal a unique resource. At 74 years of age this Journal is full of wisdom, but also growing and maturing. It is definitely a living textbook of chemistry.
Literature Cited 1. Shakhashiri, B. Z., Chemical Demonstrations: A Handbook for Teachers of Chemistry, Vol. 3; University of Wisconsin: Madison 1989; pp 50–57; Sarquis, A. M.; Sarquis, J. L., Fun With Chemistry, Vol. 1; Institute for Chemical Education: University of Wisconsin–Madison; 1991, pp 53–61. 2. Huntress, Ernest H. J. Chem. Educ. 1928, 5, 1392, 1615; Huntress, E. H. J. Chem. Educ. 1929, 6, 52. 3. Szabadváry, F., translated by Oesper, R. E. J. Chem. Educ. 1964, 41, 285. 4. Forster, M. J. Chem. Educ. 1978, 55, 107. 5. Mebance, R. C.; Rybolt, T. R. J. Chem. Educ. 1985, 62, 285. 6. Curtright, R. D.; Rynearson, J. A.; Markwell, J. J. Chem. Educ. 1994, 71, 682; Curtright, R.; Rynearson, J. A.; Markwell, J. J. Chem. Educ. 1996, 73, 306. 7. Kimbrough, D. R. J. Chem. Educ. 1992, 693, 987. 8. Mewaldt, W.; Rodolph, D.; Sady, M. J. Chem. Educ. 1985, 530, 987.
Vol. 74 No. 10 October 1997 • Journal of Chemical Education
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