Chemical Education Today
Report: My Favorite Element
I(nto) My Element by Richard W. Ramette
photo: R W. Ramette
Figure 2. My favorite element, displayed as a license plate.
substances are the sparkling deep green crystals of tetramethyl ammonium pentaiodide (90% I!). While on leave at Oak Ridge National Laboratory, my research with Donald Palmer on high temperature equilibria of iodine was the best work I ever did. An entrancing crystallization is the snowfall-like formation of glistening golden hexagons of lead iodide, as a hot solution cools in the light of a sunbeam. A spectacular flare is set off by adding a few drops of water to a mixture of aluminum and iodine powders (3). For years my vanity license plate, IODINE, elicited questions from the curious. Now, in Arizona, I monitor desert heat with my “iodine thermometer” (4), a 12-L flask containing solid iodine that uncomplainingly sublimes to deep purple vapor during hot days and reverts back to lustrous crystals at night. These are some of the reasons for choosing iodine as my favorite element. Literature Cited 1. Partington, J. R. A Textbook of Inorganic Chemistry; Macmillan: New York, 1939. 2. Ramette, R. W. Benzene Extraction of Antimony Iodide. Anal. Chem. 1958, 30, 1158–1159. 3. There are some great videos of aluminum reacting with iodine. See an example from JCE Software at http://www.jce.divched.org/ jcesoft/cca/cca1/R1MAIN/CD1R1260.HTM (accessed Jul 2009) or Google aluminum iodine reaction. 4. See Ramette, R. W. Colorful Iodine. J. Chem. Educ. 2003, 80, 878 as well as the cover of the August 2003 issue that shows the iodine thermometer at midday at my home in Arizona.
Supporting JCE Online Material
http://www.jce.divched.org/Journal/Issues/2009/Oct/abs1136.html Abstract and keywords Full text (PDF) with links to cited URLs and JCE articles
Figure 1. An iodine thermometer showing small iodine crystals that were deposited on the inner surface of the flask by repeated solar vapor–solid transitions. See ref 4 and the cover of the August 2003 issue of JCE.
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photo: R W. Ramette
Long ago, in the first years of my teaching at Carleton College, I began a clock reaction demonstration by saying, “You’ll like this. It’s about iodine, my favorite element.” At the end of the term my questionnaire included, “What did you like about this course?” To my surprise, one student wrote, “I liked that you have a favorite element. I asked my geology professor what his favorite mineral was, and I was disappointed when he had none.” I’ve found much to like about iodine (Greek, Iodes, violet). It was discovered in 1811 as purple-black crystals that came out of burning seaweed. Its tincture kills germs, and nowadays it’s swabbed liberally around my eye when I get injections for macular degeneration. When a brown water solution of iodine is shaken with colorless CCl4, the water becomes colorless and the CCl4 turns purple. That’s a perfect demonstration to show solvent extraction and to discuss molecular polarities. As a boy chemist in high school my happiest moments were “feather-catalyzed” explosions of nitrogen triiodide, releasing glorious purple plumes with a satisfying CRACK! I learned to make it from my favorite book, Partington’s Inorganic Chemistry (1). This skill almost got me expelled from Wesleyan University’s freshman chem lab. An early Dick Tracy strip had a bad guy escape using a “gun” carved from a potato and turned black by iodine solution that he had coaxed from a guard to treat a self-inflicted cut. (Think, “starch indicator”.) My college students assayed vitamin C tablets by potassium triiodide titration. They determined the tiny amount of KI in “iodized” salt, first oxidizing iodide to iodate with bromine, and then using the Dushman reaction to make a titratable quantity of I2. One of my earliest publications was Benzene Extraction of Antimony Iodide (2), a compound with beautiful orange crystals. In my display collection of favorite
Richard W. Ramette is L. M. Gould Professor of Chemistry, Emeritus, Carleton College Northfield, MN;
[email protected].
Journal of Chemical Education • Vol. 86 No. 10 October 2009 • www.JCE.DivCHED.org • © Division of Chemical Education
