The demonstration, which combines an irreversible sugar dehydration reaction with an irreversible oxidation reaction, can be effectively and safely performed in a 3 in. clay flowerpot partially filled with sand and suspended from a ring-stand with a 3 in. iron ring. Filter paper placed over the drainage hole of the clay flowerpot prevents sand from leaking out. A large collection vessel, such as an iron pail or porcelain dish, set immediately below the flowerpot provides an extra measure of safety and collects any reaction products that leave the flowerpot.

Further, we found that burning ethanol- or isopropanol-soaked sugar in the absence of KClO₃ leads to a carbonaceous product similar to that reported in ref 1 as “small black upwellings of carbon” and “that smells for the most part like burnt sugar” and discussed in ref 2. This modification demonstrates sugar dehydration without the use of KClO₃. Therefore, disposal of any unreacted and unstable sugar–KClO₃ mixture (1) is no longer a problem.

With our flowerpot demonstration setup, it was easy and safe to perform and contain the traditional, colorful, and highly exothermic sugar oxidation by KClO₃ demonstration (3). Because of the large volume of hot gases released as well as the observation that KClO₃ oxidation of sugar in the presence of sulfuric acid may yield toxic and reactive gases Cl₂, ClO, and ClO₂ (1, 3), we recommend performing this demonstration in a fume hood. To well mixed stoichiometric amounts of sugar (~1 g) and KClO₃ (~3 g), we instantaneously (~1 s) initiated the reaction with a drop (~0.05 mL) of concentrated sulfuric acid. An alternative procedure, using a match to ignite an ethanol saturated reaction mixture, gives a one- to two-minute delay before initiating the highly exothermic sugar oxidation reaction.

Literature Cited

1. Silverstein, T. P.; Zhang, Y. J. Chem. Educ. 1998, 75, 748.
2. Dahn, J. R.; Zheng, T.; Liu, Y.; Xue, J. S. Science 1995, 270, 590–593.
3. Shakhashiri, B. Z. Chemical Demonstrations, A Handbook for Teachers of Chemistry; University of Wisconsin Press; Madison, WI, 1983; Vol. 1, pp 79–80.

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