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  Home > JCE Print > Journal of Chemical Education > Issues > 1995  > December  >
General Interest
Preparing "Chameleon Balls" from Natural Plants: Simple Handmade pH Indicator and Teaching Material for Chemical Equilibrium
Naoki Kanda, Takayuki Asano, Toshiyuki Itoh, and Makoto Onoda
Department of Chemistry, Faculty of Education, Okayama University 700, Japan
Cover
December 1995
Vol. 72 No. 12
p. 1131
Abstract
Anthocyanins are found in the flowers and fruits of natural plants. Since their color depends on pH, they are sometines used as a pH indicator. Since these sequences are reversible, they are also useful in demonstrating chemical equilibrium in the repetitive color changes of anthocyanins from flowers by controlling pH conditions. We prepared the polysaccharide beads conatining water extracts of red cabbage as calcium alginate. The beads showed a clear red color under acidic conditions, turned blue at neutral pH of 7, and orange-yellow at pH of 13. This color change could be demonstrated over and over. Because the color changes of these polysaccharide beads depended darmatically on pH, junior high students in science classes called them "chameleon balls" when we demonstrated this reaction for them. In this paper we describe how polysaccharide beads, which are made from calcium alginate with natural pigments, served as a teaching tool for the chemical equilibrium of anthocyanins under different pH conditions. Preparation of the chameleon ball is very easy. The most important thing is that making the chameleon ball is great fun. The ball should therefore be viewed not only as a handmade pH indicator but also an interesting teaching tool of the chemical equilibrium reaction.
More Information
*  Citation
 Kanda, Naoki; Asano, Takayuki; Itoh, Toshiyuki; Onoda, Makota. J. Chem. Educ. 1995 72 1131.
*  Keywords
*  History
 Created:
Last Updated:		 10/1/1999
5/22/2006
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