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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 11 Issue 2 (2006) pp 98-101

An Electrochemically Induced, Chemically Produced, and Mechanically Cycled Traffic-Light Effect

Salvador Santoyo-Cázares,Jorge G. Ibanez,†,‡,* Lydia Hernández-Rivera, Martín Adolfo García-Sánchez,

Dept. Procesos Tecnologicos e Industriales. Instituto Tecnologico y de Estudios Superiores de Occidente (ITESO), Periferico Sur Manuel Gomez Morin # 8585, Guadalajara, Jal. 45090, Mexico and  Centro Mexicano de Quimica en Microescala, Depto. de ICQ, Universidad Iberoamericana, Prolongacion Reforma 880, 01210 Mexico, D.F.,
Received September 28, 2005. Accepted December 8, 2005.

Published online: 7 March 2006

Abstract. A five-minute experiment that couples electrocoagulation with local electrochemically induced pH changes produces a red-to-green-to-red-to-green color change (i.e., a traffic-light effect). The readily available pH indicators methyl red and bromocresol green give such an effect.

Key Words: Laboratories and Demonstrations; general chemistry; physical chemistry; analytic chemistry

(*) Corresponding author. (E-mail:

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Issue date: April 1, 2006

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