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The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 13 Issue 6 (2008) pp 344-347

Green Chemical Experiment: Indigo Dyeing

Nobuyoshi Koga*, A.H.A. Oliveira, and Kazuma Sakamoto

Department of Science Education, Graduate School of Education, Hiroshima University, 1-1-1 Kagamiyama, Higashi-Hiroshima 739-8524, Japan, nkoga@hiroshima-u.ac.jp
Received March 9, 2007. Accepted July 24, 2008.

Published online: 1 December 2008

Abstract. A possible way to improve the experiment of indigo dyeing using green chemistry is examined. In the preparation of the dyestuff solution, the sulfurous reducing agent for reducing water-insoluble indigo into water-soluble leuco-indigo can be replaced with a reducing sugar by slightly increasing the alkalinity of the reactant solution and by using ultrasonic waves to lower the reduction temperature. The dyeing process is also accelerated by the effect of ultrasonic waves. On the basis of the examination of the practical reaction conditions, a green chemical experiment of indigo dyeing is proposed as a student experiment in chemistry courses at secondary schools and colleges.

Key Words: Laboratories and Demonstrations; general chemistry; green chemistry; teaching materials; indigo dyeing; eco-friendly reducing agent; ultrasonic wave

(*) Corresponding author. (E-mail: nkoga@hiroshima-u.ac.jp)

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Issue date: December 1, 2008

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