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Article

A Qualitative Experiment To Analyze Microbial Activity in Topsoil Using Paper and a Handmade Reflection Photometer

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Masakazu Kita

Faculty of Education, Okayama University, Okayama, Japan

Julius Kofi Agbeko

Teacher Education Division, Accra Teacher Training College, Accra, Ghana

J. Chem. Educ., 2007, 84 (10), p 1689

DOI: 10.1021/ed084p1689

Publication Date (Web): October 1, 2007

Abstract

This article describes a novel, hands-on method to qualitatively determine the extent of microbial activity in topsoil using ordinary blank paper. Appropriate and scalable for the high school and college level, these experiments expose students to some of the challenges facing environmental researchers and also contribute to curriculum development of soil topics for environmental education. Through experimentation, students discover that paper containing high amounts of starch can be used to determine the degree of microbial activity in topsoil. After the application of soil solution eluent to paper, the paper is allowed to dry. Students react the paper with a KI + I₂ solution, and a deep blue coloration results that diminishes over time. Using the principles of complementary color combinations and a simple, handmade, cadmium sulfide–light emitting diode (CdS–LED) reflection photometer, the color can be measured and the extent of microbial activity established.