Colorful Chemistry Demonstrations Using Plant Dyes and Natural Solvents

Abstract

This study identified some common plants whose colored parts may be extracted and used as alternatives to commercial indicators in acid-base titration demonstrations.  Conventional procedures had long used synthetic indicators which are considered hazardous and can be difficult to source. Six samples were derived from three common plants cultivated in many parts of the world: alugbati (Basella alba), camote (Ipomoea batatas), and ube (Diescorea alata L.).  Without the use of hazardous solvents such as alcohol, these samples were extracted by boiling them in plain water.  The extracts were then qualified for indicator use by observing color changes in a strong acid-strong base titration. The results from one-sample t-tests showed that four out of the six natural samples tested closely mimic the behavior of the indicator phenolphthalein, thereby providing the potential to replace this popular synthetic indicator in school chemistry demonstrations. This safe and inexpensive way to do colorful titrations without the synthetic chemical may be replicated anywhere where these plants grow, and opportunities exist for further testing using other dyed plants.  The simplicity of the preparation provides for a more appealing approach in teaching some difficult concepts in Chemistry.