The application of red-cabbage extract as an acid-base Indicator in various forms in high school chemistry

Document Type : Original research

Author

Chemistry Laboratory, Science Laboratories, Shahid Beheshti High School, District 1, Department of Lorestan Education, Iran

Abstract

Red-cabbage extract (RCE) with its purple color in neutral environment, contains anthocyanin compounds and can act as an acid-base indicator. In this study, red cabbage extract in the form of liquid extract, dried cabbage powder, as well as paper, cotton, and sponge soaked in the extract were used as acid-base indicators. Then, the characteristics of the prepared materials were compared with each other. Compared to paper, cotton was more easily impregnated by RCE and quickly wetted in acidic/alkaline solutions. The sponge was easily impregnated by RCE, but didn’t show a high clarity of color-changes as a pH-identifier, because it cannot absorb much RCE due to its hydrophobicity. RCE can also be used directly as a pH-identifier and shows good color-changes in various acidities. Nevertheless, it was found that the use of dried red-cabbage powder as a pH indicator is more appropriate than the other pH indicators. This superiority of dried red-cabbage powder probably results from it's simple and easy production as well as its clear color-change in acidic and basic solutions. Additionally, this research could have positive effects on introducing the notions of acid, base, pH indicator, and bio-materials, it has also led to the creation of some experiments, which can be used in high-school labs for the purpose of practical teaching.

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