Industrial Chemistry
Open Access

Abstract

In this study, a facile and environmentally friendly method was reported for manufacturing of natural acid-base indicator by preparing Allium cepa L. juice, which provided the anthocyanins pigment. The anthocyanins pigment was extracted via boiling process. In detailed, the Allium cepa L. was cut into small fragments. Then the small fragments of Allium cepa L. was boiled in distilled water in order to extract the anthocyanin pigment. This process was followed by the addition of different solutions of acidic solutions; base solution as well as neutral solution was added into separate test tubes filled with extraction of Allium cepa L. juice. The obtained Allium cepa L. juice was then used as the pigment for the acid-base indicator. The pH of the solution can be determined by observing the color change in the Allium cepa L. juice. The light purple color of the Allium cepa L. juice turned into red color when added with hydrochloric acid, its purplish color of the juice turned into yellow when added with sodium hydroxide, the original color of Allium cepa L. did not undergo any observable color change when distilled water is added into it. The Allium cepa L. exhibited excellent color change property with chemical solutions. These color changes make the Allium cepa L. be attractive for applications in acid-base indicators.

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