phenolphthalein noun.
[fi:nɒl'(f)Ɵali:n, -'(f)Ɵeɪl-] L19.[from PHENOL + PHTHALIC + -EIN.]A whitish or yellowish crystalline solid, C
20H
14O
4, which is used as an indicator in the pH range 8 (colourless) to 10 (red), and medicinally as a laxative.
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