/fee'nawl sul'fohn thal"een, -ee in, -fthal"-, -nol-/ , n. Chem.
a bright to dark red crystalline compound, C 19 H 14 O 5 S, slightly soluble in water, alcohol, and acetone: used as an acid-base indicator and as a diagnostic reagent in medicine. Also called phenol red .
[ PHENOL + SULFONE + PHTHALEIN ]