phenolphthalein

A white or pale yellow crystalline powder, C₂₀H₁₄O₄, used as an acid-base indicator, in making dyes, and formerly in medicine as an over-the-counter laxative.

A white crystalline compound, C₂₀H₁₄O₄, made by heating a mixture of phthalic anhydrid and phenol with a dehydrating agent, as stannic chlorid or sulphuric acid. The dilute alcoholic solution is much used as an indicator in titrating. It can he used with weak or strong acids and strong bases. It melts at 250–253° C.

A white or yellowish white crystalline substance, C20H14O4, formed by condensation of the anhydride of phthalic acid and phenol. Its solution in alkalies is brilliant red, but is decolorized by acids. This reaction, being very delicate, is used as an indicator. It is sometimes used as a laxative in veterinary medicine.

A quinone derivative used as a pH indicator, and once used as a laxative

a laxative used in many preparations under various trade names; also used as an acid-base indicator in titrations involving weak acids and strong bases because it is brilliant red at high alkalinity and colorless below pH 8