Phenol phthalein

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Related to Phenol phthalein: methyl orange
See under Phthalein.
a white or yellowish white crystalline substance made from phthalic acid and phenol. Its solution in alkalies is brilliant red, but is decolorized by acids, and as this reaction is exceedingly delicate it is used as an indicator.

See also: Phenol, Phthalein

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.