Phenol phthalein | or ., n. (Chem.) 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 a pH indicator. It is sometimes used as a laxative in veterinary medicine. [ Webster 1913 Suppl. +PJC ] Variants: Phenolphthalein |
Phthalein | n. [ See Phthalic. ] (Chem.) One of a series of artificial organic dyes made as condensation products of the phenols with phthalic acid, and well represented by phenolphthalein. Their alkaline solutions are fluorescent. [ 1913 Webster ] Phenol phthalein, a white or yellowish white crystalline substance made from phthalic acid and phenol. Same as phenolphthalein. [ 1913 Webster + PJC ]
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