-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 ]