Webster's Revised Unabridged Dictionary · 1913

Phthalein

Phthalein , noun

[See Phthalic.]

(Chemistry) 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.
Collocations (1)
Phenol phthalein , a white or yellowish white crystalline substance made from phthalic acid and phenol. Same as phenolphthalein.