phthalin

from The Century Dictionary.

• noun A substance formed by the reduction of a phthalein. See phenolphthalin.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) A colorless crystalline substance obtained by reduction from phthaleïn, into which it is easily converted by oxidation; hence, any one of the series of which phthalin proper is the type.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry A colourless crystalline substance obtained by reduction from phthalein, into which it is easily converted by oxidation.
• noun chemistry Any of the series of which phthalin proper is the type.