1. Plural of phthalein; a class of synthetic organic compounds derived from phthalic anhydride, used as dyes, indicators, and pigments in chemistry and industry.
Usage: technical; chemistry

Examples

• Phenolphthalein and other phthaleins are commonly used as pH indicators in laboratory titrations.
• The chemist synthesized several phthaleins to test their properties as acid-base indicators.
• Phthaleins are valued in the textile industry for their bright, stable colors.
• The phthalein family of compounds includes both natural and synthetic members used in research.
• Students learned to identify phthaleins by their characteristic color changes in different pH environments.