Phenolphthalein is a chemical compound that is often used as an indicator in acid-base titrations. It is a weak acid that can lose H+ ions in solution, and the nonionized phenolphthalein molecule is colorless while the double deprotonated phenolphthalein ion is fuchsia. Phenolphthalein changes color depending on whether it meets an acid or a base. It turns purple if it meets something basic, such as ammonia, and it stays colorless if it meets an acid like vinegar or a neutral substance like water. Phenolphthalein is naturally colorless but turns pink in alkaline solutions. The compound remains colorless throughout the range of acidic pH levels but begins to turn pink at a pH level of 8.2 and continues to a bright magenta at pH 10 and above. In the chemistry laboratory, phenolphthalein is mostly used in acid-base titrations.