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  2. Phenolphthalein - Wikipedia

    en.wikipedia.org/wiki/Phenolphthalein

    Phenolphthalein (/ fɛˈnɒl (f) θəliːn / [citation needed] feh-NOL (F)-thə-leen) is a chemical compound with the formula C 20 H 14 O 4 and is often written as " HIn ", " HPh ", " phph " or simply " Ph " in shorthand notation. Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless ...

  3. pH indicator - Wikipedia

    en.wikipedia.org/wiki/PH_indicator

    A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH (acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. [1] Hence, a pH indicator is a chemical detector for hydronium ions (H 3 O +) or hydrogen ions (H +) in the ...

  4. Universal indicator - Wikipedia

    en.wikipedia.org/wiki/Universal_indicator

    Universal indicator. A universal indicator is a pH indicator made of a solution of several compounds that exhibit various smooth colour changes over a wide range pH values to indicate the acidity or alkalinity of solutions. A universal indicator can be in paper form or present in a form of a solution. [1]

  5. Acid–base titration - Wikipedia

    en.wikipedia.org/wiki/Acid–base_titration

    An acid–base titration is a method of quantitative analysis for determining the concentration of Brønsted-Lowry acid or base (titrate) by neutralizing it using a solution of known concentration (titrant). [1] A pH indicator is used to monitor the progress of the acid–base reaction and a titration curve can be constructed.

  6. Invisible ink - Wikipedia

    en.wikipedia.org/wiki/Invisible_ink

    In most cases, these substance changes color when mixed with an acid or base. Phenolphthalein, commonly used as a pH indicator, turns pink in the presence of a base such as ammonia fumes or sodium carbonate. Vinegar, is revealed by red cabbage water [12] Vinegar contains acetic acid that affects the pH indicator in red cabbage water. Vinegar ...

  7. Equivalence point - Wikipedia

    en.wikipedia.org/wiki/Equivalence_point

    An acid-base indicator (e.g., phenolphthalein) changes color depending on the pH. Redox indicators are also frequently used. A drop of indicator solution is added to the titration at the start; when the color changes the endpoint has been reached, this is an approximation of the equivalence point. Conductance

  8. Phenol red - Wikipedia

    en.wikipedia.org/wiki/Phenol_red

    Its solubility is 0.77 grams per liter (g/L) in water and 2.9 g/L in ethanol. [1] It is a weak acid with pK a = 8.00 at 20 °C (68 °F). A solution of phenol red is used as a pH indicator, often in cell culture. Its color exhibits a gradual transition from yellow (λ max = 443 nm [2]) to red (λ max = 570 nm [3]) over the pH

  9. Kastle–Meyer test - Wikipedia

    en.wikipedia.org/wiki/Kastle–Meyer_test

    The Kastle–Meyer test is a presumptive blood test, first described in 1903, in which the chemical indicator phenolphthalein is used to detect the possible presence of hemoglobin. It relies on the peroxidase -like activity of hemoglobin in blood to catalyze the oxidation of phenolphthalin (the colorless reduced form of phenolphthalein) into ...