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Saturday, October 22, 2022

Preparation of α-Naphtholbenzein indicator solution

Learn the procedure for making 1-Naphtholbenzein indicator solution.

The compound that changes color when exposed to acidic or basic solutions is called an indicator. Most of the time, color indicators are used to measure pH. They are added to the reaction mixture to find the endpoint or equivalence point of the titration.

α-Naphtholphthalein (C28H18O4) is a dye, chemically describes as 4, 4′-(α-Hydroxybenzylidene)di-1-naphthol, p-naphtholbenzein

α-Naphtholbenzein has been used as a pH indicator during the acid-base titration method which changes color from colorless/reddish to greenish blue at pH 7.3–8.7. It changes from green (basic) to orange (neutral) to yellow (acidic) when used as an indicator for non-aqueous titrations.

Naphtholbenzein is a solid that is colorless to slightly reddish or blue-green. It dissolves in ethanol, acetic acid, and acetone, but not in water.

How to prepare dichlorofluorescein indicator for titration?

  • Accurately weigh 0.2 g of 1-Naphtholbenzene and pour it into a 100 ml volumetric flask with 50 ml of acetic acid.
  • Once it is dissolved, dilute it to 100.00 mL with acetic acid.
  • The concentration of the prepared solution is about 2.0 g/L.


References:
  1. Wikipedia contributors. (2022, April 3). Naphtholphthalein. In Wikipedia, The Free Encyclopedia. Available Here:
  2. Law.resource.org. 2022. [online] Available Here:

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