Phenolphthalein Test

Phenolphthalein test is a presumptive test used for the identification of blood. It is based on the catalytic peroxidase-like activity of the heme group in hemoglobin, which is present in red blood cells. In the presence of hydrogen peroxide, this peroxidase-like activity catalyzes the oxidation of Phenolphthalin, a colorless compound, into Phenolphthalein, which is pink in color. The test is conducted on suspected bloodstains before collection.

How to Use Phenolphthalein Indicator

To use Phenolphthalein as an indicator, follow these steps:

• Prepare Indicator Solution: Dissolve a known amount of Phenolphthalein in a suitable solvent, such as ethanol or water, to create a solution with a known concentration.

• Add Indicator Solution to Test Solution: Add a few drops of the Phenolphthalein solution to the test solution, which could be an acidic or basic solution, depending on the test’s purpose.

• Observe Color Change: The color change indicates the pH of the test solution.

• Record Results: Document the color change observed in the test solution, as this information can be used to determine the acidity or basicity of the solution.

Color Changes in Acidic and Alkaline Solutions

Color Changes in Acidic and Alkaline Solutions is observed as,

• Color of Phenolphthalein in Acid: Phenolphthalein is colorless in Acidic Solutions

• Color of Phenolphthalein in Base: Phenolphthalein turns pink to deep red in Basic Solutions around pH 9

Phenolphthalein (C₂₀H₁₄O₄) is an organic chemical compound often used as an indicator in acid-base titrations. It is slightly soluble in water and usually is dissolved in alcohol in experiments. It is a weak acid and belongs to the phthalein dyes class. Phenolphthalein is colorless below pH 8.5 and attains a pink to deep red hue above pH 9.0.

In this article, we will look into What is Phenolphthalein, Phenolphthalein Formula, Phenolphthalein Structure, Uses of Phenolphthalein, and others in detail.