Phenolphthalein Indicator 25g (Merck) is a chemical substance used primarily as a pH indicator in various laboratory applications, particularly in titrations. Merck is a well-known and reputable chemical manufacturer, so their product is expected to be of high quality and purity.

Phenolphthalein indicator ACS, Reag. Ph Eur

• Formula: C20H14O4
• Molecular weight: 318,33 g/mol
• Pack Size: 25 gm
• Origin: Germany
• Made in India

Key Features:

1. Chemical Name:
   • The active compound is Phenolphthalein, a common acid-base indicator.
2. Appearance:
   • It is typically a white to pale pink powder or crystalline substance. In solution, phenolphthalein is colorless in acidic conditions and turns pink to red in basic (alkaline) conditions.
3. Quantity:
   • The 25g package is a standard size for laboratory use and provides enough material for frequent use in titrations or other experiments.
4. Purity:
   • As a Merck product, it is likely to have a high level of purity, often indicated as >99% or similar, making it suitable for precise analytical work.
5. Chemical Formula:
   • C20H14O4 — phenolphthalein is an organic compound with a molecular weight of about 318.34 g/mol.
6. pH Range:
   • Phenolphthalein undergoes a color change between pH 8.3 and 10. It is colorless in acidic solutions (pH < 8) and turns pink to red as the pH increases above 8.3.
7. Common Uses:
   • Titrations: Phenolphthalein is frequently used in acid-base titrations to indicate the endpoint.
   • pH Indicator: It helps determine the pH of a solution, particularly for weak acid and strong base titrations.
   • Buffer Preparation: It can be used in the preparation and calibration of buffers.

How It Works:

• Acidic Solutions: In an acidic environment (pH < 7), phenolphthalein remains colorless.
• Neutral Solutions: At pH ~7, phenolphthalein is also colorless.
• Basic Solutions: As the pH becomes alkaline (pH > 8.3), phenolphthalein turns from colorless to pink, and at higher pH (pH > 10), it may become more intensely red.

Safety Precautions:

• Handling: Phenolphthalein should be handled with care, wearing gloves, goggles, and appropriate protective clothing. Though it is not highly toxic, it can irritate the eyes and skin.
• Storage: Store in a cool, dry place, away from strong acids or bases. The container should be tightly sealed to prevent contamination.

General Applications of Phenolphthalein Indicator:

1. Titration: Phenolphthalein is used as an endpoint indicator for titrations of strong bases with weak acids. The endpoint is reached when the solution changes from colorless to pink, signaling the neutralization point.
2. Water Quality Testing: It is used in testing the alkalinity or acidity of water samples.
3. Buffer Solutions: Phenolphthalein helps define the working range of buffer solutions in analytical chemistry.

Preparation of Indicator Solution:

• For titrations: You can prepare a 1% (w/v) phenolphthalein solution by dissolving 1g of phenolphthalein in 100mL of ethanol (or isopropanol) and then diluting it to the desired volume with distilled water. Alternatively, you can dissolve phenolphthalein directly in water, but it is typically more stable in an alcohol-based solution.