How to prepare phenol red indicator

How to prepare phenol red indicator: detailed steps and precautions

Phenol red indicator is widely used in chemical experiments, especially in acid-base titration and pH determination of solution. It indicates the acidity and alkalinity of the solution by changing color. This article will introduce in detail how to prepare phenol red indicator, the steps are clear, to help you master its preparation skills.

1. What is phenol red indicator?

Phenol Red is a commonly used pH indicator with the chemical formula C19H14O5S. Its color range is usually between pH 4.8 and 7.4. Under acidic conditions, phenol red is yellow; under alkaline conditions, phenol red is red. Due to its significant color change, phenol red is often used as an indicator in water quality testing, acid-base titration and cell culture.

2. Phenol red indicator preparation method

Materials required:

• Phenol Red Powder
• Distilled water
• 1M sodium hydroxide solution (for pH adjustment)
• 1M hydrochloric acid solution (for pH adjustment)
• Burette or beaker

Steps:

1. Weigh phenol red powder Accurately weigh an appropriate amount of phenol red powder (typically 0.1 grams) and place it in a beaker.

2. Dissolved Phenol Red Powder Add about 100 ml of distilled water and stir until the phenol red is completely dissolved and the solution should be clear without precipitation. If the solution is not completely dissolved, it can be heated slightly, but excessive temperatures should be avoided.

3. Adjust pH The phenol red solution usually needs to be adjusted to the appropriate pH range. The pH was adjusted using 1M sodium hydroxide solution or 1M hydrochloric acid solution. If an acidic solution is required, a hydrochloric acid solution can be used to adjust the pH to about 6.0; if an alkaline solution is required, a sodium hydroxide solution can be used to adjust the pH to about 9.0.

4. Storage and use The phenol red indicator solution can be used directly or stored in a closed glass bottle away from direct sunlight. Make sure the bottle mouth is sealed during storage to prevent evaporation or contamination of the solution.

3. Phenol red indicator of common use

Phenol red indicator is widely used in many chemical experiments because of its bright color change. The most common uses include:

• Acid-base titration: In acid-base titration experiments, phenol red as an indicator can accurately display the solution pH changes.
• Water Quality Monitoring: Used to monitor water acidity and alkalinity, especially in laboratory water quality analysis.
• Cell culture: in the cell culture medium with phenol red, used to indicate the culture environment of acid-base balance, to ensure cell health growth.

4. How to improve phenol red indicator accuracy?

In the preparation of phenol red indicator, in order to ensure its use effect, the following points need special attention:

• Solubility problem: The solubility of phenol red in water is low. It is recommended to use pure distilled water and keep the solution fully stirred to improve solubility.
• pH adjustment: When using, ensure that the pH value of the solution is accurately controlled in the required range, which will affect the color change range of phenol red, and then affect the experimental results.
• Storage environment: Phenol red indicator is easily affected by light and temperature, long time storage to avoid direct sunlight, and keep at room temperature conditions, to avoid the solution color change or degradation.

5. Frequently Asked Questions and Answers

Q1: How to judge whether the phenol red indicator has expired? If the phenol red indicator solution changes color or precipitates, it may indicate that it has deteriorated. Check whether the solution can still show obvious color change. If the color of acid-base change cannot be displayed, a new indicator should be considered.

Q2: How to make different concentrations of phenol red indicator? According to the experimental requirements, the concentration of phenol red can be adjusted appropriately. The common concentration of phenol red is 0.1%. If higher or lower concentration is required, it can be prepared by adjusting the mass of phenol red powder and the volume of water.

6. Summary

How to prepare phenol red indicator? This process is not complicated, just pay attention to the dissolution, pH adjustment and storage methods. As an important pH indicator, phenol red is widely used in chemical analysis, environmental monitoring and biological experiments. Understanding its preparation methods and precautions can help improve the accuracy and reliability of experiments.