M-Methyl Red NEW

Methyl Red (often abbreviated as M-Methyl Red) is another pH indicator that is commonly used in laboratory experiments, particularly in acid-base titrations and in microbiological testing. It is part of the group of azo dyes and changes color depending on the pH of the solution.

Key Characteristics:

• Color Change: Methyl Red exhibits a distinct color change from red at low pH (acidic conditions) to yellow at higher pH (basic conditions).

• pH Transition Range: The pH range for the color change is between pH 4.4 and 6.2, with the indicator being red below pH 4.4 and yellow above pH 6.2.

Applications:

1. Acid-Base Titrations

• Titrations involving weak bases and strong acids: Methyl Red is used in titrations where the pH at the endpoint is slightly acidic, such as when titrating a weak base with a strong acid. The pH at the endpoint of such reactions usually falls within the pH range where Methyl Red changes color.

2. Microbiological Testing (MR-VP Test)

• In this test, Methyl Red is used to detect mixed acid fermentation by certain bacteria (e.g., Escherichia coli), which produces acidic end products that drop the pH below 4.4. When the Methyl Red indicator is added to the culture, a red color indicates a positive result for mixed acid fermentation, while a yellow color indicates a negative result.

• Methyl Red Test (MR Test): In microbiology, Methyl Red is part of the MR-VP test (Methyl Red and Voges-Proskauer test) to differentiate between bacterial species based on their ability to ferment glucose.

3. pH Indicator

• General pH Testing: Like other indicators, Methyl Red is used in various chemical experiments to visually assess the pH of a solution. It is commonly used in both educational and industrial laboratories when an acidic pH range needs to be confirmed.

4. Environmental Chemistry

• Water Quality Monitoring: Methyl Red can be used in environmental testing to assess the acidity of water samples. This is particularly useful in cases where water becomes acidic due to pollution or runoff, and the pH needs to be monitored for safety.

Properties:

• Molecular Formula: $C_{15}H_{15}N_3O_2$

• Structure: Methyl Red is an azo dye, where the nitrogen-nitrogen double bond (azo group) is part of the structure that facilitates its pH-sensitive color change.

In summary, Methyl Red (M-Methyl Red) is a widely used pH indicator, particularly valuable in acid-base titrations, microbiological tests, and general laboratory applications requiring pH assessment within a slightly acidic range.