Using litmus paper to differentiate dilute hydrochloric acid and ammonium hydroxide solutions:

To differentiate between dilute hydrochloric acid and ammonium hydroxide solutions, you can use litmus paper. Litmus paper is a type of pH indicator paper that changes color when it comes into contact with acidic or basic substances. It consists of strips of paper that are impregnated with a natural pH indicator derived from lichens.

Materials required:
- Litmus paper (blue and red)
- Dilute hydrochloric acid solution
- Ammonium hydroxide solution
- Dropper or pipette for handling the solutions

Procedure:

1. Prepare the solutions:
- Dilute hydrochloric acid solution: Take a small amount of hydrochloric acid and dilute it with water to obtain a dilute solution. The concentration can vary depending on the desired strength.
- Ammonium hydroxide solution: Similarly, prepare a dilute solution of ammonium hydroxide by diluting it with water. The concentration can vary as well.

2. Obtain the litmus paper:
- Blue litmus paper: This paper turns red in the presence of an acid and remains blue in the presence of a base.
- Red litmus paper: This paper turns blue in the presence of a base and remains red in the presence of an acid.

3. Perform the test:
- Take a piece of blue litmus paper and dip it into the first solution (hydrochloric acid).
- Observe the color change of the litmus paper. If it turns red, it indicates the presence of an acid (hydrochloric acid).
- Rinse the litmus paper with water to remove any remaining acid and make it neutral before proceeding to the next step.
- Take a piece of red litmus paper and dip it into the second solution (ammonium hydroxide).
- Observe the color change of the litmus paper. If it turns blue, it indicates the presence of a base (ammonium hydroxide).

Interpretation of results:
- If the blue litmus paper turns red, it confirms the presence of an acid, indicating that the solution being tested is dilute hydrochloric acid.
- If the red litmus paper turns blue, it confirms the presence of a base, indicating that the solution being tested is ammonium hydroxide.
- If neither litmus paper changes color, it suggests that the solution is either neutral or very close to neutral on the pH scale.

Note:
- It is important to handle the solutions carefully and avoid direct contact with the skin or eyes, as both hydrochloric acid and ammonium hydroxide can be corrosive or irritant.
- Always dispose of the solutions properly according to safety guidelines.

At first we will put diute hydrochloric acid in the litmus paper. If it changes to red colour from blue then it is a acid. Again we will put ammonium hydroxide in litmus paper. If it changes to blue colour from red then it is a base.