Materials:

* Three test tubes: One containing an acidic solution, one containing a basic solution, and one containing a neutral solution.

* Red litmus paper: This is the key indicator.

Procedure:

1. Label the Test Tubes: For clarity, label the test tubes A, B, and C.

2. Dip the Red Litmus Paper: Take a small piece of red litmus paper and dip it into test tube A. Observe the color change.

3. Observe and Interpret:

* If the red litmus paper turns blue: The solution in test tube A is basic.

* If the red litmus paper remains red: The solution in test tube A is either acidic or neutral.

4. Repeat Steps 2 and 3 for Test Tubes B and C: Make sure to use a fresh piece of red litmus paper for each test tube.

Determining the Neutral Solution:

* At this point, you will have one or two test tubes where the red litmus paper stayed red.

* To differentiate between acidic and neutral: You need to use a separate indicator called *blue litmus paper*.

* Blue litmus paper turns red in the presence of an acid. If either of your red-remaining solutions turns the blue litmus paper red, it is acidic. The other one is neutral.

Summary:

* Red litmus paper turning blue: Basic solution.

* Red litmus paper turning red: Acidic solution.

* Red litmus paper remaining red (and blue litmus paper remaining blue): Neutral solution.

Important Note: Always use fresh litmus paper for each test to avoid any contamination or false results.