These indicators are obtained from natural sources like plants. Litmus is the most common example.
| Indicator | Color in Acid | Color in Base | Original/Neutral Color |
|---|---|---|---|
| Litmus Paper/Solution | Red | Blue | Purple (Solution) |
| Turmeric | Yellow | Reddish-Brown | Yellow |
These are man-made chemical substances used to determine if a solution is acidic or basic.
| Indicator | Color in Acid | Color in Base | Neutral Color |
|---|---|---|---|
| Phenolphthalein | Colorless | Pink | Colorless |
| Methyl Orange | Red | Yellow | Orange |
These are substances whose smell (odor) changes in acidic or basic media. They are particularly useful for visually impaired students.
| Indicator | Odor in Acid | Odor in Base |
|---|---|---|
| Onion Extract | Characteristic smell is retained | Smell is destroyed / cannot be detected |
| Vanilla Essence | Characteristic smell is retained | Smell is destroyed / cannot be detected |
| Clove Oil | Characteristic smell is retained | Smell is destroyed / cannot be detected |