Q1.
If litmus is not available, are there some other natural substances that can serve as acid-base indicators?
Answer
Yes — plenty of them, and most are already in your kitchen or garden. Any strongly coloured plant part whose colour changes in acid or base will work.
| Natural indicator | Colour in acid | Colour in base |
|---|---|---|
| Red rose extract | Red | Green |
| Turmeric (haldi) | Stays yellow | Red |
| Purple cabbage extract | Reddish pink | Green |
| Beetroot extract | Stays red-pink | Yellowish |
| Red hibiscus (gudhal) | Pink to red | Green |
| Jamun (Indian blackberry) | Bright red-pink | Dull greenish |
Why so many flowers work: the red, pink and purple colours of petals and fruits come from a family of dyes called anthocyanins, and these dyes change form — and therefore colour — depending on whether the liquid around them is acidic or basic. Litmus from lichens is only the most famous member of a very large family.
Try This: squeeze jamun juice into two glasses. Add lemon juice to one, baking soda solution to the other. The two glasses will not look like they started from the same fruit.