An olfactory indicator is a substance that changes its smell when it reacts with an acid or a base. These indicators help us identify whether a solution is acidic or basic through the sense of smell.
Two examples of olfactory indicators are:
1. Vanilla: In acidic solutions, it retains its sweet smell, while in basic solutions, it may have a different, less pleasant odor.
2. Onion: When mixed with an acid, it can produce a strong smell, but in a basic solution, the smell changes.
These indicators are useful in chemistry to detect pH changes without using color.
