Question

What are olfactory indicators? Explain with an example the working of an olfactory indicator.

Answer 1

Olfactory indicators: Olfactory indicators are those which help us to identify an acidic or basic solution by changing its smell instead of colour.

Example: Onions.

• Onion has a pungent odor due to the sulphur-containing volatile compound Propanethial-S-oxide. When the onion is treated with an acidic solution its odour retains, but when it is treated with a basic solution it loses its characteristic odor.

Vanilla:

• Vanilla is another example of an olfactory indicator.
• Vanilla also retains its essence with an acidic solution but it loses its essence with basic solutions.