What are olfactory indicators ?

What are olfactory indicatiors ? How is an olfactory indicator used to test whether a given solution is an strength.

What is an olfactory indicator? Name two olfactory indicators. What is the effect of adding sodium hydroxide solution to these olfactory indicators?

Olfactory indicators are

Which of the following are not olfactory indicators ?

How do you appreciate the olfactory indicators?

Vanilla essence and olive oil are olfactory indicators.

Name two substances which can be used as olfactory indicators ?