Question

What is an olfactory indicator? Name two such indicators.

Answer 1

Hint: We know that an Olfactory indicator is a substance whose smell varies depending on whether it is mixed with an acidic or basic solution. Olfactory indicators can be used in the laboratory to test whether a solution is a base or an acid, a process called olfactory titration.

Complete step by step answer:
As we know that some substances whose smell or odor changes in acidic or basic solutions are called olfactory indicators.
We have to remember that onion and vanilla extracts are olfactory indicators. Vanilla essence is an olfactory indicator. As we know that, its smell is different in acidic and basic mediums which can be detected easily by a visually impaired student. Also, we should note that vanilla extract has a characteristic pleasant smell. An acidic solution like hydrochloric acid, however, does not destroy the smell of vanilla extract. But a basic solution destroys the smell of vanilla extract.
When a basic solution like sodium hydroxide solution is added to a cloth strip treated with onions (or onion extract), then the onion smell cannot be detected.
An olfactory indicator works on the principle that when an acid or base is added to it, then different odor can be detected in bases whereas the odor remains the same in acids. Certain substances that change its odor in Acidic or basic medium.

Note: We have to remember that other than onion and vanilla, clove oil and ginger are also examples of an olfactory indicator. In acidic medium we can easily categorize the smell of clove but it is not possible in a basic medium, to detect the smell of the substance.