Question

what is the effect of adding sodium hydroxide solution to these olfactory indicators

Answer 1

this is your answer to your questions

Answer 2

Olfactory Indicators are the indicators used for the senses of smell which indicates the change of the medium of the solution either basic or acidic solution.

Explanation:

Those substances which changes smell according to the medium of "acidity and alkalinity". Solution of Sodium hydroxide when added to the substance like onion or vanilla, which are the olfactory indicator, the smell of olfactory indicator is not indicated. Therefore, alkaline solution changes the smell.