Question

What is Tollen's test used for?

Answer 1

As a means to distinguish between ketones and aldehydes.

Explanation:

This is a wet technique that would have been used 100 years ago. Tollens test differentiates between aldehydes and (most) ketones. The appearance of a silver mirror indicates the presence of an aldehyde.

It is a fact that the best silver mirrors (i.e. an antique mirror in which you would paint your face) were made by this chemical technique. That is submerge a glass sheet (one side of which had been waxed or greased) into a large bath of ammoniacal silver nitrate. Careful addition of a primary alcohol or aldehyde would cause reduction of the `Ag^+` onto one side of the glass plate (of course it would not stick to the greased side). Out of the bath would come a high quality silver mirror, ready for mounting in a decorative frame.