Tollen's reagent is Ag(NHsubscript3)subscript2+. The reagent is a basic, colorless, watery solution. Chemists can create it using a two-step procedure that involves a water-based sodium hydroxide.
Tollen's reagent is frequently used in what is called "the silver mirror test." The test is used to determine whether a substance is a aldehyde or a ketone. It oxidizes the substance to distinguish between the two because aldehydes are easily oxidized. When the substance is an aldehyde, the test tube looks as if it forms a mirror because of the reaction, hence the name of the test. Ketones do not produce the same mirror-like result.