Editing Tollens' reagent (section)

==Laboratory preparation==
This reagent is not commercially available due to its short [[shelf life]], so it must be freshly prepared in the laboratory. One common preparation involves two steps. First a few drops of dilute [[sodium hydroxide]] are added to some aqueous 0.1&nbsp;[[molar (unit)|M]] [[silver nitrate]]. The <chem>OH-</chem> ions convert the [[transition metal aquo complex|silver aquo complex]] form into [[silver oxide|silver(I) oxide]], <chem>Ag2O</chem>, which precipitates from the solution as a brown solid: 
:<chem>2AgNO3 + 2NaOH   -> Ag2O(s)  +  2NaNO3 +  H2O</chem>

In the next step, sufficient [[aqueous ammonia]] is added to dissolve the brown silver(I) oxide. The resulting solution contains the [Ag(NH<sub>3</sub>)<sub>2</sub>]<sup>+</sup> complexes in the mixture, which is the main component of Tollens' reagent. Sodium hydroxide is reformed:
:<chem>Ag2O(s) + 4NH3 + 2NaNO3 + H2O -> 2[Ag(NH3)2]NO3 + 2NaOH </chem>

Alternatively, [[aqueous ammonia]] can be added directly to silver nitrate solution.<ref name = webpath/> At first, ammonia will induce formation of solid silver oxide, but with additional ammonia, this solid precipitate dissolves to give a clear solution of diamminesilver(I) [[coordination complex]], <chem>[Ag(NH3)2]+</chem>. Filtering the reagent before use helps to prevent false-positive results.