text: 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 M silver nitrate. The  ions convert the silver aquo complex form into silver(I) oxide, , which precipitates from the solution as a brown solid: 
  In the next step, sufficient aqueous ammonia is added to dissolve the brown silver(I) oxide. The resulting solution contains the [Ag(NH)] complexes in the mixture, which is the main component of Tollens' reagent. Sodium hydroxide is reformed:
  Alternatively, aqueous ammonia can be added directly to silver nitrate solution. 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, . Filtering the reagent before use helps to prevent false-positive results.