Tollens’ reagent

What is Tollens’ reagent?

Tollen’s reagent is a solution of ammonium hydroxide NH4OH and silver nitrate AgNO3 that is used to test for the presence of aldehydes.

Tollen's reagent
Tollen’s reagent

When Tollen’s reagent is added to an aldehyde, it forms a silver mirror on the surface of the solution, indicating the presence of an aldehyde.


  • Tollens, B. (1882), Ueber ammon-alkalische Silberlösung als Reagens auf Aldehyd. [On ammonium-alkaline silver solution as a reagent on aldehyde.] Ber. Dtsch. Chem. Ges., 15: 1635-1639.
  • Ponndorf, W. (1931), Argentometrische Aldehyd-Bestimmung. [Argentometric aldehyde determination.] Ber. dtsch. Chem. Ges. A/B, 64: 1913-1923.