The structure of the hydrate has been determined by X-ray crystallography.
It consists of a [H2O-Hg-Hg-OH2]2+ center, with a Hg-Hg distance of 254 pm.
Mercury(I) nitrate is a reducing agent which is oxidized upon contact with air.
Mercuric (II) nitrate reacts with elemental mercury (0) to form mercurous (I) nitrate (comproportionation reaction):[citation needed] Solutions of mercury(I) nitrate are acidic due to slow reaction with water: Hg2(NO3)(OH) forms a yellow precipitate.
If the solution is boiled, or exposed to light, mercury(I) nitrate undergoes a disproportionation reaction yielding elemental mercury and mercury(II) nitrate:[3] These reactions are reversible; the nitric acid formed can redissolve the basic salt.