Mercury(I) nitrate is an inorganic compound, a salt of mercury and nitric acid with the formula Hg2(NO3)2. A yellow solid, the compound is used as a precursor to other Hg22+ complexes. The structure of the hydrate has been determined by X-ray crystallography. It consists of a [H<sub>2</sub>O-Hg-Hg-OH<sub>2</sub>]2+ center, with a Hg-Hg distance of 254 pm.[1]
Mercury(I) nitrate is formed when elemental mercury is combined with dilute nitric acid (concentrated nitric acid will yield mercury(II) nitrate). 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):
Solutions of mercury(I) nitrate are acidic due to slow reaction with water:
Hg2(NO3)2 + H2O ⇌ Hg2(NO3)(OH) + HNO3Hg2(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:
These reactions are reversible; the nitric acid formed can redissolve the basic salt.