Pernitric Acid, HNO₄

The supposed nitrogen hexoxide was considered to give a Pernitric Acid, HNO₄, with water. Oxidation of nitrous acid in solution by 3 per cent, hydrogen peroxide solution is stated by Raschig to produce pernitric acid:

HNO₂ + 2H₂O₂ = HNO₄ + 2H₂O.

The decomposition of pernitric acid by water occurs slowly, according to the reaction

HNO₄ + H₂O = HNO₃ + H₂O₂.

Pure hydrogen peroxide and nitrogen pentoxide at low temperatures yield a substance exhibiting typical properties of a per-acid:

H₂O₂ + N₂O₅ = HNO₄ + HNO₃.

Bromine is liberated from potassium bromide, and aniline is oxidised to nitroso-benzene by the acid.

Electrolysis of a solution of silver nitrate yields a black crystalline precipitate, assumed to be the silver salt of pernitric acid.