Nitroso-nitrogen Trioxide, (N₃O₄)_x

When nitric oxide is passed through liquid air or oxygen, or when air or oxygen acts on solid nitric oxide at -185° C., a green solid is produced which was assumed to be nitrogen hexoxide, NO₃ or N₂O₆. The same oxide was considered to be formed by the action of a silent discharge through a mixture of nitrogen, or nitrogen tetroxide and oxygen, or by the action of an induction current on a mixture of nitrogen tetroxide and oxygen.

The green solid mentioned above is now assumed to be nitroso-nitrogen trioxide, having an empirical formula N₃O₄, and is produced according to the following reaction:



This peroxidised polymeride of nitric oxide is irreversibly converted into nitrogen trioxide.