When aniline reacts with ferric nitrate, a deep blue colored solution is formed. This is due to the formation of a complex ion between the aniline and the ferric ions.

Here's a breakdown:

* Aniline (C6H5NH2) is a primary aromatic amine. It has a lone pair of electrons on the nitrogen atom.

* Ferric nitrate (Fe(NO3)3) is a salt containing ferric ions (Fe3+). Ferric ions have a strong affinity for electron-rich species.

Reaction:

The lone pair on the nitrogen of aniline donates electrons to the empty d-orbitals of the ferric ion, forming a coordination complex. This complex is highly colored due to the interaction of the d-orbitals in the ferric ion with the electrons of the aniline molecule.

Overall, the reaction is a complexation reaction that results in the formation of a blue-colored solution.

Note: This reaction is a qualitative test for aniline, as the deep blue color is a characteristic indication of the presence of aniline.