Ferric chloride (FeCl3) reacts with salicylate ions (from salicylic acid or its salts) to form a deep purple colored solution.

This reaction is a classic example of a colorimetric test used in analytical chemistry to detect the presence of salicylic acid.

Here's a breakdown:

* FeCl3 is a yellowish-brown solution.

* Salicylate ions are colorless.

* When they react, a complex is formed with a distinct purple color.

This reaction is based on the formation of a complex between the ferric ion (Fe3+) and the phenolic hydroxyl group of salicylic acid. The formation of this complex leads to the characteristic purple color.