The reaction with iron(III) chloride solution
Iron(III) chloride is sometimes known as ferric chloride.
Iron(III) ions form strongly coloured complexes with several organic compounds including phenol. The colour of the complexes vary from compound to compound. The reaction with iron(III) chloride solution can be used as a test for phenol.
If you add a crystal of phenol to iron(III) chloride solution, you get an intense violet-purple solution formed.