Iron is a chemical element with symbol Fe. Iron is in +3 oxidation sate is called ferric ion. It is found in salt like ferric chloride. In group III, ferric ion is precipitated as its hydroxide by adding ammonium hydroxide to its solution. The reddish brown precipitate of ferric hydroxide is dissolved in HCl due to the formation of soluble ferric chloride. Ferric chloride reacts with potassium ferrocyanide to form prussian blue coloured Ferric ferrocyanide and potassium sulphocyanide to form blood red coloured Ferric sulphocyanide.
This video explains how to test for the presence of ferric ion in a given salt.