It is a test for iron(III) ion present in the solution , so it is a chemical change The chemical reaction involved in it is Fe 3+ + SCN- -------> [Fe(NCS)(H2O)5]2+. blood red Solution It is a test for iron(III) ion present in the solution , so it is a chemical change The chemical reaction involved in it is Fe 3+ + SCN- -------> [Fe(NCS)(H2O)5]2+. blood red.