Ionochromic materials, similar to
photochromic,
thermochromic and other
chromic materials, alter
colour in the presence of a factor and reverse to their initial state when the factor is removed. The factor which causes colour change in ionochromic substances are
ions. A flow of ions through an ionochromic material results in a reaction/colour change from the material. This material is in many ways similar to
electrochromic materials which change colour when electrons flow through them. Electrons, just like anions, carry a negative charge. Both electrochromic and ionochromic substances have their colour change activated by the flow of charged particles. Ionochromic substances are suitable for detection of charged particles. Some ionochromic substances can be used as
indicators for
complexometric titrations.