Ionochromic materials, similar to photochromic

Photochromism

Photochromism is the reversible transformation of a chemical species between two forms by the absorption of electromagnetic radiation, where the two forms have different absorption spectra. Trivially, this can be described as a reversible change of colour upon exposure to light...

, thermochromic and other chromic

Chromism

In chemistry, chromism is a process that induces a change, often reversible, in the colors of compounds. In most cases, chromism is based on a change in the electron states of molecules, especially the π- or d-electron state, so this phenomenon is induced by various external stimuli which can alter...

 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 ion

Ion

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

s. 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

Complexometric indicator

A complexometric indicator is an ionochromic dye that undergoes a definite color change in presence of specific metal ions. It forms a weak complex with the ions present in the solution, which has a significantly different color from the form existing outside the complex.Complexometric indicators...

 for complexometric titration

Complexometric titration

Complexometric titration is a form of volumetric analysis in which the formation of a colored complex is used to indicate the end point of a titration. Complexometric titrations are particularly useful for the determination of a mixture of different metal ions in solution...

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