What are Metallochromic indicators?
John Peck
Updated on April 05, 2026
Metallochl’Omic indicators are defined as organic dyes exhibiting marked acido-basic colour changes and containing a grouping capable of chelate bond formation directly joined to the conjugated system of the dye.
Is EBT a metal ion indicator?
It is an azo dye. Eriochrome is a trademark of Huntsman Petrochemical, LLC. In its deprotonated form, Eriochrome Black T is blue. It turns red when it forms a complex with calcium, magnesium, or other metal ions….Eriochrome Black T.
| Names | |
|---|---|
| Abbreviations | EBT |
| Beilstein Reference | 4121162 |
| ECHA InfoCard | 100.015.683 |
| EC Number | 217-250-3 |
Which indicator is used in Iodimetry and Iodometry?
starch
The indicator that is usually chosen for titrations involving iodine (triiodide) is starch. Starch forms a dark blue complex with iodine. The end point in iodimetry corresponds to a sudden color change to blue. Likewise the end point in iodometry corresponds to a sudden loss of blue color due to the complex.
Is phenolphthalein an indicator?
Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions. It belongs to the class of dyes known as phthalein dyes.
How does eriochrome black act as indicator?
Eriochrome Black T is a complexometric indicator that is used in complexometric titrations, e.g. in the water hardness determination process. It is an azo dye. In its deprotonated form, Eriochrome Black T is blue. It turns red when it forms a complex with calcium, magnesium, or other metal ions.
What is the colour of eriochrome black T indicator?
blue
A blue dye called Eriochrome Black T (ErioT) is used as the indicator. This blue dye also forms a complex with the calcium and magnesium ions, changing colour from blue to pink in the process.
Why do metal-metallochromic indicators change colour at the end-point?
When the formation of metal-metallochromic indicator complexes is accompanied by the release of more than one proton per indicator molecule complexed, the colour change at the end-point is sharper than that of a conventional acid-base indicator, when only one proton is released.
Why do we need metallochromic pH indicators?
Because complexes of different stabilities are formed between metals and metallochromic indicators, one such indicator can provide a whole range of pH indicators by variation of the metal ion used.
What are the types of indicators used in Chemical Engineering?
Types of Indicators 1 Acid-Base Indicator 2 Natural acid-base indicators 3 Indicators of oxidation-reduction reactions (redox) 4 Adsorption (precipitation) indicators 5 Metallochromic or complexometric indicators 6 Chemical indicators with luminescence capacity 7 Chemical moisture indicators 8 Chemical indicators of sterilization
What are the four types of indicators?
Metallochromic indicators, adsorption indicators, oxidation-reduction indicators, and fluorescent and chemiluminescent indicators are also considered. This volume is comprised of 10 chapters and begins with a brief history of indicators, including the contribution of Robert Boyle in the field.
