Complexometric indicator

A complexometric indicator is an ionochromic dye that undergoes a definite color change in presence of specific metal ions.^[1] 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 are also known as pM indicators.^[2]

Complexometric titration

In analytical chemistry, complexometric indicators are used in complexometric titration to indicate the exact moment when all the metal ions in the solution are sequestered by a chelating agent (most usually EDTA). Such indicators are also called metallochromic indicators.

The indicator may be present in another liquid phase in equilibrium with the titrated phase, the indicator is described as extraction indicator.

Some complexometric indicators are sensitive to air and are destroyed. When such solution loses color during titration, a drop or two of fresh indicator may have to be added.

Examples

Complexometric indicators are water-soluble organic molecules. Some examples are:

• Eriochrome Black T for calcium, magnesium and aluminium
• Xylenol orange for gallium, indium and scandium
• Methyl calcein blue
• Murexide
• Fast Sulphon Black
• Eriochrome Red B
• Calcein
• Calcon
• Eriochrome blue-black B
• Eriochrome blue SE
• Hydroxynaphthol blue
• Methylthymol blue
• Phthalein purple
• Pyrogallol red
• 3,3'-dimethylnaphthidine
• Chromazurol S
• Hematoxylin for copper
• Naphthol green B
• 1-(2-pyridilazo)-2-naphthol (PAN)
• Calmagite
• 2-Cresolphthalexon

Redox indicators

In some settings, when the titrated system is a redox system whose equilibrium is influenced by the removal of the metal ions, a redox indicator can function as a complexometric indicator.

References

1. ^ Flaschka, H.; Schwarzenbach, G.; Schwarzenbach, Gerold (1969). Complexometric titrations. London: Methuen. ISBN 0-416-19290-4. 
2. ^ M. A. Malati (1999). Experimental Inorganic/Physical Chemistry: An Investigative, Integrated Approach to Practical Project Work (Horwood Series in Chemical Science). Albion/Horwood Pub. p. 20. ISBN 1-898563-47-0. 

This article about analytical chemistry is a stub. You can help Wikipedia by expanding it.v · Categories: Analytical chemistry Complexometric indicators Analytical chemistry stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем написать реферат Doctrine of Election Fred G. Meyer Look at other dictionaries: Complexometric titration — (sometimes chelatometry) 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… …   Wikipedia Indicator — may mean:* pH indicator, a chemical detector for protons in acid base titrations * Redox indicator, a chemical detector for redox titrations * Complexometric indicator, a chemical detector for metal ions in complexometric titrations * Zeta… …   Wikipedia complexometric — adjective a) Describing a form of titration in which the titrant forms a complex (usually coloured) with the analyte b) Describing any indicator that is used in such titrations See Also: complexometry …   Wiktionary pH indicator — Acids and Bases Acid dissociation constant Acid base extraction Acid–base reaction Acid–base titration Dissociation constant Acidity function Buffer sol …   Wikipedia Eriochrome Black T — Chembox new ImageFile = Erio T.svg IUPACName = sodium (4Z) 4 [(1 hydroxynaphthalen 2 yl hydrazinylidene] 7 nitro 3 oxo Y naphthalene 1 sulfonate OtherNames = Eriochrome Black T, Solochrome Black T, EBT Section1 = Chembox Identifiers CASNo = 1787… …   Wikipedia Murexide — IUPAC name Ammonium 2,6 dioxo 5 [(2,4,6 trioxo 5 hexahydropyrimidinylidene)amino] 3H pyrimidin 4 olate …   Wikipedia Calcein — Chembox new Name = Calcein ImageFile = Calcein.svg ImageName = IUPACName = Section1 = Chembox Identifiers CASNo = 1461 15 0 SMILES = O=C(O5)c1ccccc1C (c3cc(CN(CC(O)=O) CC(O)=O)c(O)cc3O4) 5c2c4cc(O)c(CN(CC (O)=O)CC(O)=O)c2 Section2 = Chembox… …   Wikipedia murexide — noun Ammonium purpurate, the ammonium salt of purpuric acid, used as a complexometric indicator and a colorimetric reagent …   Wiktionary Thermometric titration — titration systems have pre dominated in this area since the 1970 s. With the advent of cheap computers able to handle the powerful thermometric titration software, development has now reached the stage where easy to use automated thermometric… …   Wikipedia Titration — [ frame|Titration setup: the titrant drops from the burette into the analyte solution in the flask. An indicator present then changes color permanently at the endpoint.] Titration is a common laboratory method of quantitative chemical analysis… …   Wikipedia 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”