Eriochrome Black T
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Names | |
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Preferred IUPAC name Sodium 1-[1-Hydroxynaphthylazo]-6-nitro-2-naphthol-4-sulfonate | |
Systematic IUPAC name Sodium 4-[2-(1-hydroxynaphthalen-2-yl)hydrazin-1-ylidene]-7-nitro-3-oxo-3,4-dihydronaphthalene-1-sulfonate | |
Other names Sodium 4-[2-(1-hydroxynaphthalen-2-yl)hydrazin-1-ylidene]-7-nitro-3-oxonaphthalene-1-sulfonate; Solochrome Black T; ET-00; Erio T | |
Identifiers | |
3D model (JSmol) | |
Abbreviations | EBT |
4121162 | |
ECHA InfoCard | 100.015.683 |
EC Number |
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MeSH | Eriochrome+black+T |
PubChem CID | |
RTECS number |
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UNII | |
UN number | 2923 |
CompTox Dashboard (EPA) | |
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Properties | |
C20H12N3O7SNa | |
Molar mass | 461.381 g/mol |
Appearance | dark red/brown powder |
Acidity (pKa) | 6.2, 11.55 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
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. Eriochrome is a trademark of Huntsman Petrochemical, LLC.[1]
In its deprotonated form, Eriochrome Black T is blue. It turns red when it forms a complex with calcium, magnesium, or other metal ions.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/30/Eriochrome_Black_T_indicator_color_change.jpg/400px-Eriochrome_Black_T_indicator_color_change.jpg)
Applications
[edit]When used as an indicator in an EDTA titration, the characteristic blue end-point is reached when sufficient EDTA is added and the metal ions bound to the indicator are chelated by EDTA, leaving the free indicator molecule.
Eriochrome Black T has also been used to detect the presence of rare earth metals.[2]
References
[edit]- ^ "Eriochrome Black T ACS reagent indicator grade 1787-61-7".
- ^ Dubenskaya, L. O.; Levitskaya, G. D. (1999). "Use of Eriochrome black T for the polarographic determination of rare-earth metals". Journal of Analytical Chemistry. 54 (7): 655–657. ISSN 1061-9348. Archived from the original on 2010-10-01. Retrieved 2007-06-05.