Eriochrome Black T

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Eriochrome Black T
Wireframe model of an eriochrome black T minor tautomer
Sample of Eriochrome Black T
Names
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
Identifiers
Abbreviations EBT
4121162
1787-61-7 N
ChemSpider 10483790 YesY
EC number 217-250-3
Jmol-3D images Image
MeSH Eriochrome+black+T
PubChem 6808871
5359641 (4E)
5351620 (4Z)
RTECS number QK2197000
UN number 2923
Properties
C20H12N3O7SNa
Molar mass 461.381 g/mol
Appearance dark red/brown powder
Acidity (pKa) 6.2, 11.55
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N verify (what isYesY/N?)
Infobox references

Eriochrome Black T is a complexometric indicator that is part of the 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 protonated form, Eriochrome Black T is blue. It turns red when it forms a complex with calcium, magnesium, or other metal ions.

EBT is blue in a buffered solution at pH 10. It turns red when Ca2+ ions are added.

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]

External links[edit]