Eriochrome Black T
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Eriochrome Black T |
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| Systematic (IUPAC) name | |
| sodium (4Z)-4-[(1-hydroxynaphthalen-2-yl)hydrazinylidene]-7-nitro -3-oxo-naphthalene-1-sulfonate |
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| Identifiers | |
| CAS number | 1787-61-7 |
| PubChem | 5351620 |
| Chemical data | |
| Formula | C20H12N3O7SNa |
| Mol. weight | 461.381 g/mol |
| SMILES | C1=CC=C2C(=C1)C=CC(=C2O)NN=C3C4=C(C=C (C=C4)[N+](=O)[O-])C(=CC3=O)S(=O)(=O)[O-].[Na+] |
| Complete data | |
Eriochrome Black T is a complexometric indicator that is part of the complexometric titrations, eg. in the water hardness determination process. It is an azo dye.
In its protonated form, Eriochrome Black T is blue and it turns red when it forms complex with calcium, magnesium, or other metal ions. When used as an indicator in an EDTA titration the characteristic blue end-point is reached when sufficient EDTA is added and metal ions form complexes with the EDTA instead of the eriochrome.
Its chemical formula can be written as HOC10H6N=NC10H4(OH)(NO2)SO3Na.
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