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 = 1787-61-7
PubChem = 5351620
SMILES = C1=CC=C2C(=C1)C=CC(=C2O)N/N=
C3/C4=C(C=C(C=C4) [N+] (=O) [O-] )
C(=CC3=O)S(=O)(=O) [O-] . [Na+]
Section2 = Chembox Properties
Formula = C₂₀H₁₂N₃O₇SNa
MolarMass = 461.381 g/mol
Appearance = Dark red/brown powder
Density =
MeltingPt =
BoilingPt =
Solubility =

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. It turns red when it forms a complex with calcium, magnesium, or other metal ions. Its chemical formula can be written as HOC₁₀H₆N=NC₁₀H₄(OH)(NO₂)SO₃Na.

Applications

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.

Eriochrome Black T has also been used to detect the presence of rare earth metals. [cite journal | author = Dubenskaya, L. O. and Levitskaya, G. D.| title = Use of eriochrome black T for the polarographic determination of rare-earth metals | journal = Journal of Analytical Chemistry | ISSN = 1061-9348 | year = 1999 | volume = 54 | pages = 655–657 | issue = 7 | url = http://cat.inist.fr/?aModele=afficheN&cpsidt=1896853]

References

External links

* [http://www.jtbaker.com/msds/englishhtml/e1300.htm J.T. Baker MSDS]
* [http://chemmovies.unl.edu/chemistry/smallscale/SS051c.html Describes a procedure for determining the hardness of water using EDTA with Eriochrome indicator]