Eriochrome Black T

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Eriochrome Black T
Eriochrome Black T sample solutions.jpg
Eriochrome Black T sample and as solution. From left to right: dissolved in distilled water, in distilled water with NH3, in tap water, in tap water with NH3 and in tap water with NH3 end point titrated with EDTA.
Names
IUPAC name
Sodium (4Z)-4-[(1-hydroxynaphthalen-2-yl)hydrazinylidene]-7-nitro-3-oxonaphthalene-1-sulfonate
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
Fast Chrome Black T
Hispacrom Black T
Mordant Black 11
Sodium 4-[2-(1-hydroxynaphthalen-2-yl)hydrazin-1-ylidene]-7-nitro-3-oxonaphthalene-1-sulfonate
Solochrome Black T
Properties
C20H12N3O7SNa
Molar mass 461.381 g/mol
Appearance Dark black/purple brown solid
Odor Odorless
5 g/100 ml (at 20 °C)[1]
Solubility Almost insoluble in ethanol
Insoluble in acetone, butanol, chloroform, dichloromethane, ethylene glycol, glycerol, hexane, isobutanol, isopropanol, propylene glycol, toluene, xylene
Vapor pressure ~0 mmHg
Acidity (pKa) 6.2; 11.55
Hazards
Safety data sheet Sigma-Aldrich
Lethal dose or concentration (LD, LC):
17,590 mg/kg (oral, rat)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Eriochrome Black T (EBT) is an azo dye used as complexometric indicator in complexometric titrations, most common in determining water hardness.

Properties

Chemical

Buffered aqueous solutions of EBT turn red when calcium is added.

Physical

Eriochrome Black T is a dark purple-brown/black solid, soluble in water, but insoluble in most organic solvents. While it doesn't appear to dissolve in ethanol, EBT will turn it red if added.

In its protonated form, Eriochrome Black T is blue, but turns red when it forms a complex with calcium, magnesium, or other metal ions.

Availability

Can be purchased from chemical suppliers or online.

Preparation

Best to buy it than synthesize.

Projects

  • Determine water hardness
  • Detect rare-earth metals

Handling

Safety

Eriochrome Black T is irritant, but there doesn't appear to be very toxic or carcinogenic. Ingestion may lead to diarrhoea.

Storage

In closed amber bottles, away from light and corrosive vapors.

Disposal

Can be poured down the drain.

References

  1. http://www.chemicals.co.uk/uploads/documents/ERIOCHROME-BLACK-T-MSDS.pdf

Relevant Sciencemadness threads