Chemical Properties
black powder
Uses
Eriochrome
? Black T has been used to determine the concentration of Ca
2+ using complexometric titration method.
Uses
Eriochrome black T is used as an indicator in analytical chemistry. It is also used in the detection of rare earth metals. It finds application in dyeing and printing of wool fabric, dyeing of silk and nylon as well as in leather dyeing. It can be used in the spectrophotometric determination of diphenhydramine hydrochloride in pharmaceutical preparations. As a complexometric indicator, it is useful in the determination of hardness of water.
Uses
To dye wool from an acid bath reddish-black, which can be converted to blue-black by afterchroming. As indicator in the determination of the total calcium and magnesium content of water.
Preparation
4-Amino-3-hydroxy-7-nitronaphthalene-1-sulfonic acid diazotization, and Naphthalen-1-ol?coupling.
General Description
Eriochrome
? Black T is used as an indicator for complexometric titrations. It functions as an acid-base indicator. Eriochrome
? Black T forms complex with Ca
2+ and Mg
2+, but it binds more strongly to Mg
2+ ions.
Properties and Applications
blue black. Dark brown powder. Soluble in water for bordeaux red to jam red, moderate soluble in ethanol for brown light magenta, slightly soluble in Acetone. Dye in concentrated sulfuric acid for skipper, dilution to pale red light brown; In concentrated nitric acid to orange. Dye aqueous solution to join concentrated hydrochloric acid for sauce red; Join strong caustic into brown light magenta. Mainly used for all kinds of wool fabric dyeing, also used for silk, nylon and wool and a variety of fiber blended fabric dyeing, can be in chrome pretreatment of wool fabric direct printing. Is tasted can be used for indicator, also can be used for biological and fur dyeing.
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Standard
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Ironing Fastness
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Light Fastness
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Fulling
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Persperation Fastness
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Soaping
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Water
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Alkali
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Acid
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ISO
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4-5
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7
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5
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5
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5
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5
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5
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AATCC
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4-5
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7
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4-5
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5
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5
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5
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Purification Methods
The sodium salt (200g) is converted to the free acid by stirring with 500mL of 1.5M HCl, and, after several minutes, the slurry is filtered on a sintered-glass funnel. The process is repeated and the material is air dried after washing with acid. It is then extracted with *benzene for 12hours in a Soxhlet extractor, the *benzene solution is evaporated and the residue is air dried. A further desalting with 1.5M HCl (1L) is followed by crystallisation from dimethylformamide (in which it is very soluble) by forming a saturated solution at the boiling point, and allowing to cool slowly. The crystalline dimethylammonium salt so obtained is washed with *benzene and treated repeatedly with dilute HCl to give the insoluble free acid which, after air drying, is dissolved in alcohol, filtered and evaporated. The final material is air dried, then dried in a vacuum desiccator over Mg(ClO4)2. The purified acid is converted to the dimethylammonium salt with Me2NH. [Diehl & Lindstrom, Anal Chem 31 414 1959]. It is an indicator in the complexometry of alkaline earth metals. [Beilstein 16 IV 429.]
