1787-61-7 Usage
Description
Eriochrome Black T is a complexometric indicator that forms complexes with metal ions, particularly calcium and magnesium. It is a dark brown powder that is soluble in water and ethanol, and it exhibits different colors in various chemical environments.
Uses
Used in Analytical Chemistry:
Eriochrome Black T is used as an indicator in complexometric titrations for the determination of total calcium and magnesium content in water. It forms complexes with Ca2+ and Mg2+ ions, but it binds more strongly to Mg2+ ions.
Used in Detection of Rare Earth Metals:
Eriochrome Black T is used in the detection of rare earth metals due to its ability to form complexes with metal ions.
Used in Dyeing and Printing Industry:
Eriochrome Black T is used for dyeing and printing of wool fabric, dyeing of silk and nylon, and in leather dyeing. It can dye wool from an acid bath reddish-black, which can be converted to blue-black by afterchroming.
Used in Pharmaceutical Industry:
Eriochrome Black T can be used in the spectrophotometric determination of diphenhydramine hydrochloride in pharmaceutical preparations.
Used in Water Analysis:
Eriochrome Black T has been used to determine the concentration of Ca2+ using complexometric titration method.
Properties and Applications:
Eriochrome Black T is a blue-black dye that is soluble in water for bordeaux red to jam red, moderately soluble in ethanol for brown light magenta, and slightly soluble in acetone. Its dye aqueous solution turns sauce red when it joins concentrated hydrochloric acid and brown light magenta when it joins strong caustic. It is mainly used for dyeing various kinds of wool fabric and also for silk, nylon, and various fiber blended fabric dyeing. It can be used for direct printing of wool fabric after chrome pretreatment. It can also be used as an indicator and for biological and fur dyeing.
Standard:
Eriochrome Black T has the following fastness ratings according to ISO and AATCC standards:
| Property | ISO | AATCC |
|----------------|------|--------|
| Ironing Fastness | 4-5 | 4-5 |
| Light Fastness | 7 | 7 |
| Fulling | 5 | 4-5 |
| Persperation Fastness | 5 | N/A |
| Soaping | 5 | 5 |
| Water | 5 | 5 |
| Alkali | 5 | 5 |
| Acid | 5 | 5 |
Chemical Properties:
Eriochrome Black T is a black powder that exhibits different colors in various chemical environments, such as skipper in concentrated sulfuric acid, pale red light brown in diluted sulfuric acid, and orange in concentrated nitric acid.
Preparation
4-Amino-3-hydroxy-7-nitronaphthalene-1-sulfonic acid diazotization, and Naphthalen-1-ol?coupling.
Standard
Ironing Fastness
Alkali
Acid
ISO
4-5
AATCC
4-5
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.]
Check Digit Verification of cas no
The CAS Registry Mumber 1787-61-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,7,8 and 7 respectively; the second part has 2 digits, 6 and 1 respectively.
Calculate Digit Verification of CAS Registry Number 1787-61:
(6*1)+(5*7)+(4*8)+(3*7)+(2*6)+(1*1)=107
107 % 10 = 7
So 1787-61-7 is a valid CAS Registry Number.
InChI:InChI=1/C20H13N3O7S.Na/c24-17-10-18(31(28,29)30)15-9-12(23(26)27)6-7-14(15)19(17)22-21-16-8-5-11-3-1-2-4-13(11)20(16)25;/h1-10,24-25H,(H,28,29,30);/q;+1/p-1
