Mordant black 11 indicator

Procedure Weigh accurately about 0.3 g of magnesium sulphate heptahydrate and dissolve in 50 ml of DW. Add to it 10 ml of strong ammonia-ammonium chloride solution, and titrate with 0.05 M disodium ethylenediaminetetracetate employing 0.1 g of mordant black II mixture as indicator, until the pink colour is discharged from the blue. Each ml of 0.05 M disodium ethylenediaminetetracetate is equivalent to 0.00602 g of MgS04. 

C.I. Mordant Black 11 is also used as an indicator in the complexometric titration of various bivalent metals with which it forms complexes [8],... 

Analytical Reagents. Various chelators give specific color changes on combining with different metal salts, such as vanadium, iron, cobalt, nickel, copper, and palladium salts and thus identify the corresponding metal ions [74], Other chelators, such as C.I. Mordant Black 11 (Eriochrome Black T) (2 see Section 3.11.1), are employed as indicators for complexometric titrations. 

The indicators used in compleximetric titrations are usually themselves complexing agents, which form weak complexes with the metal ion when added initially As the edetate solution is titrated, the weak complex is displaced by the stronger edetate complex to reveal the free colour of the indicator. The most commonly used indicator is known by the sinister name of mordant black. This indicator forms wine-red complexes with metal ions, but changes to a dark blue colour at the end point when the edetate has displaced all of the metal ions from the indicator complex. 

The indicator used in the test, mordant black 11 triturate R, is a dry dilution of Eriochrome Black (Figure 6.7.3), which is one of the most widely used metallochromic indicators. The acid form of the indicator is red, changes to blue at about pH 6, and to orange at pH 12. Only the blue is used as a metallochrome indicator, and it changes to red in the presence of metals. 

Decolorization of aqueous solutions of dyes used in the textile industry may be accomplished via the use of ozone. Y.-C. Hsu, J.-T. Chen, H.-C. Yang, and J.-H. Chen [AIChE J 47, 169-176 (2001)] investigated the kinetics of the oxidation of C.I. Mordant Black and other dyes in a well-agitated reactor to which a gas containing ozone was fed continnonsly. Initially, decolorization occurs rapidly, but as the process continues, colored intermediates are formed. These intermediates are more recalcitrant to oxidation, but are destroyed as ozonation proceeds. These authors indicate that the concentration of dissolved ozone remains substantially constant so that the kinetics of this process can be treated as involving two consecutive pseudo first-order reactions ... 

Eriochrome Blue Black R (Palatine Chrome Black 6BN, Mordant Black 17, 3-hydroxy-4-(2-hydroxy-l-naphthylazo)naphthalene-l-sulfonic acid Na salt] [2538-85-4] M 416.4, pK 7.0, pKf 13.5. Free it from metallic impurities by three precipitations from aqueous solution by addition of HCl. The precipitated dye is dried at 60° imder vacuum and converted into the Na salt with the calculated amoimt of alkali. It is an indicator in the complexometry of Al, Fe and Zr. [Beilstein 16 H 297,16 IV 428.]... 

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