Murexide Indicator Preparation

Murexide Indicator Preparation Add 400 mg of murexide to 40 g of powdered potassium sulfate (K2S04), and grind in a glass mortar to a homogeneous mixture. Alternatively, use tablets containing 0.4 mg of murexide admixed with potassium sulfate or potassium chloride, available commercially. 

Procedure. Prepare the murexide indicator as described in Section 10.57(a), and an ammonium chloride solution (1M) by dissolving 26.75 g ammonium chloride in de-ionised water in a 500 mL graduated flask. 

Pipette 25.0 mL of the bromide ion solution (0.01-0.02M) into a 400 mL beaker, add excess of dilute silver nitrate solution, filter off the precipitated silver bromide on a sintered glass filtering crucible, and wash it with cold water. Dissolve the precipitate in a warm solution prepared from 15 mL of concentrated ammonia solution, 15 mL of 1M ammonium chloride, and 0.3 g of potassium tetracyanonickelate. Dilute to 100-200 mL, add three drops of murexide indicator, and titrate with standard EDTA (0.01 M) (slowly near the end point) until the colour changes from yellow to violet. 

Aqueous solutions of murexide are unstable and must be prepared each day. The indicator solution may be prepared by suspending 0.5 g of the powdered dyestuff in water, shaking thoroughly, and allowing the undissolved portion to... 

Procedure (a). Prepare the indicator by grinding 0.1 g murexide with 10 g of potassium nitrate use about 50 mg of the mixture for each titration. 

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