Methyl Red-Methylene Blue

Grote s reagent is useful for the determination of 2-aminothiazoie in blood and wine (145), This thiazole may be extracted from its aqueous solution and then titrated in nonaqueous medium (MeOH) with HCIO4 in the presence of a mixed methyl red-methylene blue indicator (146). 

Methyl red-methylene blue solution - dissolve 1.25 g of methyl red and 0.825 g of methylene blue in 1 I of ethanol. 

Procedure. Steam out the distillation unit for 20 min. Pipette 5 ml of ammo-nium-N standard solution into the unit. Add 7 ml of sodium hydroxide solution and steam distil the liberated ammonia into 5 ml of boric acid solution. Collect 20 ml of distillate. Add 2-3 drops of methyl red-methylene blue solution and titrate with 0.01 M sulphuric acid until the green colour changes to... 

This method is based on the titration of basic ammonia with standard sulfuric acid using methyl red-methylene blue indicator to pale lavender end point. Distill 100 mL sample into 50 mL boric acid mixed indicator solution. Titrate ammonia in this distillate solution with standard H2S04 (0.02 N) until the color turns to pale lavender. Perform a blank titration using distillate obtained from reagent grade water under similar conditions. Calculate the concentration of NH3-N in the sample as follows ... 

Methyl red-methylene blue indicator solution Dissolve 200 mg methyl red in 100 mL 95% ethanol. Separately dissolve 100 mg methylene blue in 50 mL 95% ethanol. Mix both these solutions. 

Boric acid-indicator solution Dissolve 20 g boric acid in distilled water. Add 10 mL methyl red-methylene blue indicator solution. Dilute to 1 L. 

Alternatively, standardize 0.1 A commercially available H2S04 or the acid of same strength prepared above against 0.1 N Na2C03 (5.300 g anhydrous Na2C03 dissolved in distilled water and diluted to 1 L) using methyl red indicator (the color changes from pink to yellow at the end point) or methyl red-methylene blue indicator. 

Assay Dissolve about 0.4 g of sample, previously dried at 105° for 4 h and accurately weighed, in about 300 mL of water contained in a 500-mL round-bottom flask. Add 3 g of a powder of Devarda s alloy and 15 mL of a 40% sodium hydroxide solution, and connect with a spray-preventing device and condenser to the flask. Allow to stand for 2 h. Transfer 50 mL of 0.1 N sulfuric acid into a receptacle, use this to collect 250 mL of the distillate, and titrate the excess sulfuric acid with 0.1 IV sodium hydroxide, using 3 drops of methyl red-methylene blue TS as the indicator. Perform a blank determination (see General Provisions), and make any necessary correction. Each milliliter of 0.1 A sulfuric acid is equivalent to 10.11 mg of KNO3. 

Heat over a free flame or an electric heater until the solution has attained a clear blue color and the walls of the flask are free from carbonized material. Cautiously add 20 mL of water, cool, then add through a funnel 30 mL of a 2 5 solution of sodium hydroxide, and rinse the funnel with 10 mL of water. Connect the flask to a steam distillation apparatus, and immediately begin the distillation with steam. Collect the distillate in 15 mL of a 1 25 solution of boric acid to which has been added 3 drops of methyl red-methylene blue TS and enough water to cover the end of the condensing tube. Continue passing the steam until 80 to 100 mL of distillate has been collected, then remove the absorption flask, rinse the end of the condenser tube with a small quantity of water, and titrate with 0.01 N sulfuric acid. Each milliliter of 0.01 N acid is equivalent to 140 p.g of nitrogen. 

Starch Variety Fuchsin Acidic Basic Methyl Violet Methylene Blue Congo Red Eosin... 

Mercuric iodide, red N.F. Methyl alcohol Methylene blue N.F... 

Phosphomolybdate forms strong ion association complexes with basic dyes at low pH. For example, the sensitivity of a method based on spectrophotometric determination of the 12-MPA-malachite Green complex [84,85] was approximately 30 times that of a reduced phosphomolybdate determination. Other dyes used for this purpose include Saffranin, brilliant green, Fuchsine red, methylene blue, methyl violet, and Rhodamine B [5]. Surfactants such as polyvinyl alcohol are frequently used to avoid precipitation of the ion association complex. 

The decolorization potential of immobilized P. chrysosporium MTCC 787 for azo dyes Acid Orange, Acid Red 114, triphenylmethane dye Methyl Violet, diazoic dye Congo Red, vat dye Vat Magenta, thiazine dye Methylene Blue, and anthraqui-none Acid Green was demonstrated by Radha et al. [53]. Decolorization experiments were carried out with immobilized calcium alginate (Ca-ALG) beads of different sizes (2-6 mm). 

Mixed indicator - dissolve 0.3 g methyl red and 0.2 g methylene blue in 250 ml ethanol. 

A) Mixed indicator. Dissolve 0.10g of methyl red and 0.050g of methylene blue in 100ml... 

Of the blue lakes, mention may be made of those of indigo and logwood, alizarin blue, basic triphenylmethane blues and methylene blue. Violet lakes are made with methyl violet and the like or with mixtures of blues and reds. 

Fig. 4 Countercurrent separation of various samples by the coil planet centrifuge, (a) Separation of basic dyes with an organic/aqueous two-phase solvent system. M.G. methyl green M.B. methylene blue N.R. neutral red F.B. basic fuchsin. (From Ref. [3].) Solvent system consisted of isoamyl alcohol/ethanol/acetic acid/water (4 2 1 5, v/v).

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