Phenol blue mixtures

Figure 7. Transition energy of phenol blue in binary mixtures of acetone and CXDj at 35 C ( 80 bar, A 200 bar [ref. 36]).

Another attempt to relate the results from the use of a solvatochromic probe (Phenol Blue (66)) to the inherent properties of solvent mixtures was made by Phillips and Brennecke122. They obtained the interaction energies (required for the application of the non-random two-liquid (NRTL) approach) of 66 with each of the solvent components from its solubility in the neat solvent. The mixtures studied contained cyclohexane as one component and acetone, triethylamine, ethyl butyrate, cyclohexanone, toluene and acetophenone as the other. Then the local compositions deduced from the solvatochromism of 66 were compared with those calculated by the NRTL equation and reasonable agreement was found. 

Dissolve an amount of powdered tablets equivalent to about one-quarter of a tablet in a mixture of equal volumes of acetate buffer solution, pH 3 7 (see p. 116) and water and dilute to 200 ml with the mixture in a graduated flask. Transfer a 10-ml aliquot of this solution to a dry beaker, add, with swirling, 15 ml of 0 01 M sodium tetraphenylboron, allow to stand for five minutes and filter through a dry, sintered-glass crucible. Pipette 20 ml of the filtrate into a flask, add 0 50 ml of bromo-phenol blue indicator and titrate the excess sodium tetraphenylboron with 0 005M cetylpyridinium chloride to the blue end-point. Repeat the operation omitting the sample. 1 ml O OIM sodium tetraphenylboron = 0 0003910 g potassium. 

P-Hydroxy-a-naphthaldehyde, Equip a 1 litre three-necked flask with a separatory funnel, a mercury-sealed mechanical stirrer, and a long (double surface) reflux condenser. Place 50 g. of p-naphthol and 150 ml. of rectified spirit in the flask, start the stirrer, and rapidly add a solution of 100 g. of sodium hydroxide in 210 ml. of water. Heat the resulting solution to 70-80° on a water bath, and place 62 g. (42 ml.) of pure chloroform in the separatory funnel. Introduce the chloroform dropwise until reaction commences (indicated by the formation of a deep blue colour), remove the water bath, and continue the addition of the chloroform at such a rate that the mixture refluxes gently (about 1 5 hours). The sodium salt of the phenolic aldehyde separates near the end of the addition. Continue the stirring for a further 1 hour. Distil off the excess of chloroform and alcohol on a water bath use the apparatus shown in Fig. II, 41, 1, but retain the stirrer in the central aperture. Treat the residue, with stirring, dropwise with concentrated hydrochloric acid until... 

Pipette 25 mL of an aluminium ion solution (approximately 0.01 M) into a conical flask and from a burette add a slight excess of 0.01 M EDTA solution adjust the pH to between 7 and 8 by the addition of ammonia solution (test drops on phenol red paper or use a pH meter). Boil the solution for a few minutes to ensure complete complexation of the aluminium cool to room temperature and adjust the pH to 7-8. Add 50 mg of solochrome black/potassium nitrate mixture [see Section 10.50(C)] and titrate rapidly with standard 0.01 M zinc sulphate solution until the colour changes from blue to wine red. 

For a number of years, phenolic substances were dosed by colorimetric techniques, based on redox reactions usually known as Folin Ciocalteau methods, even if a number of adjustments were developed to fit different matrix characteristics. The Folin Cioalteau reagent is a mixture of phosphomolybdic and phosphotingstic acids, with molybdenum in the 6+ oxidation state and, when the reaction takes place, it is reduced to form a complex called molybdenum blue and tungsten blue. In this complex, the mean oxidation state is between 5 and 6 and the formed complex is blue so it can be read spectrophotometrically at 750 nm. 

In the synthesis of the heterocyclic dye 28 [83156-84-7] [49], 2-amino-4-chloro-phenol is diazotized. A solution of 1 -mcthylimidazo 1,5 pyridinc in 10% HC1 is then added dropwise to the diazotation mixture while maintaining the pH at 4—5 with sodium acetate solution. The resulting azo dye is isolated by vacuum filtration and consists of a brown powder that dyes nickel-modified polypropylene fibers in greenish blue shades. 

Assay Determine as directed under Phenols, Appendix VI. Angular Rotation Determine as directed under Optical (Specific) Rotation, Appendix IIB, using a 100-mm tube. Phenols Shake 1 mL of sample with 20 mL of hot water. The water shows no more than a scarcely perceptible acid reaction with blue litmus paper. Cool the mixture, pass the water layer through a wetted filter, and treat the clear filtrate with 1 drop of ferric chloride TS. The mixture has only a transient gray-green color, but not a blue or violet color. 

Total wine polyphenols are oxidised by the Folin-Ciocalteu reagent - composed of a mixture of phosphotungstic and phosphomolybdic acids which are reduced by the oxidation of the phenols, forming a mixture of blue oxides of tungsten and molybdenum. The blue coloration has an absorption maximum at approximately 750 nm, the intensity of which is proportional to the level of phenolic compounds present in the wine. The sequential analyser method is a direct automation of the manual method and results are expressed as a unit-less index. 

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