Cresol Red-Thymol Blue

Methyl violet Cresol red Thymol blue Methyl orange Bromcresol green Methyl red Bromthymol blue Phenolphthalein Thymolphthalein Clayton yellow... 

Cresol Red-Thymol Blue TS, 851 Cresol Red TS, 851 o-Cresolsulfonphthalein, 860 p-Cresyl Acetate, 474, 568, 684, (S 1)66 p-Cresyl Isobutyrate, 558 p-Cresyl Methyl Ether, 524 Criteria for Food Chemicals Codex Grade, xx... 

Indicator Bromphenol blue Methyl orange Methyl red Bromcresol purple Bromthymol blue Phenol red Cresol red Thymol blue Phenolphthalein Thymolphthalein... 

Ammonium Industrial effluents Pervaporation UV-Vis 0.1 mg L-1 Flow injection system mixed cresol red/thymol blue acid—base indicator solution as the acceptor stream results unaffected by surfactants, other organics and suspended solids [273]... 

Clark-Lubs indicators. Phenol red, cresol red, bromophenol blue, bromocresol purple, thymol blue, bromthymol blue, and methyl red. 

Dr. Klotz has found furthermore that the unbrominated sulfonephthaleins such as phenol red, cresol purple, thymol blue, etc., possess a marked tendency to form molecular compounds with their corresponding phenols. Apparently the stability of the indicator solutions depends upon this phenol content. 

Phenol red Bromthymol blue Rosolic acid Bromcresol purple Alizarine Bromcresol blue Bromphenol blue m-Cresol purple Thymol blue Methyl red Methyl orange Dimethyl yellow... 

For bromthymol blue, J. T. Saunders finds, by comparison with Sorensen buffers, a salt error of — 0.19 when the medium is 0.6 N with respect to NaCl. The error becomes + 0.20 at a total electrolyte concentration of 0.003 N. The errors which Saunders finds for thymol blue, phenol red, cresol red, bromthymol blue, and bromcresol purple in salt concentrations below 0.1 N are in accord with the measurements of the author (cf. above pages 340 to 342). 

The acidities increase in thionyl chloride xylenol blue < cresol red < bromo-thymol blue < bromophenol red < bromophenol blue and in acetyl chloride cresol red < xylenol blue < bromothymol blue < bromophenol red < bromophenol blue. 

Several indicators have been suggested for the determination of pH, but the most suitable are the sulphonphthalein indicators such as m-cresol purple, thymol blue and cresol red. They all exist in three forms, with the chemical equilibria following reactions (7-17) and (7-18)... 

Sulphonphthaleins. These indicators are usually supplied in the acid form. They are rendered water-soluble by adding sufficient sodium hydroxide to neutralise the sulphonic acid group. One gram of the indicator is triturated in a clean glass mortar with the appropriate quantity of 0.1 M sodium hydroxide solution, and then diluted with water to 1 L. The following volumes of 0.1 M sodium hydroxide are required for 1 g of the indicators bromophenol blue, 15.0 mL bromocresol green, 14.4 mL bromocresol purple, 18.6 mL chlorophenol red, 23.6 mL bromothymol blue, 16.0 mL phenol red, 28.4 mL thymol blue, 21.5 mL cresol red, 26.2 mL metacresol purple, 26.2 mL. 

Procedure B. The experimental details for the preparation of the initial solution are similar to those given under Procedure A. Titrate 25 or 50 mL of the cold solution with standard 0.1M hydrochloric acid and methyl orange, methyl orange-indigo carmine, or bromophenol blue as indicator. Titrate another 25 or 50 mL of the cold solution, diluted with an equal volume of water, slowly with the standard acid using phenolphthalein or, better, the thymol-blue cresol red mixed indicator in the latter case, the colour at the end point is rose. Calculate the result as described in the Discussion above. 

In the second procedure a portion of the cold solution is slowly titrated with standard 0.1M hydrochloric acid, using phenolphthalein, or better, the thymol blue-cresol red mixed indicator. This (say, YmL) corresponds to half the carbonate (compare Section 10.32) ... 

Mixed indicator. This should be prepared from 1 part of 0.1 per cent neutralised aqueous cresol red and 3 parts of 0.1 per cent neutralised thymol blue. 

Figure 9. Normalized spectra of the base form of four indicators (1 - phenol red, 2 - bromo-cresol purple, 3 - thymol blue, and 4 -bromocresol green).

Cresol red Crystal Violet Malachite Green Methanil Yellow Thymol Blue Orange IV -2,4-Dinitrophenol -Erythrosin, Na2 salt -Dimethyl Yellow Cl 11020 Bromophenol Blue Congo Red Cl 22120 Methyl Orange Bromocresol Green Alizarin Red S Cl 42750 Methyl Red Cl 13020 -Bromocresol Purple Chlorophenol Red p-Nitrophenol Alizarin Bromothymol Blue Brillant Yellow Phenol Red Neutral Red Cl 50040 -m-NItrophenol -Cresol Red Metacresol Purple Phenolphthalein -Thymolphthalein -P-Naphthyl Violet Alizarin Yellow R 2,4,6-T rinitrotoluene... 

Methylthymol blue and methylxylenol blue, prepared by the Mannich reaction from thymol-sulfonphthalein and p- xylenol blue respectively, have been intensively studied and resemble xylenol orange in many respects. If only one chelating group is introduced into cresol red, semi-xylenol orange results which is a common contaminant in XO and proves to be a more sensitive reagent for zirconium. 

The titrant is a standardized NaOH solution of approximately 0.5 N, and the indicator is a 0.1 wt% 1 1 mix of cresol red and thymol blue in methanol. The color change will be from a light yellow to violet for the end point. 

Certain of these indicators will again be considered by way of illustration of desirable properties. Methyl violet is green in 0.05 N hydrochloric acid, but the color fades appreciably even in fifteen minutes and disappears entirely after a longer interval. Evidently methyl violet can not be recommended for pH determinations, and cresol red or thymol blue must be used in its stead. In order to obtain stable acid solutions (red) of the latter indicators, no more than 0.1 c.c. of 0.1% solution should be used... 

Bromcresol green, Chlorphenol red. Methyl red, Bromcresol purple, Bromthymol blue, Phenol red, Neutral red, Cresol red, and Thymol blue (alkaline region). Acid solution in very dilute acetic acid (about 0.1 N) alkaline solution in dilute sodium carbonate (about 0.01 N-0.1 N). 

The author has prepared papers from a mixture of 0.1% cresol red with 0.25% thymol blue and from 0.1% cresol red with 0.1% thymol blue. The first paper has an indistinct bluish gray color from 7.4 to 8.4. The color is rose at a pH of 8.4 and red-violet at 8.6. The second paper is definitely rose at a pH of 7.6. Neither transformation is very distinct. 

Alizarin Bromocresol green Bromothymol blue Carminic acid Chlorophenol red m-Cresol purple Curcumin 2,4-Dintrophenol Resorcine bue Thymol blue indicator, alcohol solution p-Nitrophenol... 

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