Dimethyl yellow

The mixed indicator, bromocresol green-dimethyl yellow, may be used with advantage. The indicator consists of 4 parts of a 0.2 per cent ethanolic solution of bromocresol green and 1 part of a 0.2 per cent ethanolic solution of dimethyl yellow about 8 drops are used for 100 mL of solution. The colour change is from blue to greenish yellow at pH = 4.0 — 4.1 the colour is yellow at pH = 3.9. 

Two experimental systems have been used to illustrate the theory for two-step surface electrode mechanism. O Dea et al. [90] studied the reduction of Dimethyl Yellow (4-(dimethylamino)azobenzene) adsorbed on a mercury electrode using the theory for two-step surface process in which the second redox step is totally irreversible. The thermodynamic and kinetic parameters have been derived from a pool of 11 experimental voltammograms with the aid of COOL algorithm for nonlinear least-squares analysis. In Britton-Robinson buffer at pH 6.0 and for a surface concentration of 1.73 X 10 molcm, the parameters of the two-step reduction of Dimethyl Yellow are iff = —0.397 0.001 V vs. SCE, Oc,i = 0.43 0.02, A sur,i =... 

Dimethyl yellow, see p-Dimethylaminoazobenzene Dimethyl yellow analar, see p-Dimethylaminoazobenzene Dimethyl yellow A.A-dimethylaniline, see p-Dimethyl-aminoazobenzene... 

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... 

Colour Tests. To 5 ml of a 0.1% solution add 1 ml of dilute sulphuric acid, 10 ml of chloroform, and 0.2 ml of dimethyl yellow solution, and shake—the chloroform layer is coloured red. Add 50 mg of cetrimide and shake—the colour of the chloroform layer changes to yellow. 

Dimethyl Yellow Solution a 0 2% solution of dimethyl yellow m ethanol (90%)... 

The indicator shown is p-dimethylaminoazobenzene (also known as dimethyl yellow ). Its basic color is yellow, and its acid color is red. Its pKa is +3.3. The red color of the acid form... 

Synonyms 4-Dimethylaminoazobenzene (preferred name) DAB DMAB 4-Dimethylaminoazobenzol 4-Dimetbylaminopbenylazobenzene Dimethyl yellow Brilliant fast oil yellow Fast yellow Fat yellow Chemical Formula C14H15N3 Chemical Structure ... 

Dimethyl yellow Dimethylamino-azo-benzene 2.9-4.1 red - yellow Sorensen... 

The azo indicators, such as dimethylaminoazobenzene (butter yellow, methyl or dimethyl yellow), are usually but slightly soluble in water and therefore unsuited for the quantitative determination of pH. If several drops of a 0.1% alcoholic... 

Dimethylaminoazohenzene (also called dimethyl yellow, methyl yellow, or butter yellow),... 

Part dimethyl yellow 0.1% in alcohol 1 methylene blue 0.1%... 

Transformation range at pH < 7, alkali sensitive indicator. Examples dimethyl yellow, methyl red. 

Dimethyl yellow will show its yellow alkaline color. 

A second difficulty enters when one of the two forms is insoluble. This must be guarded against, especially in the colorimetric determination of hydrogen ion concentration. The azo dye dimethylamino-azo-benzene (dimethyl yellow) will serve to illustrate this difficulty. Dimethyl yellow is a weak base wdth a pBOH = 10. It is very insoluble and shows a yellow color. The red colored salt, on the other hand, is much more soluble in water. In the equation... 

Dimethyl yellow. The product employed in preparing the saturated solutions was purified by digesting several times in fresh water. The following saturated solutions were prepared ... 

A third solution was prepared by adding an alcoholic solution to water and letting it stand for several days. The supernatant liquids of all three solutions were carefully siphoned off, and compared in Nessler tubes with dimethyl yellow solutions of known concentrations. The solubility of dimethyl yellow was found to be 5 mg. per liter. Therefore, if the hydrogen ion concentration of 10 c.c. of sample is to be determined coiorimet-rically using a 0.1% alcoholic dimethyl yellow solution, not more than 0.05 c.c. (about one drop) should be used. 

Were the dissociation constant of dimethyl yellow to remain unchanged by heating, then at the boiling point of water this indicator should undergo transformation at two pH units less... 

Volume % Alcohol S R FOR Methyl Orange S R. FOR Dimethyl Yellow S R. FOR Tropeolin 00 S R. for Methyl Violet... 

At a given alcohol concentration, a maximum or minimum constant S.R. value occurs, as in the case of tropeolin 0, methyl orange, dimethyl yellow, and tropeolin 00. The maximum is extremely pronounced for azo indicators. The sensitivity of methyl orange towards acid rises strikingly between 95% and 96% alcohol. This property furnishes a simple means of determining the water content of alcohol (see 3 of this chapter). 

We see from the experiments which have been described and from the figures that tropeolin 0, phenolphthalein, thymolphthal-ein, thymol blue, and bromphenol blue become more sensitive towards strong acids when present in alcohol-water mixtures. Nitramine, curcumin, methyl orange, dimethyl yellow, tropeolin 00, and methyl violet, on the other hand, become more alkali sensitive. 

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

The transformation of dimethyl yellow and related substances is governed by the following equilibrium ... 

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