Transition Intervals

Figure 7.5 gives the transition intervals and colors of some selected pH indicators. Because fhe application of dieses indicators in fhe context of fhe biochemical protocol is not volumetric analysis, fhe concentration of stock solution is mosdy 0.1% (w/v) in efhanol or propanol, and fhe final dilution is 100-fold lower. 

Fig. 7.5. Transition interval of pH indicators. A amber, b blue, c colorless, g green, o orange, p/c pink,p purple, r red, vviolet,y yellow...

Fig. lib. Change of the thermal expansion coefficient /3th at the glass transition interval (b)... 

Indicator Mixtures (Two-Component). An important criterion for the selection of an indicator is an transition interval which is clear, visually well detectable, and as sharp as possible. Ideally, the acidic and the alkaline forms should possess complementary colors, for example, red and green. Unfortunately, no individual indicator fulfills all these requirements. Furthermore, the mixture of colors in the transition range often deteriorates the quality of color change. 

The jS-cell model displays chaotic dynamics in the transition intervals between periodic spiking and bursting and between the main states of periodic bursting. A careful description of the bifurcation diagram involves a variety of different transitions, including Hopf and saddle-node bifurcations, period-doubling bifurcations, transitions to inter-mittency, and homoclinic bifurcations. 

In some cases dissolution without a gel layer is found, especially at low temperatures. It appears that dissolution by stress cracking is the cause of this phenomenon. Cracks are observed which run into the polymer matrix and combine to form small blocks of the polymer, which leave the surface in a kind of eruption process. Large amounts of stored stress energy, frozen in the glass transition interval and concentrated along the wider... 

Bromocresol Green (Bromocresol Blue Tetrabromo-m-cre-solsulfonphthalein) A white or pale buff-colored powder slightly soluble in water soluble in alcohol and in solutions of alkali hydroxides. Transition interval from pH 3.8 (yellow) to 5.4 (blue). 

Pink crystals, soluble in alcohol. Insoluble in water soluble in solutions of alkali hydroxides. Transition interval from pH... 

Ethoxychrysoidin Monohydrochloride [4-(p-Ethoxyphe-nylazo)-m-phenylenediamine Monohydrochloride 4 -Ethoxy -2,4-diaminoazobenzene Monohydrochloride] A red powder, insoluble in water. Transition interval from pH 3.5 (red) to 5.5 (yellow). 

Litmus A blue powder, cubes, or pieces. Partly soluble in water and in alcohol. Transition interval from approximately pH 4.5 (red) to 8 (blue). Litmus is unsuitable for determining the pH of solutions of carbonates or bicarbonates. 

Methyl Orange (Helianthin Tropaeolin D 4 -Dimethylami-noazobenzene-4-sodium Sulfonate) An orange-yellow powder or crystalline scales. Slightly soluble in cold water readily soluble in hot water insoluble in alcohol. Transition interval from pH 3.2 (pink) to 4.4 (yellow). 

Methyl Yellow (p-Dimethylaminoazobenzene) Yellow crystals, melting between 114° and 117°. Insoluble in water soluble in alcohol, in benzene, in chloroform, in ether, in dilute mineral acids, and in oils. Transition interval from pH 2.9 (red) to 4.0 (yellow). 

Quinaldine Red (5-Dimethylamino-2-strylethylquinolinium Iodide) A dark, blue-black powder, melting at about 260° with decomposition. Sparingly soluble in water freely soluble in alcohol. Transition interval from pH 1.4 (colorless) to... 

Thymol Blue (Thymolsulfonphthalein) A dark, brown-green, crystalline powder. Slightly soluble in water soluble in alcohol and in dilute alkali solutions. Acid transition interval from pH 1.2 (red) to 2.8 (yellow). Alkaline transition interval from pH 8.0 (yellow) to 9.2 (blue). 

Table 3-3 TRANSITION INTERVALS OF SELECTED ACID-BASE INDICATORS...

Common name Chemical name Acid color Base color pH transition interval pKin... 

Several indicators have two or more color-change transition intervals (not shown in the table). 

A comparison of neutron spectra with theory was made by Danner et al. (7). These workers obtained data for Marlex 6050 at temperatures below and above the glass-transition interval and the melting point, and for samples of branched, irradiated, and quenched polyethylene at room temperature. The spectrum at 100 K (Fig. 3) showed two peaks with shapes characteristic of acoustic modes at 550 and 200 cm" (peaks C and E in Fig. 3). Five additional peaks were observed at 1360,750,340,... 

Transition Interval,—Fig. 115 will also render intelligible a point of great importance in connection with astracanite, and with double salts generally. At temperatures between those represented by the points B and X, the double salt when brought in contact with water will be decomposed with separation of sodium sulphate. Above the temperature of the point X, however, the solution of the pure double salt is stable, because it can still take up a little of either of the components. At temperatures, then, above that at which the solution in contact with the double salt and the less soluble single salt, contains the single salts in the ratio in which they are present in the double salt,... 

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