Gelatin ionic groups

Starches can be substituted by nonionic or ionic groups. The latter can be made anionic by introduction of phosphate or succinate groups. These have lower gelatinization temperature, higher peak viscosity, and higher final cold viscosity than nonionic starches (Figure 8-38). 

In a qualitative way, colloids are stable when they are electrically charged (we will not consider here the stability of hydrophilic colloids - gelatine, starch, proteins, macromolecules, biocolloids - where stability may be enhanced by steric arrangements and the affinity of organic functional groups to water). In a physical model of colloid stability particle repulsion due to electrostatic interaction is counteracted by attraction due to van der Waal interaction. The repulsion energy depends on the surface potential and its decrease in the diffuse part of the double layer the decay of the potential with distance is a function of the ionic strength (Fig. 3.2c and Fig. 

Fig. 4. Study of the equilibrium between pyruvic acid and glycine. 5.6 x 10 4 M Sodium pyruvate, 0.005% gelatin, glycine buffer pH 9.2. Concentration of the form of glycine with the free amino group is given in the polarogram. Ionic strength kept constant by addition of sodium chloride. Curves starting at —0.8 V, S.C. E., 200 mV/absc.,

The trivalent state is the characteristic one for all the lanthanides. They form oxides, M203, which resemble the Ca-Ba group oxides and absorb carbon dioxide and water from the air to form carbonates and hydroxides, respectively. The hydroxides, M(OH)3, are definite compounds, having hexagonal structures, and not merely hydrous oxides. The basicities of the hydroxides decrease with increasing atomic number, as would be expected from the decrease in ionic radius. The hydroxides are precipitated from aqueous solutions by ammonia or dilute alkalis as gelatinous precipitates. They are not amphoteric. 

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