Inhibition of dissolution

FIGURE 17.9 Inhibition of dissolution and recrystallization of sulfathiazone by PVP. Temperature cycling of 2% sulfathiazole suspensions demonstrating the effect of PVP on dissolution and recrystallization. (Publication by Ziller, K. H. and Rupprecht, H. H. (199 )harm. Ind., 52 1017-1022. With permission.)... 

Although the detailed nature of the surface of costal strips is not known, evidence from binding studies indicate that cations such as Co and Fe + are preferentially adsorbed onto these structures (9). Similar interactions have been shown with organic and colloidal materials (9). For example, phospholipid vesicles were shown to be closely attached to the surfaces of costal rods incubated in aqueous dispersions of phosphatidylcholine for 24 hr. Similar observations were made for costal rods incubated in solutions of colloidal silica. These results indicate that a range of interactions can take place on the surface of biogenic silica and such events may serve important functional roles, such as inhibition of dissolution and adhesion of components in the construction of microscopic structures. 

Corrosion and Passivity. The inhibition of dissolution is important m the corrosion of metals and building materials. Passivity is imparted to many metals by overlying oxides, the so-called passive films the inhibition of the resolution of these passive layers protects the underlying material. Figure 13 eves a schematic model of the hydrated passive film on iron. 

Surfactants function by altering the interfacial tension between the solid (particles) and liquid (surfactants). Their action as anticaking agents is not clearly understood, and various mechanisms have been proposed - protection from moisture, spreading of liqiid film, modification of crystal makeip/behavior, inhibition of dissolution and crystallization, and modification of bond tensile strength. 

The anodic behaviour of metals encompasses several well-defined phenomena, such as active dissolution, passivity, and the active-passive transition, inhibition of dissolution, formation of bulk oxides, as well as other less well classifiable behaviour. The anodic behaviour of iron in sulphuric and nitric acids has generated a great number of papers and the following example can be taken as an indication of the complexity of the processes involved. 

In contrast to nucleation control, inhibition of phase transformation does not require selectivity, as interactions with both substrates (inhibition of dissolution of the metastable phase and growth of the stable phase) may be rate-controlling [22,50] (see also Sections n.D and ni.B and Fig. 6). It is therefore not surprising that both the anionic SDS and the cationic DDACl effectively inhibit the transformation of COD into the thermoynamically stable COM (Fig. 9) [68]. 

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