Viscosity electrolyte concentration

The physical picture in concentrated electrolytes is more apdy described by the theory of ionic association (18,19). It was pointed out that as the solutions become more concentrated, the opportunity to form ion pairs held by electrostatic attraction increases (18). This tendency increases for ions with smaller ionic radius and in the lower dielectric constant solvents used for lithium batteries. A significant amount of ion-pairing and triple-ion formation exists in the high concentration electrolytes used in batteries. The ions are solvated, causing solvent molecules to be highly oriented and polarized. In concentrated solutions the ions are close together and the attraction between them increases ion-pairing of the electrolyte. Solvation can tie up a considerable amount of solvent and increase the viscosity of concentrated solutions. 

It is now admitted that the intrinsic viscosity in monovalent electrolyte (concentration Cs) is given by the folloving relation ... 

Solutions of hydrolyzed copolymer lose viscosity exponentially as electrolyte concentration in the solution increases. 

Viscosity of copolymer solutions decreases by, at most, 3 percent when electrolyte concentration changes from 0 to 0.342 M sodium chloride or 2.45 x 10 M calcium chloride. Viscosity of hydrolyzed polymer solutions decreases exponentially with increasing electrolyte concentration in water. 

Figure 5.17 The low shear viscosity as a function of concentration for a latex particle with an electrolyte concentration of 10 4M and radius of 38 nm. This is compared with the modified Eyring23 model and the hydrodynamic contribution to the flow...

Drug release profiles from the tablets in various dissolution media are shown in Fig. 2. In all cases the release rates decreased initially from the control (distilled water) as electrolyte concentration increased, until a minimum release rate was obtained. As the electrolyte concentration further increased the release rates similarly increased until a burst release occurred. These initial decreases in release rates were probably coincident with a decrease in polymer solubility, in that as the ionic strength of the dissolution medium is increased the cloud point is lowered towards 37°C. It may be seen from Table 5 that minimum release rates occurred when the cloud point was 37°C. At this point the pore tortuosity within the matrix structure should also be at a maximum. It is unlikely to be an increase in viscosity that retards release rates since Ford et al. [1] showed that viscosity has little effect on release rates. Any reduction in hydration, such as that by increasing the concentration of solute in the dissolution media or increasing the temperature of the dissolution media, will start to prevent gelation and therefore the tablet will cease to act as a sustained release matrix. 

In the presence of sodium tosylate (NaTos), both the rate constant kexp and the viscosity of the solution show maxima at the same electrolyte concentration. The dramatic variation in 17 shown in Figure 8.10a suggests that the sodium tosylate alters the shape of the micelles, first producing rodlike structures that subsequently break up into more compact structures. The complicated phase diagrams of surfactants make this a plausible explanation. Effects such as this clearly complicate the picture not only of inhibition, but also of micellar catalysis in general. 

Note, further, that this leveling off occurs at progressively lower potentials as the concentration of electrolyte increases. Increasing both the potential and the electrolyte concentration tends to increase the field in the double layer (see Table 12.1), which in turn increases the viscosity of solvent in the double layer. As the effective viscosity of the medium increases, the surface of shear occurs progressively further from the surface. This accounts for the fact that hs falls behind J/0 as [/0 increases. These conclusions are consistent with the experimental observation that HS for Agl becomes independent of the concentration of the potentialdetermining Ag + and I ions once the concentrations of these ions are well removed from the conditions at which the particles are uncharged. 

What happens when the dimensions are furthermore reduced Initially, an enhanced diffusive mass transport would be expected. That is true, until the critical dimension is comparable to the thickness of the electrical double layer or the molecular size (a few nanometers) [7,8]. In this case, diffusive mass transport occurs mainly across the electrical double layer where the characteristics (electrical field, ion solvent interaction, viscosity, density, etc.) are different from those of the bulk solution. An important change is that the assumption of electroneutrality and lack of electromigration mass transport is not appropriate, regardless of the electrolyte concentration [9]. Therefore, there are subtle differences between the microelectrodic and nanoelectrodic behaviour. 

Ref. [44]), but this equation is valid only for dilute solutions. At higher electrolyte concentrations, another, empirical equation by Gordon (see Ref. [44]) should be applied, which takes the influence of the liquid phase viscosity into account... 

The EOF is inversely proportional to the viscosity r] of the electrolyte, proportional to its dielectric constant e, the applied field strength E and the -potential (zeta-potential). For FS capillaries, the EOF diminishes with increasing electrolyte concentration, and increases with the degree of dissociation of the surface... 

The effects of the electrolyte concentration on gel viscosity are typically insignificant. For example, it was reported543 that a 100-fold increase of the electrolyte concentration changes the viscosity by only 3%. Such a result suggests that, again, only interactions of ions with a phosphoric acid moiety are involved. However, the effect of salts on the specific rotation of starch gels points to interactions between ions, and the amylose helix and amylo-pectin.516... 

It is known [41] that NBF/CBF transition occurs in a foam from NaDoS solution with constant electrolyte concentration (more than 0.3 mol dm 3 NaCl) within the temperature range from 30 to 35°C (see Section 3.4.2). To confirm that the difference in flow rates is related to the foam film type studies were performed to establish the temperature dependence of the foaming solution flow rate through NaDoS foam with NBF (in the presence of 0.4 mol dm 3 electrolyte). The results from this series of experiments show that with the change in temperature from 20 to 25°C, vexp increases in accord with the decrease in solution viscosity. Further temperature rise (30-35°C) leads to a jump-like increase in flow rate (Fig. 5.2. - (x) points lay on curve 2 which is for CBF). Obviously, this coincides with the NBF/CBF transition. 

Approximate results calculated via Eq. (27.57) are also shown as dotted lines in Fig. 27.2. It is seen that Ka > 100, the agreement with the exact result is excellent. The presence of a minimum of L Ka, la, alb) as a function of Ka can be explained qualitatively with the help of Eq. (27.57) as follows. That is, L Ka, la, alb) is proportional to 1/k at small Ka and to k at large Ka, leading to the presence of a minimum of L Ka, la, alb). As is seen in Fig. 27.3, for the case of a suspension of hard particles, the function L ko) decreases as Ka increases, exhibiting no minimum. This is the most remarkable difference between the effective viscosity of a suspension of soft particles and that for hard particles. It is to be noted that although L Ka, la, alb) increases with Ka at large Ka, the primary electroviscous coefficient p itself decreases with increasing electrolyte concentration. The reason is that the... 

FIGURE 15.4 The effect of electrolyte concentration on the viscosity of 13.2% A90 silica at pH as a function of shear rate. 

Figure 10 shows the variation of the relative viscosity with the counterion molarity at different reduced shear stress values for monodisperse polystyrene latex having a diameter of 0.192 xm at dispersed-phase volume fraction = 0.509. Clearly, is a function of the electrolyte concentration in addition to the reduced shear stress. 

Figure 10. Variation of relative viscosity of monodisperse polystyrene latex with electrolyte concentration at different reduced shear stress. (Reproduced with permission from reference 31. Copyright 1972 Elsevier.)...

Sodium alginate is incompatible with acridine derivatives, crystal violet, phenylmercuric acetate and nitrate, calcium salts, heavy metals, and ethanol in concentrations greater than 5%. Low concentrations of electrolytes cause an increase in viscosity but high electrolyte concentrations cause salting-out of sodium alginate salting-out occurs if more than 4% of sodium chloride is present. 

However, many authors [122-124] assume equality of potentials C = j/ d l ast for low values of surface potentials and low concentrations of electrolyte in the bulk phase. At higher values of the potential and higher concentrations, viscosity close to the surface increases due to the increase of surface concentration. Then, the boundary plane of the mobile layer moves deep into the solution and the anticipated value C is lower than the value IV dl- Both potentials C and ipd are diffuse ones and therefore must be of the same sign and must behave in the same way with the change of electrolyte concentration. 

St e 3 Finally, at very high electrolyte concentrations, interlayer spacings diminish even further and extensive flocculated structures build up, again raising the viscosity (Figure 8.6). 

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