Influence of the Ionic Strength

The small ions in the system are Na and CH3SO4. If we add an excess of sodium methylsulfate in the system the diphasic area promptly decreases and finally disappears (Fig. 9.6). 

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Influence of ionic strength on the reaction rate constant. The influence of the ionic strength on the reaction rate constant was studied using KCl as electrolyte. The results obtained in this study are listed in Table 4, where we can see that the reaction rate constant for N-Br-alanine decomposition undergoes an increment of 40 % upon changing the ionic strength from 0.27M to IM, while in the case of N-Bromoaminoisobutyric acid the increment of the reaction rate constant is of about 12 %. This is an evidence of a non ionic mechanism in the case of the decomposition of N-Br-aminoisobutyric acid, as it is expected for a concerted decarboxylation mechanism. For the decomposition of N-Br-proline the increase on the reaction rate constant is about 23 % approximately, an intermediate value. This is due to the fact both paths (concerted decarboxylation and elimination) have an important contribution to the total decomposition process. 

Figure 1. Influence of the ionic strength on the phase separation curve of the C73 sample at pH 7, 20°C in presence of CuCl2.

Figure 2. Influence of the ionic strength and the polymer concentration on the binding isotherms of Pb2+ by sugar-beet pectins in water (empty symbols) and in 0.1 M NaNOs (full symbols) at 25°C ( ) 2 mequiv. COO. l-, ( ) 8 mequiv. COO-.l-i (—) total binding of added Pbz+.

Fig. 16. Influence of the ionic strength in the prevention of readhesion phenomenon in the case of a positive particle on a negative substrate (alumina slurries on silicon oxide layer) a high-ionic-strength limit the double layer thickness. Particle and substrate are therefore electrically masked at a closer particle-substrate distance. (The double layer of the substrate is not represented here.)...

In biotechnological processes involving ions at concentrations higher than normal (>0.1 M), the influence of the ionic strength and the non-ideahty of the solution on the yield must also be considered. In case, where attractive ion-ion interactions are involved, a higher ionic strength reduces the yield, whereas the opposite applies for repulsive interactions (Kasche, 1986). 

Did you study the influence of the ionic strength on the catalytic functions of the synzymes ... 

The influence of the ionic strength on the clotting time of -casein at 35°C is shown in Figure 4. The pronounced minimum is strongly reminiscent of the minimum found with milk (11,12), though it occurs at a considerably lower ionic strength. 

Figure 4. Showing the influence of the ionic strength on the enzymatic clotting time of K-casein (0.1 g/100 mL) at pH 6.7 and 35°C. Clotting strength in reaction mixture, 0.8 SU.

The Influence of the Ionic Strength on the Clotting Time. We have seen that between I = 0.03 and 0.5 an increase of the ionic strength chiefly brings about a decrease of the rate of proteolysis. We shall now present a simple argument to explain the effect of salt and to show the importance of the cluster of cationic residues around the labile Phe-Met bond in -casein (5) in stabilizing the ES-complex. If the latter is identified with Bronsted s activated complex (13), one has for the rate of proteolysis... 

Figure 8. Model calculation of the influence of the ionic strength on the rate of proteolysis of K-casein by chymosin. Model parameters (cf. Equations 13 and 14) Z = —8 r = 2.5 nm a = 2.75 nm 3 pairs of electrostatic bonds formed at rt1 = 0.25 nm. (A) Overall electrostatic repulsion (first term on rhs of Equation 13) (B) Local side-chain attractions (second term on rhs of Equation 13) (C) yeByeslyeB8 (Equation 11).

Fig. 16. Influence of the ionic strength on the counterion activity of PDADMAC with different molar masses. Variation of the ionic strength by addition of NaCl. (X=Cp / cs cp=10-3 mono-mol L-1 T=20 °C PDADMAC Mn 12,000 g mol-1 22,000 g mol-1 72,000 g mol-1 A 170,000 g mol-1 - - - Gueron -Manning .Iwasa) (Data taken from[38])...

Fig. 9.18 shows the influence of the ionic strength I on the Mark-Houwink exponent a. Although there is a large amount of scatter, the data clearly indicate a decrease of a with... 

A kinetic electrolyte effect ascribable solely to the influence of the ionic strength on activity coefficients of ionic reactants and transition states is called a primary kinetic electrolyte effect. A kinetic electrolyte effect arising from the influence of the ionic strength of the solution upon the pre-equilibrium concentration of an ionic species that is involved in a subsequent rate-limiting step of a reaction is called a secondary kinetic electrolyte effect. A common case encountered in practice is the effect on the concentration of a hydrogen ion (acting as catalyst) produced from the ionization of a weak acid in a buffer solution. 

Influence of the ionic strengths of various salt solutions on the solubility 5 of a protein such as hemoglobin So is the solubility at zero ionic strength. 

In the last decade hollow spheres are extensively studied in the context of application as containers of prolonged action for substances of the different chemical nature dmgs, cosmetics, dye. A number of methods for preparation of microspheres with the sizes ranging from nanometers to micrometers and consisting of various materials are developed. Polyelectrolye capsules have been produced by sequential adsorption of oppositely charged polyelectrolytes, also known as Layer-by-Layer (LbL) assembly onto the surface of colloidal particles followed by core dissolution [1-2]. Most of the capsules applications imply their chemical or physicochemical modification by influence of the ionic strength [3], pH [3], temperature... 

Many problems still remain to be solved for pH FOCS. Areas still not completely under control are the techniques of immobilization and grafting on the support, permanent monitoring of the concentration of the indicators, ionophore lifetime [60], stability of maintenance of the dye on the support over a wide pH range, determination of the dissociation constant of the immobilization dye [61], optode reversibility, reproducibility of their manufacture (disposal optodes), monitoring of the influence of the medium, and the simplification of calibration procedures. Some progress has been achieved in the understanding of the influence of the ionic strength of the medium. 

Figure 18. Influence of the ionic strength Is of the solvent (NaCl addition) on the flow resistance factor for solutions of HPAA 30.5% hydrolysis, 8.7 x...

In future experiments, the influence of the ionic strength on the swelhng should be investigated. Monomer ratio in the feed as weU as cross-linker and initiator concentration should be varied. The method may then open up an easy route to coat sensors with mM//i-stimuli responsive hydrogels. 

In the case of the fumed-silica dispersion (cf. Figure 14.1(b)) a strong dependency of the RRs on the pH value can be noticed, but the influence of the ionic strength is not significant. Whilst the RR for a salt-free dispersion at a pH value of 4.1 is negligible it is very high at a pH value of 10.1. 

While the influence of the ionic strength probes the electrostatic nature of the interaction for the uncoated and PLL-coated Nb20s samples, it also provides relevant information for the... 

In separate experiments it was established that under the described experimental conditions the sFeOH site represented the majority of surface groups on magnetite. The above results, and additional ones, in which the influence of the ionic strength was investigated, could be interpreted by assuming the following equilibria ... 

Tirf, ) are normalized by their values at pH = 5. The experimental data show that both the surface elasticity, Ec, and relaxation time, increase with increase of pH. The interfacial dilatational viscosity, y d, exhibits a maximum at pH = 6. A similar peak of the interfacial shear viscosity of BSA at pH = 6 has been observed by Graham and Phillips [188] at petroleum ether—water interface. The results in Fig. 9 demonstrate a marked influence of the ionic strength on the rheological parameters. 

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