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Effects of Ionic Strength

Ionic strength, I, is a measure of the concentration of electrically chaiged species in solution [Pg.244]

Using the numerical value of A for aqueous solutions at 25 °C, this becomes [Pg.245]

The increase in I increases the rate constant for reactions between ions of the same charge and decreases it when the ions are oppositely charged. This kinetic effect of addition of a salt to the solutions, when the salt is not involved in the reaction, was studied in detail by Bronsted [12] and Bjerrum [13] and the expression, which it represents, is known [Pg.245]

For reactions in which one of the species is neutral, ionic strength should not have any effect. In practice, there are often small effects of changing ionic strength when reactions are catalysed by acids or bases. These are known as secondary salt effects, and are due to effects of ionic strength on acid-base equilibria. [Pg.245]

At the low ionic strengths (1=0.5 10 ), typical of natural waters, FA and HA were found to be very large (Clark and Jucker (1994)). The hydrodynamic diameters of HSs were found to vary between 15 [Pg.25]

We have shown that the energy barrier opposing deposition is linear with Debye length (Fig. 16.3b), which depends in turn on the ionic [Pg.640]

This experiment is significant because it shows that there is a maximum deposition density that can be achieved. This maximum could not be reached in the kinetics experiment because of the very long time period that would be required and in the pH experiment at pH below 3 the DNA-SWCNTs coagulate. Thus, increasing the salt concentration provides a simple way of maximizing deposition density, while still producing aligned DNA-SWCNTs. [Pg.641]

We now apply our kinetics models to this experiment. Under conditions where the energy barrier is linear in surface potential, that is, for small x/Id, it follows from Eq. 16.3 that AE a 1. If we represent this linear dependence by [Pg.642]

In case 11 kinetics, on the other hand, the density of deposited objects is limited by the number of available sites. The fit of Eq. 16.12 in the Fig. 16.4d fit was made with pt = 2.5 pm/pm, since the deposition appears to reach this clearly defined limit This is slightly greater than the site density obtained at a lower salt concentration from the fit of the kinetics data in Fig. 16.4a, pt = 1.9pm/pm. In this case, AE = Dtl + D2. [Pg.642]

Since case 11 kinetics, but not case 1 kinetics, successfully predict a limit to the deposition density, we have plotted only the case 11 fits in Fig. 16.4. We will now consider the possible nature of these sites. [Pg.642]

Temperature and pH are the most relevant environmental variables affecting enzyme behavior. However, there are other variables, like ionic strength, that may also have a significant effect on enzyme kinetics. Ionic strength is defined as  [Pg.148]

The effect of ionic strength in enzyme kinetics is seldom made explicit though special precautions are usually taken to obtain kinetic parameters under constant ionic strength. In fact, ionic strength has been considered as a neglected variable in enzyme kinetics, but it has been proven that it affect enzyme behavior at values over 100 mM (Dale and White 1982). Enzymes are polyionic polymers and may have charged amino acid residues at the active site moreover, substrates may also contain [Pg.148]

Starting from the Debye-Huckel theory, it is possible to formulate equations for the kinetic parameters of the enzyme considering that both the substrate and the enzyme at its active site are charged (Buchholz et al. 2005)  [Pg.149]

We have evaluated the effect of ionic strength on the kinetic parameters of lactose hydrolysis with (3-galactosidase from Aspergillus oryzae in Mcllvaine citrate-phosphate buffer at concentrations from 50 to 400 mM and found an increase in K but almost no effect on V (kcat). Studies on the effect of ionic strength on enzyme kinetics are not usual, so that works with acetylcholinesterase (Nolte et al. 1980), myosin kinase (Blumenthal and Stull 1982) and cytochrome C (Hazzard et al. 1991 Harris et al. 1994) are worth mentioning. Combined effect of pH and ionic strength on enzyme kinetics has been recently analyzed (Alberty 2006). [Pg.149]

A Pre-exponential factor in Arrhenius equation (frequency factor) [Pg.149]


Klapper 1, R Hagstrom, RFine, K Sharp and B Honig 1986. Focusing of Electric Fields in tire Actir e Sit of CuZn Superoxide Dismutase Effects of Ionic Strength and Amino-Acid Substitution. Proteins Structure, Function and Genetics 1 47-59. [Pg.651]

The Effect of Ionic Strength on an Equilibrium Constant (A Class Study). In J. A. Bell, ed. Chemical Principles in Practice. Addison-Wesley Reading, MA, 1967. [Pg.176]

Most ingredients in a detergent formulation contribute to the ionic strength of the wash solution. The effect of ionic strength on protease performance depends on pH and enzyme identity. The pH wash solutions also affects protease performance (Pig. 8). [Pg.294]

FIGURE 4.17 Effect of ionic strength on the elution of anionic polymers. Column TSK-GEL GMPW, two 17 fjLirt, 7.5 mm X 60 cm columns in series. Sample 0.5 ml of 0.05-0.1% of the sodium salt of polyacrylic acid, an anionic polymer. Elution Water 0.01, 0.025, 0.05, or 0.1 M NaNOs in water. Flow rate 0.5 ml/min. Detection Rl. [Pg.115]

FIGURE 19.5 Effect of ionic strength on elution of p(acrylic acid) from TosoHaas GMPW columns. (Courtesy of TosoHaas.)... [Pg.555]

An effect of ionic strength on as a consequence of effects on the activity coefficient ratio is called a primary salt effect. We will, in Section 8.3, consider this effect quantitatively. [Pg.386]

The accelerating effect of ionic strength on the reaction between Cu and Co(NH3)5C12 is illustrated. The axes are the quantities specified by the Brpnsted-Debye-Hiickel equation—log k and ju. 1/2/( 1 + fc n). [Pg.209]

No profound effect of pH on K was observed for waters which ranged from pH 4 (Okeefenokee°Swamp) to pH 8 (Lake Michigan). Nor was there an effect of ionic strength on K in the samples which ranged in composition from that of the oceans to that of a lake with a conductivity of less than 20iaS/cm. [Pg.310]

Effects of Ionic Strength on the Inhibition of D-GIucosidases by 1-Deoxynojirimycin... [Pg.380]

Habib and Hunt have continued the study of this reaction, obtaining further data with special reference to the effects of ionic strength, sulphate and hydrogen-ion concentrations. From data obtained on the dependence of the rate on the [H ] at various temperatures, values of the kinetic parameters differing slightly from those above have been obtained. Values of AFff and and AS and AS2 (at n = 1.0 M) obtained were 11.8, 5.3 kcal.mole and —17 and —31 cal.deg mole respectively. The value of 2 was estimated as 6.7 x 10 1. mole sec at 18 °C, n — 1.0 Af. [Pg.113]

Figure 2. Effect of ionic strength on Rp for different polystyrene particle sizes using SLS or AM A in eluant. Figure 2. Effect of ionic strength on Rp for different polystyrene particle sizes using SLS or AM A in eluant.
Figure 8. Effect of ionic strength on the release of 10 pm glass particles from a glass surface. Figure 8. Effect of ionic strength on the release of 10 pm glass particles from a glass surface.
Over the last several years, the number of studies on application of artificial neural network for solving modeling problems in analytical chemistry and especially in optical fibre chemical sensor technology, has increase substantially69. The constructed sensors (e.g. the optical fibre pH sensor based on bromophenol blue immobilized in silica sol-gel film) are evaluated with respect to prediction of error of the artificial neural network, reproducibility, repeatability, photostability, response time and effect of ionic strength of the buffer solution on the sensor response. [Pg.368]

Daughney CJ, Fein JB (1998) The effect of ionic strength on the adsorption of H+, Cd2+, Pb2+, and Cu2+ by Bacillus subtilis and Bacillus licheniformis a surface complexation model. J Colloid Interface Sci 198 53-77... [Pg.94]

Peng, J., Wan, A. (1998) Effect of ionic strength on Henry s law constant of volatile organic compounds. Chemosphere 36, 2731-2740. Peng, J., Wan, A. (1998) Effect of ionic strength on Henry s constants of volatile organic compounds. Chemosphere 36, 2731-2740. Pennell, K.D., Rhue, R.D., Rao, P.S.C., Johnston, C.T. (1992) Vapor-phase sorption of p-xylene and water on soils and clay minerals. Environ. Sci. Technol. 26, 756-763. [Pg.613]

In addition, (-potential measurements on PCP showed no significant effect of ionic strength on adsorption characteristics [123]. This finding suggests that no ion pair is formed, but also indicates that screening of the membrane surface by ions has little effect on the energetics of adsorption, i.e. PCP is buried at some depth below the membrane surface. [Pg.232]


See other pages where Effects of Ionic Strength is mentioned: [Pg.621]    [Pg.174]    [Pg.174]    [Pg.449]    [Pg.32]    [Pg.377]    [Pg.556]    [Pg.218]    [Pg.380]    [Pg.112]    [Pg.104]    [Pg.3]    [Pg.269]    [Pg.435]    [Pg.409]    [Pg.275]    [Pg.177]    [Pg.552]    [Pg.313]    [Pg.313]    [Pg.314]    [Pg.317]    [Pg.317]    [Pg.429]    [Pg.222]    [Pg.220]    [Pg.262]    [Pg.266]    [Pg.392]   
See also in sourсe #XX -- [ Pg.298 ]

See also in sourсe #XX -- [ Pg.485 ]




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