Water dielectric constant values

Table 1.4 Solvent descriptors of organic solvents commonly used for biocatalysis. Sw/o (solubility of water in solvent, wt%) So/w (solubility of solvent in water, wt%) and e (dielectric constant) values from [78], log P (P = partition coefficient between octanol and water), ET (empirical polarity parameter by Reichardt-Dimroth) and HS (Hildebrand solubility parameter, )l, cm J, ) from [79].

However this would necessitate the determination of the derivative of a with respect to Z. This quantity cannot be measured with enough accuracy, especially when the association constant KA is small (this is the case in the high dielectric constant values of the solvents studied D 30). We have made two conductance runs, in a 59.02% water-THF mixture and in a 81.90% water-AC... 

The abnormally high dielectric-constant values observed for certain liquid substances, such as water and ammonia, were attributed by Latimer and Rodebush to continued polymerization through hydrogen-... 

Along I lie saturation line, the steam and water values converge at the critical point. The ability of water to dissolve salts results from the high dielectric constant. The precipitous drop in water dielectric constant in the region of the critical point is very important to the solubility of salts in water near the critical temperature. Many salts exhibit declining solubilities as the critical temperature is approached and then exceeded. The drop in dielectric constant is largely a result of the decline in density. 

An approximate value of the radius of the ionic atmosphere r as a function of concentration, for a uni-univalent (1-1) electrolyte at 25 °C and water as solvent, considering 79 as the dielectric constant value, may be obtained from the relationship... 

The dielectric constant values in Table 2.8 also suggest that, while hydrate water molecules reorient rapidly compared to molecules in other solids, reorientation rates are only one-half those in ice. The hydrate value is lower than that of ice due to the lower density of hydrogen-bonded water molecules. 

Water-TMS Mixtures. Conductometric studies on Li, Na, and K chlorides and hydrochloric acid in water-TMS have shown association constants higher than the Fuoss equation predicts in these mixtures too. In the case of HCl, KA values equal to 26 5, 51 d= 9, and 76 4 corresponded to dielectric constant values of 61.42, 54.69, and 47.34, respectively. On the contrary, KA values for the same systems calculated on the basis of the Fuoss equation using the reasonable value of 4 A for the... 

The MD runs in the presence of water were performed surrounding the above equilibrated system with a shell of 300 water molecules. The wateradd DLPOLY [93] utility was used to add the water molecules. A dielectric constant value of 1.0 was employed in all the experiments. 

The DLPOLY utilities wateradd and solvadd were employed to add 8 Ca " ions, 20 Na" ions, 12 Cl" ions and 1024 rigid Simple Point Charge (SPC) [95] water molecules to a cell containing 3 PGA chains, each formed by 24 galacturonic units one third of which were taken as deprotonated. The Ewald summation method was employed to evaluate the coulomb interactions with a dielectric constant value of 1.0. A time step of 0.001 ps was adopted in all the simulations. 

Consideration of the relative permittivity Kr) or dielectric constant values can be important when selecting a solvent for a particular solute. The term refers to the ability of the solvent to decrease the coulombic field of an ion. For example, the value for water is of the order of 78.5 which relates to the extent the field is reduced in the liquid, compared with a vacuum, at a distance r from the solute species. Thus water is a very powerful solvent for salts because it greatly decreases the coulombic interactions between the oppositely charged species and hence these do not readily interact to form solid or crystalline salts, as outlined below. 

Table 3 Comparison of Dielectric Constant Values for Water at Various Temperatures and Organic Solvents at Ambient Conditions...

Figure 2 shows the effect of the solvent molar volume on AG°,c for a single dielectric constant value, es = 10. It may be seen that becomes more positive when V,s is increased. Moreover, the bias toward large ions also increases. Negative values of AG°r,ci re mathematically allowed for solvent molar volumes smaller than that of water, an unexpected condition. 

Table 9.1 Relative permittivity (dielectric constant) values at 298 K (unless otherwise stated) for water and selected organic solvents.

Figure 8.39 Dielectric constant values as a function of the volume fraction of the aqueous micellar core in the L2-phase of the system sodium octanoate/decanol/water. The regions I-III correspond to the premicellar solution, the region of spherical micelles and the region with rod-shaped micelles respectively (Sjoblom et aL, 1983).

KLEIN - You utilize the primitive model and experimental bulk water dielectric constant to normalize your potential of mean force calculations. Would it not be more natural to use the value of the dielectric constant appropriate to your water model (TIP P) How could this affect your results ... 

The efficiency of PEDOT PSS to stabilize individual SWCNTs in water, without the presence of low molar mass surfactants like SDS, has been shown using a UV-Vis spectroscopy method developed by Grossiord et al. This method was used to determine the optimal [PEDOT PSS) SWCNT ratio. The maximum achievable SWCNT exfoliation was achieved with a (PEDOT PSS) SWCNT ratio of 1 4. The final absorbance level observed in UV-Vis absorption spectra of dispersions after completion of the dispersion process was slightly higher for dispersions prepared with PEDOT PSS as compared to control SDS dispersions. This is most likely linked to a change of the dielectric constant value (s) due to the presence of a new medium in the vicinity of the nanotubes (shifts in absorption spectra are possible in a new chemical environment). Assuming 100% SWCNT exfoliation, the value for of the SDS-stabilized SWCNT dispersions, before 7i-plasmon subtraction, was determined to be 46.4 ml mg" cm at 500 nm, which is similar to reported values. It should be kept in mind that the UV-Vis absorbance spectrum of the PEDOT PSS itself is likely to be influenced by the presence of the SWCNTs. This makes quantitative analysis of these spectra impossible since the final absorbance is not simply a summation of the absorbance of the constituents measured independently (unlike exhibited for... 

Since n transition energies of these states in (1) gas-phase, (2) with discrete water molecules, and (3) and (4) in the presence of bulk solvent with two dielectric constant values e = 7.0 and 78.4, respectively, for TNI and their adiabatic states. As an example, the plot of the variation of transition energies of 7T a(5 -P04) with increasing solvation is shown in O Fig. 34-18. From O Fig. 34-18, it is evident that transition energies for the increase with increasing solvation and... 

The static permittivity or dielectric constant of a material under given conditions reflects the extent to which it concentrates electrostatic lines of flux. Technically, it is the ratio of the amount of electrical energy stored in a material by an applied voltage, relative to that stored in a vacuum. Similarly, it is also the ratio of the capacitance of a capacitor using that material as a dielectric, compared to a similar capacitor which has a vacuum as its dielectric. The dielectric constant values of water have been given, for example, by Fernandez et al. (1995). 

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