Conductivity data

In the case of small ions, Hittorf transference cell measurements may be combined with conductivity data to give the mobility of the ion, that is, the velocity per unit potential gradient in solution, or its equivalent conductance. Alternatively, these may be measured more directly by the moving boundary method. 

Thermal Conductivity. Thermal conductivity data for transparent vitreous silica are listed below (150) ... 

Phonon transport is the main conduction mechanism below 300°C. Compositional effects are significant because the mean free phonon path is limited by the random glass stmcture. Estimates of the mean free phonon path in vitreous siUca, made using elastic wave velocity, heat capacity, and thermal conductivity data, generate a value of 520 pm, which is on the order of the dimensions of the SiO tetrahedron (151). Radiative conduction mechanisms can be significant at higher temperatures. 

Figures 5 and 6 present the electrical conductivity of sulfuric acid solutions (51,52). For sulfuric acid solutions in the 90—100% H2SO concentration range, the electrical conductivity measurements reported by Reference 52 are beheved to be the best values other conductivity data are also available...

D. T. Jamieson, J. B. Irving, andj. S. Eiquid Thermal Conductivity Data Survej to /5 7i, National Engineering Laboratory, Edinburgh,... 

The hydrogen content, heat of combustion, specific heat, and thermal conductivity data herein were abstracted from Bureau of Standards MisceUaneous Pubhcation 97, Thermal Propei tie.s of Petroleum Products. These data are widely used, although other correlations have appeared, notably that by Linden and Othmer Chem. Eng. 54[4, 5], April and May, 1947). 

It is to be expected that tire conduction data for ceramic oxides would follow the same trends as those found in semiconductors, i.e. the more ionic the metal-oxygen bond, the more the oxides behave like insulators or solid elee-trolytes having a large band gap between the valence electrons and holes, and... 

The temperature dependence of the thermal conductivity of CBCF has been examined by several workers [10,13,14]. Typically, models for the thermal conductivity behavior include a density term and two temperaUrre (7) terms, i.e., a T term representing conduction within the fibers, and a term to account for the radiation contribution due to conduction. The thermal conductivity of CBCF (measured perpendicular to the fibers) over the temperature range 600 to 2200 K for four samples is shown in Fig. 6 [14]. The specimen to specimen variability in the insulation, and typical experimental scatter observed in the thermal conductivity data is evident in Fig. 6. The thermal conductivity of CBCF increases with temperature due to the contribution from radiation and thermally induced improvements in fiber structure and conductivity above 1873 K. 

Fig. 7. Thermal conductivity data for CBCF specimens heat treated for 10 seconds (5.7 seconds at temperature) at four different temperatures. Solid lines are predicted curves from Eqs. (5) through (8). Reprinted from [14], copyright 1996 Technomic Publishing Company, Inc., with permission.

Figures 7 and 8 show thermal conductivity data for CBCF after exposure to temperatures of 2673, 2873, 3073, and 3273 K, for 5.7 and 15 7 seconds, respectively. The symbols in the Figs. 7 and 8 represent measured thermal conductivity values, and the solid lines are the predicted behavior from Eqs. (5) through (8) The model clearly accounts for the effects of measurement temperature, exposure tune, and exposure temperature The fit to the data is good (typically within 10%). However, the fit to the as fabricated CBCF data (Fig 6) was less good (-20%), although the scatter in the data was larger because of the much lower heat treatment temperature (1873 K) in that case.

The room temperature conductivity data for a wide variety of ionic liquids are listed in Tables 3.6-3, 3.6-4, and 3.6-5. These tables are organized by the general type of ionic liquid. Table 3.6-3 contains data for imidazolium-based non-haloaluminate alkylimidazolium ionic liquids. Table 3.6-4 data for the haloaluminate ionic liquids, and Table 3.6-5 data for other types of ionic liquids. There are multiple listings for several of the ionic liquids in Tables 3.6-3-3.6-5. These represent measurements by different researchers and have been included to help emphasize the significant vari-... 

It is unclear at this time whether this difference is due to the different anions present in the non-haloaluminate ionic liquids or due to differences in the two types of transport number measurements. The apparent greater importance of the cation to the movement of charge demonstrated by the transport numbers (Table 3.6-7) is consistent with the observations made from the diffusion and conductivity data above. Indeed, these data taken in total may indicate that the cation tends to be the majority charge carrier for all ionic liquids, especially the allcylimidazoliums. However, a greater quantity of transport number measurements, performed on a wider variety of ionic liquids, will be needed to ascertain whether this is indeed the case. 

Table 10-14 tabulates a few unusual and useful thermal conductivity data. 

Due to the fact that K2TaF7 - KF is considered to be part of the TaF5 - KF binary system, while the K2TaF7 - KCI system is a component of the interconnected ternary system K+, Ta5+//F", Cl", the single-molecule conductivity and activation energy of the systems was calculated based on density and specific conductivity data [322, 324]. Molar conductivity (p) depends on the absolute temperature (T), according to the following exponential equation ... 

Such a model of the melt structure does not contradict conductivity data [324], if plotted against the composition of the KF - TaF5 system. Fig. 63 presents isotherms of molar conductivity, in which molar conductivity of the ideal system was calculated using Markov s Equation [315], and extrapolation... 

References to a number of other kinetic studies of the decomposition of Ni(HC02)2 have been given [375]. Erofe evet al. [1026] observed that doping altered the rate of reaction of this solid and, from conductivity data, concluded that the initial step involves electron transfer (HCOO- - HCOO +e-). Fox et al. [118], using particles of homogeneous size, showed that both the reaction rate and the shape of a time curves were sensitive to the mean particle diameter. However, since the reported measurements refer to reactions at different temperatures, it is at least possible that some part of the effects described could be temperature effects. Decomposition of nickel formate in oxygen [60] yielded NiO and C02 only the shapes of the a—time curves were comparable in some respects with those for reaction in vacuum and E = 160 15 kJ mole-1. Criado et al. [1031] used the Prout—Tompkins equation [eqn. (9)] in a non-isothermal kinetic analysis of nickel formate decomposition and obtained E = 100 4 kJ mole-1. 

The conductivity of sodium dodecyl sulfate in aqueous solution and in sodium chloride solutions was studied by Williams et al. [98] to determine the CMC. Goddard and Benson [146] studied the electrical conductivity of aqueous solutions of sodium octyl, decyl, and dodecyl sulfates over concentration ranges about the respective CMC and at temperatures from 10°C to 55°C. Figure 14 shows the results obtained by Goddard and Benson for the specific conductivity of sodium dodecyl sulfate and Table 25 shows the coefficients a and p of the linear equation of the specific conductivity, in mho/cm, vs. the molality of the solution at 25°C. Micellization parameters have been studied in detail from conductivity data in a recent work of Shanks and Franses [147]. 

II. Silver According to DTA data and conductivity data, AggSBr and AgsSI undergo phase transitions at 120 and 163 K, respectively. In AggSI the transition to the low-temperature phase is accompanied by the appearance of additional x-ray reflections (427). 

Hanvelt et al. (1994) estimated the nationwide indirect costs of mortality due to HIV/AIDS in Canada. A descriptive, population-based economic evaluation study was conducted. Data from Statistics Canada were used, which contained information about aU men aged 25-64 years for whom HIV/AIDS or another selected disease was listed as the underlying cause of death from 1987 to 1991. Based on the human capital approach, the present value of future earnings lost for men was calculated. The estimated total loss from 1987 to 1991 was US 2.11 billion, with an average cost of US 558,000 per death associated with HIV/AIDS. Future production loss due to HIV/AIDS was more than double during the period 1987 to 1991, from US 0.27 to US 0.60 billion. A more comprehensive update of this smdy was presented by Hanvelt et al. (1996). The same database and the same data section but for the calendar years 1987-1993 was used. The indirect cost of future production due to HIV/AIDS in Canada based on the human capital approach for that period was estimated to be US 3.28 billion. The authors also calculated the willingness-to-pay to prevent premature death due to HIV/AIDS, which was estimated based on... 

Recently a further study of these reactions has been described (154). The compound originally characterized by Joshi et al. as Mn(CNCgH5)5Br was shown to be a mixture of [Mn(CNC4Hj)4]Br and [MnCO(CNCj-Hj)j]Br, by analyses and conductivity data. The white color reported for this complex is in accord with this new formulation all of the other covalent complexes are yellow or gold. In view of the incorrect characterization of this complex, the isolation of the new complex Mn(CNC6H5)5Cl from... 

Both the reactors are operated in batch, and the concentrations of components involved are measured online by electro-conductivity. Data interpretation is made by the kinetic equation of second order. The results obtained in the range of 25-45"C are given in Table 3. Again, the values for the rate constant measured in SCISR, ks, are S5 tematically higher than those in STR, ksr, by about 20%, and no significant difference betvi een the values for the active energy measured in SCISR and STR has been found. 

The point defects are decisive for conduction in solid ionic crystals. Ionic migration occurs in the form of relay-type jumps of the ions into the nearest vacancies (along the held). The relation between conductivity o and the vacancy concentration is unambiguous, so that this concentration can also be determined from conductivity data. 

Low-frequency conductivity data [37] obtained along this 45°C isotherm are illustrated in Fig 2. The initial oscillatory variation in the conductivity for a > 0.9 can be assigned to variations in AOT partitioning among dimers and other low aggregates and reverse micelles, as reverse micelles are nucleated by added water (brine). These variations will be discussed in greater detail in another publication. The key behavior for the purposes of this exposition is the onset of the electrical conductivity percolation at a = 0.85. The conductivity increases two orders as a decreases from 0.85 to 0.70, and as shown in the inset, the conductivity increases another two orders as a a decreases from 0.7 to 0.3. 

FIG. 6 Self-diffusion and conductivity data reported by Feldman et al. [25] for reverse water, decane, and AOT microemulsion as a function of temperature. The Op and arrow between 18 and 19°C shows the approximate onset of percolation in low-frequency conductivity and a breakpoint in water self-diffusion increase. Another breakpoint, at about 28°C, occurs in the AOT self-diffusion data where AOT self-diffusion begins to markedly increase. 

As described in the introduction, certain cosurfactants appear able to drive percolation transitions. Variations in the cosurfactant chemical potential, RT n (where is cosurfactant concentration or activity), holding other compositional features constant, provide the driving force for these percolation transitions. A water, toluene, and AOT microemulsion system using acrylamide as cosurfactant exhibited percolation type behavior for a variety of redox electron-transfer processes. The corresponding low-frequency electrical conductivity data for such a system is illustrated in Fig. 8, where the water, toluene, and AOT mole ratio (11.2 19.2 1.00) is held approximately constant, and the acrylamide concentration, is varied from 0 to 6% (w/w). At about = 1.2%, the arrow labeled in Fig. 8 indicates the onset of percolation in electrical conductivity. 

The exponential decay predicted by the Onsager-Machlup theory, and by the Langevin and similar stochastic differential equations, is not consistent with the conductivity data in Fig. 8. This and the earlier figures show a constant value for >.(x) at larger times, rather than an exponential decay. It may be that if the data were extended to significantly larger time scales it would exhibit exponential decay of the predicted type. 

The experimental methods used for the determination of thermal conductivity are described by Tsederberg (1965), who also lists values for many substances. The four-volume handbook by Yaws (1995-1999) is a useful source of thermal conductivity data for hydrocarbons and inorganic compounds. 

When reporting the molar conductivity data, the species whose amount is given in moles should be indicated. Often, a fractional molar conductivity corresponding to one mole of chemical equivalents (called a val) is reported. For example, for sulphuric acid, the concentration c can be expressed as the normality , i.e. the species H2S04 is considered. Obviously, A(H2S04) = 2A( H2S04). Consequently, the concept of the equivalent conductivity is often used, defined by the relationship... 

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