Specific conductivity values

Janz et al. compiled the specific conductance values in the temperature range from 460 to 540 K (187 to 267 °C) [38]. With a decreasing NaCl content compared with NaAlCl4 (the melt becomes acidic) the conductance also decreases. Table 11 contains the conductance values. 

NOTE Alkalinity values in excess of 20 to 25% of specific conductance values gives a more practical guide for the onset of foaming. 

Not surprisingly, e and e" increased with increasing water content, but especially when the water content reached 6 and 13 H2O/SO3H (mol/mol). This, by the usual argument, may reflect a situation where, at these hydration levels, there are water molecules beyond those that are ion-bound that are free to rotate and therefore increase the overall polarizability. There appear to be no peaks that rise above the considerable noise in the loss spectra, as seen in the spectra for pure water. The low /behavior of the e" versus /curves exhibits a la> (co = 2jtJ) dependence, so that specific conductivity values could be extracted in the usual way. These conductivities compare favorably with those obtained by Zawodzinski et al. °... 

Many surface waters are extremely dilute (low tens of pS/cm). The lowest specific conductance values are from ponds peripheral to or outside the deposit area. Samples with specific conductance above 89 pS/cm (upper quartile) are from ponds and ground waters within or close to the deposit area. The highest values are from borehole seeps that probably reflect a deeper ground water source. 

The lowest reported value for the specific conductance of NMA is 3.3 x 10-7 ohm-1m-1 at 40 °C16). A similar value of 5 x 10-7 ohm-1 m-1 also has been reported at 35 °C10S). While the specific conductance of absolutely pure NMA may be lower, specific conductance values in the range of those noted above represent the lowest presently attainable. 

Most of the data in the literature are given in the CGS system of units, i.e. k (called specific conductance) will be in 1 cm units. To convert a specific conductance value into an SI conductivity value, multiply by 10. ... 

Figure 10.15 shows the measured specific conductivity values as a function of 2(504)3 concentration in 2.0 M sulphuric acid solution at different temperatures. This figure shows a significant drop in the solution conductivity with the increase in vanadium (HI) sulphate content of the solution. Similar behaviour was also observed for vanadium solutions in 1.5 and 1.0 M sulphuric acid solutions. 

Figure 10.16 shows the corrected specific conductance values for vanadium sulphate solution in 2.0 M sulphuric acid at different temperatures. The corrected values show a wave-like curve however, the shape of the curve seems to differ between different temperatures. The degree of scattering in the data seems to be higher at the higher concentration range. This is most likely due to the abnormality in the viscosity behaviour especially at higher concentrations. 

The resistance due to a circular junction is given by / = /2ak, where a is the radius of the junction and k is specific conductivity of the metal. For the case of two steel plates, the measured resistance is 5 x 10" Q for a load of 50 kg the yield pressure of steel is 60 kg/mm, and the specific resistance is 5x 10 Q/cm. Calculate the number of junctions, assuming that it is their combined resistance that is giving the measured value. 

The specific conductance of the finish on the filament k is not necessarily the specific conductance it exhibits in its bulk condition. For instance, absorption of ions from the finish by the fiber can reduce the conductivity. The specific conductance greatiy depends on the amount of moisture present. Figure 4a shows the experimentally observed resistance of yam as a function of the amount of antistatic agent appHed in comparison to the calculated resistance. Below 0.05% of antistatic agent the experimental values show a lower conductivity than calculated this may be due to a lack of continuity of the antistatic agent. 

Materials are usually classified according to the specific conductivity mode, eg, as insulators, which have low conductivity and low mobihty of carriers. Metahic conductors, which include some oxides, have a high conductivity value which is not a strong (exponential) function of temperature. Semiconductors are intermediate and have an exponential temperature dependence. Figure 1 gives examples of electrical conductivities at room temperature for these various materials. 

Physical Properties. Most of the physical properties discussed herein depend on the direction of measurement as compared to the bedding plane of the coal. Additionally, these properties vary according to the history of the piece of coal. Properties also vary between pieces because of coal s britde nature and the crack and pore stmcture. One example concerns electrical conductivity. Absolute values of coal sample specific conductivity are not easy to determine. A more characteristic value is the energy gap for transfer of electrons between molecules, which is deterrnined by a series of measurements over a range of temperatures and is unaffected by the presence of cracks. The velocity of sound is also dependent on continuity in the coal. 

The proposed model of the structure of oxyfluoride melts corresponds with the conductivity results shown in Fig. 69. The specific conductivity of the melt drops abruptly and asymptotically approaches a constant value with the increase in tantalum oxide concentration. This can be regarded as an additional indication of the formation of oxyfluorotantale-associated polyanions, which leads to a decrease in the volume in which light ions, such as potassium and fluorine, can move. The formation of the polyanions can be presented as follows ... 

An electrolyte may be characterized by resistance / [Qcm], which is defined as the resistance of the solution between two electrodes at a distance of 1 cm and an area of 1 cm2. The reciprocal value is called the specific conductivity at[Q" cm"1] [5], For comparison the values of k for various materials are given in Fig. 2 Here is a wide spread for different electrolyte solutions. The selection of a suitable, high-conductivity electrolyte solution for an electrochemical cell depends on its compatibility with other components, such as the positive and negative electrodes. 

Maximum values of specific conductance are often not achievable without exceeding maximum T alkalinity values, especially in boilers below 900 psig (6.21 MPa) with greater than 20.0% MU water whose alkalinity is >20% of TDS naturally or after pretreatment by lime-soda or sodium cycle ion exchange softening. Actual permissible conductance values to achieve any desired steam purity must be established for each case by careful steam purity measurements. The relationship between conductance and steam purity is affected by too many variables to allow its reduction to a simple list of tabulated values. 

It is not usual to talk about the resistance of electrolytes, but rather about their conductance. The specific conductance (K) of an electrolyte is defined as the reciprocal of the resistance of a part of the electrolyte, 1 cm in length and 1 cm2 in cross-sectional area. It depends only on the ions present and, therefore it varies with their concentration. To take the effect of concentration into account, a function called the equivalent conductance, A, is defined. This is more commonly (and conveniently) used than the specific conductance to compare quantitatively the conductivities of electrolytes. The equivalent conductance A is the conductance of that volume of the electrolyte which contains one gram equivalent of the ions taking part in the electrolysis and which is held between parallel electrodes 1 cm apart (units ohm-1 cm4). If V cubic centimeters is the volume of the solution containing one gram equivalent, then the value of L will be 1 cm and the value of A will be V square centimeters, so that... 

If the resistance of any other electrolyte is found by measurement to be Rx when using the same conductance cell, then the specific conductance of this electrolyte is L1/ . Thus, on multiplying the value of specific conductance so obtained by V, the volume of solution in milliliters containing one gram equivalent weight of the electrolyte under investigation, the equivalent conductance A is calculated. 

A plot of the spectroscopically computed maximum ionic concentrations [SD ions]m (sum of free ions and ion-pairs) at the end of the reactions (m denotes maximum values throughout this paper, the subscript 0 denotes initial values) against the final values of the specific conductivity Km. for the equivalent runs (Tables 1 and 2) gave a straight line through the origin, showing that virtually only free ions were present in our systems if there had been important quantities of ion-pairs, this plot would have been markedly curved. 

The ionic conductivity of a solution depends on the viscosity, diffusivity, and dielectric constant of the solvent, and the dissociation constant of the molecule. EFL mixtures can carry charge. The conductivity of perfluoroacetate salts in EFL mixtures of carbon dioxide and methanol is large (10 to 10 " S/cm for salt concentrations of 0.05-5 mM) and increases with salt concentration. The ionic conductivity of tetra-methylammonium bicarbonate (TMAHCO3) in methanol/C02 mixtures has specific conductivities in the range of 9-14 mS/cm for pure methanol at pressures varying from 5.8 to 14.1 MPa, which decreases with added CO2 to a value of 1-2 mS/cm for 0.50 mole fraction CO2 for all pressures studied. When as much as 0.70 mole fraction... 

Thin membranes have the advantage of low area specific conductivities and more favorable back diffusion of water in comparison with thicker membranes. In the former case, this means that membranes with lower conductivity values could be tolerated. Analysis of voltage loss versus membrane thickness and specific conductivity has revealed that, if a membrane voltage loss of 25 mV at a current density 1 A cm can be tolerated, then existing materials with conductivity values similar to Nation (0.1 S cm i) could be prepared as 20-30 pm thick membranes. However, thinner membranes also typically exhibit lower mechanical strength than their thicker counterparts and can therefore fail earlier. Therefore, future materials might be suitable with just half the specific conductivity if they can be prepared into membranes of half the thickness and still possess sufficient mechanical strength. ... 

Aquatic chemists have defined their own electrochemical standard state to fecilitate calculation of redox speciation in aqueous solutions. In this standard state, all reactions are conducted at pH 7.0, 25°C, and 1 atm. The concentrations of all other solutes are 1 molal (unless otherwise specifically noted). Values so obtained are designated with the subscript w. The pe s for the most important redox couples in seawater are given in Table 7.4. 

For anionic surfactant, we used sodium dodecyl sulfate (SDS). The CMC values were measured by conductance method. The CMC values were taken from the breaks of curves from plots of K/C versus N 5. Where K is the specific conductance, C is molar concentration and N is the equivalence. Figure 1 shows the CMC values of SDS at 25 °C. The curve showing in the lower left side represents data taken from literature for pure SDS. The curve showing in the upper right side represents measurements for our impure sample. Table I shows some values of (dy/dC) (C-Cq) for pure SDS at 25 °C. The values for NaCl concentrations of 0.03 M to 0.50 M are not far from constant. Therefore, in this concentration region, t is also considered to be proportional to M. 

Millet determined self-diffusion coefficients for Na and Cs+ ions in hydrated 1200 EW membranes using conductivity measurements and the Einstein equation, D+ = u+kT, where u+ is the absolute mobility of the given cation. u+ can be derived from the equivalent conductivity according to A = 0+IC+ = Fu+, where 0+ is the specific conductivity, C+ is the cation concentration (calculated on the basis of the dry membrane density, EW, and the water content), and F is the Faraday constant. The values of D+ determined via these conductivity measurements... 

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