Electrical resistance of solution

Fig. 25.—Effect of Pressures on the Electrical Resistance of Solutions of Sodium Chloride.

Fig. 26.—Effect of Pressure on the Electrical Resistance of. -solutions of the Alkali Halides.

Commercial IX membranes have thicknesses of ca 0.15—0.5 mm and electrical resistances of ca 3-20 H-cm at 25°C when in equiUbrium with 0.5 W sodium chloride. The electrical resistances are somewhat higher in more dilute solutions because co-ions are more effectively excluded from the membrane by the IX resin. The electrical resistance decreases with increasing temperature at a rate of ca —1.9%/°C. The electrical resistance of an ED apparatus... 

In concentrated electrolytes the electric current appHed to a stack is limited by economic considerations, the higher the current I the greater the power consumption W in accordance with the equation W = P where is the electrical resistance of the stack. In relatively dilute electrolytes the electric current that can be appHed is limited by the abflity of ions to diffuse to the membranes. This is illustrated in Eigure 4 for the case of an AX membrane. When a direct current is passed, a fraction (t 0.85-0.95) is carried by anions passing out of the membrane—solution interface region and... 

For the electrolysis of a solution to be maintained, the potential applied to the electrodes of the cell (Eapp ) must overcome the decomposition potential of the electrolyte (ED) (which as shown above includes the back e.m.f. and also any overpotential effects), as well as the electrical resistance of the solution. Thus, Eapp must be equal to or greater than (ED + IR), where / is the electrolysis current, and R the cell resistance. As electrolysis proceeds, the concentration of the cation which is being deposited decreases, and consequently the cathode potential changes. 

We did not feel any of these methods would work reliably on a commercial scale at current densities in the range of 300 mA cm"2 or for commercial periods (at least 4000 hr). Rudge s work9,10 with porous carbon anodes was a very elegant solution to the problem (and formed the basis for the Phillips Electrochemical Fluorination process), but the high electrical resistance of the porous carbon limited it to small anodes at high current densities or lower current densities on large anodes. 

Archie [23] examined electrical resistivity of various sand formations having pore spaces filled with saline solutions of different salt concentrations. Based upon his own experimental results, he obtained a simple relationship for the conductivity of beds of sand (assuming the sand itself is nonconductive) containing saline solution in terms of the porosity. In terms of diffusion coefficients his expression is... 

With application of positive current, the entire potential shifted to much more negative values and with positive current, to more negative values. These shifts should be the result of ohmic drop induced by electrical resistance of the octanol solution. 

Since water as solvent plays the role of a medium where electrolytic displacements take place we shall be able to state for sure, together with Wiedemann, Beetz and Quincke, that the electrical resistance of a solution consists of resistances to movement enforced upon the components of the solution by water particles, by the components themselves and perhaps by the undecomposed molecules of the electrolyte. To separate these various hindrances will be no easy task, particularly because, as stressed by Quincke, they are not necessarily constant but can, for example, depend on the condition of the solution. Even from this standpoint the process of conduction will be, in general, still very complicated. 

Figure 5.18. Relationship between white phosphorus concentration of the starting solutions and electrical resistivity of resulting doped-Si films. [Reproduced with permission from Ref. 25. Copyright 2007 The Japan Society of Applied Physics.]...

The voltage drop across a working electrochemical cell is not uniformly distributed. This is shown schematically in Figure 1.2. A large proportion a due to the electrical resistance of the electrolyte and the separator. This, of course, can be decreased by a suitable cell design. The voltage drop across the working electrode solution interface determines the rate constant for the electrochemical reaction. It is... 

The problem of gas bubbles is to be added to the resistive effect of mechanical separators [12-14]. H2 and O2 are formed at the surface of the electrodes facing the separator. Hence the solution between electrode and diaphragm becomes saturated with gas bubbles that reduce the volume occupied by the electrolyte, thus incrementing the electrical resistance of the solution. In the conventional cell configuration, IR can be minimized, once the electrolyte and the separator are fixed, only by minimizing the distance between the anode and cathode. However, a certain distance between the electrode and separator must be necessarily maintained. 

Experimentally, AT is determined for approx, five different polymer concentrations. After several minutes, a constant temperature difference AT of the two drops is reached which is proportional to their initial difference in vapor pressure and thus proportional to the number of dissolved macromolecules in the solution drop. AT can then be determined by measuring the difference in electric resistance of the two thermistors. Then, ATIKc is plotted vs. c (thus the power law series is broken after the linear term in c) and the plotted values are extrapolated to c 0. Mj, is finally calculated from they axis intercept. 

Energy losses in soft magnetic materials arise due to both hysteresis and eddy currents, as described in the previous section. Eddy current losses can be reduced by increasing the electrical resistivity of the magnetic material. This is one reason why solid-solution iron-silicon alloys ( 4% Si) are used at power frequencies of around 60 Hz and why iron-nickel alloys are used at audio frequencies. Some magnetically soft ferrites (see Section 6.2.2.1) are very nearly electrical insulators and are thus immune to eddy current losses. Some common soft magnetic materials and their properties are listed in Table 6.19. Soft magnetic alloys are described further in Section 6.2.1.6. 

The electrical resistivity of the films (between 0.1 and 0.25 p.m thick), measured through Au contacts, was ca. 2.5 kfl/sq (ca. 5 X 10 fl-cm). This value increased with air-annealing (250°C, 20 min) up to 60 kfl/sq. The relatively low resistivity was attributed to incorporation of S, either from the Cu cS prelayer or by hydrolytic decomposition of 8203 to S . Treatment of the films with NaiS solution decreased the resistivity by nearly two orders of magnitude, and S was found in the films. It is likely that the surface of the CuiO crystals was partially... 

Figure 5.38 shows an electrolyte solution between two plane electrodes. The conductivity of the solution (ic) is expressed by k=L/AR, where L is the distance between the two electrodes (cm), A the electrode area (cm2), and R the electrical resistance of the solution (fi). For dilute electrolyte solutions, the conductivity k is proportional to the concentrations of the constituent ions, as in Eq. (5.39) ... 

The electrical resistance of non-aqueous electrolytic solutions is often much higher than that of aqueous ones, and so polarographic and voltammetric measurements in non-aqueous solutions should be made with a three-electrode device. A computer-aided three-electrode instrument, equipped with a circuit for iR-drop compensa-... 

The specific electrical resistance of an electrolyte solution is defined as the resistance of a cube 1 cm in length and 1 cm2 in cross-sectional area. 

Electrolytic resistivity tthe reciprocal of conductivity is similarly defined as the electrical resistance of a unit cuhe of solution, h is expressed in the same units as electrical resistivity, i.e.. ohms times u unit of length. Most commonly we find ohm-cin (J2-cml and ohm-meter (fi-m) ... 

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