Electrolytes specific conductivity

The measured electrolyte specific conductivity has a contribution due to the solvent conductivity. In the case of aqueous systems, the self-dissociation of water contributes in 0.055 j.S cm at 25 °C, but increases at higher temperatures and pressures due to the increase in K and the mobility of the and HO" ions. The ion product of water up to... 

In the sodium—sulphur battery, patented by Ford, for example, instead of solid electrodes separated by a liquid electrolyte (as in the conventional lead—acid car battery, for example), sodium alumina is used as a solid electrolyte, specifically conducting sodium ions between liquid electrodes of sodium metal and sulphur (Figure 29.1). 

See chemical equivalent, equivalent conductivity The specific conductance multiplied by the volume (ml) which contains 1 g equivalent of the electrolyte. 

Conductivity. The standard unit of conductance is electrolytic conductivity (formerly called specific conductance) k, which is defined as the reciprocal of the resistance of a 1-m cube of liquid at a specified temperature m— ]. See Table 8.33 and the definition of the cell constant. 

C), (cmVohm geqmv) K = Ci/R = specific conductance, (ohm cm) h C = solution concentration, (gequiv/ ) Ot = conductance cell constant (measured), (cm ) R = solution electrical resistance, which is measured (ohm) and/(C) = a complicated function of concentration. The resulting equation of the electrolyte diffusivity is... 

The propionamide can be dried over CaO. H2O and unreacted propionic acid were removed as their xylene azeotropes. It was vacuum dried. Material used as an electrolyte solvent (specific conductance less than 10 ohm cm" ) was obtained by fractional distn under reduced pressure, and stored over BaO or molecular sieves because it readily absorbs moisture from the atmosphere on prolonged storage. [Hoover Pure Appl Chem 37 581 I974 Recommended Methods for Purification of Solvents and Tests for Impurities, Coetzee Ed., Pergamon Press, 1982.]... 

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. 

The most spectacular feature of a conductivity-concentration function is its maximum, attained for every electrolyte if the solubility of the salt is sufficiently high. For electrolytes which do not show strong ion association, the maxima can be understood on the basis of the defining equation of specific conductivity at the maximum [205], yielding... 

Electrolytes are highly important components of all galvanic cells and electrochemical devices. In most electrochemical devices, such as electrolyzers, batteries, and the like, aqueous solutions of acids and salts are used as electrolytes. Aqueous solutions are easy to prepare, convenient to handle, and as a rule are made from readily available, relatively inexpensive materials. By changing the composition and concentration of the components, it is relatively easy to adjust the specific conductance and other physicochemical properties of these aqueous solutions. 

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... 

As in the case of solutions, the specific conductance, K, the equivalent conductance, a, and the molar conductance, am, are also distinguished for molten electrolytes. These are defined in the same manner as done for the case of solutions of electrolytes. It may, however, be pointed out that molten salts generally have much higher conductivities than equivalent aqueous systems. 

From the measurements made on the bridge wire, the resistance X of the electrolyte in solution is determined by the relationship given above. Therefore, the conductance of the solution (1 /X) will also be known. The specific conductance, K, of the solution is related to the conductance of the solution thus determined by the equation ... 

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. 

Molten sulphides are almost invariably semiconductors, and so their conductivities are typically larger than those of the average molten electrolyte. For example, the specific conductance of molten Ag2S can be described, as a function of temperature by the equation... 

The CE behaviour of inorganic anions in water-methanol mixtures has also been extensively studied. The specific conductivity a of electrolytes was converted into equivalent conductivity by... 

The tape casting and electrophoretic deposition processes are amenable to scaleup, and thin electrolyte structures (0.25-0.5 mm) can be produced. The ohmic resistance of an electrolyte structure and the resulting ohmic polarization have a large influence on the operating voltage of MCFCs (14). FCE has stated that the electrolyte matrix encompasses 70% of the ohmic loss (15). At a current density of 160 mA/cm, the voltage drop (AVohm) of an 0.18 cm thick electrolyte structure, with a specific conductivity of -0.3 ohm cm at 650°C, was found to obey the relationship (13). 

Electrolyte structures containing 45 wt% LiA102 and 55 wt% molten carbonate (62 mol% Li2C03-38 mol% K2CO3) have a specific conductivity at 650°C of about 1/3 that of the pme carbonate phase (14). 

There is a potential drop V across the solution between the layer around the working electrode and the tip of the reference probe. This is related to the separation distance d by Equation 1.3 where i is the current flowing through the cell and K is the specific conductivity of the electrolyte. Tire reference electrode probe is... 

The examination of the electrolytic conductivity of soap solutions has, however, indicated that they are relatively good conductors and the conductivity concentration curve exhibits the interesting property of a definite minimum. The values for the specific conductivity of potassium palmitate are (McBain and Martin, J.G.S. ov. 967, 1914) plotted in the following curve. 

If both sides of Eq. (6.302) are divided by the specific conductivity <7 of the electrolyte, it is clear that... 

If one divides both sides by the specific conductivity of the electrolyte, one gets an atomistic expression for the streaming potential [see Eq. (6.302)],... 

The Fuoss-Onsager-Skinner equation satisfactorily describes the electrolytic conductance of lithium bromide in acetone. Values of 198.1 0.9 Q l cm2 eq l and (3.3 0.1) X I03 are established for A0 and KA, respectively, at 25°C furthermore, a value of 2.53 A is obtained for the sum of the ionic radii ( ). When bromosuccinic acid is added to 10 5 N lithium bromide in acetone, there is a decrease in the specific conductance of lithium bromide rather than the increase that is observed at higher concentrations. As the concentration of bromosuccinic acid is increased, the values obtained for A0 and KA decrease, while those for a increase when the bromosuccinic acid and acetone are considered to constitute a mixed solvent. These results do not permit any simple explanation. When bromosuccinic acid and acetone are considered a mixed solvent, the Fuoss-Onsager-Skinner theory does not describe the system. 

Review of the conductivity of solutions - the conductance G measured between two electrodes of area A and spacing d inserted into a conducting medium is the reciprocal of resistance R. G = 1 // is expressed in siemens (S). For a given ion, the conductance of the solution will vary with the concentration of the electrolyte. This relationship is linear for very dilute solutions. The specific conductance (in S mol 1) or conductivity k allows the measure to be independent of the detection cell ... 

Some remarks are necessary on the purity of chemicals. Ionic impurity causes a flow of electric current through polymerizing solution. This is certainly undesirable because it may give rise to a temperature rise and because it may trigger electrolytic reactions on the electrodes, which would screen the effect looked for. Thus, the solvents and monomers were most carefully purified. The impurity level was checked by the electric conductivity determined from the current and field intensities before polymerization. For example, 1,2-dichloroethane, the solvent most frequently used in our investigations, was purified until its specific conductivity was lowered below 1010 mho/cm. It should be mentioned... 

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