Conductivity of sodium chloride

Fig. 4. Modified Arrhenius diagram of the ionic conductivity of sodium chloride. Tis in Kelvin, O is in ((n-cm)...

Drawing a Conclusion How does the conductivity of sodium chloride compare with sucrose Why is this the case ... 

The conductivity of sodium chloride, hydrofluoric acid, and sugar solutions is illustrated below. 

Figure 5. Concentration dependence of equivalent conductivity, at 25°C, of SDS, an ordinary micellar solution, and aged aqueous surfactant (S). One mmol/L of surfactant (S) corresponds to 0.0405 wt %. The critical micelle concentration of SDS is 8 mmol/L. For comparison, equivalent conductivities of sodium chloride and sodium iony at infinite dilution, are shown.

Figure 18. Specific conductivity of sodium chloride soJutions...

Factor 3. The specific conductivity of sodium chloride solutions increases with concentration and temperature (Fig. 18), but is independent of pH over the range 2-11. The brine normally enters the cells at 60 - 70 °C and leaves the cells at 75 - 85 °C. The conductivity of potassium chloride solutions at 70 °C is 30% greater than that of sodium chloride solutions. Chlorine gas bubbles in the electrolyte... 

Later, Du Pont in America developed its own ionically conducting membrane, mainly for large-scale electrolysis of sodium chloride to manufacture chlorine, Nafion , (the US Navy also used it on board submarines to generate oxygen by electrolysis of water), while Dow Chemical, also in America, developed its own even more efficient version in the 1980s, while another version will be described below in connection with fuel cells. Meanwhile, Fenton et al. (1973) discovered the first of a... 

The conductivity of the environment low conductivity hinders the ionic current flow hence distilled water is less corrosive than a solution of sodium chloride with the same pH and dissolved oxygen content. 

We have, in this chapter, encountered a number of properties of solids. In Table 5-II, we found that melting points and heats of melting of different solids vary widely. To melt a mole of solid neon requires only 80 calories of heat, whereas a mole of solid copper requires over 3000 calories. Some solids dissolve in water to form conducting solutions (as does sodium chloride), others dissolve in water but no conductivity results (as with sugar). Some solids dissolve in ethyl alcohol but not in water (iodine, for example). Solids also range in appearance. There is little resemblance between a transparent piece of glass and a lustrous piece of aluminum foil, nor between a lump of coal and a clear crystal of sodium chloride. 

Some measure of control over corrosion also is obtained by limiting the salinity in the boiler (primarily the ions of sodium, chloride, and sulfate). These ions all increase the conductivity of boiler water electrolyte and thus enhance corrosion reaction rates. Also, chloride and sulfate ions affect the passivation process. 

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]. 

The electrolyte is made by in situ chlorination of vanadium to vanadium dichloride in a molten salt bath. Higher valent chlorides are difficult to retain in the bath and thus are not preferred. The molten bath, which is formed by sodium chloride or an equimolar mixture of potassium chloride-sodium chloride or of potassium chloride-lithium chloride or of sodium chloride-calcium chloride, is contained in a graphite crucible. The crucible also serves as an anode. Electrolysis is conducted at a temperature about 50 °C above the melting point of the salt bath, using an iron or a molybdenum cathode and a cathode current density of 25 to 75 A dnT2. The overall electrochemical deposition reaction involves the formation and the discharge of the divalent ionic species, V2+ ... 

The high ionic conductivity of sodium (3"-alumina suggested that it would form a suitable electrolyte for a battery using sodium as one component. Two such cells have been extensively studied, the sodium-sulfur cell and the sodium-nickel chloride (ZEBRA) cell. The principle of the sodium-sulfur battery is simple (Fig. 6.13a). The (3"-alumina electrolyte, made in the form of a large test tube, separates an anode of molten sodium from a cathode of molten sulfur, which is contained in a porous carbon felt. The operating temperature of the cell is about 300°C. 

The electrical conductance of liquid water is very low compared with the values given by solutions of ionic compounds. Typically, the conductance of a I mol dm-3 solution of sodium chloride is about one... 

The anodes were made of thin sheets of platinum held in a non-conducting frame between the zinc discs. Sea water was early used as an electrolyte, and later a 5 per cent. soln. of sodium chloride with about one per cent, of magnesium chloride. The electrolyte was kept m circulation by means of a special pump. 

Sodium chloride is plentiful as rock salt, but the solid does not conduct electricity, because the ions are locked into place. Sodium chloride must be molten for electrolysis to occur. The electrodes in the cell are made of inert materials like carbon, and the cell is designed to keep the sodium and chlorine produced by the electrolysis out of contact with each other and away from air. In a modification of the Downs process, the electrolyte is an aqueous solution of sodium chloride. The products of this chloralkali process are chlorine and aqueous sodium hydroxide. 

The alkali metal hydrides contain alkali metal cations and H- anions in a face-centered cubic crystal structure like that of sodium chloride (Section 10.9). Alkali metal hydrides are also ionic in the liquid state, as shown by the fact that the molten compounds conduct electricity. 

Another troublesome borderline area is that between ionic solids and three-dimensional polymers. The distinction cannot be made from the structure alone. Electrical conductivity in the molten state does not, as already mentioned, necessarily demonstrate the presence of ions in the solid state and such a test is inapplicable where, as often happens, the substance sublimes or decomposes before melting. There can rarely be any objective means of assigning a compound to one category or the other. We are often persuaded towards one description on aesthetic grounds. For example, the structure of sodium chloride cannot easily be rendered in terms of localised, electron-pair bonds (but this is true also of many unequivocally covalent compounds). Its structure is eminently plausible for an array of cations and anions, however. 

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