Sodium chloride electrical conductivity

The liquid film (water) is brought onto the filament with the help of very small, micrometer-sized water droplets. These droplets are generated in a Venturi nozzle (Fig. 9-10). To avoid electrostatic charging of the sur ce, a supporting salt is usually added that fiidlitates electrical conductivity. If sodium chloride is used as a support-... 

We can divide the substances that dissolve in water into two broad classes, electrolytes and nonelectrolytes. An electrolyte is a substance that dissolves in water to give an electrically conducting solution. Sodium chloride, table salt, is an example of an electrolyte. When most ionic substances dissolve in water, ions that were in fixed sites in the crystalline solid go into the surrounding aqueous solution, where they are liee to move about. The resulting solution is conducting because the moving ions form an electric current Thus, in genraal, ionic solids that dissolve in water are electrolytes. 

Ionic bonding was proposed by the German physicist Walther Kossel in 1916 in or der to explain the ability of substances such as molten sodium chloride to conduct an electric current He was the son of Albrecht Kossel winner of the 1910 Nobel Prize in physiology or medi cine for early studies in nu cleic acids... 

Thus we find great variation among solutions. Iodine dissolves in ethyl alcohol, coloring the liquid brown, but does not dissolve readily in water. Sodium chloride does not dissolve readily in ethyl alcohol but does dissolve in water, forming a solution that conducts electric current. Sugar dissolves readily both in ethyl alcohol and in water, but neither solution conducts electric current. These differences are very important to the chemist, and variations in electrical conductivity are among the most important. We shall investigate electrical conductivity further but, first, we need to explore the electrical nature of matter. 

Water is a very poor conductor of electricity. Yet when sodium chloride dissolves in water, the solution conducts readily. The dissolved sodium chloride must be responsible. How does the dissolved salt permit charge to move through the liquid One possibility is that when salt dissolves in water, particles with electric charge are produced. The movement of these charged particles through the solution accounts for the current. Salt has the formula, NaCl—for every sodium atom there is one chlorine atom. Chemists have... 

Sugar dissolves in water, but the resulting solution conducts electric current no better than does pure water. We conclude that when sugar dissolves, no charged particles result no ions are formed. Sugar must be quite different from sodium chloride. 

Calcium chloride, CaCl2, is another crystalline solid that dissolves readily in water. The resulting solution conducts electric current, as does the sodium chloride solution. Calcium chloride is, in this regard, like sodium chloride and unlike sugar. The equation for the reaction is... 

When we study a solid that does not have the characteristic lustrous appearance of a metal, we find that the conductivity is extremely low. This includes the solids we have called ionic solids sodium chloride, sodium nitrate, silver nitrate, and silver chloride. It includes, as well, the molecular crystals, such as ice. This solid, shown in Figure 5-3, is made up of molecules (such as exist in the gas phase) regularly packed in an orderly array. These poor conductors differ widely from the metals in almost every property. Thus electrical conductivity furnishes the key to one of the most fundamental classification schemes for substances. 

Referring to Tables 5-1 and 5-II, we find that both sodium chloride and copper have extremely high melting and boiling points. These two solids have little else in common. Sodium chloride has none of the other properties that identify a metal. It has no luster, rather, it forms a transparent crystal. It does not conduct electricity nor is it a good heat conductor. The kind of forces holding this crystal together must be quite different from those in metals. 

When an ionic solid like sodium chloride is melted, the molten salt conducts electric current. The conductivity is like that of an aqueous salt solution Na+ and Cl- ions are present. The extremely high melting temperature (808°C) shows that a large amount of energy is needed to tfear apart the regular NaCl crystalline arrangement to free the ions so they can move. 

Molten lithium fluoride and sodium chloride have easily measured electrical conductivities. Nevertheless, these conductivities are lower than metallic conductivities by several factors of ten. Molten sodium chloride at 750°C has a conductivity about IQ-5 times that of copper metal at room temperature. It is unlikely that the electric charge moves by the same mechanism in molten NaCl as in metallic copper. Experiments show that the charge is carried in molten NaCl by Na+ and Cl- ions. This electrical conductivity of the liquid is one of the most characteristic... 

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]. 

Sodium chloride is plentiful as the mineral rock salt, but the solid does nor conduct electricity, because the ions are locked into place. Sodium chloride must be molten... 

In contrast to sugar, solid sodium chloride dissolves in water to give a liquid that conducts electricity. Figure 3-19 shows that a solution of NaCl is a good conductor. When an ionic compound dissolves in water, its component cations and anions are free to move about in the solution. Mixing leads to a uniform distribution of Na and Cl ions through the entire solution, with each ion surrounded by a sheath of water molecules as shown in Figure 3-20. 

The presence of ions in solution is what gives a sodium chloride solution the ability to conduct electricity. If positively and negatively charged wires are dipped into the solution, the ions in the solution respond to the charges on the wires. Chloride anions move toward the positive wire, and sodium cations move toward the negative wire. This directed movement of ions in solution is a flow of electrical current. Pure water, which has virtually no dissolved ions, does not conduct electricity. Any solution formed by dissolving an ionic solid in water conducts electricity. Ordinary tap water, for example, contains Ionic Impurities that make It an electrical conductor. 

The ions that conduct the electrical current can result from a couple of sources. They may result from the dissociation of an ionically bonded substance (a salt). If sodium chloride (NaCl) is dissolved in water, it dissociates into the sodium cation (Na+) and the chloride anion (CL). But certain covalently bonded substances may also produce ions if dissolved in water, a process called ionization. For example, acids, both inorganic and organic, will produce ions when dissolved in water. Some acids, such as hydrochloric acid (HC1), will essentially completely ionize. Others, such as acetic acid (CH3COOH), will only partially ionize. They establish an equilibrium with the ions and the unionized species (see Chapter 13 for more on chemical equilibrium). 

Electrolytes. A substance chat will easily disassociate into ions when put into solution (generally water) and will conduct, electricity. Sulfuric acid and sodium chloride are favorite media for electrolysis. 

Three gradients of 0.0-0.5 M sodium chloride were run consecutively at 4°C in 0.05 M sodium acetate-acetic acid, 1 mM sodium azide, pH 5.25, followed by 0.05 M sodium acetate-acetic acid, 1 mM sodium azide, pH 3.5, and finally by 0.05 M sodium dihydrogen phosphate-disodium hydrogen phosphate (approx. 1 3), 1 mM sodium azide, pH 7.0. After sample application, the column was washed with the starting buffer to remove any non-bound compounds. Elution was continued with the high salt buffer. Fractions of 4 ml were collected and assayed for reactivity towards ninhydrin and for electric conductivity (salt concentration) after 75-fold dilution of a 100-pl aliquot. Ninhydrin-positive fractions were pooled for each peak, concentrated, and desalted by size exclusion chromatography (see above). 

INTESTINE Characterization of a membrane potassium ion conductance in intestinal secretory cells using whole cell patch-clamp and calcium-sensitive dye techniques, 192, 309 isolation of intestinal epithelial cells and evaluation of transport functions, 192, 324 isolation of enterocyte membranes, 192, 341 established intestinal cell lines as model systems for electrolyte transport studies, 192, 354 sodium chloride transport pathways in intestinal membrane vesicles, 192, 389 advantages and limitations of vesicles for the characterization and the kinetic analysis of transport systems, 192, 409 isolation and reconstitution of the sodium-de-pendent glucose transporter, 192, 438 calcium transport by intestinal epithelial cell basolateral membrane, 192, 448 electrical measurements in large intestine (including cecum, colon, rectum), 192, 459... 

Figure 6.29 Diffusion coefficient measured directly (open circles) and calculated from electrical conductivity data (closed circles) for Na+ in sodium chloride. From W. D. Kingery, H. K. Bowen, and D. R. Uhhnann, Introduction to Ceramics. Copyright 1976 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc.

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... 

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