Thermal Loosening of an Ionic Lattice

ISome Differentiating Features of Ionic Liquids (Pure Liquid Electrolytes) 

A common type of ionic lattice is that of a crystalline salt. One such ionic lattice encountered in everyday life is sodium chloride. Molten sodium chloride is a typical liquid electrolyte and displays the characteristics of many liquid electrolytes.  

An appreciation of the properties of liquid electrolytes can be gained by a comparison between molten ice (water) and molten sodium chloride (Table 5.2). Both liquids are clear and colorless. Their viscosities, thermal conductivities, and surface tensions near their melting points are not very different. 

In fact, one can go further and make the following statement Molten salts look like water and not far above their melting points have viscosities, thermal conductivities, and surface tensions on the same orders ofmagnitude as those of water. In general, however, and with the important exception of some AlClj-complex organic systems, most fused salts are stable as liquids only at relatively high temperatures (500 to 1300 K) (Table 5.3). 

One can quote exceptions to these generalizations. The tetraalkylammonium salts as a class are liquid at temperatures below 300 K. There are liquid electrolytes— produced from dissolving AICI3 into some complex organics—which are liquid at room temperature (Tables 5.3 and 5.4). Above the normal range of 300-1300 K is another set of molten electrolytes, the molten silicates, borates, and phosphates, for which the characteristic temperature range is 1300-2300 K (Tables 5.5 and 5.6). 

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