Non-Equilibrium Processes Are Usually Complex

The topics considered up to this point have involved liquids and solutions at equilibrium. Attention is now turned to systems which are not at equilibrium, and the processes which occur spontaneously in such systems. The physical phenomena involved can be quite complex, so that the task faced in early experiments was to separate the various processes and understand the physical properties of the system which govern them. 

Consider what happens when a beaker of pure isothermal water is placed on a hot plate. The water near the bottom rises in temperature and a temperature gradient is set up. As a result heat flows from the bottom of the beaker, producing 

In this chapter, attention is focused on mass transfer processes in isothermal systems, especially in electrolyte solutions. Heat transfer is not discussed, but the methods used to treat this problem are very similar to those used to analyze diffusion problems. Chemical reactions in solutions are another example of non-equilibrium processes. These are discussed in detail in chapter 7. 

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