Determination of surface parameters

The values of y and ct for various types of surface are necessary for quantitative application of the thermodynamic relationships developed in Section 2.2.3. These values may be obtained by three approaches. 

Direct experimental measurement. There are various techniques for measuring y for surfaces and interfaces. Most of these techniques will be described in subsequent chapters after the phenomena which underlie the measurements have been described. The techniques for measuring a are rather limited. Selected results of experimentally determined values of y and a will be presented in Section 2.2.5.1. 

Theoretical calculation. Various theoretical methods may be used for calculation of both y and a. The results of several techniques will be described in Section 2.2.5.2. 

Extrapolation using other physical properties. The nature and strength of the bonds between atoms determine not only the values of y but also a number of other physical properties. Therefore, there is a correlation between y and these properties. Such correlations are not generally available for the determination of a. 

Liquids Since y and a are numerically equal for liquids, only the determination of y is necessary. There are various techniques for measuring y for liquids. These include the capillary-rise, sessile-drop, pendant-drop, drop-weight and maximum-bubble-pressure techniques. Several of these techniques will be described in Chapters 3 and 6. Table 2.1 presents typical values for the surface energies of various types of liquids. 

---