Direct theories Girifalco-Good and Neumann

In direct theories , the interfacial tension is expressed directly as a function of the surface tensions in some universal way, although some adjustable parameters are often needed. 

In the early method of Girifalco and Good (1957, 1960), the interfacial tension is given as  

The correction parameter p is provided in tables (Appendix 3.2) for liquid-liquid interfaces and can be calculated via the following equation using the volumes for solid-liquid interfaces  

In the more modem and widely used theory of Neumarm and co-workers (e.g. Kwok and Neumann, 1998, 1999 and 2000), the interfadal tension is 

Courtesy of the School of Engineering and Applied Sciences at State University of New York at Buffalo. 

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