Other Theories of Thermoelectricity

As in most other branches of physics and chemistry, numerous attempts have been made to supplement the thermo- Wiedem. Ann. 34, 755 (1888). 

The thermoelectrical behaviour of many alloys is typical. Their thermoelectric potential is often much higher than that of the pure metals of which they are composed. These facts cannot be deduced from thermodynamics, which in general can tell us nothing new about constants which are characteristic of the chemical nature of substances. We must have recourse here to special theories, just as in the calculation of the osmotic pressure of solutions. We may mention that the electronic and molecular theories of R. Schenck I and A. Bernoulli J have done valuable service in this direction. 

Small quantities of liquids invariably tend to assume the spherical shape. In other words, they tend to assume, the form in which the surface for a given volume is as small as possible. The surface of a liquid therefore behaves as if it were an elastic skin, which tends to contract as much as possible. In order to increase the surface in any manner. 

K and H are constants for each liquid, i.e. they are independent of the shape of the surface. R is the radius of curvatm-e of the surface. The positive sign applies to convex, the negative to concave surfaces. The force per unit area of a plane surface (R=oo) is equal to A, and is called the internal pressure of the liquid. 

Thus all liquids tend to assume a form in which the total force attracting the surface towards the interior is a minimum. This is the case when the surface itself is a minimum in other words, when the liquid has assumed the spherical shape. Every departure from the spherical shape involves an increase in the surface, and therefore necessitates the doing of work, as particles of the liquid have to be brought from the interior to the surface against a force acting towards the interior. It is easy to show that the work done in increasing the surface of the liquid by 

---