Peltier effects in electrode carbon

The thermoelectric power of a cell with platinum electrodes and a carbon conductor was determined. The electromotive force (emf) was measured as a function of the temperature difference between the electrodes at temperatures varying from 310 degrees C to 970 degrees C. From these measurements, the transported entropy of electric charge in carbon was found to vary from -1.7 to -1.9 J/(K mole) at temperatures around 300 degrees C, from -2.0 to -2.3 J/(K mole) at temperatures around 550 degrees C, and from -3.4 to -3.7 J/(K mole) at temperatures around 950 degrees C. This transported entropy had not before been determined for temperatures above 550 degrees C. Also, it is shown how the previously neglected surface properties can be taken into account to interpret the measurements. In the Hall-Heroult cell, the anode is made of a similar kind of carbon. Hence, the transported entropy found above can be used to describe the often neglected coupling between transport of heat and electric charge in this electrode. It is shown that the calculated electric potential profile through a coal sample will change significantly if the coupling is neglected, but the calculated temperature profile is independent of whether the coupling is neglected. New equations are also developed that can be used to evaluate the importance of the coupling in other systems.