Principle of the pole diagram

1 See Volume 6 of this Set of books. Electrolytes and Electrochemical Thermodynamics. 

If we perform the reaction at a temperature T which is higher than T, two cases may arise  

This time, we reach point E , with abscissa Rln fiT E The reaction now runs along the segment TE . 

at the new temperature T, the state of aggregation of a component is no longer the same as at T in the standard state, meaning that this component has undergone a phase transformation (written as t) between the temperatures T and T. We therefore need to define a new pole P  

However, the difference A /z -A /z represents the enthalpy A /z° accompanying the phase change of the component in question between P and P . Similarly, the difference A 5°-A 5 represents the opposite of entropy associated with the same transformation. The slope of the straight line PP is therefore given by the opposite of the ratio of the enthalpy of phase change of the compound involved to the corresponding entropy  

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