par Pourbaix, Marcel 
;Rorive-Bouté, C.M.
Référence Discussions of the Faraday Society, 4, page (139-154)
Publication Publié, 1948
;Rorive-Bouté, C.M.Référence Discussions of the Faraday Society, 4, page (139-154)
Publication Publié, 1948
Article révisé par les pairs
| Résumé : | An examination is made of some properties of the diagrams of complex equilibria constructed by plotting the inverse of the absolute temperature as abscissa and the logarithm of the equilibrium oxygen pressures of all the transformations which can occur in the system as ordinate. At all points in these diagrams the slope of the tangents of the isobars are a measure of the quotient Q/n, where Q is the heat content change of the sum of all the reactions simultaneously possible, and n the number of g. mol. oxygen needed by the system for these reactions . At the points where these tangents are horizontal, the total heat content of the reaction is zero: the quantities of substances taking part in the various reactions are such that the sum of the heat evolved by the exothermic reactions is equal to that absorbed by the endothermic reactions. At the points where these tangents are vertical, the sum of the reactions occurs without the exchange of oxygen with the surroundings of the system: the quantities of substances taking part in the various reactions are such that the quantity of oxygen liberated by the reduction reactions is equal to that combining in the oxidation reactions; it is particularly at these points where the tangents are vertical that the heterogeneous systems of practical interest are represented. The variance of the physico-chemical systems whose equilibrium characteristics are represented in these diagrams can readily be deduced from a rapid examination of them. A few examples are given from the systems: zinc-oxygen, carbon-oxygen and zinccarbon-oxygen. |
