Jouguet-de Donder

But it will be seen that theory allows the number of equations for the reactions which are strictly necessary to describe the chemical system precisely to be defined in a rigorous way, when the nature and the number of the constituents to be taken into account are themselves well-defined. The theory therefore provides the necessary and sufficient number of chemical variables (or JOUGUET-de DONDER variables) and equations to calculate the composition of the reaction mixture during the transformation. In particular, these equations can be applied to chemical equilibria. 

Of course, De Donder was not the only thermodynamicist who was interested in nonequilibrium conditions at this time. The work of the French school, notably Duhem and Jouguet, and the Cracow school with Natanson should also be recalled. (A short survey of the history can be found in my Etude Thermodynamique des Phinomines Irreversibles, De-soer, Liege, 1947.) However, his contributions to the introduction of the degree of advancement and of affinity are now classical. 

As is shown in Table 1, the first step in the analysis of experimental results consists of describing the reaction system by a set of stoichiometric equations. Concepts associated with the word stoichiometry can be found in the pioneering works of De Donder [39], Jouguet [40] and Brinkley [41]. A considerable amount of literature about stoichiometry has appeared in recent years and the corresponding references are listed in a paper by Smith and Missen [42]. A general discussion of stoichiometric problems is given by Aris [23]. 

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