J.H. van ’t Hoff en de fasenleer

Abstract

J.H. van 'I Hoff and the phase rule After Josiah Willard Gibbs had published his phase rule in 1876, ii was the Leiden physical chemist Hendrik Willem Bakhuis Roozeboom (1854-1907) who used systematically Gibbs's phase rule in his studies on heterogeneous equilibria. He was mainly responsible for the introduction of the phase rule into European chemistry and he founded a school of phase chemists in The Netherlands, In his Etudes de dynamique chimique (1884) Jacobus Henricus van 't Hoff (1852-1911) distinguished between chemical en physical equilibria, which he divided into homogeneous, heterogeneous and condensed systems. The latter were systems in which none of the phases possesses variable composition. Van 't Hoff recognized that condensed systems don't have a continual displacement of the equilibrium. There is a transition temperature such that one of the systems is stable above that point, the other below. In the Etudes Van 't Hoff enunciated his "law of the incompatibility of condensed systems", which is a special case of the phase rule. In his Amsterdam years (1877-1895) Van 't Hoff studied with his assistants and students transition temperatures for chemical decompositions (as hydrates and double salts). In Berlin (1896-1911) he carried out, in cooperation with Wilhelm Meyerhoffer (1864-1906) and 29 co-workers, his classical investigations of the Stassfurt salt deposits from the point of view of his law of the incompatibility of condensed systems (1896-1908). Van 't Hoff did not use Gibbs's phase theory and phase rule, mainly because of the abstract mathematical apparatus Gibbs used. Besides he found use of the phase rule superfluous because his method of studying condensed systems led to the same results. This attitude was wholly contrary to Bakhuis Roozeboom's who from 1887 onwards applied the phase rule successfully to the classification and study of heterogeneous equilibria and who showed its heuristic value.