Pure Substances: their Preparation, Properties, and Uses

Abstract

PROF. TIMMERMANS has chosen as a basis for his monograph on “Chemical Species” the definitions given by Wald in 1897, and used by Ostwald in 1904 in the Faraday Lecture in which he tried to show that the molecular theory had become a superfluous hypothesis in view of the rapid development of the applications of thermodynamics to chemistry. According to these definitions, a chemical compound is merely a ‘hylotropic’ substance which remains constant in composition over a range of temperatures and pressures, within which it resists all attempts at fractionation. A solution, on the other hand, may remain of constant composition when attempts are made to fractionate it by a single method, for example, by distillation under a given pressure, but generally begins to break up when a second process of fractionation is tried, for example, by fractional distillation under a different pressure, or by freezing. If, however, the material remains hylotropic and resists fractionation under all available conditions, it is classed as an element.

La notion d'espèce en chimie.

Par Prof. Jean Timmermans. Pp. iii + 134. (Paris: Gauthier-Villars et Cie, 1928.)