Introduction

This website gives exposure to highly significant work performed in the Netherlands around 1900 on phase separation and critical behavior of fluids and fluid mixtures. These substances may exist in several different phases: vapor and one or more liquid phases. In addition fluids can transform into one or more solid phases. A characteristic feature of the vapor-liquid phase transition in one-component (or pure) fluids is that it occurs only if the temperature is below a certain temperature called critical, which differs from fluid to fluid. In 1873 the physicist Johannes Diderik van der Waals (1837-1923) published what is known as the Van der Waals equation, which yields a vapor-liquid phase transition as well as a critical point.

The phase separation of even only two-component fluid mixtures is considerably more complicated than that of pure fluids. Two-component mixtures have critical curves instead of critical points. Fluid mixtures may have liquid-liquid phase separation in addition to vapor-liquid separation. Some mixtures can separate into two phases of different density and composition even above the critical temperatures of both components.

Phase separation of fluids is a topic of major practical interest, for instance, in the chemical and materials processing industries, as well as in geochemistry, oil and gas recovery, and metallurgy. The thermodynamic foundation of the field was laid between 1873 en 1878 by the U.S. chemist Josiah Willard Gibbs. In the late 19th century, Dutch physicists and chemists, and even one mathematician, were leaders in the development of the field. Many of their early discoveries have become common knowledge, others have been forgotten, and were gradually rediscovered in the 20th century.

This site consists of three parts. The first part, Scientists of the Dutch School, introduces seven selected scientists within the context of their work. For each of these scientists, the site presents biographical information and references to a few important publications. In addition, one or more representative articles can be accessed in full. Each of those articles is accompanied by an abstract, containing a rationale for its inclusion and a concise description of its context and significance. The second part, 3D-models presents pictures of a collection of three-dimensional models constructed by Kamerlingh Onnes and his students for representing phase separation in pure fluids and in fluid mixtures. It includes explanations of the thermodynamic principles underlying these models. It contains the papers describing the construction of the models, as well as references to the theoretical and experimental work on which the models are based. The third part presents access to How Fluids Unmix, a recent book published by Edita KNAW on the history of the School of Van der Waals and Kamerlingh Onnes.

Johanna Levelt Sengers prepared the textual material for this site.