World of Physics on Johannes Diderik van der Waals
Johannes Diderik van der Waals received his doctorate in physics from the University of Leiden at the relatively late age of thirty-six. His doctoral dissertation, "On the Continuity of Gaseous and Liquid States," quickly became known among his colleagues and made his reputation almost immediately. The Nobel Prize in physics, awarded him in 1910, recognized the line of work begun in his dissertation, eventually resulting in a famous equation of state relating the pressure, volume, and temperature of a gas . He also demonstrated why a gas cannot be liquified above its critical temperature. Van der Waals also investigated the weak nonchemical bond forces between molecules that now carry the name van der Waals forces.
Van der Waals was born in Leiden in the Netherlands on November 23, 1837. His parents were Jacobus van der Waals, a carpenter, and the former Elisabeth van den Burg. Van der Waals attended local primary and secondary schools and then took a job teaching elementary school in his hometown. In 1862 he began taking courses at the University of Leiden and, two years later, received the credentials necessary to teach high school physics and mathematics. He then accepted a job teaching physics in the town of Deventer and, a year later in 1866, became headmaster of a secondary school in Hague.
During his year at Deventer, van der Waals married Anna Magdalena Smit, who bore him three daughters, Anne Madeleine, Jacqueline Elisabeth, and Johanna Diderica, and one son, Johannes Diderik. Biographers note that Anna Magdalena died while the children were still very young; Van der Waals never remarried.
While in Hague, van der Waals continued to attend the University of Leiden on an informal basis. Since he had never studied Greek and Latin in high school, he was not allowed by federal law to enroll in a doctoral program. When that regulation was abolished in the late 1860s, van der Waals was admitted as a regular graduate student at Leiden. For his dissertation he chose to study the nature and behavior of the particles that make up gases and liquids.
Van der Waals's choice of topics, he later said, was strongly influenced by a paper written by the German physicist Rudolf Clausius in 1857. In that paper Clausius had argued that the molecules of a gas can be considered tiny points of matter in constant motion. From this initial premise, Clausius was able to derive theoretically a law relating gas pressure and volume originally stated empirically by Robert Boyle in 1662. It occurred to van der Waals that the molecules of both gases and liquids might be considered in the same way, as tiny points of matter. In such a case, according to van der Waals, there might be no fundamental difference between gases and liquids, the latter being only compressed gas at a low temperature.
It was this concept that van der Waals explored in detail in his doctoral thesis, presented to the faculty at Leiden in 1873. He pointed out that two fundamental assumptions of earlier gas laws were not valid. In the first place, such laws had assumed that the particles of which a material is made had no effective size. Van der Waals argued that they did have measurable volume and that such volume affected the behavior of a gas. A second assumption of gas laws was that gas particles do not interact with each other. Van der Waals argued instead that particles do indeed exert forces on each other.
Given these modifications in starting assumptions, van der Waals was able to develop an equation that more closely matches the actual behavior of gases. Laws such as those of Robert Boyle and Jacques C´esar Charles had been regarded as correct for "ideal" gases, but always failed to some extent when applied to any real gas. Under van der Waals's formulation, the revised gas law applied with remarkable precision to any real gas. Van der Waals's work earned him almost instantaneous fame among his colleagues. His thesis was translated into German, English, and French, and gained him notice in the science world. Van der Waals was elected to the Royal Dutch Academy of Sciences in 1877, and two years later he was appointed professor of physics at the newly created University of Amsterdam. He remained in that post for three decades, retiring in 1907, to be succeeded by his son.
Van der Waals continued to work on the relationship between gases and liquids for the rest of his career. In 1890 he suggested the notion of binary solutions--states in which a substance exists as both a gas and a liquid at the same time. The calculations that van der Waals made on binary solutions later proved crucial in the fledgling field of cryogenics, specifying the conditions under which a gas can be converted to a liquid. One of the pioneers of this field, Heike Kamerlingh-Onnes, acknowledged his debt to van der Waals in an article in Eduard Farber's book Great Chemists, in which he said, "How much I was under the influence of its great importance as much as forty years ago may be best judged by my taking it then as a guide for my own researches."
For many students of science, van der Waals may be best known for the weak intermolecular forces that now carry his name. Originally called by him "pseudoassociation," these forces were hypothesized by van der Waals to explain the aggregation of particles in liquid solutions that occurred, for example, during the formation of binary solutions. Today, van der Waals forces are invoked to describe a host of situations in which rapidly shifting electron distributions in a molecule result in the formation of weak, but nonzero, transient attractions between molecules.
During the last ten years of his life, van der Waals gradually grew frail; he died in Amsterdam on March 8, 1923. Van der Waals had been elected to membership in the French Academy of Sciences, the British Chemical Society, the U.S. National Academy of Sciences, the Royal Academy of Sciences of Berlin, and the Russian Imperial Society of Naturalists.
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