Johannes Diderik van der Waals
Johannes Diderik van der Waals (November 23 1837 – March 8 1923) was a Dutch theoretical physicist. His name is associated with the van der Waals equation of state that describes the behavior of gases and their condensation to the liquid phase. His name is also associated with van der Waals forces, which are forces between stable molecules, and van der Waals molecules, which are (small) clusters of molecules bound by van der Waals forces. He was the first physics professor of the University of Amsterdam, becoming a professor at the same time that this university was founded (1877).
Biography
Johannnes Diderik was the oldest of ten children born to Jacobus van der Waals and Elisabeth van den Berg. His father was a carpenter in the Dutch city of Leiden. As was usual for working class children in the 19th century, he did not go to the kind of secondary school that would have given him the right to enter university. Instead he went to a school of "advanced primary education" (in Dutch: MULO), which he finished at the age of fifteen. He then became a teacher's apprentice in an elementary school. Between 1856 and 1861 he followed courses and gained the necessary qualifications to be a primary school teacher and to be head of such a school.
In 1862, he began to attend lectures at the University of Leiden in mathematics, physics and astronomy, although he was not qualified to be enrolled as a regular student. However, the University had a provision that enabled outside students up to four courses a year. In 1863 the Dutch government started a new kind of secondary school (HBS, a school meant to cater for the children of the higher middle classes). Van der Waals—at that time director of an elementary school—wanted to become a HBS teacher in mathematics and physics and spent two years to study for the required examinations. In 1865, he was appointed as a physics teacher at the HBS in Deventer and in 1866, he received such a position in The Hague, which is close enough to Leiden to allow van der Waals to resume his courses at the University there. While still in Deventer Johannes Diderik married with the eightteen year old Anna Magdalena Smit.
Van der Waals still lacked the knowledge of the classical languages that would have given him the right to enter university as a regular student and to take examinations. However it so happened that the law regulating the university entrance was changed and dispensation from the study of classical languages could be given by the minister of education. Van der Waals was given this dispensation and brilliantly passed the exams in physics and mathematics that qualified for doctoral studies. At Leiden University, on June 14, 1873, he defended his doctoral thesis Over de Continuiteit van den Gas en Vloeistoftoestand (on the continuity of the gaseous and liquid state). In the thesis, he introduced the concepts of molecular volume and molecular attraction (see the article on the van der Waals equation for the technical background).
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