JOHANNES DIDERIK VAN DER WAALS RALPH E. OESPER University of Cincinnati, Cincinnati, Ohio
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His doctorate was awarded in 1873 and his dissertaiion "On the continuity of the gaseous and liquid states" attracted much attention. I t was subsequently translated into English, French, and German. This topic was the leitmotifof all his important mork. He is best known for his improvement of the equation of state, taking into account the attraction between the particles of the gas and their own proper volume. In other words, the internal pressure of the gas is greater than the observed Dressure bv the amount a h 2 . He calculated the pressure inside a drop of water to be about 10,000 atmospheres. The second factor responsible for the deviation from the ideal gas law was introduced in the well known correction (v - b). The most important development of this work mas the van der Waals lalv of corresponding states, which enables the operator to calculate the state of any gas or liquid at any temperature and pressure if the state a t the critical temperature is known. The Nobel Prize was awarded t o this great theoretician in 1910 "for his work concerning the equation of state of gases and liquids.'' In subsequent studies he found that b varies with temperature and Clausius found that a is not constant for a given material but varies with temperature. However, the van der Waals equation was a most valuable approach to a very difficult problem and it has been a great aid in the liquefaction of gases and the theory of the modern freezing techninue. ? a n d & Wads died at Amsterdam on March 9, 1923, and is buried there. The plain stone covering his grave is already quite weather-beaten and the inscription is becoming hard to read.
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