Van der Waals, Johannes Diderik(1837-1923) Johannes diderik van der Waals was born on november 23, 1837 in Leyden, The Netherlands, the son of Jacobus van der Waals and Elisabeth van den Burg. After having finished elementary education at his birthplace he became a schoolteacher. Although he had no knowledge of classical languages, and thus was not allowed to take academic examinations, he continued studying at Leyden University in his spare time during 1862-65. In this way he also obtained teaching certificates in mathematics and physics In 1864 he was appointed teacher at a secondary school at Deventer;in 1866 he moved to The Hague, first as teacher and later as Director of one of the secondary schools in that New legislation whereby university students in science were exempted from the conditions concerning prior classical education enabled Van der Waals to sit for university examinations. In 1873 he obtained his doctors degree for a thesis entitled Over de Continuiteit van den Gas-en Vloeistoftoestand(On the continuity of the gas and liquid state), which put him at once in the foremost rank of physicists. In this thesis he put forward an"Equation of State"embracing both the gaseous and the liquid state, he could demonstrate that these two states of aggregation not only merge into each other in a continuous manner, but that they are in fact of the same nature. The importance of this conclusion from Van der Waals very first paper can be judged from the remarks made by James Clerk Maxwell in Nature, "that there can be no doubt that the name of Van der Waals will soon be among the foremost in molecular science"and"it has certainly directed the attention of more than one inquirer to the study of the Low-Dutch language in which it is written"(Maxwel probably meant to say Low-German", which would also be incorrect, since Dutch is a language in its own right). Subsequently, numerous papers on this and related subjects were published in the Proceedings of the Royal Netherlands Academy of Sciences and in the Archives Neerlandaises, and they were also translated into other languages When, in 1876, the new Law on Higher Education was established which promoted the old Athenaeum Illustre of Amsterdam to university status, Van der Waals was appointed the first Professor of Physics. Together with Van't Hoff and Hugo de vries, the geneticist, he contributed to the fame of the University, and remained faithful to it until his retirement, in spite of enticing invitations from elsewhere The immediate cause of Van der Waals' interest in the subject of his thesis was R Clausius' treatise considering heat as a phenomenon of motion, which led him to look for an explanation for T. Andrews' experiments(1869)revealing the existence of"critical temperatures "in gases. It was Van der Waals genius that made him see he necessity of taking into account the volumes of molecules and the intermolecular forces ("Van der Waals forces", as they are now generally called) in establishing the relationship between the pressure, volume and temperature of gases and liquids A second great discovery-arrived at after much arduous work-was published in 1880, when he enunciated the Law of Corresponding States. This showed that if pressure is expressed as a simple function of the critical pressure, volume as one of the critical volume, and temperature as one of the critical temperature, a general form of the equation of state is obtained which is applicable to all substances, since he three constants a, b, and R in the equation, which can be expressed in the critical quantities of a particular substance, will disappear. It was this law which served as a guide during experiments which ultimately led to the liquefaction of hydrogen by J. Dewar in 1898 and of helium by H Kamerlingh Onnes in 1908. The latter, who in 1913 received the Nobel Prize for his low-temperature studies and his production of liquid helium, wrote in 1910"that Van der Waals studies have always been considered as a magic wand for carrying out experiments and that the Cryogenic Laboratory at Leyden has developed under the influence of his theories Ten years later, in 1890, the first treatise on the"Theory of Binary Solutions appeared in the Archives Neerlandaises- another great achievement of Van der Waals. By relating his equation of state with the Second Law of Thermodynamics, inVan der Waals, Johannes Diderik (1837-1923) Johannes Diderik van der Waals was born on November 23, 1837 in Leyden, The Netherlands, the son of Jacobus van der Waals and Elisabeth van den Burg. After having finished elementary education at his birthplace he became a schoolteacher. Although he had no knowledge of classical languages, and thus was not allowed to take academic examinations, he continued studying at Leyden University in his spare time during 1862-65. In this way he also obtained teaching certificates in mathematics and physics. In 1864 he was appointed teacher at a secondary school at Deventer; in 1866 he moved to The Hague, first as teacher and later as Director of one of the secondary schools in that town. New legislation whereby university students in science were exempted from the conditions concerning prior classical education enabled Van der Waals to sit for university examinations. In 1873 he obtained his doctor's degree for a thesis entitled Over de Continuïteit van den Gas - en Vloeistoftoestand (On the continuity of the gas and liquid state), which put him at once in the foremost rank of physicists. In this thesis he put forward an "Equation of State" embracing both the gaseous and the liquid state; he could demonstrate that these two states of aggregation not only merge into each other in a continuous manner, but that they are in fact of the same nature. The importance of this conclusion from Van der Waals' very first paper can be judged from the remarks made by James Clerk Maxwell in Nature, "that there can be no doubt that the name of Van der Waals will soon be among the foremost in molecular science" and "It has certainly directed the attention of more than one inquirer to the study of the Low-Dutch language in which it is written" (Maxwell probably meant to say "Low-German", which would also be incorrect, since Dutch is a language in its own right). Subsequently, numerous papers on this and related subjects were published in the Proceedings of the Royal Netherlands Academy of Sciences and in the Archives Néerlandaises, and they were also translated into other languages. When, in 1876, the new Law on Higher Education was established which promoted the old Athenaeum Illustre of Amsterdam to university status, Van der Waals was appointed the first Professor of Physics. Together with Van't Hoff and Hugo de Vries, the geneticist, he contributed to the fame of the University, and remained faithful to it until his retirement, in spite of enticing invitations from elsewhere. The immediate cause of Van der Waals' interest in the subject of his thesis was R. Clausius' treatise considering heat as a phenomenon of motion, which led him to look for an explanation for T. Andrews' experiments (1869) revealing the existence of "critical temperatures " in gases. It was Van der Waals' genius that made him see the necessity of taking into account the volumes of molecules and the intermolecular forces ("Van der Waals forces", as they are now generally called) in establishing the relationship between the pressure, volume and temperature of gases and liquids. A second great discovery - arrived at after much arduous work - was published in 1880, when he enunciated the Law of Corresponding States. This showed that if pressure is expressed as a simple function of the critical pressure, volume as one of the critical volume, and temperature as one of the critical temperature, a general form of the equation of state is obtained which is applicable to all substances, since the three constants a, b, and R in the equation, which can be expressed in the critical quantities of a particular substance, will disappear. It was this law which served as a guide during experiments which ultimately led to the liquefaction of hydrogen by J. Dewar in 1898 and of helium by H. Kamerlingh Onnes in 1908. The latter, who in 1913 received the Nobel Prize for his low-temperature studies and his production of liquid helium, wrote in 1910 "that Van der Waals' studies have always been considered as a magic wand for carrying out experiments and that the Cryogenic Laboratory at Leyden has developed under the influence of his theories ". Ten years later, in 1890, the first treatise on the "Theory of Binary Solutions" appeared in the Archives Néerlandaises - another great achievement of Van der Waals. By relating his equation of state with the Second Law of Thermodynamics, in