Today is the 161st anniversary of the birth of Johannes van der Waals, a Dutch physical chemist known for his theories about gases and interatomic forces. Van der Waals described in simple mathematical terms the various phenomena of gases and liquids that other scientists had observed experimentally, such as the existence of a critical temperature, above which a gas cannot be liquefied by pressure alone. By accounting for the intermolecular attractions of different gases, van der Waals extended the idealized gas laws of Robert Boyle and others to the behavior of real gases. These intermolecular attractions in gases came to be known as van der Waals forces. Van der Waals won the Nobel Prize in physics in 1910 and died in 1923.
[Source: Roy Porter, Ed., The Biographical Dictionary of Scientists (Oxford University Press, ed. 2, 1994).]