ONNES, HEIKE KAMERLINGH Dutch physicist, was born in Groningen on Sept. 21, 1853. He studied mathematics and physics in his native town. In 1871 he went to Heidelberg, where he studied under Bunsen and Kirchhoff (qq.v.). Later he returned to Groningen, where in 1879 he took his doctor's degree on presenting a dissertation entitled New Proofs of the Earth's Rotation. He became professor of experimental physics at Leyden in 1882. Here he founded and developed the famous Cryogenic Laboratory. Stimulated by van der Waals, Onnes became interested in the equations of state and the general thermodynamic properties of liquids and gases. (See THERMO DYNAMICS.) He appreciated that the need for exact measure ments was greater than that for fresh theoretical developments.
Onnes set himself the task of making measurements over a large range of pressure and temperature. His name is associated particularly with the measurement and attainment of low tem peratures ; in this direction Onnes showed himself a master of experimental physics. In 1908 he succeeded in liquefying helium, but was unable to solidify it ; this was subsequently done by his successor Keesom. Onnes obtained the isothermals for a number of gases and mixtures of gases at low temperatures ; he also studied the optical, magnetic and magneto-optical properties of bodies. He carried out important investigations on the influence
of low temperatures on nickel and manganese iron alloys. He also demonstrated that the resistance of electric conductors dis appeared suddenly at a temperature near the absolute zero, and termed this phenomenon "super-conductivity." His systematic researches on super-conductivity (started in 1914) are of extreme importance on account of their bearing on the theory of electri cal conduction in solids (see ELECTRICITY, CONDUCTION OF : Soups), and also because the facilities offered by the Cryogenic Laboratory for investigating this subject are practically unique.
In 1913 the Nobel Prize for physics was conferred on him. He became a foreign member of the Royal Society in 1916, and a corresponding member of the Prussian Academy of Sciences at Berlin in 1923, the year in which he resigned his chair at Leyden. He was the recipient of a number of honorary degrees, medals and other honours. His published work includes Algemeine Theorie der Vloeistoffen (General Theory of the Fluids, 1881). He died at Leyden on Feb. 21, 1926.
See J. P. Kuenen, De Toekenning van den Nobelprys aan H. Kamer lingh Onnes (Chemisch Weekblad, 1913).