(Shigenobu June 12) July 10, 1908, the Dutch physicist Onnes first liquefied final permanent gas helium. end



card forest • Onnes (Kamerlingh Onnes) is a low-temperature physicist, born in Groningen in the Netherlands on September 21, 1853, February 21, 1926 and died in the Netherlands Leiden. The (history TodayOnHistory.com) made of liquid helium and discovered superconductivity phenomenon was awarded the Nobel Prize in Physics in 1913.
1882 Onnes, a 29-year-old was appointed as the person in charge of the Leiden University professor of physics and the physics laboratory. Then Physics is in an era of change, there is a growing emphasis on physical experiments. Onnes as a person in charge of the physics laboratory of the University of Leiden, it was decided to study the low-temperature physics as the main direction. Affected by the work of Van der Waals, Onnes general thermodynamic characteristics of liquids and gases within a very wide range of pressure and temperature. Support from experiments on the van der Waals gas theory, in particular the corresponding state law, Onnes managed to expand the measurement range to the lowest possible temperature. Experiments found that, in order to make the gas liquefaction, it is necessary to compress the gas, and to enable it to cool to below the critical temperature. If allowed gas to push the piston external work, or the work done by the vacuum expander, further cooling occurs, resulting in the liquefaction of some gases. In order to obtain low temperature, the samples must exothermic. The most convenient way is to sample immersed in a liquefied gas. When the gasification of liquefied gas, the sample will continue to emit heat. To make difficult liquefaction of helium liquefaction, Onnes a well-designed system. Evaporator jacket to cool the helium using a liquid hydrogen, and then, and then throttling expansion, so that the part of the helium liquefier. (L $ dj��.��r��)
to be a low-temperature experiments, we must first get the low temperature. Low temperature to rely on access to liquefied gas. When only hydrogen and helium has not been liquefied. British physicist the Dewar from 1877 began to study in 1898, after twenty years, liquefied hydrogen. Onnes leadership Physics Laboratory of the University of Leiden in order to meet the needs of the low-temperature research, in 1892 to 1894 and built a large liquefied oxygen, nitrogen and air factory, 1906 can be mass-produced liquid hydrogen, liquefied helium laid a solid foundation. And after two years of struggle, finally in the July 10, 1908 successfully liquefied helium. Create the conditions to study the nature of the substance in the liquid helium temperature.
filed in 1908 so that helium liquefier very memorable day, said: "When liquid helium is presented to the van der Waals, my friend, I was so happy, his theory Onnes I have been guided to the final victory. "
Metal resistance problem Onnes an important research topic. Metal resistance near absolute zero how to change, there are different versions, some people believe that the resistance of pure metals with decreasing temperature gradually smaller and eventually disappear at absolute zero. The Onnes initially believe Kelvin 1902 Another view, as the temperature decreases, the resistance of the metal reaches a minimum value, due to electronic cohesion to the metal highland sub becomes infinite. Onnes liquefied helium technology is mastered, thus have the conditions for the experiment to study the issue. In February 1911, he measured the resistance of the gold and platinum in the liquid helium temperature, 4.3K or less, a platinum resistance maintained at a constant. Rather than through a minimum value and then increases. So he changed his views to the Plateau and the pure platinum resistance should disappear at liquid helium temperatures. To test his views,
selected the mercury as experimental object, because mercury is easily purified than other metals. The experimental results appear strange unexpected phenomenon: the mercury resistance about 4.2K suddenly disappear. This extraordinary discovery, indicates that not only can greatly improve the efficiency of power generation in the electric power industry, but also opened up a vast world for people to take advantage of the of this superconductivity manufacturing superconducting motors, superconducting magnets and superconducting cables, etc.. April 1911 to November, Onnes detail in the triple consecutive papers reported the results of his experiments. (Of $ dj��.c��m)
1913, Onnes discovered tin and lead and mercury, superconductivity, impure mercury superconductivity. Due to the study of low-temperature properties of substances and the preparation of liquid helium, Onnes (Heike Kamerlingh Onnes 1853 ~ 1926) was awarded the 1913 Nobel Prize in Physics. Onnes outstanding leadership and management of the Physics Laboratory of the University of Leiden, the laboratory became the center of the low-temperature research around the world in the beginning of this century.