<P> His name is most widely known in connection with his work on the liquefaction of the so - called permanent gases and his researches at temperatures approaching absolute zero . His interest in this branch of physics and chemistry dates back at least as far as 1874, when he discussed the "Latent Heat of Liquid Gases" before the British Association . In 1878, he devoted a Friday evening lecture at the Royal Institution to the then - recent work of Louis Paul Cailletet and Raoul Pictet, and exhibited for the first time in Great Britain the working of the Cailletet apparatus . Six years later, again at the Royal Institution, he described the researches of Zygmunt Florenty Wróblewski and Karol Olszewski, and illustrated for the first time in public the liquefaction of oxygen and air . Soon afterward, he built a machine from which the liquefied gas could be drawn off through a valve for use as a cooling agent, before using the liquid oxygen in research work related to meteorites; about the same time, he also obtained oxygen in the solid state . </P> <P> By 1891, he had designed and built, at the Royal Institution, machinery which yielded liquid oxygen in industrial quantities, and towards the end of that year, he showed that both liquid oxygen and liquid ozone are strongly attracted by a magnet . About 1892, the idea occurred to him of using vacuum - jacketed vessels for the storage of liquid gases--the Dewar flask (otherwise known as a Thermos or vacuum flask)--the invention for which he became most famous . The vacuum flask was so efficient at keeping heat out, it was found possible to preserve the liquids for comparatively long periods, making an examination of their optical properties possible . Dewar did not profit from the widespread adoption of his vacuum flask--he lost a court case against Thermos concerning the patent for his invention . While Dewar was recognised as the inventor because he did not patent his invention, no way to stop Thermos from using the design was possible . </P> <P> He next experimented with a high - pressure hydrogen jet by which low temperatures were realised through the Joule--Thomson effect, and the successful results he obtained led him to build at the Royal Institution a large regenerative cooling refrigerating machine . Using this machine in 1898, liquid hydrogen was collected for the first time, solid hydrogen following in 1899 . He tried to liquefy the last remaining gas, helium, which condenses into a liquid at − 268.9 ° C, but owing to a number of factors, including a short supply of helium, Dewar was preceded by Heike Kamerlingh Onnes as the first person to produce liquid helium, in 1908 . Onnes would later be awarded the Nobel Prize in Physics for his research into the properties of matter at low temperatures--Dewar was nominated several times, but never succeeded in winning the Nobel Prize . </P> <P> In 1905, he began to investigate the gas - absorbing powers of charcoal when cooled to low temperatures and applied his research to the creation of high vacuum, which was used for further experiments in atomic physics . Dewar continued his research work into the properties of elements at low temperatures, specifically low - temperature calorimetry, until the outbreak of World War I . The Royal Institution laboratories lost a number of staff to the war effort, both in fighting and scientific roles, and after the war, Dewar had little interest in restarting the serious research work that went on before the war . Shortages of scholars necessarily compounded the problems . His research during and after the war mainly involved investigating surface tension in soap bubbles, rather than further work into the properties of matter at low temperatures . </P>

Who has won the race to liquefy helium