Scottish Chemist and Physicist. He is best remembered for his invention of the Dewar flask, which he used in conjunction with extensive research into the liquefaction of gases. His scientific work covers a wide field, from organic chemistry, hydrogen and its physical constants, high temperature research, the temperature of the sun, and of the electric spark, electro-photometry and the chemistry of the electric arc. Born the youngest of six boys, he received his education at the Dollar Academy, a boarding school in central Scotland and the University of Edinburgh in Edinburgh, Scotland, where he studied under Scottish scientist Lyon Playfair and later became his assistant. In 1867 he described several chemical formulas for benzene. He investigated the physiological action of light and examined the changes which take place in the electrical condition of the retina under its influence. In 1877 he was he was elected a Fellow of the Royal Society of London. The following year, he began a long series of spectroscopic observations, including to the spectroscopic examination of various gaseous elements separated from atmospheric air by the aid of low temperatures. By 1891 he had designed and built, at the Royal Institution of Great Britain, 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. Around 1892 he conceived the idea 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 that it was found possible to preserve the liquids for comparatively long periods, making examination of their optical properties possible. He 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 he was recognized as the inventor, because he did not patent his invention, there was no way to stop Thermos from using the design. He then experimented with a high-pressure hydrogen jet by which low temperatures were realized 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. In 1898 he used this machine for the first time to collect liquid hydrogen, with solid hydrogen following a year later. He attempted 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 lack of helium with which to work, he was preceded by Dutch physicist Heike Kamerlingh Onnes in 1908 as the first person to produce liquid helium. 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 successful in winning the Nobel Prize. In 1902 he became president of the British Science Association and in 1904 he was knighted for his work in the field of physics. The following year, he began to investigate the gas-absorbing powers of charcoal when cooled to low temperatures and applied his research to the production of high vacuums, which were useful for further experiments in atomic physics. He 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, he had little interest in restarting the serious research work which went on before the war. Shortages of scholars compounded the problems, and 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. He died at the age of 80, still holding the office of Fullerian Professor of Chemistry at the Royal Institution (since 1877), having refused to retire. Among his honors and awards include the president of the Chemical Association (1897), the Smithsonian Institution Hodgkins Gold Medal (1899, the first recipient), the Royal Society's Rumford (1894), Davy (1909), and Copley (1916) Medals, the Royal Society of Edinburgh's Gunning Victoria Jubilee Prize (1900 to 1904), the French Academy of Sciences Lavoisier Medal (1904, the first British person to receive it), the Italian Society of Sciences Matteucci Medal (1906, the first recipient), the Albert Medal of the Royal Society of Arts (1908), and the Franklin Medal by the Franklin Institute of Philadelphia, Pennsylvania (1919) for Physics. A lunar crater was named in his honor.