(1881-1957) US scientist who invented the mercury vapor pump for producing a high vacuum, and the atomic hydrogen welding process; he was also a pioneer of the thermionic valve. In 1932 he was awarded a Nobel Prize for his work on surface chemistry.
Langmuir was born in New York and studied there at Columbia University and in Germany at Göttingen. He worked at the research laboratories of the General Electric Company 1909–50.
Langmuir's research on electric discharges in gases at very low pressures led to the discovery of the space-charge effect: the electron current between electrodes of any shape in vacuum is proportional to the 3/2 power of the potential difference between the electrodes. He also studied the mechanical and electrical properties of tungsten lamp filaments. Langmuir's introduction of nitrogen into light bulbs prevented them from blackening on the inside but increased heat loss, which was overcome by coiling the tungsten filament.
Langmuir was the first to use the terms “electrovalence” (for ionic bonds between metals and nonmetals) and “covalence” (for shared-electron bonds between nonmetals).
During the 1920s, Langmuir became particularly interested in the properties of liquid surfaces. He went on to propose his general adsorption theory for the effect of a solid surface during a chemical reaction.