Sixty-eight years ago today, on August 16, 1957 (July 21, 1957 in the lunar calendar), American physical chemist Langmuir died. Langmuir Irving Langmuir (January 31, 1881 - August 16, 1957) American chemist. Born January 31, 1881 in Brooklyn, New York, died August 16, 1957 in Falmers, Massachusetts. He graduated from the School of Mines at Columbia University in 1903 and was awarded the title of Metallurgical Engineer. He received his PhD in Chemistry from the University of Göttingen in Germany in 1906. He taught at the Stephens Institute of Technology from 1906 to 1909. He studied physical chemistry at the General Electric Research Laboratory in New York from 1909 and served as assistant director and deputy director in 1932. Langmuir developed a high-vacuum electron tube in 1912, which brought the tube into practical use. In 1913, he developed a nitrogen-filled and argon-filled incandescent lamp. In 1924-1927, he invented the hydrogen atomic welding gun. He also developed high-vacuum mercury pumps and acoustic devices for detecting submarines. He also made great contributions to the scientific research of electron emission, space charge phenomena, gas discharges, atomic structure and surface chemistry. He was awarded the 1932 Nobel Prize in Chemistry for his achievements in atomic structure and surface chemistry. He was awarded the Nichols Medal of the American Chemical Society twice in 1915 and 1920, the Hughes Medal and the Longford Medal of the Royal Society in 1918, and the Faraday Medal in 1944. Since 1940, Langmuir has made important contributions to cloud and precipitation microphysics and artificial rainfall experiments. After publishing the article "Supercooled Droplets in Rising Saturated Cold Air Flow" in 1944, he and his assistants first explored the possibility of seeding clouds and precipitation with silver iodide and solid carbon dioxide (dry ice) in 1946. In 1948, he published the article "Rainfall Caused by Chain Reactions in Warm Cumulus Clouds", which quantitatively calculated the efficiency and collision growth rate of large cloud droplets trapping small cloud droplets as they fell in the gravitational field. New insights such as the minimum radius of the chain reaction of cloud droplets breaking-growing and the minimum height of the secondary breaking were proposed, which was called the Langmuir chain reaction. From 1948 to 1951, he published "Study on the Seeding Effect of Dry Ice in Stratiform Clouds", "Various Cloud Seeding Techniques for Controlling Cumulus Precipitation", "Progress of Artificial Influence on Clouds in Cirrus Research Program" and other papers. He has made great contributions in many aspects such as electron emission, space charge phenomena, gas discharge, atomic structure, surface chemistry, cloud and precipitation microphysics, artificial rainfall experiments, etc.