Marcello Stefano Pirani (July 1, 1880 – January 11, 1968) was a German

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

known for his invention of the Pirani vacuum gauge, a

vacuum gauge {{Cat main, Vacuum system Vacuum Systems A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boun ...

based on the principle of heat loss measurement. Throughout his career, he worked on advancing lighting technology and pioneered work on the physics of gas discharge.

Biography

Marcello Pirani was born on July 1, 1880, in

Berlin Berlin ( , ) is the capital and List of cities in Germany by population, largest city of Germany by both area and population. Its 3.7 million inhabitants make it the European Union's List of cities in the European Union by population within ci ...

. Starting in 1899, he studied mathematics and

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

at the

University of Berlin Humboldt-Universität zu Berlin (german: Humboldt-Universität zu Berlin, abbreviated HU Berlin) is a German public research university in the central borough of Mitte in Berlin. It was established by Frederick William III on the initiative ...

. In 1903, he was granted a PhD for his measurements of the

dielectric In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mate ...

constant of solids in the group of Emil Warburg. He then moved to the Technical University of Aachen as an assistant at the Physikalischen Institut of this university. In 1904, he joined the light bulb factory (''Glühlampenwerk'') of

Siemens & Halske Siemens & Halske AG (or Siemens-Halske) was a German electrical engineering company that later became part of Siemens. It was founded on 12 October 1847 as ''Telegraphen-Bauanstalt von Siemens & Halske'' by Werner von Siemens and Johann Ge ...

AG in Berlin, where he remained for the next fifteen years. At the age of 25, in 1905, he was promoted to head of the development lab of the light bulb factory. In 1906, he made his most important invention with the development of a new type of

that today bears his name, the

Pirani gauge The Pirani gauge is a robust thermal conductivity gauge used for the measurement of the pressures in vacuum systems. It was invented in 1906 by Marcello Pirani. Marcello Stefano Pirani was a German physicist working for Siemens & Halske which was ...

. It is based on measuring the pressure dependence of heat loss from a hot wire by heat transfer to the surrounding gas and walls. In particular, it employs the change in resistivity of the heated wire (in Pirani's original work consisting of

tantalum Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that ...

and

platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Pla ...

; today,

tungsten Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isol ...

, platinum, and

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...

are commonly used) with temperature to determine the heat loss. Its useful measurement range lies within 10⁻⁴

mbar The bar is a metric unit of pressure, but not part of the International System of Units (SI). It is defined as exactly equal to 100,000 Pa (100 kPa), or slightly less than the current average atmospheric pressure on Earth at sea lev ...

up to 1000 mbar. Four years later, he finished his habilitation on optical measurements of high temperatures and studies on the relationship between temperature and emissivity of hot solids and becomes private docent at the Technical University Berlin-Charlottenburg. During the

First World War World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

, he enlisted in the army to deal with scientific-technical problems such as

wireless telegraphy Wireless telegraphy or radiotelegraphy is transmission of text messages by radio waves, analogous to electrical telegraphy using cables. Before about 1910, the term ''wireless telegraphy'' was also used for other experimental technologies for ...

. In 1918, Pirani was promoted Titular-Professor at the

TU Berlin The Technical University of Berlin (official name both in English and german: link=no, Technische Universität Berlin, also known as TU Berlin and Berlin Institute of Technology) is a public research university located in Berlin, Germany. It wa ...

-Charlottenburg. One year later, he co-founded the Deutsche Gesellschaft für Metallkunde (German society for metal science) in Berlin. From 1919 to 1936, he worked for the newly formed Osram company. As head of the scientific-technical bureau, he was in charge of coordinating and pushing scientific work in the field of light bulbs of the three founding companies

, AEG and the Auergesellschaft. In this time fall his pioneering contributions to the advancement of lighting technology, in particular in the field of gas-discharge lamps: In 1922, he was named außerordentlicher Professor at the TU Berlin. In 1928, he became head of the Studiengesellschaft for electrical lighting of the Osram GmbH. He wrote a textbook on heat generation from electrical sources in 1930. As his mother — Clara Schönlank — was Jewish,Memoirs of Mario von Pirani
«''1936 wurde er als „Halbjude“ aus dem Staatsdienst entfernt. Er emigrierte nach London''». with the rise of the

Nazi Party The Nazi Party, officially the National Socialist German Workers' Party (german: Nationalsozialistische Deutsche Arbeiterpartei or NSDAP), was a far-right political party in Germany active between 1920 and 1945 that created and supported t ...

to power in Germany he left Germany in 1936 for England and joined the research lab of

General Electric General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable en ...

Co. Ltd. in

Wembley Wembley () is a large suburbIn British English, "suburb" often refers to the secondary urban centres of a city. Wembley is not a suburb in the American sense, i.e. a single-family residential area outside of the city itself. in north-west Londo ...

. There his work focused on gas discharge lamps and high temperature resistant materials. From 1941 to 1947, he served as scientific consultant for the British Coal Utilization Research Association in

London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...

, working on new high temperature resistant materials involving

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

. Between 1947 and 1952, he was scientific consultant for the British-American Research Ltd., also in London. In 1953, he returned to Germany as one of the few second world war repatriates with scientific background and moved first to

Munich Munich ( ; german: München ; bar, Minga ) is the capital and most populous city of the German state of Bavaria. With a population of 1,558,395 inhabitants as of 31 July 2020, it is the third-largest city in Germany, after Berlin and Ha ...

and from 1955 to his hometown Berlin. In 1954, he took up a consultant position with Osram working on problems in gas discharge, glass and ceramics up to an old age. On January 11, 1968, Marcello Pirani died in Berlin.

Awards

*1933 Honorary member of the Lichttechnischen Gesellschaft *1933 Gauß-Weber-Medal of the University Göttingen *1961 Federal Cross of Merit 1. class of the Federal Republic of Germany

References

{{DEFAULTSORT:Pirani, Marcello Officers Crosses of the Order of Merit of the Federal Republic of Germany 20th-century German physicists German Quakers German people of Italian descent 1880 births 1968 deaths Jewish emigrants from Nazi Germany to the United Kingdom