Otto Hönigschmid (13 March 1878 in

Hořovice Hořovice (; ) is a town in Beroun District in the Central Bohemian Region of the Czech Republic. It has about 8,100 inhabitants. The town is known for the Hořovice Castle. Geography Hořovice is located about southwest of Beroun and southwest ...

– 14 October 1945 in

Munich Munich is the capital and most populous city of Bavaria, Germany. As of 30 November 2024, its population was 1,604,384, making it the third-largest city in Germany after Berlin and Hamburg. Munich is the largest city in Germany that is no ...

) was a

Czech Czech may refer to: * Anything from or related to the Czech Republic, a country in Europe ** Czech language ** Czechs, the people of the area ** Czech culture ** Czech cuisine * One of three mythical brothers, Lech, Czech, and Rus *Czech (surnam ...

Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...

n chemist. He published the first widely accepted experimental proof of isotopes along with Stefanie Horovitz. Throughout his career he worked to precisely define atomic weights for over 40 elements, and served on committees with the purpose of adopting internationally agreed upon values. After his home and laboratory in Munich were destroyed in

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

, he committed suicide in 1945.

Education

Hönigschmid studied organic chemistry at the

Charles University in Prague Charles University (CUNI; , UK; ; ), or historically as the University of Prague (), is the largest university in the Czech Republic. It is one of the oldest universities in the world in continuous operation, the oldest university north of the ...

under the guidance of

Guido Goldschmiedt Guido Goldschmiedt (May 29, 1850 – August 6, 1915) was an Austrian chemist. During his career, he collaborated with Bunsen in Heidelberg and Baeyer in Straßburg. In 1891, he became full professor at the University of Vienna and later at the Un ...

(the discoverer of the structure of

papaverine Papaverine (Latin '' papaver'', "poppy") is an opium alkaloid antispasmodic drug, used primarily in the treatment of visceral spasms and vasospasms (especially those involving the intestines, heart, or brain), occasionally in the treatment of ...

). Additionally, he worked as a student researcher in

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

under

Henri Moissan Ferdinand Frédéric Henri Moissan (; 28 September 1852 – 20 February 1907) was a French chemist and pharmacist who won the 1906 Nobel Prize in Chemistry for his work in isolating fluorine from its compounds. Among his other contributions, Mo ...

from 1904 to 1906. He was

habilitated Habilitation is the highest university degree, or the procedure by which it is achieved, in Germany, France, Italy, Poland and some other European and non-English-speaking countries. The candidate fulfills a university's set criteria of excellen ...

in 1908 upon publication of a thesis on carbide and silicide.

Career and Scientific Research

In 1909, Hönigschmid worked under Theodore Richards at

Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...

to determine the official weight of

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

. During this year he learned Richards' Nobel Prize winning methods for precisely determining atomic weights, which earned Hönigschmid credibility in the field. From 1911-18 he was a professor and directory of the laboratory of

inorganic An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemistry''. Inor ...

and

analytical chemistry Analytical skill, Analytical chemistry studies and uses instruments and methods to Separation process, separate, identify, and Quantification (science), quantify matter. In practice, separation, identification or quantification may constitute t ...

at the Prague Polytechnic University. He was simultaneously involved in research at the Radium Institute of Vienna, traveling back and forth between the two cities. He was asked by

Frederick Soddy Frederick Soddy FRS (2 September 1877 – 22 September 1956) was an English radiochemist who explained, with Ernest Rutherford, that radioactivity is due to the transmutation of elements, now known to involve nuclear reactions. He also pr ...

and

Kazimierz Fajans Kazimierz Fajans (Kasimir Fajans in many American publications; 27 May 1887 – 18 May 1975) was a Polish-Jewish physical chemist, a pioneer in the science of radioactivity and the co-discoverer of chemical element protactinium. Education and ca ...

to determine precise atomic weights of lead from radioactive sources in support of their

radioactive displacement law of Fajans and Soddy The law of radioactive displacements, also known as Fajans's and Soddy's law, in radiochemistry and nuclear physics, is a rule governing the transmutation of elements during radioactive decay. It is named after Frederick Soddy and Kazimierz Fa ...

, which had not yet been credibly proven by experimental means. At the suggestion of

Lise Meitner Elise Lise Meitner ( ; ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish nuclear physicist who was instrumental in the discovery of nuclear fission. After completing her doctoral research in 1906, Meitner became the second woman ...

, he recruited Stefanie Horovitz in 1914 to work from his Vienna lab processing lead from uranium-rich pitchblende and measuring its atomic weight to the thousandth of a gram. The two co-published their results showing a significant difference in weight between the uranium lead (206.736 g/mol) and standard lead (207.190 g/mol), thereby providing the first authoritative proof of the existence of isotopes. Within two years, Hönigschmid and Horovitz demonstrated the second known case of isotopes by showing that

ionium Thorium (90Th) has seven naturally occurring isotopes but none are stable. One isotope, 232Th, is ''relatively'' stable, with a half-life of 1.405×1010 years, considerably longer than the age of the Earth, and even slightly longer than the gen ...

, a recently discovered element, was in fact

thorium-230 Thorium (90Th) has seven naturally occurring isotopes but none are stable. One isotope, 232Th, is ''relatively'' stable, with a half-life of 1.405×1010 years, considerably longer than the age of the Earth, and even slightly longer than the gen ...

. In 1918, he moved to Germany to teach at Munich University, where he founded a laboratory specifically for research with atomic weights. He and his colleagues worked up until 1941 to precisely define atomic weights of over 40 elements. Notable contributions redefined values for

silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...

niobium Niobium is a chemical element; it has chemical symbol, symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and Ductility, ductile transition metal. Pure niobium has a Mohs scale of mineral hardness, Mohs h ...

tantalum Tantalum is a chemical element; it has Symbol (chemistry), symbol Ta and atomic number 73. It is named after Tantalus, a figure in Greek mythology. Tantalum is a very hard, ductility, ductile, lustre (mineralogy), lustrous, blue-gray transition ...

, and

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

. Contributing to the work of

Ernest Rutherford Ernest Rutherford, 1st Baron Rutherford of Nelson (30 August 1871 – 19 October 1937) was a New Zealand physicist who was a pioneering researcher in both Atomic physics, atomic and nuclear physics. He has been described as "the father of nu ...

and

Marie Curie Maria Salomea Skłodowska-Curie (; ; 7 November 1867 – 4 July 1934), known simply as Marie Curie ( ; ), was a Polish and naturalised-French physicist and chemist who conducted pioneering research on radioactivity. She was List of female ...

, Hönigschmid prepared

radium Radium is a chemical element; it has chemical symbol, symbol Ra and atomic number 88. It is the sixth element in alkaline earth metal, group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, ...

standards for comparison in 1912 and again in 1934. Additionally, he served as the chairman of the German Atomic Weight Commission from 1920-1930, and in 1930 became the German representative in the Atomic Weights Committee of the International Union of Chemistry. This work was instrumental in the adoption of precisely defined atomic weights in the international scientific community.

Awards

He won the

Haitinger Prize The Haitinger Prize of the Austrian Academy of Sciences was founded in 1904 by the chemist and factory director, Ludwig Camillo Haitinger (1860–1945), who created the award in honor of his father, Karl Ludwig Haitinger. From 1905 to 1943 it was a ...

of the

Austrian Academy of Sciences The Austrian Academy of Sciences (; ÖAW) is a legal entity under the special protection of the Republic of Austria. According to the statutes of the Academy its mission is to promote the sciences and humanities in every respect and in every fi ...

in 1913, and the

Liebig Medal The Liebig Medal (German: ''Liebig-Denkmünze'') was established by the Society of German Chemists () in 1903 to celebrate the centenary of Justus von Liebig. Since 1946 it has been awarded by the Society of German Chemists (''Gesellschaft Deutsc ...

in 1940.

Death

Much of Hönigschmid's work, his home, and his laboratory in Munich were destroyed during

. Facing difficulties with his health and housing, he committed suicide alongside his wife in 1945. The two had been staying with the widow of

Hans Fischer Hans Fischer (; 27 July 1881 – 31 March 1945) was a German organic chemist and the recipient of the 1930 Nobel Prize for Chemistry "for his researches into the constitution of haemin and chlorophyll and especially for his synthesis of hae ...

, a friend and colleague who had also killed himself a few months prior.

References

External links

Contains short biography of Hönigschmid (in Czech)
* {{DEFAULTSORT:Honigschmid, Otto 1878 births 1945 suicides 1945 deaths People from Hořovice 20th-century Austrian chemists Charles University alumni Ludwig Maximilian University of Munich alumni Harvard University faculty Czech chemists Suicides in Germany Academic staff of Czech Technical University in Prague Chemists from Austria-Hungary