Stefanie Horovitz (1887–1942) (Stefania Horovitz or Stephanie Horowitz) was a Polish-Jewish

chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a graduated scientist trained in the study of chemistry, or an officially enrolled student in the field. Chemists study the composition of ...

known for experimental work proving the existence of isotopes. Between approximately 1914-1918, she worked with Otto Hönigschmid at the Radium Institute of Vienna using analytical methods to demonstrate the first and second credible cases of isotopes in

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

and

thorium Thorium is a chemical element; it has symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air, forming thorium dioxide; it is moderately soft, malleable, and ha ...

. Later she co-founded a home for children and young adults in need of psychological therapy. She was killed by Nazis at

Treblinka extermination camp Treblinka () was the second-deadliest extermination camp to be built and operated by Nazi Germany in occupied Poland during World War II. It was in a forest north-east of Warsaw, south of the village of Treblinka in what is now the Mas ...

in 1942.

Early life and education

Horovitz was born in Warsaw on 17 April 1887. Her father was the artist Leopold Horovitz, a successful painter known for Baroque style portraiture. Her mother's maiden name was Rosa London and she had one sister. The family moved to Vienna around 1890. She was educated at the University of Vienna beginning in 1907, earning a PhD in organic chemistry in 1914. Her advisor was

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 ...

and her doctoral research was on the rearrangement of quinone using sulfuric acid.

Scientific career

At the recommendation 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 ...

, Horovitz was recruited by Otto Hönigschmid at the

Institute for Radium Research, Vienna The Institute for Radium Research is an Austrian research institute associated with the Austrian Academy of Sciences, Vienna. The Institute's researchers won multiple Nobel Prizes. Due to the gradual change of interests, "nuclear physics" was add ...

in 1913 or 1914. At this time, the

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 ...

was a recent development in radiochemistry. It predicted that lead resulting from the radioactive decay of uranium or thorium would have different atomic weights than typical lead. Early experimental data was not considered authoritative by analytical chemists. Hönigschmid had studied under leading expert Theodore Williams Richards at Harvard and his work in determining precise atomic weights was well respected. Hönigschmid was asked by Fajans and Soddy to determine the atomic weight of lead from radioactive sources to demonstrate the existence of isotopes. Horovitz undertook the laborious process of separating, purifying, and measuring lead with fine accuracy. First, she isolated lead from uranium-rich pitchblende samples from the nearby St. Joachmistal mine. The purification process involved many rounds of washing, dissolving, filtering, and recrystallization to yield a lead chloride sample completely free of contamination. Her gravimetric analysis to the thousandth of a gram proved that lead created from the radioactive decay of uranium had a lower atomic weight (206.736) than typical lead (207.190). This was the first widely accepted experimental proof that elements could have different atomic weights depending on the source. Horovitz and Hönigschmid later proved that ionium, a radioactive element discovered by

Bertram Boltwood Bertram Borden Boltwood (July27, 1870August15, 1927) was an American pioneer of radiochemistry. Boltwood attended Yale University, became a professor there and in 1910 was appointed chair of the first academic department of radiochemistry. He est ...

, was in fact an isotope of

. This experimental work disproved the existence of a widely accepted element and established thorium as a second element with isotopes. The two scientists co-published their work, and Horovitz was publicly recognized as a contributor both by Hönigschmid and Soddy. This recognition is notable because at the time it was common for female scientists to be limited to assistant positions. However, after Hönigschmid's death Horovitz's name seems to have been dropped and her contribution nearly forgotten.

Later years and circumstances of death

After World War I, Horovitz's career was disrupted by family matters and political upheaval. In a major career shift, she established a foster home in Vienna providing therapy for children with Alice Friedmann, an Adlerian psychologist. She returned to Warsaw with her sister in 1937, and Nazis descended on the city forming a Jewish ghetto in 1940. Her exact date of death is unknown. Correspondence from

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 ...

indicates that she returned to Warsaw and was killed by the Nazis in 1940. Other sources explain that Horovitz and her sister reported themselves to

Umschlagplatz ''Umschlagplatz'' () was the term used during The Holocaust to denote the holding areas adjacent to railway stations in occupied Poland where Jews from ghettos were assembled for deportation to Nazi death camps. The largest collection point ...

in 1942 to avoid endangering others, but the details are unclear. They were transported to the

and were among 900,000 Jews who did not survive there. Records indicate Horovitz was murdered in a gas chamber in 1942.

Published works

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References

{{DEFAULTSORT:Horovitz, Stefanie 1887 births Date of death unknown 1942 deaths Polish women chemists 20th-century Polish chemists Polish people who died in Treblinka extermination camp Scientists from Warsaw Jewish chemists Polish Jews who died in the Holocaust University of Vienna alumni Polish emigrants to Austria Jewish women scientists 20th-century Polish women scientists 20th-century Polish scientists