Editing Marie Curie (section)

=== New elements ===
[[File:Pierre and Marie Curie.jpg|thumb|Pierre and Marie Curie in the laboratory, {{circa|1904|lk=no}}]]
In 1895, [[Wilhelm Röntgen]] discovered the existence of [[X-ray]]s, though the mechanism behind their production was not yet understood.<ref name="Marie Curie and the Science of Radioactivity" /> In 1896, [[Henri Becquerel]] discovered that [[uranium]] salts emitted rays that resembled X-rays in their penetrating power.<ref name="Marie Curie and the Science of Radioactivity" /> He demonstrated that this radiation, unlike [[phosphorescence]], did not depend on an external source of energy but seemed to arise spontaneously from uranium itself. Influenced by these two important discoveries, Curie decided to look into uranium rays as a possible field of research for a thesis.<ref name="Estreicher1938a" /><ref name="Marie Curie and the Science of Radioactivity" />

She used an innovative technique to investigate samples. Fifteen years earlier, her husband and his brother had developed a version of the [[electrometer]], a sensitive device for measuring electric charge.<ref name="Marie Curie and the Science of Radioactivity" /> Using her husband's electrometer, she discovered that uranium rays caused the air around a sample to conduct electricity. Using this technique, her first result was the finding that the activity of the uranium compounds depended only on the quantity of uranium present.<ref name="Marie Curie and the Science of Radioactivity" /> She hypothesized that the radiation was not the outcome of some interaction of molecules but must come from the atom itself.<ref name="Marie Curie and the Science of Radioactivity" /> This hypothesis was an important step in disproving the assumption that atoms were indivisible.<ref name="Marie Curie and the Science of Radioactivity" /><ref name="Reid1974e" />

In 1897, her daughter [[Irène Joliot-Curie|Irène]] was born. To support her family, Curie began teaching at the {{Lang|fr|[[École normale supérieure]]|italic=no}}.<ref name="Estreicher1938b" /> The Curies did not have a dedicated laboratory; most of their research was carried out in a converted shed next to ESPCI.<ref name="Estreicher1938b" /> The shed, formerly a medical school dissecting room, was poorly ventilated and not even waterproof.<ref name="Marie Curie and the Science of Radioactivity 2" /> They were unaware of the deleterious effects of [[Radioactive contamination|radiation exposure]] attendant on their continued unprotected work with radioactive substances. ESPCI did not sponsor her research, but she received subsidies from metallurgical and mining companies and from various organisations and governments.<ref name="Estreicher1938b" /><ref name="Marie Curie and the Science of Radioactivity 2" /><ref name="Marie Curie – Student in Paris 2" />

Curie's systematic studies included two uranium minerals, [[pitchblende]] and [[torbernite]] (also known as chalcolite).<ref name="Marie Curie and the Science of Radioactivity 2" /> Her electrometer showed that pitchblende was four times as active as uranium itself, and chalcolite twice as active. She concluded that, if her earlier results relating the quantity of uranium to its activity were correct, then these two minerals must contain small quantities of another substance that was far more active than uranium.<ref name="Marie Curie and the Science of Radioactivity 2" /><ref name="Reid1974f" /> She began a systematic search for additional substances that emit radiation, and by 1898 she discovered that the element [[thorium]] was also radioactive.<ref name="Marie Curie and the Science of Radioactivity" /> Pierre Curie was increasingly intrigued by her work. By mid-1898 he was so invested in it that he decided to drop his work on crystals and to join her.<ref name="Estreicher1938b" /><ref name="Marie Curie and the Science of Radioactivity 2" />

{{blockquote|The [research] idea [writes Reid] was her own; no one helped her formulate it, and although she took it to her husband for his opinion she clearly established her ownership of it. She later recorded the fact twice in her biography of her husband to ensure there was no chance whatever of any ambiguity. It [is] likely that already at this early stage of her career [she] realized that... many scientists would find it difficult to believe that a woman could be capable of the original work in which she was involved.<ref name="Reid1974g" />}}
[[File:Marie Pierre Irene Curie.jpg|thumb|Pierre, [[Irène Joliot-Curie|Irène]], and Marie Curie, {{circa|1902|lk=no}}]]
She was acutely aware of the importance of promptly publishing her discoveries and thus establishing her [[scientific priority|priority]]. Had not Becquerel, two years earlier, presented his discovery to the [[French Academy of Sciences]] the day after he made it, credit for the discovery of radioactivity (and even a Nobel Prize), would instead have gone to [[Silvanus Thompson]]. Curie chose the same rapid means of publication. Women were not eligible for membership of the Académie des Sciences until 1979, so that all her presentations had to be made for her by male colleagues;<ref name="Spinney2024">{{cite news |last=Spinney |first=Laura |title=The Elements of Marie Curie by Dava Sobel review – the great scientist who created her own school |newspaper=The Guardian |date=11 November 2024 |url=https://www.theguardian.com/books/2024/nov/11/the-elements-of-marie-curie-by-dava-sobel-review-the-great-scientist-who-created-her-own-school}}</ref> her paper, giving a brief and simple account of her work, was presented for her to the {{langn|fr|Académie}} on 12 April 1898 by her former professor, [[Gabriel Lippmann]].<ref name="Reid1974h" /> Even so, just as Thompson had been beaten by Becquerel, so Curie was beaten in the race to tell of her discovery that thorium gives off rays in the same way as uranium; two months earlier, [[Gerhard Carl Schmidt]] had published his own finding in Berlin.<ref name="Reid1974b" />
At that time, no one else in the world of physics had noticed what Curie recorded in a sentence of her paper, describing how much greater were the activities of pitchblende and chalcolite than that of uranium itself: "The fact is very remarkable, and leads to the belief that these minerals may contain an element which is much more active than uranium." She later would recall how she felt "a passionate desire to verify this hypothesis as rapidly as possible."<ref name="Reid1974b" /> On 14 April 1898, the Curies optimistically weighed out a 100-gram sample of pitchblende and ground it with a pestle and mortar. They did not realise at the time that what they were searching for was present in such minute quantities that they would eventually have to process tonnes of the ore.<ref name="Reid1974b" />

In July 1898, Curie and her husband published a joint paper announcing the existence of an element they named "[[polonium]]", in honour of her native Poland,<ref>{{cite journal |last1=Curie |first1=P. |last2=Curie |first2=M. |title=Sur une substance nouvelle radio-active, contenue dans la pechblende |trans-title=On a new radioactive substance contained in pitchblende |language=fr |journal=Comptes rendus |volume=127 |pages=175–178 |date=1898 |url=https://www.academie-sciences.fr/pdf/dossiers/Curie/Curie_pdf/CR1898_p175_178.pdf |url-status=live |archive-url=https://archive.org/details/surunesubstancen127curi/page/177/mode/1up?q=polonium |archive-date=23 July 2013 |quote=Si l'existence de ce nouveau métal se confirme, nous proposons de l'appeler polonium, du nom du pays d'origine de l'un de nous. |trans-quote=If the existence of this new metal is confirmed, we propose to call it polonium, after the country of origin of one of us.}} [http://web.lemoyne.edu/~giunta/curiespo.html English translation.]</ref> which would for another twenty years remain [[partitions of Poland|partitioned among three empires]] ([[Russian Empire|Russia]], [[Austrian Empire|Austria]], and [[German Empire|Prussia]]).<ref name="Estreicher1938a" /> On 26 December 1898, the Curies announced the existence of a second element, which they named "[[radium]]", from the Latin word for 'ray'.<ref name="Estreicher1938b" /><ref name="Marie Curie and the Science of Radioactivity 2" /><ref name="LawrenceBerkeleyNationalLaboratory2000" /><ref>{{cite journal |year=1898 |title=Sur une nouvelle substance fortement radio-active, contenue dans la pechblende |trans-title=On a new, strongly radioactive substance contained in pitchblende) |journal=Comptes rendus |volume=127 |pages=1215–1217 |url=https://www.biodiversitylibrary.org/page/3731197#page/813/mode/1up |last1=Curie |first1=Pierre |last2=Curie |first2=Marie |last3=Bémont |first3=Gustave |quote=Les diverses raisons que nous venons d’énumérer nous portent à croire que la nouvelle substance radioactive renferme un élément nouveau, auquel nous proposons de donner le nom de radium. |trans-quote=The various reasons we have just listed lead us to believe that the new radioactive substance contains a new element, which we propose to give the name radium. |language=fr}}   [http://www.aip.org/history/curie/discover.htm English translation] {{Webarchive|url=https://web.archive.org/web/20090806083923/http://www.aip.org/history/curie/discover.htm |date=6 August 2009 }}</ref> In the course of their research, they also coined the word "[[radioactivity]]".<ref name="Estreicher1938a" />
[[File:Pierre Curie (1859-1906) and Marie Sklodowska Curie (1867-1934), c. 1903 (4405627519).jpg|thumb|Pierre and Marie Curie, {{circa|1903|lk=no}}]]
To prove their discoveries beyond any doubt, the Curies sought to isolate polonium and radium in pure form.<ref name="Marie Curie and the Science of Radioactivity 2" /> Pitchblende is a complex mineral; the chemical separation of its constituents was an arduous task. The discovery of polonium had been relatively easy; chemically it resembles the element [[bismuth]], and polonium was the only bismuth-like substance in the ore.<ref name="Marie Curie and the Science of Radioactivity 2" /> Radium, however, was more elusive; it is closely related chemically to [[barium]], and pitchblende contains both elements. By 1898 the Curies had obtained traces of radium, but appreciable quantities, uncontaminated with barium, were still beyond reach.<ref name="Williams1986 pp331–332" /> The Curies undertook the arduous task of separating out radium salt by differential [[crystallisation]]. From a tonne of pitchblende, one-tenth of a gram of [[radium chloride]] was separated in 1902. In 1910, she isolated pure radium metal.<ref name="Marie Curie and the Science of Radioactivity 2" /><ref name="Williams1986 p332" /> She never succeeded in isolating polonium, which has a [[half-life]] of only 138 days.<ref name="Marie Curie and the Science of Radioactivity 2" />

Between 1898 and 1902, the Curies published, jointly or separately, a total of 32 scientific papers, including one that announced that, when exposed to [[radium]], diseased, [[tumor|tumour-forming]] cells were destroyed faster than healthy cells.<ref>"Marie Sklodowska Curie", ''Encyclopedia of World Biography'', 2nd ed., vol. 4, Detroit, Gale, 2004, pp. 339–41. [[Gale Virtual Reference Library]]. Web. 3 June 2013.</ref>

In 1900, Curie became the first woman faculty member at the École Normale Supérieure and her husband joined the faculty of the University of Paris.<ref name="Marie Curie and the Science of Radioactivity 3" /><ref name="Quinn1996" /> In 1902 she visited Poland on the occasion of her father's death.<ref name="Estreicher1938b" />

In June 1903, supervised by [[Gabriel Lippmann]], Curie was awarded her doctorate from the [[University of Paris]].<ref name="Estreicher1938b" /><ref name="Mould1998" /> That month the couple were invited to the [[Royal Institution]] in London to give a speech on radioactivity; being a woman, she was prevented from speaking, and Pierre Curie alone was allowed to.<ref name="Marie Curie Rec and Dis" /> Meanwhile, a new industry began developing, based on radium.<ref name="Marie Curie and the Science of Radioactivity 3" /> The Curies did not patent their discovery and benefited little from this increasingly profitable business.<ref name="Marie Curie and the Science of Radioactivity 2" /><ref name="Marie Curie and the Science of Radioactivity 3" />