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Discovery of Radioelement Polonium and Radium
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2007-9-26
Madam Curie individually experimented their radioactivity for many mineral specimens. Hundreds substances had been tried, no radioactivity was found. But when she was testing a uraninite and cuprouranite, there was strong radioactivity in them, with an intensity much larger than the estimated pursuant to the content of uranium and thorium. She also synthesized calcholitebased on the composition from precisely analyzing the natural cuprouranite, discovering the radioactivity of which was 4.5 times as strong as the artificial synthesized specimen. The extraordinary radioactivity of these two minerals could just interpret they contained a certain new element of little percentage and with stronger radioactivity than uranium and thorium. In June 1896 the Curies started to jointly search for this new element. Beginning from uraninite, they decomposed this ore and classified and grouped various elements with the systematic chemical analysis program. After each separation, the radiation of the two groups were determined, and decided to classify the new element into which group according to their radioactivity or the intensity of radioactivity. After several screening, they finally found there were two new radioelements in uraninite. In July 1898, they proved the existence of a new radioelement by their radioactivity, but they only got a few bismuth sulfides which were rich in this element, which had a much stronger radioactivity than that of metal uranium. How difficult it is to accumulate through chemical method this element, which only accounted for part per hundred million in uraninite. Mary named this new element "Polonium" to commemorate her homeland Poland.
Five months later, the Curies discovered another new radioelement by radioactivity, which concentrated in barium chloride crystal with the radioactivity of nine million times as strong as that of the metal uranium. They named this element "Radium", meaning "radioactive substance". Polonium was rich in the bismuth sulfide precipitation, and radium in the barium chloride crystal, which indicated they had similar chemical property as bismuth and barium, but far different from radium. However, the Curies still hadn't found any compound of radium or bismuth and decided to extract pure radium compounds from uraninite subsequently. They presumed that bismuth and radium might remain intact in the waste ore slag after uranium being extracted from uraninite, as the chemical property of bismuth and radium differed much from that of uranium. Then they bought cheap waste ore slag from the state mines disposing uraninite in Austria. From 1899 to 1902, the Curies worked for 45 months in the shabby work shed in the Physics campus and disposed two tons slag little by little. After millions of experiments of dissolution, deposition and crystallization, they finally obtain 100mg pure radium chloride with an amazingly strong radioactivity two million times of that of uranium salt. If put in a bottle, it would emit violet fluorescence, which could also enable diamond, ruby, fluorite and zinc sulphide, barium platinum cyanide, etc. to emit phosphorescence. They had a preliminary measuring of the atomic weight of radium at 225, determining its position under barium II A in Periodic Table of Elements. On June 25, 1903, the 36-year-old Madam Mary Curie passed her doctorate paper dissertation titled "Study on Radioactive Substances"; in November the same year, the Royal Society granted the Curies the David Gold Medal. On December 10, the Curies and Bekele together won the Nobel Prize in Physics of the year and shared the prize.
In 1910, Madam Curie cooperated with French chemist Debierne, A. (1874-1949), and obtained metal radium by electrolyzing radium chloride. In 1911, Madam Curie won the Nobel Prize in Chemistry, the sole female scientist who won twice Nobel Prize in the world. Maria Sk?odowska was born on November 7, 1867 in Warsaw under the rule of Russia, when Poland had been subjugated for over 100 years. While in childhood she had a strong sense of patriotism and in youth she begun to love science and determined to contribute to Poland. In 1891 she came to Paris to study and successively obtained the Postgraduate Degree in Maths and Physics with honors. She married with Physics Prof. Curie in 1895 and became the renowned science partners. Since June 1898 Curie and Mary had decided to work jointly to extract a new radioelement from uraninite until 1906 when Curie was killed by a carriage cab. Madam Curie was so grieved that she was hospitalized in sanatorium. With strong perseverance, she recovered from sorrow and afforded two daughters by herself. She took over Curie's seat of Professor of Paris University and made great contributions in establishment and development of radiation science, which won her the Nobel Prize in Chemistry 1911. The discovery of radium invoked a revolution in the science world and the Curies commenced the research of atomic energy application. As a scientist with huge contributions, Madam Curie was also a loft and unselfish person. The radium price was then very expensive, but she publicized the extraction method of radium without applying for patent. As she said, "radium as a chemical element is the property of everyone but not the means that anyone can make fortune". The huge prize she won was almost spent on her students or used to aid scientific groups. On July 4, 1934 Madam Curie died of chronic pernicious anemia and leukemia. Her doctor said, "Nobody but radium killed Madam Curie." It's undoubtedly to say that she had committed her whole life to the scientific cause.
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Organizer:
Beijing Municipal Association for Science & Technology
Undertaker: Beijing Science & Technology
Consulting Center,
Information Center of Beijing Municipal Association for
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