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The discovery of polonium and radium by pierre and marie curie

On the other hand, the uranic rays, discovered in 1896 by Henri Becquerel, raised a puzzling problem. Uranium compounds and minerals appeared to maintain an undiminished ability to blacken a photographic plate over a period of several months. What was the source of this inexhaustible energy that apparently violated the Carnot principle that energy can be transformed but never be created or destroyed?

Pierre Curie, already a famous physicist for his work on magnetism and crystal symmetry, had a feeling that the phenomenon was quite extraordinary, and he helped his wife reach a decision in her choice of thesis topic.

One reason was the proliferation of false or doubtful observations of radiation similar to uranic rays in a variety of substances.

However, within eight months in 1898 she discovered two elements, polonium and radium, founding a new scientific field—radioactivity.

In addition to blackening a photographic plate, uranic rays rendered air conductive for electricity. This later property was much more amenable to quantitative measurement.

Becquerel had used electroscopes, but the measurements were unreliable. At this point, little progress would have been made without the genius of Pierre Curie. In 1880, together with his brother Jacques, he had discovered piezoelectricity i. He invented a device by which the charges produced by uranium in an ionization chamber were compensated for by opposite charges in known amounts produced by applying a weight to a leaf of quartz.

The compensation was followed by a second invention, the quadrant electrometer. The emission of uranic rays could now be quantified from the weight and the time required for compensation of the charges produced in the ionization chamber.

Beginning on 11 February 1898, she tested all samples at hand or borrowed from various collections, including a large number of rocks and minerals, taking the activity of metallic uranium as a reference. She found that all compounds and minerals that contained uranium were active and that pitchblende, a massive variety of uraninite from the Joachimasthal mine in Austria, as well as chalcolite, a natural uranium phosphate, were more active than metallic uranium itself.

At this stage, the hunt for the supposed element became a matter of paramount importance and urgency. On 18 March he abandoned his own research projects and joined his wife in the venture. In the course of the systematic search of Becquerel rays, Marie Curie also discovered, on 24 February, that thorium compounds were also active.

However, the German physicist Gerhardt Schmidt had observed the emission several weeks earlier. The Discovery of Polonium: It became necessary the discovery of polonium and radium by pierre and marie curie separate and identify a substance whose chemical properties were unknown.

However, the hypothetical element could be followed by tracing its radioactivity. Marie Curie explained the process: It consists of separations performed with the ordinary procedures of analytical chemistry and in the measurement of the radioactivity of all compounds separated. In this way, one can recognize the chemical character of the radioactive element sought; the latter is concentrated in fractions which become increasingly radioactive in the course of the separation.

On 14 April, the trio began research on pitchblende, which was two and a half times more active than uranium. Several procedures were used in parallel runs by precipitations with various reagents and sublimations of solid deposits, whereby the active substance accompanied primarily bismuth, from which it could be progressively separated.

Marie and Pierre Curie and the discovery of polonium and radium

On 27 June, Marie Curie precipitated sulfides from a solution containing lead, bismuth, and the active substance. She underlined the result in her notebook: On 18 July, Pierre Curie obtained a deposit 400 times more active than uranium.

The symbol Po, written by Pierre Curie, appears in the notebook on 13 July. The name polonium had a provocative significance because Poland had disappeared as a state in 1795, being divided between Prussia, Russia, and the Austrian Empire.

The publication signed both by Pierre Curie as first author and Marie Curie, was based on experiments performed from the discovery of polonium and radium by pierre and marie curie April to 16 July. The title is historic: It proclaims that the search for the element more active than uranium was successful, and the word radio-active appears for the first time The Curies dropped the hyphen the following year.

It was customary that no such claim was considered valid until a pure substance had been isolated, the atomic weight of the element had been determined, and its spectral lines had been measured. They considered the entire material as a mixture. They knew nothing of radioactive decay. In this sense it was purely a matter of chance since the experiments were performed within three months, a relatively short time with respect to the 138-day half-life of polonium.

Pierre and Marie Curie handling the electrometer. It was only a few years later that the authors noticed with astonishment and great perplexity that polonium was progressively disappearing, still unaware of its half-life. They were preoccupied with the authenticity of polonium for several years, and with their customary honesty they did not hide their doubts. In 1899, Marie Curie still raised the question: The spark spectrum of this sample revealed for the first time a few lines characteristic of the element.

The note in the Comptes Rendus concluded the short story of polonium for several years. Marie Curie maintained a strong sense of ownership for the element, which she defended with considerable emotion and vehemence.

Curies isolate radium

In a sense she was correct: The Discovery of Radium: Second, they found that a radioactive substance could be concentrated by fractional crystallization from barium chloride contained in pitchblende.

They pursued this operation until the activity of the chlorides was 900 times greater than that of uranium. Their third and last argument was decisive. This time the spectroscopic analysis was successful. Marie Curie maintained a strong sense of ownership for the element [polonium], which she defended with considerable emotion and vehemence. In December 1898, the Austrian government offered the Curies a first batch of 100 kg of uranium-free residue from the treatment of the Joachimsthal pitchblende.

With the foregoing discovery of polonium, the Curies had oddly enough begun with the most difficult part of the work. In its own right, radium had outstanding advantages: He was research student of Marguerite Perey who was assistant of Marie Curie and discoverer of francium.

See the References section for works cited in this article. Page last modified 15 February 2011.

  • It was attended by the most prominent personalities in France, including Aristide Briand , then Foreign Minister, who was later, in 1926, to receive the Nobel Peace Prize;
  • She declared that she also regarded this Prize as a tribute to Pierre Curie;
  • A group of some ten children were accordingly taught only by prominent professors;
  • For reasons that would not be fully understood until the concept of radioactive decay was developed, Marie never succeeded in isolating polonium, which has a half-life of only 138 days;
  • She was the first woman to win a Nobel Prize;
  • Their dearest wish was to have a new laboratory but no such laboratory was in prospect.

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