February 27, 2024

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The black deception of actinium

The black deception of actinium

The black metal found, among other things, in silver and cobalt mines in the Ore Mountains on the border of the Czech Republic and Germany, was for centuries ruled by miners as “worthless.” Bad luck blind The miners called it black fraud. They did not notice that the metal was also completely radioactive. But for chemists, this mixture of bitumen became a gold mine. A previously unknown uranium element was isolated from it as early as 1789 (although it was later shown to be uranium oxide) and around 1900, Marie and Pierre Curie delivered several tons of this uranium ore to their laboratory in Paris. The material was full of uranium decay products and was the basis for the discovery of polonium and radium.

Thanks to pitchblende, the radioactive mineral actinium was also discovered. At least, that's what one of Curie's assistants, André Debern (1874-1949), always claimed. The famous Curie family has always supported their young student and family friend in this matter. And still, as in wonderfully thick Chemistry of elements From 1997 but And also in modern studiesthe discovery of actinium is carelessly attributed to Debern.

Because didn't he already publish his discovery of this radioactive element that was very similar to thorium in 1900? The fact that the German industrial chemist Friedrich Oskar Gesell (1852-1927) announced his discovery of imanium four years later, with the same properties, seems like an after-dinner must-have. The fact that Gesell abandoned his name “Imanium” in favor of Actinium only a few years later also seems to confirm Debern's primacy. And that Debern initially gave his element the wrong atomic number, 87, and Geisel immediately published the correct number, 89, well.

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Quinine factory in Braunschweig

But out diverse Scientific history Search It is now clear that Debern may not have actually found actinium, but rather one of several isotopes of thorium. In 1900, he also described his research procedures somewhat vaguely. Friedrich Geisel, a chemist at the quinine plant in Braunschweig, became immediately interested in Dibbern's discoveries. Geisel's numerous requests for more information received no response from Paris. But after Geisel's publication of the imanium, Debern suddenly became active and declared in a lecture that the German imanium was the same as his own actinium. But the procedure Dibbern uses is the same procedure that Geisel clearly laid out in his post, not his own unclear procedure. Geisel travels to Paris shortly afterwards. After much trouble, Marie and Pierre Curie decide to send a sample of Giselle and one of Debern to London, where the chemist William Ramsay can settle the matter. But it is not an old sample of d'Ebernais that is going to London, but a new preparation – according to Geisel's method. So Ramsay decides in favor of actinium.

Like the German chemist Siegfried Nisse Written in 2017, the German industrial chemist at the time could not compete with the world-famous Curie, who had just been awarded the Nobel Prize in 1903. As a researcher without a university appointment, Gesell was not very important in the scientific community. But on His memorial stone A cemetery in Braunschweig proudly says:Entdecker des actiniums'.