The black deception of actinium

The black deception of actinium

‘Worthless’ was the miners’ judgment for centuries about a black mineral that was found, among other things, in the silver and cobalt mines in the Ore Mountains on the border of the Czech Republic and Germany. Bad luckblende the miners called it black fraud. They did not notice that the mineral was also quite radioactive. But for chemists, this pitch blende became a gold mine. The previously unknown element uranium was isolated from it as early as 1789 (although it later turned out to be uranium oxide) and around 1900 Marie and Pierre Curie had many tons of this uranium ore delivered to their Paris laboratory. The stuff was full of uranium decay products and was the basis for their discovery of polonium and radium.

And thanks to pitchblende, the radioactive metal actinium was also discovered. At least, that is what one of the Curies’ assistants, André Debierne (1874-1949), has always claimed. The famous Curies have always supported their young pupil and family friend in this. And still, as in the fascinatingly thick Chemistry of the Elements from 1997, but also in more recent studies, the discovery of actinium is unconcernedly attributed to Debierne.

Because didn’t he already publish his discovery of that radioactive element that was so similar to thorium in 1900? The fact that the German industrial chemist Friedrich Oskar Giesel (1852-1927) announced his discovery of emanium four years later, with the same characteristics, seems like a must after dinner. And the fact that Giesel gives up his name ’emanium’ in favor of actinium after just a few years also seems to confirm Debierne’s priority. And that Debierne initially gave his element the wrong atomic number 87, and Giesel immediately published the correct number, 89, oh well.

Quinine factory in Braunschweig

But it has now become clear from various scientific-historical studies that Debierne probably did not actually find actinium, but one of the many isotopes of thorium. In 1900 he also described his research procedure rather vaguely. Friedrich Giesel, a chemist at a quinine factory in Braunschweig, immediately became interested in Debierne’s discoveries. Giesel’s many requests for more information received no response from Paris. But after Giesel’s publication of emanium, Debierne suddenly becomes active and he declares in a lecture that the German emanium is the same as his actinium. But the procedure that Debierne uses is the same as that Giesel clearly explained in his publication, not his own unclear procedure. Giesel travels to Paris shortly afterwards. After much hassle, Marie and Pierre Curie decide to send a specimen from Giesel and one from Debierne to London, where the chemist William Ramsay can settle the matter. But not an old specimen from Debiernes is going to London, but a new preparation – according to Giesel’s method. So Ramsay decides in favor of actinium.

As German chemist Siegfried Niese wrote in 2017, a German industrial chemist at that time could not compete with the world-famous Curies, who had just been awarded the Nobel Prize in 1903. And as a researcher without a university appointment, Giesel did not count very much in the scientific community. But his memorial stone in a cemetery in Braunschweig proudly reads: ‘Entdecker des Aktiniums‘.




SCIENCE