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The story of astatine takes us to Alabama, Dacca, Romania, Vienna, and California, but definitely not Switzerland.
Featured above: Berta Karlik and Traude Bernert, two of the many women involved in the search for astatine.
Langmuir’s Symptoms of Pathological Science were these:
1. The maximum effect that is observed is produced by a causative agent of barely
detectable intensity, and the magnitude of the effect is substantially independent of
the intensity of the cause.
2. The effect is of a magnitude that remains close to the limit of detectability; or,
many measurements are necessary because of the very low statistical significance
of the results.
3. Claims of great accuracy.
4. Fantastic theories contrary to experience.
5. Criticisms are met by ad hoc excuses thought up on the spur of the moment.
6. Ratio of supporters to critics rises up to somewhere near 50% and then falls
gradually to oblivion
His entire speech is a bit dense, but you can have a look for yourself here. If reading it is making you a bit drowsy, I recommend skipping to page 13.
Astatine was one of the several elements predicted to exist by Dmitry Mendeleev back when he first drew up a periodic table. He called it “eka-iodine,” following a common schema for his placeholder names of predicted elements. Wherever his predicted elements belonged on the table, he’d take the name of the element directly above and add the prefix “eka.” Eka-boron, eka-silicon, eka-manganese, et cetera. “Eka” was the Sanskrit word for “one,” so he was basically calling them “boron-plus-one,” “silicon-plus-one,” and so on. In very rare instances, theorists sometimes used the prefixes dvi- and tri-, for two or three places lower on the periodic table.
But there exists a world of difference between proposing something’s existence and proving that thing’s existence. That was especially true for astatine. It gained notoriety in the early 20th century for being one of the most elusive elements that scientists were looking for.
It even made the pages of Time magazine in 1931, where it was dubbed “the rarest and most fugitive thing on earth.”1 Thankfully, chemists finally did apprehend the rogue atom, so we shouldn’t have nearly as much trouble learning about it today.
You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each episode, we take a look at the fascinating true stories behind one element on the periodic table.
Today, we’ll peer down the spectroscope at astatine.
The writers at Time were more accurate than they might have known in their assessment of element 85, because astatine is the rarest element to naturally occur on Earth. In the entirety of the planet’s crust, there are only a few grams of astatine.
The element is one of the halogens, those caustic, highly reactive elements from fluorine down. Astatine would probably be a lot like the others, but it’s hard to know for sure — it’s exceptionally difficult to study, thanks to its aforementioned rarity as well as its radioactivity. It’s predicted to be a little odd compared to its siblings — pretty much all of the elements near the bottom of the table are. Things start to get a little weird down there. While the others in this file are nonmetallic and diatomic, with an existential preference for the gaseous state of matter, there’s a good chance astatine is a monatomic solid, and it sits right in that blurred demarcation between metals and nonmetals.2
Much like technetium, element 85 has a long history of scientists claiming its discovery, only for those claims to later be invalidated. Those scientists weren’t hacks, though. Many of them are among the most respected names in chemistry, even if they’re not quite household names like the Curies. Why don’t we meet a few of them?3
Fred Allison was born on the fourth of July, 1882, and his intelligence was apparent from the start. Right after graduating from Emory and Henry College, he became a professor of algebra, history, and English. He did that for a couple of years until the college president suggested that he pursue an advanced degree. And he did. For the next thirteen years, he would alternate, spending one year working on his science degree at Johns Hopkins University, then one year teaching science at Emory and Henry. In his free time, he headed the school’s physics department — which, incidentally, didn’t exist until Allison founded it.4 5
His studies involved lots of work with magnetism, light, and thermodynamics, and in the course of his research, he devised a new approach to spectroscopy: the Allison magneto-optic method. He used his eponymous method to measure time lag in the Faraday effect — or, as Scientific American helpfully explains, “the rotation of plane polarized light carried out by the application of a magnetic field to any particular solution of a substance.”
For our purposes, we can simply say that he would generate a magnetic field around a thing, then observe what happened when he shot light at it. In this way, he could identify which elements were present in said thing.
Using this method, in 1935, he claimed to discover a new element within a sample of monazite sand — element 85. He dubbed it “alabamine” after the state where he lived.
There’s nothing wrong with magneto-optical spectroscopy, per se, except that he was eyeballing his measurements. No precise tools used here — the recorded results were just what Allison thought he saw.
Naturally, this cast some doubt on his discoveries, once word got out. A scientist named Francis Slack built his own magneto-optical instrument, completely to spec, but he and his grad students at Vanderbilt were completely unable to replicate Allison’s results. No one else was able to, either. His discoveries were considered invalid.6
You may remember Irving Langmuir as the last person to speak with Gilbert N. Lewis before the latter was found dead on his laboratory floor. He would probably prefer to be remembered for something else, and he did accomplish a lot throughout his career. He was influential to the fields of electricity, fluids, plasma physics, meteorology, and more. He was highly respected by anyone who knew his name (Lewis notwithstanding).
In 1953, Langmuir gave a now-legendary talk about “pathological science.” That was his name for the circumstance where a researcher convinces themselves their experiment got the result they wanted to get. For instance, Charles believes there are canals on the surface of Mars. When he looks through the telescope and sees long, straight trenches on the planet’s surface, he deduces that those are evidence of canals on Mars.
“There is no dishonesty involved,” Langmuir explained, but “people are tricked into false results by a lack of understanding about what human beings can do to themselves in the way of being led astray by subjective effects, wishful thinking, or threshold interactions.”
He had a handful of examples, like cases where people found so-called “evidence” of UFOs or ESP. But his first illustration was the case of Fred Allison and his magneto-optical spectroscopy. He called it “one of the most extraordinary of all” cases of pathological science.
Like Langmuir said, there was no dishonesty here — Allison wasn’t a charlatan. He was actually a pretty great physicist with a long career after that, but nothing quite matched the infamy he earned over the Allison effect and his mistaken claims of discovery.
Well — sort of. It seems like it depends who you ask. For instance, the Auburn University College of Science and Mathematics is happy to claim that Fred Allison was “a renowned laboratory physicist [who] also discovered astatine (originally called alabamine),” and leave it at that.7
The next claim to discovery was made in 1937 by Rajendralal De. He was a chemist in Dacca, which today is the capital of Bangladesh, but at the time was part of India, which at the time was occupied by the British. He proposed the name “Dakin,” which seems like a reference to his hometown, but it’s hard to say. Very little is known about De. In the 1920s, he studied under Lise Meitner and Otto Hahn in Germany — those two will become important in future episodes — and his work continued into the 1970s.8 Alas, as one book puts it, “Information on the life of Rajendralal De seems to have vanished with his person.”9
Whoever he was, his claim is considered baseless, because if he really had been handling as much astatine as he claimed, he would have been obliterated by its radiation.
Six thousand kilometers away, Horia Hululbei and Yvette Cauchois actually might have been on to something. Both of them had studied under Jean Perrin, and Hulubej under Marie Curie. By the time they opened their lab in Romania, they were considered the experts on x-ray radiation. Cauchois might be the greatest woman in science you’ve never heard of (although there’s a lot of competition for that title).10 11 12 13 14 15
She graduated from the Sorbonne, where she would eventually teach and become the Chair of Chemical Physics, and she later became the President of the French Society of Physical Chemistry. She earned nearly a dozen medals and awards throughout her long career, and she never lost steam.
In 1999, she had a conversation with an Orthodox monk — it must have been quite a profound conversation, because she converted and was baptized in the Romanian Orthodox religion. Sadly, she contracted bronchitis during the trip, and died only a few days later. Cauchois was buried at the monastery she had just visited, and in her will, she also left them all her money.
But back in the 1930s, she and Hulubei were using x-ray spectroscopy to hunt down elements 85 and 87. They were bombarding radon with radiation and examining the resulting spectrum — with scientific instruments, it’s worth noting, not just just taking a casual look. They found an emission line at 151 siegbahns — precisely what was expected for eka-iodine.
They published papers on this work in 1936 and 1939, and a former student of theirs was able to replicate their results. It was looking pretty likely that element 85 had been found.
In 1942, those results were replicated yet again, this time by two Austrian women, Berta Karlik and Traude Bernert. At the time it was exceptionally rare to see one woman doing scientific research, let alone a team of two! They were regarded highly, too, for their work at the Institute for Radium Research in Vienna.16 17
Independently, they might have found element 85 using similar methods in 1942, and their work highlighted how previous claims were invalid. They knew nothing about Hulubei and Cauchois — the occupying Germans made international collaboration rather difficult.
And there were yet more teams in the race for element 85! There was a team at Berkeley that included our old friend Emilio Segre, and they took a different approach to the search. They were trying to synthesize the element, the same way they produced technetium a few years earlier — and in this pursuit they were successful, no question about it.18
Physicists Walter Minder and Alice Leigh-Smith also made claims of finding element 85, but said claims were spurious. No one could replicate their results, and what’s most notable about this attempt was that they proposed a couple of names. First, “helvetia,” after the Roman word for Switzerland. When that research was debunked, they came back with slightly revised work and said, “How about anglohelvetium?”19 20 21
As the dust of the war started to settle, the scientific community started to sort things out. Hulubei wrote a paper emphasizing his claim of first discovery, and noted Karlik and Bernert’s later work by saying — not incorrectly — that it supported his findings. He also suggested the name “dor” or “dorium,” short for saying “longing for peace” in Romanian.
Friedrich Paneth swooped in to untangle this knot. He was an Austrian radiochemist, a high-ranking member of the International Union of Pure and Applied Chemistry, and he was going to decide the names for disputed elements — not just element 85, but 43, 75, and others, too.22 23
His decisions were published as an editorial in Nature in 1947. The Berkeley team was recognized as the undisputed discoverers of element 85, and they were given the privilege of naming the element. They’re the ones who came up with “astatine”: from the Greek “astatos,” meaning “unstable,” plus the “ine” suffix used by all the other halogens.
Later in the editorial, Paneth addresses all the other work people had done in pursuit of element 85. Leaning pretty heavily on the work of Karlik and Bernert, he said, quite definitively, that all “former claims” to the element’s discovery had been disproven.
That’s correct in most cases, but the research he was citing said nothing about Charcois and Hulubei’s work. It was neither refuted nor even addressed by name in Paneth’s editorial, nor in Karlik and Bernert’s papers.
But what was done was done. Paneth wasn’t going to retract what he had published. Plus, Hulubei’s credibility had been damaged when he had also claimed to have discovered element 87 — a claim that was unequivocally disproven.
None of this hullabaloo ruined anybody. Pretty much everyone involved went on to have long and illustrious careers that contributed to science in other ways that were just as important. Still, Charcois and Hulubei must have felt a bit of a sting whenever someone mentioned “astatine.” I can only hope it would put their souls at ease if they knew their story would be told some 80 years later, on a podcast.
The longest-lived isotope of astatine only has a half-life of 8 hours-ish, which makes acquisition and display somewhat problematic. If you did seek out this ephemeral element, your sample would have to be microscopic — not only would that be extremely difficult, but its sheer radioactivity would be highly hazardous. It was a pretty big deal when scientists were able to amass 5 nanograms of the stuff.
Since only a gram or two is present in all the Earth at any given time, it’s practically impossible to find a sample in nature. However, new atoms of astatine are constantly being created as part of uranium’s and thorium’s decay chains. “What’s a decay chain,” you ask? Well, you might be aware that over time, radioactive elements turn into other, stable elements. That’s what the half-life measures: the time it takes for half of the element to change into something else.
Uranium and thorium generally wind up as lead, quite a stable destination. But it’s not just a quick trip from A to B. Uranium will turn into radium, which decays into radon, which becomes polonium, and so on and so forth.24As part of this process, uranium will occasionally pop out an atom or two of astatine. It’s very rare, and that astatine only exists for a second or two before it turns into bismuth. But this process is happening constantly, untold billions of billions of quadrillions of times every day. (And that’s underselling it by billions of orders of magnitude.)
So there’s a sort of agreed-upon solution among element hunters: If you have a moderately sized chunk of the right kind of rock — granite, maybe, about the size of a baseball — there’s probably some uranium in there. If there is, then it’s certainly decaying. And every once in a while, for a brief moment in time, as part of that decomposition, the tiniest amount of astatine will flicker in and out of existence.25
It’s hard to say how often that happens. Maybe once a week, maybe once a year. But within that big old rock it does happen.
No one will dispute that.
Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To learn what Langmuir considered to be the six symptoms of pathological science, visit episodic table dot com slash A t.
Next time, we’ll see if we detect any radon.
Until then, this is T. R. Appleton, reminding you that on a geological time scale, we ourselves have only just flashed into existence.
- Science: Eka-Iodine, Time Magazine. May 18, 1931.
- Cornell Chronicle, Scientists Theorize Properties Of Fleeting Astatine. Anne Ju, September 9, 2013.
- Elementymology And Elements Multidict, Astatine. Peter van der Krogt, last updated June 13, 2016.
- The New York Times, Fred Allison, 92, Physicist, Is Dead. August 8, 1974.
- Encyclopedia Of Alabama, Fred Allison. Lindy Biggs and Stephen Knowlton, Last Updated April 25, 2013.
- Francis G. Slack,
The magneto-optic method of chemical analysis,
Journal of the Franklin Institute,
Volume 218, Issue 4,
- Auburn University College Of Science And Mathematics, History.
- The Periodic Table: Its Story And Its Significance p 328. Eric Scerri, 2019.
- The Lost Elements: The Periodic Table’s Shadow Side, p. 337. Marco Fontani, Mariagrazia Costa, Mary Virginia Orna, 2015.
- Stratan, G. Horia Hulubei, father founder of the Institute of Atomic Physics. Romania: N. p., 1999. Web.
- Mental Itch, The Interesting Discovery Of Astatine. September 16, 2020.
- Scientific American, A Tale Of Seven Elements: Element 85– Astatine [Excerpt]. Eric Scerri, July 15, 2013.
- Christiane Bonnelle , “Yvette Cauchois“, Physics Today 54, 88-89 (2001) https://doi.org/10.1063/1.1372125
- IFIN HH, Brief History.
- Academie de Poitiers, Quelques Portraits: Yvette Cauchois. April 27, 2006. Machine translated from French.
- LiveScience, Facts About Astatine. Rachel Ross, May 23, 2017.
- Women In Their Element: Selected Women’s Contributions To The Periodic System, p. 352. Edited by Annette Lykknes, Brigitte Van Tiggelen, 2019.
- Corson, D., MacKenzie, K. & Segre, E. Astatine : The Element of Atomic Number 85. Nature 159, 24 (1947). https://doi.org/10.1038/159024b0
- Leigh-Smith, A., Minder, W. Experimental Evidence of the Existence of Element 85 in the Thorium Family. Nature 150, 767–768 (1942). https://doi.org/10.1038/150767a0
- The Lost Elements: The Periodic Table’s Shadow Side, p. 345. Marco Fontani, Mariagrazia Costa, Mary Virginia Orna, 2014.
- Compound Interest, A Periodic Table Of Rejected Element Names. January 30, 2016.
- Koppenol, W. (2005), Paneth, IUPAC, and the Naming of Elements. HCA, 88: 95-99. https://doi.org/10.1002/hlca.200490300
- Encyclopedia Britannica, Friedrich Adolf Paneth. The Editors Of Encyclopedia Britannica, last updated September 13, 2020.
- Couturier, Olivier & Supiot, Stephane & Mougin-Degraef, Marie & Faivre-Chauvet, Alain & Carlier, Thomas & Chatal, Jean-François & Davodeau, Francois & Chérel, Michel. (2005). Cancer radioimmunotherapy with alpha-emitting nuclides. European journal of nuclear medicine and molecular imaging. 32. 601-14. 10.1007/s00259-005-1803-2.
- PeriodicTable.com, Astatine. Theodore Gray, last updated October 28, 2017.
8 Replies to “85. Astatine: Pathological Science”
So he predicted the element but not predicted the details, such as properties?
He predicted that it would have some behaviors in common with the other halogens, but that’s about it.
But element 85 is not the element with the shortest half time outside of the super heavy elements
Right, there are elements we’ll hit soon that have shorter half-lives.
Anyway, there is a rare nuclear decay chain that generates this element that starts at neptunium which is in trace amounts naturally which is the reason why it is so rare
True. At 217 is a descendant of Np 237. But Np 237 itself requires two neutron captures in order to form, neutrons which result from the spontaneous fission of U 238. It happens, but everything about the process is unlikely. At 217 does form, but in amounts best described in terms of atoms per planet. Nearly all natural astatine is At 218, which is in the decay chain going from U 238 to Pb 206.
I was a bit disappointed on a couple of points. First, synthetic astatine and francium consist of light nuclides with neutron counts at or below 126. Naturally-occurring astatine and francium consist of heavy nuclides with neutron counts well above 126. Those two elements illustrate the importance of neutron shell closure at N = 126. Second, the ratio of At 218 to U 238 concentration is precisely known, as is uranium concentration in a variety of materials. It looks like, on average, you need around 800 moles of granite to be sure of having an At 218 atom. That portion of the script could have been more precise. Finally, please edit that statement “billions of orders of magnitude. I’m quite sure that’s not what you meant.
On the whole, though, great article. I already knew just enough of the story to have confidence in what you say..