An illustration of cretinism from the 1800s, with an emphasis on goiter.

53. Iodine: Purple Haze

We’ll pull in our elemental haul from the sea while Lady Jane Davy spits in the ocean.

Featured above: An illustration of Styrian people with a case of cretinism. If they knew to collect iodine, this could have been avoided!

Show Notes

My British accent is sounding even worse than usual on this episode. My sincerest apologies to those of you whose ears spontaneously began to bleed. I promise I’ll recite, “With blackest moss the flower pots were thickly crusted one and all,” one hundred times while holding marbles in my mouth before the next episode. On with the show notes!

He’s Probably The Guy Who Said “Freedom Fries”: Davy really, really didn’t like the French. Maybe because of how they laughed at his wife’s tiny hat, or blind nationalism, or maybe there was something else going on, but he was downright hateful in that letter he wrote to the PM, Lord Liverpool. By his own account, his motives do not seem complicated:

My Lord, In addressing Your Lordship I am actuated by no other motive than that of patriotism by no other interest than the well being of civilized society.”

The whole letter reads like it must be covered in spittle from his frothing mouth, and in his eyes, no French person is free of sin:

Bonaparte & the army are not more than the expiatory sacrifices of France.–The sins of the people are laid upon the head of the scape goats & of the peace offering; but the Nation itself is guilty.”

Later in the (very long) letter, he starts talking about the Louvre, and I have to admit Davy raises some worthwhile questions about who “owns” treasures that were captured in conquest. But that’s pretty rich coming from an Englishman.

The letter has several spelling errors and clumsy sentences, which really makes me cast side-eye toward all the people who thought Davy was a great poet.

At one point, he starts babbling about how the French people “resemble in so many particulars the Jews,” which is always a sign you should start backing away if you weren’t already. It all makes him sound like the kind of guy who would be a big fan of Alex Jones if he were around today, and frankly, I had a much higher opinion of Davy before learning all this. Perhaps inhaling fumes from all those halogen experiments got to his head?

If you’d like to take a look at all this for yourself, see footnote number 3 about where it’s available.

Now Consider The Antikythera Mechanism: Sometimes I like to imagine what our strange little planet might look like to a visiting alien archaeologist. If said alien happened upon Humphry Davy’s medal, recovered from the sea floor off the Cornish coast, what would they think? Of all the possible scenarios they could imagine, do you really think “Granted to a country’s most eminent scientist by the emperor of a wartime enemy, then cast into the sea by his spiteful widow after he died” would even be in the top one thousand hypotheses? It’s a real privilege to live in such a bizarre world.

So What Should Ren Call Stimpy? Good news! There’s at least one more insult that the angry yet socially conscious interlocutor can use: “Fool.” It basically just means “windbag.” Oh hey, actually, that’s another one you could use! I guess I was wrong in my little postscript for this episode. But if you’re that concerned about the social dynamics behind the insults you hurl, perhaps you could be successful in sorting out your differences with others, instead?

Seriously, though, so many insults in our language have very dark origins. Take bozo, for instance: a “muscular, low-I.Q. male,” a word originally used in the slave trade. And that’s the name of a clown.

I Never Even Watched Breaking Bad: One reason iodine might be more difficult to get your hands on than it used to be is because, apparently, it’s useful in the creation of methamphetamines. I don’t know anything about that, except what I’ve read on Theodore Gray’s website. (It’s under the entry for “Antique reagent bottle.”)

He would know about these things, and yes, he has had element samples confiscated by the federal government. Element collecting will take you to some strange places!

It’s Also A Pretty Tasty Snack, BTW: This YouTuber has done an impressive job harvesting elemental iodine from seaweed, as we discussed. He performs experimentation that’s pretty dang sophisticated, using some awfully nice equipment. I don’t even want to guess how much glassware like this costs.

If you really wanted, though, you could probably figure out a way to run a simpler, less efficient version of all this in your garage. (Protip: Pool supply stores are probably the easiest place to pick up chemicals like hydrochloric acid.) This is also considerably less hazardous than some of the other experiments we’ve observed, like isolating metallic sodium, or MacGyvering thermite.

By the way… not that anyone suggested you should do this, but please don’t drop metallic sodium into sulfuric acid:

If It’s Yellow, Keep It Mellow: There’s one more notable place you can find iodine that I neglected to mention: Counterfeit detection pens.

You can see one here on the left. I had never heard of these things until I spent a couple summers working the register at Party City as a teenager. If a customer paid with any bills larger than a $20, I was supposed to mark it with one of these pens. If the mark was yellow, then it was real, legal tender. If the mark immediately darkened, then I was looking at funny money.

The marker is filled with an iodine-based ink. When the iodine reacts with starches, like the kind that are present in wood-based paper, it turns dark. What’s special about American bills is that they are not made out of paper, they’re made of a cotton-linen mix, which contains no starch.

I always wondered, but never knew how those things worked until I researched this episode! And for what it’s worth, I never ran into a single counterfeit bill. It’s probably for the best. I was so conflict-averse at the time that I probably would have apologized to the crook for the awkwardness.

Episode Script

We’re swiftly approaching the end of period five, so we’ll need to say some goodbyes. Not just to the row. After this episode, never again shall we encounter a nonmetal.

Kind of.

There’s a pretty big asterisk qualifying that statement, because several of the elements we’ll discuss in future episodes are not metals. We’ve got a couple noble gases, a handful of metalloids, and several elements that are so short-lived we can’t reliably categorize them as anything at all.

But of the elements on the periodic table that belong to the group specifically called “Nonmetals,” iodine is the last one we’ll have the pleasure of meeting.

That’s not to say our future entries will be boring — quite the opposite — but today, let’s appreciate one last vibrant vapor that your body simply cannot do without.

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 sail the seas in search of iodine.

In times of war, sometimes a little creativity is required to produce the goods that a country might otherwise receive through trade. Such was the case in 1811, when Napoleon’s France was at war with England.

Bernard Courtois was in the gunpowder business — a pretty good gig when the bullets are flying. The only problem was a shortage of one critical ingredient: potassium nitrate. Usually that was harvested from the ashes of firewood, but France had been so heavily deforested that there wasn’t much wood left.1 Seeing the land picked clean of all suitable plant life, Courtois turned toward the sea.

Specifically, sea weed. It did the trick: In the burnt remains of kelp, Courtois found sodium and potassium… and from what it looked like, something else, too. When he added sulfuric acid to the ashes, a puff of vivid purple gas appeared. Upon cooling, it condensed into dark and lustrous crystals.

Courtois suspected that this might be a new chemical element, but this was all a little over his head. He sent samples out to some of France’s most brilliant scientists, and they, in turn, passed the substance along to their friends and colleagues. Joseph Gay-Lussac (zho-zef louie gay-loos-ack) was the one to verify that yes, Courtois had discovered a brand new element, one that belonged to the halogen family. Inspired by chlorine, the halogen gas Humphry Davy named for its pale greenish yellow color, Gay-Lussac dubbed the element ione, from the Greek word for the violet hue of this halogen gas.

By sheer incredible coincidence, Humphry Davy was in France at the time. Remember, Davy was British, and France was using Courtois’s gunpowder to kill British soldiers. The prospect of finding any Englishman in French borders was laughable, and yet the most prominent British chemist, who probably knew more than anyone on Earth about the halogens, just so happened to be in Paris upon a Frenchman’s discovery of a new halogen gas.

And while Davy was deep in enemy territory, he was not constantly looking over his shoulder in fear for his life. He was there on the personal invitation of the Emperor himself. Napoleon wished to award Davy for his many valuable contributions to science.

This greatly appealed to Davy, so he claimed, for he hoped “through the instrumentality of men of science, to soften the asperity of national war.” Very high-minded of everyone, but actually convening this diplomatic meeting was logistically difficult and socially awkward.

For instance: Davy had coincidentally just gotten married, and his new bride also received special dispensation to cross the firing line. Lots of newlyweds honeymoon in Paris; rarely do they make passage on a ship carrying prisoners of war. Upon arrival, the welcome they received was less of a red carpet for guests of the Emperor, and more akin to the pat-down one receives at airport security. Davy was especially amused that guards saw fit to search his pockets, his clothes, and even his shoes before admitting entry.

The Davys were also accompanied on this trip by Humphry’s protege, Michael Faraday, who acted as the couple’s valet and recorded their travels. It’s through his diary that the comedy of manners continues, like when the Brit expresses disgust at the objectionable nature of French cooking:

I think it is impossible for an English person to eat the things that come out of this place except through ignorance or actual and oppressive hunger; and yet perhaps appearances may be worse than the reality, for in some cases their dishes are to the taste excellent and inviting, but then they require, whilst on the table, a dismissal of all thoughts respecting the cookery or the kitchen.”

And when Mrs. Davy went for a walk in the Tuileries (twillerie) Gardens, she quickly learned that her the hat she wore was embarrassingly out of touch with the contemporary sartorial trends that side of the Channel. She attracted such a crowd of tittering Parisiennes that she had to be escorted off the premises.

In between such awkward episodes as these, Professor Davy found time to inspect samples of ione with his traveling chemistry lab. He confirmed that this certainly was a new element, but offered one suggestion:

“The name ione has been proposed in France for this new substance,” he wrote. “The name ione, in English, would lead to confusion for its compounds would be called ionic and ionian. By terming it iodine … this confusion will be avoided, and the name will be more analogous to chlorine and fluorine.”

It could be seen as presumptuous of Davy to stroll into hostile territory and tell the French their name is bad and they should feel bad. Many French chemists did see Davy as meddlesome at first, but he won over just as many during his travels abroad. At the very least, honoring a scientist’s work even when you’re at war with his home country is a gracious gesture — the kind you might expect to engender goodwill in said scientist.

It seems that the negatives stuck out in his mind far more prominently than any positives, though. After the trip, he wrote to his mother, “England is the only country to live in, however interesting it may be to see other countries.”2

Even worse, following Napoleon’s final defeat at the Battle of Waterloo two years later, Davy wrote an impassioned letter to the UK’s Prime Minister encouraging severe punishment for the losers. Pages upon pages of the harshest indictments of the French people.

Whoever knows the french [sic] People knows that it is impossible to depend on their gratitude; & that they are not influenced by Kind-ness: irregular in their affections, capricious in their feelings, without public spirit, their ruling passions are selfishness & vanity; and by these they are kept in continued agitation.”3

It’s certainly not what you would expect from someone who enjoyed a foreign holiday collaborating with his peers.

Apparently, the Lady Davy shared in this antipathy. After he died in 1829, she donated most of his possessions to the Royal Society Of Chemistry — but withheld the medal they had received from Napoleon. She took it to Mount’s Bay on the southern coast of Cornwall and cast it into the sea. It’s still out there somewhere. Should you chance upon it, the Society is prepared to pay out a reward of £1,800.4

So much for “softening the asperity of national war.”

Iodine’s connection to the battlefield may be more a little less direct than chlorine’s or bromine’s, but it joins the other halogens in being plainly relevant to the field of medicine.

Like chlorine, iodine is useful as an antiseptic. Like fluorine, we artificially supplement our diets with iodine. But while a fluorine deficiency will lead to poor dental health, a lack of iodine can have much greater consequences.

During a particularly frustrating conversation, highway interaction, or court hearing, one person might wish to rudely impugn another’s intelligence. Some words commonly employed for this function include “moron,” “idiot,” and “imbecile.” Less commonly known is that these words rose to prominence as medical diagnoses.

In 1912, a book titled Backward And Feeble-Minded Children: Clinical Studies In The Psychology Of Defectives, laid out how these terms distinguish themselves:

Idiots.—Those so defective that the mental development never exceeds that or a normal child of about two years.
Imbeciles.—Those whose development is higher than that of an idiot, but whose intelligence does not exceed that of a normal child of about seven years.
Morons.—Those whose mental development is above that of an imbecile, but does not exceed that of a normal child of about twelve years.”5 6

A century later, the field of psychology has changed both its terminology and how much basic respect is afforded to fellow humans. Meanwhile, the vernacular has adopted these words as insults.

In the same league is the word “cretin,” which today is mostly known as a more obscure alternative to the aforementioned invectives. Yet it too has a past in medicine.

“Cretinism” is the name that was historically given to a congenital condition that causes symptoms that are both physical and mental. Often, those include impaired growth, hair loss, delayed puberty, neurological impairment, and goiter. That last one is the medical name for enlargement of the thyroid, a gland in the neck responsible for important hormonal functions. It’s one of the most characteristic and visible symptoms that can occur with this condition.7

For a long time, the only thing people really knew about this syndrome was that some places seemed more susceptible than others. For instance, in the 1800s, nearly five percent of people born in the Swiss Alps were afflicted to some degree or another.8 9 10

It was in that same century that doctors slowly started to draw connections. For instance, Jean-Baptiste Boussingault (boos-ahn-ghool) discovered in 1831 that adding a little sea salt to meals could stave off goiter, and in the 1850s, Adolphe Chatin found a correlation between prevalence of cretinism and the iodine content in local soil.11 12 13 14

Predictably and satisfyingly, supplemental iodine acted as both a cure and a prophylactic for these conditions — a solution that is both simple and inexpensive. We only need very small amounts of iodine in our diet, but that small amount is very important. Like fluorine and chlorine, supplemental iodine was cleverly deployed to as many people as possible — not via the drinking water, but by way of an ingredient that’s nearly as common: table salt.15

For the third time, a halogen was responsible for one of the most effective public health initiatives in history, and once again, that wasn’t without its share of controversy.16

Everything and anything can be made political, often in ways that are as perfectly legitimate as they are unexpected. In India, one of those surprisingly political things is salt.

In the 19th century, occupying British forces subjected the Indian people to a high tax on salt — really just one of many superfluous and excessive taxes that were a cruel insult on top of the regime’s often-brutal injury. The British enforced a monopoly on the salt trade, which absurdly meant that allowing a bowl of seawater to evaporate in the sun was a criminal act.

It was the cause of strife for several decades in India, and when the Indian independence movement gained traction in the 20th century, salt made for a natural tool of civil disobedience: It’s something everyone requires, regardless of class or religion. Alongside Mahatma Gandhi, anti-colonial activists began a non-violent march to the sea in the spring of 1930. Eighty people led the march, with thousands more joining in over the next three weeks, until more than 50,000 protesters convened in the seaside town of Dandi.17

There, Gandhi held a fistful of silt in the air and proclaimed, “With this, I am shaking the foundations of the British Empire.” He boiled it over a fire, producing salt that, according to British law, was illegal. Over the next several months, tens of thousands of Indians were beaten or arrested for that crime, including Gandhi himself.18

No changes came about as a direct response to the Salt March, but the independence movement was playing the long game. Even if they lost the battle, this galvanized Indians across social strata and brought global attention to the oppressive British Raj. It was a landmark on the road to India’s eventual independence in 1947, and hugely influential upon the American Civil Rights Movement and similar campaigns around the world. And salt, especially salt made by one’s own hands, became an enduring political symbol.19

So when many countries around the world, especially European countries, began mandating the addition of iodine to salt in the mid-twentieth century, it understandably met some resistance in the recently freed nation. Rumors even spread that rather than preventing disease, iodization would cause diseases, including tuberculosis, diabetes, and cancer. It’s reminiscent of the hullabaloo that chlorine and fluorine had met not long before.20

Turns out that people get a little uncomfortable when you add substances to their food and water. But sometimes it really is a good idea — especially if it comes from group 17 on the periodic table. (At least, most of the time. Sorry, bromine.)

What this means, of course, is that table salt makes a convenient way to showcase not just two, but three elements for your collection.

But we’ve run into this before: convenient often means “uninteresting,” and it certainly won’t do for the discerning collector. So what awaits those atom accumulators who are willing to work a little?

Iodine is still medicinally important today. It appears in several formulations on the World Health Organization’s list of essential medicines, notably as an antiseptic, an essential nutrient, and thyroid medication.21

Recent personal experience indicates that iodine solutions are not the consumer’s most commonly found antiseptic; I couldn’t find it at all on the shelves of my local drugstore.

It’s not entirely out of reach, though. Iodine can easily be found online, not only as an antiseptic, but as part of emergency preparedness kits.

In the event of a nuclear disaster, one of the greatest health threats comes from radioactive fallout. The body will absorb radioactive isotopes of elements that it normally encounters as stable, and iodine is one of them.

Iodine-127 is the element’s only stable isotope, and it’s also the only one you’re likely to encounter in your day-to-day activity. Fission reactions produce a high amount of iodine-131, which is very radioactive. Your thyroid can’t tell the difference, though, so if it’s surrounded by bountiful iodine-131, it’ll cram itself full of the stuff. It’s effectively a death sentence.

However, if you happen to have an emergency supply of iodine-127 on hand and consume it in the immediate aftermath of such a disaster, the thyroid will fill up on that, and won’t have any room to admit the nasty version.

It’s cheap and highly effective — not only in case of an intentional strike, like at Hiroshima and Nagasaki, but also in civilian accidents, like at Kyshtym and Fukushima, or in case of nearby military tests, as we saw in the central United States through the mid-twentieth century.

The CDC emphasizes that table salt, although iodized, contains nowhere near enough iodine to be helpful in this regard. So, y’know. In case the worst does occur, don’t compound the problem by chugging salt water.

Speaking of salt water, you could make like Courtois and harvest your own from seaweed. This will be especially fun for those of you who’ve been itching for another chemistry experiment.

If you’re lucky enough to live by the seaside, you may very well have kelp washing up on your shores that you can harvest for free. Fret not if you live farther inland — you only need travel as far as the grocery store. If your local big-name retailer doesn’t happen to sell seaweed, then the nearest Asian specialty store will.

Either way, you can expect less than a one percent yield, so you’ll need a generous pile of seaweed.

You’ll need to burn all that kelp down to ashes, so if you’ve gathered it on the beach, make sure to dry it out for a week or two first. From there, it’s a matter of filtering, acidifying, and distilling a slurry of the ashes.

It’s not quite as straightforward as all that, but it’s fully within reach for the home chemist. Just don’t expect anyone to give you a medal for your efforts.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To see more detailed instructions for the seaweed experiment or to read Davy’s ravings, visit episodic table dot com slash I.

I would like to thank you for being patient with the release schedule over the past few weeks. Remember to get your flu shot, folks! Even if you do contract influenza, the vaccine can help your body recover much more quickly than it would on its own. If I didn’t get my shot, I would probably still be laid up instead of recording an episode.

Next time, we’ll see that xenon is no dope.

Until then, this is T. R. Appleton, reminding you that if you’re looking for an insult that will only offend your intended target, you’re mostly limited to provocations of a scatological nature.


  1. Salavert, A., Hello, G., & Lemaire, F. (2016). Firewood of the Napoleonic Wars: The first application of archaeological charcoal analysis to a military camp in the north of France (1803–1805). Antiquity, 90(353), 1334-1347. doi:10.15184/aqy.2016.174
  2. Humphry Davy: Science And Power, p. 104. David Knight, 1998.
  3. Taken directly from the primary source, thanks to The British Academy’s archive of Davy’s letters. Fabulous resource with an inelegant UX, but I’d rather have it that way than the other way ’round. Anyway, there doesn’t seem to be a way to permanently link to a particular letter, so instead I will tell you that you can find this one by using the site’s Advanced Search, and querying by Recipient with “Liverpool.” Of the two letters, this is the one written in 1815.
  4. BBC News, Napoleon’s Medal ‘Cast Into Sea’. March 15, 2008.
  5. Backward And Feeble-Minded Children: Clinical Studies In The Psychology Of Defectives, p. 6-7. Edmund Burke Huey, 1912.
  6. Merriam-Webster, The Clinical History Of ‘Moron,’ ‘Idiot,’ And ‘Imbecile.’
  7. Best Practice & Research Clinical Endocrinology & Metabolism, Cretinism Revisited. Zu-Pei Chen and Basil S. Hetzel, 2010.
  8. RCC Perspectives, Hypothyroidism in Switzerland. Papageorgopoulou, Christina, et al., 2012.
  9. The Atlantic Monthly, Cretins And Idiots. Linus P. Brockett, 1858.
  10. International Journal Of Anthropology, Endemic Goiter And Cretinism In The Alps: Evolution Of Science And Treatments, Transformation Of The Pathology And Its Representations. Droin G., July 2005.
  11. The Journal Of Nutrition, Research On Iodine Deficiency And Goiter In The 19th And Early 20th Centuries. Michael B. Zimmermann, November 2008.
  12. Environmental Science & Technology, Iodine Nutrition: Iodine Content Of Iodized Salt In The United States. Purnendu K. Dasgupta, Yining Liu, and Jason V. Dyke, 2008.
  13. American Journal Of Public Health And The Nation’s Health, Iodine In Nutrition. William Weston, 1931.
  14. Wiley Online Library, Adolphe Chatin (1813-1901). D. Lynn Loriaux, February 12, 2016.
  15. American Journal Of Public Health, “When It Rains It Pours”: Endemic Goiter, Iodized Salt, And David Murray Cowie, MD. Howard Markel, February 1987.
  16. Nutrients, History Of U.S. Iodine Fortification And Supplementation. Angela M. Leung, Lewis E. Braverman, and Elizabeth N. Pearce, November 2012.
  17. A Force More Powerful: A Century Of Nonviolent Conflict, p. 86. Peter Ackerman and Jack Duvall, 2001.
  18. Encyclopedia Britannica, Salt March. Kenneth Pletcher, last updated June 26, 2019.
  19. Postcolonial Studies @ Emory, Gandhi’s Salt March To Dandi. Scott Graham, Spring 1998.
  20. The New York Times, Gandhi’s Spirit Hovers As India Debates Iodized Salt. Celia W. Dugger, November 2, 2000.
  21. World Health Organization Model List Of Essential Medicines, p. 18, 38-39, 42-43, 50. World Health Organization, 21st List, 2019.

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