78. Platinum: A Tous Les Temps, A Tous Les Peuples

Sometimes, being set in stone isn’t permanent enough.

Featured above: Stephan Schlamminger’s excellent tattoo honoring his work redefining kilogram.

Show Notes

What else is new? I’m late to the show notes. In the meantime, to learn a little bit about Jean Baptiste Joseph Delambre and Pierre Méchain, I’ll let SciShow be my substitute teacher:

But those two really deserve more mention, so even if I don’t get to do a full writeup of show notes, I’ll be sure to cover a little more of their story. This might actually have to wait a while before I get to it, I’m afraid!

Episode Script

Platinum is an expensive, shiny, durable metal, yet there are not very many coins made of platinum. It has rarely been used as currency, and even then, only for very brief periods of time. Every now and then, a commemorative coin will be minted in platinum, but that’s about it. Basically, if you’re holding a platinum coin, you know you’ve got something special on your hands.

You might even have a coin worth one trillion dollars.

That might sound far-fetched, but it’s actually a real thing. Well, it’s a real idea for a thing, at least.

The plan was first concocted in 2011 as a way for the United States government to deal with its national debt. The country needed money, you see, and had already borrowed the maximum amount it was allowed. Usually, Congress just rubber-stamps a deal to allow the country to borrow more money, but the legislature was feeling especially prickly at the time.1

So what’s a penniless power to do? The treasury isn’t allowed to just print up more money to cover their bills. There are rules against that kind of thing. Except… a blogger called “beowulf” noticed something peculiar.

31 US Code § 5112 – Denominations, specifications, and design of coins

(k)The Secretary may mint and issue platinum bullion coins and proof platinum coins in accordance with such specifications, designs, varieties, quantities, denominations, and inscriptions as the Secretary, in the Secretary’s discretion, may prescribe from time to time.2

Did you catch that? The Secretary of the Treasury can issue a coin that’s worth any arbitrary amount of money — as long as it’s made of platinum. This is supposed to be used just for coins that honor a special occasion, like the fiftieth anniversary of the moon landing or something. But technically, there’s nothing stopping the Treasury from minting a very special coin made of platinum, depositing it in the Federal Reserve, and dusting their hands off for a job well done and a country saved from debt crisis.

This has never actually happened. In 2011, Congress passed the Budget Control Act to avert that particular crisis. The idea resurfaces from time to time, though — there’s no shortage of fiscal emergencies in Late Capitalism, including COVID-19-related financial relief. So who knows? Maybe the trillion-dollar coin will become a reality sooner or later.3 4

For now, though, there does exist one big hunk of platinum that commemorates something special and priceless.

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’re gauging platinum.

Platinum is one of those strange elements, like molybdenum, that’s actually named for another element. When 17th-century Spanish invaders found the metal in South America, it primarily took the form of little grey beads while panning for gold. They called these beads “platina,” meaning “little silver.”5

But the Spanish didn’t discover platinum. There were already lots of people living in South America, and they had known about the metal for centuries. While the Spanish couldn’t figure out any way to work with it or even melt it, indigenous crafters made masks, jewelry, figurines, and even fish hooks and tweezers out of platinum.6

It is really a pain to work with, though. It’s hard to melt, it’s not very malleable, and it’s also pretty heavy. These enduring qualities are part of the reason platinum was chosen as the material for the International Prototype Kilogram.

Historically, weights and measures have been a mess. One common early unit was the cubit, defined as the length from the elbow to the tip of the middle finger. Weight was frequently defined in grains, as in grains of wheat. A denarius was seventy and a half grains, with six denarii to an ounce and twelve ounces to a pound.7

Obviously there’s nothing keeping one grain of wheat from weighing as much as another, and no two people are going to have arms of identical length.8 And just forget about converting between different units. Even worse, the whole system could be entirely different in the next town over. By the Middle Ages, Europe’s measures were probably the biggest mess in the world, a hodgepodge of various systems inherited from the Greeks, Egyptians, and Babylonians, with elements from Celtic, Scandinavian, and Arabic customs, with a dash of local flavor for any given county.

To introduce something more reasonable would take nothing short of a revolution. The French Revolution, in particular.

France was a tumultuous place in the late 18th century, to put it very mildly. Widespread inequality, unemployment, food shortages, runaway debt, and steep inflation had pushed society to its breaking point. Weights and measures were so intertwined with these problems that introducing something more logical and consistent was critical for liberté, égalité, fraternité.9

Philosopher and mathematician Nicolas de Condorcet proposed a system that would be “for all times, for all people.”10 An abstract and logical system, not something based on custom, authority, or human anatomy. Units were to be based on powers of ten, allowing for easy conversion among them. The new base unit of length, the meter, would be calculated as one ten-millionth the distance between the North Pole and the Equator. Volume would be defined in liters, with one liter being a cubic decimeter. And the unit of mass known as the kilogram would be equal to one liter of pure water.

That’s a nice idea, at least, but that actually turns out to be rather difficult to measure with high precision. For the sake of reference, standards were created. A platinum bar exactly one meter long and a platinum cylinder exactly one kilogram in mass were created with the greatest possible precision and stored in the National Archives of France. Copies were carefully created and distributed worldwide, and they remained absolutely constant for ninety years. In 1889, they were swapped out for slightly refined versions made of a platinum-iridium alloy, but for all intents and purposes, these relics were sacrosanct, contained within a climate-controlled, vacuum-sealed container, in a vault sealed by three separate keys held by three different people. This metal cylinder is as close to its platonic ideal as a thing can get. The official copies ultimately governed the accuracy of every metric scale in the world, from NASA’s Jet Propulsion Laboratory to your neighborhood supermarket.

But it turns out that absolutely nothing is as perfect in practice as it seems in theory. In 1989, on one of the rare occasions that Le Grand K was taken out of its chamber for assessment, scientists discovered something disquieting. The Ur-Kilogram was approximately 50 micrograms lighter than its official copies. Had the copies become heavier, or had the original somehow become lighter? It’s impossible to say, but either way, the definition of the kilogram had technically changed.

Thankfully, our understanding of the universe has grown over the past few centuries, and we’ve found some natural phenomena that appear to be constant, no matter where or when you are. The speed of light in a vacuum is one such example, being exactly 299,792,458 meters per second. (Except, actually, it’s more accurate to say that one meter is the distance light in a vacuum travels in one 299,792,458th of a second… but let’s not go down that particular rabbit hole right now.)11

Another of these is Planck’s constant, which is the absolute smallest amount by which a photon’s energy can increase or decrease, measured in Joule-seconds. Admittedly, this unit is a little harder to grok than the meter, but what’s important is to know that this is a unit of energy. Conveniently, we know that the mass of a particle is equal to its energy divided by the speed of light to the second power — you might have heard it as E = mc2.

By performing a little tricky math, it’s possible to express the mass of an object in terms of joule-seconds, and in so doing, tie the definition of the kilogram to Planck’s constant, making it consistent everywhere, everywhen.12 13

In order to perform this calculation with a satisfying degree of accuracy, scientists needed to measure Planck’s constant with greater precision than had ever been done before. When they first realized the problem with the platinum kilogram, no instruments existed that could perform such fine measurements.

The right tool for the job is called the Kibble balance, named after its inventor, Bryan Kibble. While a mechanical scale compares one mass against another one, the Kibble balance measures a physical mass against electromagnetic force. Kibble created the first of these scales in 1975, but it wasn’t until 2018 — two years after his death — that the technology was refined enough for this particular use, and scientists from 60 nations voted unanimously to redefine the kilogram in terms of Planck’s constant.14 15 16 17

The following May 20, World Metrology Day, that decision was enacted. The Kibble Machines were turned on, and Planck’s constant was measured more meticulously than ever before.18

The professionals exhibited a wide range of reactions. Dr. Martin Milton, Director of the International Bureau of Weights and Measures, demonstrated the kind of cool-headed impassivity you might expect from the person in that role. “Am I emotional about this? No, not really,” he said. Stephen Schlamminger, one of the scientists who performed the work, was agog. “I’m in disbelief, personally,” said he. “…[T]here’s something in my life I’ve actually finished. You start a lot of things in life, but really, how many do you get to finish?”19

To commemorate the occasion, he and a few colleagues got forearm tattoos bearing the new measurement: h = 6.626 070 15 × 10-34 Js. Underneath, it reads, A tous les temps, a tous les peoples: For all times, for all people.20

Platinum may no longer be enshrined as the definitive kilogram, but it has been used by many peoples across all times. As far back as 1200 BCE, the Egyptians were using it to make jewelry and other decorative items, although they might not have been aware of it. It’s likely that they thought they were just working with some low-grade silver.

That’s not such a big deal. Sure, it’s a pain to work with, but at least you still wind up with something shiny and beautiful. When Georgi Markov unintentionally acquired a little platinum, he wound up dead.

Born in 1929, Markov was a popular Bulgarian writer and an outspoken critic of his country’s government. That brought him a fair bit of trouble, like the time he was at a dinner party in Munich and somebody poisoned him. Luckily for him, he survived. Or the time he was on vacation in Sardinia, and somebody poisoned him. Luckily for him, he survived.21

He eventually moved to London for safety’s sake, but he continued to write plays and worked for the BBC, Deutsche Welle, and Radio Free Europe. In 1978, he was crossing the Waterloo Bridge over the Thames when he felt a sharp jab in his leg. A passer-by fumbling with his umbrella muttered a hurried apology with an Eastern European accent and shuffled off. That evening, Markov fell gravely ill and was rushed to St. James’ Hospital. Four days later, he died.22 23

During the autopsy, doctors found a tiny pellet buried deep in his leg, the same place where he had earlier felt that sharp pain. It wasn’t even two millimeters wide, and hadn’t shown up on x-rays. It was made of 10% iridium and 90% platinum — metals that are notable for their biological inertness. A human body has basically no reaction to them.

Clearly, the minuscule bullet didn’t kill Markov. It was ricin, the extremely potent toxin inside the bullet, that killed him.

Two little holes drilled into the pellet held the poison, and it was sealed inside with a special wax designed to melt at body temperature. Newspapers reported that the umbrella wielded by the shady figure on the bridge was actually the gun that fired the bullet, a real-life case of James Bond-caliber techno-intrigue. That may be true, or perhaps the assassin merely used the umbrella to hide his face. It wouldn’t be unheard of, though. The history of espionage is littered with suspicious deaths and creative weaponry. A German man was murdered under very similar circumstances in 2012.

Whether the bullet was actually delivered via bumbershoot or some other device, platinum was critical to the weapon’s design. A bullet made of lead or some other lesser metal could possibly deform upon firing, sealing the poison inside and causing Georgi Markov to survive a third assassination attempt.

These kinds of circumstances, of course, are highly unusual. Rarely is element 78 found in such unsavory company, and you should have no trouble finding it in all the same places as other platinum-group metals: spark plugs, catalytic converters, and yes, pen nibs, as well as special lab equipment for working with especially volatile chemicals.24

Or you could expand your numismatic sub-collection of the elements. For a few short years in the 19th century, Russia minted rubles of pure platinum, and the US Treasury does strike some commemorative coins out of platinum every year. Any of these would be a very valuable addition to your collection — maybe not a trillion dollars, but valuable nonetheless.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To learn about the difficult task of measuring the distance between the Equator and North Pole, visit episodic table dot com slash P t.

Next time, we’ll go for the gold.

Until then, this is T. R. Appleton, reminding you that the clocks changed! We’ve all spent the past year locked indoors and yet they still had the gall to rob us of one precious hour over the weekend. I woke up yesterday feeling very confused and then very upset. Anyway, happy spring.


  1. Slate, Mint The Coin. Matthew Yglesias, Last updated September 27, 2013.
  2. Cornell Law School Legal Information Institute, 31 US Code § 5112.
  3. The Wall Street Journal, Treasury Won’t Mint Platinum Coin To Avoid Debt Ceiling. Eric Morath and David Wessel, last updated January 12, 2013.
  4. Fortune, How Does America Pay For A $2 Trillion Coronavirus Relief Bill? With Two Shiny Coins, This Lawmaker Argues. Robert Hackett, March 25, 2020.
  5. Elementymology And Elements Multidict, Platinum. Peter van der Krogt.
  6. Platinum Metals Review, Ancient Platinum Technology In South America: Its Use By Indians In Pre-Hispanic Times. David A. Scott, 1980.
  7. Encyclopedia Britannica, Cubit. Last updated March 6, 2016.
  8. Biology Letters, Seed Size Variability: From Carob To Carats. Lindsay A. Turnbull, Luis Santamaría, Toni Martorell, and Joan Rallo, October 2006.
  9. Encyclopedia Britannica, Metric System. Last updated November 19, 2018.
  10. The Glasgow Insight Into Science And Technology, The History Of The Metric System: From The French Revolution To The SI. Gavin Kirby, May 29, 2014.
  11. BIPM, The International System Of Units (SI). Ninth edition, 2019.
  12. Encyclopedia Britannica, Kilogram. Last updated November 19, 2018.
  13. Phys.org, The Kilogram Is Being Redefined — A Physicist Explains. Kevin Pimbblet, November 15, 2018.
  14. CNN, The World Has Just Redefined The Kilogram. Matthew Robinson and Lianne Kolirin, November 16, 2018.
  15. GBH News, Say Au Revoir To That Hunk Of Metal In France That Has Redefined The Kilogram. Nell Greenfieldboyce, November 13, 2018.
  16. CERN, Lock The Planck: The Kilogram Has A New Definition. Achintya Rao, May 20, 2019.
  17. NIST, Kilogram: Mass And Planck’s Constant.
  18. Vox, The New Kilogram Just Debuted. It’s A Massive Achievement. Brian Resnick, May 20, 2019.
  19. The Verge, The Kilogram Is Dead; Long Live The Kilogram. James Vincent, November 13, 2018.
  20. YouTube, Scientists Just Redefined The Kilogram. VICE News, May 21, 2019.
  21. YouTube, Georgi Markov. U.S. Agency For Global Media, September 14, 2020.
  22. The Guardian, The Poison-Tipped Umbrella: The Death Of Georgi Markov In 1978 — Archive. Lindsay Mackie and John Andrews, September 12, 1978.
  23. BBC News, The BBC Journalist Assassinated With A Poison-Tipped Umbrella. September 20, 2016.
  24. Nature, Behind Platinum’s Sparkle. Vivian W. W. Yam, September 2010.

4 Replies to “78. Platinum: A Tous Les Temps, A Tous Les Peuples”

  1. I knew the Kilogram was based on a platinum-iridium cylinder until very recently, but that the meter used to have a man-made standard is news to me…

    It did get me thinking about rods that are a meter in length with a mass of 1 kilogram, and if I did my math right, a Platinum rod of that length and mass would be about 3.85 mm in radius… I devided 1000 grams by the density of platinum to get the volume, then divided by 100pi and took t he square root.

    A 1 kilogram rod 1 meter in length with a radius of 1 centimeter would also have a density of 10/pi or ~3.18 g/cm^3… Best I can tell, a Titanium-Aluminium alloy might be the best option for making such a rod from metal… atleast, I’m assuming alloys tend to have densities intermediate between the pure metals and I don’t know of any other light metals that are safe to handle and relatively non-reactive.

    1. Somehow, I spent two weeks researching and writing about artifacts of the metric system, and this never occurred to me. Now I must somehow acquire a one-meter long rod that weighs precisely one kilogram. If it also had a radius of one centimeter, that would be perfect. Guess I’m off to find a machine shop!!

      You know that subreddit, /r/oddlysatisfying? I think that object would take top post for at least a day.

      1. I don’t do Reddit, so no, I don’t know it… And while my math is based on the rod being a right circular cylinder with sharp edges, I’m not sure if I would prefer that shape for such a rod, or if I’d prefer a hemi-spherical cap on each end.. Either way, such a rod would certainly be an appropriate staff of office for a Minister Of Measures.

        Now, what would be an appropriate mass and radius to pair with a length of 1 light nanosecond… After some trial and error, I think silica might be a good candidate for making a rod with such a length that contains 1 mole of it’s constituent, having a molar volume of about 22 cm^3/mol… for metals, titanium barely broke 10 cm^3/mol and most others I tired are even smaller.

        I also gave thought to a literal pound-foot(e.g. a rod 1 foot long and weighing one pound), but pounds are force, not mass, and it turns out a slug is about 14 kilograms, so a foot long slug would probably need something denser than Osmium to keep the radius to something that would fit in the hand…and I’m not sure SI prefixes go high enough to put aname to multiples of the Planck length and mass in reasonable territory.

  2. Noticed an error on the episode archive page: the link to platinum actually takes you to the iridium episode.

    (Listened through each episode, by the way! Fascinating stuff and learned a lot about history.)

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