12. Magnesium: White Light/White Heat

Magnesium makes for quite a fireworks display, whether inside your body or out.

Featured above: A nighttime water-skier holds the tow line with his teeth while waving bright magnesium flares in either hand.

Show Notes

A Book And A Soak: The Russian author Fyodor Dostoevsky liked to relax with a bath at the mineral springs of a town called Staraya Russa — coincidentally, the “minerals” in these springs happened to be high in magnesium. This lends a savory taste to the salt that you can still buy from that town today. Anyway, Dostoevsky liked the town so much that his book The Brothers Karamazov takes place in a town suspiciously similar to Staraya Russa, and he wrote much of the book while staying there.

Show Me What A Scientist Looks Like: There’s a sadly defunct website dedicated entirely to busting stereotypes of what a scientist looks like over at This Is What A Scientist Looks Like.

The stereotype of a middle-aged white man in a lab coat is one that’s ingrained early, as evidenced by seventh-grade American children who visited Fermilab. They drew their mental image of a scientist before and after the visit to see what changed. Personally, my favorite image is by Dan S., who apparently learned that scientists are still middle-aged white men, but with 100% more disappointment and boredom. But seriously, it’s pretty encouraging to see young girls writing things like, “Who knows? Maybe I can be a scientist.” (The entire collection is really worth thumbing through, a mix of kids who already had a good idea and kids who think a “normal person” apparently has the job of Atlas.)

And it’s not just limited to that class of students. Kids are increasingly drawing women as scientists, and that kind of internalization is important in encouraging kids to become excited about the sciences.

Episode Script

The English town of Epsom was having a particularly hot and dry summer in 1618, so Henry Wicker was a little surprised when his cattle refused to drink from the perfectly good pool of water he’d just found. Once he took a sip for himself, he understood: The water had an unpleasant bitter taste.

He didn’t know it, but this was because of high levels of magnesium sulfate in the groundwater. And a few hours later, Henry learned of magnesium sulfate’s other properties: It’s a quite powerful laxative.1

Apparently, this was the height of entertainment in the time before podcasts, because Epsom salt quickly became renowned far and wide for its purgative properties. A few years later, a Dutch visitor wrote,

The practice of the drinking of the water is early in the morning and from then until 8, 9, 10 o’clock. It is drunk on an empty stomach from stoneware mugs holding about one pint. Some drink ten, twelve, even fifteen or sixteen pints in one journey, but everyone as much as he can take. And one must then go for a walk, works extraordinarily excellent, with various funny results.”2

It is technically possible to ingest too much magnesium — the dose makes the poison, after all — but for the most part, side effects will primarily be evacuative in nature. The real danger comes from what magnesium can do outside of your body.

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 watching sparks fly with magnesium.

We’ve discussed a few different kinds of salts already: Table salt, lithium salts, fluoride salts, and now, Epsom salt. But we haven’t discussed exactly what they are yet. Let’s fix that now.

Some chemicals are acids: Compounds that taste sour, conduct electricity, sting the skin, and chemically speaking, contain a hydrogen ion that they want to discard. Lemon juice and vinegar are a couple examples, as you probably know.

There are other chemicals called bases. They taste bitter and feel slippery, and they’re the opposite of acids: they happily accept hydrogen ions. Soap is a weak base, bleach is a much stronger one.

When an acid and a base combine, they neutralize each other and form two products: One of them is water, and whatever else remains is called a salt.

Salts can elicit any basic taste, and they tend to be solid crystals with pretty high melting points. But you’ll need to achieve those high temperatures if you want to zap a molten salt with electricity to separate it into its constituent pieces. If this is sounding familiar, it’s for a good reason: Magnesium is yet another element that was isolated by that wizard of wires, Humphry Davy.

By this point, discovering elements via electrolysis was old hat for Davy. In addition to magnesium and sodium, he found potassium, calcium, strontium, and barium the same way. The part that seemed to give him trouble was the names. We heard about the sodium/natrium confusion last episode, and almost the exact same story played out with potassium and its alternate name, kalium, which is why potassium’s symbol is K.3

But element 12 presented a different kind of problem. It was often found in minerals alongside element 25 — so often that it took a while for people to realize they weren’t the same thing. Since that mineral was found in a part of Greece called Magnesia, both elements were interchangeably called “magnesia.”4

Davy sought to eliminate this confusion by calling element 12 “magnium.” He didn’t actually like that name at all, so maybe he’d be glad that it didn’t stick. Ultimately, of course, it wound up being called magnesium, while element 25 got the name manganese. Those are still pretty confusing names for a lot of chemistry students, but the one person you can’t blame is Humphry Davy.5

These stories about Humphry Davy might evoke images of the archetypal mad scientist: Beakers full of bubbling liquids, electrodes in hand, singing and dancing around his homemade laboratory when an experiment was successful.

A more modern image of the typical scientist might be someone clad in a sterile white lab coat and protective glasses, or perhaps a field researcher capturing specimens in a steamy jungle. But a scientist can just as easily be tightening bolts, or hammering away at a keyboard behind a computer monitor. Or even gripping the steering wheel of a car going 200 miles per hour past a roaring crowd.

After all, race car drivers need to understand and operate a highly sensitive piece of machinery on a second-by-second basis. If something goes wrong, they need to figure it out quickly, and communicate that to their crew in the pit. And in the off-season, they spend their time driving new car designs around a test track, which requires an understanding of friction, drag, momentum, and entire textbooks worth of physics knowledge.6

All this while enduring sweltering heat, intense G-forces, and a world whipping past in the blink of an eye.7 Race car drivers are athletes, no question, but they have more in common with test pilots and astronauts than they do with baseball players and golfers.8 9

While astronauts had the space race, race car drivers have, well, automotive races. NASCAR, rally, Formula One, drag, and many other types of races with enthusiastic fans. Within their various constraints, they all involve relentlessly pushing both car and driver to find ever-faster speeds.

One of the most famous among them is 24 Hours of Le Mans, the oldest active auto race in the world. Le Mans doesn’t just ask which competitor is fastest — the winner is the team that travels the farthest distance over 24 hours of straight driving. It’s all the comfort and joy of a road trip, with the bonus that you end up right where you began. Beyond raw speed, this requires a car with excellent mechanical reliability and fuel economy.

Weight is of utmost importance. So it’s pretty understandable why Mercedes would build its cars out of magnesium, which is just about the lightest structural metal there is. Some of history’s greatest drivers would be competing at Le Mans in 1955 — so the pressure was on to construct some very fine cars.

Frenchman Pierre Levegh would be one of Mercedes’ drivers in 1955, and he began the race with a good start — but that wasn’t going to last.

A couple hours in, Levegh was near the front of the pack when two cars in front of him swerved and spun out of control. At racing speed, Levegh had no chance to slow down in time. The best he could do was raise his hand to warn drivers behind him to hit their brakes.

Levegh slammed into the back of an Austin-Healy that had crashed into a wall. Its aerodynamic shape caused it to act like a ramp for Levegh’s Mercedes, sending it flying into the air… and directly into the crowd.

It was a catastrophic scene. Levegh died instantly, and the car split into at least three different pieces before careening through the grandstands. The magnesium body of the automobile burst into flames, and when a marshal tried to extinguish it with water, things only got worse.

We don’t usually think of metals as materials that burn, but that’s just what happens to magnesium when it’s heated to a high enough temperature. Combining with atmospheric oxygen, magnesium emits a bright white flame that burns at thousands of degrees Celsius.

That’s hot enough that magnesium will tear apart water molecules to continue oxidizing. So when the marshal at Le Mans poured water on the burning wreckage, it might as well have been gasoline. A shower of embers rained over the chaotic and confused crowd. The car continued burning for several hours.10

Police covered bodies and priests administered last rites, but the race went on. Spectators at other points on the 13-kilometer track didn’t even know anything had gone wrong, and the event organizers worried that prematurely ending the race would make it difficult for ambulances to arrive. Mercedes withdrew its remaining drivers from the race. Even with a victory, Mercedes wasn’t going to end the day looking very good.11

The race ended as it always did, with champagne and kisses from local girls, but with 80 dead and 180 more injured, Le Mans ’55 is still remembered as the site of the deadliest accident in motor sport history.

If something good came out of this disaster, it was an increased focus on safety in motor sports, and automobiles in general. Switzerland banned motor sports outright and Mercedes stayed out of Le Mans for thirty years, but it’s much safer track today than 63 years ago. It also helps that cars are now actually designed to protect their drivers. And their bodies certainly aren’t made of magnesium. After all, carbon fiber is much lighter.

So you might want to stay out of the junkyard while searching for a sample of magnesium for your element collection. But there are applications where magnesium’s incendiary nature is more desirable.

Blocks of pure magnesium are easy to find at camping supply stores, the idea being that shavings as kindling will help start a fire. I’m not sure how well that works, but it does mean magnesium is within close reach for the discerning collector.

In days of yore, when men wore long beards and ladies wore hoop skirts, magnesium was a key ingredient in flash powder. Photographers would pack a bulb with powdered magnesium, puff it over a flame, and the stuff would give off a brilliant light to expose the image.

Magnesium is also important for another luminiferous process: Photosynthesis. Chlorophyll is the chemical that gives leaves their characteristic green color, and helps translate the light of the sun into energy that plants can use. At the center of each molecule of chlorophyll in each leaf on every tree is a single atom of magnesium.

As much as I hope this is a learning experience for you, it is for me, too, because I’m quite surprised by the panoply of elements available in pharmaceutical form.

Maybe I’m being overly fancy about it, but centuries later, magnesium is still one of the most effective laxatives we know, often as “milk of magnesia.” I guess wherever it crops up, magnesium is determined to be a firecracker.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To see what kids think scientists look like and learn how magnesium inspired Fyodor Dostoevsky, visit episodic table dot com slash m g.

Next time, we’ll figure out just where we can shove that extra “i” in aluminium.

This is T. R. Appleton, reminding you to take a walk for various funny results.

Sources

  1. Education In Chemistry, Magnesium. John Emsley, July 1, 2008.
  2. Epsom And Ewell History Explorer, Epsom Spa.
  3. Science History Institute, Science & Celebrity: Humphry Davy’s Rising Star. T. K. Kenyon, Winter 2008-2009.
  4. Elementymology & Elements Multidict, Magnesium. Peter van der Krogt.
  5. Chemical Nomenclature, pp. 46-47. K. J. Thurlowe, 1998.
  6. Further resources on the physics of race car driving are available at the Allen Berg Racing Schools website and The Science Classroom wiki.
  7. Los Angeles Times, Driving a Race Car Takes Strength and Stamina : These Athletes Travel in Fast Lane but Keep Fit. Associated Press, May 19, 1985
  8. And at one point, NASA considered race car drivers as potential astronauts. See here for more on how they did choose the guys with the right stuff.
  9. Apparently, the thought occurred to the Virginia Air & Space Museum, as well.
  10. Mike Hawthorn & the 1955 24 Hours of Le Mans: The Cause and the Effect, Jeremy McMullen. Normally I wouldn’t link to a source like “concept carz dot com,” but Mr. McMullen does cite his primary sources. I mark it as trustworthy!
  11. Jalopnik, Just How Horrifying Was The Worst Crash In Motorsports, Le Mans ’55? Raphael Orlove, June 14, 2014.

5 Replies to “12. Magnesium: White Light/White Heat”

  1. While the pics that kids grew were interesting for their gender changes, I note the kids thought scientists were somehow exclusively lily white, both before and after.

Leave a Reply

Your email address will not be published. Required fields are marked *