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  • Hey, Vsauce. Michael here.

  • And I'm in Anaheim at VidCon. I hope to see some of you here, because I

  • like you guys. But I can't marry all of you.

  • But if I did put a ring on it, what is the most precious thing you could make that ring

  • out of? Silver, gold, platinum.

  • Those are all fine, but I wanna know what is the rarest, most scarce thing on Earth

  • that's stable and safe to wear I could make that ring out of.

  • And I want it to be pure. I'm talking elemental.

  • Well, luckily, I recently went to the University of Nottingham, home of Periodic Videos and

  • experimented with some elements. First things first, zinc dissolved in mercury.

  • This stuff is awesome, it's dense, it's heavy, it's liquid metal.

  • It's cool, but even cooler is human urine. Thank you Neil.

  • Of course I am just kidding. This is an aqueous solution of the metal vanadium.

  • And when we mix vanadium in with the mercury and the zinc, the mercury helps the zinc give

  • electrons to the vanadium. And is it gains more and more electrons, it

  • changes colour. We're looking for purple.

  • I love shaking this, it's crazy, it's like throwing me off balance.

  • It's so heavy. Look at that.

  • Thank you electrons.

  • Those colours were beautiful, but vanadium

  • is not that rare. I wanna get something more precious.

  • And how about precious personally, like my dad?

  • He's a chemical engineer who specifically works with and has a patent concerning one

  • element. Sulphur.

  • Of course a fun thing to do with sulphur is to make it bark like a dog.

  • Here's what we're gonna do. We're gonna take a glass tube and fill it

  • with laughing gas, nitrous oxide. We're gonna pour a little bit of water into

  • the tube to cushion and protect the tube and then we're gonna pour in some liquid carbon

  • disulphide. It's very volatile and will evaporate, giving

  • us a mixture of gases inside this tube. Finally, I will light the top of the tube,

  • causing the carbon disulphide to burn. And as it burns, the temperature and pressure

  • in the tube will increase, causing the reaction to go faster and faster.

  • It'll accelerate and bark.

  • Wow.

  • And look at all the sulphur on the sides of the tube.

  • That reaction was fun and cool and colourful, but we're way off track here.

  • Even though sulphur is precious and dear to my heart, it's not that rare at all.

  • So let's get crazy and talk about astatine. Astatine is so rare here on Earth that we

  • don't even know what it looks like. If you were to try to get enough astatine

  • atoms together that you could see it with your own eyes, it would instantly vaporise

  • itself because of its radioactive heat. The fact that it's so radioactive means it

  • wouldn't be great as a ring, so let's move on to something a little bit more standard

  • and see where it takes us. Gold.

  • Gold, of course, is famous for its un-reactivity, which is why it's a great way to store your

  • wealth. If you have a lot of gold laying around, the

  • likelihood that it will combine with other elements and dissolve or rust or corrode is

  • basically zero, with the exception of some special solutions.

  • In particular, one discovered in 1300s with the fancy name "aqua regia."

  • It's made out of hydrochloric acid and nitric acid and we're about to make some right now

  • thanks to Neil from Periodic Videos. Of course, we're using this fume cover, because

  • the fumes that come off the nitric acid are quite dangerous.

  • It's the gas NO2 and if you inhale it, nitric acid forms in your lungs.

  • So instead of doing that, let's put some gold in aqua regia.

  • We're just gonna use this ancient priceless Egyptian relic.

  • Let's go ahead and try this out. As the gold dissolves, what we wind up with

  • in the evaporating dish is chloroauric acid. Auric coming from aurum, the Latin word for

  • gold, which is why gold's symbol on the periodic table is Au.

  • It's really sad to watch that gold dissolve away.

  • I wish there was a way for us to just make other things into gold.

  • Now I know what you're thinking. "Michael, that's alchemy."

  • But alchemy is quite real. In today's particle accelerators we can smash

  • particles together, creating elements. At the accelerator collider at GSI they can

  • create gold by smashing particles together at a rate of 2 million gold atoms every second.

  • That's pretty cool, right? Well, as you know, atoms are incredibly small.

  • They're so small that even though GSI can make 2 million new gold atoms every single

  • second, were they to leave the machine on at that rate for 50 million years they would

  • only produce 1 gram of gold. Gold is rare and precious and expensive.

  • But gold is 40% more common than iridium. And iridium is incredibly resilient.

  • It doesn't dissolve in aqua regia and it's not even attacked by molten metals or silicates

  • at high temperature, which is nice and ..., but not as pretty as cerium, which reacts at high

  • temperature to form beautiful little sparkles. As we continue our journey to discover the

  • rarest thing to make a ring out of, we've got to discuss osmium.

  • This stuff is so rare there's fewer than one part per billion in our Earth's crust.

  • But we're not done yet. Iridium and osmium are both in the platinum

  • family. And if you take a look at platinum, it's much

  • more common than both iridium and osmium, but there's something neat that I think we

  • should consider. Stable isotopes.

  • And it's one of the isotopes of platinum that will finish our story.

  • Platinum-190. It's a stable isotope with half-life of over

  • billion years that's non-reactive. It's fits all our criteria.

  • A ring made of the scarcest, naturally occurring stable, non-reactive thing.

  • So hey, it would be an awesome ring. Now, you're probably wondering, "Michael,

  • why did you experiment with vanadium, sulphur, gold and cerium?"

  • Well, here's what's interesting. Take a look at the periodic table and there's

  • symbols. Ta-da!

  • Vsauce.

  • And as always,

  • thanks for watching.

Hey, Vsauce. Michael here.

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SCIENCE!最も希少な貴金属とは? (SCIENCE! What is the Rarest Precious Metal?)

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    BH に公開 2021 年 01 月 14 日
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