Materials Advent 2018 Parts 9, 10, and 11 – Weird Glasses

A teardropped shaped piece of glass seems to have an iridescent sheen
A photo of a Prince Rupert’s drop taken with a special polarizer that helps reveals stresses in the material

Following up on yesterday, I thought it would be fun to look at some weirder glasses.

Prince Rupert’s drops are teardrop (or tadpole) shaped pieces of glass made by dropping molten glass into cold water. They are famous for their bizarre strength. You can pound on the head all you want, and it will almost never break, but nick the tail a little bit and it spectacularly explodes.

Poof

This turns out to come from the way the drop forms. That initial bit that hits the water cools so fast it actually gets compressed by the cooling, making it stronger, but the tail is basically a path to the weak core. The trippy oil-puddle-esque image above is taken with a special kind of set-up that looks at light that ends up being polarized by stresses within the glass. Prince Rupert’s drops turn out to be technologically important, because efforts to understand them since the 1600s have inspired research into ways to make other kinds of glass stronger, leading to the Gorilla Glass and other toughened glass that now lines our smartphones and many other displays.

Metallic glasses are just what they sound like. Just like how I mentioned yesterday that metals are usually crystals, it turns out we can also try making them into glasses by cooling them so quickly their atoms can’t form an ordered structure. This requires either incredibly fast cooling (on the scale of at least 1000 degrees a second for some compositions) or an interesting work around using a lot of different metals together. It turns out that mixing a bunch of atoms of different sizes makes it harder for them to pack into a neat pattern.

The mix of atoms in metallic glasses helps them stay disordered.
A microscopy image showing the real atoms in a glassy alloy of unspecified composition. From Physical Metallurgy (Fifth Edition)

You might wonder why we want to make glass out of metals. It turns out to provide a special property – bounciness. And we literally demonstrate that with “atomic trampolines”. It’s really easy to deform a crystalline metal because that orderly crystal structure makes it easy to slide rows of atoms past each other when you hit them hard enough, just like it’s easy to push a row of desks lined up in a classroom. The glass can’t deform – there’s no preferred direction to push the atoms, so instead the energy just goes back to whatever it hits. This has a cost though – if you hit it too hard, just like regular glass, a metallic glass just shatters instead of accepting a dent. There was initially a lot of hope for them as new materials for the shells of devices like smartphones since they don’t transmit that energy to the components inside, but that’s proved harder to make than hoped. However, you can buy a golf club that takes advantage of the bounciness to essentially transmit all the energy from your swing into the ball. (Going farther back, they evidently also form the basis of most of those theft prevention tags that ring alarms.)

Finally, I’m breaking my rule a bit with this last one by not having an image, but did you know that toffee is also a glass? (Sorry, no one has put toffee under a high-resolution microscope or run it under an X-ray source for weird images for me yet) Or at least good toffee is. That crisp crunch you get from well-made toffee is because of glass shattering. When toffee feels gritty, it is because it has actually started to crystallize and typically has hundreds of little mini-crystals that want to deform. This is why some recipes suggest adding corn syrup. The bigger sugar molecules in corn syrup mixed up with the sucrose in regular table sugar mix up in a way like the metallic glasses above and make it harder for them to set into their crystal structure. Similarly, an early kind of stunt glass for special effects was literally made by boiling sugar into a clear candy.

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Red Eye Take Warning – Our Strange, Cyclical Awareness of Pee in Pools

The news has been abuzz lately with a terrifying revelation: if you get red eye at the the pool, it’s not from the chlorine, it’s from urine. Or to put it more accurately, from the product of chlorine reacting with a chemical in the urine. In the water, chlorine easily reacts with uric acid, a chemical found in urine, and also in sweat, to form chloramines. It’s not surprising that this caught a lot of peoples’ eyes, especially since those product chemicals are linked to more than just eye irritation. But what’s really weird is what spurred this all on. It’s not a new study that finally proved this. It’s just the release of the CDC’s annual safe swimming guide and a survey from the National Swimming Pool Foundation. But this isn’t the first year the CDC mentioned this fact: an infographic from 2014’s Recreational Water Illness and Injury Prevention Week does and two different posters from 2013 do (the posters have had some slight tweaks, but the Internet Archive confirms they were there in 2013 and even 2012), and on a slightly related note, a poster from 2010 says that urine in the pool uses up the chlorine.

A young smiling boy is at the edge of a swimming pool, with goggles on his forehead.

My neighborhood swim coach probably could have convinced me to wear goggles a lot earlier if she told me it would have kept pee out of my eyes.

Here’s what I find even stranger. Last year there was a lot of publicity about a study suggesting the products of the chlorine-uric acid reaction might be linked to more severe harm than just red eye. But neither Bletchley, the leader of study, and none of the articles about it link the chemicals to red eye at all, or even mention urine’s role in red eye in the pool. Also, if you’re curious about the harm, but don’t want to read the articles, the conclusion is that it doesn’t even reach the dangerous limits for drinking water. According to The Atlantic, Bletchley is worried more that it might be easier for an event like a swimming competition to easily deplete the chlorine available for disinfecting a pool in only a short amount of time. This seems strange because it seems like a great time to bring up that eye irritation can be a decent personal marker for the quality of the pool as a way to empower people. If you’re at a pool and your eyes feel like they’re on fire or you’re hacking a lot without swallowing water, maybe that’s a good sign to tell the lifeguard they need to add more chlorine because most of it has probably formed chloramines by then.

Discussion of urine and red eye seems to phase in and out over time, and actually even the focus of whether its sweat or urine does too. In 2013, the same person from the CDC spoke with LiveScience and they mention that the pool smell and red eye is mainly caused by chloramines (and therefore urine and sweat), not chlorine. A piece from 2012 reacting to a radio host goes into detail on chloramines. During the 2012 Olympics, Huffington Post discussed the irritating effects of chloramines on your body, including red eye, and the depletion of chlorine for sterilization after many Olympic swimmers admitted to peeing in the pool. (Other pieces seem to ignore that this reaction happens and assume it’s fine since urine itself doesn’t have any compounds or microbes that would cause disease.) In 2009, CNN mentions that the chloramines cause both red eye and some respiratory irritation. The article is from around Memorial Day, suggesting it was just a typical awareness piece. Oh, and they also refer to a 2008 interview with Michael Phelps admitting that Olympians pee in the pool. The CDC also mentions chloramines as potential asthma triggers in poorly maintained and ventilated pools and as eye irritants in a web page and review study that year. In 2008, the same Purdue group published what seems like the first study to analyze these byproducts, because others had only looked at inorganic molecules. There the health concern is mainly about respiratory problems caused by poor indoor pool maintenance because these chemicals can start to build up. Nothing about red eye is mentioned there. In 2006, someone on the Straight Dope discussion boards refers to a recent local news article attributing red eye in the pool to chlorine bonding with pee or sweat. They ask whether or not that’s true. Someone on the board claims it’s actually because chlorine in the pool forms a small amount of hydrochloric acid that will always irritate your eyes. A later commenter links to a piece by Water Quality and Health Council pinning chloramine as the culprit. An article from the Australian Broadcasting Corporation talks about how nitrogen from urine and sweat is responsible for that “chlorine smell” at pools, but doesn’t mention it causing irritation or just using up chlorine that could go to sterilizing the pool.

Finally, I just decided to look up the earliest mention possible by restricting Google searches to earlier dates. Here is an article from the Chicago Tribune in 1996.

There is no smell when chlorine is added to a clean pool. The smell comes as the chlorine attacks all the waste in the pool. (That garbage is known as “organic load” to pool experts.) So some chlorine is in the water just waiting for dirt to come by. Other chlorine is busy attaching to that dirt, making something called combined chlorine. “It’s the combined chlorine that burns a kid’s eyes and all that fun stuff,” says chemist Dave Kierzkowski of Laporte Water Technology and Biochem, a Milwaukee company that makes pool chemicals.

We’ve known about this for nearly 20 years! We just seem to forget. Often. I realize part of this is the seasonal nature of swimming, and so most news outlets will do a piece on being safe at pools every year. But even then, it seems like every few years people are surprised that it is not chlorine that stings your eyes, but the product of its reaction with waste in the water. I’m curious if I can find older things from LexisNexis or journal searches I can do at school. (Google results for sites older than 1996 don’t make much sense, because it seems like the crawler is picking up more recent related stories that happen to show up as suggestions on older pages.) Also, I’m just curious about the distinction between Bletchley’s tests and pool supplies that measure “combined chlorine” and chloramine, which is discussed in this 2001 article as causing red eye. I imagine his is more precise, but Bletchley also says people don’t measure it, and I wonder why.

Real Stars Break Down Alcohol Through Quantum Mechanics, Not Their Liver

When most people think of astronomy, they think of physics. Many astronomers are technically astrophysicists, and even if that’s not their title, most have a physics background. (If you’re really in the know, you might know that planetary science is a distinct field that draws a lot on geology as well as astronomy.)  But another aspect of space science that’s grown a lot over the last decade or so is astrochemistry. Astronomers have been able to study chemical compounds in celestial bodies since the the middle of the 20th century, when radio telescopes could detect spectral emissions unique to certain molecules (both nearby and across the galaxy) and even more so when space probes could directly analyze celestial bodies in our solar system. But there’s also a lot of chemicals just out in the middle of space, and the list keeps getting longer and includes increasingly more complicated compounds. Astrochemistry looks at these chemicals and tries to understand how they could form in astronomical environments.

One of the bigger puzzles for astrochemists has been understanding how alcohols are formed and destroyed in space. Space is too cold for methanol to break up into the highly reactive methoxy radical in a way similar to most reactions on Earth. While UV radiation exciting molecules enough to break them apart can explain how some chemicals are formed (and why UV light gives you cancer), lab tests couldn’t detect methoxy after exposing methanol to UV radiation. Dust wasn’t even acting as a catalyst. It actually turns out the reaction works best when the methanol is in its gaseous form at low temperatures because those conditions are optimal for quantum tunneling.

The procession of a chemical reaction in normal, bulk circumstances (on the left) and via quantum tunneling (on the right). From Richard Helmich.

Tunnelingis a phenomenon that only occurs in quantum mechanics. There’s really no good analogy in the classical physics we’re most familiar with. To very quickly sum up, if an electron is in place A and can also be in place C, but A and C are separated by a region B where it shouldn’t be able to travel, it can sometimes still end up in C by tunneling through B. This is also generalized to more than just physical space. Tunneling means particles can do things they shouldn’t have the energy for, like the reaction picture above. Quantum mechanics just says that it won’t happen very often and it can take some time. This is where the low temperature comes in. As we’ve talked about before, temperature reflects molecular motion. At the low temperatures of open space, the methanol and hydroxide are moving relatively slowly. When they bump into each other, this means they won’t bounce off immediately, and in that longer frame of time, an electron is more likely to jump from the methanol to the hydroxide. It turns out this tunneling reaction is really efficient at lower temperatures: lab experiments showed methanol reacted 50 times faster at -210 degrees Celsius than at room temperature. The researchers are also confident that quantum tunneling can explain many other reactions in space.

What do Einstein and Elvis Have In Common?

  Aside from fantastic hair and piercing eyes?

They can both help diagnose dementia.

Recognizing famous pop culture figures can be used as a measure of several mental tasks, like the ability to recognize faces (which can be a really complicated process, resulting in the common phenomenon of seeing faces in random objects called pareidolia) and how easily a person can name things. One problem that the researchers came across when evaluating people was how old the original face test was. A person in their 70s or 60s may know what Emperor Hirohito looked like, but could you expect that of a 40-year-old coming in to see if they had early-onset dementia? So the team at Northwestern decided to modernize the sample. Einstein made the cut to stay, since his mug can still be found everywhere in our culture. But now we have Oprah instead of Martha Mitchell (the wife of Nixon’s attorney general, evidently).

Wine Tasting 101

NPR’s blog about food and science, The Salt, has an amusing story on wine tasting this week. Part of it is pointing out the actual science in wine tasting, which has recently been a victim of fights on the Internet*. Basically, The Salt’s post focuses on the actual chemicals present in wines and wants to help wine newbies detect by saying where we can find them in other foods. So here’s the quick lowdown

  • Whites aren’t aged in oak as often as reds.
  • Wine aged in American oak picks up more vanillin from the word than wines aged in French oak. Evidently American oaks have a higher concentration of the lactones than the French oaks. (I can’t find an explanation why, but that’s interesting) Vanillin, of course, is the primary chemical responsible for the flavor of vanilla.
  • Cabernet sauvignon and green peppers have the same chemical responsible for their smell. In cabernet, it’s strongest when the grapes aren’t ripe, so smelling green pepper would suggest a low quality wine. Aside: I definitely did not know that. I actually thought it wasn’t bad to have the green pepper scent. I also almost never drink cabernet, so maybe nothing should surprise me.
  • Diacetyl, a chemical commonly used in artificial butter flavorings (but also present in actual butter, potential chemophobes), develops in wines that have undergone a further fermentation process that converts the more sour malic acid (found in green apples) to lactic acid (found in milk).

NPR talks about sniffing all the foods with the same chemicals so you can “follow your nose”, if you will.

We went there.

They even suggest putting the good things in a cheap wine and comparing it’s smell to a more expensive one so you can find the similarities. But maybe I’m just taking the wrong lesson from this article, because I want to spray Pam into a wine glass and add some vanilla flavoring after pouring some Two Buck Chuck in and seeing if that tastes good.

*Just a quick thought on the “wine science wars”. I don’t think wine critics view themselves as scientific arbiters of wine, but I do think they present themselves as having far more precision than the studies suggest they do. Wine blogger Heimoff asks why we never see a headline saying that restaurant reviews are all junk science. Because they don’t claim to be picking up 12 distinct flavors from a single component, unlike a wine reviewer who honestly said a single wine had flavors of “red roses, lavender, geranium, dried hibiscus flowers, cranberry raisins, currant jelly, mango with skins, red plums, cobbler, cinnamon, star anise, blackberry bramble, whole black peppercorn” (perhaps take that review with a grain of salt, since the story sounds like it is coming from an ad almost).

I also think they do have a harder job than the restaurant critics. At a restaurant, you get to examine multiple things: the food, the service, the atmosphere, etc. Heck, even if you only focus on the food, that still leads to several different things to examine, whether that’s multiple courses at a Michelin-rated restaurant or just the multiple ingredients in a sandwich. A wine critic has one thing to look at, and they try to go into intense detail. But humans aren’t meant for analytical chemistry. I think things like this Salt article are perfect. It does show what people can appreciate in a wine and what the industry tries to create.

Maybe They Could Bottle It

The Atlantic, once again, proves to be a source of weird and wonderful science stories.  And I am learning I love Rebecca Rosen’s reporting/blogging significantly more than Alexis Madrigal. The LA Times interview goes into a bit more detail. Dr. Barbara Lollar and her group from the University of Toronto found water trapped underground in a copper mine in Ontario that has basically been isolated from the rest of the Earth for at least a billion years. And it’s gotten kind of… ripe after being stuck in dissolvable minerals after all this time. Lollar describes it as having “the consistency of a very light maple syrup”. And it has so many minerals dissolved in it that contact with air starts to turn the water orange.

And yet that still seems less weird than this new water at Harris Teeter

And yet that still seems less weird than this new water at Harris Teeter

Evidently it is also very salty. There’s no numbers listed for that. Lollar just mentioned that she tasted it and said it was the saltiest water she ever tried. Yeah, so evidently she not only drank a sample of this, but she semi-regularly drinks other ancient water samples to get a feel for the mineral content. But she won’t let her students sample the most vintage H2O ever. What amuses me most is that Lollar and others say the water could support life and yet she still drinks it. This just sounds like the set-up of a terrible sci-fi B movie about an ancient microbe infecting a person in the present to take over Earth in the present.*

*Yes, I know, the odds of a 1 billion year old microbe being able to infect a modern human after their environments are  separated and they evolve separately are slim. But we do still have instances of invasive species being able to thrive in environments they weren’t native to. And it seems slightly more likely that a billion year old microbe will find something it could attack in a eukaryotic cell, since eukaryotes (the giant group of organisms with cells that have nuclei and organelles that includes plants, animals, and fungi) have been around for an estimated 1.6 billion years, than the few hundred million year old mammalian immune system having any idea how to respond to that.

Optics Can Be Magical

Prepare to have your mind blown by some crazy perspective… graphical perspective, that is.

The sky, exactly opposite a sunrise.

io9 has a full (but short) explanation of why we see it this way. If you don’t want to go over, here’s the even quicker version. When you’re looking at the horizon, all parallel lines along your line of sight converge to a point (one-point perspective). All the rays from the Sun hitting the Earth are roughly parallel, so when the sun rises, you see those rays fan out in all directions due to the perspective. If you turn around and face opposite the rising sun, the rays are still truly parallel, but again, the perspective forces them to converge to an opposite point.

I wonder what you would see if you looked straight up into the sky. Our brains process the sky as a sort of shallow salad bowl (the black dots)  instead of a hemisphere (white dots), so would you see some trippy ellipsoidal equivalent of lines of longitude?