Skepticism

Liquid Nitrogen Does NOT Turn Tear Gas Solid!

This post contains a video, which you can also view here. To support more videos like this, head to patreon.com/rebecca!

Transcript:

Okay so the laptop I use to make these video has been in the shop for the past week-and-a-half so I’m sorry that this is coming at you a little late. The news cycle moves so quickly that you’ve probably already forgotten that Hong Kong even exists, but allow me to take you back to the heady days of August 31, 2019, when riot police were firing tear gas into peaceful crowds of protesters who object to a new bill that would allow officials to extradite “criminals” to China, putting citizens and visitors to Hong Kong at serious risk of being silenced by the increasingly dystopian Chinese government.

On August 31, the Twitter user “PatriotCoburn” posted a video of a Hong Kong protester, writing, “Holy Shit the protesters in Hong Kong are grabbing the canisters of tear gas dropping it into liquid nitrogen and turning it into its harmless solid form.”

Everyone retweeted this. EVERYONE. I saw this all over my timeline. Why? Because it has everything for the SJW science nerds I follow: a cause we can all get behind! Chemistry! And human ingenuity when it’s most needed.

Unfortunately, there are issues. Of course there are issues or I wouldn’t be making a video about it two weeks too late to do anything about it.

Here’s the first issue: that’s not how tear gas and liquid nitrogen and reusable water bottles work. Someone on Twitter almost immediately pointed that out to PatriotCoburn: 

“That is not LN2. They would have lost their hand from the resulting mechanical explosion after capping and shaking that thermos. It was prolly just water.”

That’s (mostly) correct, despite PatriotCoburn’s bafflingly stupid reply saying that it can’t be true because scientists and ice cream parlors use liquid nitrogen. Throwing liquid nitrogen into a water bottle and screwing the cap on would basically create a bomb. You should never, ever keep LN2 in a closed system because the liquid will begin boiling, pressure will quickly build up, and if it has nowhere to go, it goes boom. The last place you want LN2 is in a sealed bottle that hasn’t been specifically built to hold it, and if you throw in an active tear gas canister pumping out mist, your little pressure bomb will be cooking in no time.

So no, it wasn’t liquid nitrogen, nor was it vinegar as another viral tweet claimed. Amazingly, “berniespofforth” took the video from the viral PatriotCoburn tweet and just changed the liquid inside to vinegar with zero evidence, but doubling down on the pseudoscience of it all: “When chemistry graduates are faced with tear gas in Hong Kong they used chemistry to turn it into solid form, by shaking it in vinegar and rendering it useless. That’s education for you! Bravo.” Yeah, no. Tear gas isn’t actually “gas” — it’s solids or liquids that have been aerosolized in order to make them easier to spray in people’s faces. So vinegar will not do anything to tear gas, and furthermore though it’s often used as a home remedy to treat people who have been hit with tear gas, it’s probably not even good for that considering that it’s also an acidic irritant that has been used for similar purposes as mace.

Wanna know the real way to treat tear gas? Not acids, but antacids like Maalox, mixed with water and sprayed on the affected areas. Safe and effective. That’s education for you, but I doubt tweeting that will get that information to go viral, because actual science isn’t always quite as sexy and fun as pseudoscience.

Here’s another thing that won’t go viral: the water bottle was filled with mud. Simple mud stopped the tear gas canister from continuing to operate. Why? Simple: the canisters operate by quickly heating up a powder inside that is neutral at room temperature but hurts humans when cooked. Getting the canister wet stops that reaction from taking place and also neutralizes the powder, which is why it’s equally effective to pour water on the canisters. That’s also why the treatment for people exposed to tear gas is mostly just water.

It’s still science, it’s still human ingenuity, but it doesn’t quite have that viral bite to it anymore, does it?

What’s the harm in misinformation like this going viral? Well, the worst case scenario is that you send some well-meaning but gullible people out into the streets to make actual fucking pressure bombs. A less deadly but still bad result is that you convince people that they don’t have the right materials to fight these types of brutal police tactics when in fact they might (I say “might” because you do need a lot of water to stop a decent-sized tear gas canister and sometimes it’s just not logistically possible).

And here’s one final bit of harm: by mindlessly retweeting this misinformation, you may be elevating the platform of a Nazi. Yep, that’s right, “PatriotCoburn” is a racist, sexist, anti-choice, conspiracy-mongering, climate change-denying white supremacist, and if you retweeted him, you gave him a little thumbs up that helped push him to 900 followers and counting.

So this is me, finally back to making videos after two very long weeks of screaming at the wall, reminding you that if something sounds too cool to be true, double check it before you retweet. And maybe consider clicking through to see what kind of person you’re retweeting, too.

Rebecca Watson

Rebecca is a writer, speaker, YouTube personality, and unrepentant science nerd. In addition to founding and continuing to run Skepchick, she hosts Quiz-o-Tron, a monthly science-themed quiz show and podcast that pits comedians against nerds. There is an asteroid named in her honor.

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One Comment

  1. I previously made this comment on the Patreon comments section, but suspect I did something wrong so I’m re-posting it here (more or less), mostly because it contain a major brag. :-)

    A closed container (or one with only a small leak) of a liquid whose boiling point is below the external temperature can explode suddenly and with great energy when the liquid boils. This is called a Boiling Liquid Expanding Vapor Explosion, or BLEVE.

    The liquid can boil because the container is in a fire that heats the liquid above it’s boiling point. This is what often happens when tanker trucks or rail cars are involved in a crash or fire. The explosion is not caused by the flammable contents of the tank burning, though if the contents are flammable, it can make the results much more catastrophic. However, even water can explode this way. The Mythbuster’s launching a hot water heater through the roof of a house was a boiling water BLEVE.

    A BLEVE can also occur if the liquid’s boiling point is below normal room temperature and just heats up due to exposure to room-temperature air or water. This is what causes an uninsulated bottle of liquid nitrogen to explode, especially when it’s dropped in a bucket of water. (The water will warm up the nitrogen much more quickly than air would.)

    A strange case of a BLEVE is when the liquid in the tank is under great pressure. The pressure raises the boiling point of the liquid above surrounding temperature, so it won’t boil. However, if the tank springs a leak, the pressure will drop, and the boiling point will go down. When it drops below the external temperature, the liquid will boil and the tank will explode. I think this is what caused the high-pressure helium tanks to explode in both SpaceX Falcon 9 rocket explosions.

    If you look up BLEVE in Wikipedia, you’ll see my dad cited as one of the people who discovered and named the BLEVE. Woot!

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