What Is in Road Flares?

hhyperific 5 days ago 33 commentsRead Article on spiegl.org

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jaggederest•1 day ago

For extraction, you'd want to use different solvents that have different dissolving properties - usually something like water, ethanol, DCM, acetone, MEK, methanol, toluene or whatever.

For strontium, it looks like it's relatively soluble in short chain alcohols (methanol/ethanol) compared to the other two, so you'd crash out the potassium perchlorate by dissolving the mixture in water, then reducing the temperature to cause perchlorate to drop out of solution, then mix in a moderate amount of methanol to crash the potassium nitrate out, being left with a reasonably pure strontium nitrate, that you could then hot filter and recrystallize in anhydrous methanol if you wanted >90% purity. One or two rounds of recrystallization will leave you in the high nineties, probably above 97%.

This is a classic chemistry workup kind of problem and there are interesting engineering challenges embedded in it.

Of course... practical people just buy technical grade strontium nitrate and make fireworks out of it directly, as the article says.

Athas•1 day ago

This page reads like an exasperated response to constant discussions and requests for how to extract strontium nitrate from road flares, and emphasizes that it is hard and pointless in the first place. I never noticed such discussions, but maybe it's outside of my bubble! Quite an amusing read nonetheless.

terribleperson•about 20 hours ago

That sounds like the kind of discussion that might show up on the venerable sciencemadness.org

jimnotgym•1 day ago

>Some older flare formulations also had things such as pitch, asphalt, wax, tallow, potassium chlorate and black powder. Those are not likely to be part of modern flare formulations.

Most of the formulations in the table have charcoal, potassium nitrate or other oxidiser, and sulfur. Surely, to say they don't contain black powder is semantics, when they contain the ingredients of black powder?

oasisbob•1 day ago

You can look at pasta and bread the same way.

Potassium perchlorate and powdered aluminum can be used to make flash powder. Just because road flare contains both doesn't mean it's going to explode in your hand.

bookofjoe•1 day ago

https://www.amazon.com/Visibility-Eco-Friendly-15-Minute-Saf...

>Specified and approved by the Bureau of Explosives and Underwriters Laboratories. No expiration date on road flares, the date shown on the flare is manufactured date. Orion flares will burn in all weather conditions, waxed Flare w/Plastic Cap. 15 Minute Burn Time — Non Perchlorate Formula

NoSalt•1 day ago

I've always wanted to activate a road flare. It looks so cool when they do it on TV and the movies.

mikestew•1 day ago

Amazon and your local auto parts store both sell them, they’re not expensive, so what’s holding you back? Just remember that they burn for 20 minutes or so, and you can’t extinguish them. (Well, a bucket of sand works.)

gwbas1c•about 23 hours ago

So what happens when they are put into a bucket of water?

Answered my question: https://www.youtube.com/watch?v=SldmXuV3cLI

mikestew•about 22 hours ago

There’s a reason that I specified sand in your bucket. :-)

NoSalt•about 23 hours ago

To be honest, I would be slightly nervous about getting into trouble with the law.

dylan604•about 23 hours ago

For what? What are you planning on doing with a lit road flare that would get you in trouble?

fergie•1 day ago

I'm missing some context here: Why do we want to extract strontium nitrate anyway?

dmurray•1 day ago

The author's home page reveals that he has an interest in amateur rocketry. Strontium nitrate doesn't sound suitable as a propellant, so I suppose he wants it to generate visual effects.

https://spiegl.org/unsorted/unsorted.html

BenjiWiebe•about 22 hours ago

Red rocket engine flame looks really neat.

throwup238•1 day ago

Because we don’t have a Sigma Aldrich account.

jaggederest•about 21 hours ago

And more importantly we don't want to pay.. $360 a kilo for reagent grade. Yikes.

ck2•about 24 hours ago

I don't know why this makes me think of it but the coolest "burning" thing has to be an "Oxygen Candle"

https://en.wikipedia.org/wiki/Chemical_oxygen_generator#Oxyg...

https://minearc.com/oxygen-candles-providing-emergency-air/

https://www.youtube.com/watch?v=g3Ud6mHdhlQ

Unfortunately they are "boring" in comparison, no flame/glow

brazzy•1 day ago

Um... some context? What even are road flares? And why would I want to extract strontium nitrate from them?

red_admiral•1 day ago

(Road) flares aka. "pyros" are like fireworks that stay in place and give off bright light and heat. Their intended use is to warn others of accidents, or for a ship in distress, to help a coast guard helicopter find it. As safety devices, they're not hard to get in some countries/states.

Extracting strontium nitrate lets you .. build explosives from readily available materials? Or it would except, as the page shows, you need a pretty good chemistry set and knowledge to do this, at which point you probably don't need pyros.

I don't know if it's just a Europe thing, but pyros are illegally used a lot at soccer (EU: football) matches and other sporting events. Picture on this page: https://scottishfsa.org/pyros-burn-young-dundee-fan/

rob74•1 day ago

I'm from Germany, and I have never once seen a road flare used on an actual road. Not sure if they're even legal in the EU (sounds like a bad idea to carry explosive or highly combustible stuff around in your car?), here in Germany all you as the driver have to do to secure an accident site is set up a reflective "warning triangle" at a specified distance and wear a safety vest when outside the car. I have seen plenty of pyros at football matches, although I'm not sure those are being sold as "road flares".

jimnotgym•1 day ago

You can however buy 'distress flares' in most of Europe, since many seagoing craft are recommended or indeed required to have the nasty, dangerous things.

asmallcat•about 23 hours ago

I see them on roads all the time in Canada (Tow truck operators and law enforcement use them quite a lot). That being said, most vehicles on the road carry a large tank of highly combustible stuff which is a lot more volatile (e.g: Gasoline)

jfim•1 day ago

They're not typically used for passenger cars, but semi truck drivers and first responders use them since they're visible from farther away in both regular and low visibility situations like fog, rain, and at night.

tlavoie•about 22 hours ago

How does your car move around _without_ containing explosive, highly combustible stuff?

flal_•1 day ago

They are mandatory on boats, even for smaller ones, and that's how you can get some in Europe.