What Is in Road Flares?

39 points by hyperific 36 days ago | 33 comments

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 32 days 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 32 days ago | |

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

jimnotgym 32 days 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 32 days 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.

ck2 32 days 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

bookofjoe 32 days 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 32 days ago |

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

mikestew 32 days 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 32 days ago | | |

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

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

NoSalt 32 days ago | | |

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

fergie 32 days ago |

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

dmurray 32 days 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 32 days ago | | |

Red rocket engine flame looks really neat.

throwup238 32 days ago | |

Because we don’t have a Sigma Aldrich account.

jaggederest 32 days ago | | |

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

brazzy 32 days ago |

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

red_admiral 32 days 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 32 days 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".