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Author: Subject: Sodium Azide contact with metal
g222
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[*] posted on 31-3-2018 at 03:32
Sodium Azide contact with metal


I've seen warnings like this:

"Contact with metal shelves, containers, and utensils can result in formation of heavy metal azides and the risk of explosion."

"Do not use a metal spatula to weigh quantities of sodium azide. A ceramic spatula should be used."


Can a brief contact of Sodium Azide (in solid or aqueous form) and metal (like spatula) really create enough heavy metal azides to cause an explosion? How would that even work?
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LearnedAmateur
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[*] posted on 31-3-2018 at 04:10


I wouldn’t imagine that more than a negligible quantity would be produced but it MAY slightly increase the shock sensitivity. Aqueous mixtures are a different matter though, since they’re not explosive but would facilitate a greater reaction rate so it would present an increased risk if you were to make a dry solid from it.

A few second transfer using a spatula shouldn’t matter much, these warnings are typically worst case scenarios and are often highly exaggerated. However, storage is a different concern since it’ll obviously have longer to react if you did happen to have heavy metals in contact - for example if you spilled a little onto metal and left it for a while.

Just be careful with it and immediately clean up any spills and you’ll be fine. I’m sure you’re aware of the dangers NaN3 presents on its own so just abide by basic safety.




In chemistry, sometimes the solution is the problem.

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g222
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[*] posted on 31-3-2018 at 07:55


Thanks, that make sense.
btw. those aqueous mixtures are never explosive? i.e. I've heard about drain pipes explosions when NaN3 solutions were poured down the drain, but I guess that could only happen after those pipe have dried out (i.e. during a maintenance work on pipes)?


Quote: Originally posted by LearnedAmateur  

Just be careful with it and immediately clean up any spills and you’ll be fine. I’m sure you’re aware of the dangers NaN3 presents on its own so just abide by basic safety.


Yes, I'm aware of NaN3 dangers, just those parts about explosions from brief contact with metals seemed way too exaggerated.
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LearnedAmateur
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[*] posted on 31-3-2018 at 08:40


Explosives are usually so when dry (anhydrous, for oily ones like nitroglycerin), AFAIK you can have a solution that will never explode even when subject to pretty harsh conditions. It’s like when preparing diazonium salts, you can have a solution of them and it will only decompose to nitrogen gas under reacting conditions, but the when allowed to precipitate, they become explosive.

I believe it’s a different explosive mechanism - the buildup in pressure caused by nitrogen gas during decomposition, and via hydrogen azide, I could be wrong but I highly doubt it’s caused by explosive decomposition of the azide itself.

[Edited on 31-3-2018 by LearnedAmateur]




In chemistry, sometimes the solution is the problem.

It’s been a while, but I’m not dead! Updated first of June, 2019. Shout out to Aga, we got along well.
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g222
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[*] posted on 31-3-2018 at 09:40


I found this report about one such incident:

"In April 2010, a maintenance worker was replacing a sink in a hematology lab. Laboratory staff had always kept a stream of running water in the sink to dilute and flush the sodium azide. However, the copper pipe had dried out during the replacement process. This allowed sodium azide residue to react with the pipe, forming lead and copper azides. While the maintenance worker was assembling the sink and drain pipe, the pipe exploded due to the friction and shock from the azides being disturbed. The maintenance worker sustained serious permanent injury from the incident."

http://www.lni.wa.gov/safety/hazardalerts/SodiumAzide.pdf
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Justin Blaise
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[*] posted on 31-3-2018 at 20:13


I don't think the mechanism of explosion is necessarily different in solution or solid state. Both reactions are explosive due to the release of gas and the energy of the decomposition of the explosive. It is unlikely that hydrazoic acid is involved in the explosive decomposition of solutions or solid azides. It is true that in solution azides are not as sensitive, but wouldn't say that solutions are never explosive. Under conditions that cause them to rapidly release gas, lots of solutions can be explosive.
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g222
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[*] posted on 2-4-2018 at 07:43


Do you know maybe at which concentrations and conditions they become unstable? i.e. I know that hydrazoic acid is very stable in dilute solutions, but becomes very sensitive and explosive in concentrated solutions (>17%).
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