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Katie
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[*] posted on 21-4-2020 at 17:56
Question about lead azide synthesis


In my dex. Lead azide synthesis, I follow a procedure which states “NaOH is added to lower the pH to 5”. I assumed they meant “raise the ph to 5” so that is what I do, although I use potassium hydroxide instead.

Then recently I read a scientific paper that said the reaction should be carried out in basic conditions, but 5 is acidic!

What is the correct ph to synthesize dextrinated lead azide? And can I rinse the LA I already made with a pH of 5 in a hydroxide or bicarb solution to emulate having synthesized it in a basic solution?
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Etanol
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[*] posted on 22-4-2020 at 01:25


You noticed correctly. pH of unclean Pb(NO3)2 is 2...4, clean nitrate have pH about 4,6..5.
Recommended value pH to dextrinated lead azide from lead nitrate is 4,3..4,6. The correct synthesis is described in the patent US3173818 "Manufacture of dextrinated Lead Azide" and " Bagal. Chemistry and technology of initiating explosives." p230-234 - "Method for the continuous production of lead azide". Solutions of NaN3 and Pb(NO3)2 should be simultaneously added to the dextrin solution within 30-60 minutes
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Rhodanide
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[*] posted on 22-4-2020 at 12:09


When I speak of my experiences with any sort of Azides salt in acidic medium, none of the stories turn out good. HN3 will find any way of escaping even under the mildest of acidic conditions. The Pb azide syntheses I've seen try to keep the ph at the very least neutral or very slightly basic using dilute aq NaOH. Any sort of azide synthesis in the presence of acid is, in my opinion, ludicrous. HN3 is no joke.



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Katie
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[*] posted on 22-4-2020 at 13:27


Quote: Originally posted by Etanol  
You noticed correctly. pH of unclean Pb(NO3)2 is 2...4, clean nitrate have pH about 4,6..5.
Recommended value pH to dextrinated lead azide from lead nitrate is 4,3..4,6. The correct synthesis is described in the patent US3173818 "Manufacture of dextrinated Lead Azide" and " Bagal. Chemistry and technology of initiating explosives." p230-234 - "Method for the continuous production of lead azide". Solutions of NaN3 and Pb(NO3)2 should be simultaneously added to the dextrin solution within 30-60 minutes


Thank you for that patent, I noticed several things I’d like to do differently in my next synth.
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Etanol
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[*] posted on 22-4-2020 at 15:45


Quote: Originally posted by Rhodanide  
When I speak of my experiences with any sort of Azides salt in acidic medium, none of the stories turn out good. HN3 will find any way of escaping even under the mildest of acidic conditions. The Pb azide syntheses I've seen try to keep the ph at the very least neutral or very slightly basic using dilute aq NaOH. Any sort of azide synthesis in the presence of acid is, in my opinion, ludicrous. HN3 is no joke.


I understand your perplexity. But the "neutral" Pb(NO3)2 solution does not exist. Measure the acidity of your nitrate. At pH7 only Pb(OH)NO3 and Pb(OH)2 are exists. Nice article in Russian: "The influence of some factors of product synthesis on the formation of crystal grains (for example, the production of dextrinated lead azide ) Part 1,2,3"
https://cyberleninka.ru/article/n/vliyanie-nekotoryh-faktoro...
Authors show grains of lead azide at pH 3,7...4,6 in Part 3.

[Edited on 22-4-2020 by Etanol]

[Edited on 22-4-2020 by Etanol]
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