Sciencemadness Discussion Board

Make Alkali metals from controlled decomp of azides??

fusso - 12-4-2018 at 11:31

Alkali azides explode on heating to form respective AM and N2 is a well known fact.
But is it possible to heat carefully/ in a controlled manner to make it decomp slower and isolate the AM formed? If so how?

RawWork - 12-4-2018 at 11:52

It's suspicious. They are sensitive to shock, friction, etc. But if we take that out of consideration, they can be decomposed by using lower temperatures. Who knows, maybe azides are sensitive because of reaction with oxygen. If that's true, that means they are not sensitive, and just heat them however you like. If they are, if we ignore friction and other possible death and explosion possibilities, by boiling them in container which is placed on water, in that case it will have max temperature of 100 C obviously. If no reaction observed, then move to some higher boiling point liquid as bath for container. Maybe each increased by 20 or 50 C. Or just add more salt to water and use that like that...if you know what i am talking about. This is based on fact that when you immerse sodium azide container in liquid, liquid won't be able to heat above it's boiling point, and temperature can be kept cosntant.

I read in various terrorism books that whenever you try/test or work first time with something, do it with extremely small quantity, about size of fingertip or less. That's called practice. Theory is another world, practice is another. We can only talk here. Useless. Test it, see what you observed, detect differences... Try with air presence, then without. Maybe it's explosive only in air, but not when alone or with N2. That makes sense.

According to "handbook of inorganic chemicals":

In the laboratory, nitrogen may be generated by several methods, such as carefully decomposing sodium azide: 2 NaN3 → 2 Na + 3 N2

Potassium can be produced by thermal decomposition of potassium azide: 2 KN3 → 2 K + 3N2

Although it says: "Sodium azide is a toxic as well as an explosive substance".

So you see it works, although it's explosive, so beware, safety first, in small portions :mad:

[Edited on 12-4-2018 by RawWork]

Bert - 12-4-2018 at 13:04

Go watch a slow motion video of an auto airbag inflating.

Please do not try this. If you provoke an azide into decomposing, it will probably do so rather briskly, with lots of hot N2. I lost some hair to this reaction some years ago, and was just lucky not to do worse dammage.

The metal will be a vapor, you won't capture it easily, or at all, most likely. Sodium azide is fairly expensive as well as somewhat hard to obtain in many countries. Save it for better uses.

NeonPulse - 12-4-2018 at 15:53

There’s this video: https://www.google.com.au/url?sa=t&source=web&cd=1&a... here is the follow up:
http://chemistry-chemists.com/N6_2016/ChemistryAndChemists_6...

I did visit the page where the poster describes his attempt however it was in Russian and needed to be translated. He had no real success in actually isolating the metal and even described doing it under vacuum. He stated that once it was bought back up to atmospheric pressure the metal oxidised immediately. It seems to reach a point where it decomposed almost instantaneously on heating. I will be trying this very method in the near future to see if I can improve on the process but judging by the post he wrote it looks doubtful. Perhaps charging the tube with argon may help. I probably wouldn’t say that this is a viable method to obtain barium but experimentation needs to prove or disprove the idea.

BromicAcid - 13-4-2018 at 05:18

Decomposing alkali azides to yield the free metal is a very old and well known technique. IIRC it was at one time the main method of preparation of cesium in the labratory (back when it was still a curiosity). I do not have any refs on hand but I have read many over the last few decades. Will try to find something for you later.

fusso - 13-4-2018 at 15:04

Quote: Originally posted by Bert  
Go watch a slow motion video of an auto airbag inflating.

Please do not try this. If you provoke an azide into decomposing, it will probably do so rather briskly, with lots of hot N2. I lost some hair to this reaction some years ago, and was just lucky not to do worse dammage.

The metal will be a vapor, you won't capture it easily, or at all, most likely. Sodium azide is fairly expensive as well as somewhat hard to obtain in many countries. Save it for better uses.


Actually you can make it from hydrazine & nitrite.

[Edited on 13/4/18 by fukko]

unionised - 14-4-2018 at 03:16

OK,
Don't play with sodium azide- it's roughly as toxic as sodium cyanide.

However, heating sodium azide won't generally cause and explosion (unlike the heavy metal azides).

Posting videos of airbags as a basis for saying you shouldn't heat azides makes as little sense as posting videos of gunpowder and saying "that's why you shouldn't heat sulphur".

The stuff in airbags is* a mixture of sodium azide, potassium nitrate and silica.

Without the oxidant , the reaction is much less violent.

The nitrate is there to speed up the reaction so the bag inflates quickly.

The silica is there as an acid anhydride to react with the sodium oxide that is formed.
It is considered better to have the sodium oxide react with the silica, rather than with the face/ lungs/ eyes of the person who hits the airbag.

Sodium silicate's not very nice but it's less of an issue than the oxide would be.


* I think it may be a case of it "was", rather than it "is", the azide's toxicity made it unpopular.

Bert - 16-4-2018 at 14:33

I would agree, he is at least as likely to poison himself as burn/blow himself up. If he can get the pure chemical, he would certainly be more likely to poison himself- But:

If you are a kid out looking for some Sodium azide, what is your probable source? A junked airbag unit from an old car??? Maybe we could open that can up quicker with power tools, a grinder should work good?

Shortly after the good idea fairy strikes, there might be a quick, hot POOOF!

[Edited on 4-16-2018 by Bert]

dillee1 - 18-4-2018 at 20:56

Just curious why would you want to manufacture your own sodium metal? Given that this industrial metal is both cheap and easily available from market?

LearnedAmateur - 18-4-2018 at 22:07

There are multiple reasons why, if you take a look at various synthesis threads around the forum you’ll see your sort of question pop up, to which there will be various answers along the lines of:
It’s a chemistry exercise to study the reaction,
The reagent isn’t available where (OP) lives,
The reagent is too expensive for (OP’s) budget whereas the precursors are not,
Post/couriers won’t ship this reagent; amongst others.

I myself have bought sodium metal before but if there’s a chance and cheap/free way to make it, andyou’ll learn something in the process - maybe not ‘this is how I lose hair and/or fingers’ - then that’s a good reason to do it yourself.

woelen - 18-4-2018 at 22:46

I tried the making of sodium from NaN3 in small amounts. It actually works, but you lose a lot of the sodium in the process in the form of a grey mist.

I did the experiment as follows (do this OUTSIDE, there is a chance of cracking and instant fire):
- Take a big spatula of NaN3 and put this in a large test tube (18 mm diameter, 20 cm length).
- Pour in some liquid butane gas, or blow away the air with propane. Even better is nitrogen or argon. Do not use CO2.
- Immediately loosely stopper the test tube with a piece of cotton wadding. I used the liquid butane option because after stoppering the test tube with the piece of wadding, still some gas is produced by evaporation, making the test tube really free of air.
- Once there is only NaN3 and the gas in the test tube, start heating carefully.
- At a certain point, a violent but not explosive reaction occurs. The NaN3 quickly decomposes, giving off a grey mist, and small globules of matallic Na remain behind in the bottom of the test tube. The glass of the test tube becomes covered with a greyish "frost".
- Allow the test tube to cool down and open it. The grey "frost" turns white almost immediately when air comes in the test tube.

I simply added some water to the test tube. You nicely see pieces of orange fire and see violent fizzling when the little globules come in contact with the water.

Based on my experience, I do not consider this a good method of making sodium. You lose a lot, as it appears in the form of a mist/smoke, which cannot easily be isolated, and the reaction is quite dangerous. I would not feel comfortable scaling it up to multi-gram quantities.

dillee1 - 19-4-2018 at 01:20

Quote: Originally posted by woelen  
I tried the making of sodium from NaN3 in small amounts. It actually works, but you lose a lot of the sodium in the process in the form of a grey mist.


Given that the boiling point of sodium being 883^C, it wouldn't be surprising sodium created is mostly in vapor phase, with some sodium condense on container wall as metal sweat.

So unless the container+atmosphere is bone dry and very clean(no metal oxide contaminant from tap water etc), the sodium vapour/sweat will immediately reacts with aforesaid. End product will be contaminated with sodium oxides/hydroxide/elemental transition metals. It won't be the ultra pure sodium metal as OP desired.

This go back to my question why does OP want to synth his own sodium metal. Industrial grade sodium are cheap and widely available. Ultra pure sodium need lab grade equipment and air free technique to obtain. Even for the later there are better way to get it than decomposing azide.

phlogiston - 19-4-2018 at 03:52

OP asked about 'alkali metals' in general. He did not specifically say thay he wanted sodium.
As Bromic pointed out, this used to be a common method for the preparation of ceasium, and IIRC for rubidium too.

RawWork - 19-4-2018 at 06:38

I don't know why azide, why not nitride? I mean nitrogen is available and data about nitrides is more available than for azides. Maybe he wants Lithium. But making azides and nitrides is bigger challenge than making pure elements from them.

woelen - 19-4-2018 at 23:12

Alkali azide is much better characterized than alkali nitride. I never have seen a compound like Na3N being offered and I doubt it is available commercially (it may not even exist in a pure state). Even a compound like NaNH2 already is hard to keep around (much harder than NaN3) and the compounds Na2NH and Na3N (if they exist) must be amazingly hard to keep around. They must be quite unstable and extremely air-sensitive. I know that NaNH2 tends to form explosive mixtures when stored in contact with air.

fusso - 8-5-2018 at 12:27

Quote: Originally posted by phlogiston  
OP asked about 'alkali metals' in general. He did not specifically say thay he wanted sodium.
As Bromic pointed out, this used to be a common method for the preparation of ceasium, and IIRC for rubidium too.

Yes, I asked about alkali metals in general, not specifying Na.