Sciencemadness Discussion Board

collect gas in a cylinder

ecos - 4-10-2016 at 05:50

Hi All ,

I would like to collect gasses and store them in a metal cylinder under pressure.

Lets take N2O as an example :



so if the gas is collected in the beaker , how to collect it and store it in a metal cylinder under pressure ?!

sorry if the question looks very basic but I lag the concept here.

Jstuyfzand - 4-10-2016 at 06:26

My first guess is to lead the gas into a compressor

Sulaiman - 4-10-2016 at 06:41

negligible expertise but that never stops me;

. I expect that a critical step is the drying of any gas before storage in a metal container,

. and remove any contaminants (e.g. ammonia, acids ...)

. gasses produced by electrolysis (such as O2 and H2 from H2O) can self-pressurise,
e.g. I think that electrolysis of water with 100Atm pressure is only 20% less efficient than at 1Atm.

. otherwise a compressor will be required

. remember to check the compatibility of gas + metal in each case

. I guess that in most cases it is cheaper (and a lot safer) to buy gas in bottles if you use significant quantities

. if for small scale hobby use it is better to make gasses on demand rather than storing potential bombs.

[Edited on 4-10-2016 by Sulaiman]

Heavy Walter - 4-10-2016 at 06:41

Handling gases is tricky, mainly if you need some grade of purity.
You need to purge/evacuate your receiving container. It is strongly reccomended to have access to some evacuating device (at least a mechanical pump).
Some gases can be handled/trapped freezing the container and sending you gas into; then you can pump out residual -non condensable- gases. But you need to calculate the amount of frozen gas and figure out the final pressure when defrostening you container in order not to rise excessively the pressure, with the risk of explosion.
As ancillary support you will need some valves, able to support vacuum and some positive pressure, pressure/vacuum gauges as well as adecuate piping.
Not easy to all amateurs.

Maroboduus - 12-10-2016 at 18:31

You need to replace the beaker with something with a hose fitting on the top (a valve would be nice too) so you can tap the gas out with a pump.

Other schematics I've seen for making N2O from ammonium nitrate include at least bubbling it through water before trapping it.
I think the more elaborate ones include washing it with an alkali. You don't want any other stray decomposition products in there because some are corrosive, and if somebody tries to breathe it it might do a bit of damage. Those same impurities might also be hard on the container if it isn't acid proof.

Also, if you're using low grade ammonium nitrate, there may be a lot of other things in the gas besides the oxides of nitrogen.
Some tech grade stuff is pretty dirty looking.



And let's not forget the whole detonation problem. I'd much rather use a more controllable heat source just to be safe. Sure, it almost never detonates doing it with a burner flame, but with explosives almost isn't a great safety standard.

Beyond that, dry it(pass it slowly through a container with some drying agent in it, like calcium chloride & etc), and pump it into a cylinder. You won't need much of a pump unless you're trying to make a whole lot, in which case you'll have a whole lot of that potentially explosive salt heating away and hopefully not going off (even heating gets harder with bigger samples so the risk goes up unless you find some way to stir it and heat more evenly than just putting a flame under it.

EDIT: I see you're mostly an energetic materials guy, so I guess you're probably more interested in using it as rocket fuel or something like that rather than selling it at Dead shows. (Do they still have those, or are the Dead all dead?) Also, with your being an energetic materials guy I feel a bit better about your heating ammonium nitrate. You obviously have experience with being careful with reaction conditions.




[Edited on 13-10-2016 by Maroboduus]

[Edited on 13-10-2016 by Maroboduus]

[Edited on 13-10-2016 by Maroboduus]

brubei - 13-10-2016 at 08:02

place ammonium in a full aluminium chantilly propellant like this and heat



they can keep 37 bar safely

[Edited on 13-10-2016 by brubei]

Maroboduus - 13-10-2016 at 20:56

Seriously? 37 bar? That's 550 psi or so.

Wonder if you could throw a magnetic stirrer in there, and some catalyst and use it as a hydrogenator?

Be nice to replace the charging nipple with a pressure gauge to measure uptake.

unionised - 13-10-2016 at 23:56

Quote: Originally posted by brubei  
place ammonium in a full aluminium chantilly propellant like this and heat

[Edited on 13-10-2016 by brubei]

Well, that's one way to discover that aluminium loses its strength very quickly when heated.

ave369 - 14-10-2016 at 02:08

What pressure will be generated if you put bicarbonate of soda and some acid in a cylinder (e.g. a CO2 fire extinguisher, they are pretty pressure resistant) and screw in the valve?
Quote: Originally posted by unionised  

Well, that's one way to discover that aluminium loses its strength very quickly when heated.


Again, one can use CO2 fire extinguishers. They are typically made of steel.

[Edited on 14-10-2016 by ave369]

Maroboduus - 14-10-2016 at 11:11

Quote: Originally posted by unionised  
Quote: Originally posted by brubei  
place ammonium in a full aluminium chantilly propellant like this and heat

[Edited on 13-10-2016 by brubei]

Well, that's one way to discover that aluminium loses its strength very quickly when heated.


Not as quickly as the plastic parts some of those things have.

They do make them in stainless steel. The Webstaurant store sells one for around $60 American. I doubt the valves are all steel though, and there's still what looks like plastic on the outside, albeit non-structural.

EDIT: Actually, THAT one pictured looks like the nozzle is plastic. And they have rubber O-rings in the valves on all the ones I can find schematics for.


[Edited on 14-10-2016 by Maroboduus]

unionised - 14-10-2016 at 12:29

Quote: Originally posted by ave369  
What pressure will be generated if you put bicarbonate of soda and some acid in a cylinder (e.g. a CO2 fire extinguisher, they are pretty pressure resistant) and screw in the valve?

Quote: Originally posted by unionised  

Well, that's one way to discover that aluminium loses its strength very quickly when heated.


Again, one can use CO2 fire extinguishers. They are typically made of steel.

[Edited on 14-10-2016 by ave369]

That's a great way to discover that steel loses its strength very quickly when heated.

Heating ammonium nitrate in a closed vessel is also pretty nearly identical to setting off a pipe bomb. How do you expect it to know which outcome you want?


[Edited on 14-10-16 by unionised]

ave369 - 15-10-2016 at 05:53

Quote: Originally posted by unionised  
How do you expect it to know which outcome you want?
[Edited on 14-10-16 by unionised]


Put it in a campfire, sit in a nearby gully at a safe distance and watch. If it explodes, it's fun and no one is hurt. If it doesn't, you have an usable cylinder of N2O.

ecos - 9-11-2016 at 09:19

As far as i know , AN is insensitive EM. it needs a detonator to set it.
I am not planning to prepare N2O.
I just wonder how they collect gasses from experiments.