Sciencemadness Discussion Board

Liquid chlorine or ammonia via liquid propane - possible?

xfusion44 - 9-10-2016 at 14:30

Hi all!

I was wondering if it would be possible to make liquefied chlorine or ammonia by cooling them with liquid propane from propane or propane/butane LPG cylinder.

However, although this would probably be pretty hard to perform, due to minimal BP difference between propane and chlorine/ammonia, I'm more concerned about any possible reactions between chlorine/ammonia and propane/butane.

I'm guessing chlorine would react with propane/butane if enough of UV light is present, which doesn't sound good to me. Am I wrong?

What about ammonia? Are there any possible reactions between it and propane/butane?

And, if I only have 70/30 mixture of butane/propane, is it even possible to create low enough temperature or would that require pure propane cylinder?

Procedure:

1. Pouring liquid propane from LPG cylinder into the vacuum flask
2. Immersion of a glass test tube into the liquid propane
3. Starting chlorine/ammonia generator and leading the gas into the chilled test tube

Any thoughts?

Thanks!

[Edited on 9-10-2016 by xfusion44]

RocksInHead - 9-10-2016 at 18:10

I don't think there would be any chance of the NH3 or Cl2 reacting with the propane if it doesnt come in contact with it. You could try to see if it would freeze it by sealing the gasses in ampoules and then immersing them in the propane. I think there shouldnt be any chance of them reacting then.

xfusion44 - 9-10-2016 at 20:13

Quote: Originally posted by RocksInHead  
I don't think there would be any chance of the NH3 or Cl2 reacting with the propane if it doesnt come in contact with it. You could try to see if it would freeze it by sealing the gasses in ampoules and then immersing them in the propane. I think there shouldnt be any chance of them reacting then.


Unfortunately they would come in contact with propane - not in large amount if the temperature would be low enough but of course, not all gas would be able to condense, so some of it would escape the test tube, for which I thought, would be immersed directly in liquid propane. So, yes, NH3 or Cl2, at least with procedure I described in first post, would certainly be in contact with butane and propane.

As you've said, it would be a good idea to seal the gases into the ampoules and immerse the ampoules into the liquid propane, to see if the gases condense, but I'm not sure there would be enough gas in ampoules to make a visible amount of liquefied gas?

And I agree, they wouldn't react when sealed in ampoules, but of course I'd like to liquify at least a few ml's of those gases - to be able to see how they actually look like when in liquid state. If I just seal ampoules with the gas inside them, I won't get much liquid if any, at all.

Thanks!

[Edited on 10-10-2016 by xfusion44]

MeshPL - 9-10-2016 at 21:20

You don't need pure, liquid propane to liquify Cl2 or NH3, but once propane evaporates, the mixture will begin to rise in temperature from about -40C to about 0C, so remember that if you still have some liquid gas, but your ammonia or chlorine would not freeze, you probably have onlu butane left, which boils at about 0C.

j_sum1 - 9-10-2016 at 21:53

It is not something that I would do. I have used butane to get things to low temperature. But it is never a particularly controlled process. You are dealing with a volatile liquid evaporating in large quantities. It is just, well, messy. Playing with one gas is awkward enough. Playing with two is bound to be worse. And if you are using ampoules that you wish to seal... Did someone say ignition source?


I am not saying it is impossible to do cool with propane safely but you need to consider how to set things up to control the flow of your two gases. I would endeavour to keep them completely separate.


Remember that it is not the liquid propane that gets things cold. It is the evaporative cooling that does it. So, immersion of a test tube into the propane liquid is not going to do the trick. You would be better to trickle liquid propane over the surface of your test tube in a stream of air to facilitate evaporation. And then vent your evaporated propane away to somewhere safe. I would think that a dry-ice and acetone bath would be more suitable and a whole lot more convenient.


For the chlorine side of your condenser setup, remember that you don't want to work with a closed system. If you are keeping your gases separate then you will want to vent your excess Cl2 away somewhere. I think a fume hood is pretty much mandatory for any chlorine generation although maybe you would feel comfortable in a suitably evacuated outdoor space on a windy day. Good practice would be to vent through traps anyway.

In the absence of sophisticated glassware, that quickly leads to the following setup:

1. Chlorine generator (what are you using for an addition funnel?)
2. Dry by passing through CaCl2 (You don't want your system clogging up with water ice)
3. Condensing tube passing through bath of dry ice and acetone. A decent length of PVC would probably be ok.
4. Drip into a test tube, also sitting in the cold bath. A two-hole bung with glass rods would work
5. Feed excess gas through an empty container that can act as a suck-back trap
6. Bubble through a solution of NaOH

Setup will be different with ammonia. I refer you to NileRed's video on ammonia production https://www.youtube.com/watch?v=gHokrNS1ask


In all of this, a whole lot depends on what you intend to do with the liquid chlorine or ammonia. If it is not for immediate use you have containment issues. If it is just for observation, you need to plan what you will do when finished.


I have thought about this in the past -- I would love to make my own ampoules of liquid chlorine. But I have decided that I am not going to attempt this without a fume hood and I want as good an equipment setup as I can get.

xfusion44 - 9-10-2016 at 23:56

Quote: Originally posted by MeshPL  
You don't need pure, liquid propane to liquify Cl2 or NH3, but once propane evaporates, the mixture will begin to rise in temperature from about -40C to about 0C, so remember that if you still have some liquid gas, but your ammonia or chlorine would not freeze, you probably have onlu butane left, which boils at about 0C.


Yeah, but doesn't the quantity of propane affect the lowest possible temperature? Remember that there's still a large quantity of butane that needs to be cooled down to -42°C, so, would those 30% of propane be able to cool down 70% of butane to propane's BP?

j_sum1 - 10-10-2016 at 00:23

By that logic, 1% of propane would cool the 99% butane down to propane's BP. Ain't gonna happen.

The propane is first to evaporate and so its concentration in the butane will drop. As it evaporates the latent energy of evaporation comes from cooling down the remaining liquid But getting it all the way down to -42C is another matter.

xfusion44 - 10-10-2016 at 00:41

Quote: Originally posted by j_sum1  
It is not something that I would do. I have used butane to get things to low temperature. But it is never a particularly controlled process. You are dealing with a volatile liquid evaporating in large quantities. It is just, well, messy. Playing with one gas is awkward enough. Playing with two is bound to be worse. And if you are using ampoules that you wish to seal... Did someone say ignition source?


I am not saying it is impossible to do cool with propane safely but you need to consider how to set things up to control the flow of your two gases. I would endeavour to keep them completely separate.


Remember that it is not the liquid propane that gets things cold. It is the evaporative cooling that does it. So, immersion of a test tube into the propane liquid is not going to do the trick. You would be better to trickle liquid propane over the surface of your test tube in a stream of air to facilitate evaporation. And then vent your evaporated propane away to somewhere safe. I would think that a dry-ice and acetone bath would be more suitable and a whole lot more convenient.


For the chlorine side of your condenser setup, remember that you don't want to work with a closed system. If you are keeping your gases separate then you will want to vent your excess Cl2 away somewhere. I think a fume hood is pretty much mandatory for any chlorine generation although maybe you would feel comfortable in a suitably evacuated outdoor space on a windy day. Good practice would be to vent through traps anyway.

In the absence of sophisticated glassware, that quickly leads to the following setup:

1. Chlorine generator (what are you using for an addition funnel?)
2. Dry by passing through CaCl2 (You don't want your system clogging up with water ice)
3. Condensing tube passing through bath of dry ice and acetone. A decent length of PVC would probably be ok.
4. Drip into a test tube, also sitting in the cold bath. A two-hole bung with glass rods would work
5. Feed excess gas through an empty container that can act as a suck-back trap
6. Bubble through a solution of NaOH

Setup will be different with ammonia. I refer you to NileRed's video on ammonia production https://www.youtube.com/watch?v=gHokrNS1ask


In all of this, a whole lot depends on what you intend to do with the liquid chlorine or ammonia. If it is not for immediate use you have containment issues. If it is just for observation, you need to plan what you will do when finished.


I have thought about this in the past -- I would love to make my own ampoules of liquid chlorine. But I have decided that I am not going to attempt this without a fume hood and I want as good an equipment setup as I can get.


It would be done outside. I can't think of any ignition source regarding that procedure. Sealing ampoules was "RocksInHead's" idea and I wasn't planning on doing that although it would probably be a good idea, to see if it's possible to use propane for cooling. Anyways, why would there be a problem, when using a flame to seal ampoules with chlorine or ammonia? Would that ignite ammonia? For chlorine, I know it won't burn.

I don't understand why it wouldn't work if I'd just immerse the test tube into the liquid propane? Test tube would be at, say, 20°C and propane at -42°C, so when the test tube would be immersed, that'd cause the propane to evaporate and stay at this temperature.

Yeah, I know I could use dry ice and acetone bath, but it's easier for me, to get LPG and I also thought that would be an interesting way of making liquefied Cl2/NH3.

What did you mean by closed system? Like closed system where both propane and chlorine are in contact?

I'd use separatory funnel for addition.
I have CaCl2.

Thanks for the video link.

It would be just for observation. When finished I'd just bubble the chlorine through water, but I don't know about ammonia, since it can rapidly dissolve in water and cause suck-back. Maybe it could be used in some interesting reaction?

Thanks!

j_sum1 - 10-10-2016 at 01:27

Quote:
Anyways, why would there be a problem, when using a flame to seal ampoules with chlorine or ammonia? Would that ignite ammonia? For chlorine, I know it won't burn.

You forget, propane does burn. It can form heavier than air puddles on the ground and can form explosive mixtures with air. I would be cautious about attempting to seal an ampoule in the vicinity of an experiment where I had been evaporating light hydrocarbons.
Quote:
I don't understand why it wouldn't work if I'd just immerse the test tube into the liquid propane? Test tube would be at, say, 20°C and propane at -42°C, so when the test tube would be immersed, that'd cause the propane to evaporate and stay at this temperature

But propane is not at -42C. Liquid propane that you have access to is at room temperature. It only drops in temperature when you reduce the pressure and when some of the liquid evaporates. The minimum possible temperature drop that you could hope to achieve with a 30:70 propane butane mix would depend on the heat capacities of the two liquids and the heat of vaporisation of the propane. I haven't dome the calculation. But I would be surprised if -42 was feasible at that ratio.

A closed system refers to a situation where matter cannot enter or leave your apparatus. A lidded bottle for example. Or a distillation rig leading to a receiver that is not open to the atmosphere. In such a situation you have no control over the pressure of the system -- it can build up or drop. Both can cause problems -- catastrophic ones where glass breaks or minor ones where your product behaves in unexpected fashion or squirts to where you don't want it.




[edit]

I should mention in passing that ammonia (as far as I know) has a specific heat higher than any other substance -- even greater than water. This means that it takes a lot of heat transfer to cool it down to condensation point. And its latent heat of vaporisation is also high (but not as great as water.) This means you are placing a lot of demands on your propane and experiment setup to cause it to condense. The more I think about this enterprise, the more I think it is folly. You should adopt a more conventional methodology.

[Edited on 10-10-2016 by j_sum1]

woelen - 10-10-2016 at 03:29

I would simply forget about the entire endeavor. You will need to evaporate a lot of propane for liquifying a small amount of Cl2 or NH3. The Cl2 and NH3 are the least worrysome things in this entire idea. You evaporate a lot of propane and you propably will be working in a cloud of highly flammable gas around you, even on a windy day. What if there is a little static discharge? You end up being in a big ball of fire. Trying to seal a glass tube while being in or near the cloud of propane is asking for disaster, don't even think of it!

If you really want to try this kind of things, then try to get some dry ice. If you can't obtain dry ice, then simply accept that this is not within reach of your resources.

Dan Vizine - 10-10-2016 at 13:13

Quote: Originally posted by j_sum1  


3. ...dry ice and acetone. <== The only sensible route

I have thought about this in the past -- I would love to make my own ampoules of liquid chlorine. But I have decided that I am not going to attempt this without a fume hood and I want as good an equipment setup as I can get.


I have the same plans. The pressure will be 107 PSI @ RT. That's 7.3 atmospheres. So, if we'd like a safety factor of 2.5, the tube shouldn't burst until it reaches 2.5 x 107 = 268 PSI. The burst strength of 15 mm OD borosilicate with 2 mm wall is about 268 PSI. I envision 1/2 inch diameter ampoules with 2 mm walls. Should look nice. Working outside is almost as good as a hood. You must make the ampoule seal as strong as the walls. Thick seals crack sometimes. I wouldn't consider the sample done until a few weeks elapse. Quartz is often used instead of borosilicate. This eliminates cracking but makes sealing much harder.

[Edited on 10-10-2016 by Dan Vizine]

xfusion44 - 10-10-2016 at 18:19

Quote: Originally posted by j_sum1  
Quote:
Anyways, why would there be a problem, when using a flame to seal ampoules with chlorine or ammonia? Would that ignite ammonia? For chlorine, I know it won't burn.

You forget, propane does burn. It can form heavier than air puddles on the ground and can form explosive mixtures with air. I would be cautious about attempting to seal an ampoule in the vicinity of an experiment where I had been evaporating light hydrocarbons.
Quote:
I don't understand why it wouldn't work if I'd just immerse the test tube into the liquid propane? Test tube would be at, say, 20°C and propane at -42°C, so when the test tube would be immersed, that'd cause the propane to evaporate and stay at this temperature

But propane is not at -42C. Liquid propane that you have access to is at room temperature. It only drops in temperature when you reduce the pressure and when some of the liquid evaporates. The minimum possible temperature drop that you could hope to achieve with a 30:70 propane butane mix would depend on the heat capacities of the two liquids and the heat of vaporisation of the propane. I haven't dome the calculation. But I would be surprised if -42 was feasible at that ratio.

A closed system refers to a situation where matter cannot enter or leave your apparatus. A lidded bottle for example. Or a distillation rig leading to a receiver that is not open to the atmosphere. In such a situation you have no control over the pressure of the system -- it can build up or drop. Both can cause problems -- catastrophic ones where glass breaks or minor ones where your product behaves in unexpected fashion or squirts to where you don't want it.




[edit]

I should mention in passing that ammonia (as far as I know) has a specific heat higher than any other substance -- even greater than water. This means that it takes a lot of heat transfer to cool it down to condensation point. And its latent heat of vaporisation is also high (but not as great as water.) This means you are placing a lot of demands on your propane and experiment setup to cause it to condense. The more I think about this enterprise, the more I think it is folly. You should adopt a more conventional methodology.

[Edited on 10-10-2016 by j_sum1]


I said it was not my plan to seal the ampoules (and even if I wanted to do that, I would do it before I'd even set up that whole thing, regarding propane).

Maybe there was a misunderstanding? Have you thought I wanted to seal the ampoules full of liquefied gases? No. And even if I did want to do that, I'd be doing it far away from any flammable gases. Also, I thought that ordinary ampoules are too weak for the purpose of storing liquefied gases with such a high vapor pressure. I don't need a bomb, let alone toxic bomb.

"It only drops in temperature when you reduce the pressure..."

Isn't this exactly how I was planning to conduct this experiment?

I'm sorry if some of my sentences are hard to understand (I'm not native english speaker).

In my first post I said I'd fill the vacuum flask with liquid propane or propane/butane and I don't see, how the propane could stay at the same temperature when releasing it from pressurized LPG cylinder into the vacuum flask, while the cylinder itself, would of course be turned upside down (to force liquid propane out).

First thing that would happen is, that the liquid propane would come in contact with hot inside of the vacuum flask - that'd cause it to evaporate and cool down the flask which would allow the incoming propane to stay in liquid state. And when propane is evaporating, it's taking the heat away from the object that's making it evaporate, so the temperature stays at BP of propane, until it all evaporates.

Of course there are better ways, but this one is more challenging ;)

xfusion44 - 10-10-2016 at 18:46

Quote: Originally posted by woelen  
I would simply forget about the entire endeavor. You will need to evaporate a lot of propane for liquifying a small amount of Cl2 or NH3. The Cl2 and NH3 are the least worrysome things in this entire idea. You evaporate a lot of propane and you propably will be working in a cloud of highly flammable gas around you, even on a windy day. What if there is a little static discharge? You end up being in a big ball of fire. Trying to seal a glass tube while being in or near the cloud of propane is asking for disaster, don't even think of it!

If you really want to try this kind of things, then try to get some dry ice. If you can't obtain dry ice, then simply accept that this is not within reach of your resources.


Actually, the largest amount of gas would be released when filling the hot vacuum flask. Test tube itself would be cooled down pretty quickly (and with minimal amount of propane evaporation). Gas flow of ammonia or chlorine would be slow, which also means slow evaporation of propane.

I wouldn't even be standing near, when this would be going on, since I don't even have a gas mask for ammonia or chlorine. My thoughts are that the flammability of butane/propane is the last thing to worry about here. I'm much more worried about any possible reactions, between butane/propane and chlorine/ammonia. And of course, about the toxicity of Cl2/NH3. Flammability, when doing that outside (at around 5-10°C) isn't such a big of a deal, as you might think it is. I've done some experiments with liquid butane and never had any problems.

The scariest part part for me, is filling of the vacuum flask (a lot of flammable gas is released when doing this). Of course I'm doing my best not to cause any static discharge at that time and also, not to move any metal parts, until the filling process is done. After that, the LPG cylinder is moved to safe location and cover is placed over the vacuum flask, to minimize any evaporation.
Quote:

Trying to seal a glass tube while being in or near the cloud of propane is asking for disaster, don't even think of it!


I never said I thought of it.

j_sum1 - 10-10-2016 at 19:51

Again, you will need more propane than you think to get the cooling you want.
And I would be far more concerned about the propane than Cl2 or ammonia in this case. It is by far the bigger hazard.
Quote:
to minimise any evaporation

It is the evaporation that is doing the work. That is what makes it cold. You can dip your finger in a puddle of butane quite happily. It will only become uncomfortably cold at the surface where the butane is evaporating into the air.

By way of analogy, consider whether you would make ice by sitting a test tube of water in petrol. If you arranged enough evaporative cooling you could probably manage it but just sitting there will do squat. Without doing a calculation, the thermodynamics of the two situations are probably not that dissimilar.

Deathunter88 - 10-10-2016 at 21:24

Also you might not want to forget, LPG cylinders are not designed for the liquid to be directly sprayed out of the connector port. Doing so could cause a build up of static electricity and ignite the propane. There have been many incidents in the past when flammable gas cylinders were allowed to vent, only to have it catch fire seconds later.

woelen - 11-10-2016 at 00:30

I would not worry about reactions with Cl2 and NH3. NH3 does not react at all with propane or butane. Cl2 can react, but if you do this in a shady place, or in the twilight period of the day, then I see no issue with that.

I really, however, urge you to not do this, because of the high risk of fire. That's why I said that the presence of a small quantity of Cl2 or NH3 is the least of the risks you run. The real risk is not in the small quantities of Cl2 or NH3, especially because you work outside, the real risk is accidental ignition of the propane while you are near it.

unionised - 11-10-2016 at 05:37

I suspect that mixtures of LPG and chlorine can de

tonate.

xfusion44 - 13-10-2016 at 14:44

Quote: Originally posted by j_sum1  
Again, you will need more propane than you think to get the cooling you want.
And I would be far more concerned about the propane than Cl2 or ammonia in this case. It is by far the bigger hazard.

Quote:
to minimise any evaporation

It is the evaporation that is doing the work. That is what makes it cold. You can dip your finger in a puddle of butane quite happily. It will only become uncomfortably cold at the surface where the butane is evaporating into the air.

By way of analogy, consider whether you would make ice by sitting a test tube of water in petrol. If you arranged enough evaporative cooling you could probably manage it but just sitting there will do squat. Without doing a calculation, the thermodynamics of the two situations are probably not that dissimilar.


I totally agree that evaporation is the reason for low temperature. And propane would of course start to evaporate when something is placed in it, that has its temperature above -42°C. That's also the reason that LN2 starts to boil when something at room temp. is placed in it.

Gasoline is not the same thing, since it boils at much higher temp. than propane or butane, so you need to force its evaporation to get the cooling effect. If you place the test tube with water at room temp. into the gasoline, it will not boil, so it won't have any cooling effect on that test tube, unless the evaporation is forced.

[Edited on 13-10-2016 by xfusion44]

xfusion44 - 13-10-2016 at 15:35

Quote: Originally posted by Deathunter88  
Also you might not want to forget, LPG cylinders are not designed for the liquid to be directly sprayed out of the connector port. Doing so could cause a build up of static electricity and ignite the propane. There have been many incidents in the past when flammable gas cylinders were allowed to vent, only to have it catch fire seconds later.


Any references for this?

xfusion44 - 13-10-2016 at 15:56

Quote: Originally posted by woelen  
I would not worry about reactions with Cl2 and NH3. NH3 does not react at all with propane or butane. Cl2 can react, but if you do this in a shady place, or in the twilight period of the day, then I see no issue with that.

I really, however, urge you to not do this, because of the high risk of fire. That's why I said that the presence of a small quantity of Cl2 or NH3 is the least of the risks you run. The real risk is not in the small quantities of Cl2 or NH3, especially because you work outside, the real risk is accidental ignition of the propane while you are near it.


Yeah, but I have had bad experiences with chlorine and hydrogen mix (mixture detonated about 20-30cm away from my head in a glass jar - luckily the cap blew off - if the glass shattered I'd have some serious troubles + I was completely deaf for a moment). Now you know why I'm worried about this (if the thing explodes, it'd probably send all the liquid propane and butane into the air). However, that accident wouldn't happen, if I wouldn't point my flashlight at that jar.

You say you'd be more worried about propane/butane igniting - why is that?

I'm quite sure that butane wouldn't accumulate too much outside + it has that odorant added which means you can smell it even in small quantities.

Even if LPG in vacuum flask ignites, it's not dangerous as long as the vacuum flask stays in an upright position. My vacuum flask is made of stainless steel, so it wouldn't burn. The only trouble is that the flask would heat up and start releasing more gas. But I could simply cover it (to extinguish the flame), before that happens. I also have fire extinguisher ready, in case something unpredictable happens.

PS: I have a video (if you're interested) where I pour about 200ml of LPG on fire - and it's not as bad as you might think it would be.

[Edited on 14-10-2016 by xfusion44]

Deathunter88 - 13-10-2016 at 17:38

Quote: Originally posted by xfusion44  
Quote: Originally posted by Deathunter88  
Also you might not want to forget, LPG cylinders are not designed for the liquid to be directly sprayed out of the connector port. Doing so could cause a build up of static electricity and ignite the propane. There have been many incidents in the past when flammable gas cylinders were allowed to vent, only to have it catch fire seconds later.


Any references for this?


I can't find the reference for LPG specifically anymore, but I remember seeing it somewhere. However I found this video by the CSB on propylene cylinders doing the same thing.

https://www.youtube.com/watch?v=-_ZLQkn7X-k

ave369 - 13-10-2016 at 22:38

Forget propane, use cryohol. Cryohol is made from ethanol and dry ice. Dry ice can be obtained from CO2 fire extinguishers. The temperature of cryohol is -79 C, which is more than enough to make liquid chlorine.

xfusion44 - 14-10-2016 at 17:46

Quote: Originally posted by Deathunter88  
Quote: Originally posted by xfusion44  
Quote: Originally posted by Deathunter88  
Also you might not want to forget, LPG cylinders are not designed for the liquid to be directly sprayed out of the connector port. Doing so could cause a build up of static electricity and ignite the propane. There have been many incidents in the past when flammable gas cylinders were allowed to vent, only to have it catch fire seconds later.


Any references for this?


I can't find the reference for LPG specifically anymore, but I remember seeing it somewhere. However I found this video by the CSB on propylene cylinders doing the same thing.

https://www.youtube.com/watch?v=-_ZLQkn7X-k


Oh, I have watched this video before, but I didn't remember that.

So, if the charge builds up, you also need something that will cause a discharge - what would that be? Anyways, I could still connect the valve to the earth.

xfusion44 - 14-10-2016 at 17:50

Quote: Originally posted by ave369  
Forget propane, use cryohol. Cryohol is made from ethanol and dry ice. Dry ice can be obtained from CO2 fire extinguishers. The temperature of cryohol is -79 C, which is more than enough to make liquid chlorine.


If I wanted to do it this way, I'd just buy a dry ice, instead of expensive fire extinguisher. I know about those cooling baths, but that'd be too easy ;)