Sciencemadness Discussion Board - Making Chlorine

Making Chlorine

elementcollector1 - 24-11-2012 at 18:44

Let's start off with this: I most certainly do *not* want to kill myself or anyone else with any chlorine produced. I *do* first want to seal some in an ampoule for my element collection, and second want to have a general method of manufacture for the stuff in case I need chlorine for a reaction.

Disclaimer over, on to the science.

So far, I've amassed a few methods of making chlorine gas:
-MnO2 + HCl - Produces chlorine rapidly if in large quantities, not too efficient in terms of chlorine (an equal amount goes into MnCl2 that goes into gas).
-NaOCl / Ca(OCl)2 + HCl - Haven't tried this yet, don't know about the rapidity of the reaction. Any thoughts, anyone?

UnintentionalChaos - 24-11-2012 at 19:21

Go read the prepublications forum.

[Edited on 11-25-12 by UnintentionalChaos]

elementcollector1 - 24-11-2012 at 20:33

...Well, that was convenient.

What about NaOCl + HCl? I'd assume it would have similar characteristics to the Ca(OCl)2 + HCl reaction discussed in the thread, but bleach is far easier to come by than calcium hypochlorite.

Magpie - 24-11-2012 at 20:44

from Len1's method in the Prepublication:

"A much forgotten post by Organikum (practical method to chlorine, an outflow from the chlorine thread) suggested the use of Trichloroisocyanuric acid C3N3O3Cl3, a chemical ubiquosuly availabale as a pool chlorinator together with HCl as a means of producing Cl2 without the piggyback O2 impurity which the other common chlorinator, hypochlorite bleach, is purported to produce."

elementcollector1 - 24-11-2012 at 20:48

Brand names?
I know a guy who runs a pool, I'll see if he has any.

Vargouille - 25-11-2012 at 04:06

The only brand name that I've seen is "Value Chlor", but they're sold as "Chlorine tabs", "Chlorinating tablets", or "Trichlor" in most other cases. The chlorinating tablets are typically quite large, with a diameter of either 3" or 1". Apparently they may be sold as "Symclosene", but I've never seen it labeled as such. It may not be labeled as "trichloroisocyanuric acid", as most tubs of the stuff I've seen say "trichloro-s-triazinetrione".

blogfast25 - 25-11-2012 at 07:23

If your purpose is to fill up a small ampoule for display, then using the black, manganese oxide(s) containing dry battery electrolyte from spent batteries plus HCl is probably the cheapest route. It does tend to foam quite a bit. Wash the chlorine by bubbling through water to absorb the extra HCl, then dry it.

AirCowPeaCock - 25-11-2012 at 09:17

Absorption of Cl gas into the filter water is not a concern?

elementcollector1 - 25-11-2012 at 09:52

Not much Cl2 can dissolve into water.

AndersHoveland - 26-11-2012 at 03:50

I find the hypochlorite bleach with sodium bisulfate route most practical

ScienceSquirrel - 26-11-2012 at 04:30

Use strong sodium hypochlorite solution (9 -12%) and hydrochloric acid, the reaction is rapid and facile.

AirCowPeaCock - 26-11-2012 at 11:09

According to wiki 1 L of water disolves 1.125 L of chlorine, I have read similar things other places. Certainly no compairison to HCl, but certainly significant. Especially of trying to collect just a small amount of chlorine for display.

elementcollector1 - 26-11-2012 at 11:15

So, when the solution is saturated with chlorine, no more will dissolve, and the chlorine bubbled through will be led through a drying tube into the desired ampoule.
I think I'm going to go with hypochlorite and HCl, seems the cheapest route.

elementcollector1 - 28-11-2012 at 20:23

Well, quick update: I now have an ampoule with the absolute faintest tinge of green when placed against a white background. I don't think that this is nearly as concentrated as I'd like it to be, but considering it's electrolytic chlorine and not chemically produced, it's alright. My question is: How visible is chlorine gas on a white background?
EDIT: pictures attached

<img src="http://25.media.tumblr.com/tumblr_me8f8pKNwq1ri4na2o1_1280.jpg" width="600" />
[Edited on 29-11-2012 by elementcollector1]

[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: reduced image size(s)]

[Edited on 9.8.13 by bfesser]

woelen - 28-11-2012 at 23:33

Yours is very dilute. Have a look at the wikipedia page about chlorine. That page shows a glass ampoule of 20 ml, which I have made myself. I made my chlorine with calcium hypochlorite, to which I added dilute HCl. I collected the gas in a 200 ml bottle with a narrow top. I then sucked the chlorine in a syringe of 60 ml in which I had a mix of anhydrous CaCl2 and P4O10 and swirled the mix somewhat. I kept the chlorine in that syringe for several minutes and then blew all of it in the 20 ml ampoule and immediately sealed that with a hot flame.

I think that the chlorine in that ampoule is somewhere around 90%, the rest is air. It nicely shows the green color of the gas.

The gas must be meticulously dried. If you fail to do so, then you get condensed water at some spots on the inside of your sample and that really spoils the ampule. Hence the use of P4O10, combined with CaCl2.

Did you make the chlorine by means of electrolysis? That is not a very good way of making pure chlorine. My experience is that quite a lot of oxygen is made as well (maybe even 10% or so). The production of chlorine is slow and while colelcting it under water, a considerable amount dissolves in the water, while the oxygen does not dissolve. This dilutes the chlorine. As a young boy I tried to make chlorine in this way and I found that more than three out of four parts dissolved in the water. If you then have a mix of 10% oxygen and 90% chlorine and three quarters of that gas mix dissolves in water, then the remaining gas mix is almost half oxygen. Transferring it to a vial add more dilution and you understand that using this method results in weak samples.

[Edited on 29-11-12 by woelen]

MrHomeScientist - 29-11-2012 at 06:36

Some time ago I made a very small amount of liquified chlorine, my plan being to transfer this to an ampoule for display. I didn't have everything cold enough though so it all boiled away before I was able to get it ampouled. The plan was to only add about 1 mL or so of the liquid, let the majority of it boil off, then seal the ampoule. That way I should have a pretty concentrated sample of the gas that should be easily seen. Anyone see any problems with this? Pressure shouldn't be too high since I'm letting just about all the liquid boil off before sealing. I had wondered if the ampoule would shatter from the temperature difference between the cold bottom and hot top though.

tetrahedron - 29-11-2012 at 08:17

Quote: Originally posted by MrHomeScientist

Pressure shouldn't be too high since I'm letting just about all the liquid boil off before sealing.

the pressure should be the same whether the ampoule is nearly full or nearly empty, just like the concentration of a saturated solution is the same whether there's little or a lot solid solute in contact with it.

MrHomeScientist - 29-11-2012 at 09:53

@tetrahedron:
I understand what you're saying, but here is a little different I think. If, say, I filled the ampoule completely with liquid chlorine and sealed it, upon warming up to room temperature all that liquid would boil into gas, increasing the pressure inside the ampoule dramatically and probably leading to failure. If, on the other hand, I only add a small amount of liquid, let it boil enough to push any air out, then seal the ampoule while there is still a small amount of liquid left, then upon warming to room temperature this would only add a small amount of pressure to the container when it boiled off. Less liquid chlorine added initially means less final pressure once the container has warmed back up.

Edit: For clarification, I'm not trying to store Cl2 liquid in the ampoule - just a gas concentrated enough where it is easy to see. The liquid step is only to ensure lots of chlorine is present, and a pressure slightly greater than atmospheric within (again, so that the gas is nice and visible). I can see that I wasn't very clear on what I was trying to do.

[Edited on 11-29-2012 by MrHomeScientist]

tetrahedron - 29-11-2012 at 10:23

granted, if the amount of liquid is small enough, then all of it can evaporate before establishing its full vapor pressure. but consider that a microliter of liquid Cl₂ evaporates to about 0.5mL of gas at room temperature and thus adds about 1/2 atm to a 1mL ampoule.

chlorine vapor pressure:

watson.fawkes - 29-11-2012 at 11:38

Quote: Originally posted by MrHomeScientist

I'm not trying to store Cl2 liquid in the ampoule - just a gas concentrated enough where it is easy to see. The liquid step is only to ensure lots of chlorine is present, and a pressure slightly greater than atmospheric within (again, so that the gas is nice and visible).

From the graph tetrahedron posted, the vapor pressure at 300 K (canonical room temperature) is about 8 bar. That's the highest possible pressure for chlorine vapor at room temperature. If there's more chlorine than that in the vessel, it will condense and liquify.

If you want a chlorine vapor demonstration ampoule, then, I'd recommend ensuring there's a drop of chlorine in it. 8 bar is well within the pressure tolerances of standard borosilicate glass, at least at small diameters. If you want larger diameters, medium wall and heavy wall tubing is also available. I won't recommend actual dimensions here, because I don't have a reference handy, and I do recommend looking up the engineering data in this case.

The advantage of a small amount of liquid chlorine is that you'll ensure the amount of gaseous chlorine is as large as possible. This is directly related to the reason there's a tiny drop of mercury in many fluorescent bulb, to ensure maximal vapor pressure. You only need the smallest drop that remains liquid, maybe several μL. The temperature gradient during fabrication can be fairly modest in this case, because while the temperature difference remains large, if the tube is long enough, the gradient is manageable. In addition, there's nothing saying that the liquid chlorine needs to be in thermal equilibrium at the bottom of the glass. It can be evaporating off as you seal the ampoule.

tetrahedron - 29-11-2012 at 11:47

OTOH if the aim is storing chlorine in any form then go all the way and fill your ampoule, if it can manage 8 atm. the only danger is if it breaks, the impact will be greater.

[Edited on 29-11-2012 by tetrahedron]

elementcollector1 - 29-11-2012 at 11:47

MrHomeScientist, I'm interested in your liquid chlorine. Chlorine condenses at -101.5 C, which is significantly below the temperature of dry ice (solid carbon dioxide) at -78 C. So what did you use to liquefy your chlorine?

tetrahedron - 29-11-2012 at 11:50

Quote: Originally posted by elementcollector1

Chlorine condenses at -101.5 C

no, that's the melting point. the boiling point is in the -30s.

elementcollector1 - 29-11-2012 at 12:03

Quote: Originally posted by tetrahedron

Quote: Originally posted by elementcollector1

Chlorine condenses at -101.5 C

no, that's the melting point. the boiling point is in the -30s.

...Right.
Feeling pretty stupid right about now...
Anyway, in that case, dry ice should work perfectly. I went onto Amazing Rust in the meantime and found that they used a mixture of ethanol and dry ice to cool the chlorine to it's liquid state. http://www.amazingrust.com/Experiments/how_to/Liquid_Cl2.htm...
My only question here is, how did the container containing the dry ice/ethanol mix withstand the temperature? It doesn't look like borosilicate, so unless ordinary soda-lime glass is significantly stronger than I thought, I would expect the container to shatter. Not fun.
Incidentally, would it be possible to set up an actual 'condenser' with this mix instead of placing a flask in a bowl? I would think a cold finger or something would work more ideally in this situation, but I don't think I can build one.

MrHomeScientist - 29-11-2012 at 12:43

@elementcollector1:
Indeed, that's actually where I got the idea to try it myself. I used dry ice and acetone in a beaker, into which the receiver RBF of my gas generator setup was immersed. I only had a little dry ice left from something else I was using it for, so I suspect that's why mine didn't work out so well (not enough cooling). If you scroll down to the bottom of the Amazing Rust page, you see he actually uses a styrofoam container to hold his cooling liquid rather than the bowl in the illustration. That would seem ideal (but of course, then you couldn't use acetone).

@tetrahedron & watson.fawkes:
Thanks for the great graph and advice. The ampoules I have are this type (though mine aren't amber):

Would those really hold enough pressure to keep chlorine liquid? I thought they were too thin-walled for that. The only samples of liquid Cl2 I've seen are tiny glass tubes imbedded in plastic resin, which I assumed was to contain the pressure but I suppose may have been for safety reasons. I'd certainly be worried about handling a pressurized fragile ampoule full of liquid Cl2!

tetrahedron - 29-11-2012 at 13:30

Quote: Originally posted by elementcollector1

how did the container containing the dry ice/ethanol mix withstand the temperature? It doesn't look like borosilicate, so unless ordinary soda-lime glass is significantly stronger than I thought, I would expect the container to shatter.

just being at a certain temperature doesn't cause thermal shock, it's the rapid change that does. after adding the dry ice, the ethanol takes a while to cool, so it provides a sort of heat buffer in the meantime. also, the relatively hot gas doesn't carry enough heat to cause a dangerous shock. consider it a sort of distillation, just carried out at room temperature rather than at the boiling point of water/ethanol/...

watson.fawkes - 29-11-2012 at 14:34

Quote: Originally posted by MrHomeScientist

Would those really hold enough pressure to keep chlorine liquid? I thought they were too thin-walled for that.

Those are preformed ampoules. An ampoule as such doesn't need to be preformed. Many of the pre-formed ones are flint glass, as borosilicate would be overkill. I mentioned borosilicate because it's much easier to find dimensional tubing in borosilicate rather than flint glass.

The short answer to your question is that I don't know. 8 bar is only about 120 psi, though. That's well within the range of a typical shop compressor. So test one to destruction with compressor air. Make jig, clamp on a hose, and use stops to prevent the ampoule becoming a bullet. Bring it up to pressure behind a blast shield. If it's not broken yet, tap on it and see if it breaks.

tetrahedron - 29-11-2012 at 15:01

..or store it in the freezer (<2 bar should be manageable). any leak will help preserve your food ;p

elementcollector1 - 29-11-2012 at 16:56

Quote: Originally posted by tetrahedron

..or store it in the freezer (<2 bar should be manageable). any leak will help preserve your food ;p

...I'd rather not.
I use disposable glass pipettes as ampoules, instead of those official things.
So, once I've put in a minimal amount of liquid chlorine into my ampoule and sealed it, anything fun to do with the rest?

tetrahedron - 30-11-2012 at 00:44

Quote: Originally posted by elementcollector1

anything fun to do with the rest?

i'd make some anhydrous metal chlorides with it.

MrHomeScientist - 30-11-2012 at 06:28

Quote: Originally posted by watson.fawkes

I do have some tiny test tubes I have used as ampoules before, but I'm not sure if those are borosilicate. I don't suppose there's any way to tell? They are pretty thin-walled though. I think in the end if I want to store the liquid for display I'll cast the ampoule in resin - that's how I've seen some display samples of bromine sold and it would let me sleep better at night I think

In the meantime I'll proceed with my original plan to ampoule only the gas. Woelen's method sounded pretty good too.

The pressure test is a very interesting idea, as long as all those safety measures are in place. It would probably be a good idea to put the whole thing in a box too so I don't end up with glass shards everywhere. That would make an exciting video too I think!

elementcollector1 - 30-11-2012 at 08:55

Quote: Originally posted by tetrahedron

Quote: Originally posted by elementcollector1

anything fun to do with the rest?

i'd make some anhydrous metal chlorides with it.

Sounds fun, how do I start? I'd probably have a flask of liquid chlorine, leading to a flask of a metal, allow the liquid chlorine to warm up to room temperature...
I seem to have noticed that if you look at the 'lip' of the glass, borosilicate and soda-lime seem to be different colors. Soda-glass seems to be more blue, and borosilicate closer to yellow or yellow-green. This may be something else, however.

HCl Electrolysis

I Like Dots - 21-3-2014 at 08:25

Lately i've been looking for a way to produce chlorine gas that I could start and stop at will.

I settled on electrolysis of HCl, as it has a long term reliable output.
Im using graphite anodes, and a old computer powersupply. My anode surface area is 4in². The power supply outputs 12A @ 3v, 12A @ 5v and 16A at 12v. So a current density of 3-4A/in² Ive been experimenting with different voltages, the largest production is at 12v, 3v and 5v visually produce the roughly the same amount of gas. I think with increasing voltages more side reactions are likely to occur (More O₂ production, higher anode erosion-likely CO and CO₂).

I have a few questions though. There must be some oxygen produced as well as chlorine right? What conditions favor chlorine production? Is it possible free chlorine is combining with the carbon, or carbon-oxygen compounds forming things like CCL₄, or Phosgene?

macckone - 21-3-2014 at 09:16

Quote: Originally posted by I Like Dots

Lately i've been looking for a way to produce chlorine gas that I could start and stop at will.

I settled on electrolysis of HCl, as it has a long term reliable output.
Im using graphite anodes, and a old computer powersupply. My anode surface area is 4in². The power supply outputs 12A @ 3v, 12A @ 5v and 16A at 12v. So a current density of 3-4A/in² Ive been experimenting with different voltages, the largest production is at 12v, 3v and 5v visually produce the roughly the same amount of gas. I think with increasing voltages more side reactions are likely to occur (More O₂ production, higher anode erosion-likely CO and CO₂).

I have a few questions though. There must be some oxygen produced as well as chlorine right? What conditions favor chlorine production? Is it possible free chlorine is combining with the carbon, or carbon-oxygen compounds forming things like CCL₄, or Phosgene?

First instead of precious HCl why not use more readily available NaCl
and acetic acid to keep the pH low. Some oxygen is generally produced.
Chlorine production is favored by low pH among other things like
electrode material. Yes, the carbon will react with the chlorine slowly
destroying your electrode. The side products are going to depend a
lot on your current density and the density of your electrode.

Mailinmypocket - 21-3-2014 at 09:26

A two neck flask... Crushed TCCA in the flask, a pressure equalized addition funnel with 15% or so HCl in one neck, and in the other neck a take off adapter with tube going to wherever you want the chlorine. Just add the HCl and stop adding it to stop generating chlorine.

MrHomeScientist - 21-3-2014 at 11:40

A [url=http://en.wikipedia.org/wiki/Kipp's_apparatus]Kipp generator[/url] is also a nifty way to generate gases on-demand. The page conveniently mentions a method for chlorine with the device - HCl and MnO₂ or KMnO₄.

[Edited on 3-21-2014 by MrHomeScientist]

Hrm, suddenly url tags don't work?

[Edited on 3-21-2014 by MrHomeScientist]

Refinery - 21-3-2014 at 14:03

Quote: Originally posted by macckone

Does this really work to produce chlorine? I can obtain 10% acetic acid solution, which I could saturate with NaCl. Obviously this would form sodium acetate as a byproduct.

elementcollector1 - 21-3-2014 at 14:38

It does, but the product is contaminated with oxygen.

Refinery - 21-3-2014 at 15:03

Well it doesn't matter in my case.

I think Im gonna test this ASAP and post results. I'm gonna need to reinstall my graphite electrodes though, it'll take some time.

Oh by the way, is the oxygen produced in the cathode compartment? Because I can separate the electrodes by encapsulating them into separate floating tubes.

elementcollector1 - 21-3-2014 at 15:19

Nope, anode along with the chlorine. Hydrogen is produced at the cathode.

Panache - 21-3-2014 at 16:41

Quote: Originally posted by Mailinmypocket

A two neck flask... Crushed TCCA in the flask, a pressure equalized addition funnel with 15% or so HCl in one neck, and in the other neck a take off adapter with tube going to wherever you want the chlorine. Just add the HCl and stop adding it to stop generating chlorine.

It really needs to not be more complex than this, in fact if you're just collecting the gas for display or on a cold finger a plain addition funnel is fine. I know people don't like reading but len1 also showed that with this method the cacl2 drying tub was redundant.
Likewise I have a post somewhere where I prepared some 500ml of liquid cl2 then transferred this to Lecture bottle.

I Like Dots - 21-3-2014 at 17:44

Quote: Originally posted by Panache

I prepared some 500ml of liquid cl2 then transferred this to Lecture bottle.

Now that's neat.

As far as HCl electrolysis, I am also interested in the possibility of insitu chlorination. Ex: ethanol / acetone.

Metacelsus - 22-3-2014 at 04:37

I tried acetone. I couldn't get it to work very well, due to tar formation.

http://www.sciencemadness.org/talk/viewthread.php?tid=936&am...

However, my cell was pretty crude, as were my reagents (hardware store grade).

[Edited on 22-3-2014 by Cheddite Cheese]

j_sum1 - 20-10-2014 at 04:45

Nice to have a forum search engine.

I was debating with myself the relative merits of various methods for creating chlorine --
I have previously done KMnO4 + HCl
I have also done HCl and laundry bleach.
I was curious which was better -- to use HCl and Ca(OCl)2 or HCl and TCCA.

I also had some questions about both vapour and liquid ampouling. Pretty much everything answered here.

I have decided to go for the HCl and TCCA route on the basis that the product is not going to be contaminated with O2 and also because it is less likely to need drying. Can someone confirm that I have this correct?