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elementcollector1
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Making Chlorine
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?
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UnintentionalChaos
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Go read the prepublications forum.
[Edited on 11-25-12 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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elementcollector1
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...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.
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Magpie
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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."
The single most important condition for a successful synthesis is good mixing - Nicodem
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elementcollector1
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Brand names?
I know a guy who runs a pool, I'll see if he has any.
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Vargouille
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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".
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blogfast25
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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.
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AirCowPeaCock
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Absorption of Cl gas into the filter water is not a concern?
BOLD
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elementcollector1
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Not much Cl2 can dissolve into water.
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AndersHoveland
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I find the hypochlorite bleach with sodium bisulfate route most practical
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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ScienceSquirrel
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Use strong sodium hypochlorite solution (9 -12%) and hydrochloric acid, the reaction is rapid and facile.
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AirCowPeaCock
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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.
BOLD
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elementcollector1
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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.
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elementcollector1
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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]
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: reduced
image size(s)]
[Edited on 9.8.13 by bfesser]
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woelen
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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]
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MrHomeScientist
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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.
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tetrahedron
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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.
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MrHomeScientist
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@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 Cl<sub>2</sub> <b>liquid</b> 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]
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tetrahedron
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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:
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watson.fawkes
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Quote: Originally posted by MrHomeScientist  | | I'm not trying to store Cl<sub>2</sub> <b>liquid</b> 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.
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tetrahedron
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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]
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elementcollector1
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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?
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tetrahedron
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no, that's the melting point. the boiling point is in the -30s.
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elementcollector1
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...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.
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MrHomeScientist
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@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!
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