Sciencemadness Discussion Board - Preparation of Chlorine

Preparation of Chlorine

sirius_cm - 25-5-2003 at 16:45

Hey Guys,

Here is my question. Well, i'm an element collector, and I was wondering the best way of collecting rather pure Chlorine Gas. I know the electrolysis of Brine works, but is there a better way? Electrolysis of brine is fine for small quanities, but i want to fill a rather large bottle, well enough to tell that it is chlorine from the green/yellow vapor.

blip - 25-5-2003 at 18:19

Probably the easiest way is to combine MnO2 and HCl.

MnO2 + 4HCl --> MnCl2 + Cl2 + 2H2O

If you just happened to have CCl4 laying around, you could just burn it. ;-)

DDTea - 25-5-2003 at 20:02

Even easier than that is the well-known reaction between Sodium Hypochlorite Bleach and HCl... that's the way I've always made Chlorine, and it works just fine.

madscientist - 25-5-2003 at 20:17

I've found that Ca(OCl)2 + HCl works well.

[Edited on 26-5-2003 by madscientist]

a_bab - 25-5-2003 at 23:05

As being an element colector myself, I am planning to make liquid chorine in a glass tube. You can use chlorine hydrate in order to achieve this.

vulture - 26-5-2003 at 04:54

Chlorine hydrate?
Chlorine normally reacts directly with water:

Cl2 + H2O -> HCl + HOCl

a_bab - 26-5-2003 at 09:17

Actually, the hydrate is a cage around the chlorine atoms. Read here.

You need CaCl2 solution and chlorine to get the crystals.

sirius_cm - 26-5-2003 at 14:01

Quote:

Originally posted by blip
Probably the easiest way is to combine MnO2 and HCl.

MnO2 + 4HCl --> MnCl2 + Cl2 + 2H2O

If you just happened to have CCl4 laying around, you could just burn it. ;-)

Yes, I've used this method before. When I did it, i used about 20mL of Bleach (i believe 5%-7%) and 20% 20mL of Hydrochloric acid. Now when i mixed them, I did get bubbles, but not many of them. I want to get about .5 L of this stuff if possible, and this would require a bunch of these two chemicals. What are your thoughts?

And for the other reactions, are there any household equals to them? Calcium Hypochlorite and Manganese Oxide?

Just in case...

Rhadon - 26-5-2003 at 14:18

Quote:

If you just happened to have CCl4 laying around, you could just burn it. ;-)

Just in case someone really wants to try this: The thermal decomposition of CCl4 is known to yield highly toxic phosgene, so it might be wise to use another method instead.

Marvin - 27-5-2003 at 10:39

'Hydrate cage' sounds a bit insubstantial even if it is whats really going on. Cooling a strong solution of chlorine in water does produce crystals of chlorine hydrate, but the faraday method for a barely visible amount of liquid chlorine is likley to be as dissapointing as it is dangerous. Generally the tubes explode.

Electrolysis of salt with a high current produces chlorine of a concentration you can easily see in a small test tube in front of white paper.

sirius_cm - 27-5-2003 at 17:46

Quote:

Originally posted by Marvin
'Hydrate cage' sounds a bit insubstantial even if it is whats really going on. Cooling a strong solution of chlorine in water does produce crystals of chlorine hydrate, but the faraday method for a barely visible amount of liquid chlorine is likley to be as dissapointing as it is dangerous. Generally the tubes explode.

Electrolysis of salt with a high current produces chlorine of a concentration you can easily see in a small test tube in front of white paper.

On my last electrolysis of Brine, I think I had about 35 Volts of power running through my rig. I didnt think about the white paper. Now, how much in a reaction between bleach and hydrochloric acid are needed to start to see the good stuff?

a_bab - 28-5-2003 at 08:40

If you want to see the green color of the chlorine, you have to make it in copious amounts. Very simple to do with HCl+hydrogen peroxide mix, and Al. Use Al foil for better results.
I did it by accident and I saw the chlorine green clouds flowing down the table

sirius_cm - 28-5-2003 at 16:41

Quote:

Originally posted by a_bab
If you want to see the green color of the chlorine, you have to make it in copious amounts. Very simple to do with HCl+hydrogen peroxide mix, and Al. Use Al foil for better results.
I did it by accident and I saw the chlorine green clouds flowing down the table

Heh, thats interesting, thanks. Can you tell me though, why would this reaction yeild a yellow cloud, as the electryolsis of brine does not (in terms of amounts required to see the gas)?

DDTea - 28-5-2003 at 16:53

If you would not mind, could you try that reaction again, but without the Al? I don't see how it is needed, because the reaction between HCl and the Oxidizer (H2O2) should be enough to liberate Chlorine.

a_bab - 28-5-2003 at 22:37

Actually no. I used this mix to dissolve copper from electronoc plates. Without the H2O2, we all know that HCl is not able to dissolve copper, but mixed with H2O2 it does.

Be aware!

the timeless - 10-9-2003 at 01:10

See the concentrations first! If you do it with low-yield OTC´s it won´t make much chlorine, even if you use a 500ml batch. But if you use very pure and hot chemicals it will cause a vigorous reaction and a burst of chlorine as the batch shoots up a whistling shower of the remained liquid. You don´t have the time to do anything! I did this once by accident and it filled the whole house with chlorine. I could not assume this because all my previous low-concentration batches produced a very tiny amount of chlorine.

[Edited on 10-9-2003 by the timeless]

JustMe - 10-9-2003 at 11:57

If I were doing this, I would react Manganese Dioxide with Hydrochloric acid as has been already mentioned. (Mn02 is often available in hobby stores, HCl is Muriatic Acid, available at Hardware stores). Unfortunately, it creates wet chlorine.

Run it through a drying tube packed with Calcium Chloride (available at supermarkets as a dehumidifing agent), and condense it with a mixture of acetone (available at hardware stores as paint thinner) and dry ice (available at grocery stores) in a thermos.

Chlorine is viciously toxic... be careful!

[Edited on 10-9-2003 by JustMe]

Theoretic - 19-11-2003 at 09:20

Here's the catalytical cycle for using heat to conver CaCl2 + O2 to Ca(ClO)2 or CaO + Cl2.
1)CaCl2 + 2N2O4 => Ca(NO3)2 + 2NOCl
2)2Ca(NO3)2 => 2CaO + 2N2O4 + O2
3)2N2O4 + 2NOCl => 2N2O3 + Cl2
4)2N2O3 + O2 => 2N2O4
5)(optional) CaO + Cl2 + 2H2O => CaCl(ClO)*2H2O (water needed to wet the CaO that results from the original addition of water to make the reaction easier)
If you need it, SOP (standart operational procedure) is coming up tomorrow.
Have fun!

[Edited on 26-11-2003 by Theoretic]

Theoretic - 26-11-2003 at 02:47

OK, I shouldn't have posted the "have fun" bit, because then I would be assuming that the process is safe and easy, but anyway, here goes:

1)Place 111 g of CaCl2 in a 250-ml flask.

2)Place in an ice bath with a temperature lower than -6 C (to stop NOCl from escaping as a gas), but higher than -11C (to stop N2O4 from freezing).

3)Pour 368 g of N2O4 onto the CaCl2 and quickly cover with an inert liquid that would float on top (like petrol, vegetable oil or lubricating oil) to stop any gases evaporating off. Reaction 1 should be happening now (solvolysis). Reaction 2 may or may not be happening, so prepare to recieve chlorine anyway.

4)Irradiate with strong sunlight, which would decompose NOCl into NO and Cl2. Nitrogen monoxide would react with N2O4, but I don't trust the reaction going to completion, so use a slight excess of N2O4. Chlorine will escape. It's dry and pure. Any NOx that escaped with it (unlikely) can be captured with SO3, which reacts:
1)2NO + SO3 => (NO)2SO3
2)N2O4 + SO3 => (NO2)(NO)(SO4)
3)N2O3 + SO3 => (NO)2SO4.
The NOx can be regenerated by heating.

5)Now you have Ca(NO3)2, N2O3 and N2O4 left in your flask. Strongly heat to distill this over. Strong heating is needed to decompose Ca(NO3)2.

6)To regenerate N2O4, bubble O2.

I do have my doubts about strongly heating NOx with petrol on top, so you might want to remove that before you distilland reinstate the layer over NOx in its new location. This process is quite crude, and so it's more suited for making chlorine in quantities for chemical synthesis rather than for element collection. Again, like Catalytic chlorination, this seems too good to be true! Marvin, blast my theory to pieces, please, I tried but I can't. I don't sugest anyone tries this before someone else comments.

[Edited on 26-11-2003 by Theoretic]

Marvin - 26-11-2003 at 23:47

HahahahahahahaHAHAHAHAHAha.
hhaaahhahaaaahaaHHAahahaAHHHAAAAAHHAHA
AhahaAHAHAHahahaHAHAHAHAHAHAHAHA.
Muahahaahahahahah AHAHAHAHAHAHAHAHAHA.
HA!

By this point, you may have twigged that this is not looking good for the "Theoretic chlorine synthesis" (Patent pending). I would have great difficulty putting together a funnier parody synthesis myself, and Id give it to fellow chemists if I thought theyd 'get' it. I'm certain most undergraduates wouldnt.

"1)Place 111 g of CaCl2 in a 250-ml flask. "
The 250ml flask is too small for this experiment. Far too small. It wouldnt contain all the solid/liquid componants let alone have enough room for a reaction. This is not much of a problem though, compaired to what happens later and at least this step would work and so you only find out its wrong later.

"2)Place in an ice bath with a temperature lower than -6 C (to stop NOCl from escaping as a gas), but higher than -11C "
Ok, you are cooling a system a maximum of 5C below the boiling point of one of its componants and you are expecting it to have no vapour pressure, ie any gas liberated will be free of it. This is particully unlikley given the low molecular mass and poor intermolecular bonding.

Aside from this, we have the low availability of nitrogen tetroxide and its rather extreme toxicity. Few people would go neer using N2O4 for anything, and most of them are locked up for the protection of others.

"3)Pour 368 g of N2O4 onto the CaCl2 and quickly cover with an inert liquid that would float on top (like petrol, vegetable oil or lubricating oil) to stop any gases evaporating off. "
This is where it becomes obvios noone has ever actually tried this, becuase the amount of N2O4 we are being told to add exceeds the capacity of the flask we are being told to add it to, even if it didnt contain anything else, which it does. Having the highly toxic N2O4 fuming all over the place while we get a bigger flask would be considered 'bad', and then we move on to make things 'safer' by adding our 'inert' solvent.

This is where things go from bad to, well, downright abominable. Through good fortune or design liquid N2O4 is more dense than petrol, so things look fine up until the point we realise we cant cover the N2O4 with it because they are completely miscable. More importantly a mixture of petrol and N2O4 is a very shock sensitive high explosive, so at this point you have slightly less of a 'chlorine generator' and slightly more of a bomb.

"Chlorine will escape. It's dry and pure"
Sanity at this point has already fled, pale and shaking, while screaming obsenities down a mobile phone to lawyers4u. It is uncertain if any chlorine will actually be liberated by the setup, but if it does it certainly wont be pure. If its over 50% pure we'd be doing astonishingly well under the circumstances and bonus points for having any limbs left.

"I do have my doubts about strongly heating NOx with petrol on top, so you might want to remove that before you distilland reinstate the layer over NOx in its new location"
We'll be sure to remember.

"This process is quite crude, and so it's more suited for making chlorine in quantities for chemical synthesis"
Or possibly we should be doing this on a still much larger scale, lets all pick a city we dont like. The british are excluded from choosing a german city and vice versa, the americans are excluded from choosing a japanese city and vice versa and everyone apart from the french are excluded from choosing a french city. First to turn the chosen city into a smoking crater wins an extended stay in a luxury padded apartment with very high windows and a state of the art security system maintained by professionals. This offer is not open to minors, furthur terms and conditions apply and are available on request.

The question arises, "does it do what it says on the tin?". Almost certainly not, a complex mixture will probably form, evolving nitrogen oxides, chlorides and chlorine that would be completely useless to anyone not actually suffocating in it assuming that is, you actually get a reaction. SO3 is annoying to get hold of or make, as if N2O4 wasnt more annoying/difficult/toxic, and the method of recycling NO wouldnt work anyway without something like water to hydrolyse, though under most circumstances the salts do at least form.

Should anyone want chlorine by a catalytic oxidation method, I would suggest the CuCl2 regenerated by HCl/Air, or the permanganate/MnO2 process where the oxidising agent is regenerated by sodium or potassium nitrate,

Entertaining though these posts are, please stop this synthesis 'inventing'. You are rapidly moving from suggestions that simply wouldnt work for obvios reasons, to highly specific lists of instructions that would actually kill people that tried them.

Theoretic - 27-11-2003 at 05:56

Too bad... I edited it once for stochiometry when I realised that there was only half the required N2O4. I also realised the reaction vessel was too small, but that came too late...
"the amount of N2O4 we are being told to add exceeds the capacity of the flask we are being told to add it to"
It doesn't... ...just. The density of N2O4 is 1.51g/ml, so it would take up 242 ml (or it doen't matter anyway - as you say, there's more than N2O4 + room for reaction).
If the inert-layer method would have worked, no NOCl or NOx would escape below bp, since any evaporation would be hindered... ...but it doesn't, and it is my fault for proposing an inert layer that would dissolve in the reaction mixture and would lead to loss of limb and life. It looks like there isn't an inert compound for the layer that wouldn't dissolve in N2O4. Nitrogen tetroxide and SO3 are annoying/difficult...
I did intent for this to be a serious synthesis, but now I see my recipies don't work.
1)The inert-layer method doesn't work.
2)I make silly mistakes like not knowing flask capacity needed.
3)N2O4/SO3 are annoying/difficult/toxic...
OK, I'll stop concocting recipies.