Sciencemadness Discussion Board

Simple, cheap large scale chlorine generation

Dan Vizine - 9-4-2014 at 05:18

There are many ways to generate chlorine gas at home. Some use calcium hypochlorite and I have always found this to be exquisitely inconvenient for large scale generation because of the stirring (or should I say non-stirring?) issue/problem.

Chlorox gives chlorine when acidified. It's about 5% NaOCl. Swimming pool "shock" treatments are about 10% NaOCl.

My chlorine generator is a glass 5 gallon water cooler bottle. I think it was all of $10 or $11 dollars a few years back. Place a long cylindrical stir-bar in the bottom, place it on a sturdy magnetic stirrer and add 4 - 4 1/2 gallons of 5 - 10% NaOCl. The top is closed with a 2 hole rubber stopper. One hole has a provision for a 1 liter sep. funnel full of conc. HCL (the pool supply store is your friend) and the other is for Cl2 to exit.

Start dripping HCl into the stirred liquid. A few minutes pass while the generated Cl2 saturates the solution and it becomes green-yellow. When it becomes saturated, Cl2 begins to leave through the Cl2 exit tube. Refill the sep. funnel with HCl solution as necessary (before it runs out).

You can do the math to see how much Cl2 is possible. I didn't bother as I knew that I needed to simply keep the chlorine coming until the liquid refluxed at the right temperature. A rough statistic: I dichlorinated about 400 mL of xylenes with one generator containing 4 1/2 gal. 10% NaOCL.

After the reaction is done, feed the generator output outside while it finishes. The next day, (CAREFULLY) pour the solution into a large plastic bucket outside. Allow a day or two for Cl2 to escape and dispose of the residual brine solution down a drain.

The Cl2 can be dried using a conc. H2SO4 trap.

gdflp - 9-4-2014 at 05:46

Nice generator, I didn't realize that you could get conc HCl from a pool store. Also what are you using chlorinated xylene for?

thesmug - 9-4-2014 at 06:09

Where does he mention HCl from the pool store?

gdflp - 9-4-2014 at 06:13

Quote: Originally posted by Dan Vizine  
One hole has a provision for a 1 liter sep. funnel full of conc. HCL (the pool supply store is your friend) and the other is for Cl2 to exit.

thesmug - 9-4-2014 at 06:14

Sorry, didn't notice that!

Dan Vizine - 9-4-2014 at 06:37

The pool store is the best supplier for conc. HCl at low cost. It isn't quite as concentrated as normal commercial reagent grade but quite close (within a few %). Also it's the the best place for 10% NaOCl and bulk NaHCO3.

(also, FYI, Lowe's is the local place to find NaOH (drain cleaner. RIP Red Devil Lye). Hardware stores and similar often stock conc. H2SO4 for about $11/liter (also as drain cleaner/opener)).

The bis(chloromethyl)benzenes were made a few years back on a contract basis for a customer I initially met on eBay. Actually, 1.4- bis(chloromethyl)benzene was the original request but I didn't have a convenient source for p-xylene so he settled for a mixture at reduced cost which he said he'd purify. I don't know the purpose (exactly) but the terminology he used made me think it was being used as a cross-linker or for some other similar, polymer-related work. This material has no known drug or explosive connection that I'm aware of, so I didn't need to pry into motives too much.



[Edited on 9-4-2014 by Dan Vizine]

Zyklon-A - 9-4-2014 at 07:24

Electrolysis of NaCl in solution is the cheapest way to make it chlorine on the large scale.

gdflp - 9-4-2014 at 08:03

One problem is, that method is rather slow so you have to have a way of storing chlorine. Also, won't most of the chlorine produced dissolve in the hydroxide to produce hypochlorite? Although, I guess you could get around this by placing the cathode near the top of the solution and the anode at the bottom.

Bert - 9-4-2014 at 08:11

Quote: Originally posted by Zyklonb  
Electrolysis of NaCl in solution is the cheapest way to make it chlorine on the large scale.


If one has a good sized DC power supply and the materials already? That's certainly possible. You have done this? If so, you should post your lab notes here, so others may learn. Of course, with the links or citation of other materials you learned from.

------------

My questions-

Did you use a pressure equalizing addition funnel for the hydrochloride acid?



If using H2SO4 dryer inline, bubbled through the acid, or merely passed over?


Zyklon-A - 9-4-2014 at 08:44

Quote: Originally posted by Bert  
Quote: Originally posted by Zyklonb  
Electrolysis of NaCl in solution is the cheapest way to make it chlorine on the large scale.


If one has a good sized DC power supply and the materials already? That's certainly possible. You have done this? If so, you should post your lab notes here, so others may learn. Of course, with the links or citation of other materials you learned from.

I did make some with this method, yes. But only as a byproduct of a sodium hydroxide producing cell. I did use some of the produced the chlorine, but most I simply scrubbed out. I didn't need large amounts of it at the time. I did not quantitatively test the purity, nor did I dehydrate it, as I had no real use for it at the time.
I believe I used this set-up. I still have everything put-together, so I could try it again, but this time, intentionally for the chlorine, and making NaOH as a byproduct. I can't remember what voltage or amperage I used, but I'm sure it was not the best. I will test thest some more later.

Bert - 9-4-2014 at 09:01

Quote: Originally posted by Zyklonb  

I could try it again, but this time, intentionally for the chlorine, and making NaOH as a byproduct. I can't remember what voltage or amperage I used, but I'm sure it was not the best. I will test thest some more later.


Two thoughts: ALWAYS TAKE NOTES. It REALLY helps down the road-

And do you know enough electrochemistry to work out just how much electric power it takes to electrolyze a mol of Cl2? Would your long term interest be better served by learning some theory, or in an experiment...

See problem example #2 here:

You might need a bigger power supply?

Your parents might be surprised at the electric bill?

[Edited on 9-4-2014 by Bert]

Dan Vizine - 9-4-2014 at 10:07

Hi Bert,

Your questions-

Did you use a pressure equalizing addition funnel for the hydrochloride acid?
No, I don't have one as large as a liter. I used a sep. funnel with a tiny strip of paper towel in the stopper hole, along side the stopper. The addition rate is slow (controlled by how fast my chlorination would consume it) so this minute leak lets enough air in. The HCl layer seals the chlorine inside. If left unattended, make sure there is always HCl in the funnel or chlorine escapes here rather than push through H2SO4 and chlorination mixture.


If using H2SO4 dryer inline, bubbled through the acid, or merely passed over?
Passed over it? I would never consider this adequate. It was bubbled through a column of acid about 4 - 5 inches deep (use suck-back trap).

[Edited on 9-4-2014 by Dan Vizine]

elementcollector1 - 9-4-2014 at 10:09

Don't produce chlorine from electrolysis. It sucks to capture it, and it's so contaminated with oxygen as to be not worth it (Up to 10%, if the thread in PrePub is to be believed).

Personally, for producing chlorine, I prefer battery paste (MnO2) or bleach and HCl.

Zyklon-A - 9-4-2014 at 10:10

Yes, I have been taking notes for some time now, I often look back at my earlier work, and regret not taking notes.
I will spend some time working out the math, and getting a better understanding of electrochemistry. I currently do not know exactly how to find out, but the link you provided, was very helpful.

I definitely need a new power supply, At the moment, what I've been doing is hooking up small PSU's in parallel to achieve higher amps, and in series to achieve higher volts.
Correct me if I'm wrong, but it looks like I'll need a total of 5.29 volts for the whole reaction. Is this right?
I will start off with very low amps, (in the order of 5-10 amps) so I doubt the electric bill will be very dramatically increased.

AJKOER - 9-4-2014 at 10:40

Here is a path to Cl2 I have discussed previously and performed on many occasions, namely create a so called Bleach battery. This would qualify as cheap and simple if you has some spare chlorine bleach around, copper (new US pennies are pure Cu plate), vinegar and Aluminum foil. One can also produce some electricity as well.

Steps:

1. Whip up some Hypochlorous acid by mixing bleach (NaOCl) and vinegar (which contains Acetic acid HAc) in the volume ratio 1.4 parts of 5% vinegar to one part of 8.25% extra strength chlorine bleach.

2. To the HOCl add a piece of copper metal which will function as the cathode and an Aluminum source to act as the anode (finely cut up Al foil, for example, will also work).

3. Lastly, add a little (or perhaps more, see discussion below) salt to act as the electrolyte to get things started.

My take on the chemistry:

The creation of Hypochlorous acid:

NaOCl + HAc --> HOCl + NaAC

And, on the major electrochemical reactions:

6 H2O <--> 3 H3O+ + 3 OH-

At anode:

Al + 3OH- ⇒ Al(OH)3 + 3 e-

At the cathode (copper):

3 HOCl + 3 H3O+ + 3 e- ⇒ 3/2 Cl2(g) + 6 H2O

for an implied net reaction of:

3 HOCl + Al --> Al(OH)3 (s) + 3/2 Cl2 (g) Eo net = 3.93 V

This battery cell is theoretically capable of generating 3.93 volts.

Reference: see http://www.exo.net/~pauld/saltwater/ and http://sci-toys.com/scitoys/scitoys/echem/batteries/batterie... and also http://www.dtic.mil/dtic/tr/fulltext/u2/d019917.pdf

There are also many side reactions. One with respect to increased chlorine production of interest is that with an excess of chloride, a possible competing reaction to the cathode reaction which consumes Hypochlorous acid and hydronium ions, and can enhance the chlorine yield:

HOCl + H3O+ + Cl- ⇒ Cl2 (g) + 2 H2O

The general nature of chlorine generation is nearly nill at the beginning (an induction period) followed by a consistent Cl2 generation. This is actually favorable for 'large scale' as one is given time to close and adequately seal (or move) the Cl2 generator. This is a potential issue with the hypochlorite/HCl method which is rapid (IMHO, possibly inviting an accident on a large scale).

[Edited on 9-4-2014 by AJKOER]

aga - 9-4-2014 at 12:30

Quote: Originally posted by Zyklonb  
At the moment, what I've been doing is hooking up small PSU's in parallel to achieve higher amps, and in series to achieve higher volts.
Correct me if I'm wrong, but it looks like I'll need a total of 5.29 volts for the whole reaction. Is this right?
I will start off with very low amps, (in the order of 5-10 amps) so I doubt the electric bill will be very dramatically increased.


I find PC tower type PSUs perfect for everything.
You get 5v at 30 Amps
12v at (about) 10 Amps and they're cheap and rugged.

I think the one use was found in a discarded PC tower case in a bin, but they are dirt cheap on ebay too.

You just need to short out one of the pins to ground to get it to run.
I will go get mine and see which pin it is.

aga - 9-4-2014 at 12:41

Just checked my PC power supply.

The big connector has 20 pins, in two rows of 10.
if you look Into that connector, with the latch-clip at the top, then you need to short the pin that is 4th from the Left, top row, to the 5th from the left, top row. That makes it run. Un-short and it stops.
The pin on the left, bottom is the only square pin.

The outputs on the Other leads (4-pin connectors) are +5V @ 30 Amps on the red wires, and +12V @ 15 Amps on the yellow wires, with 0V on the black wires.

You can also find +3.3V @ 20 Amps on the 20-pin connector if you have a voltmeter.

That's my power supply salvaged from the bin.

Your mileage will probably vary (likely you'll get more Amps from yours)