synthesising hypochlorite ions

[hermanntrude]

I want to make some sodium or calcium hypochlorite to do a luminescense demo with hydrogen peroxide. I've found out you can simply take NaOH and bubble chlorine through it and you get a mixture of HCl and NaOCl. this would be fine but I don't want the HCl, since mixing it with H2O2 is bound to give badness... perhaps I could bubble Chlorine through NaOH and then neutralise the solution with more NaOH? or just stop the reaction when it's neutral?

[YT2095]

take NaOH and bubble chlorine through it and you get a mixture of NaCl and NaOCl.

 

would have been better

 

excess Cl2 would give you the HCl and chlorous acid after, although for NaOCl to remain stable you need NaOH in excess (it has to be a basic soln)

can`t you just use TCCA or NaDCCA with your peroxide? it gives a Red glow.

[big314mp]

Is there any reason you can't use bleach or pool shock treatment?

[YT2095]

normal "bleach" is only about 5% at best, you can get up to 12% making it yourself.

the Pool shock stuff should work though

[hermanntrude]

I'd just rather use the stuff I have in the stores. Ive got chlorine and NaOH, but no swimming pool bleach

 

apparently the reaction with hypochlorite is rather faster than that with the swimming pool stuff. Assuming it's not too violent it'll probably provide quite a bright flash

[YT2095]

do it in a darkened room and allow time for your eyes to adjust, I`m pretty sure the color will be Red and not very bright or particularly long lasting.

[hermanntrude]

do you think there'll be any difference between hypochlorites with different cations?

 

how would I know when to stop bubbling chlorine? when I reach a certain pH? perhaps 8 to avoid losing the basicity? Can I then just add the H2O2 or will the NaCl and/or other impurities cause the luminescence to not happen?

[YT2095]

I`m really not sure about the cations affecting the color and I have no idea if NaCl or other impurities will prevent the reaction, although I can`t imagine NaCl doing anything of significance.

 

the way I made my NaOCl was to pass Cl2 gas through NaOH soln as tiny bubbles, and the vented gas was passed through a scrubber with indicator soln in it, when Cl2 was no longer reacting with the NaOH soln he color changed, and at that point I stopped and added a little extra NaOH to the soln for stability.

I will point out that IF you decide to store this, do it in a suitable container and don`t put the lid on tightly for a few days, there is quite a bit of off gassing for a while before it finally settles to a storable reagent.

even then be careful taking off the cap, as some Cl2 will escape if it`s been left standing for a while and can catch you by surprise, there doesn`t need to be a lot of Cl2 in the air to be Very unpleasant!

 

the best way to find out is to try it and then let us know how if it worked out or not, I genuinely don`t know the answer to some of your questions.

[hermanntrude]

I wonder if there's a method by which I dont have to bother actually isolating the NaOCl... perhaps I can just bubble some chlorine through NaOH and then add some H2O2

[jdurg]

If you're going to make Cl2 anyway, why not just get your singlet oxygen in that regard? The most visible emission of light happens with chlorine gas bubbled through a strongly basic solution of concentrated H2O2. (You can use concentrated ammonia, or what's probably better is concentrated NaOH, to make it basic). The red light given off is most intense when done in this fashion.

[hermanntrude]

not gonna make the chlorine. I have a lecture bottle full of the stuff.

 

The idea of bubbling it directly through h2o2 never occurred to me... thanks for the idea... awesome.

 

congratulations on your up-coming 2000th post

[jdurg]

If you've got a lecture bottle full of the stuff, then yeah, just go with that route. It will be SUPER easy to show off singlet oxygen. You just have to make sure that the H2O2 is very basic before you do this. So add plenty of NaOH to the 35% H2O2 and bubble the Cl2 into there. I had always done it by using ammonia, but after seeing it done just as easily with NaOH, I'd say go that route. NaOH is very easy to come by and doesn't have the nasty smell that NH3 does. Plus, you don't have to worry about the formation of NH4Cl from any HCl and NH3 vapors in the air.

 

So just go and get some NaOH, dissolve it in some H2O2, then bubble Cl2 into it. You'll see a pretty neat glowing reaction.

 

 

 

 

 

 

(Never realized I was close to 2,000 posts. Means I've had far too much free time in the past four years. )

[John Cuthber]

Chlorinating ammonia is a bad idea.

http://en.wikipedia.org/wiki/Nitrogen_trichloride

[jdurg]

In my experience, no NCl3 was formed since the H2O2 and evolution of oxygen quickly oxidized everything into various oxychlorides. But NaOH is a much easier method and less stinky.

[jrayj]

THanks to jdurg:

It's pretty simple. You need to have fairly concentrated Hydrogen Peroxide (H2O2) with some concentrated ammonia solution mixed in. Do this very carefully to ensure there's no rapid decomposition of the H2O2.

 

Put this mixture into a tall graduated cylinder. In a separate flask with a one-holed stopper, put some concentrated calcium hypochlorite solution and slowly add concentrated HCl to it. This will start generating chlorine gas. The stopper should have a glass tube coming out of it with the other end under the surface of the H2O2/NH3 mixture. Once you've got the HCl added, put the stopper on.

 

The Cl2 generator should be setup at a higher level than the graduated cylinder as Cl2 is much denser than air so this will cause it to flow out the glass tube into the H2O2/NH3 cylinder. As the chlorine enters the graduated cylinder, it will cause the decomposition of the H2O2 and it will form exicted (singlet) oxygen which will glow red.

 

Just make sure this is done in a well ventilated area as the Cl2 and NH3 are pretty nasty stuff.

[hermanntrude]

OK so i plan to do this exactly as jrayj describes, except that since I have chlorine but no hypochlorites, I'll just use my lecture bottle for the chlorine source.

 

Several times people have suggested that there is a danger of a sudden decomposition of H2O2, what can I do to minimise the risk?

[John Cuthber]

Make sure that the container it is in is big enough to contain the foaming.

 

Also, don't forget the suck-back trap.

[jdurg]

Yeah. I have done it with concentrated NH3 in the H2O2, but using NaOH is probably better. The highly concentrated H2O2 will decompose any NCl3 that may form, but the NaOH is less "smelly" and easier to come by.

[person]

This sounds very interseting could someone please explain why "excited/singlet oxygen glows ? Does the oxygen get ionized or something? thanx