Sciencemadness Discussion Board - Preparation of BrCl (liquid)

Preparation of BrCl (liquid)

tinker - 11-11-2003 at 09:44

Hi,

I need to use Bromine Chloride, BrCl (l), in its liquid phase in a chemical process. The amount of BrCl (l) required is minute, maybe even just a trace.
What is the best (small scale) preparation for BrCl (l) in a lab with very limited resources? Could BrCl (l) be bought from one of the chemical suppliers?
Are there any publications or encyclopedias that do describe various alternative preparation methods for BrCl?
Since I don’t have experience with halogens any general comments, concerning safety, storage, etc., are most welcome.

Thanks in advance for your help,
Tinker.

I am a fish - 11-11-2003 at 11:06

Bubble chlorine through a saturated solution of sodium (or potassium) bromide. The bromide ions will be oxidised into bromine, some of which will further react with the chlorine to produce bromine monochloride.

Bromine monochloride boils at 5oC, and so if the sodium bromide solution is kept at about 10oC (in order to get the product into gas phase, whilst minimising evaporation of the bromine), the outgoing gas should consist of the product mixed with excess chlorine. This can then be seperated out by cooling the gas.

tinker - 12-11-2003 at 11:12

Quote:

Originally posted by I am a fish
Bubble chlorine through a saturated solution of sodium (or potassium) bromide. The bromide ions will be oxidised into bromine, some of which will further react with the chlorine to produce bromine monochloride.

Bromine monochloride boils at 5oC, and so if the sodium bromide solution is kept at about 10oC (in order to get the product into gas phase, whilst minimising evaporation of the bromine), the outgoing gas should consist of the product mixed with excess chlorine. This can then be seperated out by cooling the gas.

Thanks for your expeditious reply.

I am not sure on the best and cheapest procedure for producing sufficient chlorine gas to be effective in oxidizing the NaBr or KBr in solution. Any suggestions?

Will NaBr and KBr work equally well in your proposed preparation of BrCl or is one preferrable over the other?

What parameters such as temperature, pressure, etc. could be adjusted to maximise the yield of BrCl?

Thanks again for your help.

I am a fish - 12-11-2003 at 14:04

Quote:

Originally posted by tinker
I am not sure on the best and cheapest procedure for producing sufficient chlorine gas to be effective in oxidizing the NaBr or KBr in solution. Any suggestions?

One way is to mix calcium hypochlorite (available from swimming pool suppliers as a chlorination agent) with an acid. (This is a very basic question. Seaching through the site will reveal this method and many others.)

Quote:

Will NaBr and KBr work equally well in your proposed preparation of BrCl or is one preferrable over the other?

Not really. The sodium or potassium ions don't take part in the reaction.

Quote:

What parameters such as temperature, pressure, etc. could be adjusted to maximise the yield of BrCl?

Temperature is already contrained as explained above. An increase in pressure would probably increase yield. However, working at elevated pressure is a pretty advanced technique for an amateur, and so I can't imagine it would be worth it.

Marvin - 19-11-2003 at 10:21

Attempting any sort of 'preperation' is somewhat misleading. 'BrCl' in anything but the solid phase is meerly the same as a mixture of Br2 and Cl2 would cause it to be. The gas/solution contains molecules in whatever form and proportion is most stable at the time.

There is virtually no evidence BrCl exists as a compound around its boiling point, just a transient molecular species.