Experimental Chemistry - 2022-05-22
Elemental bromine is made from potassium bromide by using sodium persulfate as an oxidizing agent.
Great prep! You are also reminding me to make some bromine again myself... I just used up my last 10ml today.
Thank you!
Try it with fresh NAPS. The chlorine method carries to much BrCl into the product (which is an explanation for the unusual high yields, too)...
Scale down your syntheses - for me 10 ml would be enough for two years... 😉
@Experimental Chemistry well I just used up 11ml today… Refluxing the contaminated bromine with sodium bromide solution should get rid if the BrCl problem easily so I still prefer bubbling Cl2 into NaBr solution as a first step because it works great. I might make 150ml at once next time because even 150ml will be used up within a year.
@Thy Labs Yes, refluxing with sodium bromide should help - but you didn't show it in your video last year - and of course it's always an additional step with this dangerous substance that can be avoided with the persulfate method.
Speaking of the work step and last year: what are you drying your bromine with this time?
150ml? 😲
You should get yourself a poison cabinet with a permanent gas vent...
@Experimental Chemistry Maybe with P2O5 followed by distillation. Would have to look up if they react first
This could get pretty hot and vaporize all the bromine at once...
Also, the flask glass may not like the concentrated metaphosphoric acid when destilling....
Please tell me about your experiences with it as soon as the time comes...
I like to produce bromine by the reaction of NaBrO3, NaBr and NaHSO4. It has the same advantages as the method from this video plus you don't need an oxidizer if you make the NaBrO3 by the electrolysis of NaBr.
Your method requires an additional previous step, which is not so simple as it seems, concerning to the electrolytical preparation of bromate: https://woelen.homescience.net/science/chem/exps/KBrO3_synth/index.html
You have to work with carcinogenic salts then, which I try to avoid as often as possible. And I am not allowed to show the use of dichromates on this commercial channel because of REACH regulations.
The oxidizer isn't the problem at all for me: the persulfate is freely and cheaply available here.
For all who have no access to it, I would rather recommend using H2SO4/H2O2 instead of persufate.
But I consider NaBr instead of KBr as a good idea: it contains more Br per weight, is non-hygroscopic and often cheaper than KBr.
Hi! Great video! Could you use a large excess of persulfate to achieve a higher yield?
Thank you.
With fresh persulfate a stoechiometric mixture (exactly 1:1!) normally is sufficient to get yields above 90 % (prooved in earler runs).
But if the the persulfate looks already clumped and whethered, you should double its input not to waste unreacted bromide.
I will not try it again soon - 8 ml of bromine are already enough for the next 1-2 years. As you might know, I mostly work small-scaled... 😉
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how does the alkali sodium sulfite work when reducing bromine? the naoh just reduces the so2 back to nahso3? so its just catalytic or?
No, it's a real redox reaction:
Br2 + Na2SO3 + H2O -> Na2SO4 + HBr
Additional Na2CO3 then just neutralizes the formed HBr to NaBr, water & CO2, therefore makes reduced waste or spills less corrosive and protects excess sulfite against forming choking SO2-gas, which would otherwise be released in the acidic environment of dissociated HBr in water.
Yeah but persulfate is really hard to get...
Edward Elizabeth Hitler But thanks to Brexit you were at least allowed to do so with the battery acid. In Germany we aren't anymore... We still just can get 15 % H2SO4 and 12 % H2O2 from pool additive suppliers (with registered business even more concentrated).
Are bromine and bromides banned in the UK?
Here we can easily buy it in many online stores or ebay as a supply for etching platines. I just cannot recommend German Amazon for purchase: it seems to be under monitoring - just ask Thyzoid what's going on there...
Sulfuric acid + hydrogen peroxide can be used, too (allowed 15 + 12 % are sufficient without additional water).
Never use MnO2 - that badly works...
Edward Elizabeth Hitler Here in the EU you are not even allowed to use hoarded substances if they are banned... Be glad to be out...
Edward Elizabeth Hitler That a substance can be bought does not necessarily mean that it's allowed to... And what about selfmade bromine?
Edward Elizabeth Hitler Everybody can do what he got to do on his own responsability...
Here in Germany nearly all houses have kitchens, so nobody is forced to pay for meals out...
And again more and more people grow their own vegetables in the garden...
Experimental Chemistry - 2022-05-22
Mistake in the voiceover at 1:46: The reaction vessel has of course a volume of 500 ml, not 100 ml like the collection flask... ☺ 🙄