Aurum
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Make Lithium Bromide.
How would I make some Lithium Bromide.
I can get the following,
Lithium Hypochlorite - pool shop
Lithium Carbonate - pottery shop
Potassium Bromide - Photography shop
Sulphuric acid - drain opener
After much reading, I think my best way would be,
Add Sulphuric to Potassium Bromide to get HBr.
Dissolve HBr in water to get Hydobromic Acid.
Add Hydrobromic acid to Lithium Carbonate to get Lithium Bromide.
Will this work? Anything to be careful of?
Is there a better route, using the hypochlorite?
Is there another way to obtain Lithium Bromide?
I need about 100g for an absorption cooling experiment.
Thanks.
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woelen
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All of your procedure is OK, except the part of making HBr from KBr and H2SO4. That latter reaction also gives SO2 and Br2, due to partial oxidation
of the bromide.
What you could do is mix KBr with H3PO4 and heat. That gives pure HBr.
Another option is to use a solution of KBr in dilute H2SO4 and heat that. This gives water vapor and at a certain point HBr/H2O is produced. This
procedure, however, only allows partial recovery of HBr from the solution. At a certain point, the liquid will turn yellow and the same problem occurs
as with conc. H2SO4 + solid KBr. So, only use this if no H3Po4 is available.
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not_important
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How pure do you want the LiBr to be?
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Pyridinium
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| Quote: | Originally posted by woelen
All of your procedure is OK, except the part of making HBr from KBr and H2SO4. That latter reaction also gives SO2 and Br2, due to partial oxidation
of the bromide. |
True, but he could just use cool, somewhat dilute H2SO4, which is not oxidizing... it's just that the yield wouldn't be that great. AFAIK, production
of HBr depends only on protonation of the bromide ion by the H+ of sulfuric acid, which doesn't require hot acid. I don't have the pKa of HBr in
front of me, though.
Anyway, he could crystallize out the KHSO4, leaving a solution containing HBr, to which the lithium salt could be added.
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Magpie
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There is a method in Brauer (in our library) for making 48% HBr which I have used with good success. Also see
http://www.sciencemadness.org/talk/viewthread.php?tid=2169&a...
The single most important condition for a successful synthesis is good mixing - Nicodem
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not_important
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If you are not in a rush you can place two glass or ceramic containers in a large plastic contain with a lid. Put Li2CO3 in one, add at least enough
distilled water to dissolve the molar equivalent amount of LiBr. In the other put KBr and sulfuric acid, diluted down to 30% or so - not strong
enough to oxidise HBr at room temperature; use an slight excess of KBr.
Close the container with a lid with a pinhole in it, or with a sheet of thin polythene film - but you'll want to watch that to make sure the CO2 is
diffusing out fast enough to not be making the film balloon out too much. Ignore for days or even weeks. The carbonate will be converted into a
solution of the bromide.
This is slow, depending on the diffusion of HBr from the container of acid to the caontainer of Li2CO3, but doesn't need any heating. And as only
substances that have appreciable vapour pressure and diffuse through air will reach the carbonate, contaminates in the acid aren't much of a problem.
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Aurum
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Thanks everyone.
I think I’m going to try the diffusion method. But, as I don’t need conc. H<sub>2</sub>SO<sub>4</sub> then I am going to
substitute NaHSO<sub>4</sub>. I worked out that the following should happen,
2NaHSO<sub>4</sub> + 2KBr => Na<sub>2</sub>SO<sub>4</sub> + K<sub>2</sub>SO<sub>4</sub>
+ 2HBr
and then,
Li<sub>2</sub>CO<sub>3</sub> + 2HBr => 2LiBr + CO<sub>2</sub> + H<sub>2</sub>O
I am going to use 50g of KBr (I need to order some more) and calculate that I need 58g of NaHSO<sub>4</sub> (monohydrate) and 15.5g of
Li<sub>2</sub>CO<sub>3</sub>. This should give me 36.5g of LiBr.
I would be very grateful if someone can confirm the above equations and figures. The quantities equate to 0.21M.
A couple of questions,
How much water should I add to the NaHSO<sub>4</sub> + KBr mix?
To get an excess of HBr, I intend to reduce the amount of LiCO<sub>3</sub> by 10% to 14g. Is this a reasonable excess?
Should the vent in the plastic box be on the bottom to reduce loss of HBr?
Can I assume completion when the carbonate has dissolved?
Any guess on timescale?
Again, thanks for all your help.
[Edited on 28-3-2007 by Aurum]
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not_important
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HBr is denser than air, but with a really slow formation rate I believe that diffusion mixing will prevail and density not be too important.
Why an excess of HBr? Just to see when the reaction is done?
In place of the slow leak, you could instead use a bubble trap like that used for brewing, but use mineral oil rather than water.
Timescale - I mostly have done this with technical HCl, which is almost always contaminated with iron; this method gets around having to distill the
acid. I always used an excess of the carbonate/hydroxide/oxide, this helped reduce impurities as some of the contaminating metals in the raw carbonate
would mostly precipitate on the surface of the excess carbonate/oxide. I just eyeballed it, when it looked as enough carbonate was gone, I considered
the reaction over. Same when I did it for bromides and iodides, I would simply set it aside in the shed for several weeks, and then work it up.
If you are in N America, check and see if there any pool/spa supply stores near you, or any of the large chain hardware stores; these often stock
sodium bromide in the pool chemicals, this is likely to be a cheaper source of bromine than photo grade KBr.
I don't know if bisulfates will function as useful acids in this case, it's going to depend of the relative Ka values.
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12AX7
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Bisulfate isn't all that strong compared to HBr. You may create some, but it's not going to want to leave the solution much anyway. Heat will help,
and maybe a lot would be a good thing! Better to stick with stronger acid.
It could easily take weeks, depending on surface area and temperature and whatnot.
Tim
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Aurum
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I thought that when bisulphate was in solution you could think of it as sodium sulphate + sulphuric acid.
2NaHSO<sub>4</sub> => Na<sub>2</sub>SO<sub>4</sub> + H<sub>2</sub>SO<sub>4</sub>
If so, and I used NaBr instead of KBr then when I use H<sub>2</sub>SO<sub>4</sub>, half way through I have the same solution
as with the bisulphate. Have I understood this correctly?
Why the excess of HBr? I read in your post "use an slight excess of KBr" and assumed an excess of HBr was the intension. I now realise that it's
better to have the carbonate as the limiting reagent.
Why the vent in the bottom? I assumed (wrongly) that CO<sub>2</sub> would be heavier than HBr. I now see that HBr is almost twice as
heavy.
I think I will try it with the bisulphate as I have lots around and if it doesn't work I can add some acid as required.
Thanks.
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not_important
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Check the Ka value for sulfuric acid, the first is much greater than the second; bisulfate is favoured over a mix of the acid and sulfate.
Yes, and I'll bet you'll find that bisulfate is where it stops for practical purposes. When making HCl or HNO3 using sulfuric acid, the reaction stops
at the bisulfate unless higher temperatures are used.
Vent at top, just a very slow leak or a bubbler.
Excess of the bromide just to use all the acid. When I'll letting it run until I remember to check it, I figure it's best to have just the desired
acid around near reactions end.
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tupence_hapeny
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For the NaBr & KBr deprived among us, like myself, how the fuck do I get bromine out of this mess (which is every single Brominating agent at the
local pool supply shops):
1-bromo,3-chloro 5,5-dimethyl hydantoin
Starting from the beginning, and thanks to IUPAC, I can see that the two methyl groups are apparently attached to same No.5 carbon, and I know what hydantoin is. Therefore, as shown in the picture above the bromine and the chlorine are both hanging off the end of the molecule.
I hope that simply adding caustic (NaOH/KOH) will liberate them (but I expect it won't), providing me with NaBr/NaCl or KBr/KCl and the
1,3-dihydroxy-5,5-dimethylhydantoin (which I can find no data on at all)?
Or is it that if I added HCl the acid would liberate the Bromine as HBr? Alternatively, could I swap the NaCl for NaBr?
In addition to that, our pool chlorine is starting ot be taken over by this darling,
http://en.wikipedia.org/wiki/Trichlor
trichloroisocyanuric acid (and the dichloro), which when heated gives off cyanic acid. So my questions vis-a-vis this one is whether it is possible to
reduce the cyanic acid to it's hydrocyanic cousin, and then catch that baby in NaOH or KOH? Or would it be better to make the sodium or potassium
cyanate and reduce that?
[Edited on 9-4-2007 by tupence_hapeny]
We are all the sum of our experiences, and our reactions to the same
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Aurum
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tupence,
Where about in Aus are you? I tried to send you a U2U but the BB seems to have messed up.
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Nicodem
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| Quote: | Originally posted by tupence_hapeny
For the NaBr & KBr deprived among us, like myself, how the fuck do I get bromine out of this mess (which is every single Brominating agent at the
local pool supply shops):
1-bromo,3-chloro 5,5-dimethyl hydantoin |
This was already answered in the thread about bromine preparation. UTFSE!
| Quote: | | I hope that simply adding caustic (NaOH/KOH) will liberate them (but I expect it won't), providing me with NaBr/NaCl or KBr/KCl and the
1,3-dihydroxy-5,5-dimethylhydantoin (which I can find no data on at all)? |
No, it does not make any redox sense.
| Quote: | | Alternatively, could I swap the NaCl for NaBr? |
For what use and where?
| Quote: | | trichloroisocyanuric acid (and the dichloro), which when heated gives off cyanic acid. |
Pyrolysis of TCCA is way more complex than that! Besides cyanic acid can not be formed because (a) there are no hydrogens in TCCA and (b) cyanic acid
itself decomposes on heating.
| Quote: | | So my questions vis-a-vis this one is whether it is possible to reduce the cyanic acid to it's hydrocyanic cousin, and then catch that baby in NaOH or
KOH? Or would it be better to make the sodium or potassium cyanate and reduce that? |
What the hell is "hydrocyanic acid"?
You can not make sodium or potassium cyanate from TCCA. However, you can make cyanates by heating trisodium or tripotassium cyanurate or a mixture of
Na2CO3 or K2CO3 and cynuric acid at 200°C or more (cyanuric acid can be bought in the same places as TCCA or alternatively it can be made from urea
or by reducing TCCA). UTFSE and see the thread on cyanate & cyanide preparations for deatails about preparing cyanates from cyanuric acid.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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tupence_hapeny
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What a lovely suprise,
Nicodem (WWFW), as you will see in the attachment, I did use the fucking search engine, I looked for Bromine (and got like 20 pages of results, go
figure) and when I tried to narrow it down I got none (as per attachment).
I then decided to attach the question to what appeared to be the only recent (and ongoing) thread on Bromine, with the result you now see.
As this would appear to be a rational approach, I see no reason to apologise.
The question vis-a-vis cyanuric acid was not originally destined for here, however, as this discussion was the venue for some questions re.pool chems,
I decided to tack it on as an afterthought. For that I do apologise most humbly, oh venial one. I sincerely beg your forgiveness for asking questions
in the 'beginnings' area, perhaps by reason of having mistakenly believed that this was the place to do such a thing?
As always, such a pleasure...
tup
Why thank you for the answers to the questions I ask, although, as usual to be gleaned from a page full of spite. You forget, I have studied law -
that is exactly how law is taught - it helps people think for themselves...
Anyhow, here is the only hit on the relevant compound from my search - prior to this post no hits were forthcoming:
[Edited on 11-4-2007 by tupence_hapeny]
Attachment: Sciencemadness Discussion B.pdf (81kB)
This file has been downloaded 975 times
We are all the sum of our experiences, and our reactions to the same
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PainKilla
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Generally, when one UTFSE, they actually read the results. I am in pretty good mood, so all the relevant info that you need is in the Bromine thread.
Or perhaps, all of the info that you need to change your mind from using that... either way, it's there.
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