chief
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BaCO3 from (BaSO4 + Na2CO3) _melt_
As was discussed in another thread one can obtain BaCO3 from BaSO4 at 99% efficiency by cooking with about 15 times the stoechiometric amount of
Na2CO3 for 1-2 hours (concentrated solution).
Now that I have a new furnace I want to try the other way:
Melt the BaSO4 with some amount of Na2CO3 .
Can I use stoechiometric amounts, or must I use excess Na2CO3, and how much? How long to let the melt react ? I can use temperatures up to 1050
[Celsius]: What is the optimum and could I go for the direct way of BaSO4 + charcoal?
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Xenoid
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BaCO3 can be bought from pottery suppliers quite cheaply!
BaSO4 melts at about 1350 oC. Na2CO3 melts at 854 oC. and starts to decompose. I would imagine decomposition would be complete before 1350 oC. is
reached! Apparently the BaSO4 is decomposed to some extent by excess Na2CO3, but my reference is not precise, it doesn't sound very efficient!
The procedure for making BaCO3 from BaSO4 involves heating the latter with coke, coal or charcoal to form crude BaS and CO. The BaS is then heated in
a stream of moist carbon dioxide and is converted to BaCO3 and hydrogen sulphide.
BaS + CO2 + H2O --> BaCO3 + H2S
This is the reason crude pottery grade BaCO3 smells so bad when it is dissolved in acids, it is contaminated with the intermediate BaS.
Hope this helps!
Regards, Xenoid
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not_important
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You still need a considerable excess of Na2CO3 to make it work; 10:1 weight ratio Na2CO3 to BaSO4 is typical for analytical work. An alternative is
to fuse the BaSO4 with H3BO3, which results in the displacement of SO3; 10:1 ration or even higher for analytical work. Same temperature range, 950 to
1000, 15 minutes often does the job for carbonate, 10 for boric acid.
If boric acid is used, either the cooled melt can be treated with hot water and then sodium carbonate added, or Na2CO3 can slowly be added to the
fusion mixture after the 10 minutes or so of heating. Slow addition reduces problems with foaming, and helps flush out remaining SO3, which will be
swept away with the CO2 so long as the melt remains acid - excess boric acid/oxide.
Both of the molten carbonate or boric acid fluxes will attack ceramics. Nickel containers are best of the moderate priced ones, stainless steel will
work.
old analytical
http://books.google.com/books?id=jv0uKgPUKLIC&pg=PA51&lpg=PA51&dq=barium+carbonate+sulfate+(fusion%7Cmelt)&source=web&ots=yr0Dnxq6
CD&sig=52ev6aum2y6tUFG1AMr39P0NE9A
Modern industrial production methods - BaSO4 + C
http://books.google.com/books?id=W-lY7_9jIfcC&pg=PA285&lpg=PA285&dq=barium+carbonate+sulfate+(fusion%7Cmelt)&source=web&ots=GCixwn
qV_N&sig=tjmF4s2Qraeg0d3--dIFnSXRxLE
Note if you go the BaSO4 + C route, don't use cooking charcoal, the mineral ash will contaminate your barium. It was more typical to use heavy oil or
tar as the carbon source, this also makes it easier to get good contact between the sulfate and reducing agent.
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12AX7
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FYI, hardwood charcoal is quite pure, in the 99% range IIRC. It's certainly sufficient for industrial smelting of silicon.
Tim
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chloric1
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I am going to have to try the sodium carbonate solution trick myself so at least I can get some ball park numbers on the conversion. I will have a
little barium sulfate soon as a byproduct of hexavalent chromium treatment and disposal using metabisulfite. I should have little more than 20g of
barium sulfate so I think a 1000 ml boiling washing soda solution should suffice.
Fellow molecular manipulator
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chief
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I have done it: Several washings (4-5) with quite concentrated Na2CO3-solution (boiling for 1-1.5 h each), and the result was about 60-80 %
conversion. But it's a lot of washing/decanting, much work to be done for the result.
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not_important
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| Quote: | | Several washings (4-5) with quite concentrated Na2CO3-solution (boiling for 1-1.5 h each), and the result was about 60-80 % conversion. But it's a lot
of washing/decanting, much work to be done for the result. |
Back in the old days they'd just filter the unreacted BaSO4 out of the solution formed from dissolving the 'BaCO3' in acid, and then recycle it.
BTW, when making soluble salts a trick is to make sure some unreacted carbonate, hydroxide, or oxide remains after the acid treatment, that is don't
use enough acid to dissolve all the carbonate; for Sr and Ba add a little of the hydroxide if you have it. This results in many of the trace
impurities remaining one the solid carbonate and thus removable by filtration. Bubbling filtered air through the hot solution + suspended carbonate
helps push Fe and Mn to the higher oxidation, less soluble state.
| Quote: |
FYI, hardwood charcoal is quite pure, in the 99% range IIRC. It's certainly sufficient for industrial smelting of silicon.
Tim |
Still runs several percent ash, about 1/5 to 1/3 Ca, 0,5 to 1,5 Mn
http://www.fpl.fs.fed.us/documnts/pdf1993/misra93a.pdf
http://www.bioheat.info/pdf/kpn_wood_fuels_at.pdf
http://www.energy-products.cn/trade/hardwood-charcoal-459/
http://www.agrorestu.com/hardwood_charcoal.htm
http://indonetwork.co.id/INDOENERGY_MM/230088/charcoal.htm
http://cv--indoarab-interprise.tradenote.net/product/3841-Sh...
http://www.exporters.sg/showroom_item.asp?id=114973
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