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ScienceSquirrel
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Your limiting reactant is calcium hydroxide which is not very soluble at all.
Getting solid sodium hydroxide is the real challenge as Blogfast says.
It never crystallises, it just turns from being a very strong solution to being a melt of sodium hydroxide that contains water.
This stuff is truly evil, as it can spatter molten droplets that will cause horrendous burns.
You can buy it for about EUR 10 for a kilogram, 99.9% pure for soap making, etc.
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ElectroWin
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but if you boil NaHCO3 solution, it loses half of its CO2 giving Na2CO3 solution. then add the lime, let settle, decant, and continue boiling down the
liquors until concentrated
[Edited on 2013-6-21 by ElectroWin]
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blogfast25
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Bear in mind that NaOH attracts CO2: if you're not careful you end up with what you started from!
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annaandherdad
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I'm wondering about what science_guy1 said, about decomposing Na2CO3 into Na2O+CO2 at high temperature. Wikipedia says Na2CO3 melts at 851C and boils
at 1633C. It doesn't say anything about decomposition.
Nevertheless, I've always assumed that part of what is in wood ashes is Na2O or K2O, and that that gives lye when treated with water. It certainly
wouldn't make lye if it were the carbonate.
Again according to wikipedia, CaCO3 produces a vapor pressure of CO2 of one atmosphere at about 900C. I wonder what the number is for Na2CO3.
Any other SF Bay chemists?
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blogfast25
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Quote: Originally posted by annaandherdad  | I'm wondering about what science_guy1 said, about decomposing Na2CO3 into Na2O+CO2 at high temperature. Wikipedia says Na2CO3 melts at 851C and boils
at 1633C. It doesn't say anything about decomposition.
Nevertheless, I've always assumed that part of what is in wood ashes is Na2O or K2O, and that that gives lye when treated with water. It certainly
wouldn't make lye if it were the carbonate.
Again according to wikipedia, CaCO3 produces a vapor pressure of CO2 of one atmosphere at about 900C. I wonder what the number is for Na2CO3.
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It's not clear what Na2CO3 decomposes to at extremely high temperatures. But that doesn't appear to be a very practical way of preparing Na2O, unlike
CaO that is obtained on a rather grand scale from 'burning' limestone.
What you find in wood ashes is K2CO3, aka 'pot ash' (or 'potash'), from which the name potassium is derived. It's only a couple of percent (or so) but
it was once a prized source of potassium before potassium salts began to be mined. Wood ash would be collected in pots, the potassium carbonate then
leached out of the ash with hot water.
[Edited on 21-6-2013 by blogfast25]
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Dr.Bob
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"What you find in wood ashes is K2CO3, aka 'pot ash' (or 'potash'), from which the name potassium is derived. It's only a couple of percent (or so)
but it was once a prized source of potassium before potassium salts began to be mined. Wood ash would be collected in pots, the potassium carbonate
then leached out of the ash with hot water."
That is true, but wood being a complex mixture and fire being a vague process, you actually get a complex mixture of K2CO3, Na2CO3, KOH, NaOH, NaCl,
KCl, and much more in real life. That is a plenty basic enough mixture to make some simple soap with grease if heated long enough, but it would not
work as well for making biodiesel or doing much real chemistry.
And as others have pointed out, getting a soln. of NaOH into a solid, dry form is not easy. So while electrolysis and other methods are fine for
experimental purposes, and even small scale reagent synthesis, they are tough to use for preparative amounts of chemicals, especially if needed in
commercial amounts, like for making biodiesel, which requires as dry a source of base as possible, preferably NaOMe, but NaOH will do if you don't
mind using more of it, and lower yields.
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annaandherdad
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Thanks, Bob, in the meantime I looked up the thermal decomposition of Na2CO3. It seems that you only get some decomposition into Na2O + CO2 after the
carbonate is melted, and then only a small percentage of Na2O appears in the melt. That's because the Na2O vaporizes, or comes off as Na + O2, as it
is produced. The bottom line seems to be that thermal decomposition of sodium carbonate is not a good way to make Na2O, no matter how hot you are
willing to go.
Reference:
The Thermal Decomposition.of Sodium Carbonate by the Effusion Method
Ketil Motzfeldt
J. Phys. Chem., 1955, 59 (2), pp 139–147
Any other SF Bay chemists?
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blogfast25
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| Quote: Originally posted by Dr.Bob | That is true, but wood being a complex mixture and fire being a vague process, you actually get a complex mixture of K2CO3, Na2CO3, KOH, NaOH, NaCl,
KCl, and much more in real life. That is a plenty basic enough mixture to make some simple soap with grease if heated long enough, but it would not
work as well for making biodiesel or doing much real chemistry.
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KOH and NaOH? I doubt that VERY much. They would not survive the CO2 rich environment in which they are generated. Na2CO3 is probably a minority
constituent. NaCl and KCl as contaminants only.
Fire is not really a 'vague' process: what so 'vague' about complete incineration?
Biodiesel (transesterification of triglycerides) requires KOH or NaOH: carbonates aren't alkaline enough.
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ElectroWin
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| Quote: Originally posted by blogfast25 |
KOH and NaOH? I doubt that VERY much. They would not survive the CO2 rich environment in which they are generated. Na2CO3 is probably a minority
constituent. NaCl and KCl as contaminants only.
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yes, Na2CO3 and K2CO3 appear in wood ashes as minor constituents; when fresh, though, much wood ash has plenty of CaO, which is effective at stealing
the carbonate when you leach it
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blogfast25
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| Quote: Originally posted by ElectroWin | | yes, Na2CO3 and K2CO3 appear in wood ashes as minor constituents; when fresh, though, much wood ash has plenty of CaO, which is effective at stealing
the carbonate when you leach it |
I was recently involved in a minor research project with the aim of reducing the alkalinity of paper/paper pulp/cardboard fly ash for safe and cheap
disposal.
I found more than 30 % of CaCO3 in the ash and yes, some CaO (by then Ca(OH)2, of course) in the water leachate of said ash. But the amount was very
small and appeared to be due to too high incineration temperature. I doubt very much if wood ash obtained from 'normal' wood fires contains much quick
lime at all: CaCO3 only starts losing CO2 above 800 C and it's a slow process at that temperature. And in paper/cardboard, cheap CaCO3 is likely used
as a cheap filler, so there's more of it.
[Edited on 22-6-2013 by blogfast25]
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ElectroWin
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yes, laser-printer paper especially has CaCO3 added, as a filler. but i got good results from leaching paper i had burned in a wood furnace. the
leachate had a strong soapy feel to it and made decent lye.
but i also sealed the ashes from moisture and atmosphere after burning, to help keep them fresh. When fresh, they are white. after moisture gets to
them, they turn a dull gray.
as for burning temperatures and time, the paper i burned got to a red-orange to orange hot. 800 C is only about a cherry red.
[Edited on 2013-7-08 by ElectroWin]
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bfesser
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Interesting. I was under the impression that <a href="http://en.wikipedia.org/wiki/Bentonite" target="_blank">bentonite</a> <img
src="../scipics/_wiki.png" />, rather than CaCO<sub>3</sub>, was used as a filler in paper. I've never observed fizzing, as would be
expected with CaCO<sub>3</sub>, from wetting of copy paper with acidic solutions:
<strong>CaCO<sub>3</sub>(s) + 2 H<sub>3</sub>O<sup>+</sup>(aq) → Ca<sup>2+</sup>(aq) +
3 H<sub>2</sub>O(l) + CO<sub>2</sub>(g)</strong>
After burning, I would think the bentonite would leave various K, Na, Ca, Al oxides, hydroxides, and carbonates. I'm struggling to find a reference
for the use of bentonite in paper, however. My searches keep turning up sellers of bentonite for use in papermaking, but no explanation.
[edit]
Evidently, either or both are used along with TiO<sub>2</sub>. So now you've got Na, Al, K, Ca, Ti and who knows what else?<a
href="http://www.paperonweb.com/A1056.htm" target="_blank"> | Quote: | | Inorganic portion consisting of mainly filling and loading material such as calcium carbonate, clay, titanium oxide etc may be 0 - 30% of paper.
<img src="../scipics/_ext.png" /> |
</a>It's not a pretty website, but the claim is within reason.
[Edited on 7/12/13 by bfesser]
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ElectroWin
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ok! bubbles, or the lack, thereof, in acid solution, would seem to be definitive.
it frustrates me to be wrong about what the filler material is, but i stand by my observations, that (1) fresh ashes are white; (2) there is an
exothermic reaction upon adding the ashes to water; and (3) the leachate gets a soapy feel to it and makes good lye.
[Edited on 2013-7-11 by ElectroWin]
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Random
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I think it depends on how hot the fire was. Needless to say I have dissolved aluminium in wood ash/Ca(OH)2 mixture in water. There was big excess of
both compounds for their water solubility. Almost like a paste.
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: removed
unnecessary quote(s)]
[Edited on 7/12/13 by bfesser]
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bfesser
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<strong>ElectroWin</strong>, I never said you were wrong. Calcium carbonate is a filler component, but it may not be the
<em>only</em> component. In fact, this composition would seem to support your observations. I have no doubt that burning copy paper
produces plentiful CaO, Na<sub>2</sub>O/NaOH, KOH, etc.
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blogfast25
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A recent analysis of fly ash from paper/cardboard incineration for a client showed it to contain only small amounts of CaO. Ordinary burning of
copying paper doesn't generate enough heat to convert CaCO3 to CaO, I think. Never mind Na2O...
[Edited on 12-7-2013 by blogfast25]
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bfesser
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Thanks, <strong>blogfast25</strong>. Any chance you could share the analysis—if it isn't confidential or proprietary? Even a
heavily <a href="http://en.wikipedia.org/wiki/Sanitization_(classified_information)" target="_blank">redacted</a> <img
src="../scipics/_wiki.png" /> copy could prove insightful
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ElectroWin
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also it isnt the fly ash but the bottom ash that i collected and processed
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experimenter_
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I have tried to electrolyse concentrated NaHCO3 solution on carbon electrodes. It gave the typical H2/O2 mix (it "bangs" with flame), not CO2 (or very
few). Also the pH in the solution did not rise at all after few hours of electrolysis. The electrodes corroded heavily.
- Probably Na2CO3 or K2CO3 is needed for this to work.
- The bubbling CO2 might react with the NaOH and convert it back to carbonate. So maybe cell separation is required.
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XeonTheMGPony
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| Quote: Originally posted by experimenter_ | I have tried to electrolyse concentrated NaHCO3 solution on carbon electrodes. It gave the typical H2/O2 mix (it "bangs" with flame), not CO2 (or very
few). Also the pH in the solution did not rise at all after few hours of electrolysis. The electrodes corroded heavily.
- Probably Na2CO3 or K2CO3 is needed for this to work.
- The bubbling CO2 might react with the NaOH and convert it back to carbonate. So maybe cell separation is required. |
If your goal is to make sodium hydroxide go the mercury route IMO, I did this, only I reacted the Cl2 and the H2 to make hydrochloric acid while I was
at it.
I been thinking of modifying the cell some how to recover pure sodium as as well, will post one of these days on it if I suceed
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experimenter_
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| Quote: Originally posted by XeonTheMGPony |
If your goal is to make sodium hydroxide go the mercury route IMO, I did this, only I reacted the Cl2 and the H2 to make hydrochloric acid while I was
at it. |
Cool. How did you combine the gases and what were the results? I have been trying something similar:
http://www.sciencemadness.org/talk/viewthread.php?tid=65883
My interest in the NaHCO3 electrolysis experiment was to find a way to capture atmospheric CO2. I would not be interested in the lye produced except
that it would capture CO2 from the air.
I'm not interested in the mercury way also since I do the experiments only for amusement. I have tried gallium but it seems that it cannot form a
liquid alloy with sodium. Maybe lithium electrolysis with the Ga cathode has more chances of working.
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XeonTheMGPony
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The way I did it was very dangerous back then! I used simple water flash back arresters, and a simple premixing tube that lead into a big jar and
spark plug, then that ran to ice water.
the spark was started then the cell, it seemed to work but again back then it was mucking about and no way to test the hcl concentration.
The cell its self how ever worked exceedingly well, good strong hydroxide! Just ran it till I couldn't make hydrogen any more.
Your UV issues is you're using UV-B, You need UV-C Air cleaner UV bulbs make this, or if you buy a "Plasma cell Ozone generator" for hot tubs it is
just a UV-C based generator, care fully dismantle and repurpos it.
UV-C is to be considered a serious health risk, shield body and eyes from radiation and any thing you wish to live for that matter, and it will
produce ozone in the immediate area.
https://www.youtube.com/watch?v=MtygiCwnEzw < Hydrogen flame in Chlorine
I am sure now days I could do better, but so you can surely do even better! I used a spark plug but with some thinking you can surely find a better
method. but despite how haphazard my rig was it did work! it ran like a little blow torch inside the jar and exhausted though the ice water.
Side note: I totally forgot about that system that I made! that was when I was 15! It has been 18 years now and till I found this thread I had never
remembered it, lol all this time I was wondering where I could get high purity HCL LOL life is weird like that!
[Edited on 29-4-2016 by XeonTheMGPony]
[Edited on 29-4-2016 by XeonTheMGPony]
[Edited on 29-4-2016 by XeonTheMGPony]
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experimenter_
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Some new experiments showed that with A.C. current (50Hz) a gas that is not flammable at all is produced. However, the rate of production was very
small; even at 2A I wasn't able to capture enough of the gas to test it. I think that a lower frequency of the A.C. current might result in a higher
evolution rate.
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Romix
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Electrolyse NaCl, separating cathode from anode, so that electrons can flow through.
You'll get, NaOH formed on the cathode.
Be about the price of buying bulk. + saves time.
But if you have free electricity, then worth it.
[Edited on 1-7-2016 by Romix]
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experimenter_
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According to this source:
Na2CO3 = Na2O + CO2 (t>1000°C)
I don't know if it worths the trouble to find a furnace for 1000°C but it seems a possible route.
Afterwards, just dissolve the Na2O in water and get NaOH.
[Edited on 1-7-2016 by experimenter_]
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