ParkinsonWilkinson
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Simple synthesis of NaOH from baking soda
If you're like me and live in a country when NaOH is completely banned, like Singapore, you'll know how troublesome it is to get it. While you might
be able to order it online, a lot of people who are actually interested in practical chemistry are still living with their parents, and may not be
able to order it. Therefore, I have found 2 ways to make NaOH with baking soda.
Method 1 - Synthesis with baking soda and vinegar
1. Mix baking soda and vinegar, with a slight excess of baking soda (NaHCO3+CH3COOH -> CH3COONa + H2O + CO2)
2. Collect the resulting liquid, and heat it until all the water has boiled off (2CH3COONa -> Na2O + (CH3CO)2O)
3. Heat for another 30s, then add water to the dry powder (Na2O+H2O -> 2NaOH)
4. You should get fairly pure NaOH, but if you do not, repeat steps 2 and 3
I do not really like this method, as it is pretty troublesome to do and produces acetic anhydride in gaseous form, which reacts with water vapour to
produce airborne vinegar. However, it does not require strong heating, and can be done very easily
Method 2 - Synthesis with only baking soda
1. Mix baking soda with a few drops of water
2. Heat the resulting mixture until all the water boils off (2NaHCO3 -> Na2CO3 + H2O + CO2)
3. Heat the powder until it starts to turn slightly brown/black (Na2CO3 -> Na2O + CO2)
4. Add water to powder (Na2O+H2O -> 2NaOH)
I prefer this method, as it is much more efficient. However, step 3 requires pretty strong heating(>500c).
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Jome
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These equations/reactions are.... weird. Heating sodium acetate will not yield acetic anhydride and sodium oxides, it will yield sodium carbonate
(Na2CO3) and acetone, CH3COCH3.
Decomposing sodium carbonate takes extremely high temperatures, far higher than 500 C, and wouldn't be a very rapid reaction at that.
A saturated solution of Na2CO3 can be combined with slaked lime, Ca(OH)2 to precipitate CaCO3 and leave a solution of NaOH.Problem is to quickly
filter the thick, cream-like precipitate to prevent CO2 absorption, or somehow boil a more dilute solution down without the container getting eaten
and/or CO2 getting access.
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clearly_not_atara
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I doubt you have to filter it that fast. Typical CO2 concentrations are about 400 ppm (300 ppm before AD 1900!) or 1/2500 and there are 22.4 liters of
gas in a mole at STP. So you would need to extract the CO2 from 22.4 * 2500 * 0.1 / 2 = 2800 liters of air to neutralize 0.1 mole of NaOH. But the
presence of a microdispersed precipitate is annoying in and of itself.
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PirateDocBrown
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Not to mention that Na2O is explosive on contact with water.
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ParkinsonWilkinson
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I know that this method produces very impure NaOH, but I have personally tested both of them, and both seem to work for me. I have tried heating
sodium acetate, and I did not get any acetone. The sodium carbonate takes some time to decompose, but it does happen at temperatures under 1000c(I
used isopropanol flame for heating). As for the Na2O being explosive, I have not noticed that when adding water(although this is probably due to the
high amount of impurities). While this method is very crude, it does produce detectable amounts of NaOH, but should only be used if there really is no
other way to get NaOH.
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draculic acid69
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I doubt this method makes any Amount of NaOH. All the equations look incorrect at first glance. Also this is a well known pathway to sodium carbonate
and acetone it's well known that alkaline carbonates don't decompose easily to there hydroxides the way alkaline earth metals do.
[Edited on 9-5-2022 by draculic acid69]
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ParkinsonWilkinson
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I have already tried it, and it does produce detectable(pH 14 on pH paper) amounts of NaOH. However, it does not produce anything substantial(very
little visible reaction with aluminum foil)
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Tsjerk
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Sodium carbonate does lose CO2 around 850 degrees, which is easily reachable with an Bunsen burner.
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Jome
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You are correct, of course. But the temperature where something starts to decompose isn't necessarily where it decomposes to the degree that the
reaction could be used to produce a reagent, I found that out in my youth while trying to thermally decompose KNO3.
OP would get a very high pH even if only 0.1% of the CO2 left!
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Chemgineer
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You could produce quite clean NaOH by electrolysing NaCl in a membrane cell. You can use a clay pot as a membrane.
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Rainwater
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Scrap science has some good videos on producing NaOH from NaHCO3
https://youtu.be/OrEQkBOxmxg
I keep the concentration of NaOH around 8%~11% for better production rates at the cost of efficiency
Concentrating the solution into a dry powder is not easy. My favorite method is vacuum distillation.
"You can't do that" - challenge accepted
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ParkinsonWilkinson
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Thanks everyone for the input. I have found that electrolysis of Na2CO3(even without a membrane) is quite effective at producing NaOH (https://core.ac.uk/download/pdf/36998552.pdf)
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Alkoholvergiftung
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The decompusen of Na2CO3 with Fe2O3 was the first industrial methode of NaOH production but i thing you need 900C. The ferrit was than decompused in
hot water.
[Edited on 10-5-2022 by Alkoholvergiftung]
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Fantasma4500
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youre worried that .. acetic anhydride .. will produce vinegar? thats interesting.
is the decomposition of sodium acetate really into Na2O? im hearing the typical way of doing this is loading a flask with glacial acetic acid and
anhydrous sodium acetate (dont ask me why you wanna add in GAA in the first place) and then distilling off the GAA, and then you will get acetic
anhydride coming over
but Na2O is interesting in itself, it would react with EtOH to form sodium methoxide
im confident that sodium acetate decomposes at rather low temperature as some of it decided to decompose in my oven, as i was dehydrating some MgCl2-
at about 180-200*C i was having some kind of acidic vapours
now since others have dodged out of the original prep- i would like to chime in too
Ba(OH)2 + Na2SO4 = NaOH + BaSO4 (ppt)
Ca(OH)2 + Na2SO4 = CaSO4 (ppt) + NaOH (more tedious due to solubility of Ca(OH)2)
i believe one ancient method was to take halfway burnt wood and dunk in water, and it did indeed produce some hydroxide solution, not just carbonate-
yields might not be fantastic until you scale it up
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macckone
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A more traditional method:
Ca(OH)2 + Na2CO3 -> CaCO3 + 2NaOH
This is also the reaction that takes place in ash to make 'caustic potash' from 'potash' but using K2CO3.
This occurs naturally if the fire reaches 800C and is extinguished before the temperature drops too low.
Softwood does not generally get this hot while hardwood charcoal can exceed this by 200-300C.
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ManyInterests
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Sodium Hydroxide is banned in Singapore? I know many places tend to ban sulfuric acid for a variety of reasons, but even in those countries sodium
hydroxide is usually left alone.
That being said, I might give your formula a try.
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PirateDocBrown
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Quote: Originally posted by macckone  | A more traditional method:
Ca(OH)2 + Na2CO3 -> CaCO3 + 2NaOH
This is also the reaction that takes place in ash to make 'caustic potash' from 'potash' but using K2CO3.
This occurs naturally if the fire reaches 800C and is extinguished before the temperature drops too low.
Softwood does not generally get this hot while hardwood charcoal can exceed this by 200-300C. |
Or just use a muffle furnace. Actually pretty easy to make one.
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mysteriusbhoice
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just get sodium bicarbonate cake and stainless steel electrodes with tons of amps as it's known that bicarbonate decomposes in water electrolysis
cells to hydroxide slowly.
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