# Making Sodium Hydroxide Comments



## lazersteve (Sep 23, 2007)

This topic is for replies to the Tutorial : Making Sodium Hydroxide found here:
Making Sodium Hydroxide

Great post, here's some additional information on this excellent process.

Heat the calcium carbonate that precipitates to red heat (825 C) and you end up with lime (calcium oxide ) which forms calcium hydroxide (hydrated lime) all over again when added to water!!!

An excellent example of working towards closing the supply loop! Way to go Irons!!! :wink: 

Steve


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## Irons (Sep 23, 2007)

Take chunks of limestone break them up in small pieces. Build a big fire and start throwing bits of limestone onto fire. Add more wood and Limestone. Let the fire die down and when it's cool, collect the ashes and burnt limestone and leach with water.



 

Plants use Potassium in their metabolism, so what you get is primarily Potassium Hydroxide.


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## lazersteve (Sep 23, 2007)

There is an excellent site with all sorts of low tech chemical processes for extracting and producing chemicals. 

Here's the link:

Caveman Chemistry

Steve


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## Irons (Sep 23, 2007)

Be it Sodium or Potassium Hydroxide, after a while it will load up, usually Sodium or Potassium Silicate from digesting those floor, bench and polishing sweeps.

Don't throw it away. Let the solution settle for several days, or even better several weeks to let all of the values settle out. If you need to use it more often, make two or more batches and use the one that is the oldest.

To your clean but loaded Alkali solution, add a spoon or two of Calcium Hydroxide and let it settle for several days. The Silicates will precipitate out as Calcium Silicate, a useful refractory material, and your solution will be as good as new.

Everything but the squeal.


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## Irons (Sep 25, 2007)

It reacts with Sodium Or Potassium Silicate to give Calcium Silicate and Sodium or Potassium Carbonate.

Everything but the squeal.


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## bmgold2 (Mar 25, 2014)

After I read Irons' post on making Sodium hydroxide I did a lot of researching and a little testing. This long post may be of use to someone. 

For anyone that doesn't already know, Sodium carbonate is also known as soda ash or washing soda. Its formula is Na2CO3 and can often be found in the detergent aisle at the grocery store. One common brand is Arm & Hammer Super Washing Soda Detergent Booster & Household Cleaner available at Walmart for about $3.24 in a 55 ounce box (3 pound 7 ounce). You can also find it as swimming pool pH Increaser. As a last resort, you can heat up some regular baking soda (sodium bicarbonate) in the oven at around 400 degrees F. (200 degrees C.) or even on the stove and turn it into sodium carbonate, water steam, and carbon dioxide. You can tell when it has changed to sodium carbonate because baking soda is a powdery, crystallized like salt, and clumps together. Washing soda is grainy, dull and opaque, and is separate grains.

As for the Calcium hydroxide, besides the masons lime (hydrated lime or slaked lime), this chemical is also available as pickling lime which may be available in the grocery store in 1 pound bags. Look for Mrs. Wages pickling lime. It's around $3.90 a pound online direct from Mrs. Wages Store.
As Irons stated above, you could also make the Calcium hydroxide from many sources of Calcium carbonate. Calcite, aragonite and vaterite are pure calcium carbonate minerals. Industrially important source rocks which are predominantly calcium carbonate include limestone, chalk, marble and travertine, tufa, and other rocks. Some biological sources of Calcium carbonate include eggshells, snail shells and most seashells including oyster shells which can be purchased as a calcium supplement for chickens.

So, we have Calcium carbonate, CaCO3, and want to make Calcium hydroxide, Ca(OH)2, from it. First you will heat the carbonate to form Calcium oxide, CaO. This releases carbon dioxide on heating, called a thermal decomposition reaction, or calcination, (to above 840 °C (1544 °F) in the case of CaCO3), to form calcium oxide, commonly called quicklime, with reaction enthalpy 178 kJ / mole: 
CaCO3(s) → CaO(s) + CO2(g) 
Next, if you mix this Calcium oxide with water, it produces heat energy by the formation of the hydrate, calcium hydroxide, by the following equation:
CaO (s) + H2O (l) ↔ Ca(OH)2 (aq) + heat


As it hydrates, an exothermic reaction results and the solid puffs up. The hydrate can be reconverted to quicklime by removing the water by heating it to redness to reverse the hydration reaction. One liter of water combines with approximately 3.1 kilograms (6.8 lb) of quicklime to give calcium hydroxide plus 3.54 MJ of energy.

Going back to Irons' original recipe, we want 1 cup of this Calcium hydroxide. Now, why does most of the world use the metric system? A bit of research (PDF file) shows that 1 cup of powdered Calcium hydroxide weighs 96 grams. But we are starting with Calcium oxide. That only weighs 72 grams per cup of powdered material.

I'm not a chemist (unlike Irons) so I might really mess this up but let's give it a shot.

CaO = 56.0774 g./mol.
H2O = 18.01528 g./mol.
And
Ca(OH)2 = 74.09268 g./mol.

Rounding things off, that should mean that 56 grams of Calcium oxide plus 18 mL of water would give 74 grams of Calcium hydroxide.

We want 96 grams (or 1 cup) of Calcium hydroxide so:

56/X = 74/96 or X=about 73 grams of Calcium oxide plus 23 mL water should give us the 96 grams of Calcium hydroxide.

Wouldn't it be much easier to just buy the lye drain cleaner? What fun would that be? This is caveman chemistry right?

Back to the recipe. We wanted that Calcium hydroxide mixed to a slurry in 1 pint of water. 1 pint = 473.176 mL plus our 23 mL gives us 496... Let's say 500 mL of water should be close enough for a caveman.

Are we having fun yet? Want to keep going?

Baking soda decomposes with heating to form Sodium Carbonate, Carbon dioxide, and water vapor.

2NaHCO3(s) + heat ---> Na2CO3(s) + CO2(g) + H2O(l)

NaHCO3 = 84.0066 g./mol. X2 = 168.0132 grams
Na2CO3 = 105.9885 g./mol.
CO2 = 44.01 g./mol.
H2O = 18.01528 g./mol.

Rounding things off again gives us 168 grams of baking soda should make 106 grams of Sodium carbonate and the carbon dioxide and water disappears so we won't worry about them.

We want 1 cup (221 grams) of Sodium carbonate so:

168/X = 106/221 or X=about 350 grams of baking soda should give us the amount of Sodium carbonate we need once we heat it to remove the CO2 and H2O.

This means we should need around 1-1/2 cups of baking soda to make our 1 cup of Sodium carbonate.

Now that we made our chemicals, all we should have to do is follow Irons' original directions to make the Sodium hydroxide we originally wanted.

Ca(OH)2 + Na2CO3 → 2NaOH + CaCO3

Dissolve a cup of Sodium Carbonate in a half gallon of water. 
Mix a cup of Calcium hydroxide in a pint of water to make a slurry. 
Pour the slurry into the Sodium Carbonate solution while stirring.
Allow the resulting Calcium Carbonate to precipitate out. 

This is the classic way of making NaOH (and KOH). You need to use fairly dilute solutions to get it to work. It relies on the fact that Ca(OH)2 is a lot more soluble than CaCO3.

Ca(OH)2 is not very soluble in water but it is much more soluble than CaCO3, so it does work.

For testing purposes, we could scale this whole recipe down to a more manageable size considering we have to start from rocks.

1 gram Calcium oxide + 7 mL water to form the slurry and
3 grams Sodium carbonate + 26 mL water

This won't give very much sodium hydroxide but you should be able to prove the process works. You should be able to heat enough Sodium carbonate (limestone) chips using a torch to get the gram you need for this test and the 3 grams of Sodium carbonate should be much easier and faster to make than the cup called for in Irons' recipe.

When you have made this tiny amount, a drop or two on a piece of aluminum should bubble hydrogen gas if it worked. Next, you can scale it back up and make more or just go buy a pound of lye drain cleaner knowing that you could make it you had to.

How's that for caveman chemistry? 

So far my personal experiments with this process have made somewhat weak lye. I'm not sure if my calcium carbonate wasn't heated long enough to fully turn it into calcium oxide or if it is diluted with enough water to only make a weak solution of sodium hydroxide. It does react with aluminum but not as fast as I expected. This homemade lye has not been tested yet to see if it will remove solder mask from circuit boards but the process of going from basically rocks to a solution of lye was interesting enough to try even if you can still buy the sodium hydroxide.


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## Irons (Mar 25, 2014)

You just made Caveman First Class. :mrgreen: 

Actually, the reason for this thread, in the first place, was that Sodium and Potassium Hydroxides are not as easy to find as one might think. Thanks to people who make drugs, the DEA classified them as chemicals used in drug production, so most stores quit carrying them. There's nothing illegal about purchasing them, just potentially more hassle. I buy mine online cheaper than I could get them at the local supermarket.

I like to think that there isn't much we can't make on our own, if sources of chemicals become scarce. It's definitely cheaper and less labor intensive to buy them if you can.

Heating Sodium Carbonate to drive off the Carbon Dioxide is probably the easiest route. If one leaves Sodium Hydroxide exposed to air, it will react with Carbon Dioxide in the Air to form Sodium Carbonate. At the Supermarket, Sodium Carbonate is less than a $US dollar per pound.


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## Tub Buster (Apr 8, 2014)

Fuse potassium hydroxide and manganese dioxide and make KMnO4. Might need some chlorate.


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