[schmidling]

After going through a lot of trouble making "lye" from wood ash, I now learn that it is actually Potassium carbonate and not hydroxide as stated in just about every discussion I could find on the subject.

I have also been told than I can convert one to the other by adding Calcium hydroxide to the Potassium carbonate but it's not clear how to do this and in what proportions.

Any help will be appreciated.

One other question... Calcium hydroxide is also called slaked lime which is defined as lime with water added.  The C h I just purchased is a dry powder so where does the water fit in?

Thanks,

Jack Schmidling
Marengo, Il

[billnotgatez]

http://en.wikipedia.org/wiki/Soap_making#Soapmaking

http://www.alcasoft.com/soapfact/history.html

http://www.cavemanchemistry.com/projects.html
http://www.cavemanchemistry.com/cavebook/chsoap.html

http://www.ehow.com/how_5700913_make-potassium-hydroxide.html

These sites mention potassium and sodium hydroxide.
I see other sites where they mention carbonate instead of hydroxide
but the WIKI article only mentions the carbonate as a function of the curing process

The EHOW article says you get the carbonate in the wood ashes
but after leaching and heating it changes to hydroxide

Make potassium hydroxide from wood ashes. The pioneers leached the ashes from their wood fires and used the potassium carbonate they contained to make soap. Potassium carbonate, if heated strongly, gives off carbon dioxide gas, producing potassium oxide. Reacting the oxide with water produces potassium hydroxide.

I see no mention of calcium hydroxide in either WIKI or EHOW

I suppose I could search more but time escapes me.

[Arkcon]

You should be able to find some recipes for using homemade lye.  Yes, it may contain a variety of potassium salts, but you should find a recipe that involves evaporating the homemade lye to dryness and roasting it to potassium oxide.  On you've done that, and you mass it carefully, you can follow recipes with care, or try to use stoichiometry to add just the right amount of fat.  The potassium oxide reforms lye when mixed with water.  But for safety's sake, you should follow recipes as written.  You don't want to get sloppy with strong base, or fail to consume it all in the final soap product.

[schmidling]

The Calcium hydroxide came as an afterthought in an email from Kevin Dunn (Cave Man Chemistry).  I have both of his books and a pretty good handle on contemporary "hand crafted" soap making.  However, as a hobbyist, I tend to do things the hard way for the learning experience.

I have commercial lye of both types but want to go through the wood ash drill.  Now that I know that my home made lye is not actually Potassium hydroxide, I think it might explain why I have been unable to make clear liquid soap with it.  It always comes out some shade of cream.

Dunn suggested "titrating" my lye with a solution of Calcium hydroxide until it stops precipitating Calcium carbonate.

I don't understand this nor do I understand what a solution of CH is as it is more or less insoluble in water.

I hate to keep asking him dumb questions so I am trying to work it out myself but getting nowhere.

Jack

[billnotgatez]

I found some links that discuss making soap with calcium hydroxide
I did not look at them yet

But look at this
http://en.wikipedia.org/wiki/Calcium_hydroxide
Calcium hydroxide
Solubility in water
  0.189 g/100 mL (0 °C)
  0.173 g/100 mL (20 °C)
  0.066 g/100 mL (100 °C)

http://en.wikipedia.org/wiki/Potassium_hydroxide
Potassium hydroxide
Solubility in water
 97     g/100 mL (0 °C)
121     g/100 mL (25 °C)
178     g/100 mL (100 °C)

If you saw my EHOW quote below what you have with the wood ashes is the precursor to lye.
K₂CO₃ + heat = K₂O + CO₂
K₂O + H₂O = 2KOH


I think what Dunn is suggesting is basically swapping the hydroxide for the carbonate between pickling lime and wood ashes (Calcium hydroxide and Potassium carbonate) to get the final lye (Potassium hydroxide) and Agricultural lime (Calcium carbonate).

http://en.wikipedia.org/wiki/Calcium_carbonate
Calcium carbonate
Solubility in water
   0.0013 g/100 mL (25°C)

http://en.wikipedia.org/wiki/Potassium_carbonate
Potassium carbonate
Solubility in water
112     g/100 mL (20 °C)
156     g/100 mL (100 °C)

We will assume that the reaction Dunn is suggesting is favored.

Never the less just some heating of the soluble components in wood ashes and then adding water should also give you lye.
That's is what EHOW is suggesting.

[schmidling]

If I understand correctly, the runoff has to be reduced to a solid in order to burn off the CO2?

I have reduced mine to 30 Baume which is about 28%, a convenient concentration for soap making.

Dunn was suggesting a method of determining how much Calcium carbonate it would take to convert the solution to the hydroxide.  This seemed like an easier method until I discovered that Calcium hydroxide does not dissolve in water and I got lost.

Jack

[billnotgatez]

-you said

Dunn was suggesting a method of determining how much Calcium carbonate it would take to convert the solution to the hydroxide.  This seemed like an easier method until I discovered that Calcium hydroxide does not dissolve in water and I got lost.

-did you mean to say
Dunn was suggesting a method of determining how much Calcium hydroxide it would take to convert the solution to the hydroxide.  This seemed like an easier method until I discovered that Calcium hydroxide does not dissolve in water and I got lost.

-remember I suggested Dunn meant
 swapping the hydroxide for the carbonate between pickling lime (Calcium hydroxide) and wood ashes extract (Potassium carbonate) to get the final lye (Potassium hydroxide) and Agricultural lime (Calcium carbonate).
Ca(OH)₂ + K₂CO₃ = CaCO₃ + 2KOH

------------
I assume you read this
http://cavemanchemistry.com/oldcave/projects/lime/
There he shows calcium carbonate being converted to calcium oxide which then is converted to calcium hydroxide. Later he shows where sodium carbonate is combined with the calcium hydroxide to form sodium hydroxide and calcium carbonate. I assume potassium carbonate will do the same as sodium carbonate in the presence of calcium hydroxide.

----------------
It appears for the WIKI data I posted both Calcium hydroxide and Calcium carbonate are slightly water soluble. The Calcium hydroxide seems more soluble than Calcium carbonate. So the Calcium carbonate would fall out of solution before the Calcium hydroxide.

--------------------

After reading some of the sites that talk about Calcium hydroxide and soap making, I could not easily find where it was used directly in the process. More like an adjunct to lye.

[schmidling]

-did you mean to say
Dunn was suggesting a method of determining how much Calcium hydroxide it would take to convert the solution to the hydroxide.

Yes. Sorry.



>-remember I suggested Dunn meant
 swapping the hydroxide for the carbonate between pickling lime (Calcium hydroxide) and wood ashes extract (Potassium carbonate) to get the final lye (Potassium hydroxide) and Agricultural lime (Calcium carbonate).

Understood.

>I assume you read this
http://cavemanchemistry.com/oldcave/projects/lime/...

Roger.

>After reading some of the sites that talk about Calcium hydroxide and soap making, I could not easily find where it was used directly in the process. More like an adjunct to lye.

That is another issue which is not part of this discussion.

I am trying to convert my mostly Potassium carbonate solution to mostly Potassium hydroxide solution without reducing the former to a solid.

My ref to Dunn was regarding an email and not in his book or any other source I have seen.

His exact words were...

 "If you want avoid boiling away the water from your potash solution, you could "titrate" a sample by adding a lime solution to your potash solution a little at a time until no more calcium carbonate precipitates. You could then scale it up to a larger batch."

My problem is that I don't know what a "lime solution" is and I have to know the exact amount of lime  in this solution to calculate the amount of lime to add to my lye solution to convert it to Potassium hydroxide.

If I add Calcium hydroxide to water all I get is a milky suspension and I don't how to relate that to a solution.

Jack

[billnotgatez]

lime
http://en.wikipedia.org/wiki/Calcium_oxide
Calcium oxide
Solubility in water
1.19 g/L (25 °C)
0.57 g/L (100 °C)
exothermic reaction

The above is for reference.

OK -- I have not made soap from wood ashes and fat.
But I get the idea of how to do it theoretically.
Unfortunately, GOOGLE is not giving up a recipe that is clear cut when discussing your problem.

My impression is that you have a solution that has been extracted wood ash and contains Potassium carbonate, Potassium oxide, Potassium hydroxide (possibly), Sodium carbonate,  Sodium oxide, Sodium hydroxide (possibly).  You can eventually get to lye by further heating to dry powder and then re-hydrating with water. Alternatively, you could take the original wood ash extract above and add calcium oxide (lime). The calcium oxide will turn into calcium hydroxide in the water. Since calcium oxide is more soluble than calcium hydroxide it will dissolve quickly. Before the calcium hydroxide can participate out it combines with the potassium carbonate and sodium carbonate. The result is lye and calcium carbonate which participates out. I can only assume you do this by slowly pouring in calcium oxide (lime) while stirring at room temperature.  Although, it is possible that you can just put calcium oxide in stir it good and wait for the reaction to happen over days. The first method of stirring in does not require you guessing how much Calcium oxide to use, since you can see when it will not take any more before participating out as calcium carbonate. This is my best guess.

Adding lime to water alone will eventually give you a milky look, since it turns into the less soluble calcium hydroxide and there is nothing to react with in the water.

The problem I see is finding consistent common terms for
Calcium oxide
Calcium hydroxide
calcium carbonate
which makes the it confusing.
Lime, quick lime, pickling lime, etc. are not well defined.

Maybe someone else will chime in if you need more help.

[schmidling]

The problem I see is finding consistent common terms for
Calcium oxide
Calcium hydroxide
calcium carbonate
which makes the it confusing.
Lime, quick lime, pickling lime, etc. are not well defined.

You hit the nail on the head.  I suppose to a chemist, the binomials are well defined but as in biology, the common names are a mess.

I saw a video of some guys mixing roasted limestone with water and the reaction was furious with huge chunks dissolving into mud in minutes.  This was a very good demo of slaking lime.

So I took a small seashell and torched it to red heat and dropped it into water when cool and a tiny bubble or two arose which I assumed was just air escaping but not a reaction.  The only thing that happened was that the pH of the water went up which I guess proved the whole idea.

Now my confusion is that hydrated lime seems to be a key expression but that would imply the mud in the video.  I have a bottle of Calcium oxide and one of Calcium hydroxide but they of course are powders.

One is supposed to be hydrated lime by some of the definitions but where is the water?

One presumed that the slaked lime is dried for future use but then it is no longer slaked as the water is gone.

I am sure I am over complicating this but such is the problem of learning chemistry via Google.

Jack

 

[curiouscat]

Now my confusion is that hydrated lime seems to be a key expression but that would imply the mud in the video.  I have a bottle of Calcium oxide and one of Calcium hydroxide but they of course are powders.

One is supposed to be hydrated lime by some of the definitions but where is the water?


One presumed that the slaked lime is dried for future use but then it is no longer slaked as the water is gone.

Slaked lime can be dry.

Lime = CaO
Slaked lime = Ca(OH)2

Ca(OH)2 can be dry or slurried. Very little of it will actually dissolve.

[Wastrel]

Suggestions on ehow to heat potassium carbonate and add water to the oxide should be politely disregarded.  Also causticising is not as easy or complete as caveman chemistry implies, particularly for potassium carbonate.  Fortunately for soap you don't need a pure product.  There is one gotcha if you make your own lime in that you can over-burn (dead-burn? I forget where I read it) limestone, where the silicates form/melt and the product is not porous (ruined) but this should not be an issue if you use a traditional fire to make it.

About the alkali, Wagner's talks about a large inverted conical container with a tap on the base into which ash and between 1/10th and 1/12th of it's mass of lime is placed, together with enough water to slake it.  That amount is not given but it will be in excess of stoichiometric. This is lixiviated until exhausted, producing three grades of soap boiler's lye.  Strong, containing 18 to 20% alkali, Middling strong, containing 8 to 10% alkali and Weak lye containing 1 to 4%.  The latter is usually reused in the next batch instead of water in the lixiviating stage.

The boiling of soft soap commences with a strong lye containing 8 to 10% potash, by which an emulsion if formed, the scum is dashed about with a stick, the beating-stick, and by this means all the alkali is caused to be taken up.  A fresh lye is then added, and the boiling continued, until the soap stiffens on cooling to a clear tough mass.  When the soap contains too much caustic alkali, which can be ascertained by the taste, more oil is added.  The clear boiling now commences, during which excess of water is removed.  To avoid a lengthy evaporation a concentrated lye is employed, and the soap, instead of bubbling up, has it's surface covered with blisters as large as the hand; these blisters are termed leaves.  When the boiling is finished-ascertained by putting some of the soap to cool on a glass plate, from which, if firm, it can be separated-the soap is cooled and stored in barrels.

There is a lot more stuff here but it's quite broad and vague, massive amounts as the type and quality of the fat or oil.  I think this is everything it says about the manufacture of soft (potassium) soap and might be as close to a pre-industrial method as I can find.  Avoid aluminium containers/pans, they will be eaten, and I suggest you use an appropriate indicator instead of tasting.

[billnotgatez]

@Wastrel
Do you have a link that is best for the old wood ashes style of soap making?

[schmidling]

http://www.grandpappy.info/wsoap.htm
@Wastrel
Do you have a link that is best for the old wood ashes style of soap making?

The following are a few that I have collected but they are all flawed in one way or another.

I have made a few bars of passable hard soap from wood ash and lots of decent soft and liquid soap but there is a lot more to it than meets the eye and room for a citizen chemist to sort it all out.

I still have about 500 ml of lye at about 30 Baume for lots more experiments.

Keep in mind that it takes about 1000 lbs of wood to make a pound of potash or 150 kg for my little bottle of lye.  Lots of romantic nights in front of the fireplace thinking about soap?



js

http://www.countryfarm-lifestyles.com/make-lye.html

http://www.countryfarm-lifestyles.com/support-files/soapmaking-how-to-make-soap.pdf

http://www.frontierfreedom.com/index.php?option=com_content&task=view&id=105

http://www.grandpappy.info/wsoap.htm

[billnotgatez]

Please note that it was NOT I (billnotgatez) who posted the link in the quote in the previous post by schmidling.

@schmidling
Thanks for all the links
If anyone else has any they like, please post them.