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kerkring
01-20-2009, 09:48 AM
I recently started experiments to extract K2CO3 from wood ashes, following the method described by Robert Bartlett in Real Alchemy.

In my first experiment I used 210g of ashes and added about 4L of water. I let the mixture stand for one day and then filtered off the liquid.

The resulting liquid was light yellow in color and was slowly evaporated on a hot plate.

This is a picture of the needle like crystals after the evaporation was complete:
http://a.imagehost.org/0897/500_en_5_dpieerste_exp-kristallen_droogDSC00098.jpg

Ten grams of crystals were recovered. Normally they should have been white though.

Now they need to be purified through deliquescence.

Aleilius
01-20-2009, 02:17 PM
I'm working on a book, and in my book I proceed a bit differently than Bartlett.

Even though wood ashes are already partially calcined, they should be calcined again, but first you need to sift through the ashes to remove any bits of partially combusted wood. After sifting through the ashes, you should recalcine. The calcination temperature should be around 750F - 1000F. This is hot enough to remove most impurities.

Pour the freshly calcined wood ashes into a vessel with water (use approximately 2x more water than ashes) - make sure the ashes are still hot from calcination. Cap the vessel, and then shake it for a few minutes. After shaking you'll need to put it on a burner and then boil it vigorously for a few hours.

After boiling we can let the ashes settle and then decant, or use a filter to separate the ashes from the liquid. I recommend filtering the solution twice to remove any particulate matter that might've made it through the first time. Some filters tend to degrade when filtering highly alkaline solutions, so it may be necessary to add water to reduce the overall alkalinity.

Evaporation is the final step, and after the process is all said and done you should end up with fairly pure potassium carbonate. Of course, multiple recrystallizations may be utilized to produce a highly pure product.

kerkring
01-20-2009, 05:56 PM
I'm working on a book, and in my book I proceed a bit differently than Bartlett.

Even though wood ashes are already partially calcined, they should be calcined again, but first you need to sift through the ashes to remove any bits of partially combusted wood. After sifting through the ashes, you should recalcine. The calcination temperature should be around 750F - 1000F. This is hot enough to remove most impurities.

Pour the freshly calcined wood ashes into a vessel with water (use approximately 2x more water than ashes) - make sure the ashes are still hot from calcination. Cap the vessel, and then shake it for a few minutes. After shaking you'll need to put it on a burner and then boil it vigorously for a few hours.

After boiling we can let the ashes settle and then decant, or use a filter to separate the ashes from the liquid. I recommend filtering the solution twice to remove any particulate matter that might've made it through the first time. Some filters tend to degrade when filtering highly alkaline solutions, so it may be necessary to add water to reduce the overall alkalinity.

Evaporation is the final step, and after the process is all said and done you should end up with fairly pure potassium carbonate. Of course, multiple recrystallizations may be utilized to produce a highly pure product.

Thanks, will try it out.

solomon levi
01-21-2009, 08:59 PM
When HCl is added to ashes in solution, bringing the pH down to 1, and then
raising the pH back up to 10.78 with lye or KCO3, one has a precipitate that
is supposed to be m-state. After washing, the precipitate has no bite as
KCO3 would.
It's interesting to think about - how so much precipitate can come
out of an ash that would otherwise be merely KCO3.
I guess one would have to try to get a precipitate from the ash at different
stages of purity to see if the metals are still there, or when/if they disappear.

Aleilius
01-21-2009, 09:14 PM
It's interesting to think about - how so much precipitate can come
out of an ash that would otherwise be merely KCO3.

The composition of wood ash varies. A large percentage is calcium carbonate. Potassium carbonate is only found in relatively small amounts. Wikipedia has an article on this very topic.



http://en.wikipedia.org/wiki/Wood_ash

Wood ash contains calcium carbonate as its major component, representing 25 [4] or even 45 percent.[5] Less than 10 percent is potash, and less than 1 percent phosphate; there are trace elements of iron, manganese, zinc, copper and some heavy metals.[4] However these numbers vary as combustion temperature is an important variable in determining wood ash composition.[3]

Potassium carbonate, or potassium hydroxide is water soluble, and thus will stay in solution. However, calcium carbonate is not water soluble. When muratic acid is added it converts our insoluble calcium carbonate, into a soluble calcium chloride. Now, whenever lye or potash is added the soluble calcium chloride is thus converted to insoluble calcium carbonate/hydroxide. Of course, if m-states sre in the ash, then they will also be precipitated along with the other insoluble carbonates/hydroxides. If we can't detect m-state matter, who's to say it's there or not?

I'm not saying this is the full explanation, but this is the explanation modern science would give.

theFool
01-22-2009, 08:01 PM
I follow a recipie from the book "Caveman Chemistry", Kevin M. Dunn (http://www.cavemanchemistry.com/cavebook/). Here it is step by step. Note that Kevin removes the least soluble carbonates by filtration, just before K2CO3 crystallizes and also calcines the final product to make it white (driving off unburnt carbon).

My attempt was the following:

1. Ash from 5 wood logs was mixed with water in a bucket.
2. It was left for a day to settle and the water was siphoned out. It had a yellowish-orange tint.
3. Water was evaporated down to ~150ml and the least soluble salts coagulated.
4. The insolubles were filtered out.
5. Evaporation continues till dryness.

Hm, how do you upload an image to this new forum?


Now they need to be purified through deliquescence.

Try to purify them by calcination. I got mine much whiter through this process. Also I 've observed that when the initial ash-water solution is left to settle for a long time (~ a week), the water comes out almost transparent, (almost no yellow color) and the resulting carbonate pretty pure and white.

kerkring
01-23-2009, 07:38 AM
I
Hm, how do you upload an image to this new forum?


I went here http://www.imagehosting.com/ and uploaded my images there and then pasted in the links I got.

theFool
01-23-2009, 10:30 AM
I went here http://www.imagehosting.com/ and uploaded my images there and then pasted in the links I got.

Thanks for the info. Here are my pics. At the first, there is the solution before the final coagulation (step4) and at the second the finished product I got from the above process(step5). Observe that while the color of the solution is orange-brown, the final carbonate got pretty clear probably because I left it on the heating pad for sometime.

http://img530.imageshack.us/img530/8868/karb1ot7.jpg

http://img217.imageshack.us/img217/9228/karb2et8.jpg

kerkring
01-23-2009, 01:23 PM
My solution had the same color also.

Aleilius
01-23-2009, 11:37 PM
My extraction liquid had the slightest golden tinge to it, but otherwise it was fairly clear and pure.

Calcination of the impure potash is also quite acceptable. Just don't get it too hot or you may accidentally convert the potassium carbonate to potassium oxide.

Riventree
01-07-2013, 05:23 PM
Your pardon, all for replying to such an old thread, but I have some knowledge of this matter. The pink/brown color in potash made from lixivated ash is almost certainly a substance called "muriate of potash", which is also the mineral Sylvite. Note that sylvite also comes in brown/pink coloring. It may be separated from potash by careful temperature control and completely saturating the solution. Or alternately you may add common salt to a saturated solution of potash, precipitating soda ash rather than potash, and leaving the rest of the solution as waste.

The pinkish brown color is actually an excellent sign if you desire potash composed primarily of pearl ash rather than soda ash... it shows that the "pot" in potash is dominant. A pure white color probably means mostly soda ash and also the natively white common salt. (The impurities normally align with the main product)

thrival
02-07-2013, 04:18 AM
Not so easy to make potassium oxide, the melting point of potassium carbonate is 1,636F (891C)