Author Topic: Potassium hydroxide (Read 99 times)

shakti · « **on:** May 01, 2009, 02:57:25 AM »

I read somewhere (which i now cannot find) that you could heat potassium carbonate with something else to get potassium hydroxide. I'm able to source potassium carbonate from a pottery supply house but the KOH i'm having trouble finding OTC. If anyone knows a specific brand of KOH or knows the reaction, it would be much appreciated : )

Vesp · « **Reply #1 on:** May 01, 2009, 03:29:31 AM »

I've heard rumors that calcium hydroxide and potassium or sodium carbonate in solution will precipitate calcium carbonate and leave potassium hydroxide, or sodium hydroxide in the solution, which would later be purified. I'll try to find a reference later if you are unable too.

Also electrolysis would probably work, though I don't know if it would be worth it.

Sedit · « **Reply #2 on:** May 01, 2009, 07:08:53 AM »

take it wil a grain of salt because i dont feel like trying tonight,,,

what vesp said is correct. it appears in most old synthesis for NaOH from elemental chemicals....

pottasium wont be any different...

fuck I hate being so simple and half retarted but theres your infor if you need more ill try to edit it tommow when the bday party booz warez off.

shakti · « **Reply #3 on:** May 01, 2009, 03:00:23 PM »

Thanks guys, i found it this morning on wikipedia of all places

I guess my brain wasn't going to process anymore information last night. But it said if one were to boil potassium carbonate and calcium hydroxide (quicklime mixed with water), KOH would remain in the solution and calcium carbonate would precipitate off. Then you just filter and reduce the liquid

Satan · « **Reply #4 on:** May 01, 2009, 09:28:18 PM »

As a little kid I did something similar, but using Na₂CO₃, made NaOH.
If you want to get rid of impiurities such as Ca(OH)₂, there is simple purification:

"Take 100g of raw KOH, and boil it in 350ml of 95% ethanol until it dissolves. Let it stand
until all fine particles of Ca(OH)₂ sink to bottom, decant and evaporate ethanol."

Translated from Supniewski-Inorganic Preparations.

Vesp · « **Reply #5 on:** May 02, 2009, 08:06:31 PM »

I like that method of purification, it sounds pretty easy to do, I bet once distilled denatured alcohol would work pretty well. I've never boiled away a solution of an alkali hydroxide, but it seems like it might be difficult or slightly dangerous. I would imagine small chunks of the dehydrating material would pop up and out of the heating container. I'd be careful.

Sedit · « **Reply #6 on:** May 02, 2009, 08:20:11 PM »

Its not really a problem Vesp. I would't put my head directly over it but its ok as long as you leave some head room and dont boil extreamly hard.

I get all my NaOH anymore by boiling down diluted solutions that they sell now days. Boil it until the bubbles change there look. You will notice that it will want to bump more then the fine bubbles the dilute solutions give. When this happens, you stop seeing steam come from it and trace amounts of crystals on the top then pure it into a pyrex baking pan and on cooling it will solidify into a hard rock. Dont leave it in the flask because it will be a bitch because it is very solid and takes a while to dissolve in water.

Vesp · « **Reply #7 on:** May 02, 2009, 08:23:57 PM »

Ah, but this wouldn't be anhydrous would it be? Seems like it would make doing anything like a titration, etc pretty difficult.

Douchermann · « **Reply #8 on:** May 02, 2009, 09:05:19 PM »

No it certainly wouldn't be anhydrous, but if you just take that brick in the pyrex baking dish, and heat it up strongly, it'll eventually melt and the water will disappear. Remove the heat and stir as it cools down. Do not stop stirring or you're SOL. As long as you do this while there isn't too much humidity, you'll have pretty close to dry. Don't do this in a dish you care about though. Molten sodium hydroxide eats through almost anything (glass, ceramic)

Satan · « **Reply #9 on:** May 03, 2009, 11:32:45 AM »

Its bad idea to dry it this way, it will be contaminated by silicates of potasium.
Best way to do this - dry it in silver bowl over flame for short peroid of time to minimize CO₂
absorption. Stainless stell bowl would probably work too.

Sedit · « **Reply #10 on:** May 03, 2009, 04:45:07 PM »

This is way dryer then commercial hydroxides when you evaporate the solution down.
Stainless steel is a no go because it appears to leach it a little bit and I would rather have silicates instead of metals in it but A silver bowl would be ideal.
Doing it the way I mentioned gets it very nice and I prefer using it over commercial. Making Hydroxides anhydrous is a pain in the ass without alot of equipment. Im not to worryed about the silicates because even though I know there there because of what is done to the bowl the effects are minimal and I would say for every 100 grams you have maybe a few milligrams of silicates if that. Thats acceptable for most uses.

Vesp · « **Reply #11 on:** May 03, 2009, 09:57:10 PM »

I have heard potassium hydroxide can be made from dissolving wood ash in water, and then taking of the liquid fraction. I never thought this was true since it would make a lot more sense that it would be potassium carbonate. However, would it be likely that calcium or magnesium oxide or hydroxide is present in the ash in enough quantity to make a decent amount of potassium hydroxide using this precipitate method? Surely it would be impure and nearly useless, but it seems like it would be possible to some degree now.
Either way, ash is still more useful for fertilizing tobacco and other plants.

Author Topic: Potassium hydroxide (Read 99 times)

shakti

Potassium hydroxide

Vesp

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Sedit

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shakti

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Satan

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Vesp

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Sedit

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Vesp

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Douchermann

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Satan

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Sedit

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Vesp

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