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KOH(and finally biodiesel) from potash?

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KOH(and finally biodiesel) from potash?

Unread postAuthor: john bunsenburner » Tue Jan 06, 2009 10:36 am

Ok a few months ago we cut down a large hazel, i ran out of space for the logs and leavens in my gargae and so after filling every available space with wood decided to burn the left overs. I finished with about 2kg of ash which i mixed with sand then i ran water through it to extract Potassium hydroxide(KOH) i got about 1-2liters of yellow liquid which i have stored in sterile glasses in my "chemicals safe". Today i had some spare time and after nearly getting frost bite by playing with canned air i decide to check somethings on my lye i found the following:

Ph of 11
Flame test was intense yellow/ornage, as for sodium...

My questions are the following:
1. I was supposed to get KOH but the flame test said something totally different, what did i make here?
2.Why is it yellow, is that some sort of pigment?
3. Can i boil of the water to get a stronger lye?
4. What did i do wrong, why did i not get KOH?
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Last edited by john bunsenburner on Tue Jan 06, 2009 2:09 pm, edited 1 time in total.
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Re: KOH from potash?

Unread postAuthor: JohnnyBOOM » Tue Jan 06, 2009 11:27 am

john bunsenburner wrote:1. I was supposed to get KOH but the flame test said something totally different, what did i make here?

Both NaOH and KOH will be present in wood ashes. From Wikipedia on potassium --> "In a flame test, potassium and its compounds emit a pale violet color, which may be masked by the strong yellow emission of sodium if it is also present. Cobalt glass can be used to filter out the yellow sodium color."

john bunsenburner wrote:2.Why is it yellow, is that some sort of pigment?

Dirt from the sand perhaps?

john bunsenburner wrote:3. Can i boil of the water to get a stronger lye?

Sure. Just make sure you don't expose your KOH/NaOH mix to air. It will react with CO2 in the air and form sodium/potassium bicarbonate. (They used lye in the origional space missions to "scrub" CO2 from the air because of this property)

john bunsenburner wrote:4. What did i do wrong, why did i not get KOH?

Doesn't look like you did anything wrong to me. Perhaps you could try filtering it again to get rid of the yellow contaminant?
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Unread postAuthor: john bunsenburner » Tue Jan 06, 2009 11:34 am

Ok the yellow is not from the sand i filtered that seperately to check and its clean. I have never heard of that property of these hydroxides, i have worked with them and had them in contact with air without a problem...it it only like that when heated?
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Unread postAuthor: JohnnyBOOM » Tue Jan 06, 2009 11:54 am

As far as I know, Na and K hydroxides both react with atmospheric CO2 to form bicarbonate salts. If you look them both up on Wikipedia, this mechanism is described.

Edit: I was just reading this website about extraction of lye from wood ashes: http://journeytoforever.org/biodiesel_ashlye.html, and they describe the product as a brownish liquid. They don't explain what the "brownish" color is from, but perhaps what you have made is normal?
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Unread postAuthor: john bunsenburner » Tue Jan 06, 2009 12:06 pm

So i have to boil it of in an innert atmosphere, i knew this would happen some time, what gas do you recomend, will n2 do?
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Unread postAuthor: JohnnyBOOM » Tue Jan 06, 2009 12:29 pm

I don't think you have to go to any extremes while boiling since the water vapor will displace any atmospheric CO2. Just make sure to store the product in a sealed container to protect it from air.
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Unread postAuthor: john bunsenburner » Tue Jan 06, 2009 12:37 pm

ok, i boiled 10ml and got soem wierd yellow powder, i left ti in the evaporatign dish so it most probably carbonated(or what ever you call it) i only got very little powder, i wa swondering one thing: to make biodiesel can i aslo use lye in solution?
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Unread postAuthor: jimmy101 » Tue Jan 06, 2009 12:53 pm

The yellow really isn't surprising. The wood ash contains basically everything that was in the wood that isn't combustable. In addition, since wood burning is rarely complete, you've got all kinds of "stuff" left over from partial decomposition of the various components of the wood.

Add water and a fair amount of that other "stuff" will get dissolved, giving the yellow color.

The flame test for sodium is much more sensitive than is the flame test for potassium. Even if you've got 99%K+ and only 1%Na+ is would think you would still get a positive flame test for Na+.

The pH of 11 suggests that the solution is about 0.001M hydroxide. Assuming it is mostly KOH (mw=56.1g/mol) that means it is about 0.056 gram per liter.

You can boil off some of the water. As long as the solutions is boiling that will tend to purge it of any CO2 (H2CO3) that it may have picked up.

There are a couple of things that might get rid of the yellow color. Try adding charcoal or graphite and stirring the mixture for a while. Filter (or let settle and decant) to get rid of the charcoal. If the yellow color is mostly from organics then the charcoal may remove them. If the yellow color is from other salts then the charcoal won't help much.
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Unread postAuthor: JohnnyBOOM » Tue Jan 06, 2009 12:54 pm

You can test to see whether is has become (bi)carbonate by checking the PH again. Lye has a much higher PH than sodium or potassium bicarbonate.

I'm not familiar with making biodiesel. :( Although I'm sure there are many good resources out there. I think the link in a previous post even had some detailed instructions for making it. Good Luck! :D
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Unread postAuthor: john bunsenburner » Tue Jan 06, 2009 2:08 pm

ok, though i am a little conserned about having only .6grams a liter. i am not sure that is really worth the trouble...One more question: i have made biodiesel from methanol but my parents dont like me using it so i am stuck to making ethanol :evil:. Does some one have experience with making ethyl esters(bio-diesel from ethanol)? I will be boiling **** for the next few days, one last question: what can i cover the .6grams of KOH with to prevent carbonation, would mineral oil work?
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Unread postAuthor: JohnnyBOOM » Tue Jan 06, 2009 2:44 pm

An air tight container should be just fine.
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Unread postAuthor: john bunsenburner » Tue Jan 06, 2009 2:54 pm

i am not sure about boiling 1liter down to .6grams in an air tight container...
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Unread postAuthor: JohnnyBOOM » Tue Jan 06, 2009 4:26 pm

I meant for post processing storage. :)
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Unread postAuthor: jimmy101 » Tue Jan 06, 2009 7:18 pm

john bunsenburner wrote:one last question: what can i cover the .6grams of KOH with to prevent carbonation, would mineral oil work?

In the dry state it won't "carbonate", it'll hydrate first.

Water + stong base + co2 --> water+ slightly weaker base + HCO3-

So, a water solution of the strong base will pick up CO2 fromthe atmosphere.

Dry NaOH and KOH are both pretty hygroscopic; they absorb water from the atmosphere. I believe KOH is also deliquescent; it'll absorb so much water from the atmosphere that it'll turn into a puddle.

If you get it dry then any tightly closed container will work fine, you don't need to cover with oil. Perferably you don't want a 4L container for 1g of solid.

Making the KOH yourself is pretty cool. But if you really want to make biodesiel you might consider just buying the KOH. Cheapo powdered drain cleaners are often pretty much pure KOH or NaOH. IIRC, more $$$ ones like Drano also contain aluminum pellets.
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Unread postAuthor: john bunsenburner » Wed Jan 07, 2009 12:08 pm

i swear i feel like i lived on mars at times: in switzerland we dont have those nifty little things you do: amonium nitrate is mixed with tons of different stuff to make it useless as an oxidizer. We dont have ammonia in our soaps or cleaning things, nor do we have koh or naoh in our drain cleaners instead we have a hep of differnt compounds that do crap with our plugged sinks so we call a "specialist" who then takes out 20different instruments including a bulk tank of nitrogen to blow out the dirt from our drains into the suwage system which them get plugged so the ""specialist" has another job and every one is happy...with the exeption of a handful of people like me :evil:

But my parents decided that they should hire a chemistry tutor(hey its suprising my house is still in the place where it was built) for me, i will then convince him that making biodiesel is a great idea(on average the answer to anything in switzerland is no: example: my dad was arrested for blowing his nose while driving, a ticket was not eanoth they wanted to take away his lisence, he got of the hook but still: ARRESTED FOR BLOWIGN YOUR NOSE) and make biodiesel with him... :roll: :roll: :roll: :roll: :x :evil: :(

I will still try to make some KOH just to see if it works!!!
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