[thcipriani]

I just had a few questions regarding the use of Potassium Hydroxide (KOH) in mead. I've seen this suggested in multiple sources:

http://www.bjcp.org/mead/Mead_Study.pdf
http://www.ahaconference.org/presentations/2008/KrisEngland_NHC.pdf

Really these questions are more requests for confirmation that I'm going about things correctly and that I'm not a total boob.

In any event - what is a reputable source of KOH? I tried ordering 500 g flakes from Cynmar and they informed me that they don't sell chemicals to individuals. Since then I've located this source which is food grade and it's about 4x as much as Cynmar was selling for the exact same price:

http://www.amazon.com/Grade-Devil-Potash-Potassium-Hydroxide/dp/B0039CIQTI/ref=pd_sbs_auto_2

I did notice in that picture on Amazon that it says 'minimum 90% KOH' on the bottle - which begs the question, what's the rest and is it OK to add this?

Also a quick question about using the stuff if/when I get it. It's been a while since chemistry - since the molecular weight of KOH is 56.1056g/Mol, to get a 2M solution I would add 112.211g to a container and then add distilled water until the total volume reaches 1 Liter and the subsequent solution is KOH at a concentration of 2M, correct?

If that is correct, does this method scale in a liner way (i.e. if I mixed a 500mL solution with 56.1056g of KOH would that also have a molarity of 2? Or 28.0528g in a 250mL solution?).

After I get a 2M solution of KOH can I just add 10mL of directly to my fermenter or is there an intermediary step?

Thanks in advance for the responses.

[euge]

KOH is caustic. Be careful! I'm curious as to why it aids in fermentation.

[gordonstrong]

It raises pH.  Helpful if you find your pH in the low 3's and still expect the yeast to do something.

[euge]

It raises pH.  Helpful if you find your pH in the low 3's and still expect the yeast to do something.

Ahh... That makes sense. So one would need to check the pH to make sure, and not just blindly add KOH.

[thcipriani]

Ahh... That makes sense. So one would need to check the pH to make sure, and not just blindly add KOH.

That's another good question actually. Both of the sources I posted left me with the impression that KOH was a mandatory addition along with the staggered nutrient additions. Is my inference correct or would I need to take pH readings at 24, 48 and 72 hours and only add KOH if the pH is below 3? Or would I only need to take a pH reading if my final gravity was greater than I wanted and I suspected pH to be to blame?

It raises pH.  Helpful if you find your pH in the low 3's and still expect the yeast to do something.

I saw that Kristen England posted in the 'Jim's Beer Kit' forum that pH was only half of the reason that he used KOH. The quote from the forum is brief and unexplained in the thread:

Potassium (K) really makes the yeast healthy

If anyone cares to expand on why KOH is more desirable than K2CO3 or the like that'd be really helpful information - is KOH's ability to raise pH just greater?

Thanks guys.

[BrewArk]

You don't want to add KOH without checking the pH first.  When you do add it, add it in small doses and monitor your pH while you do.  The potassium is beneficial to live yeast but will not help dead ones.  I'd lean towards the carbonate myself.  It would change the pH more slowly.  There is potassium in the Fermaid if you are adding that, so you may not need to add either of these to get a good mead.

-Rick

[tschmidlin]

The potassium is beneficial to live yeast but will not help dead ones.

Hilarious! 

[thcipriani]

I'd lean towards the carbonate myself.  It would change the pH more slowly.

IIRC, K2CO3 is a weak base and only partially dissociates into K2+ and CO3- and that dissociation is based on several factors including the current pH of the solution and only the CO3 can accept an H+ ion raising the pH (lowering the acidity) while KOH is a strong base that fully ionizes in solution contributing 1M of OH- per 1M of KOH solution raising the pH (lowering the acidity) because of the hydroxide contribution.... I think....

Please correct this if I'm mistaken - I'm no scientist and the information above was pieced together from Wikipedia and Google.

Based on my strong Google skill it seems it would take more K2CO3 than KOH to achieve the same effect on pH.

The only reason I mention any of this is that the BJCP mead guide that I linked to above says:

Excess carbonate can also impart a metallic or soapy note in the flavor. Don’t use more than 5 grams of potassium carbonate when adjusting pH of the must.

Anyone have any experience with this or nuggets of chemistry knowledge to drop? Is 5g of K2CO3 enough to achieve the desired effect? Also, why does the BJCP mead guide have the above quote and also list:

6g K2CO3 or 150ppm KOH (30ml of 2M solution)

as one of the ingredients of the basic mead making process on page 86 of the pdf? Did it actually mean, "Up to 6g K2CO3 based on pH shift during fermentation"?

Edit: 8/31/10 - from lowering pH to raising pH - cause of my dumbness...

[punatic]

Sorry to be late to the party, but if you plan to make a 2M KOH solution from flake KOH do so with caution!  Mixing KOH with water causes a highly exothermic reaction (it gets really hot).  Be sure to wear eye protection, face protection and gloves!

Mo bettah to buy a KOH solution than mix one - if you can.  Unless you have lab bench experience.  I do, but I still prefer to buy my KOH and NaOH in liquid form.

[thcipriani]

I have lab-bench experience in the sense that I was the TA who set up experiments in HS and college - so really I don't have any experience outside of a lab. Do you have any sources from pre-made 1Normal Solutions?

[punatic]

In my lab we use 8N KOH for determining calcium hardness in water by titration.  We buy 100mL bottles of 8N KOH from Fisher Scientific.  However. we have a laboratory/business account with Fisher.  I don't think they sell directly to the public.

You might want to look at winemaking suppliers and the like.  KOH is classified as a haz-mat and cannot be shipped via the USPS.  Private shippers will carry it, but haz-mats cost more to ship.

100mL lasts quite a while.  I usually only need 1mL or so to adjust the pH on a 6.5 gallon batch of mead.

With KOH normality, N and molarity M are equal.