Is it possible to use KOH and NaOH in the same reaction (properly mixed amounts with methanol in separate containers)? Reason I ask is I have been using KOH for bio and although it has some nice advantages (speedy mixture with methanol and liquid glycerol), it seems it makes gravity settling of soaps and leftover glycerol very slow, where as from what I've read on here, NaOH reacted soaps seem to fall and settle far faster. That got me thinking, is there a middle ground I could run by using half of each caustic and speed up settling but also have a thicker, but yet liquid enough glycerol to flow cold? I've had my demethed KOH bio settling for like two weeks now and the soap is just as thick as the day I put it in the settling tank. I understand temperature plays a part in that and considering my tank is unheated and the ambient air temp has been in the 50s, its probably slowing down the soap but I dont see any improvement and was just doing a little thinking.
I have been reading up on the dry wash setups using just hardwood and the idea behind it seems simple and cheap enough, I may just head that way for my bio cleaning. I have an endless supply of quite a few different hardwoods as well.
Yes you can do this, I have done it several times and it does result in liquid glycerol. However if mixed approx 50/50 I'm not sure if it has advantages regarding the settling of soap.
It sounds to me as if you are getting too much soap in there. I have sometimes had a similar thing when just settling after using KOH. If for some reason the soap is a higher % in the glycerol then when settling the glycerol can be run off, leaving sticky brown soap in the bottom cone which is really difficult ( if not impossible) to remove.
At the moment I am using some methanol that is higher water than it should be and I suspect this is what is causing my problem.
Also if you are glycerol pre-treating the oil and the glycerol you are using is very high in soap this can have a 'knock-on' effect with future batches. After the pre-treatment and the glycerol is removed, some of the soap can be left in suspension in the oil.
Sounds like a that might be my problem. I haven't done any tests to tell an actual amount ( just the 50/50 test) but I'm willing to bet my PPM is just really high to begin with.
Nice to know that you can use two caustics though. That means I can save more money per gallon considering NaOH is noticeably cheaper than KOH.
I'm still learning a lot about brewing and one thing that I find different answers on and would like some clarification on is about my vent for my water heater reaction tank. I've had it open and vented outside during my whole brewing time. I have read that you should close it off as soon as your methoxide mixture is added and somewhere else I read to leave it open. Kind of freaks me out to close off my whole system while a chemical reaction is going on inside it. Don't want anything to explode or rupture. Some clarification would be nice.
ouchfoss, the main thing is to be aware of the methanol fumes, they arn't nice. I react at ambient temperature so any fumes are minimal. My processor (220 litre plastic conical) has the top on during the reaction and there is a 6mm vent hole in the top.
As long as your processor is vented externally I would leave it open, any methanol evaporation that would effect the reaction would be very minimal.
My vent goes about 20 feet thru a wall and is vented outside. No methanol fumes are ever in my area around me while the tank is mixing.
I kinda figured the methanol evaporation would be minimal once the heat was off and the mixer is going but I read on here in one post about shutting that valve once the methoxide was added otherwise a full reaction won't happen.
There has been an absolute wealth of inaccurate information posted in the past about the "massive" loss of methanol out of an open vent pipe.
As Dgs advises and you are aware of, once the heat is turned off there will be virtually nil loss of methanol out of a properly constructed vent pipe.
And of course you do not want to close the vent while heating because that will lead to pressurization of the reactor.
Dgs and Tilly, thank you! Glad to know now because I was planning on trying it with the valve closed on my next batch but the whole idea of it just sounded too scary to try so I figured I'd ask on here first since I was unsure. Makes sense now that I think about all the people in the past who have made perfect batches with the same amount of methanol using open topped 55 gallon drums.
KOH has more water than NaOH - the water is the impurity - and due to hydrogen bonding is slower to settle. BD itself is mildly polar.
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