I made jelly, why?

[Grael]

Alright, recently I got me a biodiesel kit and I have been making small batches with used oil. The first batch I made was with new oil, it turned out fine. Then I made a few batches with used oil, the first one went great, but now when I make another batch using the same oil from the same pail, when I add the methoxide (Lye dissolved in methanol) to the oil, within about 30 seconds to a minute the whole thing turns to jelly. WHY is it doing this??!!?? Water in the oil making soap? I dont get why it would do this.

Help!

[biobill]

M.O.N.
  Presumably you did the titration properly. Was the oil reasonably warm? Being vigorously stirred? Methoxide added gradually? I've had batches gel from the oil being too cold and from dumping the methoxide in too quickly. In both cases I added heat and beat the piss out of it, and was able to get a good reaction. Sure got the heart rate up though. I make 150gal batches and don't know what I'd do with that much soap         Bill

[Grael]

The oil is at room temp. I did add the methoxide all at once since, so maybe that was my problem. as for the titrations, I dont like the indicator solution that came with the kit, it says between pH of 8-9, 8 is blue and 9 is a blueish green not a real noticeable difference, what indicators do you use? would a electronic one work?

[biobill]

M.O.N.
  I'd bet dumping the methoxide in caused your troubles. With continued vigorous agitation you might have saved it, but who knows? It's hard to stir the glop. I don't know how your "kit" is set up but I use COLORPHAST test strips to check the oil/isopropyl solution. Way better than standard litmus paper, they've got four color blocks that change shade and allow for very accurate readings.
  What you have is probably good enough though. You've got a bit of wiggle room with the ph. 8-9 should be fine.

[Grael]

Yep that was my problem, it turned liquid again with good separation I have "hydrion one drop indicator solution" basicaly it is a little drop bottle, and has a range of 1-11, I put 3 drops in the titration. Would an electronis pH tester work? Or would it have to be in an aqueous solution (in water) to work? Also, after I add the methoxide, mix then let settle, I get a thin scum/skin on top. what is it? is it telling me of something bad happening? I just skim it off...

I'm still learning so I'll have alot of questions...

[biobill]

 The skin seems to be some kind of soap compound - may be related to traces of water but I don't know for sure. Doesen't seem to hurt anything, I just skim and chuck. No idea about the electronic tester but you might find the answer here:
http://biodiesel.infopop.cc/eve/forums
More than you ever wanted to know about biodiesel.    Bill

[Grael]

Thank you.