quote:

Originally posted by Tilly:
Hello Jon

The "Standard" reprocess is 1g NaoH/1.4g KOH mixed into 50ml methanol per litre of washed and dried biodiesel and 1g NaOH/ 1.4g KOH mixed into about 35ml methanol for unwashed biodiesel.

quote:

Originally posted by johno:
In theory the concentrated methoxide should be added second, to the initial mix of oil and straight methanol. This is to avoid exposing parts of the oil to excessive lye concentration, which would locally over-react some of the oil, reducing yield and increasing soap. The methanol needs to be present when the NaOH/KOH-hydroxide meets the oil. This is also the theory that indicates it is "better" to slowly add methoxide over a period of time, allowing the concentration to gradually approach the ideal level, without overshooting locally.
In practice it may make less difference because batch mixing operations are never homogeneous until they've run for a while (bad for us), and the reaction isn't instantaneous (good for us). When I do batches, I add the methoxide all in one go, with quite good results, but it's still got 20% methanol.