A friend at the University of Oregon sent along this quick test to check on the conversion percentage of Biodiesel, and thought I'd pass it along.

In a 300ml glass burette mix 225 ml Methanol with 25 ml of biodiesel. Stir GENTLY. Let settle and measure ANYTHING that falls to the bottom of the column. 2.5 ml = 1 percent unreacted oil. So a "slime" layer 5 ml thick equals a 98 percent conversion.