Jeff;
I use 70% and 90% Isopropyl intercahngably and don't see any difference in the titration results. This is not where you are running into problems.
I think that if I were you, I would be more suspect of my method of doing the titration and my processing of the oil. You talk about using a teaspoon to measure your NaOH. If you do not have a proper scale to measure small amounts of NaOH to process your test batch, how did you acurately measure the tiny amount of NaOH needed when you made your titration solution? Probably your solution is not acurate. And how are you measuring how much solution you are adding to your test sample to get the titration number? Do you have a burette, accuratly graduated syringe, or other way of acurately measuring tiny amounts of the solution. If not, this will throw off your titration number as well. What amount of NaOH are you using as a base amount? (I use 6 grams/liter and get good results.) Once you have your titration number, how are you acurately measuring the NaOH into the methanol? If you are using a teaspoon, this is introducing another inacuracy. You need a good scale capable of measuring small amounts. How are you measuring your methanol and WVO? Do you have some kind of graduated container? What about temperature of the WVO? Do you check it with an acurate thermometer? If it's to hot it can boil off the methanol before the reaction takes place. Too cold, and the reaction will take a long, long time. All of these minor inacuracies can add up to big problems with your end result!
Keep at it. It will work once you learn the tricks!
