you can also do a 'soap test' titration to look for soap in the biodiesel, this titration being with hydrochloric acid regent using bromophenol blue as an indicator. I don't have the formula on hand on how to calculate the amount of soap from the titration- I do it for a different purpose and don't do the math- but it would give you a precise idea of how much soap is in your biodiesel sample. I imagine you could do it to the wash water as well. I'll post directions for this titration soon if an actual chemist who knows more about it than me doesn't get around to it first. It';s in an American Oil Chemists SOciety publication on testing of fats and oils.
Mark --- In biofuel@yahoogroups.com, "Appal Energy" <[EMAIL PROTECTED]> wrote: > > To determine the amount of soap in the wash stream you really have to work > your way backwards > through the process. > > 1) Make your biodiesel. > > 2) Recover your FFAs to determine approximately what percentage of the > original volume of oil dropped out as soap in the glycerin cocktail. > http://www.journeytoforever.org/biodiesel_glycsep.html > > 3) Wash your fuel, with long settling times so no fuel is lost in the > washes, then dry it. Mathematically add the volume of fuel to the volume of > recovered FFAs and subtract the sum from the original volume of oil. > > This will tell you roughly what percentage of oil was converted to the soaps > that were suspended in the biodiesel prior to the wash. > > For example: Presume that you are processing one gallon of soybean oil and > that you have a missing volume of 1/2 of 1% after step #3. (That "missing > volume" is approximately what would be in your wash water.) > > Knowing that the molecular weight of soybean oil is 278.15 > grams/mole and that soybean oil weighs 7.68#s per gallon lets you calculate > that there are 12.519 moles of soybean oil per > gallon. > > Multiplying the 1/2 of 1% that is missing (in your wash water) by 12.519 > moles per gallon gives you ~0.6295 moles of soap in the wash water for that > one gallon batch. > > This means that under perfect conditions you would need ~0.6295 moles of > MgSO4 (magnesium sulfate) to replace all the sodium or potassium molecules > that had bonded with the FFAs/oil to make the soap that is suspended in the > wash water. > > Multiply 0.6295 by 120.37 grams, the weight of one mole of magnesium sulfate > (Epsom salt). This gives you approximately 7.535 grams of Epsom salt needed > for every missing one-half percent, per gallon of oil processed. > > If 1/2 of 1% is missing in a 10 gallon batch, you would need ~75.35 grams of > Epsom salts to treat the water. > > If 1/4 of 1% is missing in a 10 gallon batch, you would need half that > amount, etc. > > You can extrapolate for different sized batches. > .. Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://infoarchive.net/sgroup/biofuel/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/biofuel/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
