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How to Titrate Oil Prior to Making Biodiesel

Note: when doing a titration, the solution in your beaker should be constantly and gently stirred. Always avoid contamination by keeping your lab area clean and lids on all your containers.

  1. Mix together a solution of about 1 gram of NaOH per liter of water. This will be your basic solution.
  2. Put 10 ml of 99% Iso Propyl Alcohol in a small beaker.
  3. Add two drops of Phenolphthalein PH indicator.
  4. Slowly add drop by drop, some of your basic solution until the mixture in the beaker just barely turns and then stays fuchsia. This helps to assure that there are no acidic contaminants.
  5. Add exactly 10 ml of 0.01N HCL.
  6. Slowly add your basic solution until the mixture in the beaker turns back to fuchsia.
  7. Calculate the following: ( 4.0 )/ (# of ml of basic solution) = (True grams of NaOH/ liter) in basic solution.

To accurately determine the acidity (FFA content) of your oil, you need to accurately know the strength of your base solution. It is nearly impossible to measure out a small amount of the base (like sodium hydroxide) to mix into a solution with a high degree of accuracy. One of the problems encountered in trying to do this, is the fact that NaOH quickly absorbs water and CO2 out of the air. This makes the compound both heavier and weaker. Steps 2-6 (above) have allowed you to determine the strength of the basic solution that you are using to titrate your oil. To double check the strength of your base solution, repeat steps 2-6 to make sure the results compare.

Because a basic solution will lose strength over time, whenever, you have a day that you plan to titrate some oil or fuel, start by employing steps 2-6 to find the strength of your base solution. If it has degraded somewhat, there is no need to worry. Simply use the new number that you have for “true grams of NaOH/liter” in step 5 below.

Now to actually titrate your oil (or finished biodiesel if you are testing for TAN):

To process this in the BioPro™ 190, you should have less than 5% FFA To pass TAN test for finished fuel you should have less than .28% FFA.

For greater accuracy on the TAN test you can use 50ml of Isopropyl (step 1), 10 ml of fuel (step 3), and divide by 12.8 instead of 1.28 (step 5).

  1. Add 15 ml of isopropyl and two drops of PH indicator to a beaker.
  2. Add your basic solution drop by drop until the mixture in the beaker just barely turns and stays fuchsia. This helps to ensure that there are no acid contaminants in the beaker.
  3. Add 1 ml of the oil in question to the beaker.
  4. Now slowly add your basic solution into the beaker until the solution turns and stays fuchsia.
  5. Calculate:
    • ((True grams of NaOH/liter) * (number of ml of basic solution)) 1.28 = %FFA