Determine the percentage of FFA in oil

In order to determine the percent of FFA in the oil, a process called titration is used. The vegetable oil is first mixed with methanol. Next, a mixture of Sodium Hydroxide (NaOH) and water is added until all of the FFA has been reacted. This is confirmed by checking the pH of the mixture. A pH of about 9 signifies all of the FFA has been reacted. Virgin vegetable oil from the same feed stock will usually titrate at approximately the same level, so checking every batch is not necessary. Waste Vegetable oil feed stocks will vary greatly. Every batch must be titrated.

The following items are needed to perform an accurate titration.
- Two 50mL flasks - One 5mL graduated pipette
- A 1mL dropper
- A 10mL dropper
- A mixture of NaOH and water in 0.1% concentration
- pH solution and color chart

The NaOH water mixture can be prepared by adding 1 gram of NaOH to 1000ml distilled water. The mixture will be more accurate if it is first made as a 1% solution (10grams NaOH to 1000ml water). Next, add 100mL of the 1% solution to 900ml of distilled water. This will make a 0.1% NaOH solution.


The process for titration is as follows:

1. Place 10mL of Methanol in a 50ml flask
2. Add 1mL of vegetable oil (mix the oil thoroughly prior to drawing 1ml)
3. Mix the oil with the Methanol using the squirting action of the dropper
4. Add the ph indicator solution (usually 3 drops, check instructions)
5. Place 15ml 0.1% NaOH (know as titrant) solution in a 50ml flask
6. Draw exactly 5ml of the NaOH solution into the graduated pipette
7. Add the 0.1% NaOH to the methanol/oil mixture one drop at a time. Mix the solution using a swirling action between the drops. Using the eyedropper to mix the solution may help if the oil forms drops in the bottom of the flask.
8. Continue to add 0.1% NaOH until a pH of 9 (blue-green color) is reached. This may require more than 5ml. Refill the pipette and continue. Note the amount in ml that was required.
9. Look up the corresponding amount of NaOH required for the entire batch in Table 3. Multiply the amount by the number of gallons of oil to obtain the required amounts.

Table 3. Titration information

ml titration--------%FFA-------------NaOH (grams) per gallon
0------------------0----------------13.25
0.5----------------0.3578222--------15.15
1------------------0.7156445--------17.025
1.5----------------1.0734667--------18.925
2------------------1.431289---------20.825
2.5----------------1.7891112--------22.7
3------------------2.1469334--------24.6
3.5----------------2.5047557--------26.5
4------------------2.8625779--------28.3875
4.5----------------3.2204002--------30.28
5------------------3.5782224--------32.1725