Testing Waste Vegetable Oil with Titration

One hundred percent virgin or lightly used waste vegetable oil (WVO) requires 3.5 grams of lye per liter of oil to cause a biodiesel reaction. Heavily used oil can require significantly more, and must be tested to evaluate its acidity. Titration is a common method used to determine the appropriate amount of lye (base) needed for a particular batch of WVO.

Titration

Equipment:

·        an electronic scale or beam balance

·        2 beakers or jars

·        a graduated dropper

·        litmus test strips or electronic pH meter

·        lye ( Flack Or Cristal Drain Cleaner )

·        isopropyl alcohol ( 91% or above )

·        distilled water

Following are the steps to complete a titration test:

1.      Measure 1 gram of lye on a scale.

2.      Measure 1 liter of distilled water into a beaker.

3.      Thoroughly mix the gram of lye with the liter of water until it’s dissolved.

4.      Measure 10 milliliters of isopropyl alcohol into a separate beaker.

5.      Thoroughly mix 1 milliliter of used vegetable oil into the alcohol.

6.      With a graduated eyedropper, put a 1 milliliter drop of the lye/water mix into the oil/alcohol mix.

7.      Immediately check the pH level of the oil/alcohol mix with a piece of litmus paper or an electronic   pH meter.

8.      Repeat step 7, keeping track of the number of drops used, until the oil/alcohol mix has reached a pH level of between 8 and 9--normally no more than 4 drops.

9.      Calculate the amount of lye needed for the biodiesel reaction by adding 3.5 (amount of lye used for virgin oil) to the number of drops from step 7. For example: suppose a titration uses 3 drops of lye/water. Adding 3.0 plus 3.5 = 6.5. This hypothetical batch of oil requires 6.5 grams of lye per liter of oil.