Introduction: Titrating Waste Vegetable Oil for Biodiesel Production

Picture of Titrating Waste Vegetable Oil for Biodiesel Production

Waste vegetable oil is commonly used for producing biodiesel and becomes degraded during the cooking process into it's constituent fatty acids. This can also happen with new oil if the raw seeds have not been stored properly. The acidity can not be measured with a pH meter or litmus paper as it is not an aqueous solution and so the titration method must be used.

Equipment required:


Add 1ml of oil to the flask and then 10ml of Isopropanol using the syringes and then 3 drops of the indicator solution. Whilst stirring the solution add the sodium hydroxide one drop at a time using the pipette until the indicator solution changes from yellow to green. Keep adding the drops until the green colour is maintained for at least 15 seconds. The amount of hydroxide used will be the final reading minus the initial reading, in ml.

If your amount of hydroxide used = x (ml) and the quantity of oil to process is y (litres), then the amount of solid sodium hydroxide required should be:

z = (x + 3.5) * y grams per litre.

For example, if the titration reading was 3.0 ml, then z will be 6.5 grams of sodium hydroxide per litre of oil.

Step 1: Full Biodiesel Production Instructions

For the complete instructions on how to make biodiesel from waste vegetable oil please visit here:


SHOE0007 made it! (author)2016-11-05

Would an expensive titration equipment for accurate results be required to do this? Or would accurate pipettes be enough. I have made bio diseal at home roughly with some equipment and at college.

Tecwyn Twmffat (author)SHOE00072016-11-06

Well done! All the components required in this instructable all fairly cheap so no, expensive titration equipment is not required. Even with more expensive gear the results would not be any better as the test depends on judging colour changes by eye and, for biodiesel manufacture, it does not need to be particularly accurate anyway.

About This Instructable




Bio: Ugly pirate roaming the seas in search of Treasure.
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