Step 4: Titrate your oil

This is where we test the acidity of the oil, by measuring the free fatty acids, to see how much NaOH is needed for the reaction.

Start by measuring out 1 gram of NaOH and mixing that with one liter of the distilled water. This gives you a 1/1000 solution. Keep this, you won't use it all on one titration.

Next measure out 10 milliliters of the isopropyl and 1 milliliter of your WVO sample. Mix these in the same jar. Now add about 5 drops of Phenol Red indicator to this solution; swirl to get it mixed. Fill the last syringe with your lye/water solution and add 1/4 milliliter at a time while swirling the jar. Once it turns bright pink and stays that way you need to count exactly how many milliliters of lye/water solution you used to neutralize the acidity of the oil.

Now we can use this information to tell us how much NaOH to use in the reaction.
The formula is this:

For NaOH- # of liters of oil x 4 grams + titration

For example, say I titrated at 2 milliliters and was using 50 liters of oil. I would do 50 x 6=300. 300 grams of NaOH for that batch.
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JimU4 months ago took me a minute to figure out how you got six for your 50 X 6 = 300. You've got to follow the PEMDAS order of operations. The 4 + 2 should have been in (parentheses) to equal 6. The answer should have been 202 the way you had it set up. And how did you get the 4? Is that a constant no matter if it's 50 liters or 500 or 5000 liters? I'm new at this, but I have the knowledge of math and chemistry to make it happen. Thanks.

theturn2 years ago
Don't forget to adjust for purity of your catalyst :
In many cases its dificult to get 100 % pure catalyst (NaOH or KOH)
Divide your base (4 grams in above example) by purity.
If NaOH is used and its 90% pure divide 4 by 0.9 = 4.44 and add this to your titration result using above example (4.44 + 2) = 6.44 x 50 = 322g needed.
Failing to do this, you could leave free fatty acids (FFA) in your processor / finished biodiesel because you didn't account for purity and add enough catalyst.
The point of titrating is to find out exactly how much "extra" catalyst we need to deal with the FFA's over the basic formula for virgin veg oil.
Hope this helps.
hi tufrat look on the journey to forever web site it gives covertion tables for both koh and naoh.Its agood site for allthings earh friendly. regards
TufRat5 years ago
 What is the method if you are using KOH instead of NaOH, particularly the mass/ volume KOH used instead of NaOH?