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Quantifying Acid Number by titration
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I understand that the proper method to determine the acid number for a sample of FAME is through potentiometric titration. However, from this article (http://www.make-biodiesel.org/Biodiesel-Chemistry/acid-number-to-ffa-conversions.html), I understand that you can reach a close approximation using the conventional titration method, just as you would do to determine the FFA content of a sample of WVO. The article states that you would use the formula:
    AN=1.08t

to determine the Acid Number. However, it does not state what units that calculation would yield, so how can I determine if I am within the ASTM D 664 limit of 0.50 mg/g?

Any clarification would be appreciated.
 
Registered: June 19, 2012Reply With QuoteReport This Post
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1.08 is the inverse of 0.923 which is the approximate density of vegetable oil in grams per milliliter. So the inverse would be milliliters per gram. Titration is done in grams per liter. Acid number (acid value) is milligrams per gram. Its just a unit conversion method thing. But I measured the density of new corn oil at 0.915 grams per milliliter. The density of vegetable oils vary. At least I think that's your answer. Thanks But the density of biodiesel that I measured was about 0.84 grams per milliliter. I read on the computer biodiesel density may be 0.87-0.88 grams per milliliter. You can easily measure the density of your biodiesel with a one liter volumetric flask. Fill it to the line, then weigh it. Or a 100 ml graduated cylinder. According to Wikipedia, Acid Number is the mass of KOH in milligrams that will neutralize one gram of a chemical substance.

This message has been edited. Last edited by: WesleyB,
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
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