Acid Value Test on Patchouli Essential Oil
Acid value test is commonly performed to check the origin and the quality of Patchouli Essential Oil.
Patchouli oil Sumatra, which is known to have a better quality, typically has an acid value of less than 6 mg KOH/1 gr oil. On the other hand, Patchouli oil Sulawesi, which is the majority type of Patchouli oil produced in Indonesia, has an acid value of higher than 8 mg KOH/ 1 gr oil. In some regions of Sulawesi, due to the acidity of the soil, the acid value can get up to 11 to 12 mg KOH/ 1 gr oil.
How to measure the acid value.
Acid value is defined as how much KOH in mg is required to neutralize 1 gram of essential oil .
Simple titration conducted by adding phenolphthalein as indicator and KOH solution (the concentration has been known before) to the essential oil sample. The addition of KOH is stopped when the solution turns to slightly pinkish purple. The volume of KOH is entered to the formula below to determine the acid value in the essential oil sample.
V = Titration volume of sample (mL)
W = Weight of fat in the volume of extract (g)
56.1 = Molecular weight of KOH
Nb = Concentration of KOH
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 Sharma, S. and Jain, V.K., 2015. Acid Value of Various Domestic Uses Oil. Research Journal of Science and Technology, 7(2), p.109.