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For determining the acid value of mineral oils and biodiesel, there are standard methods such as ASTM D 974 and DIN 51558, and especially for biodiesel the European Standard EN 14104 and ASTM D664 are both widely used worldwide. [2] Acid value of biodiesel should be lower than 0.50 mg KOH/g in both EN 14214 and ASTM D6751 standard fuels.
The total acid number (TAN) is a measurement of acidity that is determined by the amount of potassium hydroxide in milligrams that is needed to neutralize the acids in one gram of oil. [1] It is an important quality measurement of crude oil. The TAN value indicates to the crude oil refinery the potential of corrosion problems.
Olive oil contains small amounts of free fatty acids (meaning not attached to other fatty acids in the form of a triglyceride). Free acidity is an important parameter that defines the quality of olive oil. It is usually expressed as a percentage of oleic acid (the main fatty acid present in olive oil
A sample is typically dissolved in a pre-mixed solvent of chlorobenzene and acetic acid and titrated with standardised perchloric acid in glacial acetic acid for fresh oil samples. [2] The end point is detected using a glass electrode which is immersed in an aqueous solution containing the sample, and connected to a voltmeter/potentiometer.
Such a triglyceride has a high iodine value (approx. 119). Below, the reaction product after the addition of four equivalents of iodine or bromine to the four C=C double bonds of the unsaturated fatty acid residues. The determination of iodine value is a particular example of iodometry. A solution of iodine I 2 is yellow/brown in color.
The conversion between hydroxyl value and other hydroxyl content measurements is obtained by multiplying the hydroxyl value by the factor 17/560. [2] The chemical substance may be a fat, oil, natural or synthetic ester, or other polyol. [3] ASTM D 1957 [4] and ASTM E222-10 [5] describe several versions of this method of determining hydroxyl value.
Olive oil is composed mainly of the mixed triglyceride esters of oleic acid, linoleic acid, palmitic acid and of other fatty acids, [100] [101] along with traces of squalene (up to 0.7%) and sterols (about 0.2% phytosterol and tocosterols). The composition varies by cultivar, region, altitude, time of harvest, and extraction process.
The experimental determination of a value is commonly performed by means of a titration. [8] A typical procedure would be as follows. A quantity of strong acid is added to a solution containing the acid or a salt of the acid, to the point where the compound is fully protonated.