EN 14104 Fat and oil derivatives - Fatty Acid Methyl Esters (FAME) - Determination of acid value
9 Procedure
9.1 Test portion
Take approximately 20 g of the test sample.
Weigh the test portion into a 250 ml conical flask.
9.2 Determination
9.2.1 Dissolve the test portion (9.1) in 1 00 ml of previously neutralised solvent mixture (5.1).
Titrate, whilst swirling the solution, with the potassium hydroxide solution (5.2) to the endpoint when the addition of a single drop produces a slight, but definite colour change persisting for at least 15 s.
9.2.2 If the solution becomes turbid during titration, add a sufficient quantity of the mixed solvent (5.1) to give a clear solution.
10 Calculation
The acid value is reported as:
(56.1 x V x c)/m
where
V is the volume, in millilitres, of standard volumetric potassium hydroxide solution used;
c is the exact concentration, in moles per litre, of the standard volumetric potassium hydroxide solution used;
m is the mass, in grams, of the test portion;
56.1 is the molecular mass of potassium hydroxide.
Results are expressed as mg KOH/g sample and shall be rounded to the second decimal digit.
NOTE The concentration of the ethanolic sodium or potassium hydroxide solution varies with temperature and it may be useful to use the following correction:
V' = Vt x [1 - 0.0011 x (t - t0)]
where
V' is the corrected volume, in millilitres, of the standard sodium or potassium hydroxide solution;
Vt is the volume, in millilitres, of the standard sodium or potassium hydroxide solution measured at temperature t;
t is the temperature at which the determination was carried out, in degrees Celsius;
t0 is the temperature, in degrees Celsius, at which the concentration of the standard sodium or potassium hydroxide solution was determined.
