EN 14111 Fat and oil derivatives - Fatty Acid Methyl Esters (FAME) - Determination of iodine value
9 Procedure
9.1 Test portion
Take approximately 0.13 g to 0.15 g of the test sample, weighed to the nearest 0.001 g in a glass weighing scoop (6.1).
NOTE In the case of an iodine value below 100, the mass of the test portion should be adjusted according to clause 9 of EN ISO 3961.
9.2 Determination
9.2.1 Place the glass weighing scoop containing the test portion in a 500 ml flask (6.2) and dissolve using 20 ml of solvent (5.4). Add 25 ml of Wijs reagent using a precision pipette. Insert the stopper, swirl carefully and place the flask in the dark.
CAUTION - Do not use a mouth pipette for the Wijs reagent.
9.2.2 Prepare a blank with solvent and reagent as in 9.2.1 but omitting the test portion.
9.2.3 Leave the flask in the dark for 1 h.
9.2.4 At the end of the reaction time add 20 ml of potassium iodide solution (5.1) and 150 ml of water.
Titrate with standard sodium thiosulfate solution (5.3) until the yellow colour due to iodine has almost disappeared. Add few drops of the starch solution (5.2) and continue the titration until the blue colour just disappears after very vigorous shaking. Potentiometric determination of end point is also permissible.
9.2.5 Carry out a blank test using the blank solution (9.2.2) concurrently.
10 Calculation - Iodine value
The iodine value reported in g of iodine/ 100 g of FAME, is given by the following equation:
[12.69 x c x (V1 - V2)/m
where
c is the exact concentration, in moles per litre, of the standard volumetric sodium thiosulfate solution used;
V1 is the volume, in millilitres, of standard volumetric sodium thiosulfate solution (5.3) used for blank test;
V2 is the volume, in millilitres, of standard volumetric sodium thiosulfate solution (5.3) used for sample titration;
m is the mass, in grams, of the test portion.
Results shall be expressed to the nearest 1 g of iodine/100 g.
