ISO 3961-2013 pdf free download

ISO 3961-2013 pdf free download.Animal and vegetable fats and oils — Determination of iodine value
Corps gras d’origines animale et végétale — Determination de I’m dice d’iode.
9 Procedure
9.1 Place the glass scoop containing the test portion in a 500 ml conical flask (2) and add the volume of solvent (55) indicated in Table 1. Add 25.00 ml of the Wijs reagent (5) by pipette (,5). Insert the stopper, swirl the contents and place the flask in the dark.
Melt and dissolve fats and oils with a IV of 20 or less (hard or hardened fats) in warm solvent (60 °C). It is also recommended that all flasks and reagents be warmed before use. Closed vessels shall be used to avoid evaporation and change in concentration when warming the reagents.
NOTE The scoop remains in the flask.
CAUTION — Do not use a mouth pipette for the Wis reagent.
9.2 Prepare a blank with solvent and reagent as in 9j hut omitting the test portion.
9.3 For samples having an IV below 150, leave the flasks in the dark for I h. For samples with lVs above
150, and for polymerized products and oils containing conjugated fatty acids (such as tung oil, dehydrated
castor oil) and any oils containing keto fatty acids (such as some grades of hydrogenated castor oil) and
products oxidized to a considerable extent, leave the flasks in the dark for 2 h.
9.4 At the end of the reaction time (9.3), add 20 ml of potassium iodide (52) and 150 ml of water (5.1). Titrate against standard sodium thiosulfate solution (SA) until the yellow colour due to iodine has almost disappeared. Add a few drops of the starch solution (5.3) and continue the titration until the blue colour just disappears after vigorous shaking. Record the volume, V2, of sodium thiosulfate solution required to reach the endpoint. Note that potentiometric determination of the endpoint is permissible.
11 Precision
11.1 Interlaboratory test
Details of an interlaboratory test on the precision of the method are summarized in AnnexA. It is possible that the values derived from this interlaboratory test are not applicable to concentration ranges and matrices other than those given.
11.2 Repeatability limit, r
The repeatability limit, r, is the value less than or equal to which the absolute difference between two test results obtained under repeatability conditions may be expected to be with a probability of 95 %.
Repeatability conditions are conditions where independent test results are obtained with the same method on identical test items in the same laboratory by the same operator using the same equipment within short intervals of time.
11.3 ReproducibilIty limit, R
The reproducibility limit, R, Is the value less than or equal to which the absolute difference between two test results obtained under reproducibility conditions may be expected to be with a probability of 95 %.
Reproducibility conditions are conditions where independent test results are obtained with the same method on identical test items in different laboratories with different operators using different equipment within short intervals of time.ISO 3961-2013 pdf free download.