Bepaling van het joodadditiegetal
The iodine value II is the number that expresses in grams the quantity of halogen calculated as iodine that can be fixed in the prescribed conditions by 100 g of the substance.
Unless otherwise prescribed, use the following quantities (Table 2.5.4.-1) for the determination:
Table 2.5.4.-1
|
Presumed value II |
Quantity of sample (grams) |
|
less than 20 |
1.0 |
|
20 - 60 |
0.5 - 0.25 |
|
60 - 100 |
0.25 - 0.15 |
|
more than 100 |
0.15 - 0.10 |
Introduce the prescribed quantity of the substance to be examined (m g) into a 250 ml flask fitted with a ground-glass stopper and previously dried or rinsed with glacial acetic acid R, and dissolve it in 15 ml of chloroform R, unless otherwise prescribed. Slowly run in 25.0 ml of iodine bromide solution R. Close the flask and keep it in the dark for 30 min unless otherwise prescribed, shaking frequently. Add 10 ml of a 100 g/l solution of potassium iodide R and 100 ml of water R. Titrate with 0.1 M sodium thiosulphate, shaking vigorously until the yellow colour is almost discharged. Add 5 ml of starch solution R and continue the titration adding the 0.1 M sodium thiosulphate dropwise until the colour is discharged (n1 ml of 0.1 M sodium thiosulphate). Carry out a blank test under the same conditions (n2 ml of 0.1 M sodium thiosulphate).
II = 1.269 (n2 - n1) / m
10 september 1999