A small aliquot of oil is dissolved in a suitable solvent and reacted with an excess of iodine monochloride (Wij's iodine solution). The residual iodine, after reaction, is titrated against standard sodium thiosulphate using starch as an indicator.
||BS 684, Section 2.13
||mg I2/g Oil
|Significance of result
|The iodine value is a measure of the unsaturation of an oil. The higher the iodine value the more double bonds are present, which consequently reflects the reactivity of the oil.
||Solid fats have low iodine values (typically <60).
Non drying liquid oils have iodine values of approx. 80-120.
Semi-drying oils have an iodine value in the range 120-150.
The iodine value of drying oils are normally greater than 150. Also known as the iodine number.