Fig. 4.
(a) Variation of absorbance index of peaks 722, 970, 987, 1744 and 3472 representing the out-of-plane C–H bend of the methylene group bridging the double bonds, conjugated double bonds (970 and 987), the carbonyl group and the formation of hydroxyl groups, respectively, during oxidation of boiled linseed oil at 80 °C and (b) Variation of the absorbance index of 3010 cm−1 peak during oxidation of boiled linseed oil at 80 °C.