The iodine value of tung oil

Woburn Iodine Absorption Method, Use in Combination with Partial Iodine Values for the Determination of Diene Numbers

“…5-54°C .) were subjected to the modified Wijs method in ice, as previously suggested for tung oil (21). The values obtained (Table I) are close to the theoretical partial iodine value, but from 2 to 5 points higher.…”

“…The ordinary Wijs iodine value was considered to represent this stage adequately, where two out of three double bonds in eleostearic acid had been saturated with halogen, until Bolton and Williams (6) extrapolated a time series of Wijs numbers of tung oil and obtained its true partial or instantaneous iodine value. A simpler procedure, requiring one 2-minute determination in an ice bath instead of two exposures of 0.5 and 3 hours, respectively, was suggested by one of the authors (21) and shown to give the theoretical two-thirds addition for alpha-eleostearic acid. If this method is to be used in the determination of the diene value it must be adapted to systems of two conjugated double bonds as well.…”

Bodying of Dehydrated Castor Oil

“…Iodine values were determined by the Hanus method on samples small enough to have an excess of at least 400 per cent reagent. This modification was found necessary in order to obtain constant and reproducible results (9). Some modifications used in the Kaufmanrt diene determination (7) as well as the methods for determining the other data listed are described in another paper (10).…”

Composition and Analysis of Dehydrated Castor Oil

“…The total unsaturation, on the other hand, can be determined accurately by a quantitative hydrogenation and possibly by the method of Rossmann (23). Furthermore, it was found in this laboratory (19) that standard Hanus solution (2), when applied in excess of at least 400 per cent for one hour at 20°C ., will give reproducible constants which correspond fairly closely to the total unsaturation as calculated from the drop in hydroxyl value during dehydration, To demonstrate this, the increase of iodine value expected from the decrease of acetyl value is calculated for sample A (Table I). The castor oil used had an acetyl value of 145.5 and an iodine value of 85.0.…”

“…Excess of reagent alone, however, is not sufficient to obtain theoretical values for tung oil, as shown in great detail by Ho, Wan, and Wen (IS). Even with over 400 per cent excess of Wijs solution, only two of the three double bonds in eleostearic acid are attacked if the time is short and the temperature low (19). It could similarly be expected that in the case of dehydrated castor oil not all of the conjugated portion would take up halogen under the ordinary Wijs procedure, even if a large excess of reagent was used.…”