Determination of true iodine number of oils with conjugate unsaturation by use of hypochlorous acid reagent

Summary Hypochlorous acid reagent has conveniently been used for the determination of total unsaturation in oils containing conjugated double bonds. The use of 0.1 N HOCl reagent normally employed for oils with isolated double bonds leads to incomplete absorption, and the increase in concentration and reaction period gives desirable results in the presence of mercuric acetate catalyst. A 1-hr. reaction period with 0.3 N HOCl reagent in the presence of 2.5% solution of the catalyst is recommended. A sample size varying between 0.07–0.1 g. and a 300–400% excess reagent should be employed to obtain reliable results. This procedure can be effectively used for determining the total unsaturation of tung oil, isomerized fatty acids, and dehydrated castor oil and can be employed for detecting the adulteration in commercial samples of tung oil, which cannot be ordinarily detected by the determination of the partial iodine number with the help of conventional procedures.