A halogenation method for the determination of the total unsaturation of tung oils and of eleostearic acids

Abstract

SummaryA new modification of the Rosenmund‐Kuhnhenn method has been developed for determining the total ethylenic unsaturation of tung oil and of eleostearic acids. With tung oils this method results in iodine values which are in agreement with those obtained by quantitative catalytic hydrogenetation and, in the case of α‐ and β‐eleostearic acids, with the theoretical value. Good agreement was found with hydrogen‐iodine values of various partially hydrogenetal tung oils. An essential feature of the method is the addition of mercuric acetate to the oil prior to the addition of the Rosenmund‐Kuhnhenn reagent in contrast to the Benhan‐Klee modification in which the Rosenmund‐Kuhnhenn reagent is added first. The latter method gives iodine values for tung oil and for eleostearic acid approximately 8% higher than those obtained by quantitative catalytic hydrogenation. Light was found to affect the results obtained by both methods so greatly that use of low‐actinic flasks, addition of the Rosenmund‐Kuhnhenn reagent in a partially darkened room, and storage of the reactants in complete darkness during the reaction period (1 hour) is recommended.