Report of the Spectroscopy Committee—1952–1953

As a result of the work herein reported, several conclusions can be drawn: a) Reasonably reproducible results, using A.O.C.S. Tentative Method Cd 7-48, revised May, 1951, can be obtained in the hands of experienced operators. b) No particular increase in either precision or accuracy is obtained by using a 45-min. isomerization time. c) Background corrections are unnecessary and probably undesirable when k′268 is greater than 1.0 and when k′315 is greater than 1.0. d) The present method is valueless for determining the composition of oils such as fish oils containing unsaturated acids of higher unsaturation than tetraene. e) Because of the presence of cis- and trans-isomers in all hydrogenated oils and the presence of iso-acids (position isomers) in hydrogenated oils which contained higher unsaturation than diene,i.e., linolenic or arachidonic acids, the present method is not satisfactory for the analysis of hydrogenated oils. f) As hydrogenated oils contain a mixture of cis- and trans-isomers, analysis of such samples by the techniques of the present method followed by calculations, using constants obtained from acids prepared by bromination-debromination methods (which have been shown to consist of cis- and trans-mixtures) might afford more satisfactory results than use of the constants prepared from the natural acids (the all cis-isomers). The results of these collaborative studies show that use of the debromination constants for the calculation on hydrogenated soybean oil instead of the recommended natural-acid constants did not give much more satisfactory results.