The determination of the pyrethrins in pyrethrum concentrates in mineral oil

A method is described for the determination of pyrethrin I in pyrethrum concentrates in light mid heavy mineral oils. The method is based that of Wileoxon as modified by Holaday and utilises the separation of chrysanthemum monocarboxylic acid and the reduction of Denier reagent. Modifications of the Wilcoxon‐Holaday method concerned with the initial removal of uncombined acids, the removal of the oil and the separation of the monocarboxylic acid have been introduced. The determination of the monocarboxylic acid by the reduction of Denier reagent gives results for pyrethrum I slightly in excess of those given by a modified Soil method involving separation of the monocarboxylic acid by steam distillation. pyrethrum II may be determined in oil solutions made from petroleum ether extracts of pyrethrum lowers by an application of the Soil method. Further work is required on the determination of pyrethrum II in oil solutions made from acctouo extracts of the flowers. RESP-2633