This section is from the book "Monograph on Flavoring Extracts With Essences, Syrups, and Colorings", by Joseph Harrop . Also available from Amazon: Monograph On Flavoring Extracts With Essences, Syrups And Colorings.
Essential oils which have become deteriorated in odor by age, may be restored by shaking for fifteen minutes with a thick cream, made of powdered borax, animal charcoal and water, and then filtering. If much discolored, mix with equal weight of poppy oil and a saturated solution of common salt, and distill. The coloring matter is left behind in the fixed oil.