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Solvent Extraction: A Kinder, Gentler Alternative Though distillation can be used as a method of obtaining most essential oils (80%), it can not be used for all. Why? Many white florals disintegrate quickly under the violent boiling methods of distillation. In addition, the constituents of jasmine and narcissus are so volatile that they can not be condensed by the still—their oils literally dissolve into thin air before they can even be condensed! So for the remaining 20% that do not respond well to distillation, there are a few other methods, one of which is solvent extraction. |
Above: Geraniums ready for distillation (Photo from the early 1900's) (1). |
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Solvent extraction was first used in the petroleum plants of Pennsylvania and was later applied to perfumery in the early 19th century. The process is as follows: as soon as possible, the flower petals are harvested and taken to an extraction plant. The blooms are then loaded into huge tanks and hermetically sealed. A solvent is passed through the tank (much in the way that clothes are dry-cleaned), but only the fragrant oils are removed, not any dirt or grease. Today, the solvent employed is usually petroleum ether—it has a low boiling point (60 º to 80º C). As the solvent collects the oil, it may also collect any plant waxes or paraffins, as well as pigments. The solvent is then evaporated, and what is left is known as "floral concrete," a left-over solid due to the presence of paraffins. The waxes are removed by putting them in an apparatus called a batteuse, and then mixing them with ethyl alcohol. The oils pass into the alcohol and the wax is removed. Then the oil must be extracted from the alcohol by distilling it in a vacuum to maintain the low temperature necessary to the preservation of the fragile essences. Jasmine, violets, hyacinths, carnation, boronia, oakmoss and Spanish broom respond best to solvent extraction. |
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