Perfume: A Third-Grade Science Fair Project
Following on after a successful first-grade science fair project, my daughter couldn't think of a project this year that would be sufficiently interesting to justify all the study, expense, and worry. But a wasteful, yet common, 8-year-old practice inspired us.
A friend of my daughter introduced her to mixing fragrant household products in order to make perfumes (or potions). When I was a boy, I remember doing this with the shampoo, conditioner, and whatever else I could find in the bathroom. So with that in mind, my daughter suggested "perfume" as a topic. I did basic research into perfume and discovered that there were three methods that we could do for a reasonable cost -- enfleurage, steam distillation, and solvent extraction.
We decided that our science experiment would qualitatively and quantitatively examine the differences between steam distilled essential oils and solvent extracted absolutes. E.g., "What effect does extraction method have on the fragrances?" The general design would be to prepare two samples from the same plant material, such as lavender, orange peels, etc., and steam distill one of the samples and solvent extract the other sample. Give a sniff and compare. The stretch goal would be then to get access to a GC-MS analysis to figure out what each processes' chemical composition is.
After a great deal of capital investment, for a 3rd grade science fair, we've put together a well-researched system for solvent extraction, absolute distillation. Thanks for the miracle of Chinese glassware, some parts left over in my lab, and Home Depot, we've put together a vacuum pump and control system capable for regulating between 0 and 97% of atmospheric pressure for the vacuum distillation, a Soxhlet extractor with heating mantle, and fountain-pump-based water circulation system for the condensers.
Steam distillation is pretty basic. Solvent extraction is a bit more involved. Somehow you need to expose the plant material to a solvent (pentane, in our case) that will dissolve the wax-based structure, freeing the aromatic compounds, along with pigments and other non-essential molecules. To accomplish this step, we are utilizing a large Soxhlet extractor that will condense pure solvent onto the sample, then syphon off the solution back into the heating flask. Because pentane boils at <100°F, it should not damage the aromatic compounds. Then the solvent needs to be as completely removed as possible. We will do this with a basic distillation set-up. What is left is a waxy mass with the pigments and aromatic compounds embedded in it -- "concrete". This is then dissolved in anhydrous ethyl alcohol (200-proof absolute). The final step is a vacuum distillation (the vacuum is needed to reduce the boiling point of the ethanol-aromatic compound from ~170°F to less than 100°F). The distilled "absolute" is considered the most concentrated fragrance available. These absolutes are the building blocks of much of real perfumery.