In contrast, the fixed oils like corn, safflower and peanut, do not evaporate. The Grease Spot Test is a test to determine whether an oil is volatile or fixed. Simply spot a small sample of the oil on a sheet of paper. If it leaves an oily mark, like after eating some potato chips, the oil is fixed. If it disappears, it is an essential oil.
Essential oils are a diverse mixtures of molecules.
The kind and concentration of molecules in the oil determines its odor. The molecules typically have 20 carbon atoms or fewer and are hydrocarbons, terpenes, alcohols, phenols, esters, aldehydes and ketones. Plants and essential oils A . Essential oils occur in numerous different plants, but especially tropical and subtropical species. They occur in more than 60 families and are especially common in the Mint, Citrus, Laurel, Myrtle, Geranium and Carrot families.