In the world of science, especially for testing purposes, an essential oil might be defined as: a viscous fluid composed of volatile aromatic, and other, compounds created through the natural processes of plants. To continue the scientific look into essential oils, started in my article “Top 10 Questions to Ask Your Essential Oil Distributor or Store” and Evelyn’s “Quality: Tests for Essential Oils” it is necessary that we first lay some groundwork to build a foundation for understanding them.
Here we shall look at some definitions to help us see a little more clearly what essential oils are, why it is important to grow, harvest and process in a certain way and test for purity as well as determine that the compounds that make up a particular oil are within certain guidelines to be suitable for a particular use.
For example, if you are only looking to have the smell, you would look for (and thereby breed for) certain compounds that produce the aroma, whereas if you are looking for healing properties you might look for those compounds and others as well.
So, before we go any further lets set some definitions (we’ll go in the order of the definition in the first paragraph):
- viscous – having a thick, sticky consistency between solid and liquid, which is related to the amount of internal friction in a fluid. Viscosity is a rating of how easily a fluid flows – molasses flows slower (has a higher viscosity) than water.
- fluid – a substance that has no fixed shape and yields easily to external pressure – applies to both liquids and gasses.
- volatile – easily evaporated at normal temperatures and pressures – water is volatile, gasoline is volatile.
- aromatic – having a pleasant and distinctive smell. This is how we can determine the difference between different flowers – eg. a rose does not smell like cinnamon.
- compound - a thing that is composed of two or more separate elements; a mixture.
In some places, you will find that they include in the definition the word “distillation”. While this is true for most essential oils, it is not true for all. In some cases (such as lemon, orange, grapefruit and others) the oil is obtained through mechanical pressure and the oil is separated from any residual fluids that are not part of the oil. In yet others (such as Jasmine, Neroli, and Onycha) it is extracted by the use of solvents because steam doesn’t work at all or doesn’t work very well - these are known as absolutes – and the solvent is then distilled out leaving the actual aromatic compound.
In the world of chemistry, for all intents and purposes, the smallest unit is the atom. Atoms come in many configurations from Hydrogen through Carbon and Gold up to Uranium and beyond. Atoms come together to form molecules and these molecules are what make up the compounds known as essential oils.
There are many types of molecules that are in any single essential oil. These molecules include alkyds, terpenoids, pinenes and many others. Each plant species has varying amounts of these molecules ranging from zero up to 80 or 90% of the volume of a sample. A large volume of a molecule does not mean that will be the smell as the aroma of Grapefruit comes from a very small percentage of a molecule known as mercaptan (C10H18S).
So, differing combinations of compounds in different ratios make the essential oils from different plants unique. This uniqueness allows us to test them to be sure they are in fact from a certain species of plant and thereby verify they are what they are represented as and to also determine if they have been adulterated or cut in any which would make them impure and of lesser quality.
Longtime Young Living Essential Oil user and Webmaster for the Young Living Circle Blog and Website.