Optical Rotation is defined as how light bends when passing through a material (specifically a liquid).

Source: Coolphysicsvideos

Certain liquids have the ability to bend light, such as the liquid in the above image. This measurement on the rotation of a light source is measured by an instrument and is described as optical rotation.

Only certain chemical compounds have the ability to rotate light and these chiral compounds, those lacking microscopic mirror symmetry, vary depending on the substance, or essential oil in this case. Many of the more complex compounds have chiral carbon centers (or different unique possible connectivity to different atoms) and it is these different configurations that lead to the bending of light in one direction or the other.

Example of an essential oil with a Positive Optical Rotation:
Lime: 15.45o

Example of an essential oil with a Negative Optical Rotation:
Carrot Seed: -7o

The Optical Rotation values for all of our essential oils can be found under the "Technical Data" section of the oils' Certificates of Analysis. It is one of five sets of "fingerprint" measurements that is used to identify any possible inconsistencies in the oil's composition. When testing an essential oil that has entered Ananda's facility and lab, we compare the optical rotation value with previous batches. If the optical rotation varies significantly with previous batches, this may be an indicator that that oil may have been contaminated or adulterated.