The optical rotation of essential oil is , a quick and easy to measure polarimetric quality parameter. It can also be used to distinguish between essential oils and analyze their purity. Essential oils like orange or lemon oil are sometimes referred to by the term volatile oils. They are usually obtained through distillation. These oils are concentrated hydrophobic liquids that extract essential aroma compounds from plants. The optical rotation can be used to characterize their different compositions. These measurements can provide information about the quality and purity of essential oils. Any change in the oil's optimal composition will have an impact on the optical rotation. International pharmacopoeias such as those in the US and Europe require the determination of the optical rotating of essential oils. This is generally done at 25 and 20 degrees Celsius, respectively.