In this cold winter weather, there is rarely anything as pleasant as a cup of hot tea, the steam of which fills the room with various aromas. While drinking my favourite drink – the simple and old one, mint tea, an interesting story came to my mind…

Mint is a well-known plant with recognizable aroma that we find in teas, toothpastes, chewing gums and many other products, and we often use it in the summer months because of its refreshing taste.

That taste, or aroma, comes from the chemical compound menthol. It is a natural organic compound that belongs to the group of terpenes – unsaturated organic compounds that are mainly produced by plants. Menthol is an alcohol, because just like the well-known ethyl alcohol, it contains a hydroxyl group, but you won’t get drunk from it. You can potentially get to smell pleasant…

At room temperature, menthol is a white, crystalline substance with characteristic intense smell, and it is often found as an ingredient in creams and compresses for cooling swellings, since it causes a cooling effect.

Although it is in a solid state at room temperature, just like iodine, it also slowly sublimes, that is, it changes from a solid to a gaseous aggregate state. The reason for this is that the menthol molecules in the crystal are bound by very weak Van der Waals forces, so even room temperature is enough to overpower them.

Due to this property, if closed in a container for a long time, menthol will form wonderful long needle-shaped single crystals near the top, as you can see in the photo.

Author of the text and photos: Alen Bjelopetrović, Dr. Sc.