The oil is a colourless or yellowish liquid with a powerful odour and taste of cloves, sp. gr. 1·046 to 1·058. It is a mixture of a hydrocarbon, and an oxygenated oil called Eugenol, in variable proportions. The former which is termed light oil of cloves and comes over in the first period of the distillation, has the composition C₁₅H₂₄, a sp. gr. of 0·918 and boils at 251° C. It deviates the plane of polarization slightly to the left, and is not coloured on addition of ferric chloride; it is of a rather terebinthinaceous odour.
Eugenol, sometimes called Eugenic Acid, has a sp. gr. of 1·087 at 0° C., and possesses the full taste and smell of cloves. Its boiling point is 247°·5 C. With alkalis, especially ammonia and baryta, it yields crystallizable salts. Eugenol may therefore be prepared by submitting the crude oil of cloves to distillation with caustic soda; the “light oil” distils then, the eugenol, being now combined with sodium, remains in the still. It will be obtained on addition of an acid and again distilling. Eugenol is devoid of rotatory power, whence the crude oil of cloves, of which eugenol is by far the prevailing constituent, is optically almost inactive. The constitution of eugenol is given by the formula
 | OCH₃ | |
| C₆H₃ | OH. | |
| CH·CH·CH₃ |
It belongs to the phenol class, and has also been met with in the fruits of Pimenta officinalis ([see next article]), in the Bay leaves, in Canella bark ([see page 75]), in the leaves and flower buds of Cinnamomum zeilanicum and in Brazilian clove-bark (Dicypellium caryophyllatum Nees).
Eugenol can be converted into Vanillin (see Fructus Vanillæ).
The water distilled from cloves is stated to contain, in addition to the essential oil, another body, Eugenin, which sometimes separates after a while in the form of tasteless, crystalline laminæ, having the same composition as eugenol.[1093] We have never met with it.
According to Scheuch (1863), oil of cloves also (sometimes) contains a little Salicylic acid,
| C₆H₄ |  | OH |
| COOH, |
which may be removed by shaking the oil with a solution of carbonate of ammonium.
Caryophyllin, C₂₀H₃₂O, is a neutral, tasteless, inodorous substance, crystallizing in needle-shaped prisms. We have obtained it in small quantity, by treating with boiling ether cloves, which we had previously deprived of most of their essential oil by small quantities of alcohol. E. Mylius (1873) obtained from it by nitric acid, crystals of Caryophyllinic Acid, C₂₀H₃₂O₆.