Volatile Oils
essential oils; oils which can be distilled without decomposition. They are classed under two heads; mineral and vegetable; the former being composed of carbon and hydrogen, and generically known as paraffins. The vegetable oils, which are generally procured by distilling the odoriferous substance with water, may be divided into three great classes: (1) Oils composed of carbon and hydrogen (binary volatile oils), of which oil of turpentine may be considered the type; (2) oils containing carbon, hydrogen, and oxygen (oxygenated oils), which include most of those used in medicine and perfumery; and (3) oils containing sulphur (sulpheretted oils), characterized by their extreme pungency and suffocating odor, such as oil of mustard, asafœtida, etc. The volatile oils are generally more limpid and less unctuous than the fixed oils, and are almost colorless after rectification. They are soluble in alcohol and ether, slightly soluble in water, and mix in all proportions with the fixed oils. are