INDUSTRIAL USES OF PLANTS 389 



followed by fustic, Brazil-wood, sandalwood, and others of very 

 minor importance. The most important domestic dyewood is 

 OSAGE ORANGE, followcd by QUERCITRON or the crushed bark of 

 black oak, black walnut, butternut, sumach, yellow wood, 

 mesquite, red gum and dogwood. These dyewoods are generally 

 made up of 5% to 10% of their weight in true dye, which is 

 extracted from the ground or powdered wood with a suitable 

 solvent and then concentrated to liquid, powder, or crystal form. 

 Most of the present day supply comes from South America. 



Volatile Oils 



These essential oils, as they are often called, differ from the 

 fatty or fixed oils by being volatile, or evaporating in contact 

 with air. They possess a strong, often pleasant, odor and may be 

 removed from their plant sources without any change in chem- 

 ical composition. They occur in a large number of plant families 

 and species, but the Mint, Aster, Myrtle, Laurel, and Parsnip 

 Families are especially known for their aromatic species. These 

 oils usually occur in hairlike structures or in internal glands, and 

 may be found in any part of the plant. They are extracted from 

 their plant sources by a variety of methods, the method used 

 with any particular oil depending upon its stability in the 

 presence of heat, various solvents, and the amounts present. 

 Very delicate oils are removed by extraction with solvents, or by 

 maceration of the oil-yielding parts with fats, after which the 

 extracting agent is either evaporated, or in the case of fats is 

 removed with a volatile solvent. Oils which are more stable and 

 are present in larger amounts are removed from the ground plant 

 parts by steam distillation. This involves heating the plant 

 material in water until the boiling point is reached, at which 

 time the oils are volatilized and distilled into closed containers, 

 where they occur as an oily film on the water which has been like- 

 wise distilled from the boiling mass. 



Uses of essential oils are extremely varied; the more expensive 

 ones are used in the manufacture of perfumes and other toilet 

 preparations. Many are used as flavorings in cooking, and candy 

 and ice cream manufacture. Some have antiseptic properties 



