Lee Granberg, age 13, of Carson City, Nov., for his question:
ARE THERE MANY KINDS OF OILS?
A number of different greasy substances are called oil. The color of oil can vary from black to transparent. Most oils are liquids. And most are lighter than water and they float on top of it.
Oils are used in lubricants, paints, foods, medicines and perfume.
Petroleum in a natural oil that is found in the earth. It was formed from plant and animal materials that were buried in rocks of the earth's crust millions of years ago.
Petroleum in a mixture of a number of substances that are separated from the crude oil by distillation. Among the oil products of distillation are natural gases, gasoline, kerosene, fuel oil, lubrication oils and medicinal oils.
Plants store fatty oils in their pulp or seeds. Examples include castor oil, linseed oil, olive oil, cottonseed oil and corn oil.
Animals produce similar fats from the vegetables they eat. Among the animal fats are lard, tallow, butter fat and cod liver oil.
Most animal fats are solid unless they are heated. Plant oils are usually liquid. An extra hydrogen atom in each molecule of animal fat makes the difference.
We have made use of this information to produce from vegetable oils various types of margarine and vegetable shortening that turn out to be much like products made of animal fats. Hydrogen atoms are added to the vegetable oils by a process known as "hydrogenation." The result is an oil that has a higher melting point, which makes it a solid et ordinary temperatures.
Fish oils are rich in vitamins A and D and are used for medicinal purposes,
Linseed oil is a drying oil. The permanent dry, hard film that develops when it is exposed to air makes linseed oil useful in paints and varnishes.
"Volatile" oil is another type of oil that in found in some plant tissues. It is called volatile because it evaporates quickly.
Volatile oils carry the typical aromas of plants and the fragrance of flowers. They are often called "essential" oils because their fragrance is the "essence" of the plant.
To obtain such delicate or valuable oils, a process known as "enfeurage" is used. The flowers are thinly spread over a layer of fatty oil. The delicate, oily essence in absorbed by the cheaper, nonvolatile substance. The resulting mixture of oils is then separated by a process called distillation.
Many volatile oils are used in perfumes. Favorites include attar of roses, lavender oil, jasmine oil and geranium oil. The cost of some of these is high since a large number of flowers are needed to produce a small amount of essential oils. About 500,000 roses are needed to produce a single pound of rose oil.