Aromatic hydrocarbon (organic)
Insoluble in water; soluble in ethyl alcohol; very soluble in ether and acetone
Naphthalene (NAF-thuh-leen) is a white crystalline volatile solid with a characteristic odor often associated with mothballs. The compound sublimes (turns from a solid to a gas) slowly at room temperature, producing a vapor that is highly combustible. Naphthalene was first extracted from coal tar in 1819 by English chemist and physician John Kidd (1775–1851). Coal tar is a brown to black thick liquid formed when soft coal is burned in an insufficient amount of air. It consists of a complex mixture of hydrocarbons, similar to that found in petroleum. Kidd's extraction of naphthalene was of considerable historic significance because it demonstrated that coal had other important applications than its use as a fuel. It could also be utilized as the source of chemical compounds with a host of important commercial and industrial uses. Naphthalene's chemical structure was determined by the German chemist Richard August Carl Emil Erlenmeyer (1825–1909). Erlenmeyer showed that the naphthalene molecule consists of two benzene molecules joined to each other.
HOW IT IS MADE
Naphthalene occurs naturally in petroleum and coal tar. It is extracted from either by heating the raw material to a temperature of 200°C to 250°C (392°F to 482°F), producing a mixture of hydrocarbons known as middle oil. The middle oil is then distilled to separate its individual components from each other, one of which is naphthalene. The naphthalene produced in this process is purified by washing it in a strong acid and then in a sodium hydroxide solution and purified by steam distillation.
COMMON USES AND POTENTIAL HAZARDS
In 2000, about 100,000 metric tons (110,000 short tons) of naphthalene was produced in the United States. About 60 percent of that amount was used for the synthesis of phthalic anhydride [C6H4(CO)2O], a compound used as the starting point in the manufacture of a host of products, including a variety of dyes, resins, lubricants, insecticides, and a number of other products. At one time, naphthalene was used widely as a moth repellent in mothballs and moth flakes and in the manufacture of insecticides and fungicides. Demand for these applications has decreased, however, with the introduction of a class of compounds known as the chlorinated hydrocarbons. For example, one of those compounds, p-dichloro-benzene, is now the primary ingredient, rather than naphthalene, in mothballs and moth flakes.
- The name "naphthalene" comes from the Persian word naphtha, meaning "oil" or "pitch."
- One use of naphthalene is as an insecticide. None-theless, one type of insect, the Formosan termite, uses naphthalene to build its nests. Scientists have not yet determined the source from which the termites get naphthalene or why they are immune to its otherwise toxic properties.
- Naphthalene becomes an environmental contaminant when it leaches into the soil. In 2003, however, scientists discovered bacteria capable of decomposing naphthalene in the soil, reducing the environmental hazards it poses.
- One of the most terrible weapons used during the Vietnam War of the 1960s and 1970s was a mixture of naphthalene and palmitate called napalm that ignited and burned at a very high temperature causing widespread destruction of plant life, structures, and human life.
Some other uses of naphthalene include:
- As an ingredient in the manufacture of the explosive known as smokeless gunpowder;
- In the manufacture of scintillation counters, devices used to detect and measure radioactivity;
- In the production of lubricants;
- In the manufacture of various types of dyes and coloring agents;
- As an antiseptic and antihelminthic (a substance used to kill disease-causing worms);
- As a deodorant in toilets, diaper pails, and other settings; and
- As a preservative.
Naphthalene can be toxic by ingestion, inhalation, or absorption through the skin when humans are exposed to it in more than a passing way. In small amounts it may produce symptoms such as nausea, vomiting, headache, and fever. In larger amounts, it may induce more serious problems, including liver damage, blindness, coma, convulsions, and death. One medical problem that has been associated with exposure to large amounts of naphthalene is hemolytic anemia, a condition in which red blood cells are destroyed, resulting in fatigue, restlessness, jaundice, loss of appetite, and, in more serious cases, kidney failure.
Words to Know
- A process of separating two or more substances by boiling the mixture of which they are composed and condensing the vapors produced at different temperatures.
FOR FURTHER INFORMATION
"Background and Environmental Exposures to Naphthalene, 1-Methylnaphthalene, and 2-Methylnaphthalene in the United States." Agency for Toxic Substances and Disease Registry. http://www.atsdr.cdc.gov/toxprofiles/tp67-c2.pdf (accessed on October 17, 2005).
Milius, Susan. "Termites Use Mothballs in Their Nests." Science News (May 2, 1998): 228.
"Naphthalene Chemical Backgrounder." National Safety Council. http://www.nsc.org/ehc/chemical/Naphthal.htm (accessed on October 17, 2005).
naph·tha·lene / ˈnaf[unvoicedth]əˌlēn; ˈnap-/ • n. Chem. a volatile white crystalline compound, C10H8, produced by the distillation of coal tar, used in mothballs and as a raw material for chemical manufacture. DERIVATIVES: naph·thal·ic / nafˈ[unvoicedth]alik; nap-/ adj.