Butane

OVERVIEW

Butane (BYOO-tane) is a colorless gas with the odor of natural gas that is highly flammable and explosive. It exists in two isomeric forms. Isomers are forms of a chemical compound with the same molecular formula (in this case, C₄H₁₀), but different structural arrangements. In one isomer ("normal" or "n-" butane), the four carbon atoms are arranged in a continuous chain, while in the other ("iso-butane"), three carbon atoms are arranged in a continuous chain and the fourth carbon atom is attached to the middle atom in that chain.

Butane occurs naturally in natural gas, where it is present to the extent of about 1 percent, and in petroleum, where it exists only in very small amounts. Butane is used primarily as a fuel and as a chemical intermediary, a compound used to produce other chemical substances.

KEY FACTS

OTHER NAMES:

n-Butane

FORMULA:

C₄H₁₀

ELEMENTS:

Carbon, hydrogen

COMPOUND TYPE:

Alkane; saturated hydrocarbon (organic)

STATE:

Gas

MOLECULAR WEIGHT:

58.12 g/mol

MELTING POINT:

−138.3°C (−216.9°F)

BOILING POINT:

−0.5°C (31°F)

SOLUBILITY:

Slightly soluble in water; soluble in ethyl alcohol, ether, and chloroform

HOW IT IS MADE

Butane is obtained during the separation of natural gas into its components. Natural gas consists primarily (70 to 90 percent) of methane. Other components include ethane (about 9 percent), propane (about 3 percent), and butane (about 1 percent). The remaining 1 to 2 percent of natural gas is impurities, including nitrogen, carbon dioxide, compounds of sulfur, and water. The process of separating natural gas into its components begins with the removal of water. The natural gas is forced through some drying agent, such as diethylene glycol (HO(CH₂)₂O(CH₂)₂OH), which efficiently removes water from the gas. The dry gas is then treated with an agent to remove carbon dioxide, compounds of sulfur, and other impurities. Diethanolamine (HO(CH₂)₂NH(CH₂)₂OH) is an efficient "scavenger" of many of these impurities.

After dehydration and removal of impurities, the remaining gas consists almost entirely of simple hydrocarbons, primarily methane, ethane, propane, and butane. These hydrocarbons can be separated from each other by cooling them until they reach the point at which they become liquid. As each component liquefies, it can be removed from the gas and further purified. For example, butane changes from a gas to a liquid at −0.5°C (31°F) and propane liquefies at about −42°C (−44°F). So as the hydrocarbon mixture cools, liquid butane can be removed before any other components liquefy. In actual practice, liquid butane and propane are removed together, leaving behind only ethane and methane. The mixture of liquid butane and propane is known as liquid petroleum gas (LPG). Since propane and butane have many similar properties, there is often no commercial reason to go to the expense of separating them from each other. LPG is typically stored above or below ground in large, insulated containers and shipped in insulated trucks or rail cars.

COMMON USES AND POTENTIAL HAZARDS

Butane, in both gaseous and liquid form, is widely used as a fuel. Because it is easily stored and transported in small containers, it is used as a fuel for backpacking stoves, small space heaters, and portable torches. Butane is also the fuel most commonly used in cigarette lighters. It may be used in its pure form or in combination with propane as liquefied petroleum gas (LPG). Butane is also used as a fuel for larger household and industrial operations.

Interesting Facts

• Some people have used butane as a recreational drug, inhaling it to get "high." The practice is extremely dangerous, however, and has led some users to die of asphyxiation (suffocation).
• Researchers at Surrey Satellite Technology, Ltd. in the United Kingdom have built a small satellite the size of a soccer ball that is propelled by pressurized butane gas. The butane thruster was built for $15,000 and was launched aboard a Russian Cosmos spacecraft in June 2000.
• Contact with liquid butane or LPG can cause frostbite, for which first aid involves washing with cold water.

In terms of volume, one of the major uses of butane is in the synthesis of other organic compounds, especially synthetic rubber and high-octane liquid fuels used in aviation. The gas is sometimes added to gasoline in cold climates to improve the rate at which the fuel evaporates and burns. A relatively new application for butane is as a propellant for spray products, such as hair spray and spray paints, and as a refrigerant. Butane is being used for these purposes as a substitute for chlorofluorocarbons (CFCs), which have been shown to have damaging effects on the Earth's ozone layer. Small amounts of butane are also used as food additives, usually in foods that are dispensed as sprays.

The primary health hazard posed by butane is its narcotic effects. When inhaled, either accidentally or intentionally, it produces a sequence of bodily changes that include, at first, a sense of euphoria and excitement. Increased doses may then produce harmful results, such as nausea, vomiting, sneezing, coughing, blurred vision, slurred speech, and increased salivation. Even higher doses result in confusion, perceptual distortion, hallucinations, and delusions. Eventually, a sequence of life-threatening conditions may develop, including depression of the central nervous system, irregular heartbeat, drowsiness, coma, and death.

Words to Know

EUPHORIA

A state of extreme happiness and enhanced well-being.

HALLUCINATIONS

Visions or other perceptions of things that are not really present.

FOR FURTHER INFORMATION

"Acute Exposure Guideline Levels (AEGLs) for n-butane." National Advisory Council, U.S. Environmental Protection Agency. Washington, DC: U.S. Environmental Protection Agency, April 2004. Also available online at http://www.epa.gov/oppt/aegl/pubs/tsd102.pdf (accessed on December 29, 2005).

"Butane." International Labour Organization. http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc02/icsc0232.htm (accessed on December 29, 2005).

"Butane." International Programme on Chemical Safety. http://www.inchem.org/documents/pims/chemical/pim945.htm#SectionTitle:2.1%20%20Main%20risks%20and%20target%20organs (accessed on December 29, 2005).

Russell, Justin. "Fuel of the Forgotten Deaths." New Scientist (February 6, 1993): 21-23.

See AlsoMethane; Propane

butane (C₄H₁₀) Colourless flammable gas, the fourth member of the alkane series of hydrocarbons. It has two isomers: n-butane is obtained from natural gas; isobutane is a by-product of petroleum refining. Butane can be liquefied under pressure at normal temperatures and is used in the manufacture of fuel gas and synthetic rubber. Properties: b.p. (n-butane) −0.3°C (31.5°F) and (isobutane) −10.3°C (13.46°F).

bu·tane / ˈbyoōˌtān/ • n. Chem. a flammable hydrocarbon gas, CH₃CH₂CH₂CH₃, that is a constituent of petroleum and is used in bottled form as a fuel. It is a member of the alkane series.