Ethanol; grain alcohol; alcohol; ethyl hydrate
Carbon, hydrogen, oxygen
Miscible with water, ether, acetone, and most common organic solvents
Ethyl alcohol (ETH-uhl AL-ko-hol) is a clear, colorless, flammable liquid with a sharp, burning taste and a pleasant, wine-like odor. It is one of the first chemical substances discovered and used by humans. Ceramic jugs apparently designed to hold beer have been dated to the Neolithic Period, about 10,000 bce. Some scholars suggest that humans may have learned how to make beer and incorporated it into their daily diets even before they made and used bread. The making and use of wine is a clear theme in Egyptian pictographs dating to the fourth millennium bce. There probably does not exist a human culture today in which alcohol consumption does not occur. Today, beverages with alcohol content ranging as low as two to five percent ("near beer" and beer) to as high as 50 percent (some forms of vodka) are known and consumed by humans. In spite of its widespread use as a beverage, ethyl alcohol has a number of commercial and industrial uses that account for more than 90 percent of all the compound produced in the United States.
HOW IT IS MADE
Ethyl alcohol is made in one of two ways: naturally, through the process of fermentation, or synthetically, beginning with compounds found in petroleum. Until the beginning of World War II, more than 90 percent of all ethyl alcohol produced in the United States and other developed nations was made by fermentation. Waste syrup left over from the production of sugar from sugar cane was treated with enzymes at temperature of 20°C to 38°C (68°F to 100°F) for 28 to 72 hours. Under these conditions, about 90 percent of the syrup is converted to ethyl alcohol.
Over time, synthetic methods for the production of ethyl alcohol were developed. In one such method, ethylene (ethene; CH2=CH2) is treated with sulfuric acid and water to= obtain ethyl alcohol. That method was popular during the 1950s and 1960s. Then, a new method for making the compound was invented. In that process, ethylene and water are heated together at high temperatures [300°C to 400°C (570°F to 750°F)] and high pressures [1,000 pounds per square inch (6.9 megaPascals)] over a catalyst of phosphoric acid (H3PO4). The efficiency of this method is greater than the older method, and there are fewer environmental consequences from making ethyl alcohol by this process.
As of 2003, about 94 percent of all ethyl alcohol was produced by fermentation. The remainder was produced by the phosphoric acid method.
COMMON USES AND POTENTIAL HAZARDS
In 2005, 10,500 million liters (2,790 million gallons) of ethyl alcohol were produced by fermentation methods. Of that amount, 92 percent was used as a fuel or an additive in fuels. Many experts suggest that consumers use a mixture of gasoline (90 percent) and ethyl alcohol (10 percent) called gasohol as a vehicle fuel because it burns more completely and releases fewer harmful byproducts to the environment. Although gasohol has not yet become very popular in the United States, it is widely used in some other parts of the world, most notably, in Brazil.
- All members of the alcohol family of organic compounds (such as methyl alcohol, ethyl alcohol, and isopropyl alcohol) are toxic to some extent. Only ethyl alcohol is safe to drink in relatively small quantities. Even then, a blood alcohol concentration of less than 5 percent can result in death.
- The concentration of alcohol in a beverage is often expressed as a "proof" number. The proof number of a beverage is twice that of its alcohol concentration. Thus, a beverage that is 80 proof has an alcohol concentration of 40 percent.
Of the remaining 8 percent of ethyl alcohol produced by fermentation, half was used in industrial operations, as a solvent or intermediary in the preparation of other chemical compounds; and half was used in the production of alcoholic beverages.
In 2005, about 650 million liters (170 million gallons) of ethyl alcohol were produced by the phosphoric acid method. Of that amount, 60 percent was used for industrial solvents in the manufacture of toiletries and cosmetics, coatings and inks, detergents and household cleaners, pharmaceuticals, and other products. The remaining 40 percent was used in the preparation of other chemical compounds, including ethyl acrylate, vinegar, ethylamines, ethyl acetate, glycol ethers, and miscellaneous materials.
Ethyl alcohol commonly occurs in one of three general forms. Absolute alcohol is ethyl alcohol that contains less than 1 percent impurities, such as water. Absolute alcohol is very difficult to make because ethyl alcohol will absorb water from the atmosphere or any other source that is available. The ethyl alcohol used in fuels and almost all industrial operations is a mixture of 95 percent ethyl alcohol and 5 percent water. Both absolute and 95 percent ethyl alcohol are extremely toxic. Ingestion of even very small amounts of either liquid has serious health effects that may include death.
The alcohol with which most people commonly come into contact is ethyl alcohol mixed with water in alcoholic beverages, such as beer, wine, gin, vodka, rum, or bourbon. In such beverages, the concentration of ethyl alcohol ranges from a few percent to 50 percent.
The effects produced by ethyl alcohol on the human body depend on the type of beverage consumed and the time taken for consumption. Drinking a 5-percent beer over an hour has a very different effect on the body than drinking a 50-percent vodka in five minutes.
Ethyl alcohol is a central nervous system depressant. After ingestion, it passes through a person's stomach and the small intestine, where it is absorbed rapidly into the bloodstream. It then travels throughout the body, interfering with the normal functioning of the nervous system and producing symptoms such as drowsiness, slurred speech, blurred vision, unsteady gait, impaired judgment, and reduced reaction time. With greater concentrations of alcohol in the blood, these symptoms may become more severe, resulting in coma and death.
Words to Know
- A material that increases the rate of a chemical reaction without undergoing any change in its own chemical structure.
- able to be mixed; especially applies to the mixing of one liquid with another.
- A chemical reaction in which some desired chemical product is made from simple beginning chemicals, or reactants.
FOR FURTHER INFORMATION
"Alcohol." Erowid. http://www.erowid.org/chemicals/alcohol/alcohol.shtml (accessed on October 7, 2005).
"Alcohol: What You Don't Know Can Harm You." National Institute on Alcohol Abuse and Alcoholism. http://pubs.niaaa.nih.gov/publications/WhatUDontKnow_HTML/dontknow.htm (accessed on October 7, 2005).
Boggan, William. "Alcohol and You." http://chemcases.com/alcohol/ (accessed on October 7, 2005).
"Chemical of the Week: Ethanol." http://scifun.chem.wisc.edu/chemweek/ethanol/ethanol.html (accessed on October 7, 2005).
"Ethanol." http://www.ucc.ie/ucc/depts/chem/dolchem/html/comp/ethanol.html (accessed on October 7, 2005).
"How Alcohol Works." How Stuff Works. http://science.howstuffworks.com/alcohol.htm (accessed on October 7, 2005).