ETHYL ALCOHOL

also called ethanol, grain alcohol, or alcohol the most important member of a class of organic compounds that are given the general name alcohols; its molecular formula is C2H5OH. It is the intoxicating ingredient of many beverages produced by fermentation. There are three main processes for the manufacture of ethanol: the fermentation of carbohydrates, the hydration of ethylene, and the reduction of acetaldehyde (commonly prepared by the hydration of acetylene). Before 1930 all ethanol was prepared by fermentation process, which still remains the most important method in most countries. In the United States, 70 to 90 percent of the total output of ethanol is now produced by hydration of ethylene, however. The fermentation process involves the transformation of carbohydrates to ethanol by growing yeast cells. The chief raw materials for this process are molasses and corn (maize). The hydration of ethylene is achieved by passing a mixture of ethylene and a large excess of steam. Ethanol produced either by fermentation or by synthesis is obtained as a dilute aqueous solution and must be concentrated by fractional distillation. Direct distillation can yield at best the constant-boiling-point mixture containing 95.6 percent by weight of ethanol. Dehydration of the constant-boiling-point mixture yields anhydrous, or absolute, alcohol. Because ethyl alcohol for beverage purposes is subject to tax in all countries, ethyl alcohol for industrial purposes must be rendered unfit to drink (denatured) to escape taxation. Typical denaturants that are mixed with ethyl alcohol are methanol, camphor, benzene, and kerosene. Pure ethanol is a colourless, flammable liquid (boiling point 78.5 C ) with an agreeable ethereal odour and a burning taste. Ethanol is toxic, affecting the central nervous system. Moderate amounts stimulate the mind and relax the muscles, but larger amounts impair coordination and judgment, finally producing coma and death. It is an addictive drug for some persons, leading to the disease alcoholism. Ethyl alcohol is converted in the body first to acetaldehyde and then to carbon dioxide and water, at the rate of about 0.75 ounce per hour; this quantity corresponds to a dietary intake of about 200 calories.