Grain Alcohol

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Ethyl alcohol, or ethanol, C2 H5OH, is a clear, colorless liquid, with a burning taste and characteristic, agreeable odor. Ethanol is the alcohol in such beverages as beer, wine, and brandy. Because of its low freezing point, it has been used as the fluid in thermometers for temperatures below -40° C (-40° F), the freezing point of mercury, and for other special low-temperature purpose, such as for antifreeze in automobile radiators.

Ethanol is normally concentrated by distillation of dilute solutions. Commercial ethanol contains 95 percent by volume of ethanol and 5 percent of water. Dehydrating agents remove the remaining water and produce absolute ethanol. Ethanol melts at -114.1° C (-173.4° F), boils at 78.5° C (173.3° F), and has a specific gravity of 0.789 at 20° C (68° F).

Ethanol has been made since ancient times by the fermentation of sugars. All beverage ethanol and more than half of industrial ethanol is still made by this process. Starch from potatoes, corn, or other cereals can be the raw material. The yeast enzyme, zymase, changes the simple sugars into ethanol and carbon dioxide. The fermentation reaction, represented by the simple equation
C6H12O6→ 2C2 H5OH + 2CO2
is actually very complex because impure cultures of yeast produce varying amounts of other substances, including fusel oil, glycerin, and various organic acids. The fermented liquid, containing from 7 to 12 percent ethanol, is concentrated to 95 percent by a series of distillations. In the production of beverages such as whiskey and brandy, some of the impurities, which supply the flavor, are of great value. Much ethanol not intended for drinking is now made synthetically, either from acetaldehyde made from acetylene, or from ethylene made from petroleum. A small amount is made from wood pulp.

Ethanol can be oxidized to form first acetaldehyde and then acetic acid. It can be dehydrated to form ether. Other products made from ethanol include butadiene, used in making synthetic rubber; ethyl choride, used as a local anesthetic; and many other organic chemicals. Ethanol can also be mixed with gasoline to form the automobile fuel called gasohol. Ethanol is miscible (mixable) in all proportions with water and with most organic solvents. It is an excellent solvent for many substances and is used in making such products as perfumes, lacquer, celluloid, and explosives. Alcoholic solutions of nonvolatile substances are called tinctures; if the solute is volatile, the solution is called a spirit.

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