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Ethanol, or ethyl alcohol, is commonly referred to as “alcohol.” This term is somewhat misleading, because there are numerous other alcohols. However, ethanol is probably the most commonly used and abused xenobiotic in the world. Its use is pervasive among adolescents and adults of all ages, socioeconomic groups, and represents a tremendous financial and social cost.3,197 The ethanol content of alcoholic beverages is expressed by volume percent or by proof. Proof is a measure of the absolute ethanol content of distilled liquor, made by determining its specific gravity at an index temperature. In the United Kingdom, the Customs and Excise Act of 1952 declared proof spirits (100 proof) as those in which the weight of the spirits is 12/13 the weight of an equal volume of distilled water at 51°F (11°C). Thus, 100 proof spirits are 48.24% ethanol by weight or 57.06% by volume. Other spirits are designated over or under proof, with the percentage of variance noted. In the United States, a proof spirit (100 proof) is one containing 50% ethanol by volume.

The derivation of proof comes from the days when sailors in the British Navy suspected that the officers were diluting their rum (grog) ration and demanded “proof” that this was not the case. They achieved this by pouring a sample of grog on black granular gunpowder. If the gunpowder ignited by match or spark, the rum was up to standard, 100% proof that the liquor was at least 50% ethanol. This became shortened to 100 proof (Table 80–1).

TABLE 80–1.Basic Information and Calculations

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