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Alcohol proof is a measure of how much ethanol (alcohol) is contained in an alcoholic beverage. The term was originally used in the United Kingdom and was equal to about 1.75 times the alcohol by volume (ABV). The UK now uses the ABV standard instead of alcohol proof. In the United States, alcoholic proof is defined as twice the percentage of ABV. The measurement of alcohol content and the statement of this content on the bottle labels of alcoholic beverages is regulated by law in many countries. The purpose of the regulation is to provide pertinent information to the consumer. == History == From the 18th century until 1 January 1980, the UK measured alcohol content in terms of "proof spirit", which was defined as spirit with a gravity of that of water, or 923 kg/m3, and equivalent to 57.15% ABV.〔 http://www.dcs.ed.ac.uk/home/jhb/whisky/swa/chap6.html〕 The term originated in the 16th century, when payments to British sailors included rations of rum. To ensure that the rum had not been watered down, it was "proved" by dousing gunpowder with it and then testing to see whether the gunpowder would ignite. If it did not, then the rum contained too much water and was considered to be "under proof". Gunpowder would not burn in rum that contained less than 57.15% ABV. Therefore, rum that contained this percentage of alcohol was defined to have "100° (one hundred degrees) proof". The gunpowder test was officially replaced by a specific-gravity test in 1816.〔 The value 57.15% is very close to the fraction = 0.5714. Thus, the definition amounts to declaring that 100° proof spirit has an ABV of . From this, it follows that to convert the ABV (expressed as a percentage, as is standard, rather than as a fraction) to degrees proof, it is only necessary to multiply by = 1.75. Thus pure, 100% alcohol will have 100×() = 175° proof, and a spirit containing 40% ABV will have 40×() = 70° proof. The proof system in the United States was established around 1848 and was based on percent alcohol rather than specific gravity. 50% alcohol was defined as 100 proof.〔 The use of "proof" as a measure of alcohol content is now mostly historical. Today, liquor is sold in most locations with labels that state its alcohol content as its percentage of alcohol by volume (ABV). The term "percent proof" has no meaning: alcoholic strength should be stated as "degrees proof" (UK) or "proof" (US) if the respective "proof" scale is being used, or "percent ABV" if it is expressed as a percentage. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Alcohol proof」の詳細全文を読む スポンサード リンク
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