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|Section2= |Section7= |Section8= }} Indigo dye is an organic compound with a distinctive blue color (see indigo). Historically, indigo was a natural dye extracted from plants, and this process was important economically because blue dyes were once rare. A large percentage of indigo dye produced today – several thousand tons each year – is synthetic. It is the blue often associated with blue jeans. ==Uses== The primary use for indigo is as a dye for cotton yarn, which is mainly for the production of denim cloth for blue jeans. On average, a pair of blue jean trousers requires 3–12 g of indigo. Small amounts are used for dyeing wool and silk. Indigo carmine, or indigo, is an indigo derivative which is also used as a colorant. About 20 million kg are produced annually, again mainly for blue jeans.〔Elmar Steingruber "Indigo and Indigo Colorants" Ullmann's Encyclopedia of Industrial Chemistry 2004, Wiley-VCH, Weinheim. 〕 It is also used as a food colorant, and is listed in the United States as FD&C Blue No. 2. 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「indigo dye」の詳細全文を読む スポンサード リンク
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