Felling fluid - Felling exhaust

This is the most widely used reagent for the detection and quantification of reducing sugars. It is prepared by mixing equal amounts of copper sulfate solution (dissolve 34.6 g of CuSO ₄ ･5H _{2 O} in 500 mL of water) and sodium potassium tartrate solution (dissolve 173 g of sodium potassium tartrate and 50 g of sodium hydroxide in 500 mL of water) just before use. It is a deep blue alkaline solution in which copper(II) ions are dissolved as a complex compound. When a reducing sugar is added to this and boiled, Cu ^II is reduced to produce a red precipitate of Cu ₂ O. The reduction rate varies depending on the type of sugar, but it reacts with both aldoses and ketoses. Although the reaction is not stoichiometric, one molecule of hexose reduces approximately five atoms of copper. The sensitivity of this test is approximately 0.01 mg of glucose per mL of sugar solution. The resulting Cu ₂ O is quantified by gravimetric methods (Alleen method), quantitative methods (Bertrand method), colorimetric methods (Somogyi method), etc. This solution also forms insoluble copper complexes with polysaccharides such as hemicellulose, so it is also used in the purification of these.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

還元糖の検出，定量にもっとも広く用いられている試薬．硫酸銅溶液(CuSO₄･5H₂O34.6 g を水500 mL に溶かす)と酒石酸ナトリウムカリウム液(酒石酸ナトリウムカリウム173 g と水酸化ナトリウム50 g を水500 mL に溶かす)の等量を使用直前に混合してつくる．銅(Ⅱ)イオンが錯化合物として溶けている深青色のアルカリ溶液で，これに還元糖を加えて煮沸すると Cu^Ⅱは還元されてCu₂Oの赤色沈殿を生成する．還元速度は糖の種類によって異なるが，アルドース，ケトースともに反応する．反応は化学量論的ではないが，ヘキソース 1分子はだいたい5原子の銅を還元する．この試験の感度はだいたい糖液1 mL につきグルコース約0.01 mg である．生じたCu₂Oは，重量法(アリーン法)，定量法(ベルトラン法)，比色法(ソモジ法)などによって定量される．また，この溶液はヘミセルロースなどの多糖と不溶性の銅錯体をつくるので，それらの精製にも利用される．

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