本尼迪特試劑，也稱班氏試劑、本尼迪克試劑、本尼迪克試液或班乃德試劑，是一種藍(lán)色化學(xué)試劑,為斐林試劑的改良試劑。

反應(yīng)原理：檸檬酸鈉和Cu2+生成絡(luò)合離子，此絡(luò)合離子與葡萄糖中的醛基反應(yīng)生成紅黃色沉淀。

首先，將需測試的樣本溶解于水中，加入少量的班氏試劑，搖勻后將此混合物在沸水中加熱。反應(yīng)時(shí)間約為3分鐘。如果測試樣本是還原糖，混合物中會(huì)形成紅黃色的沉淀物。這是因?yàn)檫€原糖會(huì)將硫酸銅中的二價(jià)銅離子(Cu2+)還原成一價(jià)亞銅離子(Cu+)，并以氧化亞銅(Cu2O)的形式沉淀出來。如果溶液中還原糖含量較低，產(chǎn)生的氧化亞銅便會(huì)相應(yīng)減少，因此試驗(yàn)后可能只會(huì)出現(xiàn)綠色、混濁的黃色或橙色沉淀物。
鑒定還原性糖過程

1 取一支試管，注入2mL待測樣品
2 向試管內(nèi)注入2mL本尼迪克試劑
3 將這支試管放進(jìn)盛有開水的大燒杯中，用酒精燈加熱煮沸2分鐘左右。
4 觀察溶液顏色

結(jié)果
非還原性糖如蔗糖，淀粉，纖維素等呈陰性
還原性糖如葡萄糖，果糖，半乳糖等呈陽性
 

常溫保存，有效期12個(gè)月

Benedict's reagent (often called Benedict's qualitative solution or Benedict's solution) is a chemical reagent named after American chemist Stanley Rossiter Benedict.


Benedict's solution is a deep-blue solution used to test for the presence of the aldehyde functional group, - CHO. It is an aqueous alkaline mixture of CuSO4 and sodium citrate. Here sodium citrate is the complexing agent that keeps Cu2+ in solution, which would otherwise precipitate as cupric carbonate. The substance to be tested is heated up to 95 °C (for example, in a water bath) with Benedict's solution; formation of a brick-red precipitate indicates presence of the aldehyde group in relatively high concentrations. Since simple sugars (e.g., glucose) give a positive test, the solution is used to test for the presence of glucose in urine, a sign of diabetes. One litre of Benedict's solution contains 173 grammes sodium citrate, 100 grammes sodium carbonate, and 17.3 grammes cupric sulphate pentahydrate. It reacts chemically similarly to Fehling's solution; the cupric ion (complexed with citrate ions) is reduced to cuprous ion by the aldehyde group (which is oxidised), and precipitates as cuprous oxide, Cu2O.