Preparation of lab reagents


 * Dr. Manisha Jain

(1) Neutral FeCl3 : Dissolve FeCl3 in water. Add NH4OH dropwise till there is a start of precipitation. Filter. Use filterate as neutral FeCl3 solution. (Precipitation indicates that HCl produced by hydrolysis of FeCl3 has been neutralized and added ammonium hydroxide is reacting with FeCl3 to precipitate Fe(OH)3)

(2)Tollen’s reagent: To AgNO 3 solution taken in a dry test tube, add dil. NaOH dropwise till precipitation is complete. Filter. Dissolve the brown residue in minimum amount of NH 3 to obtain a clear solution.

(3)Molisch reagent: 10% alcoholic solution of α-naphthol.

(4)Barfoed’s reagent: to 100 cc of acetic acid in water, add 6.5 g of cupric acetate.

(5)Fehling’s A: 17.3 g of CuSO4 in 250 ml H2O containing few drops of conc. H2SO4.

(6)Fehling B: 8.65g of sodium potassium tartarate (Rochelle salt) and 35 g of NaOH in 250 ml H2O.

(7)2,4- DNP: Dissolve a pinch of 2,4 – DNP add 1 drop of conc. H2SO4 in minimum amount of ethanol.

(8)Nitroprusside solution: Dissolve  g of nitroprusside in    ml of distilled water.

(9)Saliwanoff’s reagent: Dissolve 0.05 g of resorcinol in 100 ml of dilute (4N) HCl.

(10)Schiff’s reagent: Dissolve 0.5 g of Fuschine (Rosaniline hydrochloride) in 250 ml of warm distilled water. Cool, saturate with SO2 (solution becomes colourless or pale yellow) and dilute to 500 ml with water.

(11)Benedict A: Dissolve 8.65g of CuSO4.5H2O in 75 ml of H2O.

(12) Benedict B: Dissolve 86.5 g of sodium citrate and 50 g of anhydrous Na2CO3 in 400 ml H2O.

(13) Benedicts Reagent: Pour Benedicts solution A slowly into solution B and make up the volume to 500 ml. Mix well.

(14)Brady's reagent: Suspend 1g of powdered 2,4- dinitrophenyl hydrazine in 2 ml conc. H2SO4. Cautiously add into it 20 ml of CH3OH and warm to get a clear solution. Add 5 ml of H2O. Stir the mixture thoroughly and filter if necessary.

(15) Nesseler's reagent: Dissolve 5g of KI in minimum amount of water. To it add saturated solution of HgCl2 till a faint permanent red precipitate is formed. Mix it with 40 ml of 50% aqueous KOH solution. Allow the precipitate to settle. Dilute to 100 ml with water. Allow it to stand overnight and filter. Filterate is nesseler's reagent.

(16) Ninhydrin solution: Dissolve 0.2 g of ninhydrin in 100 ml of rectified spirit.