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oo Experiment No. 05 ee, , Aim: To perform the limit test for Iron for the given test sample., Requirements:, (a) Glassware: Nesslers' cylinder, measuring cylinder and glass rod., (b) Chemicals: Citric acid (20%), thioglycollic acid, ammonia solution (10%), standarg, , iron solution and sulphuric acid., Principle:, , This test is based on the formation of purple colour by reaction of iron with thioglycollic, acid to form ferrous thioglycollate in the presence of ammonium citrate., , Ammonium ., Fe +cH,sH —tlrate oy gy 00c + 2H, ms, |, e, ww, COOH coo~ HSH,C, Thioglycoilic acid Ferrous thioglycollate, , The intensity of colour produced by test solution is compared with the standard solution, obtained by taking standard iron solution containing 0.04 mg of iron., , ‘Scanned with CamScanner
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A Practical Book of Pharmaceutical Inorganic Chemistry, , Note:, , Limit Tests, , 1) Citric acid reacts with ammonia solution, giving ammonium citrate, which act as a, buffer. The citrate ion also prevents the precipitation of iron by ammonia by forming, , a complex with it., , 2) Thioglycollic acid not only reacts with ferrous ions, but it also reduces ferric ions to, , ferrous ions., Reagent Preparations:, , Standard solution: Accurately weighed 0.1726 g of ferric ammonium sulphate is, , dissolved in 10 ml of 0.1N sulphuric acid (H)SO,) and the volume make up to 1000 ml, , with water., °, , Citric acid (20%): Dissolve 20g of iron free citric acid in 100 ml of distilled water., Iron free ammonia solution: Dilute ammonia solution i.e. 10% ammonia., , , , , , Procedure:, Test Standard Reasons, 1. Dissolve specified . Place 2 ml of the|1. The aqueous solution will, quantity of test standard iron solution leach out all the iron present, , substance as given in, monograph or prepare a, solution as directed in, individual monograph., , (equal to 0.04 mg Fe) in, Nesslers’ cylinder and, add 40 ml in distilled, water., , in the sample or test., , , , 2. Add 2 ml of 20% solution, of iron free citric acid, , (FeT)., , . Add 2 ml of 20%, , solution of iron free, citric acid (FeT)., , . Citric acid prevents the, , 2Fe + 10NH3 — 2Fe(NH;)s + 5H,, CeHgO, + Fe > Fe(CgHeO). + 2H2, , precipitation of iron with, ammonia and keeps iron in, solution even in the presence, of ammonia by forming, complex with iron as iron, citrate., , , , 3. Add 0.1 ml of, thioglycollic acid (FeT)., , , , , , . Add 0.1 ml of, , thioglycollic acid (FeT)., , 3. Thioglycollic acid, , 2HSCH;COOH + Fe —, , HSCH,COOH + Fe?” ->, , , , converts, ferric ions to ferrous ions., , Fe** + 2H’ + HSCH,COO™, Thioglycollic acid further, reacts with ferrous ion to, form ferrous thioglycollate., , , , 2H" + (HSCH,COO),Fe, , , , ... (Contd.), , , , Scanned with CamScanner, , inc
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Limi, , A Practical Book of Pharmaceutical Inorganic Chemistry ee im t Test, _ >, sons, — Standard | Reasons, , | i sohirtiet rous — thioglycoll, 4 4, Make this solution | 4. Make this solution | 4. The ferrou — ate, i" alkaline with iron free alkaline with iron free formed a sia in|, fi ammonia solution (FeT). ammonia solution (FeT). medium but ine |, medium it gives purple |, colour. |, : Equal volumes of test and |, , 5. Dilute to 50 ml mark with | 5. Dilute to 50 ml mark | 5. Equa, , standard are compared easily, |, , distilled water. with distilled water., , , , , , , , FeT: Test for iron free., Conclusion:, , If the intensity of purple colour in standard is more than tha, , complies limit test of iron as per LP. 1996., HE BD ED, , t in the test, the Sample, , ‘Scanned with CamScanner
