. Estimation of oxalic acid Aim : To estimate the amount of oxalic acid dissolved in ml of the given solution volumetrically. For this you are given with a standard solution of ferrous ammonium sulphate (FAS) of normality . N and potassium permanganate solution as link solution.
Principle: During these titrations , oxalic acid is oxidized to CO and MnO - ions (from KMnO ) is reduced to + Mn ion. Oxidation : + colourles Pink s 8H + 5e Mn 4H M nO − + → Reduction : + colourles Pink s 8H + 5e Mn 4H M nO − + → Overall reaction : + (COOH) 2MnO 6H 10CO 2Mn 8H O → Since one mole oxalic acid releases moles of electrons, the equivalent weight of oxalic acid = (oxalic acid is dihydrated) Short procedure: s.no Content Titration-I Titration-II Burette solution KMnO KMnO Pipette solution ml of standard FAS ml of unknown oxalic acid Acid to be added 20ml of 2N H SO (approx) 20ml of 2N H SO (approx) Temperature Lab temperature – C Indicator Self-indicator ( KMnO ) Self-indicator (KMnO ) End point Appearance of permanent pale pink colour Appearance of permanent pale pink colour Equivalent weight of oxalic acid = Procedure : Titration–I (Link KMnO )Vs ( Standard FAS ) Burette is washed with water, rinsed with KMnO solution and filled with same KMnO solution up to the zero mark. Exactly ml of standard FAS solution is pipetted out into the clean, washed conical flask. To this FAS solution, approximately 20ml of 2N sulphuric acid is added.
This mixture is titrated against KMnO Link solution from the burette. KMnO is added drop wise till the appearance of permanent pale pink colour. Burette reading is noted and the same procedure is repeated to get concordant values. organic organic - - - - Titration –I (Link KMnO )Vs ( Standard FAS solution) s.no Volume of standard FAS (ml) Burette readings