Permanganate oxalate titration

The hydrogen peroxide problem When oxygen of the air is present, the reactions are more complicated H2O2 is formed during the permanganate-oxalate titration according to the overall reaction... 

K permanganate by titration into Na oxalate/ dil sulfuric acid soln... 

Even though the mechanism of the reaction between oxalate and permanganate is extremely compHcated, titration under acidic conditions is extremely accurate. This is the recommended method for standardi2ation of permanganate solutions. 

Quantitative Analysis. OxaUc acid is precipitated as calcium oxalate from a solution containing oxaUc acid, and the calcium oxalate obtained is then weighed. If there are no organic substances other than oxaUc acid present, oxaUc acid can be titrated quantitatively with potassium permanganate. 

An example of catalytic action is provided by the titration of oxalates with potassium permanganate solution referred to above. It is found that even though the oxalate solution is heated, the first few drops of permanganate solution are only slowly decolorised, but as more permanganate solution is added the decoloration becomes instantaneous. This is because the reaction between oxalate ions and permanganate ions is catalysed by the Mn2+ ions formed by the reduction of permanganate ions ... 

An approximate value of the volume of permanganate solution required can be computed from the weight of sodium oxalate employed. In the first titration about 75 per cent of this volume is added, and the determination is completed at 55-60 °C. Thereafter, about 90-95 per cent of the volume of permanganate solution is added at the laboratory temperature. 

The excess of oxalic acid is titrated with standard potassium permanganate solution. 

Weigh out accurately 0.3-0.4 g potassium persulphate into a 500 mL conical flask, add 50 mL of 0.05 M-oxalic acid, followed by 0.2 g of silver sulphate dissolved in 20 mL of 10 per cent sulphuric acid. Heat the mixture in a water bath until no more carbon dioxide is evolved (15-20 minutes), dilute the solution to about 100 mL with water at about 40 °C, and titrate the excess of oxalic acid with standard 0.02 M potassium permanganate. 

The amount of oxalic acid thus decomposed under conditions where all the light is absorbed by the uranyl ion is determined by titrating a sample of the solution with potassium permanganate before and after irradiation. Since... 

Procedure Weigh accurately about 6.3 g of pure oxalic acid (AnalaR-Grade) into a 1 litre volumetric flask, dissolve in sufifcient DW and make up the volume upto the mark. Pipette out 25 ml of this solution, add to it 5 ml of concentrated sulphuric acid along the side of the flask, swirl the contents carefully and warm upto 70°C. Titrate this against the potassium permanganate solution from the burette till the pink colour persists for about 20 seconds. 

Procedure Weigh accurately about 1 g of sodium nitrite and dissolve it in DW to make 100 ml in a volumetric flask. Transfer 10 ml of this solution into a mixture of 50 ml of 0.1 N KMn04, 100 ml of water and add 5 ml of sulphuric acid along the side of the flask. Heat the contents to 40°C, allow it to stand for 5 minutes and add 25 ml of 0.1 N oxalic acid. Warm the resulting mixture to about 80°C on a steam-bath and titrate with 0.1 N KMn04 solution. Each ml of 0.1 N potassium permanganate is equivalent to 3.450 mg of NaN02. 

Thereafter, analysis was done by faster techniques based on oxalate-permanganate titrations which involved a precipitation procedure followed by quick titration of pre-heated solutions containing oxalate ions. 

Elemental composition Ca 40.04%, C 12.00%, O 47.96%. CaCOs dissolves in water in the presence of a few drops of HCl. The solution is analyzed for calcium by AA or ICP spectroscopy or by treatment with ammonium oxalate followed by titration with potassium permanganate. 

Elemental composition Mn 63.19%, 0 36.81%. The pure oxide may be characterized by x-ray crystallography. The Mn02 content in pyrolusite may be measured by titration. An excess of a standard solution of oxalic acid is added to a solution of Mn02 in sulfuric acid. After all solid Mn02 dissolves, the excess oxalic acid is measured by titrating against a standard solution of potassium permanganate (see Reactions). 

Elemental composition Na 34.32%, C 17.92%, 0 47.76%. The aqueous solution is analyzed for sodium by AA or ICP method. The oxalate ion is quantitatively determined by titration against a standard solution of potassium permanganate. 

Selenious acid readily decomposes potassium permanganate, but analytical results are untrustworthy in the presence of more than a limited quantity of sulphuric acid.1 The oxidation should be carried out at 50° C., a known quantity of 0-lN potassium permanganate being used and the excess determined either by means of standard oxalic acid solution or by electrometric titration with ferrous sulphate. In the presence of tellurium, the latter is also oxidised and should be determined in a separate sample by oxidation with potassium di-chromate, which does not oxidise the selenium, and the necessary deduction can then be made.2... 

Tellurous acid cannot be determined by oxidation with potassium permanganate in acidified solution, but in alkaline solution accurate results may be obtained by cooling to 8°-10° C. after the oxidation and slowly acidifying with dilute sulphuric acid, with continual stirring. Excess of standard oxalic acid is then added and after warming to 50° C. the remaining excess is titrated with permanganate.6... 

The equivalence point is the ideal (theoretical) result we seek in a titration. What we actually measure is the end point, which is marked by a sudden change in a physical property of the solution. In Reaction 7-1, a convenient end point is the abrupt appearance of the purple color of permanganate in the flask. Prior to the equivalence point, all permanganate is consumed by oxalic acid, and the titration solution remains colorless. After the equivalence point, unreacted Mn04 accumulates until there is enough to see. The first trace of purple color is the end point. The better your eyes, the closer will be your measured end point to the true equivalence point. Here, the end point cannot exactly equal the equivalence point, because extra Mn04, beyond that needed to react with oxalic acid, is required to exhibit purple color. 

Step 3 Heat the solution to 60°C and titrate the oxalate with standardized potassium permanganate until the purple end point of Reaction 7-1 is observed. 

Potassium permanganate can be standardized by titration of sodium oxalate (Na2C204) by Reaction 7-1 or pure electrolytic iron wire. Dissolve dry (105°C, 2 h) sodium oxalate (available in a 99.9-99.95% pure form) in 1 M H2S04 and treat it with 90-95% of the required KMn04 solution at room temperature. Then warm the solution to 55-60°C and complete the titration by slow addition of KMn04. Subtract a blank value to account for the quantity of titrant (usually one drop) needed to impart a pink color to the solution. 

One hundred and fifty milligrams of the product are dried at 105-120° C, weighed out to the nearest O.OOlg, dissolved in 250ml of water at 85°C, and 10ml of 9itf sulfuric acid are then added. The solution is titrated hot with N/10 standard sodium oxalate to the disappearance of the permanganate color. 

Other kinds of titrations are possible in addition to acid-base titrations. For example, the concentration of a solution of potassium permanganate, KMn04, can be determined by titration against a known amount of oxalic acid, H2C204, according to the following equation ... 

To calculate the molarity of the KMn04 solution, we need to find the number of moles of KMn04 present in the 22.35 mL of solution used for titration. We do this by first calculating the number of moles of oxalic acid that react with the permanganate ion, using a gram-to-mole conversion with the molar mass of H2C2O4 as the conversion factor ... 

Lime.—This could be determined by precipitation with ammonium oxalate and subsequent titration with permanganate, but in practice use is generally made of Pellet s method, which is carried out as follows ... 

---