Potassium permanganate, volumetric

Assay The initial sample is dissolved in a mixture of hot sulfuric acid and ammonium sulfate. After the dissolution is complete, the mixture is allowed to cool, and diluted with water. The suspension is then filtered, and neutralized with ammonium hydroxide. This filtrate is reduced in a Jones reductor (making use of a zinc amalgam), and then titrated with 0.1 N potassium permanganate volumetric reagent. Under these conditions, each mL of 0.1 N potassium permanganate reagent is equivalent to 7.988 mg of TiOj. 

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 Dilute 10 ml of hydrogen peroxide solution to 250 ml with DW in a volumetric flask. To 25.0 ml of this solution add 5 ml of 5 N sulphuric acid and titrate with 0.1 N KMn04 to a permanent pink endpoint. Each ml of 0.1 N potassium permanganate is equivalent to 0.001701 g of H202. 

In an experiment to determine the percentage by mass of manganese in a steel paper clip, it is necessary to prepare various concentrations of standard potassium permanganate solutions. You will learn more about this experiment on p. 88. A standard 0 0010 mol h solution of potassium permanganate is often used as a stock solution in this experiment. Dilutions of the stock solution are prepared by accurately transferring a known volume of the stock solution, using a pipette or a burette, into a volumetric flask (standard flask). The flask is then carefully filled to the graduation mark with deionised water. 

Marckwald, after a research with unsatisfactory material,4 prepared some pure tellurium dioxide from telluric acid which had been crystallised several hundred times.5 The dioxide was analysed volumetrically by oxidising to telluric acid by means of potassium permanganate, excess of the latter being determined by means of oxalic acid. The mean result obtained was 127-61. 

Estimation of Vanadium.1—Volumetric Methods.—The most convenient and the usual method for the estimation of vanadium is a volumetric process. The vanadium is first obtained in acid solution as vanadate, and reduced to the tetravalent state by one of several reducing agents which are available. The solution is then titrated in the presence of sulphuric acid with hot potassium permanganate solution, which quantitatively oxidises the lower vanadium salt to the vanadate. Using sulphur dioxide to effect the reduction, the following reactions take place —... 

Standard Preparations Dissolve 338.5 mg of mercuric chloride, in about 200 mL of water in a 250-mL volumetric flask, add 14 mL of 1 2 sulfuric acid, dilute to volume with water, and mix. Pipet 10.0 mL of this solution into a 1000-mL volumetric flask containing about 800 mL of water and 56 mL of 1 2 sulfuric acid, dilute to volume with water, and mix. Pipet 10.0 mL of the second solution into a second 1000-mL volumetric flask containing 800 mL of water and 56 mL of 1 2 sulfuric acid, dilute to volume with water, and mix. Each milliliter of this diluted stock solution contains 0.1 pig of mercury. Pipet 1.25, 2.50, 5.00, 7.50, and 10.00 mL of the last solution (equivalent to 0.125, 0.250, 0.500, 0.750, and 1.00 ptg of mercury, respectively) into five separate 150-mL beakers. Add 25 mL of aqua regia to each beaker, cover with watch glasses, heat just to boiling, simmer for about 5 min, and cool to room temperature. Transfer the solutions into separate 250-mL volumetric flasks, dilute to volume with water, and mix. Transfer a 50.0-mL aliquot from each solution into five separate 150-mL beakers, and add 1.0 mL of 1 5 sulfuric acid and 1.0 mL of a filtered solution of 1 25 potassium permanganate solution to each. Heat the solutions just to boiling, simmer for about 5 min, and cool. 

Assay Transfer a volume of sample, equivalent to about 300 mg of H2O2 and accurately weighed, into a 100-mL volumetric flask, dilute to volume with water, and mix thoroughly. Add 25 mL of 2 N sulfuric acid to a 20.0-mL portion of this solution, and titrate with 0.1 N potassium permanganate. Each milliliter of 0.1 N potassium permanganate is equivalent to 1.701 mg of H2O2. 

Procedure Transfer 10.0 mL each of the Standard Preparation and the Test Preparation to separate 25-mL volumetric flasks. Add 5.0 mL of Potassium Permanganate and Phosphoric Acid Solution to each, and mix. After 15 min, add 2.0 mL of Oxalic Acid and Sulfuric Acid Solution to each, stir with a glass rod until the solutions are colorless, add 5.0 mL of fuchsin-sulfurous acid TS (see Solutions and Indicators), dilute with water to volume, and mix. After 2 h, using a suitable spectrophotometer, concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 575 nm, using water as the blank. The absorbance of the solution from the Test Preparation is not greater than that from the Standard Preparation. PH Determine as directed under pH Determination, Appendix IIB. 

Assay Transfer about 1.2 g of sample, accurately weighed, into a 100-mL volumetric flask, dissolve in and dilute to volume with water, and mix. Pipet 10 mL of this solution into a mixture of 50.0 mL of 0.1 A potassium permanganate, 100 mL of water, and 5 mL of sulfuric acid, keeping the tip of the pipet well below the surface of the liquid. Warm the solution to 40°, allow it to stand for 5 min, and add 25.0 mL of 0.1 A oxalic acid. Heat the mixture to about 80°, and titrate with 0.1 A potassium permanganate. Each milliliter of 0.1 A potassium permanganate is equivalent to 4.255 mg of KN02. Lead Determine as directed under Lead Limit Test, Appendix IIIB, using 1 g of sample in 10 mL of water, and 4 xg of lead (Pb) ion in the control. 

Potassium Permanganate TS Use 0.1 N Potassium Permanganate (see Volumetric Solutions in this section). 

Ferrous ammonium sulphate is a stable salt at ordinary temperatures, and its solutions in the cold do not readily oxidise. Hence it is largely used in the laboratory for standardising solutions of potassium permanganate for volumetric analysis. Its solubility in water is as follows —4... 

With potassium permanganate oxidation to ferricyanide proceeds quantitatively in acid solution, the reaction affording a useful volumetric method of estimating ferrocyanidcs if carried out under certain well-defined conditions.2... 

LJswg Potassium Permanganate and Cerium(IV) Solutions Table 20-5 lists some of the many applications of permanganate and cerium(IV) solutions to the volumetric determination of inorganic species. Both reagents have also been applied to the determination of organic compounds with oxidizable functional groups. 

Figure 3-2 Preparation of 0.0100 M solution of KMn04, potassium permanganate. A 250.-mL sample of 0.0100 M KMnO solution contains 0.395 g of KMnO (1 mol = 158 g). (a) 0.395 g of KMn04 (0.00250 mol) is weighed out carefully and transferred into a 250.-mL volumetric flask, (b) The KMn04 is dissolved in water, (c) Distilled H2O is added to the volumetric flask until the volume of solution is 250. mL. The flask is then stoppered, and its contents are mixed thoroughly to give a homogeneous solution.

Caution Consult appropriate literature and ensure that safety regulations are being followed. Strong oxidants and acids are used. Conditions 0.7 % w/v of potassium permanganate in a mixture of sulfuric acid (95-97%, Merck) and phosphoric acid (85%, Aldrich) in the volumetric ratio of 2 1. Specimens are etched in 0.7 % w/v of the permanganic solution at room temperature typically over 5 h. The etched... 

Volumetric determination may be made by reducing the titanium to the trivalent condition with zinc and then titrating with potassium permanganate, ferric chloride, or methylene blue.5... 

Percentages of vanadium(IV) relative to the total vanadium can be determined volumetrically. An acid solution of a sample is titrated with a standard solution of potassium permanganate and then successively titrated with a standard solution of ammonium iron(II) sulfate by the use of diphenylamine as an indicator. The first titration corresponds to the amount of vanadium(IV) and the second to the total amount of vanadium. 

As the acid can be obtained in the pure condition it, or one of its salts, is used to standardize solutions of potassium permanganate to be used in volumetric analysis. The complete reaction is expressed by the equation —... 

Why is potassium permanganate not satisfactory as a primary standard in volumetric analysis ... 

Potassium permanganate is used in volumetric analysis as an oxidizing agent, as a bactericide, and as a disinfectant. In aqueous solution its behavior as an oxidizing agent depends on the pH of the solution. 

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