Standardization permanganate

The detection and determination ot the perchlorates.—The perchlorates give no precipitates with silver nitrate or barium chloride soln. cone. soln. give a white crystalline precipitate with potassium chloride. Unlike all the other oxy-acids of chlorine, a soln. of indigo is not decolorized by perchloric acid, even after the addition of hydrochloric acid and they do not give the explosive chlorine dioxide when warmed with sulphuric acid unlike the chlorates, the perchlorates are not reduced by the copper-zinc couple, or sulphur dioxide. Perchloric acid can be titrated with —iV-alkali, using phenolphthalein as indicator. The perchlorates can be converted into chlorides by heat and the chlorides determined volumetrically or gravimetrically they can be reduced to chloride by titanous sulphate 28 and titration of the excess of titanous sulphate with standard permanganate they can be fused with zinc chloride and the amount of chlorine liberated can be measured in terms of the iodine set free from a soln. of potassium iodide and they can be... 

Another method which is applicable also to the estimation of solutions containing sulphites and hydrogen sulphites is the addition of a known excess of acidified hydrogen peroxide to the solution of sulphurous acid. The excess of peroxide may then be titrated with standard permanganate solution. The reactions are as follows ... 

Neither silver bromide nor iodide react thus, and it is possible to estimate silver chloride in presence of iodides by means of this reaction, the excess of potassium ferroeyanide remaining after filtration being determined by titration with standard permanganate.3... 

Example 2. A solution of potassium permanganate was standardized by determining the volume necessary to oxidize an acidic solution of ferrous iron. It was found that 0.1135 g of pure iron wire, when dissolved in acid and converted to the ferrous salt (containing ferrous ions, Fe++), required 23.85 ml of the standard solution of potassium permanganate to oxidize it to ferric ion, Fe+ + +. It was also found that 0.2281 g of iron ore, when converted to a solution of ferrous iroif in acid, required 22.35 ml of the standard permanganate solution to reach the end point. What is the normality of the permanganate solution, and what is the percentage of iron in the ore ... 

Standardized permanganate solutions should be stored in the dark. Filtration and restandardization are required if any solid is detected in the solution or on the walls of the storage bottle. In any event, restandardization every 1 or 2 weeks is a good precautionary measure. 

Solutions containing excess standard permanganate should never be heated because they decompose by oxidizing water. This decomposition cannot be compensated for with a blank. It is possible to titrate hot, acidic solutions of reductants with permanganate without error, however, provided that the reagent is added slowly enough so that large excesses do not accumulate. 

The reaction between permanganate ion and oxalic acid is complex and proceeds slowly even at elevated temperature unless manganese(II) is present as a catalyst. Thus, when the first few milliliters of standard permanganate are added to a hot solution of oxalic acid, several seconds are required before the color of the permanganate ion disappears. As the concentration of manganese(ll) builds up, however. the reaction proceeds more and more rapidly as a result of autocatalysis. 

Volumetric methods for determining columbium are rapid and fairly satisfactory since tantajum does not interfere. But tungsten, molybdenum, and titanium must be completely removed. The methods depend on the reduction of pentavalent columbium to the trivalent condition by means of zinc, then the oxidation by standard permanganate. Taylor s method3 makes the reduction in a Jones reductor and the titration in an atmosphere of C02. Levy s method4 carries out the reduction and titration in an atmosphere of hydrogen in a conical flask from which the air is excluded. 

The SO2 present in air is mainly responsible for the acid rain phenomenon. Its concentration can be determined by titrating against a standard permanganate solution as follows ... 

If we want to determine hydrogen peroxide concentration, this reaction can be carried out as a redox titration, using a standard permanganate solution. 

In neutral or slightly alkaline solutions in the dark, decomposition is immeasurably slow. It is, however, catalyzed by light so that standard permanganate solutions should be stored in dark bottles. 

For the active oxygen determination a known excess of standard ferrous ammonium sulfate was employed in dissolution of the sample. The excess was then titrated with standard permanganate. 

The filtrate from the original reaction is diluted by pouring it into a 250-mL volumetric flask, diluting to the mark with water, and then mixing thoroughly. An aliquot consisting of 10.00 mL of this diluted solution is pipetted into a 125-mL Erlenmeyer flask, approximately 25 mL of water is added, and the solution is made basic. What volume of the standard permanganate... 

Analysis for the hydroxylamine content is effected by the Raschig method. The recommended procedure is a modification of the method given by Scott. Approximately 0.1 g. of sample is dissolved in 75 ml. of water in an Erlen-meyer flask and 30 ml. of a saturated solution of iron(III) ammonium sulfate is added, followed by 10 ml. of 50 per cent sulfuric acid. The solution is boiled for 10 minutes, treated with approximately 5 to 10 ml. of phosphoric acid to reduce the color, then diluted with 200 ml. of water and titrated immediately with standard permanganate solution. 

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