Potassium permanganate solution

In what way does a solution of hydrogen peroxide react with (a) chlorine water, (b) potassium permanganate solution, (c) potassium dichromate solution, (d) hydrogen sulphide 50 cm of an aqueous solution of hydrogen peroxide were treated with an excess of potassium iodide and dilute sulphuric acid the liberated iodine was titrated with 0.1 M sodium thiosulphate solution and 20.0 cm were required. Calculate the concentration of the hydrogen peroxide solution in g 1" ... 

Peroxides can usually be completely removed from a sample of ether by thorough shaking with aqueous potassium permanganate solution. 

Traces of aldehyde are produced. If ether of a high degree of purity is required, it should l>e further shaken with 0-5 per cent, potassium permanganate solution (to convert the aldehyde into acid), then with i> per cent, sodium hydroxide solution, and finally with water. 

The analytical reagent grade is suitable for most purposes. The commercial substance may be purifled by shaking for 3 hours with three portions of potassium permanganate solution (5 g. per litre), twice for 6 hours with mercury, and Anally with a solution of mercuric sulphate (2-5 g. per litre). It is then dried over anhydrous calcium chloride, and fractionated from a water bath at 55-65°. The pure compound boils at 46-5°/760 mm. 

Chakactkrisation of Unsaturatkd Aliphatic Hydrocarbons Unlike the saturated hydrocarbons, unsaturated aliphatic hydrocarbons are soluble in concentrated sulphuric acid and exhibit characteristic reactions with dUute potassium permanganate solution and with bromine. Nevertheless, no satisfactory derivatives have yet been developed for these hydrocarbons, and their characterisation must therefore be based upon a determination of their physical properties (boiling point, density and refractive index). The physical properties of a number of selected unsaturated hydrocarbons are collected in Table 111,11. 

Use a mixture of 4-5 drops of 0- 5 per cent, potassium permanganate solution and 4 ml. of dilute sulphuric acid. 

By oxidation of primary alcohols with alkaline potassium permanganate solution or with a dichromate and dilute sulphuric add, for example ... 

Test the solution so obtained for unsaturation by adding cold 1 per cent, potassium permanganate solution a drop at a time. The immediate disappearance of the purple colour and the formation of a brown turbidity indicates the presence of a double bond Baeyer a test). It must be noted that many substances, not unsaturated, decolourise warm acid or neutral potassium permanganate solution. 

Unsaturated esters decolourise a solution of bromine in carbon tetrachloride and also neutral potassium permanganate solution. 

The position of the triple bond is established by oxidation of the latter by means of alkaline potassium permanganate solution to sebacic acid, H02C(CH2)gC0jH, m.p. 133°. 

Oxidation of 10-undecynoic acid to sebacic acid. Dissolve 2 00 g. of the acid, m.p. 41-42°, in 50 ml. of water containing 0 -585 g. of pure anhydrous sodium carbonate. Saturate the solution with carbon dioxide and add O IN potassium permanganate solution (about 1500 ml.) slowly and with constant stirring until the pink colour remains for half an hour the addition occupies about 3 hours. Decolourise the solution with a httle sulphur dioxide and filter off the precipitated acid through a... 

Preparation of the sulphones. Dissolve the 2 4-dinitrophenyl-sulphide in the minimum volume of warm glacial acetic acid and add 3 per cent, potassium permanganate solution with shaking as fast as decolourisation occurs. Use a 50 per cent, excess of potassium permanganate if the sulphide tends to precipitate, add more acetic acid. Just decolourise the solution with sulphur dioxide (or with sodium bisulphite or alcohol) and add 2-3 volumes of crushed ice. Filter off the sulphone, dry, and recrystaUise from alcohol. 

Potassium permanganate test. Dissolve 0 -2 g. or 0 -2 ml. of the substance in 2 ml. of water or in 2 ml. of acetone (which gives a negative test with the reagent), and add 2 per cent, potassium permanganate solution dropwise. The test is negative if no more than 3 drops of the reagent are decolourised. 

Aqueous potassium permanganate solutions are not perfectiy thermodynamically stable at 25°C, because Mn02, not MnO is the thermodynamically stable form of manganese in water. Thus permanganate tends to oxidize water with the evolution of oxygen and the deposition of manganese dioxide, which acts to further catalyze the reaction. 

The kinetics of the reaction are relatively slow and permanganate solutions exhibit greatest stabiUty around a neutral pH. The decomposition rates increase below pH 3 or above pH 10. Potassium permanganate solutions are stable at elevated temperatures, up to approximately 3 N sodium hydroxide, above which decomposition into manganate occurs. 

Both technical- and reagent-grade phosphoms pentoxide is typically >99% P O q. Phosphoms pentoxide sublimes near 360°C at atmospheric pressure. Lower oxides, which may account for <0.3% (as P40 ) in technical-grade material, are present at <0.02% in reagent-grade phosphoms pentoxide. Lower oxides are detected by decolorization of a dilute potassium permanganate solution (Table 11). 

Silver Permanganate. Silver permanganate [7783-98-4] AgMnO, is a violet soHd formed when a potassium permanganate solution is added to a silver nitrate solution. It decomposes upon heating, exposure to light, or by reaction with alcohol. 

Surface oxidation short of combustion, or using nitric acid or potassium permanganate solutions, produces regenerated humic acids similar to those extracted from peat or soil. Further oxidation produces aromatic acids and oxaUc acid, but at least half of the carbon forms carbon dioxide. 

The purification of diethyl ether (see Chapter 4) is typical of liquid ethers. The most common contaminants are the alcohols or hydroxy compounds from which the ethers are prepared, their oxidation products (e.g. aldehydes), peroxides and water. Peroxides, aldehydes and alcohols can be removed by shaking with alkaline potassium permanganate solution for several hours, followed by washing with water, concentrated sulfuric acid [CARE], then water. After drying with calcium chloride, the ether is distilled. It is then dried with sodium or with lithium aluminium hydride, redistilled and given a final fractional distillation. The drying process should be repeated if necessary. 

Aconitine produces an intense tingling sensation when a drop of a solution, 1 in 10,000, is applied to the tip of the tongue. It also gives a characteristic unstable, crystalline precipitate when a few drops of potassium permanganate solution are added to a solution of the alkaloid in dilute acetic acid. The formation of acetic acid when the alkaloid is heated dry, or of benzoic acid when it is hydrolysed by alkali, have also been suggested as identification tests. For the recognition of minute quantities a biological test is probably the best procedure. ... 

Chameleon, n. chameleon chameleon mineral (potassium manganate). -Idsung, /. potassium permanganate solution. 

As a more complex case, suppose we want to write the equation for the reaction that occurs when hydrogen sulfide gas, H2S, is bubbled into an acidified potassium permanganate solution, KMn04. When we do this, we observe that the purple color of the MnO ion disappears and that the resulting mixture is cloudy (sulfur particles). From Appendix 3 we find the two halfreactions... 

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 ... 

This reaction is slow in acid solution, but it is very rapid in neutral solution. For these reasons, potassium permanganate solution is rarely made up by dissolving weighed amounts of the purified solid in water it is more usual to... 

Calculation. It is evident from the equation given above that if the weight of arsenic(III) oxide is divided by the number of millilitres of potassium permanganate solution to which it is equivalent, as found by titration, we have the weight of primary standard equivalent to 1 mL of the permanganate solution. 

The following reaction occurs when potassium permanganate solution is added to hydrogen peroxide solution acidified with dilute sulphuric acid ... 

If a solution of a nitrite is titrated in the ordinary way with potassium permanganate, poor results are obtained, because the nitrite solution has first to be acidified with dilute sulphuric acid. Nitrous acid is liberated, which being volatile and unstable, is partially lost. If, however, a measured volume of standard potassium permanganate solution, acidified with dilute sulphuric acid, is treated with the nitrite solution, added from a burette, until the permanganate is just decolorised, results accurate to 0.5-1 per cent may be obtained. This is due to the fact that nitrous acid does not react instantaneously with the permanganate. This method may be used to determine the purity of commercial potassium nitrite. 

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