Permanganate-stabilized solutions

Figure 3. Apparatus for analyzing the mercury in the permanganate-stabilized solutions...

A stock solution of 3.0% potassium permanganate in 10% nitric acid (prepared fresh daily) was used to stabilize the mercury collected in the rinses from the sampling train. The stabilized solutions were then returned to TraDets Columbus, Ohio laboratory for analysis. 

The stability of the heterocyclic ring toward oxidation by permanganate depends on the experimental conditions. In acid media the ring is not cleaved, and acetylisoxazoles are readily prepared from isopropenyl derivatives.2-Isoxazolines are dehydrogenated into isoxazoles (cf. 192 193). The stability of the heterocyclic ring is also observed when this oxidation is carried out in acetone solution. It is of interest that this method allows the preparation both of... 

Cerium(IV) sulphate solutions are remarkably stable over prolonged periods. They need not be protected from light, and may even be boiled for a short time without appreciable change in concentration. The stability of sulphuric acid solutions covers the wide range of 10-40 mL of concentrated sulphuric acid per litre. It is evident, therefore, that an acid solution of cerium(IV) sulphate surpasses a permanganate solution in stability. 

Potassium dichromate exhibits much greater stability in aqueous solution in comparison to potassium permanganate. Potassium dichromate possesses an inherent oranage colour that is not intense enough to serve its own end-point signal, specifically in the presence of the green Cr3+ ion, which is supposed to be present at the end-point. Hence, redox indicators are usually employed to locate the exact end-point e.g., barium diphenylamine sulphonate. 

Rees, T., The Stability of Potassium Permanganate Solutions, J. Chem. Educ., 64, 1058, 1987. 

Unlike other [2.2]paracyclophanes (see below), 20a exhibits remarkable chemical stability. It is inert towards bromine in carbon tetrachloride, permanganate solution, and maleic anhydride, and cannot be reduced with Pd/C or nickel at room temperature under 1 atm hydrogen pressure. 

Tricresylphosphate from receptacle 9 enters flusher 11, which is a cylindrical apparatus with an agitator. First of all, tricresylphosphate is washed with 3% sodium hydroxide to neutralise residual hydrochloric acid and separate cresol (the allowable cresol content in tricresylphosphate is 0.6 g/1). It is also recommended to treat the product with diluted solution of potassium permanganate to improve the colour and oxidation stability of tricresylphosphate. 

In the original analytical method developed by Freudenberg and coworkers, wood was first subjected to alkaline hydrolysis at high temperature followed by a methylation with dimethyl sulfate The free phenolic hydroxyl groups were converted by this treatment to methoxyl groups and the phenolic units were thus stabilized toward oxidative breakdown The oxidation step was carried out by addition of portions of solid potassium permanganate at a pH at or near 7 until the purple color of the solution remained (Freudenberg et al 1936)... 

Figure 15-2 (left) depicts several titration curves of Fe(II) with permanganate. Beyond the end point the experimental curves differ from the theoretical shape, which is nearly flat beyond the end point (5-equivalent reduction). The essential symmetry of the curves suggests that the potential is determined by the Mn(III)-Mn(II) couple beyond the end point. Evidence for this behavior can be seen in solutions containing sulfate or phosphate, which tend to stabilize Mn(III) (Section 17-1). That sulfuric and phosphoric acids have about the same effect before and after the end point is consistent with the similarity of the behavior of the Mn(III)-Mn(II) and the Fe(III)-Fe(II) systems with respect to changes in activity coefficients as well as with respect to hydrolysis and complex formation. 

Determination of iron The most important applications of dichromate involve either directly or indirectly the titration of Fe(II). An excess of standard Fe(II) can be added to determine oxidants, or an excess of Fe(III) to determine reductants. These determinations usually can be carried out equally well with Ce(IV). For routine applications, however, the low cost and ease of preparation of standard solutions and the great stability of dichromate offer some advantages. Permanganate is at a disadvantage, expecially if hydrochloric acid solutions are to be used. 

However, the tendency of permanganate to oxidize chloride ion is a disadvantage because hydrochloric acid is such a useful solvent and, furthermore, KMnOd solutions have limited stability. 

Stability and metal ion salt solubilities of the sila-crowns have not been quantitatively evaluated. The sila-17-crown-6 materials offer simple qualitative evidence of complex formation. Potassium permanganate is mixed with chlorobenzene. The salt rapidly settles and no coloration of the chlorobenzene is observed. The addition of 1-2% of the silacrown produces the characteristic deep purple color of solvated potassium permanganate. After 1 hour vinylsilacrown solutions turn brown and a fine percipitate is observed, presumbly due to silacrown promoted oxidation of its own vinyl group. 

As may be seen from Tables IV and V, Fischer and Delbriick s iso-trehalose is probably identical with /3,j8-trehalose. The a,j8-trehalose claimed first in 1918 reduced neither Fehling solution nor neutral permanganate. It was formulated as containing two D-glucopyranose residues, and its specific rotation (compared to that of a,a-trehalose) indicated that it was probably the a,fi isomer. The stability of a,a-trehalose to hydrolysis by N hydrochloric acid (compared to the lability of sucrose) favored the pyranoid ring for the two moieties. 

The urine sample is diluted with 10 mL nitric acid (1.5%), 100 p.L potassium permanganate solution, 5% in water (for stabilization), and 50 p,L octanol (as an antifoaming agent) is added and the mercury vapor is released immediately from the sample by the induction of sodium borohydride solution (3% in 1% sodium hydroxide). Aqueous calibration standards can be used [100]. 

Chemical stability of compounds K-1, K-2, K-3 and K-4 solutions to different chemical reagents during 90 day has been studied. For this purpose prepared films (thickness 200-300 microns) were lowered to the solution. After certain interval of time the films were took from a solution and checked external changes of sheets. The data of Table 7 show some swelling of samples after their stay in solutions 0.1% of potassium permanganate and 10% of nitric acid in which samples changed external parameters. 

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