Potassium permanganate reaction with oxalic acid

Experiment 18.1 Temperature dependency of rate of reaction Potassium permanganate and acidulated oxalic acid solutions are brought to three different temperatures (in an ice bath at about 0 °C, at room temperature, and in a water bath of about 50 °C). Starting with the coldest oxalic acid solution, the potassium permanganate solution of the same temperature is added to each one. The hottest solution loses color by far the fastest. 

Harcourt and Esson were the first to study such reactions (in their case, the reaction of potassium permanganate with oxalic acid). Esson was the first to integrate the differential equation. This scheme can be treated exactly by considering the differential equations ... 

Almost simultaneously with the appearance of Guldberg and Waage s first paper of 1864, Harcourt and Esson commenced their work on reaction rates. Whereas the French and Norwegian workers had been concerned with both equilibria and reaction rates, Harcourt and Esson chose reactions which were effectively irreversible, and they were therefore able to concentrate on chemical kinetics alone. They made no claim to be measuring affinity or chemical force. They initially studied the reaction between potassium permanganate, oxalic acid and sulphuric acid, but this proved to be rather complicated. They therefore switched to the reaction between hydric peroxide and hydric iodide in acidified solution ... 

The law was formulated in this form in 1879. The idea of the rate of chemical transformation was introduced somewhat earlier by V. Harcourt and W. Esson (1865- 7). They studied the oxidation of oxalic acid with potassium permanganate and pioneered in deriving formulas for the description of the kinetics of reactions of the first and second orders. 

The common treatment methods are acidification, neutralization, and incineration. When oxahc acid is heated slightly in sulfuric acid, it is converted to carbon monoxide, carbon dioxide, and water. Reaction with acid potassium permanganate converts it to carbon dioxide. Neutralization with alkahes, such as caustic soda, yields soluble oxalates. Neutralization with lime gives practically insoluble calcium oxalate, which can be safely disposed of, for instance, by incineration. 

Some of the investigations carried out in the first half of the twentieth century were related to CL associated with thermal decomposition of aromatic cyclic peroxides [75, 76] and the extremely low-level ultraviolet emission produced in different reaction systems such as neutralization and redox reactions involving oxidants (permanganate, halogens, and chromic acid in combination with oxalates, glucose, or bisulfite) [77], In this period some papers appeared in which the bright luminescence emitted when alkali metals were exposed to oxygen was reported. The phenomenon was described for derivatives of zinc [78], boron [79], and sodium, potassium, and aluminum [80]. 

COOH)2 (aq.). Thomsen15 and Berthelot10 25 measured the heat of solution of oxalic acid. WTith Thomsen s value S= —2.26200, we have computed, for (COOH)2 (aq.), Qf= 195.3. Thomsen s15 data on the reaction of aqueous hypochlorous acid with aqueous oxalic acid yield, for (C00H)2 (aq.), Qf = 194.5. Berthelot s25 data on the reaction of gaseous chlorine with aqueous oxalic acid yield, for (COOH)2 (aq.), Qf= 194.8. Berthelot s2 data on the reaction of aqueous potassium permanganate with aqueous oxalic acid yield, for (C00H)2 (aq.), Qf=195.5. 

Oxidizing reagents such as tetravalent cerium or potassium permanganate solutions may be standardized by oxalic acid, sodium oxalate, or potassium iodide. The reactions of Ce4+ and permanganate ions with oxalic acid in acid medium are given below ... 

A potassium permanganate solution is standardized by dissolving 0.9234 g sodium oxalate in dilute sulfuric acid and then titrating with the potassium permanganate solution. The principal products of the reaction are man-ganese(II) ion and carbon dioxide gas. The titration requires 18.55 mL of the potassium permanganate solution to reach the endpoint, which is indicated by the first permanent, but barely perceptible, pink color of the permanganate ion. 

Kinetics is concerned with the rates of chemical reactions and the factors which influence these rates. The first kinetic measurements were made before 1820, but interpretation in terms of quantitative laws began with the studies on the inversion of sucrose by Wilhelmy/ the esterification of ethanol with acetic acid by Bethelot and St. Gilles, and the reaction between oxalic acid and potassium permanganate by Harcourt and Esson. These investigations established the relations between rate and concentration of reactants. The important contribution of Arrhenius for the effect of temperature was also made in the nineteenth century. 

Potassium permanganate (KMn04) is a stain remover that can be used to clean most white fabrics. However, there is one problem with using it it is a deep purple color that leaves behind its own stain. Fortunately, the purple stain can then be removed by treating the fabric with oxalic acid. The reaction is as follows. 

Unsevine (LXXXVIII) (mp 173°-174° [aJi, -t-170° in CHCI3) formed hydrobromide (mp 180°-183°), oxalate (mp 192°-194°), and methiodide (mp 249°-250°) salts (99). Oxidation of unsevine with either silver oxide (98) or chromium trioxide (56) afforded nivaline. Additional degradations of nivaline and unsevine follow the classic patterns established in the homolycorine and hippeastrine structural elucidations. Unsevine is oxidized by potassium permanganate to hydrastic acid (97, 100, 101). Hofmann degradation of either nivaline or unsevine affords the methine base LXXXIX (97, 100). In the case of unsevine, this reaction must... 

Everyday experience demonstrates that, most of the time, the rate of a chemical reaction will increase with a rise in temperature. Food will spoil outside on a hot summer day much faster than it would in a refrigerator. The decolorization of potassium permanganate by oxalic acid in a sulfuric acid solution (a reaction we already discussed in Chap. 16) is also strongly accelerated by heating (Experiment 18.1). 

With regard to the determination of oxalic acid, see the standardization of potassium permanganate, above.) An interesting extension of the oxidization reaction of oxalic acid is the determination of calcium ions. The latter are precipitated as calcium oxalate in hot acetic acid (solubility product = 10 ). The precipitate is separated out from the solution, washed, and dissolved into a 2 mol/L sulfuric acid solution. After heating, the liberated oxalic acid is titrated with permanganate. In fact, oxalic acid is simply liberated by displacement of the precipitation equilibrium ... 

The same products are formed when citric acid is oxidized by acidic solutions containing mixtures of potassium permanganate with KIO3, Kt or but also yellow solid is precipitated, probably tetraiodoacetone ( 2)2(20 [269], The oxidation reactions of citric acid by periodic acid were also discussed by Melangeau and Rub-man [270]. The over-all oxidation process includes an additional product oxalic acid... 

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