The overall chemical equation representing the thermal decomposition of potassium permanganate up to ≈300°C is given approximately
by: 10 KMnO4→2.65 K2MnO4+[2.35 K2O·7.35·MnO2.05]+6O2, the bracketed material being δ-MnO2. The experimental mass loss in air is ≈12% and the enthalpy of decomposition is ≈10 kJ/mol of KMnO4. Analysis of published kinetic studies of the decomposition show that most of the results can be represented by the Prout-Tompkins
equation ln (x/(1−x))=kTt+constant, and insertion of the rate constants into the Arrhenius equation gives an activation energy for decomposition of
≈150 kJ/mol of KMnO4. Although the kinetic studies have always been interpreted in terms of a single type of chemical decomposition, with the
different rates encountered during the course of the decomposition ascribed to physical effects, X-ray diffraction studies
by Boldyrev and co-workers have shown that the reaction actually occurs in two stages, with essentially all the KMnO4 transformed into K3(MnO4)2, δ-MnO2 and O2 in the first stage, and the K3(MnO4)2 then decomposing into K2MnO4 and more δ-MnO2 and O2 in the second stage. We have confirmed the Boldyrev diffraction results and extended them by measuring the kinetics of the
appearance and disappearance of K3(MnO4)2 by an X-ray diffraction method. Our earlier isotopes studies have shown that the oxygen molecules come from oxygen atoms
produced by breaking Mn−O bonds in different permanganate ions i.e. the decomposition mechanism is interionic. We conclude
by summarising what is, and is not, currently known about the thermal decomposition of potassium permanganate up to ≈300°C.
The chemical effects of56Mn-recoils following neutron capture produced in mixed crystals /KMnO4–LiClO4, KMnO4–NaClO4 and KMnO4–KClO4/ have been investigated. A linear increase of initial retention with the mol fraction of perchlorate was observed which is tentatively ascribed to the tendency to form species having structures similar to that of the host matrix. The ultimate chemical fate of the manganese atom also depends on the conditions of the immediate chemical environment of the atoms /e.g. Li, Na, K/ at rest in the crystal. The results are discussed in terms of retention and non-retention reactions invoking a mechanistic model involving metal and ligand-vacancy exchange, substitution and transfer reactions.
The paper discusses a part of the tragedy
by Sophocles from the point of view of experimental chemistry. One of the protagonists of the tragedy tells in a most lively and pictorial way how the preserved blood of the dying Centaur, Nessus, attacked and dissolved a piece of wool. One is inclined to think that the text relates some personal observation of the author. We tried to prepare a liquid, with the appearance of clotted blood, which attacks wool as described by Sophocles. The starting material we chose was related to the myth, and the methods and additives we used were or, at least, could have been at the disposal of the Athenians in the 5th century BC. After having carried out a number of simple experiments we concluded that some mixtures of potassium permanganate
sulphuric acid fit the requirements.
Professor Vladimir V. Boldyrev has made numerous important contributions to a wide range of chemical topics, not only limited
to studies of the decompositions of solids. Of particular value has been his emphasis on exploring, in detail, the chemical
steps participating in the thermal reactions of solids by carefully designed experiments that rely on more observational evidence
than the run-of-the-mill collection of overall kinetic data. Some of these major contributions to both the theory and the
uses of solid-state reactions are identified here and discussed in relation to his illuminating and fundamental mechanistic
studies of the thermal decompositions of silver oxalate, ammonium perchlorate, potassium permanganate and the dehydration
of copper sulfate pentahydrate.
cephalosporin antibiotics, using stress agents such as hydrogen peroxide at different concentrations (0.1 and 0.3%), sodium thiosulfate, potassiumpermanganate, iodine solution, and ascorbic acid. In previous researches, we elaborated also simple and rapid TLC
glycerol standard were spotted onto an activated pre-coated silica gel HPTLC GF 254 plate f (10 × 10 cm 2 ) in duplicate. The plate was developed, air dried, and then was sprayed with the chromogenic agent alkaline potassiumpermanganate (1.5 g KMnO 4
It has been shown that the exothermic decomposition of KMnO4 in vacuum is accompanied by a significant self-heating effect. It manifests itself in the reduction of the molar enthalpy
of the reaction, determined by the third-law method. In comparison with the value 138.3±0.6 kJ mol−1 that is valid for the decomposition of KMnO4 under atmospheric pressure at 493–553 K, the molar enthalpy in vacuum (10−4-10−7 bar) at 484–511 K varies in the range of 136 to 126 kJ mol−1. This is related to the reduction of the thermal conductivity of residual air in the furnace and, as a result, to the self-heating
of the reactant, that accelerates the exothermic reaction. A simple method of evaluation of the self-heating effect has been
developed. By analogy with the known method for evaluation of the self-cooling effect, it is based on the determination of
the molar enthalpy by the third-law method at two different temperatures. The increase of sample temperature above the furnace
temperature Tf in the case of the exothermic decomposition of KMnO4 in a high vacuum and Tf≥490 K reaches a few tens of degrees.
A novel electrolytic method has been developed for destroying organic matter in urine. A combination of potassium permanganate, sulfuric acid and nitric acid has yielded about 99% destruction in initial organic content of urine within two hours when electrolysis is carried out with an applied voltage of about 2.5 V, while maintaining a current density of 8.23 mA/cm2 at 373 K.