Metal permanganates

The density of the alkaU metal permanganate salts increases with the atomic number of the Group 1 (IA) cation, whereas the corresponding aqueous solubihty decreases (106). At room temperature aqueous solubiUty decreases from about 900 g/L for NaMnO to 60 g/L for KMnO, and to 2.5 g/L for CsMnO. The solubihty of potassium permanganate in water as a function of temperature is as follows ... 

Metal chlorates Lead dioxide Metallic permanganates Metallic dichromates Nitric acid (concentrated)... 

Pyridine, CsHs N, like ammonia, forms complexes with various metallic permanganates. In general, they are more or less sol in w and very sol in pyridine. When heated rapidly they expld, but decompose when heated slowly. The / burn vigorously when moistened with sulfuric acid or when suddenly compressed. They are unstable and lose pyridine even at RT, and for this reason should be prepd and dried at 0°... 

The effects of pre-irradiation [908], although still marked, were less for a given dose than those observed for the alkali metal permanganates. The other Group IIA permanganates are obtained as hydrates. 

The G-riesheim Elektron Company2 use a closed diaphragm cell for preparing metallic permanganates, which is fitted with tubes for the escape of electrolytic gas. Their method for preparing the calcium salt is as follows The cathode compartment contains caustic potash solution, and the anode compartment is filled with saturated manganate... 

Contacting the cross-linked RO polyamide membrane with ions to form a membrane ion complex, treating the membrane ion complex with an aqueous solution of alkali metal permanganate to form manganese dioxide crystals in the membrane, and finally dissolving the crystals [49]. 

When the gaseous products are simple and can be readily predicted from the composition of the reactant, e.g. nitrogen from metal azides or oxygen from metal permanganates, it may be possible to determine the overall stoichiometry from simple gas-law calculations from pressures of gas collected under calibrated conditions. Even such systems, however, may yield atomic or ionic, rather than molecular, species as intermediates [76] and these require more specific methods of detection. 

This chapter considers together the thermal decompositions of metal salts of inorganic oxyacids. The decompositions of ammonium salts of these oxyacids (and other anions) are discussed in Chapter 15. The decomposition of potassium permanganate is considered first because it represents one of the earliest solid state reactions that was subjected to detailed mechanistic investigation. Substantial interest in the reaction has continued and has been extended to other metal permanganates. 

It seems probable that the reactivities of the alkali metal permanganates are predominantly controlled by the ease of anion disintegration. The values of , are similar. Subsequent reactions, however, vary with the cation present. No analogue of K3(Mn04)2 is formed from the Cs salt [16] and that of Rb is less stable. The residual products (other than M2Mn04) are difficult to characterise, apparently containing some uncrystallized material, consistent with the possible intervention of an amorphous or molten interface phase. 

Attempts at identifying the influence of structme on stability have generally been inconclusive. For example, some alkali metal permanganates with comparable stmctures show similarities of decomposition behaviour [29], while, in contrast, the decompositions of several cobalt(lll) ammine azides show little evidence of structural influences [76], Significant differences in behaviour were found for the various crystal forms of the LiK tartrate hydrates [87] and, also, for the dehydrations of the isomorphic alums [20,43], However, some reactants, for example those prepared by the dehydration of hydrated metal carboxylates [5], may be amorphous to X-rays, thus preventing recognition of any control of stability by crystal structure. 

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