The oxides of manganese

The following redox potentials are given for the oxidation of manganese(II) to manganese(III) in acid and alkaline solution. 

Fused potassium nitrate is a powerful oxidising agent (cf. the oxidation of manganese compounds, p.. IS6 ... 

Both ions can be removed by oxidation and subsequent filtration. Aeration is adequate for iron(II) oxidation at above pH 6, but the oxidation of manganese(II) is much too slow, even at higher pH values, for effective removal. Potassium permanganate or chlorine dioxide is frequently used for the oxidation of manganese however, their use must be foHowed by coagulation prior to filtration because of the formation of coHoidal Mn02. 

To prepare sabinenic acid for the identification of the terpene, Wallach operates as follows 10 grams of the crude terpene are mixed with the theoretical amount of potassium permanganate in water at ice temperature. The oxide of manganese is filtered off, the liquid rendered acid and extracted with ether, and the ethereal solution shaken with caustic soda solution. The sodium salt is very sparingly soluble, and is precipitated, collected, and decomposed with dilute sulphuric acid and purified by a further solution in ether. It must be well dried in a desiccator before its melting-point is determined. Sabinene has the following constitution —... 

The oxidation of manganese dioxide to manganate by solid alkafi-chlorate mixtures becomes explosive above 80-90°C at pressures above 19 kbar. 

Although the heavier alkali-metal compounds of the oxides of manganese, cobalt, chromium, and... 

The oxides of manganese give spectra, shown in Fig. 5, where the valence shift from +2 to higher (+3, +4) is the outstanding feature. The MnO spectrum shows extended structure probably related to the simple crys-... 

In the autumn of the same year, Arfwedson completed a beautiful research on the oxides of manganese. He determined the per cent of... 

The oxide of manganese having been used a second time, may be again recovered a third and a fourth time and if no lime or alkali-waste has been UBed in neutralizing the excess of acid, it may be recovered on indefinite number of times. 

If a plot of log [-dPddt] versus log[A] is a straight line, the slope of the line is the reaction order with respect to A. Figure 7.19 represents Mn2+ oxidation at pH 8.5 and p02 0.2 obtained by pH-stat technique. The technique utilizes a pH electrode as a sensor so that as OH is consumed (during Mn2+ oxidation), the instrument measures the rate of OH- consumption and activates the autoburete to replace the consumed OH-. It is assumed that for each OH- consumed, an equivalent amount of Mn2+ is oxidized. These pH-stat data clearly show that the first part of the oxidation of manganese is zero-order, whereas the second part is first-order. Keep in mind, however, that these particular reaction orders are strictly empirical and without necessarily any mechanistic meaning. 

The oxidation of manganese (Reaction 12.4) shows that the process produces excess hydrogen ions. The best way to alleviate this acid-producing problem is to lime the ponds with excess calcium carbonate. The pH will be maintained at about 7-8 and there will always be enough hydroxyls to neutralize the acid generated by the oxidation of manganese. 

In summary, the two most important factors in removing iron and manganese from water are high pH and the presence of an oxidizer. One of the most effective available oxidizers for the oxidation of manganese is calcium hypochlorite. 

Mn02 is a darkish-brown precipitate. As an example the oxidation of manganese(II) salts can serve ... 

This may be identified (a) by its odour (cautiously smell the vapour after removing the test-tube or small beaker from the flame) (b) by the formation of white fumes of ammonium chloride when a glass rod moistened with concentrated hydrochloric acid is held in the vapour (c) by its turning moistened red litmus paper blue or turmeric paper brown (d) by its ability to turn filter paper moistened with mercury(I) nitrate solution black (this is a very trustworthy test ) and (e) filter paper moistened with a solution of manganese(II) chloride and hydrogen peroxide gives a brown colour, due to the oxidation of manganese by the alkaline solution thus formed. 

Manganic sulfate, Mn2(S04)3, is obtained by the oxidation of manganese sulfate (tetrahydrate) in 6 M sulfuric acid by aqueous potassium permanganate at 0-25 °C. This oxidant oxidizes aromatic hydrocarbons to quinones [802]. 

The oxidation of manganese(ll) carbonate proceeds initially with air to a manganese(Ill,lV) oxide ... 

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