Manganese dioxides hydrated

The reaction to produce the hydrated manganese dioxide has been studied by... 

According to C. J. B. Karsten,15 when small quantities of hydrated manganic dioxide are treated with nitric oxide in the presence of water, manganous nitrite, Mn(N02)2, is formed while with large quantities, manganous nitrate is formed. E. Mitscherlieh, and J. Lang showed that when an attempt is made to concentrate the soln., hydrolysis occurs, and hydrated manganese dioxide is precipitated. Neither ferrous nitrite nor ferric nitrite has been prepared but C. Przibylla... 

Cognate preparations, p-Chlorobenzoic acid. Proceed exactly as for o-chlorobenzoic acid. Use 1250 ml of water, 50 g (0.4 mol) of p-chlorotoluene (Expt 6.71) and 75 g, 37.5 g and 37.5 g (0.95 mol total) of potassium permanganate. When the oxidation is complete, steam distil the mixture to recover any unreacted p-chlorotoluene (3-4 g). Filter the reaction mixture from hydrated manganese dioxide and wash the precipitate with two 100 ml portions of water. Precipitate the p-chlorobenzoic acid in the filtrate (1) by the addition of 75 ml of concentrated hydrochloric acid. Filter the cold solution with suction, wash with cold water and dry in an oven at 100 °C. The yield of p-chlorobenzoic acid, m.p. 234-235 °C, is 55 g (89%). Recrystallisation from hot water raises the m.p. to 238-239 °C. 

Dilute solutions of potassium permanganate are reduced by finely divided platinum, potassium hydroxide and hydrated manganese dioxide being produced. Thus 3 ... 

The precipitate is insoluble in excess reagent. The precipitate rapidly oxidizes on exposure to air, becoming brown, when hydrated manganese dioxide, MnO(OH)2, is formed ... 

Hydrogen peroxide converts manganese(II) hydroxide rapidly into hydrated manganese dioxide ... 

Manganese (II) sulphate test If a bromate solution is treated with a little of a 1 1 mixture of saturated manganese(II) sulphate solution and m sulphuric acid, a transient red colouration (due to manganese(III) ions) is observed. Upon concentrating the solution rapidly, brown, hydrated manganese dioxide separates. The latter is insoluble in dilute sulphuric acid, but dissolves in a mixture of dilute sulphuric and oxalic acids (difference from chlorates and iodates, which neither give the colouration nor yield the brown precipitate). 

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