Manganese dioxide concentrated sulphuric

Manganese dioxide and concentrated sulphuric acid if the solid chloride is mixed with an equal quantity of precipitated manganese dioxide, concentrated sulphuric acid added and the mixture gently warmed, chlorine is... 

In America bromine is obtained by treating the saline mother-liquors with dilute sulphuric add and then adding to the previously concentrated liquid, manganese dioxide and sulphuric acid. The mixture is then distilled, when the bromine passes over together with water and a little bromine chloride. 

This reaction is also used on a large scale, to obtain iodine from seaweed. The ash from burnt seaweed ( kelp ) is extracted with water, concentrated, and the salts other than iodides (sulphates and chlorides) crystallise out. The more soluble iodides remain and the liquor is mixed with sulphuric acid and manganese dioxide added the evolved iodine distils off and is condensed. 

When heated with concentrated sulphuric acid, manganese dioxide evolves oxygen, leaving a residue of manganese sulphate. The reaction takes place m two stages,3 namely ... 

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). 

Place a drop of the alkaline test solution in the distillation apparatus of Fig. 11.59 and evaporate to dryness. Add 5 drops concentrated sulphuric acid and 5 drops pure methanol, stopper the apparatus, and heat to 80°C in a water bath. Collect the methyl borate which distils over in a micro porcelain crucible, waxed on the inside, and containing about 1 ml reagent. A black precipitate forms. For very small amounts of borate it is best to add a few drops of benzidine acetate solution and thus to detect the traces of manganese dioxide by the... 

Experiment 122.—Mix and grind together in a mortar three or four crystals of potassium iodide and an equal quantity of manganese dioxide. Put the mixture in a 250 cc. Erlenmeyer flask, add about 8 cc. of water, and about 5 cc. of concentrated sulphuric acid, drop by drop. Invert a dry funnel upon the flask, as shown in Fig. 77, and stand the flask on a sand bath. Heat with a low, steady flame. Too much heat will vaporize the water, or crack the flask — perhaps both. The vapor of iodine will fill the flask, and crystals of iodine will collect on the sides of the funnel. Regulate the heat so that the flask is filled with vapor, but so that little or none escapes from the funnel. If vapor escapes from the funnel, plug the stem with cotton or soft paper. If crystals of iodine collect on the upper... 

Coccinin, Ci4Hi205 [80], is formed on melting carminic acid or carmine-red with potash. It forms yellow leaflets, insoluble in water, but soluble in alcohol and alkalies. The alkaline solution becomes oxidised on exposure to the air, the colour changing through - green to red. A solntion of coccinin in concentrated sulphuric acid gives a blue coloration on addition of manganese dioxide. 

Concentrated sulphuric acid decomposition of all solid oxalates occurs with the evolution of carbon monoxide (POISON) and carbon dioxide the latter can be detected by passing the escaping gases through lime water (distinction from formate) and the former by burning it at the mouth of the tube. With dilute sulphuric acid, there is no visible action in the presence of manganese dioxide, however, carbon dioxide is evolved. 

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