The object of the latter is to convert the manganous hydroxide by the atmospheric oxygen into manganese dioxide, but this would take place much too slowly if there was not an excess of lime present ready to combine with the manganese dioxide to form a calcium manganite.
The most striking phenomenon which they bring into prominence is the effect of any considerable quantity of manganese in annihilating the magnetic property of iron.
Manganese is found widely distributed in nature, being generally found to a greater or less extent associated with the carbonates and silicates of iron, calcium and magnesium, and also as the minerals braunite, hausmannite, psilomelane, manganite, manganese spar and hauerite.
Heusler that an alloy consisting of copper, aluminium and manganese (Heusler's alloy), possesses magnetic qualities comparable with those of iron.
If, on the other hand, the carbon-content is to be raised, then carbon and manganese are usually added together in the form of a manganiferous molten pig iron, called spiegeleisen, i.e.
Its exports include coffee, sugar, hides, cabinet woods, tobacco and cigars, tapioca, gold, diamonds, manganese and sundry small products.
Potassium permanganate in acid solution oxidizes it to carbon dioxide and water; the manganese sulphate formed has a catalytic accelerating effect on the decomposition.
The iron and manganese are precipitated as hydroxides, and are filtered off.
If the substance does not melt but changes colour, we may have present: zinc oxide - from white to yellow, becoming white on cooling; stannic oxide - white to yellowish brown, dirty white on cooling; lead oxide - from white or yellowish-red to brownish-red, yellow on cooling; bismuth oxide - from white or pale yellow to orange-yellow or reddish-brown, pale yellow on cooling; manganese oxide - from white or yellowish white to dark brown, remaining dark brown on cooling (if it changes on cooling to a bright reddishbrown, it indicates cadmium oxide); copper oxide - from bright blue or green to black; ferrous oxide - from greyish-white to black; ferric oxide - from brownish-red to black, brownish-red on cooling; potassium chromate - yellow to dark orange, fusing at a red heat.
By evaporating a solution containing free sulphuric acid in a vacuum, the hepta-hydrated salt first separates, then the penta-, and then a tetra-hydrate, FeSO44H2O, isomorphous with manganese sulphate.