A college text-book of chemistry . contain nickel, and frequently small 622 COLLEGE CHEMISTRY. quantities of other elements, as manganese and of iron occur in enormous quantities, andwidely distributed in the earth. Among the more impor-tant are the following-named: hematite, Fe203; magnetite,Fe^; brown iron ore, Fe403(OH)6; siderite, or the car-bonate, FeC03; pyrite, FeS„; pyrrhotite, Fe7S8. It is alsocontained in many silicates, in small quantity, and in con-sequence of the disintegration of the constituents of rocksit is found in the soil, and in many natural waters. Inthe
A college text-book of chemistry . contain nickel, and frequently small 622 COLLEGE CHEMISTRY. quantities of other elements, as manganese and of iron occur in enormous quantities, andwidely distributed in the earth. Among the more impor-tant are the following-named: hematite, Fe203; magnetite,Fe^; brown iron ore, Fe403(OH)6; siderite, or the car-bonate, FeC03; pyrite, FeS„; pyrrhotite, Fe7S8. It is alsocontained in many silicates, in small quantity, and in con-sequence of the disintegration of the constituents of rocksit is found in the soil, and in many natural waters. Inthe vegetable kingdom it is always found in chlorophyll,and in the animal kingdom always in the blood. Thecompounds which are chiefly used for the purpose ofmaking iron, or the iron ores, are magnetite, Fe804;hematite, Fe203; brown iron ore, Fe403(OH)6; and spathiciron, or siderite, FeC03. Metallurgy.—The ores of iron, after they are brokenup, are first roasted, in order to drive off water from the^^^ hydroxides; to decompose car-. * bonates; to oxidize sulphides; and,as far as possible, to convert theWilis oxides into ferric oxide, Fe203,which is the most easily reducibleof the oxides of iron. After theores are prepared in this way theyare reduced by heating them withcarbon and fluxes in the blast-furnaces, when the iron collectsin the molten condition under theso-called slag at the bottom of thefurnace. Blast - furnaces differsomewhat in construction, but theessential parts are represented inFig. 78. The inner cavity of the furnaceis narrow at the top and bottom,as is shown in the figure. Throughpipes, known as tuyeres, such asthat represented at the lower part of the left-hand side of Fig. 78. IRON. 623 the figure, air is blown into the furnace to facilitate thecombustion. In modern furnaces arrangements are madeabove for carrying oft the gases and utilizing them as inner walls are built of fire-bricks, and these are sur-rounded by ordinary bricks, or stone-work. Th
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