. Inorganic chemistry . it to insinuate itself into the finest Metallic Elements. 265 lines, and so to present a faithful copy of each. This fact is notto be confounded with another, which has led to its beingdenied—namely, that an iron casting is always smaller thanthe wooden fac-simile, or original, from which its mould wasmade. This diminution of size is owing to the contractionof the iron after it has consolidated. It has swelled up intoevery crevice of the mould, however, before contraction com-mences. 919. Malleable iron is prepared in this country from cast-iron by depriving the latter
. Inorganic chemistry . it to insinuate itself into the finest Metallic Elements. 265 lines, and so to present a faithful copy of each. This fact is notto be confounded with another, which has led to its beingdenied—namely, that an iron casting is always smaller thanthe wooden fac-simile, or original, from which its mould wasmade. This diminution of size is owing to the contractionof the iron after it has consolidated. It has swelled up intoevery crevice of the mould, however, before contraction com-mences. 919. Malleable iron is prepared in this country from cast-iron by depriving the latter of carbon. The process by whichthis is done is called puddling. This is effected in a reverbera-tory furnace (see fig. 59)—that is, one somewhat resembling abakers oven, where the current of burning gases proceedingfrom the hot fuel, A, is reflected or made to reverberate down-wards from the arched roof of the furnace to the floor, B, so asto expose a body lying on the latter to a great sheet of flameand of hot Fig- 59- 920. The cast-iron is laid in the bed of the furnace, B, whereit speedily melts^ and becomes partially oxidised at the workman then, by means of a long iron rod, or large oar-like spatula, puddles the melted metal—that is, stirs it up, soas to bring each portion of it successively to the surface. Theobject of the whole process is to remove the impurities from thecast-iron. The silicop and phosphorus are oxidised and removedin the slag or scum, whilst the carbon is converted into carbonic 266 Chemistry. oxide, and as the removal of the carbon proceeds, jets of thatgas are seen burning on the surface of the metal with itscharacteristic blue flame. 921. One marked effect of the withdrawal of the carbon fromthe cast-iron is the diminution of its fusibility, so that althoughthe temperature of the furnace remains unaltered, the metalceases to be liquid, and becomes first pasty, and then, as thestirring or puddling is continued, granular—that
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