. Nature . here the primaryaustenite crystallises with the silicon, as will be shownpresently. The second arrest is where the primary cementite platesfreeze. The third arrest, at 945°, is the freezing point of theternary eutectic, and is identical with that of the corre-sponding long arrest of the grey iron. The fourth arrest, at 77°, is coincident with the forma-tion of pearlite. Bearing in mind that the manganese in the white iron- was insufficient to combine with the whole of the sulphurpresent to form manganese sulphide, it is obvious thatsome other compound or compounds of sulphur
. Nature . here the primaryaustenite crystallises with the silicon, as will be shownpresently. The second arrest is where the primary cementite platesfreeze. The third arrest, at 945°, is the freezing point of theternary eutectic, and is identical with that of the corre-sponding long arrest of the grey iron. The fourth arrest, at 77°, is coincident with the forma-tion of pearlite. Bearing in mind that the manganese in the white iron- was insufficient to combine with the whole of the sulphurpresent to form manganese sulphide, it is obvious thatsome other compound or compounds of sulphur microscope clearly revealed the presence of mangancLiesulphide and traces of free iron sulphide. The carbide plates were quite free from striations ofsulphide, such as had been noticed by Mr. Levy in theeutectic of high sulphur irons. But for the sulphur present, the silicon would have beensufficient to effect a decomposition of the carbides, andthe metal in absence of the sulphur would have given a. I I.,- CkMUiri Wliile Iron White = massive plales of FejC, Dark —pearlite, the decomposed aust White and hall-tone=ternary Ke—C—P grey instead of a white fracture. In view of this con-clusion, it appeared to be probable that if manganese wereto be melted with the metal, it would combine with thesulphur associated with iron, &c., and crystallise as MnS,previous to the solidification of the carbide, or independ-ently, and that the metal would then become grey oncooling. In order to test this, a portion of the metal was meltedin a clay pot with a little pure manganese, free fromcarbon—suflicient to give i per cent, of manganese, whichwas more than sufficient to combine with the whole of thesulphur. As soon as the mass was melted it was at oncepoured into a sand mould and allowed to set. When<;old, it broke with a grey fracture corresponding to whatis known as hard forge, and the coinbined carbon, insteadof being about 3 per cent., was reduced to o-6 per cent.,a
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