. Nature . t the sulphur in the white ironundoubtedly is the cause of the whiteness of the iron,whilst the excessively high silicon and low sulphur areequally responsible for the graphitic condition of the carbonin the grey irons. The micro-structure of the high silicon metal was charac-teristic of all phosphoretic, high-silicon, carbon plates of graphite cut the mass in many directions,whilst the binary eutectic of phosphorus and iron remainedin irregular patches, generally midway between the graphiteplates. The ground mass occupying the space between theeutectic and graphite pl
. Nature . t the sulphur in the white ironundoubtedly is the cause of the whiteness of the iron,whilst the excessively high silicon and low sulphur areequally responsible for the graphitic condition of the carbonin the grey irons. The micro-structure of the high silicon metal was charac-teristic of all phosphoretic, high-silicon, carbon plates of graphite cut the mass in many directions,whilst the binary eutectic of phosphorus and iron remainedin irregular patches, generally midway between the graphiteplates. The ground mass occupying the space between theeutectic and graphite plates consisted of silico-ferrite. The interesting feature about the structure of the whiteiron is that there was no iron-iron-carbide eutectic. Thishad been replaced by the ternary eutectic of iron-phosphorusand carbon, which, according to Dr. Wiist, containsabout :— Iron Phosphorus Carbon 91 There was evidence thatthe primary crystals of austeniteof the octohedral skeleton type had been the first to fall. out of solution, that the second crystal to form consisted ofshort plates of carbide of iron (cementite) ; whilst theternary eutectic of phosphorus, carbon, and iron was thelast to freeze and occupied spaces between the cementiteplates and the primary crystals. Dr. Carpenter and his assistant, Mr. Edwards, ofVictoria University, Manchester, kindly obtained, for thepurpose of this address, the cooling curves of these twotypical metals. These were as follows :— Grey long arrest at 1118° indicates a change of state, butis also coincident with important chemical changes. Thesecond long arrest at 945° is due to freezing of the ironphosphorus carbon eutectic. The arrest at 850° indicatesthe formation of pearlite, and corresponds closely with thearrest in a similar alloy examined by Gontermann. Thearrest at 690° is probably due to the formation of pearlite inthe eutectic of iron and phosphorus, and is of great interest,for it points to the conclusion that silicon is
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