. Nature . ilicon was concentrated in the pearlite; yetthis white iron, on heating to 1000° C, became quite -we not justified in concluding that it was the diffusionof silicide of iron from the silico-austenite into the carbideswliich caused the separation of graphite? As I had proved, first that sulphur crystallises withand makes the carbide of iron more stable, and secondthat in the presence of a fusible mother liquor rich inphosphorus, after the austenite crystallisation is complete,the carbide crystallises out in plates and not as iron carbideeutectic, it appeared probable that if
. Nature . ilicon was concentrated in the pearlite; yetthis white iron, on heating to 1000° C, became quite -we not justified in concluding that it was the diffusionof silicide of iron from the silico-austenite into the carbideswliich caused the separation of graphite? As I had proved, first that sulphur crystallises withand makes the carbide of iron more stable, and secondthat in the presence of a fusible mother liquor rich inphosphorus, after the austenite crystallisation is complete,the carbide crystallises out in plates and not as iron carbideeutectic, it appeared probable that if, as Gontermann pre-mised, two kinds of cementite actually form during thesolidification of iron-carbide-silicon alloys, it might bepossible to obtain them in a separate state by melting therich silicon alloys with a little sulphur. In order to test this, a portion of the No. i grey glazedmetal was melted, and when fluid a little sulphide of ironwas with it. Thf niixturt- \\,i~ ili- n 1 r-; il ~ Fig. 8.—Pure Iron-Iron Carbide Eutectic, the co .lingof which was arrested before the complete de-composition of the Carbides into Austenite and White=carbide of iron. Black lines = graphite. Half-tone = pearlite. Owing to the rapidity of the melting, some of the graphiteescaped and floated on the surface of the metal. When cold it was found that the lower part of thesmall casting gave a white fractured surface, whilst theupper part was close grey. The analvses were as follows :— Combined carbon Graphite Manganese Silicon Sulphur Phosphorus The grey part, although slowly attacked by cold acid,did dissoWe, yielding much voluminous silica. The whitepart w-as almost inert, and only dissolved in strong hydro-chloric acid with difficulty, and when the iron was dis-solved out the remaining silica was of the dense variety,from which it would appear that the effect of the sulphideIs akin to that of sudden quenching. White ... Grey paPer cent .. o6o trace ... ..
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Keywords: ., bookcentury1800, booksubjectnaturalhistory, booksubjectscience
