Cast Iron, Steel, mid Malleable Iron. 581 



skeleton grains will attract each other and become united. 

 The attractive forces of these grains for carbon are developed 

 only when they are at a white heat, and it is an error, which 

 has remained even in the last edition of Turner's Chemistry, 

 that iron will weld at a red heat. When the grains of iron 

 at a white heat really come into contact with carbon, or when 

 a sufficient quantity of carbon has not been burnt away 

 during the process of puddling, the skeleton grains, instead 

 of adhering to each other, come into a state of fusion during 

 the compressing force of the strokes of the hammer, assume 

 a crystallized form, and produce a sort of cold-short iron. 



Chemically-pure iron I could never make to weld. I pro- 

 cured chemically-pure iron by reducing oxide of iron (from 

 which all traces of silica were carefully separated by means 

 of repeated solutions and evaporations) in a current of hydro- 

 gen, and inclosed it hermetically in a platinum tube pre- 

 viously filled with dried hydrogen. Several of these tubes 

 were exposed to different degrees of heat, from the dark red- 

 heat to the white-heat, and hammered, in order to give con- 

 sistency to the inclosed powder of iron ; but it never showed 

 any signs of continuity or welding afterwards, and under the 

 microscope itself appeared unaltered. 



We have just shown, that silicon principally imparts to the 

 iron the property of welding ; but we see likewise in the last 

 specimen of iron examined, that even a considerable quantity 

 of carbon contained in the iron does not impart to it the pro- 

 perty of hardening after being heated and cooled in water. 

 Besides this last specimen of iron, I melted pure iron with 3 per 

 cent, of charcoal prepared from sugar, in a clay crucible, and, 

 watching the heat very carefully until it had become quite 

 liquid, I poured it into a common ingot mould for cast steel. 

 This iron when broken presented a large round granulation 

 of a bluish-white colour, resembling the specimen c before 

 mentioned; under the hammer it forged extremel}' soft and 

 tough, like Taberg iron, but would not harden at all when 

 dipped red-hot into water, notwithstanding it contained 2'5 

 per cent, of carbon. But it contained scarcely any traces of 

 silicon ; and I found by keeping the liquid mixture for a 

 longer time at a higher degree of heat, the silicon increased, 

 and with it the proj)erty of hardening. 



We have mentioned in a former paragraph, that iron when 

 heated in a reverberating-furnace in contact with siliceous 

 matter, imbibes a portion of silicon ; but the question now is, 

 why the specimen e", before-mentioned, did not imbibe silicon 

 from the bottom of the furnace, but combined instead with 

 the carbon of the ^decomposed flame ? The answer is ob- 

 vious. In the cast iron from which the specimen e was pre- 



