Chemistry and Physics. 105 



and the less foreign substances (silicium, sulphur, phosphorus) it con- 

 tains, the greater amount of carbon will it require in order to become 

 much harder after the process of hardening than previous to it. 



Iron which contains 0*5 to 0*65 per cent, of carbon is very soft steel ; 

 the hardness and tenacity of the steel increase with the amount of the 

 carbon. From 1*4 to 1-5 per cent, appears to be the limit at which 

 steel exhibits after hardening the greatest hardness with the greatest 

 tenacity; with more carbon the hardness increases, but the malleabili- 

 ty and tenacity of the steel are diminished; when it amounts to 175 

 percent, the steel is very slightly malleable; with 1*9 it can scarcely 

 be welded red-hot, and with 2 per cent, it breaks to pieces under the 

 hammer. In this state the steel might already be called pig iron ; but 

 it may be beaten in the cold, and does not possess the property of sep- 

 arating a portion of its carbon in the form of graphite when allowed to 

 cool very slowly after fusion. This occurs only when the carbon 

 amounts to 2*25 or 2-3 per cent. If, therefore, a line of demarca- 

 tion were to be drawn between steel and pig iron, which should be 

 founded upon the combining proportions, 2*3 would characterize this 



The more carbon the pig iron takes up, from that minimum to the 

 maximum of 5*93 per cent., the lighter does the color become, and the 

 greater the hardness of the white variety, which is analogous to hard- 

 ened steel. The gray variety, with an equal amount of carbon, which 

 is analogous to unhardened steel, will be softer, that is, will separate the 

 more graphite on solidification, the slower the cooling. The gray pig 

 lf on, which contains the same amount of carbon as the corresponding 

 white kind, may consequently be sometimes a mixture of white pig 

 lr on with graphite, sometimes of soft steel or of hard bar iron and . 

 graphite, according as the solidification resulted more or less slowly, 

 a nd the solidified mixture retained more or less carbon in the combined 

 state. When the solidification is sudden, gray iron is scarcely formed, 

 because the entire amount of carbon remains chemically combined 

 w *th the iron, and is not separated as graphite. 



In preparing cast steel, the process is purely empirical, the eye of 

 the workmen being the weight and balance in determining the amount 

 of carbon in the material to be employed. To manufacture cast steel 

 *tth certain properties, those materials must be selected in which the 

 amount of carbon is known, and which, by being fused together in ac- 

 curately calculated proportions, produce a cast steel containing that 

 amount of carbon which corresponds with the properties required of 

 foe cast steel to be prepared. 



«• Note on the Action of a Solution of Caustic Soda upon a blone- 



Jjrc Jar; by Mr. Tmmum »——, v — — 

 «e author's attention was drawn to tnis subject from the presence of 

 a wge quantity of alumina in the analyses of some bronzes and iron 

 ores - On examining the reagents employed, it was found that it ongi- 

 natp -d in the soda, which had been kept for some time in a stoneware 

 J^ the alumina of which had been dissolved out by the soda, and a 

 lhlck coating of silica left closely adhering to its surface. 



S*co*d Series, Vol IV, No. 10 .—July, 1847. 14 





