flAMII/rON SCIRNTIFIC ASSOCIATION 51 



Calculated Analysis of Charge. Actual Analysis of White Iron. 



Silicon 1.31 Silicon 98 



Sulphur 048 Sulphur 053 



Phosphorus 155 Phosphorus 157 



Manganese .44 Manganese ,25 



Total Carbon 3.20 Total Carbon 2.45 



A comparison of the percentage of the various elements 

 in the original charge with the percentage of those elements 

 in the product of the melt will serve to illustrate the changes 

 that take place in the composition of the metal during the 

 course of the melt. Silicon, Manganese and Carbon are very 

 considerably reduced. Sulphur is somewhat increased, while 

 Phosphorus remains practically constant. The extent of the 

 reduction of Silicon and Carbon is dependent upon the 

 regulation of the flame and the duration of the melt, and it is 

 most important that the reduction shall not proceed too far. 

 If the proper precautions are not taken, the carbon, the per- 

 centage of which greatly influences the melting point of the 

 metal, will be reduced to such an extent that the heat of the 

 air furnaces will not be high enough to maintain it in a 

 sufficiently fluid condition to pour into molds. Moreover, an 

 iron with too low a carbon content cannot be successfully an- 

 nealed, and will remain in too brittle a condition for 

 satisfactory use. The lower limit of the carbon for success- 

 ful results has been variously stated, an eminent American 

 authority placing it as high as 2.75%, but it has been the ex- 

 perience of the writer that it may run as low as 2.10% with- 

 out serious injury to the product. 



At the termination of the melt, which ordinarily requires 

 from tliree to four hours, the metal has been sufficiently re- 

 fined by the action of the flame to have its carbon almost 

 entirely in the combined condition after it has cooled in the 

 mold. By this is meant that the carbon is united chemically 

 with the iron and cannot be detected in the fracture as it may 

 in the case of gray iron whose dark color is due to carbon 

 separated from the iron and existing in the form of graphite. 

 The fracture of the air furnace iron is markedly crystalline, 

 and is technically known as "white" in distinction to the 



