Reduction of Iron and Silver Ores. 217 



5. Means of remedying the defects of coldshort and hotshort irons. 



The characteristic property of coldshort iron can be given to any 

 soft iron, by exposing it for some time to heat. Its fracture be- 

 comes granular and laminated, but when the iron was originally good, 

 its softness and toughness may be restored by simply heating and 

 forging. 



Many of the bog and argillaceous Iron ores give coldshort iron, 

 notwithstanding the care of the workmen. The cause why iron is 

 in one case hotshort, and in another coldshort, is not yet fully under- 

 stood, but the hotshort iron is generally found to contain sulphur, and 

 the coldshort, phosphorus. Pyrites, in the ores, almost uniformly 

 make the iron hotshort, and copper, lead, and arsenic are thought to 

 produce the same effect. 



When the ores of iron do not make the metal hotshort or coldshort 

 in a very high degree, the defect may generally be remedied by careful- 

 fully roasting them, and then exposing them for some time to the weath- 

 er. In smelting the ores, a difference in the quality of the iron is often 

 effected by giving a different inclination to the tuyere (blast pipe.) 



Coldshort iron is generally brought to the state of soft iron, by vit- 

 rifying lime with the scoriae, and using this new cinder to cover the 

 iron in the finery furnace, or even by throwing a little lime upon the 

 mass of iron in the finery furnace, a short time before removing it 

 to pass between the rollers. Potassa, or ashes (of wood) will pro- 

 duce the same effect. 



Hotshort iron is more difficult to improve in quality, but where 

 coldshort iron is at hand, the difficulty may be remedied by mehing 

 together, in proportions to be determined by experiment, the differ- 

 ent kinds of cast iron that would produce the two sorts. The oppo- 

 site defects remedy each other. The same result is obtained by 

 mixing the ores that would make hotshort and coldshort irons, in 

 proper proportions, in the smelting furnace, when a cast iron is ob- 

 tained which may be made directly into good soft iron. 



There is another method, depending upon the, same principle, by 

 which the defect of coldshort iron may be removed. It is by using 

 bituminous coal with the charcoal in the process of refining, but if 

 too much of the coal be used, the iron becomes hotshort. Bitumin- 

 ous coal always contains some pyrites, and the sulphur contained in 

 these, is supposed to enter into combination with the phosphorus in 

 the coldshort, and thus both these substances become so volatile as 

 to escape from the melted iron. 



