214 On the Principles Involved in the 



sulphates, and these are removed by throwing the ore into a stream 

 of water, or by leaving it, some lime, exposed to the weather. Some 

 iron ores are in a proper state for smelting, immediately after the 

 roasting process ; some require long exposure to the weather, and 

 others to be quenched in water, while still hot. Many ores that with 

 the above treatment, make iron of the best quality, would, without 

 preparation, make iron of little value. It may be laid down as a 

 general rule, that iron ores are more easily smelted, and make a purer 

 and better iron, by being long exposed to the action of the weather. 



2. Fluxes. 



Fluxes are substances added to the ores to facilitate their fusion, 

 and to separate the impurities. There is another all important object 

 in having a proper flux for the iron ores, and it is one which is gen- 

 erally overlooked. 



It is, to form a coating of glass over the melted globules of iron, 

 as they fall in their passage by the tuyere, (blast pipe,) to the cru- 

 cible of the furnace. If they be not coated, so as to protect them 

 from the air, that rushes through the blast pipe, they take fire as they 

 pass by it, and are again oxidized. Hence, it is not only necessary 

 to have a flux, but to have one of such a degree of fusibility, as shall 

 fulfil the conditions required. It should not be very easily fused, 

 else, 



1. It would melt before the metal, and run through the furnace 

 without coating the iron. 



2. The melted flux would dissolve the ore which was not then 

 deoxidized, and thus create a great loss. 



3. Any iron that might be reduced and fused, would pass naJced 

 before the blast and be reoxidized. 



4. The flux would exert a powerful solvent action upon the boshes 

 and crucible of the furnace, so as soon to wear it out. 



Again, the flux should not be very difficult of fusion, else, 



1. The iron would be fused first, and pass naked before the blast, 

 and thus be reoxidized and then dissolved by the glass or cinder in 

 the crucible of the furnace. 



2. The flux, when melted, would form a tenacious mass, in the 

 crucible, through which the globules of melted iron could not sink. 



3. It would clog and choke the furnace so as to stop its operation, 

 in a short time, unless remedied. 



